Sir, David Bellamy has been pushing his anti-global warming barrow around for some time, peddling the same old mistakes (Comment, Oct 22). He apparently understand so little about the issue that he thinks that the “hockey stick” graph that shows a marked increase in global warming since 1900 was generated by a computer (it was actually a summary of measurements and proxy measurements), and he further thinks that it is wrong — whereas it was vindicated not by a bunch of greenies, but by the US National Academy of Sciences.

He is right about one thing — the climate has changed through time and it does contain cycles, as every geologist knows. However, we know enough about these now to realise that what we are seeing today is radically different to anything we have seen before, outside of an ice age; no previous global warming since the Paleocene-Eocene thermal maximum about 55 million years ago was simultaneous in both hemispheres. We can only explain the present warming by calling on some force that has this simultaneous effect, and we can see quite clearly from satellite observations that it is not the Sun. The only climate forces we are left with that we can see and measure and that would have this effect are the greenhouse gases: carbon dioxide and methane. And it is humans who are putting them into the atmosphere. These gases act like a blanket to keep the Earth warm. Increasing the amounts we emit will have the effect of adding another blanket, making us warmer yet.

Colin Summerhayes
Executive Director, Scientific Committee on Antarctic Research, Scott Polar Research Institute

Sir, David Bellamy emphasises the importance of “the questioning rigours of hard science,” then goes on to make the unsubstantiated statement that “James Lovelock, the author and green guru, has changed his mind”. I have just written a biography of Lovelock, which involved many interviews with him over months. I can assure David Bellamy that Professor Lovelock has not changed his mind. He does not believe that either the Earth or the human race is doomed by the present warming, but then, he never did.

His position is that civilisation as we know it is doomed, with a likely crash in human population to about a billion, if no action is taken. This might well make the world a better place to live in a couple of hundred years from now; but it doesn’t mean the transition will be pleasant for those who live through it.

john gribbin

University of Sussex

Sir, Professor Bellamy’s views differ markedly from the vast majority of climate scientists. The IPCC’s 2007 4th Assessment report — which is the most up to date and authoritative review of climate science — makes it clear that it is more convincing than ever before that we are affecting our climate. The IPCC strongly emphasises that substantial climate change is inevitable and highlights the enormous cost of not doing anything.

The science of climate change is incredibly complex and Professor Bellamy’s article will no doubt have confused many. Those wanting to gain a real understanding of where the weight of scientific evidence lies should read the Royal Society’s simple guide, which was compiled with the help of climate scientists, at www.royalsoc.ac.uk/climateguide lord rees of ludlow

President of the Royal Society

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