‘The Planet Could Become Ungovernable’: Climate Scientist James Hansen

...To think for a minute at the scarier end of the spectrum. If we do end up four or five degrees warmer, within a relatively short period of time — that’s the IPCC’s RCP8.5 scenario, by the end of the century, and that’s not counting some of these dramatic feedback mechanisms, what would that do to the planet, in your mind? 

I don’t think we’re going to get four or five degrees this century, because we get a cooling effect from the melting ice. But the biggest effect will be that melting ice. In my opinion that’s the big thing — sea-level rise. Because we have such a large fraction of people on coastlines — more than half of the large cities in the world are on coastlines. 

The economic implications of that, and the migrations and the social effects of migrations — the planet could become practically ungovernable, it seems to me. But if you’re really talking about four or five degrees, that means the tropics and the subtropics are going to be practically uninhabitable. It’s already becoming uncomfortable in the summers in the subtropics — you can’t work outdoors. And agriculture — more than half of the jobs are outdoors.

Food production seems a real worry.

Population is a problem. That’s why you want to have energy that’s needed for people to eliminate poverty, because countries that have become wealthy have the population under control. But if you do begin to lose major cities then the planet becomes ungovernable.

And what level of sea-level rise would precipitate that? What worries you?

Once sea levels go up significantly, you won’t have stable shorelines. Just parts of the city will go under water, but then it doesn’t make sense to continue to build there. So, I don’t know. By the time you get to even one-meter rise, you’re going to be losing more land. We argue in our paper “Ice Melt, Sea Level Rise, and Superstorms,” which we published in 2016, that you could get multi-meter sea-level rise in 50 to 150 years...

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Thanks to Salon.