“Most” means “more than one-half,” and the IPCC says “very likely” means a probability of between 90 and 99 percent. This claim may have constituted the “settled” science of climate change in 2007, but things have become greatly unsettled since then.
The rise in global surface temperatures as measured by the Climate Research Unit at the University of East Anglia (yes, the “Climategate” folks) is 0.70 degrees Celsius since 1950, or a little over a tenth of a degree per decade. But the most recent refereed science literature argues otherwise.
Soon after the IPCC report, David Thompson and several others (including Climategate’s Phil Jones) published a paper in Nature showing a cold bias in measurement of sea-surface temperatures from the early 1940s through the mid 1960s. Accounting for this drops the rise in temperature to 0.55 degrees Celsius.
At the time of the IPCC report, Canada’s Ross McKitrick and I published a paper in the Journal of Geophysics showing that there was a clear and systematic “non-climatic” warming — from changes in land use and problems with station maintenance — in temperatures measured at weather stations. The bias isn’t all that much when measured globally, but it subtracts another .08 degrees Celsius, leaving 0.47 degrees Celsius.
Earlier this year, Susan Solomon of the National Oceanic and Atmospheric Administration published a bombshell in Science in which she argued that the lack of recent warming was likely due to fluctuations in water vapor way up in the stratosphere — changes that bear no obvious relationship to greenhouse-gas emissions. Given the limited stratospheric data that we have going back to 1980, her finding reduces the remaining trend to 0.41 degrees Celsius.
In 2008, V. Ramanathan of the Scripps Institute of Oceanography summarized the scientific literature on the emissions of black carbon (aka “soot”) and concluded this was responsible for about 25 percent of global warming. Carbon particles are not greenhouse gases. This drops the supposedly greenhouse-gas-caused warming to .31 degrees Celsius — 44 percent of the original 0.70.
Note that it’s not even necessary to bring in variations in the sun in order to ascribe more than half of the warming to non-greenhouse changes.
So, where are the studies refuting these findings? They don’t exist. The EPA is wrong. The IPCC was wrong, too, that it is “very likely” that “most” of the warming since 1950 is from greenhouse-gas changes. The EPA has lost the scientific linchpin of its proposal to regulate our lives.
While the president will surely brandish the El Niño–driven warmth of 2010 as the reason for the EPA to regulate where the Senate can no longer act, the EPA needs to accept that the “settled” science of global warming has shifted tectonically since the last IPCC report.