Why the World Is Now Set on (at Least) Two Degrees of Warming

An agreement to aim for less has been taken off the table in Paris.

A man looks at his mobile phone at Le Bourget, France, where UN climate negotiations are being held. (Stephanie Mahe / Reuters)

In Paris this week, a diplomatic dust-up revealed the problems that accompany any discussion of climate change—an issue where we know that bad things will happen not only long before they occur, but also long after we can prevent them.

Negotiators from Europe, India, Saudi Arabia, and several Pacific Island states sparred over this question: How much warming should the world realistically try to avoid?

The origins of this fight go back decades. Even as the world’s scientists overwhelmingly endorse the science behind climate change, governments have struggled to endorse common diplomatic language to address the issue. One of their few points of agreement has been the Copenhagen Accord, a document that emerged from the otherwise unsuccessful climate talks in Denmark five years ago.

At Copenhagen, national governments affirmed what they said was “the scientific view that the increase in global temperature should be below two degrees Celsius.” This limit—that average worldwide temperatures should not rise more than two degrees Celsius—was not chosen because it was necessarily the safest or most preferable path, but because it seemed doable and a good target. Scientists since the early 1990s had been saying that, if the Earth’s temperatures rose more than two degrees on average, the ecological consequences could overwhelm human civilization.

Five years later, that global promise looks unworkable. As The Washington Post reported Monday, an increasing number of climate models say that humanity will need to use “negative-emissions technologies” to prevent two degrees of warming. (“Negative-emissions technologies” are processes that could pull carbon dioxide out of the atmosphere. They don’t really exist at scale yet.) And in June, the International Energy Agency indicated that the world will not hit its target without a fast, enormous upheaval to its energy system.

Indeed, climate researchers estimate that the level of pollution reduction likely to be affirmed in Paris will still bring about three degrees Celsius of warming by 2100.

But two degrees of warming remains dangerous. Recent research from James Hansen, the former NASA scientist who first testified about climate change, has indicated two degrees of warming will be worse than previously thought, and that its attendant changes will kick up cataclysmic “mega-storms” and threaten the northern Atlantic jet stream. And even without a worst-case scenario, the two-degree target will trigger sea-level rise that will wipe out the dozens of small nations in the Pacific Islands.

So these islands arrived at Paris with an audacious proposal: They wanted to limit global warming to 1.5 degrees Celsius. The 39-member Alliance of Small Island States—which includes Pacific nations like Kiribati and Nauru and also countries like Haiti, Saint Lucia, and the Bahamas in the Western Hemisphere—said the Earth must not even rise to two degrees Celsius.

The 1.5 degree target was also advanced by the Climate Vulnerable Forum, a 43-member group that includes not only oceanic nations but also Kenya, Ethiopia, and Vietnam. “Many countries are emphasizing that a two degrees goal is a more feasible target. But 1.5 Celsius is also the right moral decision,” said Saleemul Huq, a Bangladeshi climate researcher who advises the group, in a statement. The Forum also indicated that 106 nations endorsed the 1.5 goal.

And then, in the early days of Paris, the coalition picked up major support. Germany and France, two major emitters, endorsed the target: French President Francois Hollande said 1.5 should be adhered to “if possible,” and the German climate negotiating team said that any agreement should mention the smaller goal.

These moves matched a recent UN study that indicated 1.5 degrees of warming would be preferable to two degrees. (Here’s a PDF link to that report.)

But then, on late Thursday, the dream ended. Saudi Arabia and India pushed to remove all allusion to that study from the document. Climate Home reports that the two countries’s leaders thought 1.5 would require too many adjustments to their fossil-fuel-based economies.

So 1.5 degrees is a no-go. Eric Holthaus of Slate predicts that the climate-vulnerable nations will use the loss to push for more adaptation funding. And scientists were doubtful that 1.5 degrees could be reached, anyway: A recent report estimates that, at current rates of emissions, it will become impossible as soon as 2021.

To me, the kerfuffle indicates some of the more unreal aspects of the climate-change debate. First of all, cutting a reference to a scientific report from a diplomatic document was enough to “kill” an already miraculous goal. The truth of the report, of course, does not change depending on its inclusion, so ultimately ministers only argued over whether it should be thought of. Second, these climate negotiators must go home to a nation that they are now assured will be profoundly changed in 80 years—a reality that, difficult as it is to imagine, they have no choice but to think of, and plan for.