What do ice core samples really prove?

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ice cores show what earths past climate was like with records of Co2 and other atmospheric gases are recorded.
From the deneir point of view they play up long defunct deneir nonsense like the lag theory. In as far as the record of past natural climate change goes there was indeed a lag this has always been mentioned in the science, but in a fine example of how denial works they take part of the science and leave out the parts they don’t like.
https://www.skepticalscience.com/co2-lag...
The ice core data refers to the glacial cycles which is not started by Co2 it is started by changes in the Earth long term orbit and tile to the sun, after 600-1000 years Co2 starts to add to this natural effect and the the planet warms. What is happening now is not being started by long term orbital shifts but by mhuman actions.
This of course is one of very many theories deneirs have invented over the years, to try and explain away current climate change, all have long since been shown to be wrong.
Here is a listing of many of those excuses deneirs have tried over the years, it numbers well over 100 many actually conflict with each other but deneir tend to ignore this.
https://www.skepticalscience.com/argumen...

Answers

Through analysis of ice cores, scientists learn about glacial-interglacial cycles, changing atmospheric carbon dioxide levels, and climate stability over the last 10,000 years. Many ice cores have been drilled in Antarctica. Antarctic ice core drill sites with depth and record duration. From the US ITASE project.

That there used to ice a long, long time ago.

They prove nothing. They are evidence.
For a proof, proper logic must be applied along with the testable evidence.

I preface my answer by saying that I do not necessarily believe the ice core data as it is currently being presented. The 800 year lag is a function of the adjustments that are applied. However, if you "believe in science" then you should be able to justify the presented results.

Cause and effect is very hard to demonstrate. The only crucial point is that cause must precede effect. That, in itself, is still not proof but it is a necessary condition. If that condition is not met then all bets are off.

Correlation of two different signals in a time series graph is open to misinterpretation when eyeballing the data. Slopes can precede other slopes just because of the scaling factors used. You need to do the math(s).

However, that shows an 800 year lag. So, if there is a causal relationship the only one that is possible is that temperature causes CO2 to change. If we look at a descending slope then the temperature fall drags the CO2 right down with it. For 800 years, with record, and increasing, CO2 levels, the temperature drops. That has to be a significant observation.

You can side with skepticalscience and concentrate on the increasing slope and say that most of the increase takes place when CO2 is increasing but that is just BS. If you consider the cooling slope then the CO2 is still there but the temperature continues to fall. OK, CO2 may cause warming but even with record levels it failed for those 800 cooling years. Why would it be successful with lower levels of CO2?

The conclusion has to be that, at several points in history, temperature has gone its own way for many centuries completely independent of CO2.

Questions include: Is that 800 year lag still in effect? If it stopped, when and why? Is there a scientific mechanism that would explain it? I would say, yes, warm water holds less CO2.

"Prove"?
They provide evidence for the composition of the atmosphere of the recent past but that evidence has to be weighed with the limitations from various factors including the long time that it takes for fern to form and trap the bubbles of air and the differences in how different gases dissolve in water and move through the ice as it is formed.I think they are probably a pretty good proxy for relative gas percentages in the atmosphere during the hundred + years it was trapped.Plant stomata proxies seem to be at odds with ice core data and they tend to indicate that the atmospheric CO2 concentrations is more variable than ice core data suggests.Since ice core data seems to be a pillar in AGW alarmists belief system, it is blasphemous to even challenge it.If any proxies differ in what they indicate, a good explanation needs to be made for why.

Clearly warming tends to increase CO2 in the atmosphere in the past.Since we have been emitting CO2, we are obviously adding to that increase but the ocean holds so much CO2, it is hard to know what the CO2 concentration would have been without our emissions.You can't determine that by looking at ice cores, at least not without numerous limitations.You also can't "prove" the CO2 caused the warming we have had in the last 100 or 300 years.

That the climate is cyclical

They are a record of the weather going back tens of thousands of years.One can see the trends that make climate.They are one excellent way to show that the Earth is warming, or cooling, and just when these things happened.Volcanic activity is also recorded (as layers of volcanic ash).Chemical analysis can be done, to show the amount of CO2, and all sorts of other compounds over a long period of time as well

Ice cores provide us with data regarding the atmospheric concentrations of various gases which, when combined with proxy measurements of temperature, provide us with information about the natural warming and cooling cycles that the earth experiences.

We know that the temperature on earth is affected by many different factors, such as solar output, volcanic activity, perturbations in the earth's orbit, and so forth. We also know that temperature affects the transfer rate of CO2 between atmosphere and oceans and vice versa. As the earth warms, more CO2 is released from the oceans into the atmosphere, resulting in additional warming, which releases more CO2, and so on. The exact opposite is the case when the earth cools and oceans retain more CO2, which eventually reduces the concentration in the atmosphere. The process is not symmetric (it has hysteresis) - in other words, the rate at which CO2 is released from the oceans to the atmosphere for a 1 degree rise in temperature is not the same as the rate at which CO2 is absorbed by the oceans from the atmosphere for a 1 degree drop.

So, if we look at the graph in isolation of any other information you can draw a few possible conclusions. Firstly, let's suppose that the warming and cooling are caused by changes in solar output and CO2 has no impact on that temperature. What the graph *might* suggest is that the solar output increases rapidly (hence the quick rise in temperature at the start of the graph) but solar output decreases slowly (hence the long cooling tail). The scientific question I'd then ask is whether fluctuations in solar output generally follow that pattern, or is it more symmetric? The next question I'd ask is about ice. If the planet is cold (at the beginning of the graph) then one might imagine that it corresponds to glaciation and hence there will be a lot of reflective ice. So the fact that we see a very rapid rise in temperature must then mean that this asymmetry of the solar cycle is even more pronounced than the graph suggests! We must see a very fast upping of solar output to thaw that ice, thereby reducing the albedo of the planet, and hence leading to the rapid increase in temperature. The cycle must be very asymmetric. Is there any proof that this is how the sun actually behaves - a massive fast spike in output followed by a slow, gradual reduction? A better explanation for the shape of the graph is that, actually, CO2 is having an effect on the temperature as we thought it might. A small increase in temperature results in more CO2 being released into the atmosphere from the oceans, resulting in the rapid rise in temperature. A small decrease in temperature, and the oceans take longer to absorb that warming CO2, hence the fall in temperature is much slower. I'd argue that the shape of the graph is pretty consistent with the idea that CO2 is impacting temperature, even though the concentrations lag the temperature decrease!

Now, taking the graph at face value, we have a temperature of about -8 degrees at t = 0 and a temperature of +2 degrees, at t = 5000 years later. That's a temperature rise of 10 degrees in 5000 years, or 1 degree in 500 years.

Here's the problem ... if we think about the average temperature of the earth (zero degree anomaly on the graph) is about 15 degrees C (273 + 15 = 288 K), and the lowest temperature is 8 degrees below this (280 K) then we can estimate the percentage change in solar energy required to shift the temperature by using the Stefan-Boltzmann law (the energy radiated from the earth should match the energy arriving on the earth) -

E2 / E1 = 288^4 / 280^4 ~ 112%

In other words, to explain the temperature rise in terms of solar energy, the sun would have to increase its output by about 12%. Let's go the other way to illustrate the point ... let's suppose that the zero degree anomaly represents 273K and the coldest point is 8 degrees lower (265 K). In this case the solar energy change required is -

E2 / E1 = 273^4 / 265^4 = 113% ... so solar energy needs to up by 13% to cause that temperature change!

This is *way* higher than anything we've observed. So it would seem that, actually, CO2 (and probably water vapour as well) must be having a warming effect if we can't explain those temperature fluctuations in terms of realistic changes in solar output.

The graph shows that CO2 concentrations only ever hit a maximum of 300 parts per million in the 35000 year profile. Today, CO2 concentrations are over 410 ppm. That's a pretty good indication that the levels we're seeing are not due to the natural cycling of CO2 between atmosphere and oceans. Furthermore, since we add CO2 to the atmosphere (not the oceans) we'd expect that to have a warming effect based on the relationship hinted at with this graph. The fact that this graph shows a natural lag between warming and CO2 concentration does not imply that increasing CO2 will not impact temperature. In the case of the graph, the temperature is changing, CO2 is responding, having an impact on temperature. This doesn't mean we can't increase CO2 in the atmosphere, and then have temperature follow that ... in the case of the graph, it's a natural cycling due to temperature of CO2 between oceans and atmosphere. In the modern case, it's us adding more CO2 into that system. Two different scenarios. In fact, if there's one thing we can definitely conclude from the graph is that we'd reduce the rate of warming with our CO2 emissions if we dissolved them into the oceans rather than pumping them into the atmosphere!

The Vostok/Greenhouse Ice core samples under scientific analysis shows that CO2 lags temperature it does not lead. It also confirms that there is a 600 - 800 year lag before CO2 levels rise after Earth warming begins.

The Radiative Greenhouse Effect's foundation is based on CO2 being the major cause of global warming and the ice core experiments prove that AGE is a myth.