The Science And Politics Of Climate Change

Lennart Bengtsson:

Since the end of the 19th century, we have known that the Earth’s climate is sensitive to greenhouse gases in the atmosphere. At that time, the Swedish chemist Svante Arrhenius showed that an increase in CO2 concentrations would lead to a warmer climate. However, Arrhenius harbored little hope that this would happen. Consequently, the Swedes would have to continue to suffer in a cold and miserable climate. Since then, much has changed. Annual CO2 emissions have now reached a level that is about 20 times higher than that of 1896. This has caused concern worldwide.

More CO2 in the atmosphere leads undoubtedly to a warming of the earth surface. However, the extent and speed of this warming are still uncertain, because we cannot yet separate well enough the greenhouse effect from other climate influences. Although the radiative forcing by greenhouse gases (including methane, nitrogen oxides and fluorocarbons) has increased by 2.5 watts per square meter since the mid-19th century, observations show only a moderate warming of 0.8 degrees Celsius. Thus, the warming is significantly smaller than predicted by most climate models. In addition, the warming in the last century was not uniform. Phases of manifest warming were followed by periods with no warming at all or even cooling.

The complex and only partially understood relationship between greenhouse gases and global warming leads to a political dilemma. We do not know when to expect a warming of 2 degrees Celsius. The IPCC assumes that the earth will warm up by 1.5 to 4.5 degrees Celcius in response to a doubling of CO2 concentration. These high values of climate sensitivity, however, are not supported by observations. In other words: global warming has not been a serious problem so far if we rely on observations. It is only a problem when we refer to climate simulations by computer models.

There is no alternative to such computer simulations if one wants to predict future developments. However, since there is no way to validate them, the forecasts are more a matter of faith than a fact. The IPCC has published its expert opinion a few months ago and presented it in the form of probabilities. As long as the results cannot be supported by validated models they produce a false impression of reliability.

EU member states pursue a strategy of reducing the climate risk by reducing the use of fossil fuels in the shortest time to a minimum. Many citizens are risk averse and therefore support this policy. In addition, many citizens want to phase-out nuclear power, because it is also seen as too risky. To eliminate both nuclear energy as well as fossil fuels is an enormous challenge. Nevertheless, Germany and Switzerland have opted for such an energy transition. To pursue such a radical and perhaps risky energy policy, despite the limited economic, scientific and technical capabilities of the two countries is an enormous undertaking.

There are two things that need to be addressed in this context. Firstly, such energy transitions will, unfortunately, do little to reduce global CO2 emissions, since 90 percent of these emissions come from countries outside Europe. Many of these countries are likely to increase their CO2 emissions in the future, as their population increases and their top priority is to improve the living standards of their citizens. China is a special case. Its CO2 emissions have more than doubled in the last decade and are now about 50 percent higher than those of the United States. For various reasons, there are no alternatives to fossil fuels in the developing countries for the time being. Energy demand there is great. Currently, 1.3 billion people have no access to electricity. To reduce their own emissions easily and quickly, the OECD countries have outsourced some of their energy-intensive production to developing countries. In the national statistics, this looks good. Globally, however, not much changes, since the emissions occur simply somewhere else.

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