The impact of climate change on our weather conditions

Every day we are discussing the relationship between our increasingly strange weather patterns and the role of climate change. Nick Butler provides a thoughtful blog in the Financial Times, reviewing a recent study from the National Academy of Sciences.


Climate, weather and the politics of energy

Is climate change the cause of extreme weather events? Until now the link has been suspected but never confirmed with scientific confidence. That position is now changing. A new study from the US confirms that for some extreme events there is a causal connection.

This link between climate science and immediate weather conditions can only strengthen the case of those arguing for policy change. The impact of a damaging heatwave in terms of deaths, sickness and other social and economic costs is much more likely to rouse public opinion than the distant prospect of what might to some sound like a modest increase in the global mean temperature. All politics are local, and they are also immediate. The discount rate applied to future possibilities is very high: what could happen to a future generation decades matters much less than what is happening to me here and now. It brings climate to the foreground and diminishes the argument of those who say that since we don’t know everything we should do nothing and wait until we see how things turn out. If the impact is immediate and people are dying as a result, the call for action will be loud.

One of the most dangerous illusions in the debate around the implications of climate change is the notion that the impact will only be material when the carbon concentration in the atmosphere exceeds some defined limit — usually quoted as 450ppm. At that point global mean temperatures will rise by an average of 2 degrees centigrade and the problems will begin. I do appreciate that the science is much more complicated but I think this is how the challenge is seen by many non-expert policy makers and politicians.

That view is mistaken. It implies an accuracy in the knowledge of the relationship between carbon concentration and the effect on temperatures that doesn’t yet exist — not least because, as Martin Rees, the former President of the Royal Society puts it, we are conducting an experiment with the earth’s atmosphere which has never been tried before. We don’t know with any degree of certainty that 450ppm will produce an average rise of 2 degrees and we don’t know what the variations around that average figure might be across the world. The case for action is driven by the precautionary principle. But there is another known unknown and that is the extent and nature of the impact in the shorter term — before we get to 450ppm.

A new and important study from the National Academy of Sciences in the US focuses on the impact of climate change and weather conditions and explores the vexed question of event attribution. Can we say that a heatwave in Paris — as occurred in the summer of 2003 killing some 3,000 people, and again last year, killing another 700 or floods on the Somerset levels in southwest England as in the winter of 2013/14 are the direct consequence of climate change? Did the wildfires that swept western Russia in the summer of 2010 killing some 56,000 people, according to the independent estimate of the insurance company result from global warming?

Until now, the careful scientific answer has been that there may be a linkage but it cannot be proved. Now, however, the science of event attribution is changing that position. It is beginning to be possible to say that some weather events are directly linked and attributable to climate change. Events such as heatwaves fall within that category. For the moment, cyclones do not and nor do droughts because too many other factors are involved.

In the view of the authors of the NAS study, to justify attribution requires:

  • a long-term historical track record of data to set the context of any current event
  • the ability to simulate the events accurately in climate models.
  • a position purely influenced by meterological data.
  • that there is an understood and robustly simulated physical mechanism that relates a given class of extreme events to long-term anthropogenic climate changes such as global-scale temperature increase or increases in water content of a warmer atmosphere

For heatwaves these standards can be met.

In areas where the standards cannot yet be met more work needs to be done — separating out the different factors involved in producing particular circumstances and showing what if any proportion of the outcome is due to climate change.

This is an important advance. We may not yet be at the point of being able to predict the frequency of extreme weather events — that is, we cannot say that there is likely to be a heatwave in Paris at least once every five years but we are close to being able to say that heatwaves are much more frequent than they have been in the past and that the change in frequency is due to a change in the climate.

As this linkage becomes more obvious the public demand for action will grow more intense and that in turn will raise a serious political problem. Even politicians who fully accept the risks of climate change cannot change the weather because heatwaves and other current extreme weather conditions are being caused by the change that has already occurred. Cutting carbon emissions to zero immediately — even if that were practical — would not alter the situation although it could, of course, prevent further deterioration. Equally, countries cannot not isolate themselves. The weather does not recognise political boundaries. In such circumstances the only viable response is adaptation and the development of provision to cope with the increased risks. The approach is sensible but it can be expensive. Taking precautions against the risks of a heatwave is not a simple process.

In politics, if a risk cannot easily be removed or managed the temptation is to look for someone to blame. In legal terms this will be translated into the concept of liabilities. If you are a shareholder in an energy business you might like to ask your company’s view of the issue. It would be fascinating to read their responses.

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