President Donald Trump says that the Fourth National Climate Assessment, authored by representatives of 13 federal agencies, is focused on an extreme scenario of climate and on the year 2100. “Next time we will have better scenarios,” he said to the media while he was waiting for his helicopter on the White House lawn on Friday. Let’s wait (four years) for that report before worrying about the problem, if it exists, was his message.

As an environmental economist who has worked on climate change for four decades, was vice chair for the Third National Climate Assessment, and was a reviewer of the new report, I believe this approach is folly. It is irresponsible. It is, in fact, immoral because it would unnecessarily put human lives at risk.

It has been accepted by governments all over the world, and by states and municipalities across the United States, that responding to climate change is an “iterative risk management” problem, according to the report.

“Iterative” means that we should be informed about long-term possibilities even as we concentrate on the near term.

“Risk management” requires us to account for the extremes in our decision-making. It means that we should not focus exclusively on the more benign median. The Fourth National Climate Assessment responds to this challenge by presenting a low and high emissions scenario to display the range of potential futures. Sadly, the future is dark regardless of the path we choose.

What does abdicating responsibility now mean for the mid-course corrections that will be undertaken in 2030 or 2050? It means that the next iteration will be more aggressive and more expensive than it would have been otherwise. What does the recent history tell us about the near term?

The experiences of 2017 and 2018 across the country and around the globe show that climate change is happening and that damages calibrated in the billions of dollars at specific locations are already disastrous. The Fourth National Climate Assessment says that that this pattern will only get worse.

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The president says that “something’s changing, but it will change back.”

No it won’t, at least not without action.

The Fourth National Climate Assessment says that delaying response, waiting for the fiction of changing back to occur, will be increasingly expensive. It says that responding is not a matter of “if”; it is a matter of “when.” It says that the inevitable responses will only cost more dollars and more lives the longer we wait to act.

The fundamental messages of The Fourth National Climate Assessment are familiar. They amplify the findings of assessments published over the past 15 years by bodies including the National Academies of Science, Engineering, and Medicine, the Intergovernmental Panel on Climate Change, and the 2014 National Climate Assessment. The retrenchment of the Trump administration means that we have erased the progress of the Obama years and have wasted 15 years. Waste another two or six years, and the news will be even worse. Both the costs and benefits of action will be even higher. More people will have died, and more economic treasure will have disappeared. Again, unnecessarily.

In context, The Fourth National Climate Assessment says that the time to act, both in mitigating emissions and adapting to risks, is now - notwithstanding the intransigence of the current president of the United States.

Gary Yohe is the Huffington Foundation Professor of Economics and Environmental Studies at Wesleyan University. He was vice chair of the Third National Climate Assessment and a member of the National Academy of Sciences Panel that reviewed an earlier draft of the Fourth National Climate Assessment last December. He wrote this for the Hartford Courant.