Level of carbon dioxide gas in the atmosphere is approximately 290 ppm (parts per million).

The advent of the Industrial Revolution, with its increased rate of coal burning, railroad development and land clearing, increases greenhouse gas emission.

In an essay, French mathematician and physicist Jean Baptiste Joseph Fourier suggests that gases in the atmosphere might increase the surface temperature of the earth, using the analogy of a greenhouse.

Beginning of the Second Industrial Revolution, when James Watt's development of the steam engine dramatically increases economic and technological progress.

Irish scientist John Tyndall publishes a paper describing how water vapor, carbon dioxide and hydrocarbons can cause this "greenhouse effect" by absorbing and reflecting heat.

Swedish chemist Svante Arrhenius suggests that carbon dioxide emissions from fossil fuel combustion might increase the greenhouse effect.

British engineer G.S. Callendar links rising temperature and carbon dioxide levels and suggests that greenhouse warming is underway.

Biochemist G.E. Hutchinson suggests a connection between deforestation and an increase in atmospheric carbon dioxide.

At the Scripps Institution of Oceanography, Roger Revelle and Hans Seuss demonstrate that the oceans cannot absorb carbon dioxide as rapidly as human activity is releasing it, warning that people are conducting a "large-scale geophysical experiment" on the planet.

Charles Keeling sets up the first continuous monitoring of atmospheric carbon dioxide levels at the Mauna Loa Observatory on Hawaii, confirming a regular annual rise of levels, which are now up to 315 ppm. Monitoring continues for the next 50 years.

Glaciologist John Mercer suggests the possibility that a West Antarctic ice sheet collapse could raise sea levels catastrophically.

First Earth Day. Creation of U.S. National Oceanic and Atmospheric Administration.

Study of Man's Impact on Climate (SMIC) conference of leading scientists reports a danger of rapid pollution-induced climate change, calling for global data collection and new measurement standards.

United Nations Conference on the Human Environment is held in Stockholm, leading to the creation of the United Nations Environment Program.

Oil embargo and price increase contribute to the first energy crisis.

The World Climate Conference in Geneva is one of the first major international scientific meetings on climate change. That same year, a National Academy of Sciences (NAS) report warns about the climate repercussions of doing nothing as carbon dioxide levels continue to increase.

World Climate Research Program (WCRP) established.

Global warming trend is reported, with 1981 the warmest year on record.

Greenhouse warming becomes a political issue. A U.S. Environmental Protection Agency (EPA) study warns that global warming may affect agricultural conditions and economic systems.

First major international conference on the greenhouse effect at Villach, Austria, warns that some future warming appears inevitable due to past emissions regardless of future actions and recommends consideration of a global treaty to address climatic change. The conference report warns that atmospheric carbon dioxide concentrations recorded at the Mauna Loa Observatory show a steady increase averaging more than 1 ppm/year since Keeling's measurements began.

Dr. James Hansen of NASA Goddard Institute for Space Studies lab testifies at a Congressional hearing that "global warming is at hand," sparking media attention. The UN sets up the Intergovernmental Panel on Climate Change (IPCC) to establish international standards for the science of climate change. Delegates to the Toronto Conference on the Changing Atmosphere call for a 20 percent reduction of global carbon dioxide emissions from current levels by 2005.

U.S. Congresswoman Claudine Schneider (R-RI) authors the Global Warming Prevention Act, the first significant piece of legislation to call for a reduction in greenhouse gas emissions.

Level of carbon dioxide in the atmosphere reaches 350 ppm.

In Canada, the Federal Buildings Initiative is established to help federal departments improve energy efficiency. As of 2005, the result is an estimated $24 million in annual energy savings in more than 5,500 buildings.

United Nations Framework Convention on Climate Change (UNFCC) is adopted. President George Bush signs on behalf of the United States. Initial target is to reduce emissions from industrialized countries to 1990 levels by the year 2000.

In Canada, federal, provincial and territorial governments begin a coordinated approach to addressing climate change with the development of the National Action Strategy on Global Warming. The Energy Efficiency and Alternative Energy program is established with a federal commitment of $175 million in new funding over six years. It includes information programs to help Canadian homeowners and motorists reduce energy consumption.

Greenland ice core studies suggest that large and rapid climate deviations can occur over decades or less.

The Alliance of Small Island States (AOSIS), many of whom are in danger of disappearing as sea levels rise, demand a 20 percent reduction in emissions by 2005.

Hottest year to date. Intergovernmental Panel on Climate Change's Second Assessment Report declares there is evidence of human influence on greenhouse warming, and warns of potential serious warming in the next century.

At the first full meeting of the Climate Change Convention in Berlin, the Berlin Mandate is approved. Industrialized nations agree on the need to negotiate emissions reductions by the end of 1997.

At the second meeting of the Climate Change Convention, the U.S. agrees for the first time to legally binding emissions targets. The U.S. also sides with the IPCC against "skeptical" scientists. It is deemed unlikely that most industrialized countries will meet the Rio agreement to hold emissions at 1990 levels by 2000.

Toyota introduces the first mass-market electric hybrid car, the Prius, in Japan; progress in developing wind turbines and other energy alternatives.

The warmest year on record, averaged from global data.

With most countries participating but not the U.S., the Bonn meeting develops mechanisms for reaching Kyoto Protocol targets. Newly elected U.S. President George W. Bush renounces the Protocol because he questions the science and fears it will damage the U.S. economy.

UN weather agency reports that 2001 is the second hottest year on record. Nine of the 10 warmest years since 1860 have occurred since 1990.

Japan, the European Union and its 15 member states and Canada ratify the Kyoto Protocol.

Nineteen of the 20 hottest years on record have occurred since 1980; 1998 was the hottest year, and 2002 the second hottest ever recorded.

Deadly summer heat wave in Europe kills an estimated 35,000.

The intensity of Hurricane Katrina and other major tropical storms provokes further discussion as to the impact of global warming.

Level of carbon dioxide in the atmosphere reaches 380 ppm.

The warmest year on record in the United States and the sixth warmest worldwide.

The U.S. Fish and Wildlife Service proposes listing the polar bear as an endangered species because its habitat “may literally be melting.”

NASA scientists confirm a net loss of ice to the sea from the Greenland and Antarctic ice sheets, with 20 billion tons of water added to the oceans.

A report from the National Research Council announces that examination of tree rings, glaciers, ocean sediment, and other indicators of past surface temperatures confirms with “high confidence” that “the last few decades of the 20th century were warmer than any comparable period in the last 400 years.”

Global and U.S. annual temperatures are now approximately one degree Fahrenheit warmer than at the start of the twentieth century. The past nine years have all been among the 25 warmest years on record for the contiguous U.S., according to NOAA's National Climatic Data Center. Minnesota, New York, Connecticut, Vermont, and New Hampshire have their warmest December on record.

The ExxonMobil Corporation announces that it has stopped funding groups that have downplayed the risks of greenhouse emissions and is involved in industry talks on potential U.S. greenhouse gas emissions regulations sponsored by the nonprofit Resources for the Future.

Former Vice-President Al Gore’s film about global warming, An Inconvenient Truth, is nominated for two Academy Awards. Gore wins the Nobel Peace Prize for his efforts to build up and disseminate greater knowledge about man-made climate change.

Intergovernmental Panel on Climate Change releases a draft report warning that greenhouse gases are at their highest levels in 650,000 years, and that the subsequent warming is likely to result in more droughts, floods and rising seas.

Australia announces that it will phase out the sale of incandescent lightbulbs over the next three years and substitute more efficient compact fluorescent bulbs, which will help substantially cut greenhouse gas emissions.