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Newsletter 13th April 2007

The uses and limitations of modelling

The current received wisdom on climate change is based on two key assumptions: that the global climate system is sufficiently well understood to be used as the basis of a predictive tool, and that computer modelling can encapsulate this understanding comprehensively enough to be this tool. If either assumption is incorrect, the whole basis of climate change policy is called into question. We have covered some of the unanswered questions on climate science previously, but here are a few thoughts on modelling.

First, one of the interesting games which is often played in the office is to check the weather forecast for Cambridge on the BBC website and see how it relates to observation on the day. The first remarkable thing to note is that the outlook for the day can be very different depending on how the information is viewed. Looking at the 24 hour forecast, we can see the temperature, wind speed and direction and whether it will be cloudy, rainy or sunny. However, tracking cloud, rain or temperature over the same period for the east of England often shows quite a different picture. And sometimes, most confusingly, the view from the window does not fit the forecast for that hour at all.

Now, it is easy to criticise meteorologists, and we know it is particularly difficult to produce accurate local forecasts, especially with the sort of variable climate we enjoy. So we should not be too harsh on them. Nevertheless, the understanding of weather patterns which underpins the computer models used for weather forecasting is the same as that embodied in global climate models.

Perhaps this should be of less concern because global models are used to show trends rather than accurate, year-by-year regional figures. On the other hand, there are a number of models in regular use, and the climate projections which they produce vary over a wide range, with no-one being able to say that one model is better or worse than another. Which really points to a key factor about models: they can be very useful to do “what if” experiments, to see how something might change given different input data, but they say nothing about how realistic such an outcome may be.

A parallel example lies in economic modelling. For the UK, a minor cog in the overall world economy, teams of economists, researchers and statisticians in the Treasury and elsewhere make predictions for how the economy will evolve over the next year (and longer). Every year, we know the predictions will be wrong, but not by how much. Every year, the Treasury has to review real data and correct the growth figures, for example. Of course, different schools of economists will rarely agree about anything but, nevertheless, the workings of a modern economy and its response to particular policies are reasonably well understood.

This seems not to be the case for global climate. Climatologists readily admit that they have an imperfect understanding of the effect of clouds. We know that very significant short-term drivers of climate – El Niño for example – are not understood or readily predictable and therefore do not form part of the models. In these circumstances, is it right for the IPCC to place so much faith in a set of complex algorithms to project future climate and form the basis of far-reaching policies?

The Times gets it right

The first leader in the Times on 7th April (A climate of intolerance) calls for tolerance of dissent. The first few lines say it all:

Few scientists or rational politicians doubt that global warming is a serious issue that poses long-term dangers to the planet. The scientific evidence that the world’s climate has changed and that this change is accelerating is convincing. But it is also beyond doubt that the world is in danger of being held captive by powerful lobby groups that have distorted data, made unjustified extrapolations and attempted to stifle debate on one of the most important issues of our time.

We may disagree with the leader writer on how certain the understanding of climate science is, but we warmly welcome such a call for scientific tolerance. Climate change happens to be one of the defining issues of our time and important in its own right, but what happens in this debate will also set precedents and shape the evolution of quite different areas of science and policy. Everyone who believes in the power of the scientific method should be prepared to take a stand and support informed debate rather than succumb to the calls to toe the line by those people endowed with a greater sense of certainty than is healthy.

All schoolchildren in England to be told Al Gore’s inconvenient truth

Al Gore, now complete with Oscar for the best documentary, continues to promote the cause of man-made climate change across the world. He has been welcomed with open arms by both main political parties in this country (who, incidentally, are continuing their bidding war to capture the green high ground, with the Tory quality of life policy group now pushing for an 80% cut in CO2 emissions by 2050).

One manifestation of this is that, to coincide with the launch of the IPCC working group 1 Summary for Policymakers back in February (the full report is still several weeks away from publication) David Miliband and Alan Johnson announced that all secondary schools in England would receive a copy of “An Inconvenient Truth” as part of the Sustainable Schools programme. Distribution is due to start on 16th April.

Letting people see the film and make up their minds is one thing (and to be encouraged), but surely showing it at school with no attempt to balance the information is a wrong move. Impressionable young people will be given a highly professional but one-sided and flawed version of climate change, and many will regard this a “the truth” (whether inconvenient or not). We think that many parents may also be worried about a precedent for only politically correct views to be taught in areas of great uncertainty.

Resurgence of the salmon

“Against a tide of gloom, the salmon makes a comeback” reads the headline in the Times on 11th April. Not only is this a good news story, which we rarely seem to hear in the environmental area, but the details are equally interesting. This resurgence (14,000 salmon being caught in the Tweed last year, the second best year since 1952) has been due to concerted action by people whose primary concern is fishing. Orri Vigfússon, chairman of the North Atlantic Salmon Fund (NASF), is credited with much of the effectiveness of the campaign, which has seen commercial fishermen bought out, fishing for sand eels cut back, and the use of drift nets stopped.

There seem to be two clear messages here: that Mankind can thoughtfully alter the local environment to encourage particular species, and that the motivation for such action can come from apparently selfish motives rather than the conservation movement. A question of the means justifying the end?