And that means that Democratic candidates are talking a lot more about what they will do to curb global warming. To find out exactly where the candidates stand on climate-related issues, The Post’s John Muyskens and Kevin Uhrmacher waded through 23 candidates’ public statements and voting records, as well as sending climate-change questionnaires to every campaign.

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The result is this comprehensive overview. They found each candidate agrees the issue of rising temperatures is something the next president needs to address. But differences abound between the candidates on how to rein in heat-trapping pollution being released by humans.

Here are the five most interesting answer from our survey:

Jay Inslee on nuclear energy: The Democratic field is split on whether nuclear power should be part of any solution to climate change. It's the largest source of low-carbon electricity in the country. But building more reactors has proven in most cases to be cost-prohibitive. And accidents like Three Mile Island still weigh heavily on the minds of many left-leaning Americans.

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At one end of the debate are Sens. Michael Bennet (Colo.) and Cory Booker (N.J.), who led Congress in passing legislation easing the way for the construction of more reactors. At the other end is Bernie Sanders (I-Vt.), whose campaign told The Post he would stop issuing nuclear power plant license renewals in an effort to phase out the energy source entirely.

Then there is Jay Inslee, who has launched a campaign devoted to the issue of climate change and is trying to find a middle ground on nuclear power.

“We must move to a carbon-free power sector, so I would not take any zero-emission sources of power generation off the table,” the Washington governor told The Post. “However, in order to support new development of nuclear energy, we would first have to solve critical challenges that do not yet have solutions.”

These issues include improving the safety and lowering the cost of construction of reactors. He also “most critically” wants to find “a stable long-term plan” for storing the thousands of tons of nuclear waste produced every year.

Bernie Sanders on a carbon tax: For years, the Vermont senator was one of the biggest proponents in Congress of a carbon tax — forcing polluters to pay for climate-warming emissions in a way many economists have praised as cost-effective.

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He introduced legislation to place a fee on the emissions of carbon dioxide and methane, going so far as to write in the Huffington Post that a carbon tax “must be a central part” of any plan to address carbon pollution. The 2014 blog post was titled “Why We Need a Carbon Tax.”

Now as scientists for the United Nations warn the window for stopping the world from warming over 2 degree Celsius is closing, some left-wing activists have grown more skeptical of a carbon tax, arguing it is too little, too late.

Sanders, too, has changed his tune a bit, no longer casting a carbon tax as a linchpin to his climate plan. But he still isn’t entirely ruling it out either.

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“[I]f we are to solve the issue of climate change, a price on carbon must be part of a larger strategy and it must be formulated in a way that actually transitions our economy away from fossil fuels and protects low-income families and communities of color,” a campaign spokesman told The Post.

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Beto O’Rourke on banning fossil fuel exports: In 2015, congressional Republicans and President Obama made a deal to lift a 40-year-old ban on exporting oil in exchange for extending tax breaks for wind and solar energy.

A number of current candidates, including Sens. Elizabeth Warren (Mass.) and Amy Klobuchar (Minn.), voted in favor of the compromise. So too did Cory Booker, even as the New Jersey senator said at the time it was “disappointing and frustrating” to see the repeal of the oil export ban included in a broader $1.1 trillion spending package.

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But it is Beto O’Rourke who is in the toughest position of all on this issue.

The former congressman from oil-rich Texas voted in favor of a standalone bill lifting that oil-export ban, at the time calling it an “outdated policy” that prevented U.S. allies from becoming "less dependent on energy from other volatile areas in the world.”

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Now O’Rourke finds himself in the tricky position of defending that record. A campaign spokesman told The Post that O'Rourke “would take executive action on day one to require any federal permitting decision to fully account for climate costs and community impacts.”

But his campaign did not indicate where he currently stands on the export question.

Steve Bullock on banning fossil-fuel leasing: Between 2005 and 2014, nearly a quarter of all U.S. carbon dioxide emissions came from the burning of oil, natural gas and coal harvested from federally controlled lands. With the stroke of a pen, the next president could stop issuing any new leases for the further extraction of fossil fuels.

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With that realization, more than a dozen Democratic candidates have committed to putting in place such a moratorium should they become president. But Steve Bullock has distinguished himself as the only contender so far to publicly oppose such a ban.

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“I believe other policy measures can be used to appropriately transition our current framework of federal leasing and to better reflect the social cost of greenhouse gases from extraction,” Bullock told The Post.

It’s a consistent position for the Democratic governor of the coal-producing state of Montana. In 2016, he opposed Barack Obama's half-step toward a fossil-fuel moratorium when the president stopped new coal leasing on federal lands.

Joe Biden on the Green New Deal: The single climate-related proposal that has animated — and divided — the 2020 field the most so far is the Green New Deal.

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All but one of the seven U.S. senators running for president co-sponsored the non-binding resolution, which calls for a program to drastically reduce greenhouse gas emissions all while increasing access to healthcare and high-quality jobs. Other candidates, such O’Rourke and Wayne Messam, mayor of Miramar, Fla., have praised the ambitions of the Green New Deal while stopping short of formally endorsing the idea.

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But Joe Biden remains the biggest enigma of them all. The former vice president has cast himself as an ardent environmentalist (“There’s been nothing middle of the road about my record dealing with the environment,” Biden told reporters in New Hampshire after Reuters reported he was seeking a "middle road" approach on climate.) But his campaign has not yet announced any concrete energy proposals.

The former vice president, who did not respond to our survey but is expected to announce his climate plan in the coming weeks, was the only 2020 Democratic candidate we put in the "unclear/no response" category on the question of the Green New Deal.

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So far, the calculated silence appears to be paying off. At the moment, Biden sits atop most polls for the Democratic nomination.

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Read the rest of the Post's report on where 2020 Democrats stand on climate change here.

POWER PLAYS

Speaking of 2020 contenders: During the convention of California Democrats, former Colorado governor John Hickenlooper was booed for criticizing socialism, saying it was “not the answer,” and again booed for expressing concern about the Green New Deal proposal, among other ideas. “We shouldn’t try to tackle climate change by guaranteeing every American a government job," he said, drawing jeers from the crowd. "As the Democratic Party we have to create a vision for this country. I want to give Americans a reason to look forward to tomorrow … I will tackle climate change with a laser focus.”

— Corn wars: The Trump administration moved to lift restrictions on ethanol fuel, the latest decision that could help farmers that have been impacted by the administration’s tariffs.

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What the Environmental Protection Agency did: On Friday, the agency said it will lift a summertime ban on selling fuel containing a 15-percent blend of ethanol, allowing the mix to be sold year-round. Growers of corn, from which ethanol is derived, have long criticized the seasonal ban for hampering the sale of the alternative fuel. “President Trump delivered on his promise to Iowans," Sen. Joni Ernst (R-Iowa) said in response to the EPA decision.

But: Ethanol-blended fuel evaporates at a higher rate, and the ban during warmer months was there in the first place to reduce smog-forming emissions. Collin O’Mara, president of the National Wildlife Federation, said in a statement the move is "both illegal under the Clean Air Act and will accelerate the destruction of wildlife habitat and pollution of our air." Oil refiners, who have to blend the ethanol into gasoline in the first place, also opposed the decision.

— A secretive meeting in Switzerland: Secretary of State Mike Pompeo was expected to attend a secretive meeting at a Swiss lakeside resort this weekend — a Davos-like annual forum “in which participants agree not to reveal exactly what was said or who said it,” the New York Times reports. “On at least one subject, climate change, many of the participants are expected to have radically different views than Mr. Pompeo. In early May, the American secretary, speaking at a meeting of the Arctic Council in Finland, praised the changes caused by the melting of ice in the Arctic Circle,” per the report.

— The latest on the impasse over disaster funding: Last week, House Republicans again blocked a $19.1 billion disaster-aid bill late last week that has even been backed by the president. Democrats looked to pass the measure via unanimous consent while they were out of session, but freshman Rep. John Rose (R-Tenn.) objected. He said the bill should be debated rather than advanced during a recess, The Post’s Erica Werner reported. Before Rose, his colleagues Chip Roy (R-Tex.) and Thomas Massie (R-Ky.) stymied the disaster aid in a similar way in recent days.

THERMOMETER

— Relentless weather has meant trouble for farmers: Normally, by the end of May, 90 percent of fields have been planted in the 18 states that produce the majority of corn crop in the country. But this year, data from the Agriculture Department says just 58 percent of the crop is in the ground. For soy, 66 percent of the crop has usually been in the ground by this point, but just 28 percent has been planted this year.

Why? It's in part because of unrelenting rainfall which has meant farmers across swaths of the Midwest “have rarely seen days dry enough to work, leading to what agricultural experts are calling a historically delayed planting season that could exacerbate the economic and personal anxieties brought on by a multiyear slump in farm prices and the Trump administration’s trade war with China,” The Post’s Katie Mettler reports.

A long-term worry: “The greatest concern may be what happens if the Midwest suffers more such severe floods and rains in future growing seasons,” the New York Times reports. “Scientists say the increase in average surface and air temperatures over time is likely to lead to increasingly extreme precipitation patterns … The question is whether, and how much, farmers are able to adapt to what seems likely to become the new normal, according to Jim Mintert, director of the center for commercial agriculture at Purdue.”

— Coyote conundrum: Government hunting programs that essentially eliminated red and gray wolves created an unintended problem — a coyote population that has exploded, surging in the east after expanding from their original habitat in the west, The Post’s Darryl Fears reports. Wildlife officials have tried to reduce the coyote populations, but the animals have so far proved more resilient. “It is a textbook example of what the recent United Nations biodiversity report said: Humans are creating chaos for wildlife, placing a million species in danger of going extinct,” he writes.

— ‘Unprecedented’ rollback of protected areas: A new report published in the journal Science found efforts in the United States to reduce protected areas could push other countries to do the same. The report found the rate of reductions in the United States has also spiked, “with 90% having taken place since 2000,” the Guardian reports. “Nearly all of those proposals (99%) were associated with industrial-scale development projects, including infrastructure construction and oil and gas extraction.” The study points to Trump’s decision to slash the size of the Bears Ears and Grand Staircase-Escalante national monuments as an example of the “uncertain future” of protected areas in the country. “The recent legal changes that have scaled back protections in the US are just unprecedented,” the study’s senior author Mike Mascia told the Guardian. “And they send a dangerous message to the rest of the world.”

— Atomic birth control: In sub-Saharan Africa, the tsetse fly’s toxic bite kills an estimated 3 million livestock each year. But a team of veterinarians in Senegal worked with researchers in Austria on a nuclear project funded by the United States. By sterilizing the male flies with gamma rays, scientists have exterminated nearly all of the tsetse flies in the country’s western Niayes zone, The Post’s Danielle Paquette reports. “The United States has poured about $5 million into this effort, which has squashed the number of trypanosomiasis cases down to nearly zero. It’s part of a broader push to harness nuclear energy for good that has stayed on track even as the Trump administration has sought to slash foreign aid elsewhere.”

DAYBOOK

Today

EPA administrator Andrew Wheeler speaks at the National Press Club.

Coming Up

The Senate Energy and Natural Resources Committee holds a hearing on expanded deployment of grid-scale energy storage on Tuesday.

The Senate Environment and Public Works Committee holds a nomination hearing on Tuesday.

The Senate Environment and Public Works Subcommittee on Clean Air and Nuclear Safety holds a hearing on advanced nuclear technology on Tuesday.

The House Science Committee holds a hearing on biodiversity loss on Tuesday.

The Senate Energy and Natural Resources Committee holds a nomination hearing on Wednesday.

The House Natural Resources Subcommittee on National Parks, Forests, and Public Lands holds a legislative hearing on Wednesday.

The House Science Subcommittee on Environment holds a hearing on ocean exploration on Wednesday.

The Center for Strategic and International Studies holds an event on climate preparedness on Wednesday.

th Washington Oil & Gas Forum, which will be held on Wednesday and Thursday. Sen. Ted Cruz (R-Tex.) is scheduled to give the keynote address at the 5Washington Oil & Gas Forum, which will be held on Wednesday and Thursday.

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