Wriggle-room shrank this week for those who believe that global warming is not caused by human activity. The latest report from the UN鈥檚 Intergovernmental Panel on Climate Change shows that the world is already changing in line with forecasts from computer models that include greenhouse gases as an integral factor (see As polluters quibble, the poor learn their fate).
Everything from the increasing numbers of glacial lakes to the poleward shifts in the ranges of animals and plants is almost certainly down to global warming. The IPCC also finds that natural variation is 鈥渧ery unlikely鈥� to be the sole cause of such changes. Models that include only natural influences on temperature, such as volcanoes and solar activity, are significantly outperformed by models that also include greenhouse gases.
Why shouldn鈥檛 we take these results at face value? Assuming there is no global scientific conspiracy, the only other occasionally voiced argument is that IPCC scientists have staked so much on greenhouse gases that they are unwilling to brook any alternative. This notion runs so completely counter to what science is about that it is as likely as a global conspiracy.
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Scientific ideas are judged by their ability to explain the natural world, and the best ones win. No amount of polemic or political influence will change that, or make a wrong idea right. Some scientists are challenging our ideas on climate change, which is vital if we are to progress. But to overturn present thinking will need very strong evidence because, as the IPCC states, confidence in the idea that anthropogenic warming is changing our world has never been higher.
