"The Yale Forum on Climate Change and the Media" har en bra artikel av David Appell om "uppvärmningspausen". Här finns synpunkter från bl a Trenberth, Pielke Sr, Santer och Pierrehumbert, och man tar upp frågor om klimatkänsligheten, om intern variabilitet som ENSO och PDO, om aerosoler, och om havens uppvärmning. Så här börjar den:
Is global warming slowing down?
Is the past 10 to 15 years — which have seen little net change in the average surface temperature of the Earth despite ever-larger carbon dioxide emissions — an indication that climate change will not be as bad as previously projected? That the atmosphere is less sensitive to carbon dioxide than many scientists have concluded based on their understanding of the scientific evidence? That the warnings from those in-the-know are overblown and the world can keep burning fossil fuels?
These questions, percolating for a few months in the blogosphere, came to a head with a recent article in The Economist questioning climate sensitivity — the amount of surface warming expected for a doubling of atmospheric carbon dioxide levels. “The climate may be heating up less in response to greenhouse-gas emissions than was once thought,” read the article’s tagline. “But that does not mean the problem is going away.”
The second half of that conclusion is certainly right. Even if climate sensitivity is somewhat less than the IPCC’s median value of about 3 degrees Celsius, atmospheric carbon dioxide levels are increasing exponentially, so a smaller value merely buys an extra decade or two until the same amount of warming is reached.
But is the climate less sensitive to greenhouse gases like carbon dioxide and methane than has been forecast?