Updated at 4:02 p.m. ET

If there was any doubt over President Trump's views on climate change, those doubts evaporated with the unveiling of his proposed federal budget on Thursday.

The budget would end programs to lower domestic greenhouse gas emissions, slash diplomatic efforts to slow climate change and cut scientific missions to study the climate.

"It's terrible from the perspective of having any concern at all about climate change," says Andrew Light, a senior fellow at the World Resources Institute's climate program and a professor at George Mason University.

"They can cut the funding, but climate change is real and we're going to have to deal with it," says Chris McEntee, director of the American Geophysical Union. "Slashing this kind of funding is not going to assist in building the resiliency to climate and the impacts of climate change that this country needs."

Previously, the Trump administration had sent somewhat mixed signals about climate change. Trump himself had described climate change as a hoax, but he also said he had an open-mind toward efforts to control it. Secretary of State Rex Tillerson has acknowledged climate change, while EPA Administrator Scott Pruitt has questioned whether CO2 is causing the globe to warm.

In a press briefing Thursday, Mick Mulvaney, the head of Trump's Office of Management and Budget, was unequivocal about the administration's attitude toward the issue.

"We're not spending money on that anymore," Mulvaney said when asked about climate funding. "We consider that to be a waste of your money to go out and do that."

At the Environmental Protection Agency, the proposed budget "discontinues funding for the Clean Power Plan, international climate change programs, climate change research and partnership programs, and related efforts."

The Clean Power Plan is the Obama administration's plan to reduce greenhouse gas emissions from power plants — an effort that Pruitt has been highly critical of.

At the State Department, the budget proposal "eliminates the Global Climate Change Initiative and fulfills the President's pledge to cease payments to the United Nations' (UN) climate change programs by eliminating U.S. funding related to the Green Climate Fund and its two precursor Climate Investment Funds."

The Green Climate Fund is the U.N. effort to help countries adapt to climate change or develop low-emission energy technologies, and the Global Climate Change Initiative is a kind of umbrella program that paid for dozens of assistance programs to other countries working on things such as clean energy.

"For the last three years, up until last May, I was a senor climate change official at the State Department, and they basically are eviscerating all of the programs that we had created over the course of the last eight years," says Light of the World Resources Institute.

One of his jobs was to coordinate climate and clean energy work with India, a major greenhouse gas emitter. "We created this whole raft of programs on this, and the basis for the funding of all those programs is now eliminated," Light says. "So that means that one of the most vulnerable countries in the world to climate change, and also one of the biggest emerging emitters, is going to get zero help from the United States on this."

The Trump administration does not appear to believe that climate change from greenhouse gases is a real problem, Light says, but it needs to realize that the rest of the world does view global warming as a threat.

"Now we're saying, 'Well, we don't agree with you, you shouldn't actually be worried about that.' That's just something that they're not going to buy," says Light. "That's going to diminish our influence. That's going to make us less safe."

He notes that the Department of Defense has identified climate change as a potentially destabilizing force.

Scientific agencies that study the climate fared little better in the budget proposal. NASA's Earth sciences budget got whacked by about $102 million, down to $1.8 billion. The budget would reduce funding for Earth science research grants.

It would also ax several NASA missions designed to study climate: The Plankton, Aerosol, Cloud, ocean Ecosystem mission, the Orbiting Carbon Observatory-3 mission and the Climate Absolute Radiance and Refractivity Observatory Pathfinder mission.

The budget plan is just a proposal, and Congress ultimately decides federal spending. And advocates for science will be knocking on doors on Capitol Hill to try to stop all of this from happening — plus marching on Washington, D.C., on April 22.

"Congress has a long bipartisan history of protecting research investments," Rush Holt, a former Democratic congressman from New Jersey who is now CEO of the American Association for the Advancement of Science, said in a statement.

"The administration's cuts threaten our nation's ability to advance cures for disease, maintain our technological leadership, ensure a more prosperous energy future, and train the next generation of scientists and innovators to address the complex challenges we face today and in the future," he said.

"However, this is the President's proposal, and it's up to Congress to respond and make decisions on budget and appropriations."

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