Climate change modellers vindicated
Via Jennifer Marohasy, I found a report on three articles in Science Express that put the closing seal on the most significant issue in the debate about the reality of human-caused climate change: the disagreement between climate models and data from satellites and radiosonde balloons. Now as Real Climate observes “the discrepancy has been mostly resolved – in favour of the models.”
There aren’t many scientifically literate sceptics (that is, people open to being persuaded by evidence, but not yet convinced) left on the global warming issue, and this evidence, along with the continued warming being observed at all levels, should convince most of those who remain. There’s a bit more history over the fold.
The big expert on satellite measurements of climate is John R. Christy of the University of Alabama, who has worked with Roy Spencer. His data, which started in 1979, initially appeared to show a cooling trend in the troposphere. Since satellite data seemed free of many of the errors that affect surface measurements, these results were seized on by global warming â€˜scepticsâ€?.
â€¨However, it was discovered in 1998 that the satellite data had problems of their own, arising from a failure to correct for the gradual decay in their orbits. Correcting for this, and adding more data, the satellite data now showed a slight warming trend, but not as much as the surface data. More data and alternative analysed reduced the discrepancy somewhat, but it remained a problematic issue. Sceptics also pointed to studies of radiosondes carried on weather balloons. These were much patchier, but also failed to match model predictions.
The latest studies correct errors in the procedures used to derive both satellite and radiosonde time trends, largely eliminating the discrepancy. The most conservative estimates of tropospheric warming, those of Christy and Spencer now show warming of 0.12 C per decade, compared to a surface trend of 0.19 C per decade. Other estimates show tropospheric warming equal to or greater than that at the surface, as predicted by the models.
In view of the predictive success of the models, in which climate change is driven by human-caused accumulation of greenhouse gases, and the repeated failure of empirical challenges, it’s hard to see how anyone without strong preconceptions on the topic can reject the conclusion that, in all probability, we are experiencing human-caused climate change. Most of the models predict that the warming is likely to accelerate in the future.