Just when it looked like the climate catastrophists had slunk back into well deserved academic obscurity, a new report in the journal Nature Geoscience has resurrected claims of Earth’s impending climatic demise.
A new computer climate study says to expect increases in temperature of up to 3°C by 2050, confirming or exceed predictions made by the IPCC reports. Can this model based report be considered any more accurate than previous attempts? Have modeling techniques suddenly improved? Or is this report’s appearance in a major scientific journal the signal of a renewed round of scaremongering by eco-alarmists?
In these days of faltering economies and tight government spending there still seems to be an infinite amount of funding available to promote ever larger computer based climate studies. The latest such study, “Broad range of 2050 warming from an observationally constrained large climate model ensemble,” was published online on March 25, 2012. A veritable potpourri of international climate science boffins applied yet another technique to the problem of turning sow’s ear climate model results into a silk purse predictions to help bolster the IPCC’s flagging fortunes. The paper’s abstract explains the work and motivation:
Incomplete understanding of three aspects of the climate system—equilibrium climate sensitivity, rate of ocean heat uptake and historical aerosol forcing—and the physical processes underlying them lead to uncertainties in our assessment of the global-mean temperature evolution in the twenty-first century. Explorations of these uncertainties have so far relied on scaling approaches, large ensembles of simplified climate models1, or small ensembles of complex coupled atmosphere–ocean general circulation models which under-represent uncertainties in key climate system properties derived from independent sources. Here we present results from a multi-thousand-member perturbed-physics ensemble of transient coupled atmosphere–ocean general circulation model simulations. We find that model versions that reproduce observed surface temperature changes over the past 50 years show global-mean temperature increases of 1.4–3 K by 2050, relative to 1961–1990, under a mid-range forcing scenario. This range of warming is broadly consistent with the expert assessment provided by the Intergovernmental Panel on Climate Change Fourth Assessment Report, but extends towards larger warming than observed in ensembles-of-opportunity typically used for climate impact assessments. From our simulations, we conclude that warming by the middle of the twenty-first century that is stronger than earlier estimates is consistent with recent observed temperature changes and a mid-range ‘no mitigation’ scenario for greenhouse-gas emissions.
The new trick that these savants applied to an existing climate model is called a perturbed-physics ensemble. Reportedly, the investigators created a large collection of model results (an ensemble) by “perturbing the physics in the atmosphere, ocean and sulphur cycle components, with transient simulations driven by a set of natural forcing scenarios.” Much like tapping a bell with a hammer and observing the vibrations, they tweaked some of the model’s parameters and watched what happened to the output. The claim is, that by analyzing a large number of these “perturbed” model runs, conclusions can be made regarding the error present in those models. Naturally, given that their results were “broadly consistent” with previous IPCC generated claptrap, the conclusions reached will surprise no one.
