A group of 20 U.S. climate scientists and experts sent an open letter to President Obama and members of Congress on Monday calling for aggressive action on climate change.

The scientists say that the American Clean Energy and Security Act under discussion in the House marks a “powerful advance and must be enacted this year,” but they are clear that it should just be the first of many steps. The bill as it stands does not go far enough in addressing the action that the science dictates is needed to avert climatic disruption, they argue. They also call on Obama to step up and call for the strongest legislation possible.

Here’s their letter:

An Open Letter to the President and Members of Congress
Strong Leadership Needed Now on Climate

Strong leadership by the United States will be required to move the nations of the world away from what scientists increasingly recognize as a rapidly developing global climatic catastrophe. That leadership requires the insight, energy and relentless attention of the President and no less vigorous interest from both houses of the U. S. Congress.

The Waxman-Markey bill now being considered by the Congress offers a powerful advance and must be enacted this year. But at its best it will be only a first step in the direction that scientists now recognize as necessary to protect local and regional climates. Our purpose is to call attention to the large difference between what U.S. politics now seems capable of enacting and what scientists understand is necessary to prevent climatic disruption and protect the human future. We urge President Obama to exercise maximum personal leadership beginning now to ensure that the strongest possible legislation emerges from the Congress.

New information arrives daily to confirm what many specialists have known for three decades: human-caused climatic disruption is serious, moving rapidly, and gaining momentum with every delay in correcting the trend. In 1992 more than 180 nations including the United States met in Rio de Janeiro, signed, and later ratified, the Framework Convention on Climate Change and in so doing agreed to “stabilize” the heat-trapping gases of the atmosphere at levels that will protect human interests and nature. We, the nations globally, have not been true to our word, and climate is moving out from under civilization rapidly. Major droughts on every continent are but one current symptom of the scale of the global environmental corruption now entrained.

In many political circles around the world, the view has taken hold that nations should endeavor both to limit the buildup of carbon dioxide, the principal greenhouse gas and a by-product of burning coal, oil and natural gas, to 450 parts per million and to limit the rise of global temperatures to less than 2°Celsius. We and many others are of the view that these objectives are inadequate to sustain the integrity of global climate and to hold the risk of ruinous climatic change to an acceptably low level. United States policy must provide a fully satisfactory U.S. contribution to global greenhouse gas reductions that move beyond these inadequate international limits.

It is essential that the Waxman-Markey bill, strengthened wherever possible and certainly not weakened, advance into law rapidly. It is also essential that it become the basis for a serious, continuing, and urgent effort on the part of the President to lead the American public into recognition of the scale of the climatic disruption so that the U.S. will embrace still stronger policies to do what we know from scientific investigation is necessary to prevent disastrous climatic alteration.

As we write, we see the unfolding Presidential effort to lead the nation in the area of universal health insurance. We urge the President to initiate an effort at least comparable in the area of climatic change. We recognize the difference in popularity of these two causes, but it is the essence of Presidential leadership to show the way even where adequate public awareness of the risks ahead may be lacking. Speaking in Germany recently, President Obama referred to climatic change as “a potentially cataclysmic disaster.” We agree and believe that message must be communicated and elaborated to the American people in time to assure strong, effective Congressional action in both houses of Congress this year.

The time for national action on climatic change is now. There has already been too much delay. The stakes are far too high to compromise the integrity of, and our responsibility for, prompt national action.

Signed

Dean Abrahamson, Professor Emeritus, Humphrey Institute of Public Affairs, University of Minnesota, Minneapolis
Robert Costanza, Gordon and Lulie Gund Professor of Ecological Economics and Director, Gund Institute for Ecological Economics, Rubenstein School of Environment and Natural Resources, The University of Vermont
Peter H. Gleick, N.A.S; President, Pacific Institute, Oakland, California
Richard A. Houghton, Senior Scientist, Acting Director, The Woods Hole Research Center, Woods Hole, Massachusetts
Ralph Keeling, Professor, Scripps Institution of Oceanography, University of California, San Diego Donald Kennedy, President Emeritus and Bing Professor of Environmental Sciences, Emeritus, Institute for International Studies, Stanford University
Thomas Lovejoy, Heinz Center for Science, Economics and the Environment, Washington, D.C.
Michael MacCracken, Chief Scientist for Climate Change Programs, Climate Institute, Washington, D.C.
Michael E. Mann, Director, The Earth System Science Center, Professor of Meteorology, The Pennsylvania State University, University Park
Michael McElroy, Gilbert Butler Professor of Environmental Science, Harvard University. Cambridge, MA
Steve Running, Professor, Director , Numerical Terradynamic Simulation Group, Department of Ecosystem Science, Univ. of Montana, Missoula
William Schlesinger, President and Director, The Cary Institute of Ecosystems Studies, Millbrook, N.Y. Stephen H. Schneider, Melvin and Joan Lane Professor for Interdisciplinary Environmental Studies; Professor, Department of Biology, Stanford University
Richard C. J. Somerville, Distinguished Professor Emeritus, Scripps Institution of Oceanography, University of California, San Diego
James Gustave Speth, Dean, Yale School of Forestry & Environmental Studies, New Haven, Connecticut
Lonnie G. Thompson, Distinguished University Professor, School of Earth Sciences; Senior Research Scientist, Byrd Polar Research Center. The Ohio State University, Columbus
Warren Washington, Senior Scientist, National Center for Atmospheric Research, Boulder, Colorado
Richard S. Williams, Senior Scientist Emeritus, USGS; Visiting Senior Scientist, The Woods Hole Research Center, Woods Hole, Massachusetts
Timothy E. Wirth, President, The United Nations Foundation, Washington, D.C.; former US Senator from Colorado
George M. Woodwell *, Director Emeritus, Senior Scientist, The Woods Hole Research Center, Woods Hole, Massachusetts

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* to whom correspondence should be addressed
(Organizations identified for identification purposes only; names listed in alphabetical order.)

The letter was initiated by four of the signees: Speth, Houghton, Schlesinger, and Woodwell, according to a release from the Woods Hole Research Center.