If the planet warms by 4 °C , it will change beyond all recognition. A radical new world order may be our only hope, says Gaia Vince in a review of different studies and projections.
Four degrees may not sound like much - after all, it is less than a typical temperature change between night and day. It might sound quite pleasant, like moving to Florida from Boston, say, or retiring from the UK to southern Spain. An average warming of the entire globe by 4 °C is a very different matter, however, and would render the planet unrecognisable from anything humans have ever experienced...
A key factor in how well we deal with a warmer world is how much time we have to adapt. When, and if, we get this hot depends not only on how much greenhouse gas we pump into the atmosphere and how quickly, but how sensitive the world's climate is to these gases. It also depends whether "tipping points" are reached, in which climate feedback mechanisms rapidly speed warming. According to models, we could cook the planet by 4 °C by 2100. Some scientists fear that we may get there as soon as 2050.
[..if only a fraction of the planet will be habitable, how will our vast population survive? Some, like Lovelock, are less than optimistic. "Humans are in a pretty difficult position and I don't think they are clever enough to handle what's ahead. I think they'll survive as a species all right, but the cull during this century is going to be huge," he says. "The number remaining at the end of the century will probably be a billion or less."