Dr Joanna Haigh is an atmospheric physicist in the department of Space and Atmospheric Physics at Imperial College, London. Dr Haigh's research interests include the role of the sun in climage change and prediction.

Are humans to blame for the recent sharp rise in temperature?
Some argue that recent increase in temperature is just another natural variability in climate. I think one of the most convincing arguments that it is human induced is the fact that the rate of increase has been so fast, never before over the last thousand years and more has such a fast increase in temperature change be seen in any of the records. Also, if you put all the effects on climate into climate models, the only way you can simulate the recent warming is by including greenhouse gases. In addition, if you analyse the data and try and see how the recent warming could be produced by any known factors, again you can’t explain the recent warming without invoking greenhouse gas increases.

How would you respond to those who accuse scientists of scare-mongering?
I don’t think many atmospheric scientists are trying to prove that there is global warming. Most of us are in the subject just because we enjoy it and we like to understand more about the atmosphere, we like to be able to understand why there’s local and regional and intra-seasonal climate and climate change, and the fact of the greenhouse gases is just another aspect that we can investigate. So I’d be disappointed if I wasn’t allowed to do more atmospheric physics, but I wouldn’t be particularly disappointed if I wasn’t asked to do anything more to do with greenhouse gases.

How can the climate models predict anything if climate is so complex?
In order to represent all the factors that are going on we have to make approximations. Now, some people argue that because essentially it’s a chaotic system we can’t represent it – if we change a small effect over here it might have a huge effect somewhere else and therefore we’re not in a position to do any sort of simulations and we can’t really predict what’s going on at all.

The argument against this is that it’s true if you take a particular example, but if you look at the average properties over a particular region over a period of, say, a month or so, then they’re fairly reproducible. I mean, reproducible not just in terms of the average, but also in terms of the degree of variation. So we know that the average temp in London in April varies over a certain range, and the models are able to produce not only that mean temp, but also the variation. So we think that the models are capable of reproducing mean climate and climate variability.

Why do you think people are sceptical about the IPCC conclusions about human culpability and action we should take?
I think there are several reasons why scientists, politicians and others are sceptical about the IPCC conclusions and indeed trying to prove them to be wrong. The first reason is probably that scientists are naturally argumentative, they always question the accepted truth and this is how the scientific method progresses - this is quite a valid thing to do. But if they’re going to do that they need to take a proper scientific approach to the criticisms and a lot of the work that’s produced is not in reputable scientific journals, it’s not peer reviewed - it’s very difficult to answer these criticisms because they don’t have any sort of formal scientific backup. So while it’s very good scientists should dispute the results, I feel they need to do it in a more objective way.

The second reason is of course a large body of opinion that doesn’t like people telling them what to do and doesn’t like governments organising industries or anything else in a way that’s prescriptive, and perhaps there’s an element of that. But the third, and I think the biggest part of it must be the threat to the economy – in particular US economy – of having to use less greenhouse gases, and the CO2 lobby in the US will use any shred of evidence they can to try and make their position safer.

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