What is not clearly known is what caused the initial temperature rises.

There have been several things that have triggered the 'climate changes' of the past several million years; be it celestial impacts, or volcanic activity, or disruptions of the ocean currents, or the inconsistencies of the Earth's orbit around the Sun. But then, the CO 2 gets involved and pushes the climate system further than the original instigating factor(s). Or as the scientists explain it, the 'CO 2 amplifies the changes'.

The denialists use the fact about the CO 2 trailing temperature consistently as if that proves CO 2 cannot heat the planet. Just as they do with the fact that the Antarctic ice sheet is growing in the central region by a very small amount, they take one kernal from the cob and ignore the rest of the story.[1] It's a tactic that is working quite well for them on unsuspecting people who are not paying attention to news coming from the climate scientists.

We all secretly hope that the skeptics are right. No one wants to see the climate of the earth deteriorate. But it is a very dis-honest and very harmful practice to confuse the issue of the changing climate.

Below is a portion of something that has been circulated widely on the web by the denialists (many shown to be funded by the energy giants) and a leading climatologist's response to it by Dr. Richard Alley:

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-MYTH - Carbon dioxide changes in the atmosphere cause temperature changes on the earth.

-FACT: A report in the journal 'Science' in January of this year showed using information from ice cores with high time resolution that
since the last ice age, every time when the temperature and carbon dioxide levels have shifted, the carbon dioxide change
happened AFTER the temperature change, so that man-made global warming theory has put effect before cause. This shows that reducing carbon dioxide emissions is a futile King Canute exercise! What's more, both water vapor and methane are far more powerful greenhouse gases than carbon dioxide but they are ignored.

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If you keep up with the climate science, you will know that no scientist has ever said that "the only thing that has ever caused a change in the climate is CO 2". That would be a ridiculous statement because many things have an impact on the climate and they are cumulative. It is just that in the past century, the CO 2 has risen exponentially faster than ever before to a level that has not been seen for at least 650,000 years.

Here is Penn. St. University Professor of Geosciences Dr. Richard Alley's response via email to the "Myth - Fact" above:

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...some of the ideas have a germ of truth, but are nonetheless inaccurate representations of what we know. First, the paleoclimatic record is not the main factor in our understanding that rising CO2 leads to rising temperature, all else being equal. The basic physics of that are unavoidable, have been known for over a century, and especially are based on military research from WWII and just after (the hot exhaust from a high-flying bomber makes it a target in war, but must be seen through the “swamp” of CO2 and H2O and other greenhouse gases in the atmosphere; the military thus figured out radiative transfer quite accurately, and those results, combined with the observed rise in CO2, lead to warming; things such as the paleoclimatic record then confirm this result).

It is true that our central estimate has CO2 lagging temperature on glacial-interglacial timescales. This is expected; the pacemaker of the ice ages is in features of Earth’s orbit, these cause changes in many things in the earth system including CO2, and the CO2 amplifies changes.

The observation that southern temperatures have often largely ignored southern sunshine has so far been explained only through the influence of CO2 changes, and is successfully explained that way. The argument advanced in the material you sent: CO2 lags temperature, so CO2 cannot cause temperature change-- seems accurate to some readers, but is really not solid at all. Consider another positive feedback: you overspend your credit card and go into debt, interest payments then accrue forcing you further into debt, and you end up going broke. The cause of the problem is the overspending, interest payments clearly lag debt, but the interest clearly contributes to the growing debt and your bankruptcy. The appended materials apparently would see that interest payments lagged debt and would then argue that interest payments cannot contribute to debt or bankruptcy. Put that way, I hope that the erroneous nature of the argument is clear.

Per molecule at a moment, methane is more potent as a greenhouse gas than CO2. But, methane lasts a few years, CO2 a few centuries (and there is a complex discussion of that; some comes out very quickly, some lasts for millennia...), and CO2 is already much more abundant than methane, so the focus is rightly more on CO2.

Water vapor does matter, but we know of no way to independently change water vapor a lot—put water vapor up, and it is mostly rained out within a week or two. But, warm the air and it picks up more water vapor from the ocean; water vapor is primarily a feedback acting as a “slave” to CO2 and other things. And the statement that these are ignored is just absurd if you read, say, the IPCC WG1 SPM AR4.

Notice that in a sound-bite world, my long explanations require more attention than do your correspondents short, pithy, seemingly accurate ones. It is a tad frustrating.

--Richard Alley

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I cannot add a thing except that the deniers being funded by the energy giants will continue to exploit this fact on those who are not aware, and of course do not want to believe that the climate will continually get worse because of Global Heating (a more precise term than the polite 'Global Warming' that sounds so minuscule).

Don Beck

[I wish to thank Dr. Alley for his time and his expertise on this subject.]

References:

1] The Antarctic Ice Sheet Is Growing?, 1/8/08
 http://sydney.indymedia.org.au/story/antarctic-ice-sheet-growing