If a Donald J. Trump administration acts on the president-elect's view that global warming's a "hoax," the consequences of the presidential election may echo for generations. When he's sworn into office in January, Trump becomes the only leader of a major industrialized country to deny the existence of human-caused global warming.

This is a first for the U.S., considering that even former president George H.W. Bush signed a climate change agreement in 1992, when the issue was just emerging. Presidents Clinton, George W. Bush and Barack Obama have all pursued reductions to emissions of planet-warming greenhouse gases, such as carbon dioxide.

In the lead-up to the election, environmental leaders and climate scientists issued apocalyptic warnings of what a Trump presidency would do to efforts to rein in global warming, given that the Paris Climate Agreement only just went into effect on Nov. 4, and is still fragile.

September 2016 global temperature anomalies. Image: NASA giss

Now, some of these same people are shellshocked, but remain resolved to opposing attempts to slow the pace of emissions cuts, which climate science says is a crucial factor in determining how much the world will warm in the next several decades.

No time to waste

The U.S. and the world can't afford to stall or slide backwards on climate progress, according to scientific research. Studies show climate change proceeding faster than anticipated, with a narrowing window to act in order to forestall the worst impacts of global warming, such as a catastrophic increase in sea levels.

In fact, a recent U.N. report showed that if we are to have any hope of meeting the Paris Agreement's goal of limiting global warming to under 2 degrees Celsius, or 3.6 degrees Fahrenheit, below preindustrial levels, emissions cuts need to become more ambitious.

Global carbon dioxide levels surpassed 400 parts per million for the first time in 2016. Image: Scripps institution of oceanography

The Obama administration committed to reducing U.S. greenhouse gas emissions by 25 to 28 percent below 2005 levels by 2025, and it's expected to lay out a decarbonization plan by midcentury during the ongoing U.N. climate talks in Marrakech, Morocco.

However, to achieve these cuts, the Environmental Protection Agency's (EPA) regulations on coal-fired power plants, known as the Clean Power Plan, would need to survive court challenges and be implemented by a supportive White House.

During the campaign, Trump made clear he would dismantle those regulations and others.

A Trump White House will have few checks on its power given that Republicans hold both houses of Congress, meaning that there could be significant rollbacks of EPA regulations and climate-related executive orders that could have ramifications beyond a single presidential term.

A slowdown or halt in U.S. emissions cuts would shift the climate math in favor of more severe global warming impacts.

Republican presidential candidate Donald Trump acknowledges the crowd after delivering an energy speech in Bismarck, N.D. in May 2016. Image: Charles Rex Arbogast/AP

Leading environmental activist and journalist Bill McKibben emphasized that issue when reached on Wednesday, telling Mashable that "... The results of this election may eventually be measured in inches or feet of sea level rise."

"Our job is to limit the damage, a harder job today than yesterday, but it wasn't easy then either. Since physics is indefatigable I guess we better be too," McKibben, a founder of the environmental group 350.org, said.

Prominent climate scientist Hans Joachim Schellnhuber, who leads the Potsdam Institute for Climate Impact Research in Germany, said the ramifications for global climate action are dire.

The climate system doesn't forget, and it doesn't forgive

"The U.S. de-elected expertise and will likely show a blockade mentality now, so Europe and Asia have to pioneer and save the world," Schellnhuber said in a statement. "Formally leaving the Paris Agreement would take longer than one Presidential term, yet of course the U.S. could simply refuse reducing national emissions which would mean a de facto exit out of international climate policy."

Global five-year average temperature anomalies, relative to 1961-1990 for 2011 to 2015. Image: WMO

He went on to say that the U.S. is "one of the world's biggest economies, and even just four years of unbridled emission staying in the atmosphere for many hundreds years would make a substantial difference. The climate system doesn't forget, and it doesn't forgive."

Environmental groups unite

Trump's election may help unify the environmental movement in opposition to the White House, making opposition to new fossil fuel projects, anti-regulatory moves and other potential actions more intense and effective.

"This is an undeniable tragedy, but of course as organizers, our job is try and forge some sort of way ahead," said Jamie Henn, a spokesman for 350.org, in an email on Wednesday morning.

Henn says the group will push the Obama administration to take fossil fuel projects currently undergoing review off the table, and then focus on flexing its muscles to oppose Trump's moves.

"We're going to need a massive movement to defend the progress we've made"

"We're going to focus on building power. No matter how this plays out, we're going to need a massive movement to defend the progress we've made and look for openings where we can," he said.

"We've shown the ability to hold up fossil fuel projects on the ground. States can still make progress. Other countries will need to charge ahead," Henn added.

Erich Pica, president of the environmental group Friends of the Earth U.S, echoed these sentiments in a statement released on Wednesday.

"We will have to harness our new energy, join together, and use every strategy possible to fight against hate and greed and environmental destruction," said Pica.

"While I wish we had a different fight before us, we must fight the one presented to us. The future of our country and planet depends it."

Business interests could lobby Trump to see the light

Then again, the Trump campaign's opaque policy stances may leave the future administration with enough wiggle room to accommodate some of the environmentalist's concerns, as well as listening to a more influential constituency: major businesses.

Jim Davis kayaks through waters flooding Bowen's Wharf after Hurricane Sandy in historic Newport, R.I. in 2012. Image: Dave Hansen/Newport Daily News/AP

Business leaders who are moving forward with cutting their own emissions and planning for a future in which climate regulations are in place might find it in their interest to stage a climate intervention of sorts to persuade Trump to alter his policy positions.

For example, tech giants such as Apple, Microsoft, Amazon and Facebook have been moving aggressively to cut their emissions and energy use, with many of them building wind and solar power projects.

Financial firms and even oil companies have started hedging their bets on climate regulation, realizing it could impact their bottom line if they don't take it into account.

It's also possible, though not likely, that he will reevaluate his position on global warming once he gets into the office and learns more about the science and economics of the issue.

"Trump has promised to rebuild America and create jobs across the rust belt and beyond. Perhaps he'll see the light and call for a clean energy revolution to revitalize our manufacturing sector? Who knows?" Henn, of 350.org, said.

"For now the future looks pretty dark."