Thirty-one scientific organizations have sent a letter to Congress saying that not only is climate change real, but U.S. policymakers must take steps to reduce greenhouse gas emissions if they want to reduce its worst effects.

"Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research concludes that greenhouse gases emitted by human activities are the primary driver," the organizations state in the June 28 letter.

The letter was released one day before the leaders of the U.S., Canada and Mexico announced their nations would strive to get 50 percent of their energy from clean and renewable sources by 2025. The American Association for the Advancement of Science, American Chemical Society, American Geophysical Union and American Meteorological Society were among the signatories.

"Climate change is real and happening now, and the United States urgently needs to reduce greenhouse gas emissions," AAAS CEO Rush Holt said in a separate statement. "We must not delay, ignore the evidence, or be fearful of the challenge."

Some lawmakers have cast doubt that climate change is happening while others have downplayed its potential effects. In their letter, the organizations make clear that such views don't conform to the scientific consensus.

"Climate change is one of the most profound challenges facing our society," AGU CEO Christine McEntee said. "Consensus on this matter is evident in the diversity of organizations that have signed this letter. Science can be a powerful tool in our efforts to mitigate and adapt to the impacts of climate change, and we stand ready to work with policymakers as they deliberate various options for action." http://bit.ly/298XuWe

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