How theories develop
Science progresses by setting up hypotheses and testing them by experiment or observation. Those which are found wanting are replaced by alternatives, or modified in some way and re-tested. That is the theory but, in practice, scientists are also human and become wedded to their pet ideas, even when rational analysis would suggest they may not be valid. This natural human behaviour is compounded when a hypothesis becomes an accepted theory in the eyes of a majority of scientists. Once an apparent consensus has been established, there are all sorts of barriers to those people who may want to criticise it. Pointing out that the emperor has no clothes may not be enough.
Anthropogenic global warming, which has now certainly taken on the mantle of a fully-fledged theory, is an interesting case in point. The basic hypothesis is that carbon dioxide, methane and a few other trace gases with long average residence times in the atmosphere are the primary drivers of a warming trend. This warming – which is what would be expected from a knowledge of the infra-red absorption properties of these gases – is theorised to be magnified by the increase in water vapour content of the atmosphere and release of further carbon dioxide from the oceans as air temperatures rise.
This neat and plausible explanation does not, however, explain the non-linear changes in temperature over the last hundred years or so. The curves of average temperature and CO2 concentration have different shapes. This has been dealt with by assuming that sulphate aerosols and dust from volcanic activity and industry had a cooling effect which, at times, outweighed the forcing by greenhouse gases. This is perfectly plausible, but suffers from the lack of direct information on aerosols during the twentieth century.
A further complication is the relative warming of the upper atmosphere and the Earth’s surface. The AGW hypothesis requires the troposphere to warm relatively more, but measurements from weather balloons and satellites do not show the predicted trend. Some (justifiable) corrections have been made to the satellite data, which bring this closer to the model predictions, but there remains a poor correlation between prediction and measurement. However, this discrepancy has now considered to have been explained, despite the poor agreement.
A similar situation pertains to warming at the poles. AGW theory tells us that the poles should show more warming that the tropics. In the case of the Arctic, this certainly seems to be the case, but the Antarctic (with the exception of the more northerly Antarctic peninsular) is showing little or no warming. Some have tried to explain this as being due to the high elevation of much of the southern continent. Nevertheless, it remains a fact that warming has been much more pronounced in mid to high latitudes in the northern hemisphere (Europe in particular) than in the southern hemisphere. Clearly, the greater expanse of open ocean in southern latitudes would be expected to have an effect, but there seems to be no simple explanation for this regional difference.
Given these various question marks over the mainstream theory of global warming (and others, including a poor understanding of the net effect of clouds), we would expect more credence to be given to possible alternatives until a clearer understanding emerges. In fact, one alternative hypothesis – that it is variations in the sun’s magnetic field which could be the primary driver, via their effect on cloud formation – will be the subject of a major piece of work at CERN (the CLOUD proposal), but this has received little publicity. In the meantime, healthy scepticism should be the norm. A more rigorous, questioning approach to hypotheses should ultimately give us better answers, whichever ideas turn out to be correct.
IPCC Fourth Assessment Report
This week, the IPCC continues its release of the Fourth Assessment Report, launching the report of Working Group II (Impacts, Adaptation and Vulnerability) in Brussels on 6th. Interestingly, although only the Summary for Policymakers will be available on the day, we are promised that the full report will appear on the website within a few days. This is in contrast to the position with the output of Working Group I; the SPM was published at the beginning of February, but the full report is still being edited and is unlikely to see the light of day for a few weeks yet.
The contents of the WG II report are meant to be a closely guarded secret. However, a number of leaks have been made to the press over the last few weeks, generally focussing on some of the more apocalyptic interpretations of what may happen to the world’s climate in the long-term. There has even been a suggestion that the IPCC bureaucracy has toned down the final report, and given insufficient credence to some of the scarier suggestions about loss of Arctic and Antarctic ice.
This is an interesting recent development. The public debate, as far as news media are concerned, seems largely to have moved on from a question of whether or not climate change is predominantly human-induced, to one of whether the IPCC is being too moderate in its pronouncements. This is rather worrying as, unwittingly or not, there could be a tendency to close down constructive discussion on the possible drivers of climate change.
Zero tolerance for GM in organic food?
The European Parliament has voted against a proposal from the Commission for organic food to meet the same standards for adventitious presence of GM material as all other non-GM produce: 0.9%. The counter proposal, supported by the Soil Association and environmentalist groups, is for a 0.1% limit, effectively the limit of detection. In practice, this is likely to be revised upwards when the legislation is finalised: Commissioner Fischer Boel is standing by her original proposal.
0.9% is a figure which seems to be readily achievable using normal agricultural coexistence approaches. If confirmed, it will allow both organic and conventional farmers to carry on their business with little problem. If, however, a figure of 0.1% was to prevail, coexistence would be much more difficult. Organic activists would see this as a way to prevent significant commercialisation of GM crops in Europe, but in practice it would be more likely to affect their own livelihoods.
Cultivation of Bt maize is well established in Spain and is now becoming significant in France, with 30,000 hectares or more being cultivated this year. Demand for higher productivity of both food and non-food crops will put increasing pressure on more extensive organic systems, which are likely to remain a niche activity. The majority of farmers will continue to use the best available agricultural technology. Increasingly, that will include crop biotechnology.
We are pleased to say that our new website is progressing well, and we will soon be able to have much more topical material on-line, updated regularly.