Professor Peter Stott:

We have to get emissions down over a period of time. That is the big picture and there is no getting away from it. One can get into very detailed arguments about timing and exactly what we do in which year and what a particular country does in which year but that was not the spirit of my remark. My remark concerned the big picture. That is the context in which one has to view it.

The Deputy referred to the tundra. One of the risks of continued climate change arises from the fact there is methane in the tundra. The methane clathrates right at the bottom of the ocean must also be considered. If one is talking about the more extreme warming rates, there are risks we cannot quantify very precisely. There could be very large releases of methane which could have a significant warming effect.

On the Deputy's question on emissions versus concentrations, the big picture still stands. Emissions and concentrations continue to increase. There are some variations from year to year potentially to do with economic activity and there are probably difficulties with precisely measuring emissions. The big picture is it is certainly the case that emissions and concentrations continue to increase. The only way to stabilise the concentrations is to reduce the emissions.

The Deputy asked about the jet stream and the work of Jennifer Francis. There is some fascinating work being done on trying to unpick the issue of the jet stream, which carries our weather systems and varies. For example, the position of the jet stream was relevant to the sort of weather conditions we had this summer. Exactly how the jet stream is varying and exactly how it might be impacted are subjects of intense scientific debate. So far there is not very strong scientific consensus that there is a very direct link between, for example, the Arctic sea ice decline, which is very clear and absolutely the case, and how that is affecting the jet stream. There have been lots of studies about that and about precisely how the jet stream is changing. What we do know is that the high latitudes are warming up more than the lower latitudes. The Arctic is warming up much more rapidly than the lower latitudes and that is changing the temperature gradient of the surface. We also know about what is happening at the upper atmosphere. Potentially it could be pushing the jet stream further north and potentially weakening it.

Taking account of some of those details does not change the overall message that, broadly speaking, summers are getting warmer and are expected to get warmer and that there will be wetter winters. The day after tomorrow type scenario of a dramatic change towards colder temperatures in Ireland or the UK is not likely. The day after tomorrow scenario is associated with overturning circulation and the currents in the Atlantic Ocean and the idea that the whole system shuts down and potentially cools down temperatures at these latitudes. One might think of it as a risk but I would say it is a low probability that can only be thought of in the context of more extreme levels of climate change. What we need to concentrate on in terms of planning and adaptation are the narratives around warmer summers and wetter winters and then to add the details on to that. In terms of the UK climate predictions, we will do that later this year.