Organizing for Action, the grassroots offshoot of President Obama's re-election campaign, sent an email to supporters Tuesday saying "climate change is real," adding that "there's no credible scientific debate anymore."

The email urged recipients to provide public comments backing the proposed Environmental Protection Agency greenhouse gas emissions rules on new and existing power plants, the centerpiece of the climate agenda Obama rolled out in June.

"[W]e don't have anything in place on a national level to regulate the amount of carbon they put in the air," Jack Shapiro, deputy climate campaign manager with OFA, wrote in the email. "That's why the EPA announced a new proposal to set carbon pollution standards for power plants, the same way we regulate other dangerous substances, like arsenic and mercury."

The rules have invited criticism from industry officials, Republicans and centrist Democrats, who say the regulations would raise energy prices and harm the economy.

Many of the lawmakers who oppose the rules, however, are skeptical of or deny the impact burning fossil fuels has on the climate, despite an overwhelming consensus of scientists saying that is what is driving global warming.

Democrats, public health organizations and environmental groups support the rules, contending they're necessary for addressing climate change.

They say the rules will yield billions of dollars in savings in health care costs and damages from extreme weather, such as storms and drought, linked to global warming.

Experts agree that for policies to have any measurable effect on curbing climate change, energy emissions -- which account for two-thirds of global carbon pollution, according to the International Energy Agency -- must be reined in.

The OFA email hit on that point, noting that about 40 percent of all carbon pollution in the U.S. comes from power plants.

"It's a common-sense way to start to make a very real dent in reducing carbon pollution," Shapiro said of the emissions rules.