The Copenhagen Conference has been the latest round in a clash of antlers between two extreme positions. On one side, most climate scientists and governments have taken an alarmist view of global warming and have urged that we "must do something", emissions reduction being the only alternative offered. On the other hand, an array of sceptics have tried to cast doubt on everything from the warming trends to the economics, suggesting we relax about "natural" variation and hope for the best. Neither side is right. There is substantial global warming which threatens serious consequences within a few decades. It is time to think about precautions. However, emissions reductions are largely ineffective. We need to think laterally and begin research on global cooling methods that might actually work.

Firstly, climate change is a reality: in simple terms, it became hot in the 1990s and it has stayed hot. There is no prospect of cherrypicking a few years to find any recent cooling trends. The recent Copenhagen Diagnosis document by some of the climate scientists associated with the Intergovernmental Panel on Climate Change gives a good survey of the recent observational evidence. Recent years have been very warm (measured by an array of different methods), there has been melting of glaciers and tundras, and that’s in a La Niña phase, which is normally cooler. The Arctic is warming faster than the rest of the world. It has a serious problem and is enough in itself to cause serious sea level rises in a few decades. The "Climategate" emails affair was a storm in a teacup that made no real difference to the observational evidence: it was interesting to see the sausage-making back of house in science, but there was nothing there that made any real difference to the existing evidence.

The fact that it has become hot is a reason for thinking that it may stay hot. That is so irrespective of whether the causes are known or any models are credible. There is something to worry about and precautions are in order, since it is very difficult to reverse effects such as rising seas.

The understanding of the causes of warming is much less than one would wish. Certainly, it is no use talking about "natural variation" as if that is a reason not to worry. "Natural" does not mean "causeless": if temperature increased, something caused it. But working out the causes in very complex systems such as the climate is always very much harder than knowing the observational facts. The theory that burning of fossil fuels is the main cause of global warming is reasonable enough on all the evidence, but is far from definitively established. There are uncertainties both in establishing that carbon dioxide is the main cause of warming and that the rise in carbon dioxide is mainly caused by burning fossil fuels. The uncertainties are dealt with in more detail in my book What Science Knows, but a short list of the major uncertainties includes: water vapour multipliers, cloud formation, soil carbon, aerosols and paleoclimate. It is true that there is no serious alternative theory on why it has become hot. That does support the fossil fuel theory, but only up to a point – Ptolemaic astronomy enjoyed success while there was no alternative theory, but only through lack of human ingenuity in thinking of one.

So what should we do? Emissions trading schemes are nearly useless. As the leading climate scientist James Hansen says, they are merely selling indulgences and are unlikely to reduce emissions much. Economists have many reasons for doubting if such an artificial market created solely by government regulations will have any effect at all except to distribute corruption and large consultancy fees. Even if those markets did work, any reduction of emissions likely to be achieved will have a very marginal effect on climate. If the sceptics are right, no effect, and if the climate scientists are right, very little.

We need something more serious, that is, well-funded research into effective methods of cooling the planet down. There is an urgent need for an International Panel on Climate Mitigation, to investigate the scientific credentials of all cooling methods, from emissions reduction to wave power to geoengineering methods like shadecloth in space. Then we can see where we should be putting our effort and we will be ready if we need to be.

James' Franklin's book, What Science Knows: And How It Knows It is published by Encounter Books