Professor Valérie Masson-Delmotte:

There is also the opportunity to use timber in building which is a way for long-lasting storage of CO2. It is not just an issue in terms of farming practices, but also in terms of the link to local supplies for the building sector instead of the use of concrete or other options. We see major progress in this direction in other European countries with multilevel buildings being developed using specific types of wood. It would also be interesting to think not just about the farm level, but also about the ultimate use of the wood at the country level.

I wish to comment on the methane side at the global level.

We compare today the effect of greenhouse gases by looking at how much heat they trap at the top of the atmosphere. We call it the radiative forcing. For the well-mixed greenhouse gases, it is altogether 2.8 W per sq. m approximately, 1.8 W from CO2 and we estimated for methane about 0.5 W for the direct effect and there is also an indirect effect because when methane interacts with atmospheric chemistry it creates near-surface ozone, which is a challenge in the context of air quality. It creates water vapour in the high atmosphere that has a warming effect and then it finally gives way to CO2. The indirect effect is about the same amount, so altogether it is around 1 W per sq. m, which is very significant after the CO2. Recent studies show that the direct effect might have been underestimated. There are a couple of studies in the literature which show that new knowledge on how methane interacts with visible radiation, short-wave radiation, suggests the direct effect to be perhaps 25% greater than previously assessed. That is important, but I am not aware of any specific trade scheme. I have seen very theoretical studies of potential chemical reactions that could interact with methane in the atmosphere but nothing close to a sequestration approach.