375 Prominent Scientists Warn Against US Withdrawal from Paris Climate Accord

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Publication date: 
26 September 2016

In an open letter published last week, 375 members of the National Academy of Sciences reasserted the scientific consensus on climate change, chided U.S. politicians who remain naysayers, and warned against U.S. withdrawal from the landmark Paris Agreement on climate.

"Human-caused climate change is not a belief, a hoax, or a conspiracy. It is a physical reality,” begins an open letter on climate change from 375 members of the National Academy of Sciences, including 30 Nobel laureates. The letter, signed by dozens of prominent physical scientists as well as leading scientists in other disciplines, uses bold language to frame the science on human-caused climate change as “certain beyond a reasonable doubt” and warns strongly against what it terms as a future “Parexit,” a U.S. withdrawal from the landmark Paris Agreement negotiated under the U.N. Framework Convention on Climate Change (UNFCCC) last December and poised to enter into force later this year.

The letter chide U.S. politicians who made claims during this year’s presidential primary campaign that contradict the vast body of scientific evidence:

During the Presidential primary campaign, claims were made that the Earth is not warming, or that warming is due to purely natural causes outside of human control. Such claims are inconsistent with reality.

The open letter also includes a specially tailored message for Republican presidential nominee Donald Trump, cautioning that, much like the climate system, “the political system also has tipping points”:

It is of great concern that the Republican nominee for President has advocated U.S. withdrawal from the Paris Accord. A ‘Parexit’ would send a clear signal to the rest of the world: ‘The United States does not care about the global problem of human-caused climate change. You are on your own.’

The scientists argue in the letter that pulling out of the Paris agreement would bring about “severe and long-lasting” consequences for both the Earth’s climate and for the U.S.’s place in the world: “Walking away from Paris makes it less likely that the U.S. will have a global leadership role, politically, economically, or morally. We cannot afford to cross that tipping point.

The letter was organized by two atmospheric scientists and two astrophysicists:

  • Benjamin Santer, a research climatologist at Lawrence Livermore National Laboratory;
  • Kerry Emanuel, professor of meteorology at MIT;
  • George Field, professor emeritus of applied astronomy at Harvard University; and
  • Ray Weymann, a retired astronomer and astrophysicist associated with the Carnegie Institution for Science.

Other prominent public leaders who signed on the letter include:

  • Steven Chu, former Secretary of Energy;
  • Ralph Cicerone, former president of the National Academies of Science, Engineering, and Medicine;
  • Rita Colwell, former director of the National Science Foundation;
  • Stephen Hawking;
  • Jane Lubchenco, former administrator of the National Oceanic and Atmospheric Administration;
  • Frank Press, former science advisor to President Jimmy Carter; and
  • Maria Zuber, chair of the National Science Board.

Paris Agreement on track to enter into force by end of 2016

President Obama at the Paris climate conferenceRepresentatives of nearly all the world’s countries negotiated the Paris Agreement last December at the most recent meeting of the UNFCCC. 191 countries have since signed the agreement, and 61 of those have ratified, including U.S. and China—the world’s largest emitters of greenhouse gases (GHGs). The landmark climate change agreement requires parties to develop national plans to contribute to an international goal of reducing GHG emissions to a level necessary to hold global average temperature to an increase of 2 degrees Celsius above pre-industrial levels. Other parts of the agreement focus on climate change adaptation, resilience, and international financing for developing nations.

Unlike most other international environmental law treaties and conventions, its targets are not enforceable by an international body. Rather, each individual party will be responsible for setting and enforcing its own GHG targets, and the agreement carries no consequences if countries do not meet their commitments.

The Paris agreement will enter into effect when 55 or more countries representing at least 55 percent of the world’s GHG emissions have ratified, a goal that has nearly been reached. At last week’s meeting of the U.N. General Assembly in New York City, Secretary General Ban Ki-moon announced that over 60 countries had already joined the agreement, accounting for about 48 percent of current global greenhouse emissions. He remarked, “I am using every opportunity to push for the early entry into force of the Paris Agreement before the end of this year.

Yesterday, India, which accounts for about 4.5 percent of global GHG emissions, announced it will ratify the agreement on Oct. 2 to coincide with Mahatma Gandhi’s birthday. At that point, the treaty will be on the brink of entering into force.

The Obama Administration formally ratified the Paris agreement at the beginning of September, but the U.S.’s ability to enforce the administration’s GHG commitments is in question. In particular, the administration’s climate policy is riding on the outcome of a high profile case before the Supreme Court that is challenging the legality of the Environmental Protection Agency's Clean Power Plan to regulate power plant emissions.

Much also rides on the upcoming presidential election in November. The official 2016 Republican party platform questions the legality of Obama’s executive order used to ratify the Paris agreement, arguing that Senate support should have been necessary for ratification.

While Democratic presidential nominee Hillary Clinton has said she will uphold the agreement, Republican nominee Donald Trump has said he will abandon it if elected. However, should a President Trump take the nation that direction, he may not be able to pull the U.S. out of the Paris agreement overnight. According to the agreement, countries that ratify must wait for three years after it has gone into legal force before they can begin the process of withdrawing.


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