A pushback against President Donald Trump’s attacks on rules to protect the environment gained momentum in Denver Thursday as former vice president and climate-change sentinel Al Gore launched a three-day mobilization of activists.

“We need to demonstrate. We need to get active. People power,” Gore told a packed Colorado Convention Center crowd.

For a decade, Gore’s been presenting updated versions of his “Inconvenient Truth” narrative at Climate Reality sessions that have set to work 11,000 activists in 135 countries — people of all ages who push for action to slow climate change by cutting emissions of heat-trapping pollution.

But this 34th training — the first since Trump rose to power — drew 1,000 more applications than usual as 2,600 people from around the West vied for 972 slots in Denver.

Climate Reality leaders are vowing to fight Trump team measures from proposed EPA budget cuts to rule rollbacks “every step of the way” — including direct action tactics such as tent camps and consumer campaigns against financiers of new fossil fuel pipelines. They’re bracing for White House action expected this month against President Obama’s signature Clean Power Plan to cut U.S. carbon emissions.

“We are winning. We are going to win,” Gore said in an interview after the speech. “Large numbers of passionate grassroots activists can make all the difference.”

Heat-wave deaths and more extreme storms, combined with falling costs for clean energy, are forcing a shift off fossil fuels, Gore said.

“And this grassroots movement is advancing on multiple fronts,” he said. “The fastest growth is in interacting with elected officials, not only in the U.S. House of Representatives and U.S. Senate, but also city councils, county commissioners, state legislatures. There’s also an important branch of the activism that is focused on businesses.

“You’re seeing in the Dakota Access Pipeline, the tent camp there is now moving against Wells Fargo and other banks that are financing the build-out of this massive new pipeline infrastructure,” he said. “You’re seeing people making it clear to large consumer-based businesses that they are going to lose their business from climate-aware consumers if they don’t get with the change.”

The climate action gathering in Denver reflected environmentalist opposition ignited this week as Trump issued an order to overhaul or rescind the EPA rule that protects streams and wetlands, following efforts to roll back new rules to protect public lands and air quality.

White House officials also this week proposed EPA budget cuts by around 25 percent with a hit list including popular programs to reclaim “brownfields” industrial sites in cities and funding for state-run programs to reduce water and air pollution. And they’ve resolved to move forward on expansion of fossil fuel pipelines and coal-mining.

The EPA funding for state-led work protecting land, air and water contributed millions to Colorado’s Department of Public Health and Environment. State officials on Thursday were sizing up potential impact from air pollution-monitoring around power plants to measuring of contaminants from toxic mines and industrial spills.

“It’s too early to speculate about proposed budget cuts at the EPA and possible impacts to the Colorado Department of Public Health and Environment,” CDPHE director Larry Wolk said. “Budget proposals generally change. We hope Congress will continue to see the value of states being in charge of air and water programs that are protective of the state’s environment and of the people’s health.”

Congress controls the federal budget and Trump team proposals likely will face scrutiny before cuts are made.

Yet, at the EPA’s 500-employee regional headquarters in Denver, longtime civil servants speculated about cuts that some fear could be unprecedented in the agency’s 47-year history. Senior officials, including acting director Deb Thomas, held an all-hands meeting on steps in a central foyer, focusing on the EPA’s core mission, skirting the issue of what cuts might mean for jobs and work in progress from climate change research to cleanups around Colorado and the West.

Their message to EPA employees: “Focus on our core mission,” agency spokesman Andrew Mutter said. “It’s back to basics.”

Meanwhile in the convention center, Gore narrated his slide show, updated after midnight to include latest images of climate change impact around the world — such as a burning building floating in Maryland floodwaters just before crashing into a bridge.

He presented latest data from climate scientists during a past decade where average global temperatures repeatedly have set new records. And photos documents growing human health impacts with temperatures in some regions topping 120 degrees, up to a 165-degree record in Iran – evidence of a trend where authorities increasingly deem areas “uninhabitable.” One slide showed people collapsing as a street melted in India where government officials during a heat wave in 2015 reported 2,330 deaths, and another showed work crews in Pakistan last year digging graves in anticipation of more heat wave deaths.

The activists devoted hours to viewing and discussing wide impacts of climate change, including the recent wildfires and severe flooding in Colorado that scientists and government officials have linked to climate change.

Climate Reality runs offices in 10 nations outside the U.S. and will open an office in Mexico this year, president Ken Berlin said. “We oppose the pipelines like other groups yet have not been involved in the tent camps yet. We will consider that as we go along…. We are taking a look at the best ways to be effective through traditional political action. We want to do everything we can to protect climate change laws.”

The organizers of the training hailed signing of the international Paris Treaty last year as a huge step forward. Cities, businesses and universities around the United States made pledges to shift to cleaner, renewable sources for all the electricity they use. But organizers also acknowledged growing uncertainty about whether the U.S., a main source of the heat-trapping gases, will keep its commitments as part of that treaty.

“It would be a catastrophic setback for the climate movement, and for the world as a whole, if the United States did withdraw,” Gore said.

“There’s a big struggle under way within the Trump White House. … There’s still an excellent chance that, even if he tries to kill the Clean Power Plan, he will decide not to formally withdraw from the Paris Treaty. There’s hardly anything he could do that would create more ill will, diplomatic damage and friction between the U.S. and virtually every other country in the world than pulling out of the Paris Treaty.”

As EPA and other government employees dealing with environment issues worried about loss of momentum, the activists rallying in Denver through Saturday exuded a mostly hopeful determination despite a dizzying deluge of heavy information.

“Most of this can still be stopped,” Gore told them after looking at time-lapse images of arctic glaciers melting and collapsing into a rapidly-warming ocean.

“This is reality. We have to take it out of the partisan framework. That is insane,” he said.

“We have to change. Can we change? If we have to change and we don’t have the ability to change, I don’t want to hear anything more about it because that is just a recipe for anxiety and stress. … Yes, we can change.”