Finally, some of the top climate modelers in the world have done a “plausible worst case scenario,” as Dr Richard Betts, Head of Climate Impacts at the Met Office Hadley Centre, put it today in a terrific and terrifying talk (audio here, PPT here).

No, I’m not taking about a simple analysis of what happens if the nation and the world just keep on our current emissions path.  We’ve known that end-of-century catastrophe for a while (see “M.I.T. doubles its 2095 warming projection to 10°F — with 866 ppm and Arctic warming of 20°F“).  I’m talking about running a high emissions scenario (i.e. business as usual) in one of the few global climate models capable of analyzing strong carbon cycle feedbacks.  This is what you get [temperature in degrees Celsius, multiple by 1.8 for Fahrenheit]:

Graphic of chnage in temperature

The key point is that while this warming occurs between 1961-1990 and 2090-2099 for the high-end scenarios without carbon cycle feedbacks, in about 10% of Hadley’s model runs with the feedbacks, it occurs around 2060.  Betts calls that the “plausible worst case scenario.”  It is something the IPCC and the rest of the scientific community should have laid out a long time ago.

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As the Met Office notes here, “In some areas warming could be significantly higher (10 degrees [C = 15F] or more)”:


  • The Arctic could warm by up to 15.2 °C [27.4 °F] for a high-emissions scenario, enhanced by melting of snow and ice causing more of the Sun’s radiation to be absorbed.
  • For Africa, the western and southern regions are expected to experience both large warming (up to 10 °C [18 °F]) and drying.
  • Some land areas could warm by seven degrees [12.6 F] or more.
  • Rainfall could decrease by 20% or more in some areas, although there is a spread in the magnitude of drying. All computer models indicate reductions in rainfall over western and southern Africa, Central America, the Mediterranean and parts of coastal Australia.
  • In other areas, such as India, rainfall could increase by 20% or more. Higher rainfall increases the risk of river flooding.

Large parts of the inland United States would warm by 15°F to 18°F, even worse than the NOAA-led 13-agency impacts report found “Our hellish future: Definitive NOAA-led report on U.S. climate impacts warns of scorching 9 to 11°F warming over most of inland U.S. by 2090 with Kansas above 90°F some 120 days a year — and that isn’t the worst case, it’s business as usual!

Dr Betts added: “Together these impacts will have very large consequences for food security, water availability and health. However, it is possible to avoid these dangerous levels of temperature rise by cutting greenhouse gas emissions. If global emissions peak within the next decade and then decrease rapidly it may be possible to avoid at least half of the four degrees of warming.”

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A DECC spokesman said: “This report illustrates why it is imperative for the world to reach an ambitious climate deal at Copenhagen which keeps the global temperature increase to below two degrees.”

Betts “presented the new findings at a special conference” today.  “4 degrees and beyond at Oxford University, attended by 130 international scientists and policy specialists, is the first to consider the global consequences of climate change beyond 2 °C.”  You can find all the talks here.

The UK Telegraph story is here.  The Guardian story is “Met Office warns of catastrophic global warming in our lifetimes:  Study says 4C rise in temperature could happen by 2060, Increase could threaten water supply of half world population”:

When they ran the models for the most extreme IPCC scenario, they found that a 4C rise could come by 2060 or 2070, depending on the feedbacks. Betts said: “It’s important to stress it’s not a doomsday scenario, we do have time to stop it happening if we cut greenhouse gas emissions soon.” Soaring emissions must peak and start to fall sharply within the next decade to head off a 2C rise, he said. To avoid the 4C scenario, that peak must come by the 2030s.

Again, this is not the likely impact for 2060 if we fail to act aggressively, but it is a plausible worst-case scenario that should invalidate all economic cost-benefit analysis done to date (see “Harvard economist disses most climate cost-benefit analyses“).

Kudos to Betts and the Met Office for this important, uncharacteristically blunt, and long-overdue analysis.

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