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For Immediate Release


Ashley Siefert Nunes at UCS,

Press Release

More Than 1,000 Scientists Sign Letter Urging Pres. Biden to Cut Emissions in Half by 2030


Following its re-entry into the Paris climate agreement, the Biden administration is currently devising a national plan to reduce global warming emissions—also known as a Nationally Determined Contribution (NDC)—over the next decade. Today, the Union of Concerned Scientists (UCS) released a letter signed by over 1,000 scientists urging President Joe Biden and his administration to commit to reducing U.S. heat-trapping emissions by at least 50 percent below 2005 levels by 2030. The number of letter signers could continue to grow as the letter remains open for additional signatories.

According to these experts, this ambitious goal is both scientifically feasible and necessary in order to limit the worst impacts of climate change and achieve the principal goal of the Paris Agreement—limiting warming to 2 degrees Celsius, and as close to 1.5 degrees Celsius as possible. They also emphasized that emissions reductions from the transportation and power sectors, which are the two leading sources for U.S. global warming emissions, must be prioritized, along with investments and policies that create good-paying jobs and further climate resilience, environmental justice, and racial equity. 

Scientists who have already signed onto the letter include: Dr. Joel Clement, senior fellow at Harvard Kennedy School and UCS; Dr. Lauren Edwards, executive director of 500 Women Scientists and director of Fellowship for the Future; Dr. Anne Kapuscinski, director of the Coastal Science and Policy Program at the University of California-Santa Cruz and board chair of UCS; Dr. Michael Mann, distinguished professor of atmospheric science at Pennsylvania State University and lead author of the IPCC Third Assessment Report; Dr. Benjamin D. Santer, climatologist and atmospheric scientist at Lawrence Livermore National Laboratory, a MacArthur Fellowship recipient and an author of the IPCC Second Assessment Report; and Dr. T. Jane Zelikova, research scientist at the University of Wyoming and co-founder of 500 Women Scientists.

UCS has the following experts, many of whom are letter signatories, available to speak about how the United States can reduce its emissions in half over the course of the decade: 

  • Dr. Dave Cooke, senior vehicles analyst in the Clean Transportation Program at UCS. He is based in Washington, D.C. Click here to view his full biography.
  • Dr. Rachel Cleetus, policy director and lead economist in the Climate and Energy Program at UCS. She has attended the UN climate talks and partnered with the international community on climate and energy policies for more than 14 years. Dr. Cleetus is based in Cambridge, Massachusetts. Click here to view her full biography. 
  • Dr. Marcia DeLonge, research director and senior scientist in the Food and Environment Program at UCS. She is based in Oakland, California. Click here to view her full biography.
  • Dr. Brenda Ekwurzel, director of climate science and senior climate scientist at UCS. She is a co-author of the Fourth National Climate Assessment. Dr. Ekwurzel is based in Washington, D.C. Click here to view her full biography.
  • Dr. Peter Frumhoff, director of science and policy and chief climate scientist at UCS. He is the lead author of the IPCC Fourth Assessment Report. Dr. Frumhoff is based in Cambridge, Massachusetts. Click here to view his full biography.
  • Jonna Hamilton, senior manager of government affairs for the Clean Transportation Program at UCS. She is based in Washington, D.C. Click here to view her full biography.
  • Dr. Adrienne Hollis, senior climate justice and health scientist at UCS. She is based in Washington D.C. Click here to view full her biography.

If you would like to talk to an expert, please contact UCS Senior Communications Officer Ashley Siefert Nunes.

On March 8, UCS joined the World Resources Institute, Environmental Defense Fund, Natural Resources Defense Council and University of Maryland for a media briefing where experts put forth detailed scientific analyses showing how the United States could achieve such a target. To watch the recording of this media briefing featuring Dr. Cleetus, click here



The Union of Concerned Scientists is the leading science-based nonprofit working for a healthy environment and a safer world. UCS combines independent scientific research and citizen action to develop innovative, practical solutions and to secure responsible changes in government policy, corporate practices, and consumer choices.

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