How does the existence of a Greenhouse Gas Effect (GHE) in the atmosphere affect the tropospheric lapse rate? I am restricting my consideration, for the moment, to just the troposphere. With regard to our understanding of the GHE do we predict that an increased GHE due to increasing CO2/Water/Methane will change the lapse rate postively or negatively? The dry adiabatic lapse rate (DALR), according to my old text books, is easily calculated from the formulae -g/c, where g is the acceleration due to gravity and c is the specific heat capacity of the atmosphere. This is supposed to be a general formulae that can be applied to any planet with a solid surface and a gaseous atmosphere. So for earth is the formulae now -g/c + (GHE) or is it -g/c - (GHE)? The bracketed GHE term being specific to the atmosphere of a specific composition, e.g. including 400ppm CO2.
The second part of the question then , after we have the correct sign, is how is the term (GHE) expected to vary as the CO2 (or other greenhouse gas) concentrations vary?

For dry adiabatic, you simply ignore the greenhouse gas.   This might sound like a cheat, but it's not.   The dry adiabatic lapse rate doesn't change with temperature or latitude.

For a physical explanation, if you consider what the greenhouse gas does, it captures heat and raises the temperature near the Earth's surface, which expands the troposphere and raises the tropopause.   In other words, the troposphere grows taller, so the lapse rate can remain the same and the tropopause moves a little higher up.   This can also be seen in higher and lower latitudes on Earth in that the tropopause is about 5 miles closer to the Earth at the poles than over the equator.

The adiabatic lapse rate is a property of the ideal gas law.  Heat trapping greenhouse gas doesn't affect it because the gas expands accordingly with trapped heat.

The true environmental lapse rate is a bit more complicated as that fluctuates with humidity.   As the Earth warms, absolute humidity should increase but relative humidity should slightly decrease.   A lower relative humidity, on average, should raise the lapse rate slightly (I think), as the dry adiabatic rate is greater than the moist rate.    But this last paragraph take with a grain of salt.   The environmental lapse rate is more complicated.

  2 identical planets, with 2 identically thick atmospheres, same c,
  same g, same lapse rate but one is a pure CO2 atmosphere and the other
  is a non greenhouse gas with the same c (fictional gas, we will call
  it CO2U)

I'm not an expert in lapse rate, so my answer is a little bit of a cheat, but I'll take the thought experiment as best I can.

Fictional gas - same density as CO2 (at standard temperature & Pressure "STP").   Both atmospheres are on planets of identical surface area, with identical gravity and both atmospheres have identical mass and (just to clarify) Identical density at STP.

The atmosphere that traps heat will expand, so it will have a higher troposphere.   Hot gas expands.   Cold gas contracts.

So the planet without the greenhouse gas will have a troposphere that's 6 miles high, the one with the greenhouse gas and a higher surface temperature will have a troposphere 10 miles high.   The rate of temperature drop can remain consistent at (-g/c) but the hotter planet will have a higher troposphere and a more expanded atmosphere.   That's for the theoretical model anyway.   I don't do real world models.  Those are much harder.

  So the planet with the GHE atmosphere will be hotter at the surface,
  hotter at any given height in the atmosphere and hotter as a complete
  body/system (atmosphere+solid planet). Everything is hotter. Errr...
  what happened to the supposed radiative S-B balance as viewed from
  space then ?? Radiative input from sun the same, radiative output from
  the GHE planet now higher

The energy balance question is a fun one, especially when climate change "skeptics" use it to say "climate change can't possibly be right" - look at the chart they use, more heat leaves the Earth's surface than comes from the sun.

Source.

Lets ignore that debate for brevity and look at the overall theory of increasing greenhouse gas driven climate change.   The Energy from the sun is same, so, why does Earth get warmer?  The answer is trapped heat.   So, what does this look like from space?   Counter intuitively, from space the Earth looks colder than it did 30/40/50 years ago.  It's giving less thermal radiation into space.   This is because heat is being trapped in the lower atmosphere and oceans.  The upper atmosphere on Earth is actually cooling and contracting and less thermal radiation is leaving the Earth, not more, even with the warming surface temperature.  Measuring the decrease in heat that leaves the Earth is one way to measure the total amount of heat being trapped by climate change.

In time, a new equilibrium will eventually be reached and heat in will equal heat out again but for now on Earth, Heat in is greater than heat out.  The difference is heat added, which does things like warm the air, the oceans and melts the ice.   In your scenario, there's no change, it's already warmer, but it's warmer in equilibrium, so heat in = heat out.

In other words:  A warmer atmosphere at equal heights doesn't mean more heat leaves the planet, because the CO2 rich atmosphere makes it harder for the thermal radiation from the warm surface to reach space.   The greater heat is balanced out by a greater percentage being reflected back to the surface.   The amount that goes into space is equal on the 2 planets.


What does geochemical data tell us about Earth's earliest palaeoclimatic conditions? Given that the age of the oldest zircon samples are about 4.4 billion years old, and meteorites and other extraterrestrial samples can also give us some indication about the Earth's composition into the Hadean era (source: Zircon Chronology: Dating the Oldest Material on Earth.

Many resources refer to the earliest atmosphere as being (for example):

  As a result of the high temperatures at the center of the Earth, and due to volcanic activity, the crust emitted halogen gasses, ammonia, hydrogen, carbon dioxide, methane, water vapor, and other gasses. In the following 100 million years, these gasses accumulated to form the primordial atmosphere.  This atmosphere was quite similar to the atmosphere of Titan, one of the larger moons of Saturn.  The primordial atmosphere is believed to have reached a pressure of 250 atmospheres and would have been extremely toxic to life as we now know it

Source: The Hadean Eon

Many mechanisms are suggested in this and many other resources, from impacts to volcanic outgassing etc. But what does measured geochemical data tell us about the Earth's earliest palaeoclimatic conditions?

This question is related to the previous questions:

What, if any, paleoclimate data can be derived from igneous rocks?
What, if any, paleoclimate data can be derived from stromatolite fossils?

But, this question is looking at the earliest palaeoclimatic conditions of the Earth.

The first thing to note here is that the zircons you mention in your question are the only thing we have dating from the Hadean: no known Hadean continental or oceanic crust have been found to date. So, all informations come from these zircons.

What do they tell us?

The rare earth element (REE) composition of these zircons (and in particular the zoning of said REE inside the mineral) suggests that they formed in a magma derived from the melting of a continental crust (Wilde et al. 2001). Their high $\delta^{18}\mathrm{O}$ composition also indicates that the magma was at some point in contact with liquid water (also Wilde et al. 2001): both continents and oceans were present in the Hadean. The presence of liquid water already implies cooler temperature than what was previously thought (Valley et al. 2002).

With regards to climate per say, the Lithium composition (high concentration, light isotopes) of the zircons (Ushikobo et al. 2008) have been interpreted as evidence of an intense chemical continental weathering. This weathering could have several explanations but one possibility retained by Ushikobo et al. 2008 (see also Sleep 2010) is a CO2-rich atmosphere with surface temperatures above 50°C.

Sleep, 2010. The Hadean-Archaean Environment. Cold Spring Harbor Perspectives in Biology, 2: a002527.
Ushikobo, Kita, Cavosie, Wilde, Rudnick & Valley, 2008. Lithium in Jack Hills zircons: Evidence for extensive weathering of Earth's earliest crust. Earth and Planetary Science Letters, 272: 666-676.
Valley, Peck, King & Wilde, 2002. A cool early Earth. Geology, 30: 351-354.
Wilde, Valley, Peck & Graham, 2001. Evidence from detrital zircons for the
existence of continental crust and oceans on the Earth 4.4 Gyr ago. Nature, 409: 175-178.


How long did it take for Earth's magnetic field to first appear? Merely what the title states. My knowledge of geography/geology/*logy is limited to high-school, and some snippets, and snatches of conversation.

As I understand Earth's magnetic field is attributed to the bi-layered nature of it's core. Proto-Earth probably did not have a magnetic field. Apparently much later Earth's core cooled enough to separate into two layers - causing the field to appear

How long did it take for Earth's magnetic field to first appear?
As a corollary, did water appear first on Earth, OR did the magnetic field appear first?

The age of the Earth's magnetic field could be as old as the existence of the physical conditions capable of generating a magnetic field. Because we believe the geomagnetic field originates from the liquid outer core, your question could be restated as: When did the Earth form a liquid core?

How the Earth's core formed is still not well understood and the area of research is referred to as planetary differentiation.


What tectonic structures delineate the split between the Australian and Indian tectonic plates? Growing up, when looking in textbooks and other references about plate tectonics, there was always the Indo-Australian (or Indian-Australian) plate, such as shown below:

Image source: The Geologic Story of Yosemite National Park (1987) by N. King Huber

But, recently it has been recognised that there are separate Indian and Australian plates, such as shown below:

Image source: An Introduction to
Plate Tectonics

This would make sense given the differences in the collisional history of the two landmasses.

What tectonic structures delineate the split between the Australian and Indian tectonic plates?

The structures are not mature or well defined and deformation was thought to be diffused, i.e., distributed over a large area. Earthquakes such as the M8.6 2012 Indian Ocean earthquake (largest strike-slip earthquake on record) appear to accommodate some, if not all, of the deformation.

Seafloor geodesy is relatively a new field. Most studies are limited to areas near the coast, e.g., US (Cascadia), Japan etc.


How to find rocks worth tumbling? My son recently got a rock tumbler and I was wondering if anybody knows of any resources that would show pictures of the different types of rocks as they would be found on the ground. I live in Chino Hills CA and we have many trails. I wanted to be able to tell the difference between something worth tumbling and something that isn't.

Any stone quartz rich and smooth not porous (no visible holes) like agates, quartzite or cherts are you best bet for getting a nice tumbled stone.

A great book is:

Gems and Minerals of America: A Guide to Rock Collecting (1st Edition)
by Jay Ellis Ransom
Hardcover, 705 Pages, Published 1975

ISBN-10: 0-06-013512-3        / 0060135123
ISBN-13: 978-0-06-013512-6 / 9780060135126

Your local library might have a copy of it.
See to find on sale on Internet also: used ~$5.00

http://www.gettextbooks.com/isbn/9780060135126

BTW, tumbling stones and rock collecting led me to a career as a geologist.


How are Richter magnitudes of past earthquakes estimated? In reading about historical major earthquakes, in particular, the Great Shaanxi Earthquake that killed approximately 830,000 people in July, 1556, there is a claim made about the approximate Richter scale magnitude:

  Later scientific investigation revealed that the magnitude of the quake was approximately 8.0 to 8.3

despite this earthquake obviously pre-dating the development of the Richter Scale.

What do geologists look for to estimate the magnitude of past major earthquakes?

The approximate magnitude of ancient historic earthquakes may be estimated using a Magnitude/Intensity comparison based on modern earthquakes.  Earthquake intensity may be estimated from the descriptions written down by people. The Chinese officials made detailed records of the damage caused by large earthquakes.


What keeps the different gases mixed in the atmosphere? Consider a gas centrifuge holding two different gases. After spinning for a while, the heavier gas will move to the outside, and the lighter gas will be on the inside. In other words, we have stratified the gases.

Why hasn't this happened in Earth's atmosphere for N$_2$ and O$_2$?

Note: I'm not considering Earth a centrifuge because it's rotating. I'm comparing it to a centrifuge because there's a weight (gravity) on the gases. In this case, the oxygen should settle to the bottom, and the nitrogen above it.

It's because gases also diffuse. If you separate two gases of different densities by a horizontal membrane, and then slowly remove the membrane, then the interface will diffuse. You can try this with bromine and air, for example – the bromine will stay at the bottom (easily visible because it's brown) and the air will stay at the top, but the interface will be diffuse. The bromine will largely stay at the bottom because it's significantly heavier than the air, but the diffusive mixing will be much stronger if the density difference is smaller – as is the case with nitrogen and oxygen, which are of course not very different in density.

While the effect above just considers mixing due to molecular diffusion, the atmosphere of course also vigorously convects due to the effects of thermal heating (and humidity differences). Both also turn over the atmosphere and mix it.

That said, the composition of the atmosphere does change with altitude. See, for example, here. The thing is that the thickness of layer corresponding to the blurry interface between bromine and air is about as thick as the entire atmosphere, and therefore hard to distinguish from other effects (such as ionization) that change its composition with altitude.


Is the Arctic already ice-free during summer? Not an expert in this field but I'm just curious as to how accurate the Google Map is here

Also, from the interview with scientist Peter Wadhams, his estimate seems to be spot-on.

I still remember, as a kid, we used to draw a white landmass when illustrating the Polar North. Now, I think we'll have to teach the kids to draw wavy lines, representing the Arctic Ocean instead!

You can follow the sea ice extent here at http://polarportal.dk/en/sea-ice-and-icebergs/

And here at http://nsidc.org/arcticseaicenews/

There is a lot of things you can not see in regular maps as they fill in the area with ice as open sea on their products,It is the same for land areas too they do not change the maps if the ground is covered by snow.

So the answer to your question,There is still an ice cover in the arctic even if it is starting to get dangerously low at the end of summer.

As a side note it does look like the arctic ice cover is melting a lot faster this year than what it have done the last ten years on average,You can see a more detailed and year by year graph here https://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/ for both arctic and antarctic sea ice


Can large earthquakes happen few times at same place(in days) I want to know if large earthquakes can happen twice in the same place? I live in Istanbul/Turkey. In Canakkale/Turkey too many earthquakes happen for days! I know it is normal for this region but 4.8 , 4.9 , 5.0 , 5.3 etc. is this a normal thing? I'm not saying "months", every day atleast one earthquake...(In Richter Scale)

Is this OK? or not?

Yes, and they are quite common, they are called aftershocks.

An earthquake redistributes the stress that creates the quake across the fault line, which then creates new points of stress, which result in additional earthquakes, which further redistribute the stress again, and so on and so forth until all the energy is spent.

Earthquake swarms also exist.  They basically work on the same principle as aftershocks but are much stronger. They tend to occur in places where you have many faults in the same region.  The release of pressure on one fault causes movement that puts more stress on other faults, causing a cascade of quakes. California and other transform faults are famous for them. Here is rather nice BBC film about them.  http://www.dailymotion.com/video/x2262rz_bbc-horizon-2003-earthquake-storms_shortfilms.


What tools are available to build unstructured grids for ocean models? Generating finite element/volume grids is tricky, especially when you are dealing with complex coastlines. What are the more common tools to create the grids and to check the quality (e.g., minimum angles, wave propagation constraints) of it?

The simplest is triangle http://www.cs.cmu.edu/~quake/triangle.html which is providing lib form many other more advanced packages. You can create poly file and create "holes/islands" in grid etc. Easy to make simple grids.
Another more advanced / gui is xmgredit where you can create/modify grids.
Blue kenue  etc..
use the force luke, do a google and it will popup many other packages,
I just wrote a few which are free and for 2D ocean applications.


Depth of the wind-induced currents and the shoreline In the open sea the speed of the current in the developed sea can be estimated as 3% the wind velocity at 10 meters.

Why is ocean surface velocity around 3% of wind velocity?

Is there a similar estimation for the depth of such a current?

Intuitively, a surface current can't continue to move towards the shoreline, as there is not enough space underneath for a bottom current to compensate the surface current, and those currents would interfere. Also, there should be some mixing of the water layer in the breaking waves near the shore, that would contribute to canceling the surface current too.

Having a wind-induced surface current directed towards the shoreline, how close to the shore can such current continue, depending on the steepness of the seabed, the wind and the wave conditions?

First, a bit of background, following the Navier-Stokes equations and assuming steady state conditions, we can obtain a simplified balance known as Ekman balance for the boundary layer of the upper ocean (order hundred meters). In this part of the ocean horizontal gradients are small compared to vertical gradients. Under these conditions, there is a balance between Coriolis, and friction (sometimes the pressure gradient force needs to also be considered in the balance).

The resulting theoretical flow has a vertical structure with decreasing magnitude with depth and flow direction progressively rotating to the right (left in the southern hemisphere) as depth is increasing. This is known as the Ekman spiral.
 Source: http://offshoreengineering.com

Under these conditions, in the open ocean (in fact assuming an infinitely deep ocean), the transport in the Ekman layer is perpendicular to the wind direction. The depth of the Ekman layer, or Ekman depth, is simply dependent on Coriolis and viscosity: $$D_e = \sqrt{2K_m\over f}$$ where $K_m$ is the kinematic turbulent viscosity (assumed constant) and $f$ is the Coriolis parameter (a typical value for mid-latitudes is $10^{-4}$ $s^{-1}$). Typical Ekman depths are of order 10 to 30 meters. Typical values for $K_m$ are around $0.1$ $m^2/s$ (not to be confused with molecular viscosity that is around $10^{-6}$ $m^2/s$) but can vary by several orders of magnitude, resulting in a range of $D_e$ of $10-150m$. A good explanation of Ekman balance and much more information can be found in Cushman-Roisin & Beckers (Chapter 8).

While all that is useful in a theoretical setting, the depths obtained from observations of the Ekman depth can be approximated by the expression: $$D_e = 0.4\sqrt{\tau\over f^2 \rho_0 }$$ where $\tau$ is the wind stress magnitude and $\rho_0$ is water density. The factor $0.4$ has been derived empirically and can varied slightly under different oceanic conditions.

All that was describing the surface boundary layer, but in reality a bottom boundary layer also forms. The solution to the bottom layer can also be approximated as an Ekman layer for which the forcing is not the wind, but the bottom friction. The resulting boundary layer also has an Ekman depth approximated with the expression above. In an sloping bottom, the boundary layer follows the bottom slope and the thickness (depth above bottom) of the layer (measured perpendicular to the bottom) is scaled by the cosine of the bottom slope.

Taking 10 meters (one of the smallest values in mid-latitudes) for the surface and bottom boundary layer thicknesses, that implies that in water depths shallower than 20 m the two boundary layers overlap. In water depths shallower than that, the transport in the surface layer is no longer perpendicular to the wind direction. The momentum input into the water by the wind (wind stress) is affected by the presence of the bottom and it is directly dissipated by bottom friction. The mixing by the wind (and wave breaking near the surf zone) results in additional mixing through the water column and facilitating well-mixed water columns. Under these conditions the wind-induced currents extend all the way to the bottom with the direction of the flow being a function of bottom depth, wind direction, and bottom slope. The presence of wind-induced currents does not preclude the occurrence of flow in the opposite direction of the wind.

A fantastic article summarizing the different flow conditions under different wind and wave fields in shallow water depths is given in Lentz and Fewings (2012). (Reprint)

Additional factors to consider are:

stratification by temperature and salinity that reduces mixing and helps maintain a separation between surface and bottom layers (some effects described here).
what happens when the wind is changing speed and direction (non-steady state)?
what happens at the Equator where the Coriolis parameter is zero?


Why is the mass of atmosphere of Venus so much greater than that of the Earth? Earth and Venus have a very similar gravity, but the mass of atmosphere on Venus is much greater (according to this wikipedia article 93 times larger). I know that the chemical composition and temperature are different, but there is just a lot more matter in the Venusian atmosphere. Why is this?

It is thought that about 4 billion years ago, Venus had an atmosphere and oceans similar to Earth's. Owing to it's proximity to the sun and the fact that most of its primeval atmosphere was carbon dioxide, it heated up and the oceans evaporated away, causing more greenhouse heating as they did so. Water vapour is a potent greenhouse gas.

Earth's primeval atmosphere was also mainly CO2, but being about 30 million miles further away from the sun it did not experience the runaway greenhouse effect which overheated Venus. The seas did not evaporate into the atmosphere, as they did on Venus, where the water mixed with sulphur dioxide/trioxide to create clouds of sulphuric acid droplets.

Another thing which has thinned the Earth's atmosphere is billions of years of sequestration by living things, which have transformed atmospheric CO2 into limestone (CaCO3), other carbonates, and various forms of fossil hydrocarbons (Lange et al., 1983). The photosynthetic organisms which produced the hydrocarbons also produced huge quantities of oxygen, which today makes up 21 percent of our atmosphere.

If you could magically turn all the carbon sequestered away in the rocks back into CO2, and evaporate our oceans so that they went up into the atmosphere, the Earth would be much more like Venus, including the runaway greenhouse effect which has heated Venus's lower atmosphere to 460C. Being much further away from the sun than Venus, Earth would not heat up as much as that, but it would still be too hot for life.

Mars also had an atmosphere similar to Earth's and Venus's, but because of its much weaker gravitational field has been unable to hang onto them. However, the proportions of the gases in the Martian atmosphere are still similar to those on Venus, though far more tenuous.

Lange, M. A. & Ahrens, T. J.(1983):"Shock-Induced CO2-PRODUCTION from Carbonates and a PROTO-CO2-ATMOSPHERE on the Earth", LUNAR AND PLANETARY SCIENCE XIV, P. 419-420.
http://adsabs.harvard.edu/full/1983LPI....14..419L


Light at the coast - is it different? I have heard artists talk about the unique quality of light near the sea, and now I live near the coast I want to know if there's any truth in it. Does being near the ocean affect light inland?

I'm in the UK, where it's not usually  clear blue skies; it's cloudy or partially cloudy (clouds may have an effect?).

I've lived in a flattish region in the centre of the UK, and at the coast. I think it's brighter here, but I can't figure out if it's a real difference. And Google is silent.

I've come up with possible explanations:

It's purely psychological
It's a side-effect of the big horizons making places feel lighter because more sky is visible
Sunlight reflects off the sea, and the clouds scatter it back onto the land

Is this real? If so, what's the mechanism and how far inland does the light penetrate?

At the coast the horizon facing the ocean is unobstructed, so a larger part of the sky is visible than inland, where trees, buildings, etc., block the view of the horizon. Also, the horizon sky is brighter than the overhead sky. At or near the horizon the sky appears lighter blue than at the zenith, or even whitish. Looking vertically at the zenith is looking through one air mass; looking horizontally at the horizon is looking through 40 air masses. Although the atmosphere scatters short wavelengths at the violet end of the spectrum most effectively, 40 air masses scatters enough of even the longer red wavelengths that the horizon sky appears very light blue or even whitish. 40 air masses is enough to scatter all of the light. Greater scattering of light causes the near-horizon sky to be brighter. (Even the zenith sky appears blue rather than violet because the Sun emits more blue light than violet and the eye is more sensitive to blue light than violet.)


What was the Amazon like during Green Sahara? It is said that the Amazon rainforest receives up to half of its nutrients via mineral dust from the Sahara desert. But a few thousand years ago, the Sahara desert was much more fertile, having a savannah-like environment.

Did this mean that the nutrient transfer to the Amazon did not take place during this time? If so, what did the Amazon look like?

According to the article Africa: Greening of the Sahara (Claussen et al.), the 'Green Sahara, occurred during the Holocene climatic optimum, occurring at the same time as the  "African Humid Period", also similar ages to the events mentioned in your 3rd link.  All occurring during the mid Holocene

At the same time in the Amazon region, according to the article Responses of Amazonian ecosystems to climatic
and atmospheric carbon dioxide changes since the
last glacial maximum (Mayle et al. 2004), was

  reduced precipitation in the Early–Mid-Holocene (ca. 8000–3600 years ago) caused widespread,
  frequent fires in seasonal southern Amazonia, causing increased abundance of drought-tolerant dry forest
  taxa and savannahs in ecotonal areas.

Although, this effect was not uniform over the entire Amazonian Basin, the authors conclude from pollen, charcoal and other samples, that the Amazon Basin had far less precipitation (up to 40 less in places), which caused

  increased fires and consequently greater ecosystem
  disturbance, which would be expected to have caused
  structural as well as compositional changes to plant communities,
  such as expansion of drought-tolerant lianas and
  semi-deciduous taxa within forests and expansion of savannahs
  at forest–savannah ecotones. Populations of coldadapted
  species (e.g. Podocarpus) were largely eliminated
  from the Amazon lowlands during this interval, and cloud
  forests on the eastern flanks of the Bolivian Andes diminished
  while open, grass-dominated ecosystems expanded.


Measuring bed dip angle from contour lines, which lines to pick? Measuring dip angle of a bed, I choose any 2 contour lines that cross the bed, and then project  lines off and measure the angle (I'm assuming this is standard technique that doesn't require explanation)

But it seems (at least with my real world map) that the dip angles vary greatly depending on the contours I pick, so how should I choose which contours to pick?

You are correct by saying that the dip angles vary greatly depending on the contours that you pick. In contrast to artificial maps designed to teach basic structural geology to students (such as the one you added in your question), natural maps are rarely "nice and friendly" regarding dip calculation.

There are several reasons for this:

The dip angle may actually vary. In artificial maps, the beds are usually tabular and not folded (unless this is a folding exercise). Natural rocks are rarely exactly planar and tabular, and their thickness also varies. This can result in different dips for the top and the bottom of the bed at the same location.
Maps are not usually drawn with dip calculations in mind. The contacts are based on the limited exposures available to the mapping geologist. The contacts between rock units may be obscured by vegetation, talus, soil and even houses and roads. Making a map that is dip-calculation friendly is time consuming, if possible at all.
It also depends on the accuracy of the topographic contours. As you probably know, you have to take the elevation into account in these calculations. Even if the contours are accurate, the topography may be not accurate or not spaced properly. I can testify from my own experience that the topographic map that was available to me of this area:
 seems like we are walking on a somewhat planar area without any steep slopes and only several meters of variability in elevation.

So what are your options? Some maps already have dip measurements built into them, thanks to the detailed work of the mapping geologist. If not, some structural maps of the same area may be available from the local geological survey/society. If you insist in making your own calculations, and the bed is rather planar, you can try to use a wider area for calculation (let's say 1 km instead of 100 m). You can try to take many measurements over an area and make a histogram of the measurements, or maybe examine the spatial distribution.


When specifying phase and amplitude for a tidal constituent, what date/time does phase start from? It is common to describe tidal elevations at a given location by giving the phases and amplitudes of tidal constituents. One such application is for setting the open boundary conditions for regional flow models.

However, the phase of a constituent is only meaningful if we also know a specific time at which that phase angle applies. For example, if a constituent has an amplitude of 2m and a phase of 127 degrees (perhaps more accurately called a phase offset), there must be a specific date and time at which it is at 127 degrees, from which it progresses at a rate specified by the period of that constituent.

Is there a convention as to what date and time this is?

Tidal constituents follow the expression: $\eta(t) = A cos (\omega t + \phi)$, where $\eta$ is the tidal elevation at a specific time, $A$ is the amplitude of the constituent, $\omega$ is the speed of the constituent (the rate of change in phase), and, finally $\phi$ is the phase of the constituent at the initial time from which the time is measured. The phase, $\phi$, is measured with regard to the equilibrium tide.
Thus, the short answer is that the phase is usually referring to the delay (in degree) from the theoretical equilibrium tide. From the NOAA glossary for phase lag (or phase epoch, not to be confused with the tidal datum epoch):

Angular retardation of the maximum of a constituent of the observed tide (or tidal current) behind the corresponding maximum of the same constituent of the theoretical equilibrium tide. It may also be defined as the phase difference between a tidal constituent and its equilibrium argument. As referred to the local equilibrium argument, its symbol is $\kappa$. When referred to the corresponding Greenwich equilibrium argument, it is called the Greenwich epoch and is represented by $G$. A Greenwich epoch that has been modified to adjust to a particular time meridian for convenience in the prediction of tides is represented by $g$ or by $\kappa'$. The relations between these epochs may be expressed by the following formula:
$G = \kappa + pL$
$g = \kappa' = G – aS / 15$
in which $L$ is the longitude of the place and $S$ is the longitude of the time meridian, these being taken as positive for west longitude and negative for east longitude; $p$ is the number of constituent periods in the constituent day and is equal to 0 for all long-period constituents, 1 for diurnal constituents, 2 for semidiurnal constituents,and so forth; and a is the hourly speed of the constituent, all angular measurements being expressed in degrees.


Are thunderstorms normal at the end of a heat wave? As far as I know, heat waves form when a high-pressure system builds up over an area. This forms a sort of "cap" over the affected area which prevents air from rising and cooling and then coming back to the surface. This results in a continuous buildup of heat leading to a heatwave. When a heatwave ends, I'm assuming that means the high-pressure system mixes with another low-pressure system. When two systems like these mix and there is moisture I believe thunderstorms are likely to form.
My question is if this reasoning is correct and if thunderstorms are common after a heatwave ends in areas where there is some moisture in the air at the end of the heatwave.
In other words, what exactly happens in the atmosphere when a heatwave needs and would this lead to increased chance of thunderstorms in areas where the air has some moisture?

Ingredients necessary for the formation of thunderstorms are

... moisture, rising unstable air (air that keeps rising when given a nudge), and a lifting mechanism to provide the “nudge.” (source)

as well as

... MOISTURE, INSTABILITY, and LIFTING. Additionally, there is a fourth ingredient (WIND SHEAR) ... (source)

and they depend on the local, regional or overregional weather situation, can have seasonal aspects, may be be bound to one or more circulation patterns or just depend on the weather ;-)
Thunderstorms can form isolated, e.g. in the afternoon when during the day the conditions have built up and labilization took place from different ground types, orography, sunshine duration/intensity/angle or "drops" of cold air high up in the troposphere. These are Orograhic thunderstorms or air mass thunderstorms. They are usually (but not always) short lived (hours), local and occur in the afternoon and last until the early night.
Or thunderstorms can form along a frontal line that separates cold from warm air mass and that moves into the warm, moist air, causing it to rise to great height where it starts to condensate. This phenomenon is called a cold front or in a special form a squall line (radar image) and labilization is here the result of the difference in air temperature and moisture on a relatively narrow frontal line. Frontal system have considerable length (100s or rarely thousands of km) and moves swiftly over long distances. These frontal systems can be part of the cylones in the temperate zones (not the tropical cyclones, those are different and I leave them out here, though they house embedded thunderstorms as well) and move with the prevailing western drift there. Such a frontal passage usually doesn't last long, comes with a significant drop in air temperature when passing overhead and a significant weather change and veering wind, on the northern hemisphere.
All these forms are expressions of convective weather, vertical movement of air caused by labilization.
Otoh, heat waves are frequently simply the result of dry and hot air being transported by advection, which is not bound to a local scale alone. For example the Sahara air to central Europe. This air is hot and very dry, and it simply lasts until the weather situation changes and different airmasses come along, e.g. of Atlantic origin. There won't be thunderstorms, then, because there's not enough moisture. Such a weather situation frequently happens on the Canaries (just as an example), it leads to a hot and extremely dry atmosphere until great height, with a cool layer underneath, for example 23°C at sea level, ~30° at 500m ASL with an inversion in between, and 35°C around the summits between 2,000 and 2,500m ASL. This is absolutely stable and not even slightly conducive for the formation of convection or any kind of precipitation (except sand :-/).
tl.dr: No, it is not normal, but it can happen. There is no general rule and it is not the absolute temperature that causes thunderstorms, but differences in temperature and moisture that cause labilization and thus convection.


Does nitrogen fixation plants consume nutrients from soil I am a farmer. I have lot of "touch me not" plants (Mimosa pudica)in my coconut plantation field. Many people are saying I have to get rid of them for two reasons:

It is very difficult to walk in the field for routine works.
These plants consume nutrients from main crops.

I am bit reluctant to remove these plants. I understand that these plants help in $\small\mathsf{N_2}$ fixation. Also these plants may protect my field from some of the animals I thought though it is inconvenient to walk.
So my main question is: Do these touch me not plants consume nutrients from the  fertilizer I put on coconut plants? Are there any ill effects of these plants?

I'm not familiar with the plants you mention, unless they are the ones whose leaves rapidly move away from you when touched. I saw some in Malaya. However, the plants well known for fixing nitrogen from the air and enriching the soil are legumes, belonging to the same group as peas, beans, alfalfa and clover. There are hundreds of them, and they all have similarly shaped flowers, though of many different colours.

They all have nodules on their roots which harbour the bacteria which do the actual nitrogen fixation. Like any other plant they also extract minerals from the soil, so the soil will be enriched with nitrogen but depleted in minerals. Farmers get round this difficulty by rotation of crops.

If the flowers of the plants you mention are similar in shape to the flowers of peas and beans they probably enrich the soil, and it is unlikely they remove enough minerals to harm your coconut palms. In England, farmers sometimes sow a legume like clover or alfalfa, then plough it back in so that the soil is enriched with nitrogen but not depleted in minerals. Perhaps you could do the same with your mimosa plants.

Most fertilisers contain nitrogen, and if yours contains anything else your mimosa will probably use a bit of it, but not enough to worry about. If your plants are indeed a kind of legume, that should enable you to use less fertiliser. If your touch-me-not plants have thorns on them, that's the only ill effect I can think of.


What is the most important source of natural gas? Coal, oil or other? By heat and pressure, both coal and oil can produce gas. But what is the most important substance for gas? Is there a relation to the amounts of marine organism (sea life) which died and the amount of plants and trees which was covered by sand or is oil (sea life) or coal (plants) just more capable of producing gas?

Else what is the alternative contributing source?

The most important source of natural gas is natural gas. This is why it is called natural. It is not "made" from oil or coal.

Natural gas forms by decomposition of organic material. Whether the organic material decomposes to coal, oil, or gas depends on the composition of the original material, time, pressure, and temperature. In theory, oil (=long chains of hydrocarbons) can decompose to gas (=mostly methane and small amounts of very short chains of hydrocarbons). I am not certain as to how much of the natural gas in existence went through this oil-like stage.

Coal cannot "become" natural hydrocarbon gas, because it contains no hydrogen. It can be burnt to form carbon dioxide, which is a gas, but this is not what you're talking about.


How does temperature impact the elevation distribution of orographic precipitation? Consider the case of two weather systems of different temperatures hitting the Andes Mountains from the west: After traveling a long distance over the Pacific ocean I would expect the air in both systems to be water saturated (i.e. Relative Humidity of 100%). However, the warmer system will be carrying more water and it will drop more water over the mountains (correct me if I got something wrong up to this point).

Now: Will the precipitation happen over the same elevation range? Or it will start to happen at lower/higher elevations?. Will the point of maximum precipitation stay the same? Or it will migrate upwards/downwards?

In case particular details are needed to answer this question, I'll describe now my main area of interest, that correspond to the Patagonian icefields, in the southern tip of South America between latitudes 46 to 51° South, roughly 500 km in the north-south direction. The area corresponds to the red box in the following world map:

The size of the area would put it in the the upper boundary of the mesoscale meteorology. However, topography gradients can vary quite a bit within the domain.

The following image show how the area looks from above, with a sat image on the left (where the ice extent is clear) and the topography on the right:

I have averaged the above elevation model in the north-south direction to obtain the average topography profile that Westerlies will face when hitting the mountains from the West (predominant winds come from between W and NW direction). This is how it looks:

The red lines (40 km apart) indicate roughly the currently ice covered longitudinal band. To the west of it, liquid precipitation dominates and there is no permanent ice cover. To the east, there is very little precipitation (dry pampas) and therefore no ice cover either.

The tree line in the area is usually between 400 and 600 m of elevation, represented by the green lines in the graph above.

The mean wind speed (from a 22 year average dataset) when the winds hit the land is between 7 and 8 m/s (25-29 km/h), as show by the shading and contours in this figure:

From the same 22-year average dataset. The typical 10-meter air temperature on the ocean just before hitting the land is between 6 and 7 °C.

Examining two extreme cases, one very cold and the other very warm, the amount of precipitable water in the very cold one will be far less than that in the very warm one.  Even fully saturated, the very cold air mass would need to be lifted quite high to form large enough ice crystals or water droplets to have enough mass to begin falling.  Meanwhile, the warm air mass would produce larger droplets very quickly.  Thus the warm air mass would begin to produce precipitation at a lower altitude, and with greater intensity.

Because the air masses begin precipitating at different altitudes, the point of maximum intensity would also be lower for the warm air mass.


Effect of urbanization on weather events At what stage is the studies on effect of urbanization on weather events (eg: Rainfall, Temperature, UHI) are now? There has been a number of observational and modelling studies around the world and it has been found (In my understanding) that urbanization cause increase in frequency and intensity of heavy rainfall, higher temperature, heat island, changes in boundary layer etc. in urbanized region, mainly due to land-surface change.
Now, What challenges and possibilities are there in this particular research field?

I did my undergraduate capstone on observational moisture changes around cities.  It's an interesting field, though it certainly seems fairly challenging to draw out and explain changes given the incredible spatial and temporal variability.  So that's definitely one of the challenges to it.  Another is the current observational density, as there are very few micronets setup and satellite resolution probably isn't helpful to diagnose variations on small time/distance scales.

But, while it definitely doesn't have near the attention (or money) that climate modeling itself does, there are a few sharp folks working in the field at least.  From my experience, having dabbled on the topic but having incomplete research familiarity particularly over the past decade, it would seem that theoretical microscale modelling might be the most fruitful research direction.  Computing power and models continue to step up, and there's much better room for experimentation.  But then, it'll still be very hard to demonstrate that those idealized simulations match reality, and impacts to connect changes definitively to theory/causes.

Indeed, if somehow sharp links can be made that are powerfully convincing, then work could be directed into reshaping urban planning to address such changes.


Ground level ozone formation and NO2 dependence over time I have a dataset which contains daily NO2 and ozone levels of the 50 largest cities in Spain for one year (so 50 x 365 observations). The data are retrieved from http://www.eea.europa.eu/data-and-maps/data/airbase-the-european-air-quality-database-7. When regressing ozone on NO2, I find a significantly negative coefficient for contemporaneous NO2 (-0.35, standard error 0.027), the first lag (-0.05, standard error 0.014), insignificant coefficients on NO2-levels on the second and third lag (-0.0014 and 0.014 respectively), and a positive coefficient on the level of NO2 five days ago (0.50, standard error 0.013).
I am also controlling for time-invariant local characteristics (fixed effects) and (lagged) weather conditions (temperature, sunshine, cloud cover, precipitation, wind).

I'm an economist so I don't know much about these things. I guess this could be explained by the complex mechanics of ozone formation? It would be great if you have some reference or idea why such a relation can be observed.

Edit: Added some more hopefully useful details.

I am unsure of the details of your dataset (length, temporal resolution, location, etc.)

For he one day time lag, it is easily explained. NO2 is consumed to produce ozone, so as NO2 decreases, O3 increases. However, for that reaction to occur, you need UV radiation. So as NO2 decreases, ozone increases.

For the fourth day lag, I would be a bit suspicious to take meaning out of this, due to my lack of knowledge on details of the dataset. For example, it could've been cloudy preventing the production of NO2 and ozone, but letting NO build up, such that when the sky cleared, the NO was allowed to photlyze, but that is just a guess.


What is Oligo-Miocene radiation? Some studies about Earth's fosilized plants/animals mention a "Oligo-Miocene radiation".

Examples:

  Our study therefore strengthens previous suggestions that the absence
  of very large penguins today is likely due to the Oligo-Miocene
  radiation of marine mammals.

from Mayr et al (2017), doi: 10.1038/s41467-017-01959-6

  Molecular phylogeny and dating reveals an Oligo-Miocene radiation of
  dry-adapted shrubs (former Tremandraceae) from rainforest tree
  progenitors (Elaeocarpaceae) in Australia

from Crayn et al. (2006), doi: 10.3732/ajb.93.9.1328, see also www.ncbi.nlm.nih.gov/pubmed/21642198

So, what is this "Oligo-Miocene radiation" ?

The ‘Oligo-Miocene’ part

The Oligocene and the Miocene are epochs of geological time. The Oligocene lasted from ~33.9 million years ago to ~23 million years ago; the Miocene followed immediately after the Oligocene, and lasted until ~5 million years ago.

Oligo-Miocene refers to events that happened around the boundary between the two epochs at ~23 million years, or that happened throughout the Oligocene and Miocene epochs.

The ‘radiation’ part

‘Radiation’ here is evolutionary radiation, a biological term usually referring to an increase in the number of species or in the differences between them. The Palaeontology Online glossary defines ‘evolutionary radiation’ as follows.

  An evolutionary radiation is an increase in either taxonomic diversity (i.e. the number of species) or morphological disparity (how they differ in anatomy). This can result  from an adaptive change or the opening of ecospace.

The combination

Putting the two parts back into the contexts where you found them: the first article mentions an increase in the diversity or marine mammals, and the second in the diversity of dry-adapted shrubs. Both these increases occurred between the start of the Oligocene and the end of the Miocene.


How did these grassy hillsides in Colombia become terraced? In Colombia, many grassy hillsides are terraced, like in the photo below. This terracing also occurs on hillsides that never had these palm trees on them. I assume that it also occurs outside of Colombia. How does this terracing happen?

Just from my first-hand observations, I think the answer is: The terracing was formed by grazing livestock. Grazing livestock is common in these areas, and the barbed wire fence hints that it is occurring here. On flat ground, the livestock wander in random directions. On steep ground, the livestock prefer to follow the hill's contour lines, as that is the easiest path to walk, as opposed to more directly uphill or downhill. When a livestock initiates a contour path on a not-yet-terraced hillside, that path is repeatedly trod by subsequent livestock, as it is a little flatter and easier to walk than other contour paths, eventually leading to significant terracing. The terracing is uneven (not level) because the livestock have to go up or down a bit to graze elsewhere on the hill.

Can anybody confirm my answer, or provide another answer that is objectively correct, preferably with citations? I asked the same question in the form of an SE puzzle, which is currently on hold because "This question may invite speculative answers, as the question is not fully defined. The validity of some answers may be based upon opinion. Good questions for this site [puzzling.stackexchange.com] have a limited number of objectively correct answers." I may be able to save the puzzle with a definitive answer here.

Click for high-resolution photo

Photo credit:
Angela Calle and Daniel Di Palma [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]
https://commons.wikimedia.org/wiki/File:Valle_del_cocora_-_wax_palm_02.jpg

These are terracettes https://en.wikipedia.org/wiki/Terracette#targetText=In%20geomorphology%2C%20a%20terracette%20is,them%20to%20move%20slowly%20downhill
  These are caused by natural earth movements as the slope angle is beyond the natural resting angle of the soil. These slopes are a result of rapid erosion e.g. by rivers and glaciers.
Solifluction https://en.wikipedia.org/wiki/Solifluction is a similar process.


From where do weather radar maps get their data? I see maps like this one all the time online and in the news. A moving map that shows clouds and stuff moving around with time. Where do they get the data from? Is it from a single source location or multiple locations? Also, is it free? Is it open for public access?

Images showing clouds mostly come from geostationary satellites. Geostationary satellites are at an altitude of about 36000 km, which allows them to monitor the same area of the Earth continuously. They stay in place relative to the Earth's surface above the equator thanks to balance between gravitational and centrifugal force. There are a few such satellites designated to operational weather forecasting, notably:

GOES-East & GOES-West operated by NOAA
Meteosat-7,-8,-9,-10 operated by EUMETSAT
MTSAT operated by JMA (Japan)

These satellites contain passive remote sensing instruments measuring incoming radiation in a number of channels, mostly visible and infrared. Visible is only available during the day, while infrared is available all the time. Radiation is captured on lines of sensors by scanning the view, which generally takes a few minutes to complete. Geostationary satellites are unable to capture polar regions above a certain latitude, because of the angle.

In addition to geostationary satellites, there are polar orbiting weather satellites:

NOAA-18,-19
MetOp-A,-B (EUMETSAT)

Polar satellites fly much lower (~800 km) and cannot provide continuous global coverage, only swathes along their orbits.

All of this data can be used in the assimilation (initialization) process of weather forecasting models. In turn, one can produce images of cloud cover from the output of the models, see e.g. wettercentrale.de.

NASA operates mostly research satellites, not so much operational weather satellites, although they do cooperate with NOAA on some of the missions. In Europe, the counterpart is ESA, who run some satellites on their own (e.g. Sentinel and in the past Envisat and ERS-1,-2) and cooperate with EUMETSAT.

The data from satellites is downlinked to communication centers (sometimes routed via other communication satellites), where it is processed by various algorithms into products (data files). Product files can be downloaded over the Internet by national weather services or are made available publicly to anyone (all data from NASA satellites is public - see e.g. NASA Global Change Master Directory).

Weather radars are generally located on the ground. They operate by sending short pulses of microwave radiation and measuring the reflected (backscattered) radiation from water/ice droplets. As the microwave radiation has relatively large wavelength (on the order of one millimeter), it is not very sensitive to cloud droplets, and you can see mostly bands of precipitation. Weather radars are operated locally by national weather services. You need roughly one per 250 km to get a good coverage. As with data from weather satellites, they are very important in assimilation of numerical weather prediction models. There are also spaceborne radars, e.g. DPR on GPM Core Observatory, TRMM, or CloudSat.


Is this why oceans are salty? From noaa.gov's Ocean facts:

  Salt in the ocean comes from rocks on land.

  The rain that falls on the land contains some dissolved carbon dioxide from the surrounding air. This causes the rainwater to be slightly acidic due to carbonic acid (which forms from carbon dioxide and water).

But...if this is the case wouldn't our rivers be even saltier from seasonal downpours and snowpack melt?

No, because fresh rainfall has no salt in it, so as long as the river keeps moving the salt has no time to accumulate.

Only stagnant sources of water on land, like lakes with no outlet, can become saline.


What exactly does it mean that Japan is the "land of the rising sun"? Only in later years have I understood anything about how our planet moves around itself and around the Sun, and how it therefore appears to always "rise in the East" and "set in the West", apparently "traveling across the sky" (but it's actually our planet that is traveling and spinning at the same time while the Sun is fixed in the centre). At least I'm pretty sure that there are no exceptions to this rule, but I wouldn't be surprised if things are different in other positions on Earth's surface.

Anyway, Japan is called the "land of the rising sun", supposedly because it is... far to the... East? But the Earth is spherical, so this has no meaning, does it? Yes, North is "up", but East... there is nowhere you can say that East "ends" because the most extreme East position on a 2D world map is just next to where the "West" is beginning. So is the idea that just because (some?) world maps have Japan to the right, and thus "East" in some misleading sense, then Japan is the "land of the rising sun"?

This confuses me. Does the sunrise and sunset have something particular about it when you are watching it from Japan, as opposed to central Europe or North America or anywhere else? Is this just a reference to semi-recent "Western" world maps? I'm pretty sure that Asian world maps place themselves in the centre rather than in the "far East"?

Nippon means "sun origin" or "land of the rising sun". From the direction and point of view of the older, larger civilisation of the continent to the West - China - the island of Japan were in the general direction of where the sun rises, with no known lands further East beyond them.

China was a powerful cultural influence for Japan. Nihon/Nippon was a nicer, more poetic name than the Chinese name of "Wa" - which was Chinese for "Dwarf"; Nihon/Nippon ("sun origin") was used, possibly intentionally, to supplant it within Japan.

I don't know if Japanese or Chinese historically understood that Earth was a globe but suspect it was largely irrelevant to that naming.


Why does the ocean seem much cleaner than the bay I live near I live in Melbourne near a bay, and it always seems really dirty, whenever I go out to the open ocean the water always seems much cleaner. Is there a reason for this, does the bay trap pollution or do the waves from the ocean break up the pollution or does the ocean simply have more area to store waste?

I had the same experience when I lived in Cardiff, South Wales. When I lived there, the waters around Cardiff were always greyish and uninviting, but the further away one got, the more blue-green and transparent the sea became. Fifty miles west on the Gower coast, the water was pristine and beautifully transparent, more like the Mediterranean.

The reason for this was two fold: a lot of effluent from the city, including sewage, was discharged into the sea, and the river Taff, which runs through Cardiff, brought down a lot of industrial effluent from the Welsh valleys. It is a matter of common sense that the sea dispersed and diluted the pollution the further away from the big city one looked. I understand that the river and the city are much cleaner now, but I think the murky waters of Melbourne which you describe are due to the same sort of causes which many years ago fouled the waters around Cardiff.


Why pro-gradation occurs along coastal environments? I am currently studying the deposition process in coastal environments and I came across a point which I do not understand concerning grading of grain size.

According to "Petroleum Geology by North F.K."

If deposition exceeds subsidence, high-energy deposits prograde over lower-energy deposits;hence grain size coarsens upwards.
If deposition and subsidence are in general equilibrium, stacked or multistorey sand bodies result.
If subsidence exceeds deposition, a series of isolated narrow, linear bars of sand become separated by wide strips having less sand. The sand bodies may still coarsen in grain upwards.

I actually don't understand why this happens, I tried to Google it but still no clue.

If deposition exceeds subsidence, then the water column shallows, the environment becomes more high energy, and so instead of muds and silt, the sediment would be coarser sand and gravel, so coarsening up.

If deposition and subsidence are equal, then the energy of the environment does not change, so similar grain sizes will be found throughout.

If subsidence exceeds deposition, then I'd expect the grain size to ultimately become smaller as the environment becomes more low-energy as the water column deepens. But what you wrote could refer to coarse material being less frequently reworked in such an environment.

Progradation merely refers here to the progression seen, as over time in the sediment size as a basin generally fills with sediments reflecting shallower environments, I think it's typically taught by the progression of sediments seen as a delta progrades into a basin. First with deep water muds, which coarsen upwards as the delta moves into the basin depositing sediment.

So what remains in the layered sediments we see, has a complex relation to the time of deposition, which might be more info than you require.(here's a link to a good diagram, which may help. LInk)


Is it possible to have an AR(0) for streamflow? Autoregressive models (AR) are extensively used to understand the behavior of streamflow. The literature abounds with examples of AR models from different families applied "everywhere" to fully understand how streamflow changes throughout the hydrologic year. One particularly well accepted model is the periodic autoregressive model, as in Hipel and McLeod (1984).

So far, from all I've ever read, all streamflow AR models will have a signficant first order lag. That is, when one calculates the PACF to find the order p of the model, p will assume a value of 1, at least.

Is there any known case registered in the literature of an AR streamflow model of order 0, i.e., AR(0) for streamflow? That is, is there a possible way that the "yesterday's flow" won't explain the "today's flow"?

Autoregressive models are mathematical models, and like all models, are based on a conceptual model of the system. The conceptual model is that prior flow is a parameter in prediction of current flow. So it doesn't really make sense to have a model where it does not do so.

Furthermore it is difficult to conceive of a natural system where prior flow is not a predictor. This is where I disagree with Gordon's answer. Even in small catchments, prior flow is a good surrogate for the physical conditions that contribute to flow. The conditions include precipitation history, soil moisture, filling of depressions so flow can accumulate, capacity for trees to intercept precipitation (are the leaves already wet), water-table stream connectivity, etc.

If you don't see a relationship to prior flow in small catchments, that may just mean your daily timestep is too large. I care about the flow variation in very small catchments and monitor the flow on 30-minute intervals.


Can the forecast N+1 days ahead be more certain than the forecast N days ahead? The Swedish meteorological agency SMHI on its website (NB: freezes Firefox on Linux for me, likely due to plugins, works in Chrome) indicates how certain the forecast for a particular day is.  Looking at today (Wednesdays) forecast for the coming week for Kvikkjokk, they estimate that the forecast for Friday is ganska säker (somewhat certain), for Saturday is osäker (uncertain), and for Sunday is säker (certain); they estimate that the forecast for Sunday is more certain than the forecast for either Friday or Saturday.  I suppose that what they do is look at the forecast ensemble and estimate certainty based on agreement between different runs from the ensemble.  But as the state of the atmosphere on Sunday should depend on the state on Friday and Saturday, is there any way how it can make sense that the forecast for Sunday is more certain than the one for Friday or Saturday?

Typically, days with conditions which might produce local instabilities would produce a less certain forecast than a day with a stabilize pattern even if the more stable day was further in the future.  For instance, tomorrow may have the potential for localized disturbances some maybe there will be thunderstorms, maybe they will not form.  But two days later, a large high pressure zone will almost certainly clear everything out or a band of rain will definitely reach the area.


How many mines are there on Earth, and what is their output in tonnes? I am writing a space colonization game, and I need some guidance on default values for mine productivity. If you also know an estimate of how much people work on them, that's a bonus. Thanks in advance :)

You can get estimates from the USGS mineral yearbooks. For example, the entry on Australia has a data table with the amounts of mined resources. Or, the entry on copper lists both US production and international production, including numbers of people employed.

More number are available from government statistics websites, regarding employment. For example Australia and USA.

Digging through those websites will give you an order of magnitude of what to expect.


Hurricane eye on landfall and relation to wind speeds I am not a meteorologist but watching Hurricane Irma (2017), I have a couple questions about how hurricanes keep their formation based on geographical landmarks.

How does the radius of the hurricane's eye affect the winds felt by
those at different distances from the eye?
When a hurricane reaches land, how does the land affect the eye's
formation?

The winds are at a maximum velocity Vmax in they eye wall, a thin annulus immediately around the eye. With increasing distance the winds fall off. If a hurricane was a Rankine vortex, the wind velocity at radius R from the center of the eye would be V(R) = Vmax X (Reye/R), where Reye is the radius of the eye. In reality friction usually prevents a hurricane from being a perfect Rankine vortex. Instead it typically a modified Rankine vortex, with V(R) = Vmax X (Reye/R)^n, where n is typically in the range 1/2 < n < 3/4 (perhaps n = 2/3 is the best overall average value). Of course this is a radially-smoothed-out wind velocity distribution. In the approach of an actual hurricane, wind does not increase monotonically as R decreases. But V(R) = Vmax X (Reye/R)^2/3 typically approximates the secular trend of its increase.


How is heat transferred from the core through the mantle to the crust? So, there are three main methods of transferring heat: radiation, convection/mass transfer, and conduction. Presumably radiation is not a major method of heat transport between the core and the crust, because it requires transparent materials (or a vacuum), and I don't think there is much of either in the mantle. Presumably conduction is the only significant method of transport in the crust, apart from volcanos.

So, in the mantle, between the core, where heat is generated, and the crust, where it is eventually dissapated, what proportion of heat is transported via convection and conduction?

It is still a little known fact that radiation play an important role in the Earth's mantle. Experiments show that mantle-material becomes transparent to infrared radiation at increasing pressures (http://www.esrf.eu/news/general-old/general-2004/earthbadro/index_html).

I would also say that the mantle is currently not understood in a way where estimates of heat-conduction-type versus depth can be accurately made. The heterogeneity of heat transfer (Cold detached subduction-slabs sinking to various depths and hot plumes quickly rising from the D''-layer) makes the question even more difficult.


What is meant by intraplate volcanism? I am having massive confusion on whether intraplate volcanism refers to volcanism occurring at plate boundaries or away from plate boundaries (such as formation of ocean island basalts), or perhaps both?

Also, are mid-oceanic ridges related to intraplate volcanism?

Terms:
Intraplate volcanism - as the name suggests it is volcanism within the plates rather than at plate boundaries.

These are also known as hotspots.

Ocean island basalt (OIB) - is the basaltic rocks associated with intraplate volcanism.

Relation between mid-ocean ridges and hotspots:

Hotspot–ridge interaction produces a wide range of phenomena including excess crustal thickness, geochemical anomalies, off-axis
volcanic ridges, and ridge relocations or jumps.

For further study refer to this research paper.

A conceptual schematic of a ridge jump from that paper:

Image Source

DR: Dying rift
PR: Propagating rift

There is a ridge jump towards the hotspot.  Due to the ridge jump lithosphere from plate B is transfered to plate A.


What is the white coating "patina" we often see on deposited chalcedony/agate? Me and some of my friends were wondering what exactly is the white coating we can see on chalcedony that has been deposited by a river during quartenary (and so the original material is damaged and has a lot of cracks in it). This is an example:

What is the white coating ? Is it opal ? Cacholong ?

So far everything I found was this link:
http://www.treasurenet.com/forums/north-american-indian-artifacts/238703-agate-arrowhead-white-patina-question.html

These people describe it as "patina" or "chalcedony weathering". I am wodering what is the process and how can we easily chemically or physically explain it ?

I think it must be some kind of weathering.. similar to oxidation. I believe that it is opalization. What do you think ? I saw this forming on many agates all over the world, but only at these, that were eroded from the mother rock, transported and deposited. It is especiially common on deposited chalcedony.

Thank you.

The white "patina" is most likely some form of opal as you suggest. I did some research and I'll explain how the agate becomes opal and why it's more common in the eroded rock.
Some background:

agate and opal are both forms of silica with the chemical formula SiO2
opal is a hydrated amorphous form of silica (1)

You would find the opal more often on weathered and deposited chalcedony because "the polymerization of silica into three-dimensional gel-like networks [opal] is favored in the pH range 3 to 10 where dissolved salts are present in solution."(2) The pH of stream/river water ranges from 6.5 to 8.5 and all natural water has salts of some kind. (3) Therefore, dissolved silica in stream/river water reacts with the agate and opal grows onto it.

To sum up: yes, the "patina" is most likely opal and it forms when stream/river water interacts with the agate.

sources:

https://en.wikipedia.org/wiki/Opal
https://rruff-2.geo.arizona.edu/uploads/CM46_139.pdf
https://www.grc.nasa.gov/WWW/k-12/fenlewis/Waterquality.html

Source 2 talks about various types of opal formation, but for simplicity's sake I only mentioned polymerization.


How do we determine subsurface composition? Let's assume that a seismogram $s(t)$ is the convolution $s(t)=r(t)g(t)$ between a source signal $r(t)$ and propagation effects $g(t)$. If the source signal $r(t)$ is known, then we can obtain the propagation effects using a Fourier transform; that is,

Original equation (time domain):  $s(t)=r(t)g(t)$

Fourier transform (frequency domain):  $S(w) = R(w)G(w)$
where $S(w)=\mathcal{F}[s(t)]$, $R(w)=\mathcal{F}[r(t)]$ and $G(w)=\mathcal{F}[g(t)]$

Solve for the unknown:  $G(w) = \dfrac{S(w)}{R(w)}$

Inverse Fourier transform:  $g(t) = \mathcal{F}^{-1}\left[\dfrac{S(w)}{R(w)}\right]$

My question

How do we use the information in $g(t)$ to determine the composition of the medium that the wave is traveling through? Moreover, knowing that the earth is heterogeneous, how can we isolate any one single substance or rock type?  How accurate is this kind of measurement?  How can we minimize the uncertainty in this measurement?

How do we use the information in g(t) to determine the composition of the medium that the wave is traveling through? Moreover, knowing that the earth is heterogeneous, how can we isolate any one single substance or rock type? How accurate is this kind of measurement?

In short: we can't, and it's not.

Taking the example of oceanic lithosphere, we can take a pretty good stab: we know (approximately) what a cross-section through the oceanic crust and mantle looks like because of the existence of ophiolites. They're pretty consistent in terms of thicknesses of units represented (see the cross-section at that link), so when in oceanic lithosphere we see 2km at a certain velocity underlain by 4km at a different velocity, with a sharp transition between the two, it's a fair bet that the former corresponds to sheeted dykes and the latter to layered gabbros, and so on down.

Some laboratory measurements of the speed of sound waves in various lithologies can be made (including measurements of both synthetic substances and of mantle xenoliths that have, for whatever reason, been brought up to the surface), but they aren't definitive. Seismic anisotropy - different "speeds" to different components of wave phases (e.g. P versus S waves) depending on the angle the wave being measured took through the rock in question - can be linked to e.g. alignment of olivine crystals. As another example we know that the core is of a different composition to the mantle because of the difference in the speed of sound and through mass-balance arguments, but seismic velocity through the core doesn't tell us anything about what it's made of.

To add further complications, variations in seismic speed can always be explained by a trade-off between compositional and thermal variations, as with LLSVPs.

Mostly what we're working with here is a bunch of best guesses. That's not to say they're useless - in a field where you get to run a single experiment that lasts 4.5Ga and you've no control over any of the parameters, best guesses are often the best we have to work with - but they're also very definitely not definitive.


How to get single value of NDVI value from four different directions? I have a data set which contains NDVI (Normalized Difference Vegetation Index) values of four directions (NE, NW, SE, SW). Now, I would like to have single value which considers all 4 directions. Is it fine to take an average or is there any other metric that can be considered? Any suggestions on which is the appropriate method?

More information on the data source:

This data is from a competition from Driven data

NDVI is
Satellite vegetation - Normalized difference vegetation index (NDVI) - NOAA's CDR Normalized Difference Vegetation Index (0.5x0.5 degree scale) measurements

After given some information about the data source I have a simple answer. Since the underscores SW etc. represent the four pixels around the city center and all the pixels cover the same physical area, taking a mean of the values will represent the average NDVI of the total area.

It is all about what you will do with the NDVI data. E.g. if something interesting occurs when somewhere near the center vegetation amounts are low (high), then the minimum (maximum) of these might provide you with more useful predictor.


How much Uranium is there in the Earth's Crust? Are there any estimates of the amount of Uranium there is in Earth's Crust?

From what I know, it's supposed that there are large amounts of Uranium in Earth's Core, the decay of which is responsible for the core maintaining its high temperature. Mining the core is hardly imaginable, while the resources in Crust are more accessible available for mining: so how much is in the Crust, and at what levels of concentration? (which affects the viability of accessing it).

According to wikipedia, there are around 5.5 million tonnes of uranium in ore deposits that are commercially viable at current prices, and perhaps 35 million tonnes that are potentially viable if prices increase.

Also according to wikipedia, the Earth's crust (to 25 km depth) contains an estimated 10^14 tonnes (100 trillion tonnes), while the oceans may contain 10^10 tonnes (10 billion tonnes). This presumably includes the ore figures stated above.

The previous link states that "The decay of uranium, thorium, and potassium-40 in the Earth's mantle is thought to be the main source of heat", however no estimate is given for quantities. Allègre, Lewin and Dupré (1988) state that "The concentration of U in the primordial mantle (bulk Earth) has been determined to be ~21±1 ppb". Back of the envelope calculations would then give us that the mantle is 84% of the Earth by volume (probably slightly less than that by mass?), and the mass of the earth is 6*10^21 tonnes, which would give us, very approximately, 0.84 * (6*10^21) * (2.1*10^-8) ~= 10^14 tonnes, or roughly the same as is in the Earth's crust.

Allègre, C.J., Lewin, E. & Dupré, B., 1988. A coherent crust-mantle model for the uranium-thorium-lead isotopic system.
Chemical Geology, 70(3), pp.211–234.


How does a tsunami affect biology and other matter in its path while in deep water Is everything in the water column going to be affected?

The answer to your question, based on linear theory, is no. The short answer is that the slope of these waves is very small, and the displacement of the particle paths is proportional to (ak) (times, perhaps, a depth dependent term) with a the wave amplitude and k its wavenumber. Now let's make this answer rigorous.

Recall, for irrotational inviscid 2 dimensional water waves the governing equation is

$$\nabla^2 \phi = 0$$

where $\nabla^2 \equiv \partial_{xx}+\partial_{zz}$ and $\phi$ is the velocity potential. We require particles on the free surface to remain there, and for the pressure to be continuous across the air-water interface, which gives us (assuming the atmospheric pressure to be 0) our surface boundary conditions

$$\left.\eta_t+\phi_x\eta_x = \phi_z\right|_{z=\eta}; \quad \quad \left. \phi_t+\frac{1}{2}(\nabla \phi)^2 +gz=0\right|_{z=\eta},$$

where $\eta(x,t)$ is the free surface displacement. Finally, we require the bottom to be impermeable, hence

$$\phi_z = 0 \quad @ z= -h$$

for $h$ the depth of the water. These are a closed set of equations. Note, the governing equation, ie Laplace's equation, is linear and hence simple to solve. However, the free surface conditions are nonlinear, and more significantly, evaluated at a moving interface. This last condition makes these equations very difficult to solve.

Therefore, to make progress, we generally take asymptotic expansions of these equations. Here, we'll just linearize the equations about some small parameter $\epsilon = ak$ for characteristic wave amplitude $a$ and wavenumber $k$. We will also consider periodic monochromatic waves, so that one can show that the following $\eta,\phi$ satisfy the governing equations to first order in $\epsilon$:

$$\eta = a \cos \theta; \quad \phi = a\omega \sin \theta \frac{\sinh k(z+h)}{\sinh kh},$$

where $\omega$ is the angular frequency given by the dispersion relationship

$$\omega = \sqrt{gk \tanh kh},$$
and $\theta\equiv kx-\omega t$.

To answer your question, we would like to know the behavior of a particle with position $(\xi+x_o,\zeta+z_o)$ originally located at some position $(x_o,z_o)$.This is the Lagrangian description of the fluid. Recall, we can relate the Eulerian and Lagrangian descriptions of a fluid through the velocity field, that is

$$\phi_x = \frac{d \xi}{d t}; \quad \phi_z = \frac{d\zeta}{dt}.$$

Substituting in the relations for $\phi$ found above, and then integrating in time, we find

$$\xi =-a\frac{\cosh k(z_o+h)}{\sinh kh} \sin \theta_o; \quad \quad \zeta = a\frac{\sinh k(z_o+h)}{\sinh kh} \cos \theta_o,$$
where $\theta_o =kx_o - \omega t$. We note that the particle displacements from the origin scales with the wave amplitude $a$.

Now, we can eliminate $\theta_o$ by squaring the expressions for the particle position to find

$$\frac{\xi^2}{\left(a\frac{\cosh k(z_o+h)}{\sinh kh} \right)^2 } +\frac{\zeta^2}{\left(a\frac{\sinh k(z_o+h)}{\sinh kh} \right)^2 }= 1$$

which describes an ellipse. I've attached a figure from Kundu and Cohen which illustrates this.

Now we can finally talk about some physics, and answer your question. For deep water waves, when $kh \ll 1$, the above relation reduces to the equation for a circle, hence the particles have a circular orbit which decays with depth (with an e-folding scale that goes like the wave number). For shallow water waves, i.e.  $kh$ small, our equation describes an ellipse with a semi major axis that is much much larger than the semi minor axis, hence there's is nearly horizontal motion that doesn't decay much with depth.

Tsunamis have wavenumbers that are large enough so that even in the middle of the ocean they fall into the shallow water regime, meaning that the particle trajectories are approximately very flat ellipses, or horizontal lines, and this does not decay with depth. However, their deviations from their origin will be very small, as their slope $ak$ is very very small, e.g. $\mathcal{O}(1^{-5})$ for numbers I looked up online. Therefore, it's very unlikely that this will have much of an effect on a passive tracer.

Now, the story is very different as the wave approaches shore and steepens. But this is a different story for a different day.

I hope this helps. Feel free to ask any other questions,

Nick


How big does a lake have to be to have its own Sea Breeze? How big does a body of water need to have a sea breeze? Is there a chart on sea breezes wind speed that include lakes?

Could a circular lake create enough sea breeze to create a wind vortex in the center of the lake?
https://worldbuilding.stackexchange.com/questions/108896/could-a-city-be-built-out-of-balloons

Lake breezes(similar to sea breezes) are fundamentally a feature of mesoscale meteorology and the peer reviewed reference Small Lake Daytime Breezes:
Some Observational and
Conceptual Evaluations details both the observational studies of lake breezes and the conceptual understanding behind the formation of the lake breeze.

Since OP's question is

  How big does a body of water need to have a sea breeze?

The answer according to this book Climate in a small area which is one of the references in the first reference is that lake breezes have been observed in lakes with a width of about 4 kms(Lake Suwa, Japan ) and a width of 10 kms (Lake Constance, Switzerland). The lake breeze reached a speed of 2 m $s^{-1}$ in the case of Lake Suwa and slightly greater speed in the case of Lake Constance. But because both of these lakes are orographic lakes the presence of thermally induced upslope flows (diurnal heating and consequent upslope flows during the day)  can interfere with the formation of lake breeze.

Further observational studies carried much later for the following lakes  Lake El Dorado , Lake Okeechobee, Lake Winnipeg and Lake Eufaula have reported lake breeze speed values in the range of 2-4 m $s^{-1}$. One must remember that these lakes are much larger in size but in essence the numbers capture the range of the lake breeze values. These observations had been obtained as a result of measurements carried out over a period of few months and over different weather conditions.

The upper range for the lake breeze is around 6 m $s^{-1}$ and any lake having a width of less than 2 km is likely to have an undetectable lake breeze.

So the physics behind the lake breeze formation in essence is similar to the physics behind the sea breeze formation. A pressure gradient(density gradient) is created between the land and the lake and this gradient is primarily established in the lower troposphere. Greater the inland sensible heat flux greater the value of the pressure gradient.

The following URL shows satellite images of different stages of formation of a lake breeze during the day - Lake Breeze Satellite Imagery

In regards to the second question I believe steam devils are mesoscale vortices that have been observed to form over lakes. These vortices are no more than 50-200 meters wide and can develop in the absence of any major synoptic scale forcing. But the surface area of the lakes have to be in the range of Great Lakes of North America  in order for the strong surface heat fluxes to play a role in mesoscale vortex development. The following peer reviewed reference provides observational and modeling studies of steam devils- Mesoscale spiral vortex embedded within a lake


Software to draw maps based on Earth I am looking for a tool to sketch changes to Earth. It should start with a geoid or an Earth model, rise/lower/flood selected areas. "Heal" boardersk: if an island is added in an ocean height shouldn't abruptly change from 0 $m$ to $-$1000 $m$. It should also measure distances between points, allow labeling and export maps of selected images as raster graphics (jpg image).

So far I could do two things:

Start with Google Earth, prepare necessary shapes using flooding, paste results as layers in Gimp/Photoshop [fast and ugly]
Import data in Matlab, define rules for modified regions, export [manual rule definitions is slow, no way to smart select, drag and drop regions]

What is the standard approach to do this? For instance, how people display flood plains, draft a channel or a new island project?

Windows/Mac/Linux/doesn't_matter? Windows preferred, Linux is OK.
GUI or also command line? GUI, or GUI+CLI batching. CLI only is undesired.
Go you want to use a GIS? I didn't know about GIS. Looking into in.

The most common software for creating and modifying maps is ArcGIS (commercial but you can get free trial for a month) or QGIS (open source).


The rock that gives birth to quartz sand Thanks to one minute of the Earth we know that beach sand mother rock, besides the quartz itself, is (or was?) made of olivine, amphibole and orthoclase. I wonder, what is the name of that rock and where do the 3 annihilated minerals go if only quartz is left?

In only one minute of presentation there isn't time for detailed discussion, so one has to make broad generalizations which, on closer inspection, aren't quite true. It is true that most sand is made of quartz, and that most of this quartz arises from weathered granitic rocks, of which the main minerals are quartz, orthoclase and plagioclase, usually with some mica, quite rarely some amphibole and almost never olivine. In the magma olivine and quartz react to make either amphiboles (if it is a very hydrous melt) or pyroxenes.

It is possible to find a sedimentary rock made of weathered out quartz and feldspar grains. Depending upon the original chemistry the feldspar could be potassium-rich (orthoclase) or sodium-calcium-rich (plagioclase). The resulting sedimentary rock is known as an arkose. Arkose is common in dry areas of eroding granite, such as the dryer parts of sub Saharan Africa. However, it is much more common for the weathering to involve wet erosion - thousands of cycles of rain and sun, hot and cold, in which case the feldspars mostly decompose to clay (many varieties and sub-species).

Olivine is much more characteristic of basic volcanic rocks, especially basalts, which do not weather to yield quartz grains. Another rock type in which olivine is a major component is peridotite. This weathers to yield goethite (a kind of ironstone) and serpentine. Occasionally, if the pyroxene to olivine ratio is sufficiently high, the weathering can yield quartz as a secondary by-product.

Another feature of quartz: Over long periods and especially at high temperatures and/or high pressures, it is very slightly soluble. Not that you would notice. The sand isn't going to dissolve beneath your feet, but every litre of surface water contains a few milligrams of dissolved quartz as silicic acid, which takes part in a whole catalogue of geological processes. In addition, there are many other rocks besides granite which yield quartz grains, including quartzite, weathered pre-existing sandstone, schist, gneiss, and some intermediate rocks (complex chemistry between granite and basalt. Even limestone - rocks that are generally thought of as 'pure' calcium carbonate, generally have a percent or two of insoluble residue, of which quartz is the dominant component.


When does the Northern Hemisphere reach minimum land area covered by solid H2O? What's the average day of the year when the fewest square miles of the hemisphere's land is covered by snow or ice or transitional forms like slush? Not counting anything below ground like permafrost or uh, temporaryfrost.

Maybe the land minimum is pretty late since North Pole air temps seem to flatline near freezing for ages? That seems to imply there's enough insolation to make it above freezing in the Arctic for quite a while if there was no snow or ice there to chill it by melting. So maybe the last non-permanent snow finally melts in late August or September or something and the ground has like 1-2 weeks before avg temps reach freezing again?

A little Google searching and I found this:

Source:  https://nsidc.org/cryosphere/sotc/snow_extent.html

Snow-cover is considered an important factor in climate change study, so it's tracked pretty carefully.   There's probably a specific average minimum date out there somewhere if you're really interested but I didn't see it.  Judging from the chart, somewhere around mid August.

Sea ice cover is later, that reaches a minimum in September most years, but oceans are slower to change than land and air, so that should be expected.   The hottest day on average, if you care about that, is July 24.   http://m.weatherbug.com/weather-news/weather-reports/5225


Does rain itself affect barometric pressure? I understand how and why low pressure systems are often associated with rain, but does the rain itself (both during and after) alter barometric pressure in any meaningful way?

Under a hydrostatic assumption the basic equation is p=/rho R T. So under this easy equation the pressure depends to the air density and the air temperature. As you may know diabatic processes during rain yield to a decreasing temperature. but the magnitude in change of pressure against the synoptic scale forcing is low.

Please be aware of mixing stuff together answering this questions. The question was not to answer how precipitation is forming. It was just the question about the rain influencing the pressure.


Do large-scale modes of variability (like NAM/SAM/ENSO) exist in the ocean? Large-scale patterns of climate variability can be explained at this Annular Modes Website.

If so, have they been characterized by EOF analysis in the same way that the annular modes in the atmosphere have been characterized? Where would be able to find this?

The large scale modes of variability present in the atmosphere are also found in the ocean. There is a strong feedback between the two systems with wind, heat flux and atmospheric pressure modifying ocean surface conditions and with parameters such as sea surface temperature altering atmospheric conditions.

A lot of studies have explored teleconnections in the ocean looking for instance at the EOFs of sea surface temperature. A good compilation of different atmospheric and oceanic time series and references can be found in Climate Indices: Monthly Atmospheric and Ocean Time Series.


How was it possible that CO2 levels were higher nearly 650,000 years ago? Recently I've been working on a debate for climate change and I'm working on a rebuttal statement but then I came across many different sites that claimed that there were higher CO2 levels before there was even industrialization or a substantial amount of CO2 being made from humans. I just need an explanation on how this happened.

The explanation is that human activities are not the only processes that affect atmospheric composition.

Last time CO2 levels were higher than today was 10-15 million years, during the Miocene epoch. During the Miocene, sea level estimated to be 100 feet higher and the global average surface temperature estimated to be 10°F warmer than today.

References:

Miocene Sea level graph.

Temperature over time graph.

www.climatecentral.org

Coupling of CO2 and Ice Sheet Stability Over Major Climate Transitions of the Last 20 Million Years


Are there any photographs of mountains without significant erosion (on Earth or otherwise) I'm curious about how mountains on an airless world such as the Moon would look if you were standing on the surface and looking at them. There are plenty of artists' impressions, of course, but I'm curious about whether there are any existing photographs of such a scene.

From browsing photographs of the Moon landings, there are a few surprisingly rounded-looking low hills on the horizon, but not what you'd call an actual mountain. This makes sense, since the missions targeted large flat areas where it would be safe to land. There are photographs of mountains seen from Lunar orbit, but not from the surface.

There are photographs of Mount Sharp from the Curiosity mission to Mars, but Mars has an atmosphere, and to my untrained eye Mount Sharp looks quite eroded.

So I'm wondering whether there are any such photos in existence at all - either because a probe has landed on an airless body close enough to a mountain to get a picture, or because a camera in orbit has been aimed at the horizon in order to capture a mountain range from the same angle at which it would be seen from the surface.

Alternatively, are there any mountains on Earth where (for whatever reason) erosion hasn't played a big role in shaping them so far, and which therefore look similar to the uneroded mountains one would find on an airless world?

Here's how astronomers of the late 19th century thought the Moon would appear:

Recreations in Astronomy by H. D. Warren D. D., published in 1879, via http://en.wikipedia.org/wiki/Selenography.

Here's what Apollo 15 astronauts saw:

  Apollo 15 Lunar Module Falcon at the Hadley-Apennine landing site. Hadley Delta in the background rises approximately 4,000 meters (about 13,124 feet) above the plain. The base of the mountain is approximately 5 kilometers (about 3 statute miles) away.

Source: NASA, from Four Out of Six Apollos.

Below is a photograph of the even taller Mons Hadley, 1.1 km taller than Hadley Delta shown above:

Source: NASA, photograph as15-86-11603, from Apollo Imagery.

Compare the above with mountains on the Earth. Here's a picture of Mont Blanc, a mountain here on the Earth comparable in size to  the smaller of the two lunar mountains portrayed above:

Photograph by Zoharby, taken from Wikimedia Commons, licensed under Creative Commons Attribution-ShareAlike 3.0 Unported license.

  Alternatively, are there any mountains on Earth where (for whatever reason) erosion hasn't played a big role in shaping them so far, and which therefore look similar to the uneroded mountains one would find on an airless world?

Nathaniel, you have a mistaken view of erosion. Erosion eventually does tear the tallest mountains down to tiny little hills. However, erosion also makes those tall mountains very jagged at first. Erosion is the primary reason why Mont Blanc and other new, tall mountains are so jagged. Liquid water seeps into cracks in the rocks and then freezes into ice. Ice has a lower density than water. This means that liquid water expands upon freezing. That expansion breaks the rock that form mountains into jagged edges.

Another reason our mountains are jagged is plate tectonics. The Earth is the only body in the solar system that exhibits plate tectonics. New continental crust forms largely from older continental crust. Erosion eventually brings particles torn from mountains to a flat area or river delta, where they collect. The material brought to those collection areas changes over time. The end result: Strata (layered rock formations). The different strata in rock have different strengths and weaknesses and thus erode differently. That differential erosion results in jagged mountains.

Bottom line: You don't see jagged mountains on the Moon or Mars because they don't have water in all three phases and because they don't have plate tectonics.


Do humans cause a DST-related shift in average daily temperatures? Inspired by the title to this question, is there a shift in average daily temperatures caused by the DST change in human activities?

I can picture any number of mechanisms by which a shift could happen (eg. more cars driving past the thermometer at the time the measurements are taken), so has such a shift been found?

Firstly you need to define what you mean by average daily temperature. What algorithm are you going to use to compute it (from several time spaced measurements), why and what do you think the result represents.

Obviously if you use a measurement which is going to be affected by very local anthropogenic activity (e.g. cars) you can expect timing of activities to affect individual measurements. a measuring station which is going to be thus affected is not really going to be useful for anything wider or general    though.

When siting weather stations we try to find locations which are not subject to such local disturbances. Ideally well away from any heat producing apparatus (e.g. fixed a/c units), heated buildings, variable traffic and so on. Locations in open non urban areas are preferable for understanding changes in the weather and climate. Past locations thus chosen however have often been compromised by the expansion of nearby housing or industry as populations and cities have expanded. This is why you sometimes see references to Urban Heat Islands (UHI) in discussions of climate measurement.