1166. How to Slice a Global Carbon Pie?

Justin Gillis, The New York Times, October 7, 2013

Global greenhouse gas emissions

STOCKHOLM — It was the middle of the night. In a matter of hours, journalists from around the world would be showing up, expecting details about the latest big United Nations climate report. But behind closed doors here, as the final wording of that document was being worked out, things were not going well.

Inside an old brewery converted into a conference center, scientists and diplomats fought off hunger pangs and joked about having their 15th cup of coffee. As the hours dragged by, several countries — with Saudi Arabia and China in the lead — raised one objection after another to a small section of the report. Reto Knutti, a Swiss scientist, spent much of the night in the hot seat, answering questions.

The idea he was defending was that scientists should specify a worldwide cap on global emissions of greenhouse gases — “a carbon cap” — that would apply if countries were serious about staying below an internationally agreed upper limit on global warming. It was just a single paragraph, but it had huge implications, and everyone in the room knew it. If it were adopted, it would make starkly clear how far the world remains from having any meaningful policy to tackle climate change.

“It was inconveniently simple,” Dr. Knutti would say a few days later.

As the questions flew, Dr. Knutti kept a graduate student awake all night at his home institution, the Swiss Federal Institute of Technology in Zurich, running computations. In the end, Dr. Knutti and his scientific colleagues prevailed, thanks in part to an intervention from the United States delegation.

Dr. Knutti is a key member of the Intergovernmental Panel on Climate Change, an international committee of several hundred scientists who issue major reports on the issue every five to six years. The report released in Stockholm on Sept. 27 was their fifth since 1990, each finding greater certainty that the earth is warming and greater likelihood that humans are the cause.

In its draft form, the fought-over paragraph declared that, to have the best chance of not exceeding the international target for global warming of 3.6 degrees Fahrenheit, society can burn no more than about 1 trillion tons of carbon, in the form of fossil fuels, and spew the resulting gases into the atmosphere. More than half that carbon budget has been used already. Moreover, the draft made it clear that if countries want to be safe and take account of other gases that are warming the planet, the carbon budget would be even less than a trillion tons. At the rate things are going, we will exceed the budget in 30 years or fewer.

The political implication of the statement was that far more ambitious efforts to limit the use of fossil fuels had to begin soon. That did not go over well with the Saudis, with their huge oil reserves, nor with countries like China and Brazil that are burning a lot of carbon as they move up the income scale.

The issue was especially sensitive because the countries of the world are in the middle of a big negotiation that is supposed to produce a new global climate treaty by 2015, to take effect in 2020. It is meant to replace the weak Kyoto Protocol, the previous climate treaty.

In essence, the scientists were putting a big carbon pie on the table and asking: How are we going to carve this thing up?

Huge fights could break out as rich countries tussle with poorer countries over who gets the biggest slice. Suppose countries got a piece proportionate to their share of world population. The United States, with less than 5 percent, would get a sliver. And at our current rate of emissions, our budget would be gone not in 30 years but in something like half the time. (Thanks to Kelly Levin at the World Resources Institute for help with the math, and thanks to four people who were in the room in Stockholm and later described the events.)

No American president is going to agree to a deal that would shut down the fossil-fuel industry 15 years from now, of course, much less get such an agreement through Congress. So you can see why the Chinas and Brazils of the world would be nervous. They fear the rich countries will try to muscle them into accepting emission limits that doom their people to lasting poverty.

What was the compromise that finally broke the Stockholm deadlock?

The scientists had wanted to specify a carbon budget that gave the best chance of keeping temperatures at the 3.6 degree target or below. But many countries felt the question was related to risk — and that the issue of how much risk to take was political, not scientific. The American delegation suggested that the scientists lay out a range of probabilities for staying below the 3.6-degree target, not a single budget, and that is what they finally did.

The original budget is in there. But the adopted language gives countries the possibility of a much larger carbon pie, if they are willing to tolerate a greater risk of exceeding the temperature target.

It remains to be seen if the carbon cap will become a major negotiating point when climate diplomats convene for their next big meeting this November in Warsaw. At the very least, the scientists have created a new yardstick by which any future foot-dragging on climate can be measured.

“It’s another way of saying that we are quickly running out of time,” Dr. Knutti said.