Sunday, July 21, 2013

Climate Change - 2 b 2 or not 2 b 2 (deg C)


From Mr. Lalloobhoy Battliwala

A piece from the Economist, leaked from second order draft of IPCC AR5 WG III (which deals with "mitigation", not physical science per se). Followed by a note from WG III secretariat cautioning that it's seven months to publication.

How much of the actual, observed GMST increase is or will be natural v. anthropogenic, nobody says and nobody asks. One of the many confusions or frauds about climate change politics. (My take: it doesn't matter. Human sensitivity to climate is far more important, at every point in time, than climate sensitivity to carbon.)
So, will the 2x of carbon lead to an increase of 2 degree C or not? 

Is it 2 b 2 or not 2 b 2?

Do-be-do-be-do. (Combining Krishna - do the right thing - and Buddha - be aware in order to be).

The climate may be heating up less in response to greenhouse-gas emissions than was once thought. But that does not mean the problem is going away.

Select paragraphs from the article...

OVER the past 15 years air temperatures at the Earth’s surface have been flat while greenhouse-gas emissions have continued to soar. The world added roughly 100 billion tonnes of carbon to the atmosphere between 2000 and 2010. That is about a quarter of all the CO₂ put there by humanity since 1750. And yet, as James Hansen, the head of NASA’s Goddard Institute for Space Studies, observes, “the five-year mean global temperature has been flat for a decade.” 

The Intergovernmental Panel on Climate Change (IPCC), which embodies the mainstream of climate science, reckons the answer is about 3°C, plus or minus a degree or so. In its most recent assessment (in 2007), it wrote that “the equilibrium climate sensitivity…is likely to be in the range 2°C to 4.5°C with a best estimate of about 3°C and is very unlikely to be less than 1.5°C. Values higher than 4.5°C cannot be excluded.” The IPCC’s next assessment is due in September. A draft version was recently leaked. It gave the same range of likely outcomes and added an upper limit of sensitivity of 6°C to 7°C.

A rise of around 3°C could be extremely damaging. The IPCC’s earlier assessment said such a rise could mean that more areas would be affected by drought; that up to 30% of species could be at greater risk of extinction; that most corals would face significant biodiversity losses; and that there would be likely increases of intense tropical cyclones and much higher sea levels.
New Model Arm.

The IPCC’s estimates of climate sensitivity are based partly on GCMs. Because these reflect scientists’ understanding of how the climate works, and that understanding has not changed much, the models have not changed either and do not reflect the recent hiatus in rising temperatures. In contrast, the Norwegian study was based on an energy-balance model. So were earlier influential ones by Reto Knutti of the Institute for Atmospheric and Climate Science in Zurich; by Piers Forster of the University of Leeds and Jonathan Gregory of the University of Reading; by Natalia Andronova and Michael Schlesinger, both of the University of Illinois; and by Magne Aldrin of the Norwegian Computing Centre (who is also a co-author of the new Norwegian study). All these found lower climate sensitivities. The paper by Drs Forster and Gregory found a central estimate of 1.6°C for equilibrium sensitivity, with a 95% likelihood of a 1.0-4.1°C range. That by Dr Aldrin and others found a 90% likelihood of a 1.2-3.5°C range.

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