Global Science Report is a weekly feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”
As the earth’s climate sensitivity is perhaps the key factor in what climate lies ahead, we’ll often report on scientific findings that enhance our understanding of this important parameter.
Recall from our previous discussion, that the earth’s “climate sensitivity” is the amount that the average global surface temperature will rise, given a doubling of the concentration of atmospheric carbon dioxide (CO2) from its pre-industrial value. This metric is the key to understanding how much global warming will occur as we continue to burn fossil fuels for energy and emit the resultant CO2 into the atmosphere.
And as we mentioned, the big problem is that scientists don’t know what the true value of the climate sensitivity really is. The U.N.’s Intergovernmental Panel on Climate Change (IPCC) summed up its assessment of the science regarding the value of the climate sensitivity in its 2007 Fourth Assessment Report (AR4) thusly:
It is likely to be in the range 2°C to 4.5°C with a best estimate of about 3.0°C, and is very unlikely to be less than 1.5°C. Values substantially higher than 4.5°C cannot be excluded…
New findings seem to be coming in with some regularity since the publication of the AR4 that the IPCC’s estimate is on the high side of reality. We discussed some of these findings in our publication Addendum: Global Climate Change Impacts in the United States (p.26-27) and more recent ones in a Global Science Report last month.
Now we have another new, lower estimate, to report on.