With three Western states ablaze and a hurricane bearing down on the Gulf Coast, Democratic presidential nominee Joe Biden assailed President Donald Trump for science denial Monday in an unprecedented move by a candidate to shift a U.S. presidential campaign’s focus to climate change.

After weeks of Trump running his campaign on a “law and order” theme and arguing that a Biden presidency would make Americans unsafe, Biden turned the tables on Trump, as the president’s plane descended through the smoke-filled skies of Sacramento to visit the capital of the state hardest hit by the unfolding wildfire disaster.

Biden argued that Trump’s inaction and dismissal of science has left Americans vulnerable to climate catastrophe, just as it heightened risks from the coronavirus pandemic.

“He fails the most basic duty to a nation—he fails to protect us,” said Biden in a speech outdoors near the Delaware Museum of Natural History in Wilmington. “From a pandemic, from an economic freefall, from racial unrest, from the ravages of climate change—it’s clear we’re not safe in Donald Trump’s America.”

The speech by Biden and its timing ensured that once Trump touched down in California, he would get the kind of direct questioning on climate change he seldom has to face. And in his brief public parleys with reporters and California state officials, the president showed no inclination to back away from his previous climate science denial.

Trump repeated an argument he has leaned on during past wildfires—that the blazes are due to inadequate forest floor maintenance. “When trees fall down after a short period of time they become very dry—really like a matchstick… and they can explode,” he said. “When you have dried leaves on the ground it’s just fuel for the fires.”

Trump is correct that forest management is important for wildfire prevention, but most of California’s 33 million acres of forest—57 percent—is owned and managed by the federal government. California state authorities, whom Trump often blames for poor forest management, own and manage only 3 percent. Private landowners, including industrial timber companies, own the remainder.

Gathered around a horseshoe table with California Gov. Gavin Newsom and state and federal emergency management officials on Monday, Trump balked at the suggestion that climate change was a primary cause behind the fires. “It will start getting cooler,” said Trump. “Just watch. I don’t think science knows actually.”

Biden argued that the president has a disdain for science that is making citizens less safe—including in the all-important election battleground of the suburbs, where Trump has sought to stoke fear about violence and racial integration.

“If we have four more years of Trump’s climate denial, how many suburbs will be burned in wildfires, how many suburban neighborhoods will be flooded out, how many suburbs will be blown away in superstorms?” Biden asked during a week when the Western fires killed two dozen people. “If you give a climate arsonist four more years in the White House, why would anyone be surprised if we have more of America ablaze? If you give a climate denier four more years in the White House, why would anybody be surprised when more of America is under water?”

Biden this summer unveiled the largest-ever climate change proposal by a presidential candidate—a $2 trillion “Build Back Better” initiative that would seek to create jobs and invest in minority communities by building infrastructure to support a clean energy transition and greater resilience to climate impacts. But Biden’s speech Monday was the first time that he—or any presidential candidate—took on an opponent over climate policy failures based on events in real time.

Scientists typically avoid attributing any one wildfire, flood or hurricane to climate change, but the evidence is that climate change is making natural disasters more frequent and more severe. And as mega-fires turned skies amber and 87 large fires consumed 4.6 million acres in California, Oregon and Washington State—an area bigger than Connecticut—Biden said that the United States was witnessing an extraordinary manifestation of the climate change that science has long projected due to the emissions of fossil fuels.

“Donald Trump’s climate denial may not have caused the wildfires, but if he gets a second term, these hellish events will become more common, more devastating and more deadly,” Biden said.

Trump’s visit to McClellan Park, a former Air Force Base that’s now home to the state’s Office of Emergency Services, marked his first visit to California since the latest wave of wildfires began in the state in mid-August. Initially, when asked by a local reporter if there was a climate change issue in California, Trump deflected.

“You’ll have to [ask] your governor that question,” Trump said. “I don’t want to step on his toes.”

Newsom did talk about climate change, while seeking diplomatic detente with Trump.

“We’ve known each other too long and the working relationship I value,” Newsom said. “We feel very strongly the hots are getting hotter, the dries are getting dryer. Something has happened to the plumbing of the world and we come from a perspective, humbly, that we assert the science that climate change is real. Please respect the difference of opinion out here with respect to the fundamental issue of climate change.”

Trump responded, “Absolutely.”

But Trump has no climate plan, and he has abandoned the climate policies instituted by his predecessor. The heart of Trump’s environmental agenda has been to roll back more than 100 pollution regulations, either directly or indirectly clearing the way for greatly increased emissions of greenhouse gases, at a time when science says the world needs to be on a track toward net-zero emissions.

Biden made clear this week that he intends to keep climate from  being overshadowed by the other crises that are at the top of voters’ lists of concerns. Instead, he is drawing connections among  climate and the coronavirus and racial injustice, and casting Trump’s dodging of the climate question as evidence that he has shirked responsibility. Noting that Trump had talked about withholding emergency funds from California, Biden said, “These interlocking crises of our time require action, not denial. They require leadership, not scapegoating. It requires a president to meet the threshold duty of the office—to care.”

He added, “Hurricanes don’t swerve to avoid red states or blue states. Wildfires don’t skip towns that voted a certain way. It’s not a partisan phenomenon. It’s science, and our response should be the same—grounded in science.”