Global Warming of 1.5°C: An IPCC Special Report by the Intergovernmental Panel on Climate Change Available at www.ipcc.ch

Though it was published at the beginning of October, Global Warming of 1.5°C, a report by the Intergovernmental Panel on Climate Change (IPCC), is a document with its origins in another era, one not so distant from ours but politically an age apart. To read it makes you weep not just for our future but for our present.

The report was prepared at the request of the United Nations Framework Convention on Climate Change at the end of the Paris climate talks in December 2015. The agreement reached in Paris pledged the signatories to

holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change.

The mention of 1.5 degrees Celsius was unexpected; that number had first surfaced six years earlier at the unsuccessful Copenhagen climate talks, when representatives of low-lying island and coastal nations began using the slogan “1.5 to Stay Alive,” arguing that the long-standing red line of a two-degree increase in temperature likely doomed them to disappear under rising seas. Other highly vulnerable nations made the same case about droughts and floods and storms, because it was becoming clear that scientists had been underestimating how broad and deadly the effects of climate change would be. (So far we’ve raised the global average temperature just one degree, which has already brought about changes now readily observable.)

The pledges made by nations at the Paris conference were not enough to meet even the two-degree target. If every nation fulfills those pledges, the global temperature will still rise by about 3.5 degrees Celsius, which everyone acknowledged goes far beyond any definition of safety. But the hope was that the focus and goodwill resulting from the Paris agreement would help get the transition to alternative energy sources underway, and that once nations began installing solar panels and wind turbines they’d find it easier and cheaper than they had expected. They could then make stronger pledges as the process continued. “Impossible isn’t a fact; it’s an attitude,” said Christiana Figueres, the Costa Rican diplomat who deserves much of the credit for putting together the agreement. “Ideally,” said Philip A. Wallach, a Brookings Institution fellow, the Paris agreement would create “a virtuous cycle of ambitious commitments, honestly reported progress to match, and further commitments following on those successes.”

To some extent this is precisely what has happened. The engineers have…