Arbitrary Two Degree Climate Threshold Is Not Backed by Research

(p. A1) Many researchers have argued that a rise in the planet’s average global air temperature of two degrees or more above preindustrial levels would usher in catastrophic climate change. But many others, while convinced the planet is warming, say two degrees is a somewhat arbitrary threshold based on tenuous research, and therefore an impractical spur to policy action.
“It emerged from a political agenda, not a scientific analysis,” said Mark Maslin, professor of climatology at University College London. “It’s not a sensible, rational target because the models give you a range of possibilities, not a single answer.”
Policy makers tend to assume the two-degree target expresses a solid scientific view, but it doesn’t. The exhaustive reports published by the United Nations Intergovernmental Panel on Climate Change are considered to be the most comprehensive analysis of the science of global warming. Yet the two-degree limit isn’t mentioned in a single IPCC report.
. . .
(p. A12) William Nordhaus, a professor of economics at Yale University, appears to have been the first to mention the two-degree figure in a paper published in 1977. But rather than making a robust scientific calculation based on the physics of climate change, his paper argued that a rise of two or more degrees would put the earth’s climate outside the observable range of temperature over the last several hundred thousand years.
. . .
In October 2014, David Victor, a professor of international relations at the University of California, San Diego, and Charles Kennel, a professor at the Scripps Institution of Oceanography in La Jolla, Calif., wrote a sharp critique of the two-degree benchmark in the journal Nature.
They argued that the yardstick was scientifically weak because it captured only a tiny portion of the planet’s climate profile. More than 93% of the extra heat, they noted, ends up in the ocean and not in the atmosphere.

For the full story, see:
GAUTAM NAIK. “Scientists Dispute 2-Degree Model Guiding Climate Talks.” The Wall Street Journal (Mon., Nov. 30, 2015): A1 & A12.
(Note: ellipses added.)
(Note: the online version of the story has the date Nov. 29, 2015, and has the title “Scientists Dispute 2-Degree Model Guiding Climate Talks.”)

The Victor and Kennel critique mentioned above, is:
Victor, David G., and Charles F. Kennel. “Climate Policy: Ditch the 2 °C Warming Goal.” Nature 514, no. 7520 (Oct. 2, 2014): 30-31.

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