Recently we heard news of scientific evidence supporting the existence of large ice sheets during the Turonian era, one of the warmest periods in Earth's history -- much warmer than today's period or the more extreme predictions of the global warming models for the near future. So, are the polar caps in danger of disappearing or not? My answer in this case, as in other instances of the climate change news we are confronted with almost daily, is: we don't know. 

In the early 1990's, when I first heard of the evidence of an increasing global temperature, the topic attracted my attention. I was starting my scientific career. Naturally, I had an interest in many scientific questions and the time to read about them. So, from time to time I went to the library to scan the articles in the recent issues of the journals Nature and Science. I frequently read those that had to do with changes in global temperature. To my surprise, I encountered articles that came to opposite conclusions. For some, global temperatures were rising, for others, decreasing. There was no evident difference in the materials on which the studies were based. They were using ice cores from high latitude regions. My conclusion was: we don't know.

If the global warming theory is proved wrong, citizens will look at science with lack of trust and perhaps with contempt.

These studies are nothing like cutting a piece of ice, taking it into the lab, putting it inside some device and then reading a number on a display. They are based on scientists' assumptions, and decisions that go from the selection of the sampling locations, to the analysis of the data, correction for predictable bias and the interpretation of the numbers. These studies are very complex and there is a lot of room for the personal opinions and decisions of the scientists. This is why similar studies can produce opposite conclusions. As a scientist, this does not surprise me at all and it does not imply anything about the quality of one or the other group of scientists. It is by accumulation of data and discussion that assumptions and interpretations are proved false or correct and a consensus is reached.

This was my state of mind about the global warming issue when I learned that, suddenly, in less than 10 years, the consensus had been reached. By now I had more experience on how complex scientific issues evolve and are clarified, and this looked suspicious. The argument at that point was that carbon emission by human activity is producing an increase of global temperature. I looked at the one essential piece of evidence and found that it does not match the official thesis. Plots of temperature since the end of the nineteenth century show a temperature increase until 1940, a plateau from 1940 to 1980 and then a constant increase. The increase in carbon emissions between 1940 and 1980, however, was approximately 57 per cent of the total increase from 1850 to 2000. How is it that such large increase in emissions failed to produce an increase of the temperature for 40 years? This discrepancy between data and interpretation is enough to cause a scientific paper to be rejected for publication in a peer-reviewed journal. Any ad-hoc explanation would not be enough to prevent rejection. The data are required to stand a quantitative test.

My suspicion about the general consensus was greater because the "truth" of global warming received so much support from political groups. The issue had become a political one and had come out of the exclusive realm of science. Whatever science was there was magnified by a political surge. All sorts of diagrams, models and predictions were being published in all sorts of popular publications. Apparently, as far as we can tell, all is very solid science and the consensus is almost universal. But this is apparent only, because political forces are supporting and funding studies that conclude in favour of the man-made global warming interpretation, whereas they starve and filter those that conclude or might conclude the opposite. 

I do not find the supposed scientific consensus among my colleagues. My field is earth sciences, related to certain aspects of climate change in the geological scale. Approximately 70 per cent of fellow researchers with whom I have discussed the matter think that we do not have sufficient information to be sure about the issue and that the pretended consensus is politically manufactured. The other 30 per cent do believe there is sufficient evidence in favour of the man-made global warming interpretation. My conversations have sampled scientists from Scotland to Gibraltar and from San Francisco to Moscow.

There are two more facts that are clear evidence of politics overriding science in this issue. I had some direct experience, through my work, of the problem of nuclear waste disposal. I can give witness to the reliability and quality of the studies carried out to test the safety of underground repositories. I have always been convinced that there is the knowledge and technology to create these repositories. I have also experienced the opposition of environmental groups and the impossibility of a dialogue on scientific ground with them. Theirs is a political position. They succeeded in delaying the implementation of underground nuclear waste repositories everywhere in Europe. Now, Britain is returning to nuclear energy for the simple reason that climate change, which has become a much more popular "phenomenon", can now be used to convince the public that nuclear power is necessary. Scientific reasons were not the cause of stopping nuclear programmes and they are not the justification for present moves to combat climate change.

The other fact is the designation of Al Gore as the recipient of the Nobel Peace Prize last year. Most recipients of the prize have worked for years to solve human conflicts and some have suffered and given the best part of their lives for the causes they fought. Gore simply made a film and toured the world for a short time while cashing in heavily on a popular theory. This shows that the environmental lobby has become so successful and powerful that they are fearless and ready to take their battle to the most unconvincing extremes. 

This panorama is a distressing one for science. The case for man-made global warming has been made waving the banner of science. There are reasons to believe it is happening and reasons to believe it is not happening. But science has been given an authority that it does not have, as yet, to decide on the matter. Only the future will be able to decide the question. If the global warming theory is proved wrong, citizens will look at science with lack of trust and perhaps with contempt. So much of their lives is being altered on the basis of this "scientific truth". Science may have a darker future if citizens are disappointed about its reliability.

Javier Cuadros is a specialist in earth science. He works in London.