James Lovelock has said that he expects about 80% of the world's population to be wiped out by 2100.
Lovelock is surely one the most influential scientists today. His extreme views on the impacts of climate change has brought all-important publicity to the issue, and his Gaia hypothesis, first ignored by almost all, then ridiculed by some, has been gradually accumulating support over the years.
Lovelock believes that by 2020 extreme weather will be frequent, and that by 2040, much of Europe will have become a part of the Saharan desert and parts of London will be underwater. Though they sound dramatic, his claims aren't too different from the claims in the IPCC's Fifth Assessment Report (see part II), and indeed have the added benefit of making the severity of our situation inescapably clear.
Lovelock's book 'The Revenge of Gaia' does a good job at explaining his view on climate change, and how we should act in light of it. Firstly, what is 'Gaia'? Gaia is the Earth, its atmosphere and all living organisms on it. The Gaia hypothesis proposes that Gaia forms a single complex system that self-regulates its environment to optimise it for life sustenance, much as our bodies self-regulate themselves to maintain the internal conditions that best enable us to thrive.
The self-regulation mechanisms take the form of negative feedback loops. Take, for example, the following feedback loop that may regulate the Earth's surface temperature: let us say that temperatures increase for whatever reason, warming the ocean surface waters. It is thought that ocean algae produce a chemical substance, called dimethyl sulphide (DMS), that contributes to cloud formation. When the ocean surface waters warm, production of DMS increases, and thus cloud coverage increases. However, since clouds cool the Earth by reflecting incident sunlight back into space, the increased cloud coverage works to reduce temperatures back down again. Thus, temperature can be regulated.
However, a number of positive feedback loops also exist. For example, if the ocean surface water temperatures surpass a certain threshold (and a few degrees can make all the difference), its surface waters become devoid of nutrients. Algae die, and DMS production reduces, decreasing cloud coverage. The decreased cloud coverage allows more sunlight onto Earth, thus increasing temperatures further, exacerbating the problem.
Self-regulation means that temperatures would not normally surpass this threshold, but human carbon dioxide emissions, for example, are leading to a hotter Earth, causing the positive feedback loop to kick in. There are many such positive feedback loops now in play, and it is this that makes Lovelock so concerned about our fate: the Earth is going to get increasingly hot, and the world as we know it is going to undergo some serious changes as a result.
So what does Lovelock suggest we do? According to him, it's far too late to try and save the planet: temperatures will increase, deserts will spread and cities will become submerged by water. According to Lovelock, what we have to do is give up trying to save the planet, and use technology to make the world one in which we can live in: we need to synthesise our own food, air-condition our cities, and, crucially, use nuclear power for energy because renewables just won't cut it.
Lovelock's prognosis may seem dark, but the more I read about what he has to say, the more I can't help but agree that we, as a human race, are in serious danger.