At a conference in Paris, almost every country in the world is meeting to forge an agreement that many believe will be the only way to avoid catastrophic climate change. It’s part of a process that started in the early 1990s, when global powers first began to act collectively to limit carbon emissions. Indeed, many countries now use 1990 as the benchmark from which they measure future emission cuts.
The ultimate goal of the conference, known as COP21, is to limit warming to less than 2°C above pre-industrial temperatures. The carbon that can be emitted without pushing temperatures above that level is a moving target: cutting less now, for example, means cutting more in the future.
In the interactive below, we’ve highlighted the level of annual emissions that the world needs to reach by 2030 to have even a 50% chance of keeping temperatures within the desired range. See which countries are expected to contribute the most to global emissions between now and then:
The 2030 target level of annual emissions is 36 billion metric tons of carbon dioxide equivalent. Last year, global emissions were 52.7 billion metric tons CO2e, according to the United Nations. So why don’t the negotiators in Paris simply set thresholds for countries, specifying what each must do to play their part: something like a carbon quota?
“You’ve asked the 64-million dollar question, which is how should you divide up the total carbon emissions to get to a 2 degree world?” says Bob Ward, whose team at the London School of Economics did the work of mapping how country-level targets for emission cuts—dubbed Intended Nationally Determined Contributions, or INDCs—would affect future emissions.
Knowing what has to be done isn’t the issue, he explained. The problem is how to share the burden between countries that want to grow, like India and China; countries that have already done most of their growing, like many in the West; and countries that unfairly bear the brunt of climate change—often the world’s poorest and most isolated.
By the end of this year, meanwhile, scientists predict that global temperatures will have risen by 1°C—halfway to the hoped-for threshold. Some believe that we are already too far down the warming path to keep temperatures below the 2°C increase.
The International Energy Agency has modeled three scenarios for how emissions might evolve in the coming decades. One is consistent with a 2°C limit. It’s not the one on the table in Paris.