In a letter to U.S. President Barack Obama, AAAS CEO Alan I. Leshner commended the President's intent to take steps against climate change, announced today at Georgetown University.
Obama's plan aims to cut U.S. greenhouse gas emissions by 17 percent below 2005 levels by 2020, to prepare the United States for the impacts of climate change, and to lead international efforts to address global climate change.
In his letter to the President, Leshner wrote, "On behalf of the American Association for the Advancement of Science (AAAS), we applaud your recent speech on the urgency of tackling global climate change in response to mounting scientific evidence that our world is changing in dramatic ways.
"The AAAS, its Board of Directors and the leaders of many other respected scientific organizations have concluded that global climate change caused primarily by human activities is now underway. Among scientists, in fact, there is now overwhelming agreement, based on multiple lines of scientific evidence, that global climate change is real, it is happening now, and it will have broad impacts on society.
"As a AAAS Board of Directors statement in 2006 noted: "It is essential that we develop strategies to adapt to ongoing changes and make communities more resilient to future changes." Your speech recognizes this as well as the importance of scientific research in supporting regional, national, and global decision-makers who must craft appropriate mechanisms for addressing this complex challenge.
"The scientific community stands ready to assist you," the letter concludes.
Greenhouse gases are warming the Earth, contributing to an intensification of droughts, heat waves, floods, wildfires, and severe storms, according to a 2006 statement  of the AAAS Board of Directors.
Atmospheric carbon dioxide currently stands at nearly 400 parts per million, the latest Scripps CO2 Dataset  shows. Between 1990 and 2100, if emissions continue to increase, temperatures are expected to rise between 2 and 11.5 degrees Fahrenheit (1.1 to 6.4 degrees Celsius), the National Research Council has reported . Continued climate change will affect U.S. crop productivity, and communities in some regions might suffer increased fatalities because of intensely hot summers, AAAS said in releasing its letter. Such dangerous climate-change impacts could persist for decades, and some scientific models predict even more extreme, though less likely impacts caused by carbon pollution and the rapid disappearance of forests.
President Obama's Climate Action Plan aims to reduce greenhouse gas emissions with a variety of strategies, including establishing carbon pollution standards for power plants, supporting innovative technologies and renewable energy sources, and helping buildings become more energy-efficient. The plan also outlines steps to make communities more resilient in the face of climate change, for example by establishing a short-term task force of state, local and tribal officials to advise on key actions the Federal government can take to help strengthen communities on the ground. Internationally, the President aims to use several tactics to help forge a global solution to climate change, such as expanding major new and existing bilateral initiatives with China, India and other major emitting countries.
Read the full letter (PDF ).
President Obama's Climate Action Plan: