Democratic presidential nominee Joe Biden excoriated President Trump on Monday over his environmental record as wildfires continued to burn through much of the West and as the president used a trip to California to question the scientific consensus that climate change is a leading cause of the devastating blazes.

Biden said during a speech in Wilmington, Del., that the “undeniable, accelerating, punishing reality” of global warming was playing out in the wildfires and hurricanes that have marked the end of summer, arguing it is a problem that “requires action, not denial.”

Across the country in California, Trump sought to pin the blame for the fires on another culprit — forest management — while shrugging off warnings that human-caused climate warming will continue to make Western states a tinderbox with annual fires that destroy communities.

“It will start getting cooler. You just watch,” he said during a briefing with state and local leaders in McClellan Park, Calif.

The dueling appearances injected the issue of climate change squarely into a presidential campaign that has been dominated by the coronavirus pandemic, a faltering economy, racial justice protests and questions about which candidate has the character to lead. But the warming of the planet and its impact on daily life are now difficult to ignore, with millions of acres burning in California, Oregon and Washington state, leading to dozens of deaths, tens of thousands displaced and skies filled with a smoky, dangerous haze that blocks out the sun.

Biden called Trump a “climate arsonist” who had belittled the factors worsening the wildfires, and he likened the president’s stewardship of natural disasters to his handling of the pandemic and racial tensions across the country that flared this summer following police shootings of Black people.

“Donald Trump’s climate denial may not have caused these fires and record floods and record hurricanes,” Biden said Monday. “But if he gets a second term, these hellish events will continue to become more common, more devastating and more deadly.”

While heavily criticizing the president for what he called a lack of vision, Biden stuck to promoting climate policies with wide support and avoided addressing politically thorny topics like the Green New Deal many liberal activists have demanded.

Not long after Biden’s remarks in Delaware, California leaders focused on climate change during their briefing with Trump. Gov. Gavin Newsom (D) made it clear that he wasn’t seeking a confrontation with the president on the topic but said that “we come from a perspective, humbly, where we submit the science is in, and observed evidence is self-evident, that climate change is real and that is exacerbating this.”

Wade Crowfoot, the secretary of the state’s Natural Resources Agency, pushed the issue more aggressively after the president dismissed concerns that temperatures were on the rise, telling Trump, “I wish science agreed with you.”

The president responded: “Well, I don’t think science knows, actually.”

Trump’s assertion ran contrary to the scientific consensus that human-caused climate change has undoubtedly made the West hotter and drier, enabling more fires to behave in extreme, unpredictable ways.

Warm temperatures dried out vegetation during a record-shattering heat wave — the second since mid-August. Recent blazes exploded in size during an outbreak of strong winds that simultaneously hit the Cascades, Sierras and coastal mountain ranges. Gusts pushed flames down canyons, through campgrounds, past highways and into neighborhoods.

Studies have documented an increase in acres burned in large fires across the West because of global warming, and projections show trends toward hotter and drier conditions that will leave the region more susceptible to massive blazes.

But Trump’s dismissal was consistent with his past remarks calling climate change a “hoax.”

The president has also continued to solely blame mismanaged forests in the Western states for the intensifying wildfires. He claimed Monday that he had spoken to a foreign leader — whom he did not name — who insisted that his or her country has “trees that are more explosive [than] they have in California, and we don’t have any problem because we manage our forests.”

“When trees fall down, after a short period of time they become very dry — about 18 months — they become very dry. They become, really, like a matchstick,” Trump said. “And they get up — you know, there’s no more water pouring through, and they become very, very — well, they just explode.”

Indeed, the management — or mismanagement — of forests across California and elsewhere has resulted in a massive amount of fuel on the ground that has only intensified and deepened the reach of the wildfires. And ever-encroaching developments, as more and more neighborhoods are built on fire-prone land, certainly have played a role in the current devastation.

But fire ecologists say no amount of “clearing” in the forests could have prevented this year’s disasters. In many cases, research shows, management practices such as salvage logging actually exacerbate fire susceptibility.

Tim Ingalsbee, a retired wildland firefighter and a certified fire ecologist, pointed to the Holiday Farm Fire, a blaze near his home in Eugene, Ore., that has burned through thousands of acres of an industrial tree plantation. “This area has experienced the maximum timber management possible,” he said, “and has made these lands even more flammable than the native forests.”

Newsom told the president that state officials “have not done justice on our forest management.” The governor also noted to Trump that 57 percent of the forest land in California is owned by the federal government, which bears a major responsibility for keeping the forests cleared.

The wildfires unfolding in the West are what climate scientists call a compound disaster, in which more than one extreme event takes place at the same time across a varied geography. While researchers have warned that compound disasters are an inevitable result of climate change, few would have predicted that the simultaneous, rapidly expanding fires spanning the entire West Coast would happen so soon.

“Everything we didn’t do in the past is now coming due in the present,” said Char Miller, a professor of environmental analysis and history at Pomona College, east of Los Angeles.

Trump — who rarely hesitates to weigh in on the topic du jour — had stayed mum about the wildfires until a tweet on Friday. Asked in Sacramento why it took him three weeks to visit California, Trump dismissed it as a “nasty question” and said he had promptly issued a disaster declaration for the state.

On Monday, Biden vowed to meet the threat of climate change aggressively as president, by setting new fuel-efficiency standards, spurring more electric-vehicle use and creating a climate corps to make the country less vulnerable to wildfires and floods.

This summer, Biden rolled out a $2 trillion plan that would treat climate change as one of the central threats facing the nation. Its goals include eliminating carbon pollution from the electric sector by 2035, rejoining the Paris climate accord, making huge investments in renewable energy, and creating incentives for more energy-efficient cars, homes and commercial buildings.

In contrast, the Trump administration has aggressively rolled back scores of environmental regulations, including weakening federal fuel-efficiency standards for automobiles and easing curbs on emissions from the nation’s power plants. The administration has overhauled a bedrock law meant to give ordinary people a say in projects that threaten to pollute their neighborhoods. It has sought to expand offshore drilling, as well as oil and gas exploration in previously off-limits places such as the Arctic National Wildlife Refuge.

The administration recently tapped an academic who has long questioned the scientific consensus on global warming to help run the National Oceanic and Atmospheric Administration (NOAA), the agency that produces much of the climate research funded by the U.S. government.

Even as the president has referred to himself as a “great environmentalist,” he has rejected growing calls to act on the economic and security threats posed by a warming climate. He has promoted the fossil fuel industry, criticized renewable technologies such as wind power and vowed to withdraw the United States later this year from an international effort to cut greenhouse gases that fuel global warming.

Lawmakers from the states hit hardest by the fires have pressed the administration for swift emergency disaster declarations to free up federal funds that have been approved by the White House, although aides said Congress is likely to make more specific requests once the scope of the damage becomes more clear.

There is no immediate need for funding action from the Hill, according to congressional aides, because the federal disaster relief fund has sufficient money and will be automatically replenished in a stopgap government funding resolution that has to pass before the end of this month.

“In the past, this White House has been certainly willing to use emergency funds to carry out their agenda,” said Sen. Ron Wyden (D-Ore.). “I hope that won’t be the case now.”

Erica Werner, Karoun Demirjian and Sarah Kaplan in Washington and Sean Sullivan in Wilmington, Del., contributed to this report.