Be worried..."logarithmic" does not mean what some people think it means

There's a straight science article up at WUWT for a change, without any snark.  It's a press release of this new paper (sans reference): McAnena et al (2013) Atlantic cooling associated with a marine biotic crisis during the mid-Cretaceous period, Nature Geoscience: doi:10.1038/ngeo1850.

The research describes how tectonic activity led to changes in the ocean and resulted in massive CO2 fixing by photosynthetic organisms in the seas.  This in turn caused a 5° Celsius drop in the temperature of sea surface waters.  All this took place more than a hundred million years ago, way back in the late Aptian and occurred over a couple of million years.  So the pace of change was a tad slower than the current extinction event.  Here are some excerpts from ScienceDaily.com:

A "cold snap" 116 million years ago triggered a similar marine ecosystem crisis to the ones witnessed in the past as a result of global warming, according to research published in Nature Geoscience....

...Analysing the geochemistry and micropaleontology of a marine sediment core taken from the North Atlantic Ocean, the team show that a global temperature drop of up to 5°C resulted in a major shift in the global carbon cycle over a period of 2.5 million years.

Occurring during a time of high tectonic activity that drove the breaking up of the super-continent Pangaea, the research explains how the opening and widening of new ocean basins around Africa, South America and Europe created additional space where large amounts of atmospheric CO2 was fixed by photosynthetic organisms like marine algae. The dead organisms were then buried in the sediments on the sea bed, producing organic, carbon rich shale in these new basins, locking away the carbon that was previously in the atmosphere.

The result of this massive carbon fixing mechanism was a drop in the levels of atmospheric CO2, reducing the greenhouse effect and lowering global temperature.

This period of global cooling came to an end after about 2 million years following the onset of a period of intense local volcanic activity in the Indian Ocean. Producing huge volumes of volcanic gas, carbon that had been removed from the atmosphere when it was locked away in the shale was replaced with CO2 from Earth's interior, re-instating a greenhouse effect which led to warmer climate and an end to the "cold snap."

Out of the keyboards of deniers

Couldn't help but remark on this comment on WUWT.  Ian W says:

June 17, 2013 at 3:45 am  The result of this massive carbon fixing mechanism was a drop in the levels of atmospheric CO2, reducing the greenhouse effect and lowering global temperature.

Why do these academics continue to claim carbon dioxide must be the cause of every global temperature change? The level of carbon dioxide changes after the change in temperature. The effect of carbon dioxide is logarithmic in any case so large reductions from 1200 to 600ppm would only have the same effect as 600 to 300ppm.

Walking back out of this ‘carbon fixation’ is going to be very difficult for academia.

What a mixed up chappie.  First he says that CO2 levels change after a change in temperature.  Then in the very next sentence he agrees that there is an effect of CO2 on temperature - or at least implies it, saying the effect is logarithmic.

He says a reduction from 1200 ppm to 600 ppm would 'only have the same effect' as 600 to 300 ppm.  Only? Well, not unless he is talking about the degree change.  Does he realise what he has written I wonder?

There would be a big difference in the world if it got five degrees colder (think lots of ice and dry), just as there will be a big difference in a world that is five degrees hotter than now (think lots of heat and wet). Is that what he really wants?

What does Ian think "logarithmic" means?

I almost have the impression that Ian W thinks that logarithmic equals "not much change, not so you'd notice".  If CO2 goes from 300 to 600 ppm and the average global temperature jumps by, say, 3 degrees;  and then CO2 goes from 600 to 1200 ppm and the average global temperature goes up another 3 degrees;  I somehow think Ian W would notice the changes in the world around him.  Just like he would if the average global temperature dropped by three or six degrees and the world got very icy.

I wonder if he will ever figure it out.


PS Ian W's comment is the most 'intelligent' of the lot so far, believe it or not!  They really are a bunch of numbskulls over at WUWT.