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The Economist on Climate Change
It seems a basically sound piece of writing and I have no general comments or observations. But one passage did strike me and prompts this post:
The establishment of an Intergovernmental Panel on Climate Change under the auspices of the UN was designed to silence the arguments and give policymakers an agreed line on what the future holds. But given how little is known about either the climate's sensitivity to greenhouse-gas emissions or about future emissions levels, that proved difficult. Not surprisingly, the IPCC's latest report, published in 2001, offers a wide range of predicted temperature rises, from 1.40C to 5.80C by the end of this century.
This huge range limits the usefulness of the IPCC's findings to
My problem with this passage is that it makes the very common mistake of equating the uncertainty about climate sensitivity with the uncertainty about emission levels through the coming century. The former is a property of the climate system, beyond our control and with a value that is independent of our influence or understanding of it. The latter is a property of our own behaviour and as such is entirely in our control (in theory, at least, even though the reality of collective behaviour brings quite a few practical limits).
The reason for the error ranges around model runs using a given scenario is due to incomplete understanding of the complex ocean-atmosphere climate system. The reason for the range of greenhouse gas concentrations in the various IPCC scenarios is not to express how unknown the future is, but to provide a guide so that we may choose, to whatever extent possible, what those future emission levels will be.
Therefore I think the conclusion in the cited quote is completely wrong. Decision making is in fact facilitated by having a range of possible outcomes from which to determine a goal and a set of actions.