Riporto qui un articolo appena pubblicato, sperando sia la discussione giusta visto che ce n'erano tre simili ...
"Experts cool on global warming: Weather office cuts temperature predictions by 20% in 'return to humility'
By Joseph Brean
Jan. 9 (National Post) -- Global warming has stalled and will not raise world temperatures over the next five years, according to a new prediction from the British national weather service.
The updated computer model of the planet's climate lowers by about 20% an earlier prediction of how much hotter the coming few years will be than the long-term average since 1971.
The new prediction "does not necessarily tell us anything about long-term predictions of climate change," the Met Office said in a statement, and it is "actively researching potential causes of the recent slowdown in global warming, including natural variability."
"I suspect a lot of modelling groups are going to have to start revising their forecasts down, because most of them are running too hot," said Ross McKitrick, a University of Guelph economist who was instrumental in debunking the famous "hockey stick" graph of rising global temperatures. "There are so many models that are now so far off that it suggests a wider problem with the technique."
Over the next five years, "global average temperature is expected to remain between 0.28 degrees celsius and 0.59 degrees celsius above the long-term (1971-2000) average . with values most likely to be about 0.43 degrees celsius higher than average," reads the new Met Office report. A previous prediction said they would be 0.54 degrees higher.
Likewise, the Met Office's earlier prediction that "about half" of the years 2010 to 2019 will be warmer than 1998 (which was the warmest year since records were kept, at 0.40 degrees above average) is now unlikely under the new model.
"It's like Keynesian economic models in the 1970s that kept predicting high inflation would bring down unemployment,"
Prof. McKitrick said. "Eventually they were so far off reality that it was no longer a case of trying to fine tune bits that didn't fit, economists had to admit the underlying theory was wrong and start over."
Uriel Sinai / Getty Images files Fishing boats sail between icebergs as the sun sets over the Jacobshavn Bay on August 25, 2007 near the town of Ilulissat, Greenland.
Scientists believe that Greenland, with its melting ice caps and disappearing glaciers, is an accurate thermometer of global warming.
The downgraded prediction recalls the 2006 report by the British government that pegged the economic cost of climate change at 20% of global GDP each year "now and forever," but was criticized for relying too heavily on extreme and unlikely outcomes, and is now outdated after the global economic downturn.
"This does not mean that there is no man-made global warming," said Bjorn Lomborg, a Danish academic and author of The Skeptical Environmentalist. "But it does mean that we perhaps should not be quite as scared as some people might have been from the mid '70s to about 2000, when temperatures rose dramatically, because they were probably at least partially rising dramatically because of natural variation, just like they are now stalling because of natural variation."
He called the revised prediction "a return to the humility that we probably should have had right from the start," and a reminder that the climate is harder to predict than scientists once "naively" thought.
"The short-term prediction has always been dodgy. It's really hard to say what's going to happen in five years. Global warming is about what's going to happen in 20 or 50 or 100 years," Mr. Lomborg said.
The public announcement of a minor adjustment to a massively complex computer model also highlights the dangers for scientists of making predictions on controversial matters of public policy.
Andrew Weaver, Canada Research Chair in climate modelling at the University of Victoria, and a B.C. Green Party candidate, called it a "highly uncertain" prediction from the fledgling science of short-term, "decadal" forecasting of the climate, which is an inherently chaotic and unpredictable system.
"Typically, science evolves so that you get better at what you do. But predictions can also change just as a matter of chance," he said.
"Decadal predictability today is kind of what seasonal predictability was 15 years ago. Now we routinely look at El Nino forecasts, we routinely look at seasonal forecasts, and they're very good, but that's because we've been doing them for about 15 or 20 years now. Decadal predictability is only just starting, so it's a bit all over the place. The Met Office actually have changed their prediction . other groups might get still different predictions," Prof. Weaver said.
Bruce Pardy, a professor of environmental law at Queen's University, said such predictions are especially dangerous because the common understanding of climate change remains simplistic on all sides. He cited the impulse to blame Hurricane Sandy on global warming as an example of wrong-headed thinking.
"In an ideal world, the policy that's put in place should not be designed to change what's going to happen in the short term. But the game that everybody is playing is to emphasize short-term things so as to produce pressure in the direction they prefer," he said.
"If the impetus required for a universal, binding, international commitment is to have the sky falling, this [new report] doesn't say the sky is falling, at least not tomorrow.
It doesn't change the idea that the sky might fall, or be in the process of falling, further out. But if what is missing in these international negotiations is a crisis, this doesn't help paint it as a crisis, or at least an immediate crisis," Prof.
Pardy said.
"It all depends upon your policy preference, and frankly a lot of policy preferences exist before the data."
-0- Jan/09/2013 14:19 GMT"
