The Union of Concerned Scientists released a landmark statement, signed by more than 1,700 prominent U.S. scientists and economists that calls for swift and deep reductions in our nation’s global warming pollution. This unprecedented list of signatories includes six Nobel Prize winners in science or economics, 30 members of the National Academy of Sciences, 10 members of the National Academy of Engineering, 10 recipients of the MacArthur Fellowship, and more than 100 members of the Intergovernmental Panel on Climate Change, which shared the 2007 Nobel Peace Prize.

We call on our nation’s leaders to swiftly establish and implement policies to bring about deep reductions in heat-trapping emissions. The strength of the science on climate change compels us to warn the nation about the growing risk of irreversible consequences as global average temperatures continue to increase over pre-industrial levels (i.e., prior to 1860). As temperatures rise further, the scope and severity of global warming impacts will continue to accelerate.

The 2007 report of the Intergovernmental Panel on Climate Change unequivocally concluded that our climate is warming, stating with at least 90 percent certainty that the warming of the last several decades is primarily due to human activities. Global average temperatures have already risen ~ 0.7°C (1.3°F) over the last 100 years, and impacts are now being observed worldwide. Human-caused emissions to date have locked in further changes including sea-level rise that will intensify coastal flooding, and dramatic reductions in snowpack that will disrupt water supplies in the western United States. If emissions continue unabated, our nation and the world will face more sea level rise, heat waves, droughts, wildfires, snowmelt, flood risk, and public health threats, as well as increased rates of plant and animal species extinctions.

The longer we wait, the harder and more costly it will be to limit climate change and to adapt to those impacts that will not be avoided. Many emissions reduction strategies can be adopted today that would save consumers and industry money while providing benefits for air quality, energy security, public health, balance of trade, and employment.

All nations must commit to a goal designed to limit further harm. The European Union and a number of other countries have adopted a goal for limiting global warming to no more than 2ºC (3.6°F) above preindustrial levels. Emerging science must be regularly evaluated to assess whether this goal is sufficient.

The UN Framework Convention on Climate Change recognizes that all nations have a responsibility to curb global warming, consistent with their respective contribution to emissions and capacity to act. Recent analyses indicate the United States—even with aggressive action by other nations—would need to reduce its emissions on the order of 80 percent below 2000 levels by 2050 to have a reasonable chance of limiting warming to 2ºC.

A strong U.S. commitment to reduce emissions is essential to drive international climate progress. Voluntary initiatives to date have proven insufficient. We urge U.S. policy makers to put our nation onto a path today to reduce emissions on the order of 80 percent below 2000 levels by 2050. The first step on this path should be reductions on the order of 15-20 percent below 2000 levels by 2020, which is achievable and consistent with sound economic policy.

There is no time to waste. The most risky thing we can do is nothing.

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Landmark Statement on global warming