Earth's atmosphere photographed from the International Space Station. Greenhouse gases have accumulated rapidly and are trapping extra heat in the atmosphere. It will take decades for the gases to break down naturally or be reabsorbed on Earth's surface. Expedition 28 Crew/International Space Station/NASA hide caption
Climate change has been a key factor in increasing the risk and extent of wildfires and other catastrophic weather events. Here, an aerial view shows neighborhoods in Monrovia, Calif., shrouded in smoke from the Bobcat Fire in September. David McNew/Getty Images hide caption
The Hunter power plant in Utah generates electricity by burning coal. Coal combustion releases enormous amounts of carbon into the atmosphere. The Utah plant is scheduled to keep operating until 2042. George Frey/AFP via Getty Images hide caption
The smokestacks of a coal-fired power plant near Emmet, Kan., in September 2020. Global greenhouse gas emissions continue to rise. Charlie Riedel/AP hide caption
Methane emitted by ruminant animals such as cattle and sheep accounted for 34% of New Zealand's greenhouse emissions in 2017. A flock of merino sheep on the country's South Island is seen here in April 2017. William West/AFP via Getty Images hide caption
The Trump administration has formally notified the United Nations that it is withdrawing from the Paris climate agreement. The move comes as climate change drives more frequent and severe wildfires, hurricanes — such as Hurricane Florence in 2018 — and other hazards. Alex Wroblewski/Bloomberg/Getty Images hide caption
French President Emmanuel Macron gives a thumbs-up after he delivered an address to a joint meeting of Congress Wednesday at the U.S. Capitol. Alex Wong/Getty Images hide caption
France's President Emmanuel Macron, center, Arnold Schwarzenegger, left, and Prime Minister of Belgium Charles Michel, right, pose for a photo in front of the Eiffel Tower while aboard a boat cruising on the Seine River after the One Planet Summit, Paris, Tuesday, Dec. 12. Thibault Camus/AP hide caption
France's President Emmanuel Macron meets with former U.N. Secretary-Generals Kofi Annan (left) and Ban Ki-moon (right) at the Elysee Palace in Paris on Monday. Michel Euler/AP hide caption
Climate conference attendees in Bonn, Germany, see a representation of Earth's climate trends. Ulrich Baumgarten/Getty Images hide caption
Environmental Protection Agency Administrator Scott Pruitt attends a Cabinet meeting with President Trump in June. Andrew Harnik/AP hide caption
When it comes to convincing climate change deniers, Al Gore says, "Mother Nature is more persuasive than the scientific community." Claire Harbage/NPR hide caption
Connecticut residents at a rally for the environment against President Donald Trump's decision to withdraw the U.S. from the Paris climate accord. Connecticut is one of twelve states and Puerto Rico that formed the U.S. Climate Alliance, all committing to uphold the Paris Accord. Spencer Platt/Getty Images hide caption
Former New York City Mayor Michael Bloomberg says his foundation will fill a funding gap left by the U.S. Christophe Ena/AP hide caption