Each Friday, CNN will answer one of your questions on climate change, which is one of the most important (and confusing) topics that far too few of us are talking about. To submit a question, fill out this Google Form. Answers will show up here and on CNN International. In other words: Ask a question, and you could end up on TV.
This ongoing Q&A is part of CNN’s Two° series. For more, check out the Two° homepage and consider signing up for our weekly newsletter. And thank you! — John Sutter, CNN columnist
Question: What do the U.S. presidential contenders think about global warming?
From: Randy McNamara, San Francisco
Answer: John D. Sutter, CNN columnist
Date: September 18
We got yet another frightening glimpse this week at the CNN Republican debate of what some U.S. presidential contenders think (or don’t think) of climate science.
Here’s a back-and-forth between moderator Jake Tapper and Republican Sen. Marco Rubio, a noted skeptic of the science saying the Earth is warming and we’re causing it.
Tapper: “Sen. Rubio, Ronald Reagan’s secretary of state, George Shultz, reminds us that when Reagan was president he faced a similar situation to the one that we’re facing now. There were dire warnings from the mass consensus of the scientific community about the ozone layer shrinking. Shultz says Ronald Reagan urged skeptics in industry to come up with a plan. He said, ‘Do it as an insurance policy in case the scientists are right.’ The scientists were right. Reagan and his approach worked. Secretary Shultz asks, ‘Why not take out an insurance policy and approach climate change the Reagan way?’ “
Rubio: “Because we’re not going to destroy our economy the way the left-wing government that we are under now wants to do. We’re not going to. …”
Tapper: “I’m citing (Republican) George Shultz.”
Rubio: “Well, and I don’t — he may have lined up with their positions on this issue. But here is the bottom line. Every proposal they put forward are going to be proposals that will make it harder to do business in America, that will make it harder to create jobs in America. … Maybe a billionaire here in California can afford an increase in their utility rates, but a working family in Tampa, Florida, or anywhere across this country cannot afford it.”
The obvious irony: Florida, Rubio’s state, is among the most vulnerable to rising seas, which are associated with the increase in global temperatures caused by humans. A recent study found that if we burned all available fossil fuels, Florida would be almost completely underwater.
Rubio: “Jake, you … called me a denier. …”
Tapper: “I called you a skeptic.”
Rubio: “OK, a skeptic. You can measure the climate. You can measure it. That’s not the issue we’re discussing. Here is what I’m skeptical of. I’m skeptical of the decisions that the left wants us to make, because I know the impact those are going to have and they’re all going to be on our economy. They will not do a thing to lower the rise of the sea. They will not do a thing to cure the drought here in California. But what they will do is they will make America a more expensive place to create jobs.”
From that exchange, maybe you get a sense of how difficult it is to answer reader Randy McNamara’s question about where these presidential candidates stand on climate change. As the science about climate change become abundantly clear — the climate is warming, with potentially disastrous consequences, and human fossil fuel emissions are the main cause — U.S. presidential hopefuls have gotten better at dodging attempts to classify them. It seems none wants to be labeled a “denier” or a “skeptic,” even if their policies suggest otherwise.
Rubio, who does acknowledge climate change is happening, actually has been very clear in the past. “I do not believe that human activity is causing these dramatic changes to our climate the way these scientists are portraying it,” he told ABC’s Jonathan Karl in 2014. Other candidates have made similar, anti-science statements and then later tried to soften their stances. “The concept of global warming was created by and for the Chinese to make U.S. manufacturing noncompetitive,” Donald Trump tweeted in November 2012. He later told Tapper on CNN’s “State of the Union” that the tweet was meant to be “sarcastic.” But Trump also told Tapper he is “not a huge believer in the global warming phenomena. …”
This stuff is exhausting, right?
There are several candidates — among them Democrats Hillary Clinton, Martin O’Malley and Bernie Sanders as well as Republican Lindsey Graham — who have clearly stated that they acknowledge the reality of climate science and (crucially) would work to curb fossil fuel emissions. “When 90% of the doctors tell you you’ve got a problem, do you listen to the one?” Graham told CNN’s Dana Bash on “State of the Union” in June. “At the end of the day, I do believe that the CO2 emission problem all over the world is hurting our environment. But the solution is a pro-business solution to a lower-carbon economy.”
I’d encourage the others to make their positions that clear.
And I’d ask journalists to continue to push, as Tapper did Wednesday, for more-specific statements on whether these candidates believe humans are causing climate change by burning fossil fuels, and, if so, what would they do about it. The American public, including McNamara, our reader in San Francisco, deserves a much higher level of discourse on this crucial topic.
The CNN Library contributed to this report.
Question: Who are the 97% of scientists who believe climate change is caused by people?
From: Mark D., Raleigh, North Carolina
Answer: Brandon Miller, meteorologist, CNN International
Date: September 11
We hear the term “scientific consensus” bantered about a lot when discussing climate change, and the 97% number — which refers to the percentage of active climate scientists who believe people are causing climate change by burning fossil fuels — is widely cited. There’s a NASA page dissecting and touting the figure. Even President Barack Obama tweeted it. But where does this number actually come from? And who are these “97%” scientists?
First, here’s where the number comes from: There are a few studies and surveys that have found an overwhelming majority of scientists who study climate change agree that the climate is warming and that humans are responsible for it. One of the largest and most widely referenced studies was published in 2009 by Peter Doran and Maggie Kendall Zimmerman. These researchers polled more than 3,000 Earth scientists, asking them simply 1) if they believed that the planet was warming, and 2) if human activity was a significant contributor in changing the global temperature.
The scientists came from a variety of fields within Earth science (geology, oceanography, paleontology and meteorology, to name a few). Ninety percent had Ph.D.s and 7% had master’s degrees.
Nine in 10 of the scientists said global temperatures are rising and 82% said this rise is because of human activities such as burning fossil fuels and putting more heat-trapping gases in the atmosphere. But they didn’t stop there.
To gauge the view of the scientists with the most expertise, the authors also looked specifically at responses from climate science experts — meaning those who published 50% of their research in that field. For that group, the consensus was even more striking. More than 97% agreed that humans are causing the Earth’s temperature to rise.
Researchers keep getting similar results. An exhaustive review of published research on climate change was performed in a 2013 study by John Cook. The study looked at nearly 12,000 published studies over 20 years across a number of scientific, peer-reviewed journals containing the words “global warming” and “global climate change.” Of those studies, approximately one-third stated a position on whether climate change was caused by humans, and, of those who stated a position on that subject, 97.1% of the research showed humans are causing the climate to change.
Mark D., the reader in North Carolina who asked about the 97%, also wanted to know, specifically, whether it’s fair to say climate scientists have a bias … simply because they’re climate scientists.
It’s an interesting point, but it’s worth noting that science is dedicated to independent thinking. Scientists test, replicate and question their hypotheses. And, perhaps counterintuitively, there’s actually an incentive for them to try to disprove deeply held scientific theories.
They haven’t been able to do that for climate change.
“When people say scientists promote climate change to get grant money, it is an immediate sign they do not understand how grants are funded,” Marshall Shepherd, director of the Atmospheric Sciences program at the University of Georgia, and publisher of research studies on climate change, wrote in an email. “It would actually be in the best interest of scientists to say to a funding source, ‘We don’t know if human-caused climate change is happening, so fund us to figure it out.’ “
Scientists are trying to question our understanding of this subject, and science is all about cataloging ongoing discovery. But our very best understanding of the science overwhelmingly indicates that the climate is changing and that humans likely are to blame.
That’s shown both in the research and among the views of experts in climate science.
To wrap up, consider this: More than 200 scientific associations from all over the world, including the U.S. National Academy of Sciences, the World Meteorological Organization and the U.N. Intergovernmental Panel on Climate Change, all support this consensus.