Only 5 per cent chance of avoiding 'dangerous' warming, study finds

Researchers look out from the Finnish icebreaker MSV Nordica as the sun sets over sea ice floating on the Victoria Strait along the Northwest Passage in the Canadian Arctic Archipelago. Photo / AP

By Chris Mooney

In recent years, it has become increasingly common to frame the climate change problem as a kind of countdown - each year we emit more carbon dioxide, narrowing the window for fixing the problem, but not quite closing it yet.

After all, something could still change. Emissions could still start to plunge precipitously. Maybe next year.

This outlook has allowed, at least for some, for the preservation of a form of climate optimism, in which big changes, someday soon, will still make the difference.

Christiana Figureres, the former head of the United Nations' Framework Convention on Climate Change, recently joined a group of climate scientists and policy wonks to state there are three years left to get emissions moving sharply downward. If, that is, we're holding out hope of limiting the warming of the globe to below 2 degrees C above pre-industrial temperatures, often cited as the threshold where "dangerous" warming begins (although in truth, that's a matter of interpretation).

Last week, a group of climate researchers published research suggesting the climate has been warming for longer than we thought due to human influences. The logic is clear: If the Earth has already warmed more than we thought due to human activities, then there's even less remaining carbon dioxide that we can emit and still avoid 2 degrees of warming.

Two new studies published yesterday, go further towards advancing this pessimistic view which asserts that there's little chance of the world will stay within prescribed climate limits.

The first new study, published in Nature Climate Change, calculates the statistical likelihood of various amounts of warming by the year 2100 based on three trends that matter most for how much carbon we put in the air. Those are the global population, countries' GDP (on a per capita basis), and carbon intensity, or the volume of emissions for a given level of economic activity. The research finds that the median warming is likely to be 3.2C, and further concludes that there's only a 5 per cent chance that the world can hold limiting below 2C and a mere 1 per cent chance that it can be limited below 1.5C. "There is a lot of uncertainty about the future, our analysis does reflect that, but it also does reflect that the more optimistic scenarios that have been used in targets seem quite unlikely to occur," said statistician Adrian Raftery of the University of Washington.

The second new study analyses how much global warming the world has already committed to, since the warming due to some emissions has not yet arrived. Conducted by Thorsten Mauritsen of the Max Planck Institute for Meteorology in Germany and Robert Pincus of the University of Colorado, it finds that it probably pushes us several slivers of a degree beyond where we are now. The upshot is that we may already have firmly committed to 1.5C of warming even if emissions were to stop immediately and entirely.