New Scientist Archive

Magazine section: Comment and Analysis 

You can't control the climate

New Scientist vol 179 issue 2413 - 20 September 2003, page 25


Reducing carbon emissions in the hope this will stop global warming is a flawed idea, argues Philip Stott. Better to react to climate change as it happens


IN EUROPE, the story of human-made global warming has become almost as unassailable as the Genesis creation story in parts of the American Bible Belt. It has morphed into a hegemonic myth, such that any scientific research that challenges it is neither reported in the media nor considered by politicians and policy makers. Whatever your opinion on the mechanics and extent of global warming, this is a pity. Not only does repressing critical science make for an ill-informed debate, it can also result in policy decisions founded on uncertain scientific conclusions.

Let me declare my position: I am a mildly left-wing global warming sceptic. For me, the real questions have never been, "Is climate changing?" or "Are humans influencing climate?" Climate always changes, and humans affect climate in many ways, not just through carbon dioxide emissions. I don't believe we will ever be able to manage the climate in a predictable manner by trying to manipulate just one of the enormous number of natural and human factors involved.

My position is reinforced by recent scientific research. Over the past few weeks, a number of studies have emerged that cast doubt on the significance of human-made global warming and the climate models on which the dominant theory is largely based. But don't be surprised if you haven't heard of them.

One of the most important investigates the link between climate change and galactic cosmic rays (GSA Today, vol 13, p 4). Cosmic rays are known to boost cloud formation - and in turn reduce temperatures on Earth - by creating ions that cause water droplets to condense. Geochemist JŠn Veizer of the Ruhr University at Bochum, Germany, and the University of Ottawa in Canada, and Nir Shaviv, an astrophysicist at the Racah Institute of Physics at the Hebrew University of Jerusalem, calculated temperature changes at the Earth's surface by studying oxygen isotopes trapped in rocks formed by ancient marine fossils. They then compared these with variations in cosmic-ray activity, determined by looking at how cosmic rays have affected iron isotopes in meteorites.

Their results suggest that temperature fluctuations over the past 550 million years are more likely to relate to cosmic-ray activity than to CO2. Cosmic rays could account for as much as 75 per cent of climate variations, they argue. By contrast, the researchers found no correlation between temperature variation and the changing patterns of CO2 in the atmosphere.

This research underlines the serious gaps in our knowledge of how CO2 behaves in the atmosphere. It is often taken as read by politicians, the media and much of the scientific community that increased levels of the gas lead directly to higher temperatures. Yet the mechanism is far from understood. This was emphasised by Veizer in a paper in Nature in 2000 (vol 408, p 698), in which he and two colleagues from the University of LiŤge in Belgium illustrated the serious mismatches between CO2 levels and climate variability in the geological record.

Another study, published last month, highlights weaknesses in the "general circulation models", the computer simulations of the Earth's atmosphere that are among the chief tools of modern climate research. In Progress in Physical Geography (vol 27, p 448), Willie Soon and Sallie Baliunas of the Harvard-Smithsonian Center for Astrophysics point out that a number of scientists have already called for better models that more accurately reflect the extremely complicated interactions between atmosphere, ocean, land and ice cover.

Improving them, they argue, will require long-term monitoring of several key factors that affect the climate that are not yet sufficiently understood by climate scientists. These include radiation, magnetised plasma and energetic particles from the sun; the crucial properties of clouds; and variations in the shape of the Earth, which has a significant influence on atmospheric flow and climate.

Soon and Baliunas go on to stress that no general circulation model has successfully simulated the observation that while temperatures at the surface of the Earth have continued to rise, the lower atmosphere has not warmed at all. Yet if CO2 plays the substantial role in climate change the global warming lobby insists it does, this layer should be warming faster than the surface air.

It seems clear, then, that our climate models are very limited, and that we have a long way to go before the observations on which they are based can be used to dictate policy. Though the "global warming myth" has become immensely powerful, the science of climate change remains deeply uncertain. I believe it is vital to acknowledge this uncertainty. Our crucial mistake is in trying to manage the climate in the vain hope that we can predict it. Instead, we should put our resources into adapting economically and socially - especially at a local and regional level - to whatever it throws at us. I am certain of only one thing: the climate will surprise us.

Philip Stott
Philip Stott is professor emeritus of biogeography at the University of London