President Obama, writing in the nation's leading science journal, declared that "the trend toward clean energy is irreversible" regardless of the different policy choices likely to come from his successor.
In an unusual essay by a departing president, Obama urged Donald Trump not to "step away from Paris," where the world's nations pledged in 2015 to accelerate the shift to carbon-free energy to slow global warming.
"This does not mean the next Administration needs to follow identical domestic policies to my Administration's," he wrote in an essay published Monday by the journal Science. "There are multiple paths and mechanisms by which this country can achieve—efficiently and economically, the targets we embraced in the Paris Agreement."
It is the latest of several attempts by Obama and his departing team to define his own legacy on climate change and other issues, in hopes that the Trump arrivals will not move too quickly on their instincts. In most respects they strongly favor fossil fuels and resist science-based calls for deep decarbonization.
"Although our understanding of the impacts of climate change is increasingly and disturbingly clear, there is still debate about the proper course for U.S. policy—a debate that is very much on display during the current presidential transition," Obama wrote. "But putting near-term politics aside, the mounting economic and scientific evidence leave me confident that trends toward a clean-energy economy that have emerged during my presidency will continue and that the economic opportunity for our country to harness that trend will only grow."
Obama boasted that during his tenure, emissions of carbon dioxide from energy in the U.S. fell 9.5 percent from 2008 to 2015 while the economy grew by 10 percent.
But some of that drop was due to the recession that welcomed him to office in 2009, or to other market or technology trends beyond his control; and to the extent his policies deserve credit, many are now under challenge.
In his essay, he concentrated on trends that are likely to sustain themselves.
The cost of renewable energy, for example, is plummeting, and "in some parts of the country is already lower than that for new coal generation, without counting subsidies for renewables," he wrote.
That is an argument made recently, too, by his own Council of Economic Advisers. He also cited a report on climate risks by his own Office of Management and Budget to argue that business-as-usual policies would cut federal revenues because "any economic strategy that ignores carbon pollution will impose tremendous costs to the global economy and will result in fewer jobs and less economic growth over the long term."
"We have long known, on the basis of a massive scientific record, that the urgency of acting to mitigate climate change is real and cannot be ignored," he wrote.
He said a "prudent" policy would be to decarbonize the energy system, put carbon storage technologies to use, improve land-use practices and control non-carbon greenhouse gases.
"Each president is able to chart his or her own policy course," he concluded, "and president-elect Donald Trump will have the opportunity to do so."
But the latest science and economics, he said, suggests that some progress will be "independent of near-term policy choices" —in other words, irreversible.