Wednesday, January 16, 2013

Carbon and Climate: A Victory of Data over Models

The story of the impact of carbon dioxide (CO2) on climate is widely reported, but the media reports often confuse matters needlessly by referring to CO2 as “carbon”.  In the real world, combustion of both biomass and fossil fuels injects carbon dioxide, water vapor, and incompletely burned carbon (soot, carbon black, or “black carbon”) into the atmosphere.  All three influence the warming and cooling of Earth.  Although the strongest greenhouse effect of these three is due to water vapor, generally the amount added by combustion is dwarfed by the natural background due to the humidity of the atmosphere (although matters would be different if we flew fleets of supersonic aircraft in the naturally dry stratosphere).  Carbon (soot) has long been suspected as a contributor to heat capture by the atmosphere.  Dr. V. Ramanathan at Scripps Institution of Oceanography suggested back in 2008 that, based on observational data, carbon black was almost as important as CO2 in governing heat capture by the atmosphere. Climate modelers generally dismissed his arguments, but the data continue to accumulate-- and now we find in the latest issue of the Journal of Geophysical Research that Dr. Ramanathan was right after all.  In its coverage of this emerging story, the Washington Post comments that “many researchers questioned his analysis because it was based on observations rather than computer modeling”.  And so it was.  How shocking!

The process by which we favor observational evidence over theoretical models has a name: it is called “science”.  We scientists revise our models to conform to observation; it is grossly dishonest to reject observational evidence simply because it fails to conform to current theories.  Let us hope that the results of these observations will soon be evident in improved computer modeling in which the warming effects of carbon are better accounted for and the supposed impact of CO2 on warming is proportionately reduced.  Perhaps the anomalous leveling out of observed global temperatures (observed as opposed to predicted by models) over the last 16 years can be better understood when the effects of soot are properly accounted for.  How important is soot?  The latest estimate is that it is two thirds as important as CO2.  So please, science writers, stop calling CO2 “carbon” and start considering real carbon.  It’s a very big deal.


Anonymous said...

Not finding a good link right now, but the New York Times established a "style and usage guideline" for distinguishing between these forms of carbon, i think 2-3 years ago. I believe the popular press now uses "carbon emissions" to indicate the combined forms of anthropogenic atmospheric and wind-deposited suface carbon, and more specific language ("soot", CO2, etc) to indicate each type of emission. Maybe la year ago the NYT published a very good synopsis of recent studies on each type of emission, including research on the effects of wind-borne soot on rates of ice-melting in the arctic. Wish i weren't doing this on my phone so i cld add some links.

qraal said...

Cleaning up the soot would have a significant impact on global health as well. Millions die from lung-disease caused by fossil-fuel burning and its crud-production. Less than from wood-burning, mind you. Cooking-fires in the poorest communities cause an immense amount of harm too.