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EDITOR'S NOTE:
This article was originally published by the American Institute of Physics and {C}Spencer Weart as Timeline of Milestones. The original version contains detailed references and links to additional information on the history of climate change science.

1800-1870

• Level of {C}carbon dioxide gas (CO₂) in the atmosphere, as later measured in ancient ice, is about 290 ppm (parts per million). Mean global temperature (1850-1870) is about 13.6°C.
• First Industrial Revolution. Coal, railroads, and land clearing speed up greenhouse gas emission, while better agriculture and sanitation speed up population growth.

1824

• Joseph Fourier calculates that the Earth would be far colder if it lacked an atmosphere.

1859

• Tyndall discovers that some gases block infrared {C}radiation. He suggests that changes in the concentration of the gases could bring climate change.

1896

• Arrhenius publishes first calculation of global warming from human emissions of CO₂.

1897

• Chamberlin produces a model for global carbon exchange including feedbacks.

1870-1910

• Second Industrial Revolution. Fertilizers and other chemicals, electricity, and public health further accelerate growth.

1914-1918

• World War I; governments learn to mobilize and control industrial societies.

1920-1925

• Opening of Texas and Persian Gulf oil fields inaugurates era of cheap energy.

1930s

• Global warming trend since late 19th century reported.
• Milankovitch proposes orbital changes as the cause of ice ages.

1938

• Callendar argues that CO₂ greenhouse global warming is underway, reviving interest in the question.

1939-1945

• World War II. Grand strategy is largely driven by a struggle to control oil fields.

1945

• US Office of Naval Research begins generous funding of many fields of science, some of which happen to be useful for understanding climate change.

1956

• Ewing and Donn offer a feedback model for quick ice age onset.
• Phillips produces a somewhat realistic computer model of the global atmosphere.
• Plass calculates that adding CO₂ to the atmosphere will have a significant effect on the {C}radiation balance.

1957

• Launch of Soviet Sputnik satellite. Cold War concerns support 1957-58 International Geophysical Year, bringing new funding and coordination to {C}climate studies.
• Revelle finds that CO₂ produced by humans will not be readily absorbed by the {C}oceans.

1958

• Telescope studies show a greenhouse effect raises temperature of the atmosphere of Venus far above the boiling point of water.

1960

• Downturn of global temperatures since the early 1940s is reported.
• Keeling accurately measures CO₂ in the Earth's atmosphere and detects an annual rise. The level is 315 ppm. Mean global temperature (five-year average) is 13.9°C.

1962

• Cuban Missile Crisis, peak of the Cold War.

1963

• Calculations suggest that feedback with water vapor could make the climate acutely sensitive to changes in CO₂ level.

1965

• Boulder, Colo. meeting on causes of climate change: Lorenz and others point out the chaotic nature of climate system and the possibility of sudden shifts.

1966

• Emiliani's analysis of deep-sea cores shows the timing of ice ages was set by small orbital shifts, suggesting that the climate system is sensitive to small changes.

1967

• International Global Atmospheric Research Program established, mainly to gather data for better short-range weather prediction, but including {C}climate.
• Manabe and Wetherald make a convincing calculation that doubling CO₂ would raise world temperatures a couple of degrees.

1968

• Studies suggest a possibility of collapse of Antarctic ice sheets, which would raise sea levels catastrophically.

1969

• Astronauts walk on the Moon, and people perceive the Earth as a fragile whole.
• Budyko and Sellers present models of catastrophic ice-albedo feedbacks.
• Nimbus III satellite begins to provide comprehensive global atmospheric temperature measurements.

1970

• {C}First Earth Day. Environmental movement attains strong influence, spreads concern about global degradation.
• Creation of US National Oceanic and Atmospheric Administration, the world's leading funder of climate research.
• Aerosols from human activity are shown to be increasing swiftly. Bryson claims they counteract global warming and may bring serious cooling.

1971

• SMIC conference of leading scientists reports a danger of rapid and serious global change caused by humans, calls for an organized research effort.
• Mariner 9 spacecraft finds a great dust storm warming the atmosphere of Mars, plus indications of a radically different climate in the past .

1972

• Ice cores and other evidence show big climate shifts in the past between relatively stable modes in the space of a thousand years or so, especially around 11,000 years ago.

1973

• Oil embargo and price rise bring first "energy crisis".

1974

• Serious droughts and other unusual weather since 1972 increase scientific and public concern about climate change, with cooling from aerosols suspected to be as likely as warming; journalists talk of ice age.

1975

• Concern about environmental effects of airplanes leads to investigations of trace gases in the stratosphere and discovery of danger to ozone layer.
• Manabe and collaborators produce complex but plausible computer models which show a temperature rise of several degrees for doubled CO₂.

1976

• Studies show that CFCs (1975) and also methane and ozone (1976) can make a serious contribution to the greenhouse effect.
• Deep-sea cores show a dominating influence from 100,000-year Milankovitch orbital changes, emphasizing the role of feedbacks.
• Deforestation and other ecosystem changes are recognized as major factors in the future of the climate.
• Eddy shows that there were prolonged periods without sunspots in past centuries, corresponding to cold periods.

1977

• Scientific opinion tends to converge on global warming, not cooling, as the chief climate risk in next century.

1978

• Attempts to coordinate climate research in US end with an inadequate National Climate Program Act, accompanied by rapid but temporary growth in funding.

1979

• Second oil "energy crisis." Strengthened environmental movement encourages renewable energy sources, inhibits nuclear energy growth.
• US National Academy of Sciences report finds it highly credible that doubling CO₂ will bring 1.5-4.5°C global warming.
• World Climate Research Programme launched to coordinate international research.

1981

• Election of Reagan brings backlash against environmental movement to power. Political conservatism is linked to skepticism about global warming.
• IBM Personal Computer introduced. Advanced economies are increasingly delinked from energy.
• Hansen and others show that sulfate aerosols can significantly cool the climate, raising confidence in models showing future greenhouse warming.
• Some scientists predict greenhouse warming "signal" should be visible by about the year 2000.

1982

• Greenland ice cores reveal drastic temperature oscillations in the space of a century in the distant past.
• Strong global warming since mid-1970s is reported, with 1981 the warmest year on record.

1983

• Reports from US National Academy of Sciences and Environmental Protection Agency spark conflict, as greenhouse warming becomes prominent in mainstream politics.

1985

• Ramanathan and collaborators announce that methane and other trace gases together could bring as much global warming as CO₂ itself.
• Villach conference declares consensus among experts that some global warming seems inevitable, calls on governments to consider international agreements to restrict emissions.
• Antarctic ice cores show that CO₂ and temperature went up and down together through past ice ages, pointing to powerful biological and geochemical feedbacks.
• Broecker speculates that a reorganization of North Atlantic Ocean circulation can bring swift and radical climate change.

1987

• Montreal Protocol of the Vienna Convention imposes international restrictions on emission of ozone-destroying gases.

1988

• News media coverage of global warming leaps upward following record heat and droughts plus testimony by Hansen.
• Toronto conference calls for strict, specific limits on greenhouse gas emissions; UK Prime Minister Thatcher is first major leader to call for action.
• Ice-core and biology studies confirm living ecosystems give climate feedback by way of methane, which could accelerate global warming.
• Intergovernmental Panel on Climate Change (IPCC) is established.

1989

• Fossil-fuel and other industries form Global Climate Coalition in US to lobby politicians and convince the media and public that climate science is too uncertain to justify action.

1990

• First IPCC report says world has been warming and future warming seems likely. Industry lobbyists and some scientists dispute the tentative conclusions.

1991

• Mt. Pinatubo explodes; Hansen predicts cooling pattern, verifying (by 1995) computer models of aerosol effects.

• Global warming skeptics emphasize studies indicating that a significant part of 20th-century temperature changes were due to solar influences. (The correlation would fail in the following decade.)
• Studies from 55 million years ago show possibility of eruption of methane from the seabed with enormous self-sustained warming.

1992

• Conference in Rio de Janeiro produces UN Framework Convention on Climate Change, but US blocks calls for serious action.
• Study of ancient climates reveals climate sensitivity in same range as predicted independently by computer models.

1993

• Greenland ice cores suggest that great climate changes (at least on a regional scale) can occur in the space of a single decade.

1995

• Second IPCC report detects "signature" of human-caused greenhouse effect warming, declares that serious warming is likely in the coming century.
• Reports of the breaking up of Antarctic ice shelves and other signs of actual current warming in polar regions begin affecting public opinion.

1997

• Toyota introduces Prius in Japan, first mass-market electric hybrid car; swift progress in large wind turbines and other energy alternatives.
• International conference produces Kyoto Protocol, setting targets to reduce greenhouse gas emissions if enough nations sign onto a treaty.

1998

• "Super El Niño" causes weather disasters and warmest year on record (approximately matched by 2005 and 2007). Borehole data confirm extraordinary warming trend.
• Qualms about arbitrariness in computer models diminish as teams model ice-age climate and dispense with special adjustments to reproduce current climate.

1999

• Criticism that satellite measurements show no warming are dismissed by National Academy Panel.

• Ramanathan detects massive "brown cloud" of aerosols from South Asia.

2000

• Global Climate Coalition dissolves as many corporations grapple with threat of warming, but oil lobby convinces US administration to deny problem.
• Variety of studies emphasize variability and importance of biological feedbacks in carbon cycle, liable to accelerate warming.

2001

• Third IPCC report states baldly that global warming, unprecedented since end of last ice age, is "very likely," with possible severe surprises. Effective end of debate among all but a few scientists.
• Bonn meeting, with participation of most countries but not US, develops mechanisms for working towards Kyoto targets.
• National Academy panel sees a "paradigm shift" in scientific recognition of the risk of abrupt climate change (decade-scale).
• Warming observed in ocean basins; match with computer models gives a clear signature of greenhouse effect warming.

2002

• Studies find surprisingly strong "global dimming," due to pollution, has retarded arrival of greenhouse warming, but dimming is now decreasing.

2003

• Numerous observations raise concern that collapse of ice sheets (West Antarctica, Greenland) can raise sea levels faster than most had believed.
• Deadly summer heat wave in Europe accelerates divergence between European and US public opinion.

2004

• In controversy over temperature data covering past millenium, most conclude climate variations were substantial, but not comparable to post-1980 warming.
• First major books, movie and art work featuring global warming appear.

2005

• Kyoto treaty goes into effect, signed by major industrial nations except US. Work to retard emissions accelerates in Japan, Western Europe, US regional governments and corporations.
• Hurricane Katrina and other major tropical storms spur debate over impact of global warming on storm intensity.

2007

• Fourth IPCC report warns that serious effects of warming have become evident; cost of reducing emissions would be far less than the damage they will cause.
• Level of CO₂ in the atmosphere reaches 382 ppm. Mean global temperature (five-year average) is 14.5°C, the warmest in hundreds, perhaps thousands of years.