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Basic climate science update: Debunking Don Surber

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See here for information on the graphic.

promo_368_0.jpegWhen I started this blog, I swore to myself I wouldn’t spend too much time and energy debunking the Daily Mail’s columnists and editorial writers on issues like the damage done by mountaintop removal mining or the threat of global climate change.

But alas, sometimes I just can’t help myself … so here goes.

On New Year’s Eve, the DM’s Don Surber declared on his blog that he had discovered The Final Nail in the Global Warming Coffin.  He pointed his readers (and there are an alarming number of them, for his blog at least) to an item in Science Daily:

To assess whether the airborne fraction is indeed increasing, Wolfgang Knorr of the Department of Earth Sciences at the University of Bristol reanalyzed available atmospheric carbon dioxide and emissions data since 1850 and considers the uncertainties in the data.

In contradiction to some recent studies, he finds that the airborne fraction of carbon dioxide has not increased either during the past 150 years or during the most recent five decades.

And then, in an editorial published yesterday, the Daily Mail summarized Knorr’s study this way:

Then there is the contention by Wolfgang Knorr of the Department of Earth Sciences at the University of Bristol in England that carbon dioxide levels in the atmosphere are about where they were 160 years ago.

Ironically, the DM editorial then commented:

Earth science is far more complicated than government officials wish to admit.

What they should have said was, Science is more complicated than we here at the Daily Mail understand.

Here’s why:

Knorr did indeed publish a short paper in Geophysical Research Letters called, “Is the airborne fraction of anthropogenic CO2 emissions increasing?”  Here’s the summary:

Several recent studies have highlighted the possibility that the oceans and terrestrial ecosystems have started loosing part of their ability to sequester a large proportion of the anthropogenic CO2 emissions. This is an important claim, because so far only about 40% of those emissions have stayed in the atmosphere, which has prevented additional climate change. This study re-examines the available atmospheric CO2 and emissions data including their uncertainties. It is shown that with those uncertainties, the trend in the airborne fraction since 1850 has been 0.7 ± 1.4% per decade, i.e. close to and not significantly different from zero. The analysis further shows that the statistical model of a constant airborne fraction agrees best with the available data if emissions from land use change are scaled down to 82% or less of their original estimates. Despite the predictions of coupled climate-carbon cycle models, no trend in the airborne fraction can be found.

So what does that mean? Well, it most definitely does not mean  that Knorr found (as the Daily Mail wrote) that that carbon dioxide levels in the atmosphere are about where they were 160 years ago.

Start with the global carbon cycle, explained in a pretty basic way here by the Woods Hole Research Center.

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You see, not all of the carbon dioxide emissions released by human and other activity go into the atmosphere. Some are sucked up by “sinks” like the oceans.

What Knorr was studying was what share of those emissions go into the atmosphere, versus which share go someplace else, like the oceans. He found that the percentage going into the atmosphere was not increasing … this is quite different from a finding that the emissions of carbon dioxide aren’t increasing or — as the Daily Mail wrongly told its readers — that the percentage of the Earth’s atmosphere that is made up of carbon dioxide isn’t increasing.

As the Real Climate blog pointed out:

Case in point, Knorr (GRL, 2009) is a study about how much of the human emissions are staying the atmosphere (around 40%) and whether that is detectably changing over time. It does not undermine the fact that CO2 is rising. [See graphic at the top of this post] The confusion in the denialosphere is based on a misunderstanding between ‘airborne fraction of CO2 emissions’ (not changing very much) and ‘CO2 fraction in the air’ (changing very rapidly) …

Or as even noted climate science contrarian  Pat Michaels wrote on his blog:

It is not that the total atmospheric burden of CO2 has not been increasing over time, but that of the total CO2 released into the atmosphere each year by human activities, about 45% remains in the atmosphere while the other 55% is taken up by various natural processes—and these percentages have not changed during the past 150 years.

Now, this particular issue is actually part of a more complicated scientific discussion over whether the percentage of carbon dioxide emissions going into the atmosphere is increasing. You can read more about that here and here.

But there’s absolutely no truth to the idea that the study cited by Surber and the Daily Mail shows carbon dioxide levels in the world’s atmosphere haven’t increased. And it’s too bad Surber and the Daily Mail got this so wrong … West Virginians deserve honest information about climate change from their public officials and from the media.