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For Immediate Release


Ashley Siefert Nunes at UCS,

Press Release

UCS Delivers Letter to White House Signed by More Than 1,500 Scientists Urging Biden to Cut Emissions by at Least Half by 2030


The Union of Concerned Scientists (UCS) today delivered a letter to the White House urging President Joe Biden to commit to reducing U.S. heat-trapping emissions by at least 50 percent below 2005 levels by 2030. The letter was signed by more than 1,500 scientists and comes in advance of the anticipated release of the Biden administration’s national plan for reducing global warming emissions—also known as a Nationally Determined Contribution (NDC)—under the Paris climate agreement.

The letter 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. 

“Hundreds of scientists have affirmed that the ambitious goal of cutting emissions in half by 2030 is scientifically feasible and the minimum threshold for what’s necessary,” said Dr. Rachel Cleetus, policy director and lead economist in the Climate and Energy Program at UCS. “We know that we will need to ratchet up ambition even further in the years to come to help limit the worst impacts of climate change and achieve the principal goal of the Paris Agreement—limiting warming to as close to 1.5 degrees Celsius as possible. After years of U.S. inaction to address its role in the climate crisis, we need the Biden administration to commit to bold climate policies and quickly get us on a pathway to what the science demands.”

Dr. Cleetus has attended the UN climate talks and partnered with the international community on climate and energy policies for more than 14 years. In addition to the letter, she can discuss the upcoming U.S. climate summit, anticipated U.S. NDC announcement, and administrative and congressional actions that need to be urgently undertaken before the annual U.N. climate talks in Glasgow this November. Dr. Cleetus also co-authored an opinion piece—titled “Biden’s Earth Day Summit is a Crucial Opportunity for Climate Action”—published today in Scientific American.

UCS also has the following experts, many of whom are letter signatories, available to speak about how the United States can reduce its emissions by at least 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. 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.
  • Dr. 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 her full biography.

If you would like to talk to an expert, please contact UCS Climate and Energy Media Manager 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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