“The main message is that when we continue with the existing coal fired power plants, and build the new ones, we are closing the door to the 2 degree target,” Edenhofer said. The research was published in Environmental Research Letters, with co-authors from the Potsdam Institute for Climate Impact Research and the Technical University of Berlin.

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The study is based on a concept of “lock-in” or “committed” emissions: Once a coal plant is completed and put into service, the thinking goes, it’s likely to operate for long time to justify the cost of the investment.

And based on an analysis of global coal plans, the research finds that five countries — India, China, Turkey, Vietnam and Indonesia — are home to “nearly three quarters (73 percent) of the global coal-fired capacity that is currently under construction or planned.” Vietnam, if plans are carried forward, could see 948 percent growth in coal emissions, the research asserts, by 2030.

But even as this is happening, the study notes that we have only about 700 billion tons of carbon dioxide that can still be emitted, after the year 2016, to preserve good odds of holding the temperature increase below two degrees Celsius. Existing coal plants and other infrastructure are capable of consuming 500 billion tons on their own, assuming we use them until they are worn out.

New coal plants that are underway or planned, meanwhile, could consume another 150 billion tons, the research finds, during their lifetimes. That pretty much accounts for the two degrees Celsius budget right there.

Here’s a figure from the study showing these calculations:


Edenhofer et al., <a href="http://iopscience.iop.org/article/10.1088/1748-9326/aaa3a2/meta">Environmental Research Letters</a>, 2018.

And if we want to hold warming to just 1.5 degrees Celsius … well. The numbers suggest there’s not much chance of that happening, even with the existing infrastructure alone.

“There is a real risk that the inertia of fossil fuel infrastructure will drag us past where we want to be,” said Steven Davis, an energy researcher at the University of California at Irvine, in a comment on the study.

“However, the retirement of power plants is ultimately an economic decision, and one that gets easier as non-fossil energy sources get cheaper,” Davis added. “And of all coal plants proposed in recent years, only about half have historically been built, and that fraction has been trending down in key places like China and India.”

That highlights the key challenge with the study — it’s one thing to say that coal plants are planned, and quite another to say that they will be completed and used throughout their full potential lifetimes.

The research is based on a database by CoalSwarm, a project of the Earth Island Institute, which carefully tracks coal plants in varying stages of completion across the globe, in collaboration with Greenpeace and the Sierra Club. The group makes is clear that it opposes the new coal plants that it is tracking.

Christine Shearer, a researcher with CoalSwarm, said it’s important to bear in mind that not all coal plants are actually completed. “Since we started doing this work, since 2010, only about a third of proposed coal plants ever begin construction or are commissioned,” she said.

“Stranding or divesting from coal power plants is an outcome that is in reach also,” added Peter Erickson, an expert with the Stockholm Environment Institute, who reviewed the study but was not involved with it. “Coal financing and political and social norms around coal are also rapidly changing.”

Edenhofer, the study author, countered that the current building plans are important information.

“This does not mean we are doomed, but these announcements are announcements which should be taken into account very seriously,” he said. “These are not just paper plants, these are real plants.”

It’s important to consider the implications of the new study in terms of equity, experts say. It’s not fair to say that developing nations should cancel coal plans when major industrialized countries, like Germany and the United States, continue to burn large amounts of coal.

“Higher-income countries have by far the greatest coal power — U.S., Germany, China, Russia, Japan — and so the phaseout in these countries is even more important in the big picture and, also, more equitable,” Erickson said.

Edenhofer doesn’t disagree. He cited Germany as one example of a developed nation set to miss climate targets because it is burning a lot of coal.

“I can see a fairness issue,” Edenhofer said. “But when we want to be fair, this means that we have to support the developing countries in building up a new infrastructure.”

The ultimate conclusion, though, is that operating and future coal plants alike are in tension with the Paris climate agreement and widely accepted climate goals.

“If we don’t stop building coal plants now, we will have four unpalatable options,” said Cameron Hepburn, a researcher at the University of Oxford, in a comment sent by email. “We either (1) shut down coal plants early, (2) retrofit expensive carbon capture technologies, (3) suck even more CO2 out of the atmosphere, potentially at high cost, or (4) burn through the 2 degree C target.”