A Project of The Annenberg Public Policy Center

Santorum’s Science

Rick Santorum calls global warming a “hoax.” If he were a scientist, he would be in a small minority.

“The dangers of carbon dioxide? Tell that to a plant, how dangerous carbon dioxide is,” Santorum said at the Gulf Coast Energy Summit in Biloxi, Miss., on March 12. He made similar comments in early February in Colorado Springs, Colo., saying that global warming was a “hoax” and that “man-made global warming” and proposed remedies were “bogus.”

Santorum isn’t the only climate change skeptic, but skeptics are rare among scientists who actually study the climate. A paper published in 2010 by the National Academy of Sciences found that 97 percent to 98 percent of climate researchers “most actively publishing in the field” agreed that climate change was occurring.

Proceedings of the National Academy of Sciences, April 9, 2010: Here, we use an extensive dataset of 1,372 climate researchers and their publication and citation data to show that (i) 97–98% of the climate researchers most actively publishing in the field support the tenets of ACC outlined by the Intergovernmental Panel on Climate Change, and (ii) the relative climate expertise and scientific prominence of the researchers unconvinced of ACC are substantially below that of the convinced researchers.

The Intergovernmental Panel on Climate Change is an international scientific body that said in its latest report on climate change, in 2007, that the earth is getting hotter, sea levels are rising and human activity is “very likely” the cause of “most of the observed increase in global average temperatures since the mid-20th century.”

Carbon dioxide levels in the atmosphere are rising. The National Oceanic and Atmospheric Administration’s Global Monitoring Division has measured greenhouse gases for decades at sites around the world. Its latest chart shows the rise in CO2 since 2008.

And CO2, a greenhouse gas, traps heat. The National Library of Medicine says that CO2 “is a ‘greenhouse gas’ because it absorbs heat in the atmosphere, sending some of the absorbed heat back to the surface of the earth and contributing to global warming.”

National Library of Medicine: Carbon dioxide emissions represent about 80 percent of all greenhouse gas emissions in the United States. Sources of carbon dioxide emissions, which contribute to climate change, include fossil fuel burning, electricity generation, transportation vehicles, cement or lime manufacturing, waste burning, and natural gas flaring.

CO2 Not ‘Dangerous’?

Santorum’s “tell that to a plant” crack raises the question — how dangerous can carbon dioxide be? Too much is definitely a bad thing. Exposure to high levels of CO2 can cause “headaches, dizziness, restlessness, a tingling or pins or needles feeling, difficulty breathing, sweating, tiredness, increased heart rate, elevated blood pressure, coma, asphyxia to convulsions,” warns the Wisconsin Department of Health, “and even frostbite if exposed to dry ice,” which is solid CO2. Poor air circulation in buildings and high carbon dioxide in soil seeping into basements can lead to high levels of the gas.

Plants do, in fact, absorb CO2. But even plants might not like too much of it. A 2008 study conducted at the University of Illinois found that instead of increasing organic matter in soil, higher carbon dioxide levels actually led to less organic matter. Increased CO2 also may limit plants’ ability to cool the air. A 2010 article in Science Daily said that a study by researchers at the Carnegie Institution for Science found that carbon dioxide’s effect on vegetation was causing some of the earth’s warming.

Science Daily, May 3, 2010: Plants give off water through tiny pores in their leaves, a process called evapotranspiration that cools the plant, just as perspiration cools our bodies. On a hot day, a tree can release tens of gallons of water into the air, acting as a natural air conditioner for its surroundings. The plants absorb carbon dioxide for photosynthesis through the same pores (called stomata). But when carbon dioxide levels are high, the leaf pores shrink. This causes less water to be released, diminishing the tree’s cooling power.

Santorum is entitled to his own opinion, of course. But voters shouldn’t be misled into thinking carbon dioxide isn’t a problem, or that climate scientists don’t overwhelmingly agree that global warming is real and human activities are making it worse.

— Lori Robertson