Professor Kevin Anderson:

Most of my focus is typically on the CO2 side. The biogenic methane is a very important issue. Again, it is one of the issues that has been deliberately underplayed by some. Methane is a relatively short-lived gas but it has a huge warming impact, particularly in the nearer term. As the Senator said, if one integrates its impact over 100 years, it looks like 28 times more impact per molecule than CO2, but if one integrates the impact over a shorter period, it looks much higher at 80, 90 or 100 depending on the timeframe. One of the things to bear in mind here is that if we are seeking to just try to stay below 1.5°C , that is going to occur very soon. We are at 1°C warming already. There will be very few years before we head towards 1.5°C. In the timeframe in which we have to deliver 1.5°C, the methane we emit today and in the next two to four years will have a big impact. We have to get the methane out of the system - the biogenic methane and the methane from use of fossil fuels. It is a massively important part of the near-term story, and that near-term story is key if we try to deliver the 1.5°C framing. As I say, it is very challenging, but we should try everything we can.

It is also worth bearing in mind that what we are seeing at global level in the atmosphere are rapid rises in methane emissions. We think there are three principal reasons for this. One is the increased use of natural gas, particularly shale gas. That is one contributing factor. Another is a reduction of the hydroxyl molecule in the atmosphere, which basically cleans up the methane. If there is less of that, the methane lasts a little longer and it appears that more is being emitted. The third one is biogenic activity at global level. As we have warmed up the planet, particularly in the Tropics, we are seeing far more activity, which means we are seeing more methane from those parts of the world. We cannot stop that. Once we have that warming, that is happening. We have to stop the biogenic methane we have control over, and that is principally through agriculture. Biogenic methane is a very important issue. If we are serious about our Paris commitments and if we recognise the atmospheric constraints on methane going up partly because of biogenic methane that we cannot control in some parts of the world because of the warming, then we have to ensure we reduce it from the areas on which we have some purchase - the fossil fuel industry and agriculture.

Regarding some of the negative emissions technologies, the biomass energy with carbon capture and storage, BECCS, is probably one of the worst. Virtually all the models assume biomass energy with carbon capture and storage. They are not looking at some of the more exotic techniques. They are primarily using this type of grunt technology. If one looks at most of the models, it is assumed one plants an area somewhere between the size and three times the size of India, with huge sets of SDG sustainability issues across the board. They could range from water to land rights, indigenous people's rights and the effects on soil. On every level these are problematic at the scale that is assumed in the models. Who is relying on these? It is the wealthy parts of the world relying upon growing this stuff often in poor parts of the world to compensate for our ongoing high emissions from the relatively few people who are producing them in our countries. That is a really problematic approach. It is another sticking plaster for a problem that is much more systemic. While I favour us doing research on some of the negative emissions technologies, and particularly some of the other nature-based solutions, to use those to allow us to carry on our high-carbon lifestyles is utterly inappropriate. The reliance on BECCS is dangerous across an entire set of the SDG commitments.