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Politics : Foreign Affairs Discussion Group -- Ignore unavailable to you. Want to Upgrade?

To: Nadine Carroll who wrote (260883)	4/7/2008 6:36:37 AM
From: Wharf Rat	Read Replies (2) \| Respond to of 281500

I'd be impressed if Swen was anything but unimpressed. "it would not prove the accuracy of the current climate models. It would only remove one potential reason for their inaccuracy, leaving others." What proves the accuracy of the models is the on-going collection of data. That's not logic, that's science. Measuring the Accuracy of Climate Models An example of a climate model, in this case NOAA's GFDL CM2.1 model. A study by meteorologists from the University of Utah shows that current climate models are indeed quite accurate and a valuable tool for seeking solutions on reversing global warming trends. The study will be published today in the Bulletin of the American Meteorological Society. I expect to see some interesting comments from our readers in regards to this. Co-authors Thomas Reichler and Junsu Kim measured how well climate models actually do their job in simulating climate. They compared the output of about 50 national and international climate models that were developed over the past two decades against observations for present climate. Excerpt from the press release........ "Coupled models are becoming increasingly reliable tools for understanding climate and climate change, and the best models are now capable of simulating present-day climate with accuracy approaching conventional atmospheric observations," said Reichler. "We can now place a much higher level of confidence in model-based projections of climate change than in the past." Other observations from the study...... --Models used for the IPCC (Intergovernmental Panel on Climate Change) paper have reached an unprecedented level of realism. --Climate models built in the U.S. are now some of the best worldwide. (This reminds me of what you typically hear from the American auto industry.) global-warming.accuweather.com == 15 May 2007 Hansen’s 1988 projections... ...In the original 1988 paper, three different scenarios were used A, B, and C. They consisted of hypothesised future concentrations of the main greenhouse gases - CO2, CH4, CFCs etc. together with a few scattered volcanic eruptions. The details varied for each scenario, but the net effect of all the changes was that Scenario A assumed exponential growth in forcings, Scenario B was roughly a linear increase in forcings, and Scenario C was similar to B, but had close to constant forcings from 2000 onwards. Scenario B and C had an 'El Chichon' sized volcanic eruption in 1995. Essentially, a high, middle and low estimate were chosen to bracket the set of possibilities. Hansen specifically stated that he thought the middle scenario (B) the "most plausible".... ...The bottom line? Scenario B is pretty close and certainly well within the error estimates of the real world changes. And if you factor in the 5 to 10% overestimate of the forcings in a simple way, Scenario B would be right in the middle of the observed trends. It is certainly close enough to provide confidence that the model is capable of matching the global mean temperature rise!... Hansen stated that this comparison was not sufficient for a 'precise assessment' of the model simulations and he is of course correct. However, that does not imply that no assessment can be made, or that stated errors in the projections (themselves erroneous) of 100 to 400% can't be challenged. My assessment is that the model results were as consistent with the real world over this period as could possibly be expected and are therefore a useful demonstration of the model's consistency with the real world. Thus when asked whether any climate model forecasts ahead of time have proven accurate, this comes as close as you get. siliconinvestor.com