Timeline

—5 Billion Years Ago: Planet Earth forms 

—10,000 years ago: Last Ice Age ends

—1500-1850: Little Ice Age occurs, temperatures in Northern Hemisphere drop by approximately 1 degree Celsius, triggering disease and famine.

—Mid-1700s: Industrial Revolution begins and manual labor-based economy is replaced by industry and coal-burning machinery.

—1824: French mathematician and physicist Joseph Fourier discovers that atmospheric gases could raise the Earth’s surface temperature. His observations would later be known as the greenhouse effect.

—1896: Swedish chemist Svante Arrhenius predicts increased levels of carbon dioxide in the air due to burning of fossil fuels by humans will cause a slow increase in Earth’s temperature.

—1938: British engineer Guy Callendar publishes one of the first studies demonstrating how the burning of fossil fuels is raising the Earth’s surface temperature. His work is largely ignored.

—1957: American scientist Roger Revelle, who later mentors environmental leader Al Gore, co-authors a paper with Han Suess showing that the Earth’s oceans can’t absorb all the carbon dioxide released from burning fossil fuels. Revelle suggests the greenhouse effect could have a major impact on the world’s climate.

—1958: American chemist Charles Keeling begins continuous measuring of carbon dioxide levels in the Earth’s atmosphere, from research station at Mauna Loa, Hawaii. Later, the “Keeling Curve” would show the steady rise of carbon dioxide in the atmosphere.

—1968: Harvard University undergraduate Al Gore meets Roger Revelle in class. Gore later credits Revelle as “one of the first people in the academic community to sound the alarm on global warming.”

—1970s: Strong global warming trend begins, most likely due to rapid increase of human-induced carbon emissions.

—1970: The U.S. Environmental Protection Agency, a federal agency designed to protect human health and the environment, is founded.

—April 22, 1970: First Earth Day celebration is held, organized by U.S. Senator Gaylord Nelson from Wisconsin. Across America, an estimated 20 million people hold rallies and protest the deterioration of the environment.

—1981: Ronald Reagan becomes America’s 40th president and ushers in a politically conservative era that is skeptical of the environmental movement and global warming.

—1985: A sudden Antarctic Ozone hole prompts new concerns about mankind’s impact on the atmosphere.

—1988: James Hansen, NASA’s top climate scientist, warns the public about the long-term dangers of carbon dioxide and other heat-trapping gases on global warming.

—1988: The United Nations Intergovernmental Panel on Climate Change (IPCC) is chartered in Geneva, Switzerland, to provide policymakers with neutral summaries of the latest information related to human-induced climate change. The organization is open to any of the nearly 200 member states belonging to the UN or WMO (World Meteorological Organization).

—Late 1980s: The golden toad, one of the first species known to have become extinct due to climate change, disappears from its natural habitat in Costa Rica.

—1990: Report from United Nations Intergovernmental Panel on Climate Change says planet is warming and future warming is “likely.”

—1992: At the Earth Day Summit in Brazil, industrialized nations agree to take voluntary steps to cut greenhouse gas emissions.

—1997: The Toyota Prius, one of the first mass-produced hybrid electric cars, goes on sale in Japan. The Prius is released worldwide in 2001.

—1997: The Kyoto Protocol to the United Nations Framework Convention on Climate Change, the world’s first treaty among industrialized nations to cut greenhouse gas emissions, is negotiated in Kyoto, Japan.

—1998: The 20th century’s warmest year on record

—2001: New Zealand establishes a residency program for citizens of South Pacific island nations Tuvalu, Tonga, Kiribati and Samoa, all at risk due to rising sea levels caused by climate change.

—2001: Report from the United Nations Intergovernmental Panel on Climate Change says human activity is “likely” responsible for global warming.

—2001: President George W. Bush announces U.S. will not ratify the Kyoto Protocol because it’s detrimental to America’s economic interests.

—2002: Major coral bleaching of Australia’s Great Barrier Reef

—February-March 2002: The Larsen B ice shelf, a massive floating ice shelf that had been attached to the Antarctic Peninsula for thousands of years, collapses and breaks into hundreds of pieces and floats away.

—2003: A heat wave in Europe kills over 30,000 people. Human-induced global warming is later blamed for the event.

—2003: U.S. Senator James Inhofe of Oklahoma claims global warming is a hoax.

—December 2005: More than 100,000 people in over 30 nations hold marches as part of the first worldwide demonstration calling for action against global warming.

—February 16, 2005: The Kyoto Protocol, which calls for industrialized nations to reduce greenhouse gas emissions, goes into force. Notably, the U.S. and Australia do not ratify the treaty.

—February 2005: The U.S. Mayors’ Climate Protection Agreement is launched in response to America’s refusal to sign Kyoto Protocol. Participating cities agree to meet or beat the U.S.’s suggested Kyoto target of reducing emissions by 7% of 1990 levels by 2012.

—August 2005: Hurricane Katrina ravages the U.S. Gulf Coast, causing over $100 million in damages in Louisiana alone.

—January 2006: James Hansen says the Bush Administration is trying to silence him after he called for the prompt reduction of greenhouse gas emissions linked to global warming.

—January 2006: President George W. Bush, in his State of Union address, says America must break its addiction to foreign oil.

—May 2006: An Inconvenient Truth, the climate-change documentary starring Al Gore, opens in theaters. The film goes on to win two Academy Awards and raise international awareness about global warming.

—February 2007: Report from the United Nations Intergovernmental Panel on Climate Change says a global warming trend is “unequivocal” and human activity is “very likely” the cause.

—April 2007: The U.S. Supreme Court rules that the Environmental Protection Agency has the authority to regulate heat-trapping gases in automobile emissions.

—September 2007: Ice melt from the Arctic Ice Cap is so great that the Northwest Passage, a shipping shortcut from Europe to Asia around the top of North America, opens for the first time since satellite records started in 1978.

—October 12, 2007: Al Gore and the United Nations Intergovernmental Panel on Climate Change win the Nobel Peace Prize.