Here are gathered in chronological sequence the most important events in the history of
climate change science. (For a narrative see the Introduction: Summary History.) The list of
milestones includes major influences external to the science itself. Following that is a list of
additional external influences 1950-1980. On the Website, nearly all items have links to essays.
1800-1870 2
• Level of carbon dioxide gas (CO ) in the atmosphere, as later measured in
ancient ice, is about 290 ppm (parts per million). Mean global temperature (1850-
1890) is roughly 13.7EC.
• First Industrial Revolution. Coal, railroads, and land clearing speed up
greenhouse gas emission, while better agriculture and sanitation speed up
population growth.
1824 • Fourier calculates that the Earth would be far colder if it lacked an atmosphere.
1859 • Tyndall discovers that some gases block infrared 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 2
• Callendar argues that CO greenhouse global warming is underway, reviving
interest in the question.
1939-1945 • World War II. Military 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
• Plass calculates that adding CO to the atmosphere will have a significant effect
on the radiation balance.
1957 • Launch of Soviet Sputnik satellite. Cold War concerns support 1957-58
International Geophysical Year, bringing new funding and coordination to climate
Weart DGW 1/17 Timeline - 2
• Revelle finds that CO produced by humans will not be readily absorbed by the
1958 • Telescope studies show a greenhouse effect raises temperature of the atmosphere
of Venus far above the boiling point of water.
1960 • Mitchell reports downturn of global temperatures since the early 1940s.
• Keeling accurately measures CO in the Earth’s atmosphere and detects an
annual rise. The level is 315 ppm. Mean global temperature (five-year average) is
1962 • Cuban Missile Crisis, peak of the Cold War.
1963 • Calculations suggest that feedback with water vapor could make the climate
acute 2
ly sensitive to changes in CO level.
1965 • Boulder, Colo. meeting on causes of climate change: Lorenz and others point out
the chaotic nature of the climate system and the possibility of sudden shifts.
1966 • Emiliani’s analysis of deep-sea cores and Broecker’s analysis of ancient corals
show that 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 climate.
• Manabe and Wetherald make a convincing calculation that doubling CO 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 • 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 climate 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 span of a thousand years or so.
• Droughts in Africa, Ukraine, India cause world food crisis, spreading fears about
climate change.
1973 • Oil embargo and price rise bring first “energy crisis.”
Weart DGW 1/17 Timeline - 3
1974 • Serious droughts since 1972 increase concern about climate, with cooling from
aerosols suspected to be as likely as warming; scientists are doubtful as journalists
talk of a new ice age.
1975 • Warnings 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 2
temperature rise of several degrees for doubled CO .
1976 • Studies find 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 as the biggest climate
risk in next century.
1978 • Attempts to coordinate climate research in U.S. end with an inadequate National
Climate Program Act, accompanied by temporary growth in funding.
1979 • Second oil “energy crisis.” Strengthened environmental movement encourages
renewable energy sources, inhibits nuclear energy growth.
• U.S. National Academy of Sciences report finds it highly credible that doubling
will bring 1.5-4.5EC global warming.
• World Climate Research Programme launched to coordinate international
1981 • Election of President Reagan brings backlash against environmental movement;
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 span 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 U.S. National Academy of Sciences and Environmental Protection
Agency spark conflict; greenhouse warming becomes prominent in mainstream
• Speculation over catastrophic climate change following a nuclear war, or a
dinosaur-killing asteroid strike, promote realization of the atmosphere’ fragility.
Weart DGW 1/17 Timeline - 4
1985 • Ramanathan and collaborators announce that global warming may come twice as
fast as expected, from rise of methane and other trace greenhouse gases.
• Villach conference declares expert consensus that some global warming seems
inevitable, calls on governments to consider international agreements to restrict
• Antarctic ice cores show that CO and temperature went up and down together
through past ice ages, pointing to powerful feedbacks.
• Broecker speculates that a reorganization of North Atlantic Ocean circulation
can bring swift and radical climate change.
1986 • Meltdown of reactor at Chernobyl (Soviet Union) cripples plans to replace fossil
fuels with nuclear power.
1987 • Montreal Protocol of the Vienna Convention requires 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;
U.K. 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 U.S. industries form Global Climate Coalition to tell
politicians and the public that climate science is too uncertain to justify action.
1990 • First IPCC report says world has been warming and future warming seems
1991 • Mt. Pinatubo explodes; Hansen predicts cooling pattern, verifying (by 1995)
computer models of aerosol effects.
• Global warming skeptics claim that 20th-century temperature changes followed
from solar influences. (The solar-climate correlation would fail in the following
• 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 to affect public opinion.
1997 • Toyota introduces Prius in Japan, first mass-market electric hybrid car; swift
progress in large wind turbines and other energy alternatives.
Weart DGW 1/17 Timeline - 5
• International conference produces Kyoto Protocol, setting targets for
industrialized nations to reduce greenhouse gas emissions if enough nations sign
onto a treaty (rejected by US Senate in advance).
1998 • A “Super El Niño” makes this an exceptionally warm year, equaled in later years
but not clearly exceeded until 2014. Borehole data confirm extraordinary warming
• 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 U.S. 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 the
end of the last ice age, is “very likely,” with highly damaging future impacts and
possible severe surprises. Effective end of debate among all but a few scientists.
• Bonn meeting, with participation of most countries but not U.S., 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 level faster than most had believed.
• Deadly summer heat wave in Europe accelerates divergence between European
and U.S. public opinion.
2004 • First major books, movie and art work featuring global warming appear.
2005 • Kyoto treaty goes into effect, signed by major industrial nations except U.S.
Work to retard emissions accelerates in Japan, Western Europe, U.S. regional
governments and corporations.
• Hurricane Katrina and other major tropical storms spur debate over impact of
global warming on storm intensity.
2006 • In longstanding “hockey stick” controversy, scientists conclude post-1980 global
warming was unprecedented for centuries or more.
• “An Inconvenient Truth” documentary persuades many but sharpens political
• China overtakes the United States as the world’s biggest emitter of CO .
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.
Weart DGW 1/17 Timeline - 6
• Greenland and Antarctic ice sheets and Arctic Ocean sea-ice cover found to be
shrinking faster than expected
2008 • Climate scientists (although not the public) recognize that even if all greenhouse
gas emissions could be halted immediately, global warming will continue for
2009 • Many experts warn that global warming is arriving at a faster and more
dangerous pace than anticipated just a few years earlier.
• Excerpts from stolen e-mails of climate scientists fuel public skepticism
• Copenhagen conference fails to negotiate binding agreements: end of hopes of
avoiding dangerous future climate change.
2012 • Controversial “attribution” studies find recent disastrous heat waves, droughts,
extremes of precipitation, and floods were made worse by global warming.
2013 • An apparent pause or “hiatus” in global warming of the atmosphere since 1998
is discussed and explained; the atmosphere is still warming (the next three recordbreaking
years would confirm that), and the oceans have warmed up steadily.
2015 • Researchers find collapse of West Antarctic ice sheet is irreversible, will bring
meters of sea level rise over future centuries.
• Paris Agreement: nearly all nations pledge to set targets for their own
greenhouse gas cuts and to report their progress.
• Mean global temperature is 14.8EC, the warmest in thousands of years. Level of
in the atmosphere reaches 400 ppm, the highest in millions of years.
Other External Influences 1950-1980
This is a reference list of miscellaneous significant developments that don’t fit into any of
the other essays: scientific-technical matters that arose altogether independently of the
scientific fields covered, and are not included in the list of major “milestones,” but that did
have a significant influence on climate change studies.
Before the 1950s, there were practically no global warming studies as such, and the important
relevant discoveries (the ice ages, absorption of infrared radiation by carbon dioxide, etc.) were
all effectively “external.”
1950s: Research on military applications of radar and infrared radiation promotes advances in
radiative transfer theory and measurements. — Studies conducted largely for military
applications give accurate values of infrared absorption by gases. — Nuclear physicists and
chemists develop Carbon-14 analysis, useful for dating ancient climate changes, for detecting
carbon from fossil fuels in the atmosphere, and for measuring the rate of ocean turnover. —
Development of digital computers affects many fields including the calculation of radiation
transfer in the atmosphere, and makes it possible to model weather processes. — Geological
studies of polar wandering help provoke Ewing-Donn model of ice ages. — Improvements in
infrared instrumentation (mainly for industrial processes) allow very precise measurements of
atmospheric CO2
Weart DGW 1/17 Timeline - 7
1960s: Analysis of automobile and airplane exhaust pollution brings recognition of complex
chemical and light interactions in the atmosphere, especially involving ozone — Research on
urban air pollution, and related industrial and military applications, improve knowledge of
aerosols and atmospheric turbidity. — Studies of fallout from nuclear weapons tests give
improved picture of circulation of aerosols in the stratosphere. — Studies of fallout and
pesticides foster worries that human technology can bring world-wide disaster. — Research on
small-scale phenomena in various fields of geophysics (cloud formation, soil moisture, etc.)
provides information useful for setting crucial parameters in global computer models. — Studies
of rice paddies and other biological and agricultural entities show emission of large quantities of
1970s: Neutrino experiments and new astrophysical theories suggest that the Sun could be a
variable star. — Models of glacier flow, developed by generations of glaciologists, reveal a
possibly catastrophic instability in the Antarctic ice sheet. — Fallout from nuclear weapons tests,
slowly penetrating the oceans, reveals deep circulation patterns. — Studies of ancient reversals of
the Earth’s magnetic field, measured in continental rocks and the ocean floor, provide a timemarker
for climate changes. — Ocean geologists find huge deposits of methane-bearing ices in
the world’s seabeds. — Continued rapid improvement of digital computers and software makes
possible fairly realistic models of complex systems like climate. — Nimbus-III and other
satellites, designed chiefly for weather prediction, provide global data essential for climate
After about 1980, research that could be relevant to global warming was generally undertaken
with an awareness of potential