Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”
Our last post was a brief run-through of some items of interest from the recent scientific literature that buck the popular alarmist meme that human-caused climate change is always “worse than we thought.” But as we said in that post, finding coverage of such results in the dinosaur media is a fool’s errand. Instead, it thrives on “worse than we thought” stories, despite their becoming a detriment to science itself.
Not to disappoint, headlines from the first major climate change story of the new year claim “Climate change models underestimate likely temperature rise, report shows,” and it’s clearly Worse Than We Thought. In its January 5 (Sunday) paper, the editorial board of the Washington Post points to the new results as a call for action on climate change.
The trumpeted results appear in a paper published in the January 2nd 2014 issue of Nature magazine by a team led by University of New South Wales professor Steven Sherwood and colleagues which claims that the earth’s equilibrium climate sensitivity—how much the global average surface temperature will rise as a result of a doubling of the atmospheric carbon dioxide content—is being underestimated by most climate models. Sherwood’s team finds “a most likely climate sensitivity of about 4°C, with a lower limit of about 3°C.”
Sherwood’s most likely value of 4°C is about twice the value arrived at by a rather largish collection of other research published during the past 2-3 years and lies very close to the top of the likely range (1.5°C to 4.5°C) given in the new report from the U.N.’s Intergovernmental Panel on Climate Change (IPCC).
While there are a host of reasons as to why our understanding of the true value of the climate sensitivity is little better constrained now that it was some 20+ years ago (it was given as 1.5°C to 4.5°C in the IPCC’s first report issued, almost a quarter-century ago), it is widely recognized that our understanding of the role of clouds in a changing climate is central to the issue.
In describing the why climate models have such different climate sensitivity values, the IPCC writes, in the 2013 edition of it’s science compendium,
Sherwood and colleague set out to see if they could help nail down the specific cloud processes involved in the model spread and to see if recent observations could help better understand which models were handling processes related to cloud behavior better than others.