Climate Scientists Issue Their Report. Now It’s Our Turn

The Intergovernmental Panel on Climate Change releases the first chapter of its new report on global warming. The findings are clear, but the politics remain murky

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Protests outside the IPCC meeting today in Stockholm

95%. That’s how certain the hundreds of scientists who contribute to the Intergovernmental Panel on Climate Change (IPCC), which released the first chapter of its fifth assessment on global warming this morning, are that human beings are the “dominant cause of observed warming” that’s been seen since the mid-20th century.

In science, which almost always speaks in probabilities, that’s about as clear as you get. This is not news—while the certainty around the scientific case for man-made climate change has tightened somewhat, much of the new report reiterates the conclusions reached in the last IPCC assessment,which was released in 2007. But while the broad conclusions of the science may not have changed that much, the political environment into which the report is being released has changed significantly. Or perhaps better—it hasn’t changed that much. The scientific case for taking action to reduce greenhouse gas emissions and prepare for the effects of climate change remains clear, despite nagging doubts about the fact that global temperatures have risen more slowly in recent years despite the continued increase in carbon emissions. But exactly what and how much action should be taken, and how politicians should balance tomorrow’s threat of climate change against any number of present day challenges, is something that won’t be answered by another thick sheaf of scientific reports.

Which isn’t to say that the scientists aren’t trying. Going beyond the conclusions seen in the last four assessments, which date back to the early 1990s, this year the IPCC formally endorsed a “carbon budget”—a red line for the amount of carbon dioxide, created chiefly by burning fossil fuels and through deforestation, that can be emitted without warming increasing beyond an internationally agreed target of 3.6 F (2 C). Think of it as a speed limit for the global economy—emit more than one trillion tons of carbon, and we’ll likely be in the red. That should be worrying, given the fact that there are 3 trillion tons of carbon left in the ground, and as I wrote in TIME this week, energy companies are developing new technologies, like hydrofracking and directional drilling, that are enabling them to find fossil fuels that were long considered uneconomical.

That means humanity is poised to blow past the carbon limit, as Myles Allen, an Oxford researcher and one of the authors of the IPCC report, told the New York Times:

Limiting the warming to the agreed-upon target “is technically doable, but at the moment we’re not going in the right direction,” Dr. Allen said in an interview. “I don’t think we’ll do it unless we bite the bullet and start talking about what we’re going to do with that extra carbon that we can’t afford to dump into the atmosphere.”

Of course, we’ve been arguing about what to do with that extra carbon for years, and when the U.N. Framework Convention on Climate Change (UNFCCC) meets for its annual summit this November in Warsaw, the debate will be joined yet again. Optimistically, many governments are doing more about their carbon emissions. Europe has long been a leader, and in the U.S., the Environmental Protection Agency just announced new draft regulations that would make it all but impossible to build new coal plants without expensive carbon-capture technology. China, the world’s biggest carbon emitter, is beginning to realize that it can’t simply keep burning carbon-heavy coal forever—albeit more because of the local pollution it causes then out of fears of climate change.

But the truth is we’re nowhere close to a path that would have the world essentially stop emitting carbon by about mid-century. And for all its confidence on the basics behind climate change and its drivers, the IPCC report underscores that there are still significant uncertainties around climate science, including the role of the understudied oceans, which have been absorbing much of the excess heat generated by global warming; the effect of warming on the animals and plants that live on this planet, including us; and perhaps most importantly, the actual level of warming we’ll experience as emissions continue to pile up in the atmosphere.

Climate skeptics have seized on the fact that the rate of warming over the past decade or so has been less than climate scientists predicted given the continued increase in carbon emissions. The IPCC report address the warming “hiatus,” as it’s been called, raising a number of possible explanations—the ocean absorbing the warmth, changes in the solar cycle, volcanic eruptions that cause cooling—without pointing the finger at a single one. Which just underscores how complex the climate system remains, even as we keep experimenting on it. The scientists will keep working on those questions and others, but the ball is in the politicians’ court now, as it has been for years. Which means, really, that it’s up to us.