There is another climate conference, this time in in Baku, with much hand-wringing, pleas to do more, everyone will talk, and then go home and continue doing what they are doing. We are frogs in the pot. Further, with Donald Trump as President we can assume the US will do more drilling. It has yet to register with the environmentalists the sun does not always shine and the wind does not always blow, yet our whole society depends on a substantial base load of electricity.

An interesting question discussed by Wong (Nature 632, 713) is how hot can people tolerate? Apparently, the University of Sydney has built a structure to test the limits of human tolerance, and these appear to be surprisingly low. Subjects can eat, work and essentially live inside this chamber from 5 degrees C to 55 degrees C. The upper limit for many people appears to be 34 degrees C. Of course, we can survive higher temperatures, but at a cost. As you overheat, work productivity goes down. An interesting point was the use of a fan. In damp heat, the use of a fan can reduce heart strain up to 38 degrees C, but it increases such heart strain in dry heat. One way to reduce strain is to soak your clothing with water, and it was noted that babies in prams in Sydney were more comfortable if covered with white muslin cloths that were wetted from a spray bottle from time to time. Of course, the effects can differ from different people. I recall being in South Africa in the summer and evening was coming. One of the workers came in and put on a jersey, saying he was feeling a little chilly. The temperature was 35 degrees C, but it was explained he came from the Kalahari, which is a real furnace of a place. However, one of the things you may notice is that in many Western cities, in summer temperatures of 35 degrees C are already reached. The cooking is real.

So what can be done? We know we are going to overshoot the original targets because we already have, but there is an option, at least as advocated by some, ad that is, make up for it with more aggressive carbon capture later. For more details, see Nature 634, pp 299 and 366). What do you think of that? To complicate the issue, enter the economists. Economic models include a “discount rate” that puts a higher value on near costs than long-term future costs, so it makes sense (to economists) to acquire the carbon “debt” now. The problem with that, of course, is that it merely encourages the politicians to do nothing right now and leave it for some time in the future. Lucky citizens of the future.

The problem with such a policy is there is an assumption that greatly enhanced carbon dioxide removal has surplus capacity that can be deployed rapidly. If there is such capacity, why not use it sooner, to make the problem simpler? Buried in this proposal is the assumption that the load of carbon dioxide will not get progressively worse over the time, but we know it will because it is getting worse right now.

There is also the question of whether overshoot can be reversed. Many physical systems do not respond instantly, the best known is trying to change the polarization of a magnet by applying an external current in a coil. At first not much happens, then as the current increases, suddenly it switches relatively rapidly. Think of it as if the tiny magnets inside the iron needed a significant force to make them flip past their neighbours. The phenomenon is called hysteresis, and the climate will have this in spades. Think of sea level rise that arises from excessive heat melting ice sheets. Cooling the air will not do much for sea level rise. The sea merely gets cooler. To reverse the rise, there has to be massive snow deposits in the zones where ice sheets may form again, and that will take a lot of time. Similarly, landscape is not immediately reversed. If you burn down a rain forest, you may be able to grow scrubby weeds quickly, but it would take a very long time to regenerate the rain forest.

So what does the paper conclude? Rather depressingly, more research and modelling, although to be fair they also say we need to reduce emissions as quickly as possible, starting now. As an added piece of depression, they say large scale carbon dioxide removal is the very definition of anthropogenic climate intervention (i.e. geoengineering) which raises questions about what would happen? Sorry, everyone, but we are already doing that with our emissions. We are changing the climate, and we have no real idea to what. We should at least give ourselves a chance to fix it.