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Washington • When it comes to climate science, two of the three Democratic presidential candidates are A students, while most of the Republican contenders are flunking, according to a panel of scientists who reviewed candidates' comments.
At the request of The Associated Press, eight climate and biological scientists graded for scientific accuracy what a dozen top candidates said in debates, interviews and tweets, using a 0 to 100 scale.
To try to eliminate possible bias, the candidates' comments were stripped of names and given randomly generated numbers, so the professors would not know who made each statement they were grading. Also, the scientists who did the grading were chosen by professional scientific societies.
Former Secretary of State Hillary Rodham Clinton had the highest average score at 94. Three scientists did not assign former Maryland Gov. Martin O'Malley a score, saying his statements mostly were about policy, which they could not grade, instead of checkable science.
Two used similar reasoning to skip grading New Jersey Gov. Chris Christie and one did the same for businesswoman Carly Fiorina. Republican Sen. Ted Cruz of Texas had the lowest score, an average of 6. All eight put Cruz at the bottom of the class.
"This individual understands less about science [and climate change] than the average kindergärtner," Michael Mann, a Pennsylvania State University meteorology professor, wrote of Cruz's statements. "That sort of ignorance would be dangerous in a doorman, let alone a president."
Vermont Sen. Bernie Sanders, with an 87, had the lowest score among the Democrats, dinged for an exaggeration when he said global warming could make Earth uninhabitable.
Former Florida Gov. Jeb Bush scored the highest among Republicans, 64, but one grader gave him a perfect 100. Bush was the only Republican candidate who got a passing grade on climate in the exercise.
Below Clinton's 94 were O'Malley with 91; Sanders, 87; Bush, 64; Christie, 54; Ohio Gov. John Kasich, 47; Kentucky Sen. Rand Paul, 38; Fiorina, 28; Florida Sen. Marco Rubio, 21; businessman Donald Trump, 15; retired neurosurgeon Ben Carson, 13; and Cruz with 6.
For the Republicans, climate change came up more in interviews than in their four debates. But Rubio did confront the issue in the Sept. 16 debate in a way that earned him poor grades from some scientists.
"We are not going to make America a harder place to create jobs in order to pursue policies that will do absolutely nothing, nothing, to change our climate, to change our weather, because America is a lot of things, the greatest country in the world, absolutely," Rubio said. "But America is not a planet. And we are not even the largest carbon producer anymore. China is. And they're drilling a hole and digging anywhere in the world that they can get ahold of."
Scientists dispute Rubio's argument that because China is now the top emitter, the U.S. can do little to change the future climate. The U.S. spews about 17 percent of the world's carbon dioxide emissions, "so big cuts here would still make a big difference globally," said geochemist Louisa Bradtmiller at Macalester College in St. Paul, Minn. Rubio's inference that China is not doing much about global warming "is out of date. The Chinese are implementing a cap-and-trade system in their country to reduce emissions," said Andrew Dessler, a climate scientist at Texas A&M University.
At an August event in California, Cruz told an interviewer, "If you look at satellite data for the last 18 years, there's been zero warming. ... The satellite says it ain't happening."
Florida State University's James Elsner said ground data show every decade has been warmer than the previous one since the middle of the 20th century, and satellite data-based observations "show continued warming over the past several decades."