In an outcome that would have been unthinkable just a year ago, the most notorious climate deniers in the country are about to take over the U.S. government.

Never before have people who reject the mainstream scientific evidence that the world is warming due to human activities occupied so many positions of power, from the White House to federal agencies and both houses of Congress. Depending on the policies they enact, these individuals could have dire consequences for the planet.

It was just one year ago this week that world leaders came together in Paris to adopt the most far-reaching climate change agreement ever negotiated. At the time, the Paris agreement seemed to be a repudiation of climate denial, with climate action ascendant from Beijing to Washington and Delhi to Nairobi.

Then Donald Trump was elected president.

SEE ALSO: Climate scientists vow to stand up to Trump

Trump's narrow electoral victory suddenly catapulted climate denialists to the center of policy making in Washington. People whose views rendered them fringe backbenchers will now be cabinet secretaries, capable of abruptly and profoundly altering course on U.S. climate policy.

For each of the major environmental agencies, including the Department of Energy, Environmental Protection Agency and Department of the Interior, President-elect Trump has nominated climate deniers and avowed proponents of fossil fuels.

Officials celebrate the adoption of the Paris Climate Agreement in Le Bourget, France on Dec. 12, 2015. Image: WITT/ SIPA PRESS/SIPA

For the job of secretary of state, who will be in charge of managing climate negotiations on behalf of the country, Trump has put forward the leader of one of the companies most responsible for causing global warming in the first place: Rex Tillerson of ExxonMobil Corp, which is the largest publicly traded oil company in the world.

Other senior advisers who will occupy high-level roles in the White House also deny that human activities are the primary cause of global warming.

In the scientific community, there's virtually no debate about the following based on observational evidence alone:

Greenhouse gases are at the highest level they've been in all of human history.

Global temperatures continue to increase, with 2016 on track to be the hottest year on record.

The current decade is likely to be the hottest on record, beating the benchmark set in the 2000s, which in turn beat the 1990s.

Sea levels are rising as the world's ice sheets melt, causing more frequent and damaging coastal flooding in low-lying cities.

Arctic sea ice is melting, permafrost is melting and spring snow cover is declining as temperatures increase at twice the rate of the rest of the globe.

Might not feel like it today, but 2016 will be the warmest year in the surface temperature records, 1.2ºC/2ºF above the late 19th C pic.twitter.com/npGM1741Vf — Gavin Schmidt (@ClimateOfGavin) December 15, 2016

Here's a guide to the people Trump is putting forward for high-level positions, and what they think about the mainstream scientific consensus on human-caused global warming.

Scott Pruitt, EPA Administrator

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Scott Pruitt, 48, is the Republican attorney general of Oklahoma and a steadfast ally of the state's oil and gas industry. He describes himself as "a leading advocate against the EPA's activist agenda" and is suing to dismantle the agency's Clean Power Plan to reduce carbon emissions from power plants.

Pruitt also created a "federalism unit" in the Oklahoma AG office dedicated to fighting the Obama administration's policies on immigration, health care, finance reform and environmental protection.

As EPA administrator, Pruitt would oversee policies and programs designed to reduce air and water pollution, curb greenhouse gas emissions, clean up oil spills and protect communities from toxic chemicals, among many other responsibilities. Pruitt has vowed to scrap environmental regulations to make it easier for companies to produce and burn fossil fuels.

In a Trumpian twist, if he is confirmed, Pruitt would inherit the task of working with the Justice Department to respond to the lawsuit that he himself helped bring.

Would he rule in his own favor?

Rick Perry, Secretary of Energy

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Rick Perry, 66, served three terms as the Republican governor of Texas, from 2000 to 2015. Before that, he was the lieutenant governor to then-Governor George W. Bush and the Texas agricultural commissioner.

He currently sits on the board of Energy Transfer Partners and Sunoco Logistics Partners, the two companies behind the controversial Dakota Access Pipeline. Perry has called himself an "all-of-the-above" energy advocate and oversaw a boom in both oil drilling and wind power as Texas governor.

The Energy Department's last two leaders were both highly regarded scientists, befitting of an agency that is a top funder of physical science research in the United States. Perry, who was briefly a contestant on Dancing With The Stars, marks a striking departure from this mold.

The Energy Department has a complex mandate that includes managing the country's nuclear weapons stockpile and running 17 national labs, as well as setting regulations for energy-efficient appliances and funding research and development for clean energy technologies.

Perry, who once vowed to eliminate the Energy Department entirely, may move to slash spending on advanced research into risky, early-stage energy technologies. In particular, he could target a little-known clean energy agency called ARPA-E, an agency that was an early backer of Tesla Motors.

Rex Tillerson, Secretary of State

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Rex Tillerson, 64, has worked for Exxon for his entire professional career, having started working there as a petroleum engineer in 1975. The Texas native and former Eagle Scout rose to become CEO in 2006.

As CEO, Tillerson has moved to have Exxon acknowledge the central role that human-caused greenhouse gas emissions play in global warming.

The company now supports putting a price on carbon emissions and has invested in biofuels and carbon capture and storage — two advanced technologies that would still allow oil and gas to be burned in the future.

Tillerson's close personal ties to Russia’s Vladimir Putin are expected to come under scrutiny during Tillerson's nomination hearing with the Senate.

Image: Bob Al-Greene/Mashable/Getty

Exxon is currently under investigation for misleading its investors and the U.S. public about the threat of global warming since the 1970s. Investigative reports by multiple media outlets have shown that the company knew its oil and gas products were causing climate change, yet funded disinformation campaigns to convince the public the science of climate change was unsettled.

Tillerson will manage the messaging of U.S. climate policy to the rest of the world. Secretary of State John Kerry was central to negotiating the Paris Climate Agreement and brokering collaboration with Chinese leadership. It's unclear if Tillerson has the same conviction that climate change should be a high priority for American foreign policy, given Exxon's track record.

Ryan Zinke, Secretary of the Interior

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Ryan Zinke, 55, is a freshman Republican representative for Montana and a former state senator. He was also in the U.S. Navy and served as a member of the elite SEAL special operations unit, serving in Iraq, Bosnia, Kosovo and the Pacific. During his 2014 House campaign, he called Hillary Clinton the "Antichrist" and America's "real enemy."

Image: Bob Al-Greene/Mashable/Getty

The Interior Department manages and protects U.S. natural and cultural resources, such as national parks, landmarks and public lands. The agency plays a key role in monitoring climate impacts and updating land management strategies to account for those changes, such as addressing wildfire risk in drought-stricken areas and preparing for sea level rise.

Zinke supports keeping U.S. public lands under federal control, but he has also called for opening those areas up to more private oil and gas drilling, coal mining and logging. He has also voted against regulations to protect waters in national parks from toxic pollution — another role of the Interior department.

Reince Priebus, Chief of Staff

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Reince Priebus, 44, is a lawyer, Trump campaign adviser and chairman of the Republican National Committee (RNC). He was previously the RNC's general counsel and chaired the Republican Party of Wisconsin from 2007 to 2011. During that time, he helped bring two state politicians to national prominence: House Speaker Paul Ryan and Wisconsin Gov. Scott Walker.

The position of White House chief of staff is widely considered the second most powerful job in Washington. By serving as the gatekeeper to the president and manager of issues and ideas that make it to the president's desk, Priebus will be able to exert significant influence over the White House's policy agenda. Priebus may be even more powerful than previous chiefs of staff due to Trump's lack of political experience.

Priebus himself has downplayed the significance of human-caused climate change and supported politicians like Walker, who deny the scientific evidence tying greenhouse gas emissions to increasing global temperatures.

Ben Carson, Secretary of Housing and Urban Development

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Ben Carson, 65, is a retired neurosurgeon and a former 2016 Republican presidential candidate. He was director of pediatric neurosurgery at Johns Hopkins Hospital in Baltimore, Maryland, from 1984 to 2013. Despite his scientific background, he disputes well-tested scientific concepts such as evolution and climate change.

Carson has said his years of treating inner-city patients, plus his childhood in Detroit, make him qualified to run the Department of Housing and Urban Development. The agency oversees affordable-housing programs and enforces fair-housing legislation.

In the wake of 2012's Hurricane Sandy, which damaged hundreds of public housing units in East Coast flood zones, HUD has also become a lab for climate change resiliency. In January, the agency awarded $1 billion in grants to help communities prepare for natural disasters such as floods, heat waves and wildfires, which will grow more frequent and severe because of climate change.

Jeff Sessions, Attorney General

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Jeff Sessions, 69, is a veteran Republican senator and a former attorney general and U.S. attorney in Alabama. Sessions has been dogged by allegations of racism throughout his career. In 1986, when the Reagan administration tapped Sessions to serve as a federal judge, the Republican-controlled Senate rejected the nomination based on testimony of Sessions' racist remarks.

Sessions has opposed many major Obama-era policies, including legalizing same-sex marriage, immigration reform, health care reform and regulating greenhouse gas emissions.

As attorney general, Sessions would be responsible for directing the legal defense of federal regulations, including any lawsuits against the EPA's Clean Power Plan. Sessions has been a harsh critic of the plan, arguing it would not solve global warming.

Steve Bannon, Chief Strategist

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Steve Bannon, 63, was Trump's third and final top campaign official. He was previously the executive chair of the far-right website Breitbart News. Breitbart has published stories espousing white nationalist, racist, anti-Semitic, anti-Muslim and other offensive views. Bannon has called Breitbart "the platform for the alt-right."

Breitbart plays host to numerous writers that regularly skewer and distort climate science findings and policy initiatives like the Paris Agreement. Recently, for example, Breitbart ran a story claiming the world is rapidly cooling, even though 2016 is about to set a record for the globe's hottest year.

Before joining Breitbart, Bannon was a U.S. naval officer and an investment banker at Goldman Sachs. In the 1990s, he helped run Biosphere 2, a research project in Arizona designed to replicate life on Earth. Bannon is also a Hollywood media executive and the host of a satellite radio show.

Mike Pompeo, CIA Director

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Mike Pompeo, 52, is a Republican congressman from Kansas and a member of the Tea Party movement. A member of the House Select Committee on Benghazi, Pompeo gained notoriety for his grilling of former secretary of state Hillary Clinton over her supposed role in the deadly attack on the U.S. consulate in Benghazi.

A West Point graduate, Pompeo has close ties to Charles and David Koch, the billionaire conservative brothers who have funded many recent efforts to spread misinformation on climate change.

His questioning of Obama administration environmental officials has revealed that he questions whether global temperatures are increasing, and if so, if human activities are the main cause.

As CIA director, Pompeo will oversee a sprawling intelligence agency that, in addition to tracking and eliminating terrorists affiliated with ISIS and other groups, analyzes broad global threats to stability and U.S. national security.

Under President Obama, CIA analysts have been involved in assessing how climate change may service as a risk multiplier in the future, helping to trigger crises. This may already have happened, given scientific evidence tying the outbreak of the Syrian Civil War to a severe, climate change-related drought.

For example, a report earlier this year from the National Intelligence Council found that "climate-change-related disruptions are well underway."

Under the leadership of a climate denier like Pompeo, however, the CIA might be less willing to continue pursuing such research, leaving it to academics or other agencies to pick up the slack.

This could harm U.S. national security if it keeps policy makers in the dark about how profoundly climate change may soon be altering the national security landscape.