How to talk to a climate skeptic – ‘CO2 doesn’t lead, it lags’


Gristmill – December 27, 2006

This is a very quick post on Gristmill which is a blog dedicated to commentary on ecological issues.  It is a question / answer format and this particular post discusses the objection that, from geological samples, CO2 increases appear to have followed an increase in temperature rather than the temperature increase to occur after the CO2 increases – the current theory of climate change in place today.

The article is a little confusing in that it points out that temperatures did increase first but then appears to make the argument that this doesn’t matter because the warming was caused by the sun and then CO2 got more concentrated and then things got really bad.  Does this prove or disprove the argument?

The comments on this article are very revealing so it is worth your time to click through to the original article just to read the commentary.

These warming periods lasted for 5,000 to 10,000 years (the cooling periods lasted more like 100,000 years!), so for the majority of that time (90% and more), temperature and CO2 rose together. This remarkably detailed archive of climatological evidence clearly allows for CO2 acting as a cause for rising temperatures, while also revealing it can be an effect of them.

The current understanding of those cycles is that changes in orbital parameters (the Milankovich and other cycles) caused greater amounts of summer sunlight to fall in the northern hemisphere. This is a small forcing, but it caused ice to retreat in the north, which changed the albedo. This change — reducing the amount of white, reflective ice surface — led to further warmth, in a feedback effect. Some number of centuries after that process started, CO2 concentrations in the atmosphere began to rise, which amplified the warming trend even further as an additional feedback mechanism.

So it is correct that CO2 did not trigger the warmings….

Read the post and its comments here.

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