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| A coal-fired steel factory in Hebei, China. Groups at the climate conference in France say that to achieve a goal of limiting the increase in global temperatures, politicians of the future will have to do a lot more on emissions. Credit Kevin Frayer/Getty Images |
LE BOURGET, France — In the climate deal being put together here, every country gets to decide for itself how ambitious to be about cutting emissions, and how to put its goals into writing.
That means there is no standardization in the national pledges, and adding them all up to see exactly what they might accomplish is no small trick. Still, lots of think tanks have been working at it for weeks, and they have said how much they expect the deal to do for the climate if it is finalized.
The problem is that they do not agree.
Climate Interactive, an American group with ties to the Massachusetts Institute of Technology, projects that by the end of the century, the deal would allow the planet to warm about 3.5 degrees Celsius (6.3 Fahrenheit) above the level that prevailed before the Industrial Revolution. That is an exceedingly worrisome number that would mean an extensive melting of the polar ice caps and a large rise in sea levels.
A coalition of European think tanks, operating under the name Climate Action Tracker, projects an increase of 2.7 degrees Celsius (4.9 Fahrenheit) under the deal — still pretty worrisome, but closer to the two degrees Celsius (3.6 Fahrenheit) that countries agreed five years ago would be a climatological red line.
Not surprisingly, the people running the climate conference like the lower number.
In carefully calibrated language, they have said that countries are doing enough at this conference, although they acknowledge that achieving their goals would require further action in coming years.
But if the more pessimistic forecasts are correct, one implication is that climate negotiators might be overestimating how much they have achieved.
What, exactly, is behind the so-called war of the temperatures?
The computer models that the groups are using incorporate pretty similar calculations on how sensitive the climate is to greenhouse gases. On the basic arithmetic of adding up the emissions reductions incorporated into the Paris pledges, the groups get fairly similar numbers.
Other factors are at work, as Kelly Levin and Taryn Fransen of the World Resources Institute explained on the organization’s website. Among the biggest issues dividing the groups are the assumptions they make about what will happen after 2030.
The groups getting low numbers assume that if emissions are falling in 2030 at the rate countries have promised, then that means a sweeping transformation of the energy system will be underway — and emissions will keep falling.
“We have made a call that we want to inform the people here, and the public, of what would be the consequences if this level of effort would be continued,” said Michiel Schaeffer, science director of Climate Analytics, one of the groups involved in the Climate Action Tracker analysis.
That may sound reasonable enough. But recently, experts have been warning about potential dead ends that could cause emissions reductions to stall in the 2030s.
One example would be a decision by the United States to rely too heavily on natural gas to meet its near-term emissions goals. The country might build a lot of gas power plants and pipelines that would still be in use 15 years from now, and which would then be hard to shut down in favor of cleaner technologies.
Groups like Climate Interactive do not want to assume as much about what will happen after 2030. They point out that if emissions are really going to keep falling after that, it will be a result of hard political decisions that have yet to be made. Some of those include costly investments, like improvements in electric cars — or the needed technologies might not be in place by the 2030s.
“It is dangerous for our leaders to count on emissions cuts that have not been pledged as if they will somehow occur automatically when those cuts require tough negotiations, greater funding and technology transfer for developing nations, and big changes in public opinion,” said John D. Sterman, a professor of management at M.I.T. and one of the brains behind Climate Interactive. “Our leaders must not sugar coat the challenge we face just to paint Paris as a success.”
In the war of the temperatures, it turns out the groups have reached a cease-fire.
They have looked at each others’ work and come to a clear understanding of the factors dividing them. They have basically agreed to disagree about what should be reported as the most likely temperature consequence of the Paris deal.
They all agree about one thing, however: They say the deal coming together here is inadequate.
To meet the global community’s stated goal of limiting the temperature increase, the politicians of the future will have to do a lot more on emissions than the ones who turned up in Paris early this week to take credit for helping to save the planet, the groups have said.
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