Congress Gets Another Reminder From Scientists That Climate Change Isn't Coming -- It's Already Here

The severity of climate change is already harming the global economy, natural resources and human health -- and it will only get worse in the coming decades, say leading U.S. policymakers and scientific organizations in a letter they sent to Congress on Tuesday.

"Climate change is real and happening now, and the United States urgently needs to reduce greenhouse gas emissions," said Rush Holt, the CEO of the American Association for the Advancement of Science and publisher of the Science group of journals.

"We must not delay, ignore the evidence, or be fearful of the challenge," Holt said. "America has provided global leadership to successfully confront many environmental problems, from acid rain to the ozone hole, and we can do it again. We owe no less to future generations."

The letter urges Congress to take action to substantially reduce greenhouse gases, highlighting disasters caused by climate change that have already affected the U.S., including drought, heat waves, wildfires and rising sea levels.

A failure to take action could threaten everything from our food supply to our national security, stated retired U.S. Naval Rear Admiral Jonathan White, who is now CEO of the Consortium for Ocean Leadership.

Man-made climate change is "not a matter of opinion, but of careful evaluation of data from a vast spectrum of scientific disciplines," added Anne Yoder, president of the Society of Systematic Biologists, in a statement.

"What remains unclear is the degree to which climate change will cause environmental, social, and economic havoc," Yoder said. "Estimates range from severe to catastrophic. We owe it to our children and to our children's children to take bold action now so that our descendants do not pay the price for our generation's greed."

Some of the nation's top nonpartisan scientific groups, including the American Chemical Society, the American Meteorological Society and the American Public Health Association, signed Tuesday's letter.

A number of the groups sent a similar plea to lawmakers in 2009, imploring them to take the threat of climate change seriously and take meaningful action to stop it.

Since 2009, lawmakers have proposed more than 800 pieces of legislation related to climate change. The vast majority have failed, with votes largely falling along partisan lines in the Republican-controlled Congress.

Read the full letter to Congress below.