New York City Mayor Bill de Blasio, Rep. Tim Ryan (Ohio), former HUD secretary Julian Castro, Sen. Cory Booker (N.J.), Sen. Elizabeth Warren (Mass.), former congressman Beto O’Rourke (Texas), Sen. Amy Klobuchar (Minn.), Rep. Tulsi Gabbard (Hawaii), Gov. Jay Inslee (Wash.) and former congressman John Delaney (Md.) participate in a Democratic primary debate in Miami on Wednesday. (Wilfredo Lee/AP)

Jay Inslee, the governor of Washington state, has said climate change is the “driving motivation” for his presidential campaign; some of his opponents agree, particularly after an April CNN/SSRS poll found that 82 percent of Democrats and Democratic-leaning voters described the issue as “very important.” One of these candidates will face off in the general election against a president who ran on the assurance that “I believe in clean air. Immaculate air. But I don’t believe in climate change.” This month, President Trump falsely asserted that “the United States right now has among the cleanest climates there are, based on all statistics, and it’s even getting better.” Vice President Pence won’t acknowledge the scientific consensus that climate change is a threat to our country.

Clearly, whichever Democrat snags the nomination will have a hard time selling the urgency of this problem. But many of the candidates have been able to skate by so far without offering many specifics about what they’d do or how they’d do it, including at the NBC News debates this past week, where the climate was a relatively minor concern. The Washington Post asked seven climate experts and scientists: In a presidential debate focused entirely on this subject, what would they ask the candidates?

— David Swerdlick

Carol M. Browner

Question: If Republicans still controlled at least one house of Congress when you took office, what would you be prepared to do on Day One, under existing executive authority, to set the country on a path to address the existential threat posed by climate change?

The background: The Trump administration and its Republican allies in Congress have taken extreme measures to block climate action. They are rolling back pollution rules on emitters from cars to power plants. Environmental Protection Agency data shows there were 15 percent more unhealthy air days in the United States during the first two years of the Trump administration than the four years prior.

Carol M. Browner, a former Environmental Protection Agency administrator, is chairwoman of the board of directors of the League of Conservation Voters.

Katharine Hayhoe

Question: How do you propose to move past the political posturing and rampant disinterest to persuade legislators and elected officials across the spectrum that climate action is not about defending a political position but about ensuring a safe future for ourselves and our children?

The background: A thermometer doesn’t give us a different number depending on how we vote. Yet today, a reliable predictor of whether we agree with the simple facts — climate is changing, humans are responsible, the impacts are serious, and we need to act now — isn’t how much we know about the science but rather where we fall on the political spectrum. In recent days, Oregon’s Democratic governor sent law enforcement officers to round up Republican state senators who’d fled the capitol, denying a quorum for a vote on a climate-change bill.

Katharine Hayhoe is a professor of political science and the director of the Climate Science Center at Texas Tech University.

Bill Nye

Question: How would you persuade climate deniers in Congress to help you address the problem? Or how would you work around the deniers?

The background: U.S. inaction with respect to climate change is due almost entirely to fossil-fuel-industry propaganda and lobbying efforts. If Americans hope to achieve electrified ground transportation, less-harmful agriculture, acceptable nuclear power, carbon-capturing technologies and a renewable-energy electrical grid, we’ll have to surmount our us-vs.-them political situation. My vote is going to the candidate who has a plan to work with or around the deniers in Congress. The Green New Deal is one possible way — a job-creating industrialist policy that also lessens our reliance on fossil fuels. The phrase “reaching across the aisle” is charming, but when it comes to climate change and renewable-energy policies, so far, scientifically literate lawmakers have been ineffective against willfully irresponsible ones. A canny president must find a way to bring these people along with his or her climate aims.

Bill Nye is a science educator and mechanical engineer. He hosts the podcast “Science Rules!” and is the creator of the Emmy-award winning series “Bill Nye the Science Guy.”

Beverly Wright

Question: If elected, would you join action on climate change with action to achieve environmental justice in communities of color burdened with racially disproportionate toxic pollution? How would you get this done?

The background: About half of greenhouse gas emissions in the United States come from industrial facilities and power plants. These facilities are disproportionately located in and near African American communities that don’t meet air quality standards; residents suffer disproportionately severe health problems such as asthma attacks and cancer as a result. Many of the same communities are also vulnerable to the climate-change effects of stronger hurricanes, more intense heat waves and increased flooding. Yet many of the climate-change proposals put forward by candidates don’t address environmental racism and the racial disparities in disaster prevention and recovery.

Beverly Wright is a sociologist and the founder and executive director of the Deep South Center for Environmental Justice.

Ann Carlson

Question: A number of cities around the country have sued oil companies for damages they are already experiencing as a result of climate change, such as sea level rise, wildfires, flooding, hurricanes and heat waves. Major oil companies want immunity from these lawsuits in exchange for agreeing to support a carbon tax. Do you support exempting oil companies from climate lawsuits in exchange for a carbon tax?

The background: These cities are suing oil companies under nuisance law (I’ve provided pro bono legal advice for several of them). They argue that oil companies have emitted a huge percentage of the total greenhouse gases in the past ­half-century, that they have known about the harms and causes of climate change for decades, and that they have concealed those harms and funded a campaign to convince the public that climate change is fake. The oil companies argue that climate change shouldn’t be solved in the courts and that the economic benefits of fossil fuels outweigh any environmental harms.

Ann Carlson is the Shirley Shapiro professor of environmental law and the co-director of the Emmett Institute on Climate Change and the Environment at UCLA.

Nick Pyenson

Question: What strategies do you have for communicating the scale of the issue and the unique opportunity afforded by making changes right now? How do you turn the facts of planetary change at geologic magnitudes into a story with heart and urgency that will move voters?

The background: Sometimes climate change feels abstract — a melting Arctic or a species extinction in a far-off place seems untethered to kitchen table concerns for most voters. Sometimes thinking about experiences within the scale of one lifetime helps (“I’ve never seen this much rain”), but the crux is a transgenerational issue: At the moment, we’re playing for many future generations, and we don’t have much time on the clock.

Nick Pyenson is a research geologist, curator of fossil marine mammals at the Smithsonian Institution’s National Museum of Natural History and the author of “Spying on Whales: The Past, Present, and Future of Earth’s Most Awesome Creatures.”

Kristie L. Ebi

Question : Government agencies have supported limited research to better understand the health risks of climate change or to identify actions to prepare for its risks. How will your administration ensure the health and well-being of Americans in a changing climate?

The background: Climate change alters our exposure to heat waves, floods, droughts and other extreme events; vector-, food- and waterborne infectious diseases; declines in the quality and safety of air, food and water; and stresses to mental health and well-being. According to a new survey, two-thirds of Americans believe climate action will ease health effects and improve well-being. Yet the shortage of investment in health-specific research and development is harming Americans by failing to anticipate the health challenges of climate change. In 2018, the National Institutes of Health only commited 0.04 percent of its annual budget to addressing climate change.

Kristie L. Ebi is a professor of global health and environmental and occupational health sciences at the University of Washington.

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