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.