Using temperature readings from the past 100 years, 1,000 computer simulations and the evidence left in ancient tree rings, Duke University scientists announced yesterday that "the magnitude of future global warming will likely fall well short of current highest predictions." Supported by the National Oceanic and Atmospheric Administration, the Department of Energy and the National Science Foundation...Duke estimates show the chances that the planet's temperature will rise even by 11 degrees is only 5 percent, which falls in line with previous, less-alarming predictions that meteorologists made almost three decades ago...., Scientists Cool Outlook on Global Warming, Jennifer Harper, Washington Times, 4/21, 2006
This from Duke?
Home of English department kooks,
Who want to burn all male-written books?
Must be a fluke.
Luther
1 comment:
That Washington Times story was pretty poorly written. A better presentation with more context is provided by ,this National Geographic story or this Washington Post story:
(1) The basic conclusion of the Duke study is the climate sensitivity is likely to be between 1.5 and 6.2 C [2.7 and 11.2 F]. This is to be compared to the IPCC assumed range of 1.5 to 4.5 C as of the IPCC's last report in 2001. You'll note that in fact the range in the Duke study has the same lower bound and a higher upper bound than the IPCC. So, why is this reported as being a lower prediction? Well, the answer lies in the fact that in the meantime there was a study last year (from the ClimatePrediction.net experiment) that found that by varying the parameters over what was felt to be plausible physical ranges, they could get climate sensitivities as high as 11 C, although the mean was around 3 C. Unfortunately, due to media hype (probably caused in part by a poorly written press release as discussed here), the 11 C figure got more play than it deserved. In reality, many scientists at the time felt that such high climate sensitivities could probably be ruled out on the basis of paleoclimate data (see here), which is good because if the climate sensitivity were that high, we'd probably be pretty much toast no matter what we do. So, what we've had here is media hype going both ways...first the dire prediction was overhyped and now the "it's not going to be so bad" prediction is overhyped (at least by the Washington Times piece).
(2) One can only describe their sentence about "even by 11 degrees" in the Washington Times as amusing. To put that in context, 11 degrees F would be on the high end of what was believed to have been the global temperature change between the last ice age and now. It is hardly small!
(3) The Washington Times article also confuses predictions about future temperature change with estimates of the climate sensitivity. What the paper was on was climate sensitivity...i.e., how much the temperature would change if CO2 levels are doubled. To convert that into a prediction, you need to incorporate a prediction about the future CO2 levels. In particular, if we were to burn through all of the fossil fuels that are available over the next couple hundred years, it is estimated that CO2 levels would increase by a factor of something like 5-10 over pre-industrial levels (with the exact factor in there depending on whether we also use the more exotic sources [I think like tar sands]). Given the logarithmic nature of the climate's reaction to CO2, this means increasing the temperature by 2 to 3 times what the climate sensitivity figure is. In fact, some people think that the best we can hope for now with a lot of effort toward cutting emissions is to try to stop at just a doubling of CO2 levels (although some think we can keep it a little under a doubling).
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