As global climate talks resume this week, the U.S. is straddling a climate credibility gap, with the Trump administration's policies on one side of an abyss and what the government's own scientists know about climate change with increasing certainty on the other.
The disconnect became more evident last week as the administration published, but then basically shrugged off, a comprehensive report on the state of climate science.
Written by authoritative government and academic experts, then honed by the extreme vetting of a formal National Academy of Sciences peer review, the latest volume of the National Climate Assessment paints a stern and explicit picture of the risks of climate change.
The report's executive summary pronounced that temperatures have reached the warmest point in human civilization, that our own actions are the cause, and that the worst is yet to come.
It followed with a staccato drum-roll of familiar findings: "Thousands of studies conducted by researchers around the world have documented changes in surface, atmospheric, and oceanic temperatures; melting glaciers; diminishing snow cover; shrinking sea ice; rising sea levels; ocean acidification; and increasing atmospheric water vapor."
On Monday, the G7 countries—including the U.S.—also affirmed that climate change exacerbates health risks.
Meanwhile, the Trump administration and its Republican allies in Congress remain wedded to an expansion of fossil-fuel energy that the science says is at the root of the problem.
In recent weeks, they have moved to: repopulate the Environmental Protection Agency's science advisory board with faces friendlier to its pro-industry cause; issue a tax bill that undermines renewable energyand fosters oil, coal and gas; expand drilling and mining from the Arctic to the Gulf of Mexico; and rejigger the calculations of how much greenhouse gas emissions will cost society. They sent a stripped down team of bureaucrats to the climate talks without much of an agendaother than to preserve the role of fossil fuels in the decades ahead, which the science warns will lead to crises.
What the Science Shows Is Necessary
The credibility gap can be captured in a simple concept, affirmed by every scientific authority: to limit the planet's warming, emissions of carbon dioxide have to be brought rapidly to zero.
To keep the globe within 2 degrees Celsius of warming since the dawn of the industrial age, the government's new climate assessment confirms, emissions of greenhouse gases need to reach net zero by 2080. To keep it within safer limits of 1.5 degrees, the ambition of Paris, that needs to happen by 2050.
By now, these and the other detailed conclusions of the NCA are so widely accepted by scientists that they should come as no surprise.
The first public draft of the report delivered essentially the same messages last December; an academic review clarified and endorsed them in the spring, and a leaked, all-but-final draft of the report a few months later made clear that there was no backing away from them.
Katharine Hayhoe of Texas Tech, one of the main authors of the NCA, began a thorough Twitter thread dissecting the findings with this conclusion: "The time to act is now."
The sense of urgency is driven by the carbon budget numbers. For some time, it has been plain that time is running out for fossil fuels.
The NCA report presented the details which, within the normal bounds of uncertainty, are as follows:
- Limiting warming to less than 2 degrees puts a limit on future carbon dioxide emissions of about 230 gigatons—the basic carbon budget facing the world. This number, unless steep cuts in emissions occur, is likely to be exceeded sometime around the years 2033 to 2037; exactly how soon depends on how ambitious are future limits on emissions.
- To stay within 1.5 degrees—enough ambition, just maybe, to keep Fiji, the presiding nation at this year's talks in Bonn, above water—requires even deeper cuts. Indeed, it means giving off just 30 more gigatons worldwide, a budget that seems very likely to be exceeded "in just a few years."
- Even with a reversal of forest and soil losses, or a breakthrough in carbon capture and sequestration, or other steps toward so-called "negative emissions," there need to be deep reductions in the use of fossil fuels.
"There is broad consensus that the further and the faster the Earth system is pushed towards warming, the greater the risk of unanticipated changes and impacts, some of which are potentially large and irreversible," the NCA concluded.
How the Trump Administration Is Responding
The Trump administration reacted in a perfunctory statement by a deputy press secretary mouthing a denialist meme: that the climate is "always changing."
That sound bite trivializes the latest authoritative data—such as that in the World Meteorological Organization's newly issued State of the Climate 2017 report. WMO's bullet points: this is the warmest year ever except for a few El Nino peaks, and the past five years were the warmest ever; ocean heat is at record levels; sea ice is well below average at both poles; September's hurricanes shattered records; sea level rise continues, as does ocean acidification; and of course the blanket of carbon dioxide that's causing it all is growing.
That is the reality. But as the rest of the world gathers in Bonn for the latest round of talks on how to confront the crisis—by increasing everyone's efforts to reduce emissions—Washington is going the other way.