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Climate

Climate

Models within models

10 Jun 2004

Anyone who worries that physicists are running out of interesting challenges to tackle and important problems to solve should read the two, very different feature articles in this issue. In “Climate change: complexity in action”, Klaus Hasselmann and colleagues write about the challenges of including economic and political dimensions in computer simulations of climate change. It is hard to imagine a physics-based topic that has a greater impact on the world at large. In “Quarks, diquarks and pentaquarks”, Robert Jaffe and Frank Wilczek describe our current understanding of quantum chromodynamics and the strong nuclear force. In this case it is hard to think of many more difficult problems in fundamental physics.

Traditional climate modelling is difficult enough because a whole range of effects in the atmosphere and the oceans have to be taken into account. It typically takes weeks for a state-of-the-art supercomputer to simulate 100 years of climate change with a horizontal resolution of 100 km. But climate change is about much more than solving difficult differential equations – there are crucial social, political and economic influences as well. Some researchers, including a significant number of physicists, have started to look at this “integrated-assessment approach”. The first challenge is to develop climate models that take minutes to run on a laptop. The next challenge is to develop analogous models that work in the social, political and economic arenas – which is not a trivial task – and then integrate all these different models and explore all the possible global-warming scenarios.

Physicists also hope to integrate quantum chromodynamics (QCD) into the larger framework of a so-called theory of everything. Like climate modellers, particle theorists working on QCD require enormous computational resources for their calculations, and even then there are limits to what can be achieved (e.g. the mass of the proton has yet to be calculated from first principles). However, QCD can explain the results of an enormous range of experiments, and has recently been given some new particles – “pentaquarks” – to get its teeth into. Moreover, physicists searching for a theory of everything can take heart from the fact that, unlike researchers working on integrated-assessment models, they already have highly successful theories for the phenomena they are trying to unify.

However, the ultimate challenge for the climate community will be to persuade governments and big business that they need to do something to avoid the potentially disastrous consequences of climate change. The UK’s chief scientific advisor, David King, made headlines recently when he wrote that, in his view, “climate change is the most severe problem that we are facing today – more serious even than the threat of terrorism” (Science 303 176-177). It is too soon to say if the message is getting through, but at least climate scientists now have an unlikely ally in the shape of the climate-change disaster movie The Day After Tomorrow.

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