History of climate change science

History of climate change science

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The history of the scientific discovery of climate change began in the early 19th century when natural changes in paleoclimate were first suspected and the natural greenhouse effect
Greenhouse effect
The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface, energy is transferred to the surface and the lower atmosphere...

 first identified. In the late 19th century, scientists first argued that human emissions of greenhouse gases could change the climate
Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...

, but the calculations were disputed. In the 1950s and 1960s, scientists increasingly thought that human activity could change the climate on a timescale of decades, but were unsure whether the net impact would be to warm or cool the climate. Then during the 1970s, scientific opinion increasingly favored the warming viewpoint. In the 1980s the consensus position formed that human activity was in the process of warming the climate, leading to the beginning of the modern period of global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...

 science summarized by the Intergovernmental Panel on Climate Change
Intergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change is a scientific intergovernmental body which provides comprehensive assessments of current scientific, technical and socio-economic information worldwide about the risk of climate change caused by human activity, its potential environmental and...


Paleoclimate change and the natural greenhouse effect, early and mid 1800s

Prior to the 18th century, scientists had not suspected that prehistoric climates were different from the modern period. By the late 18th century, geologists found evidence of a succession of geological ages
Geologic time scale
The geologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth...

 with changes in climate. There were various competing theories about these changes, and James Hutton
James Hutton
James Hutton was a Scottish physician, geologist, naturalist, chemical manufacturer and experimental agriculturalist. He is considered the father of modern geology...

, whose ideas of cyclic change over huge periods of time were later dubbed uniformitarianism
In the philosophy of naturalism, the uniformitarianism assumption is that the same natural laws and processes that operate in the universe now, have always operated in the universe in the past and apply everywhere in the universe. It has included the gradualistic concept that "the present is the...

, was among those who found signs of past glacial activity in places too warm for glaciers in modern times.

Although he wasn't a scientist, in 1815 Jean-Pierre Perraudin described for the first time how glaciers might be responsible for the giant boulders seen in alpine valleys. As he hiked in the Val de Bagnes, he noticed giant granite rocks that were scattered around the narrow valley. He knew that it would take an exceptional force to move such large rocks. He also noticed how glaciers left stripes on the land, and concluded that it was the ice that had carried the boulders down into the valleys.

His idea was initially met with disbelief. Jean de Charpentier
Jean de Charpentier
Jean de Charpentier or Johann von Charpentier was a German-Swiss geologist who studied Swiss glaciers...

 wrote, "I found his hypothesis so extraordinary and even so extravagant that I considered it as not worth examining or even considering." Despite Charpentier rejecting his theory, Perraudin eventually convinced Ignaz Venetz
Ignaz Venetz
Ignaz Venetz was a Swiss engineer, naturalist, and glaciologist; as one of the first scientists to recognize glaciers as a major force in shaping the earth, he played a leading role in the foundation of glaciology....

 that it might be worth studying. Venetz convinced Charpentier, who in turn convinced the influential scientist Louis Agassiz
Louis Agassiz
Jean Louis Rodolphe Agassiz was a Swiss paleontologist, glaciologist, geologist and a prominent innovator in the study of the Earth's natural history. He grew up in Switzerland and became a professor of natural history at University of Neuchâtel...

 that the glacial theory had merit.

Agassiz developed a theory of what he termed "Ice Age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

" — when glaciers covered Europe and much of North America. In 1837 Agassiz was the first to scientifically propose that the Earth had been subject to a past ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

. William Buckland
William Buckland
The Very Rev. Dr William Buckland DD FRS was an English geologist, palaeontologist and Dean of Westminster, who wrote the first full account of a fossil dinosaur, which he named Megalosaurus...

 had led attempts in Britain to adapt the geological theory of catastrophism
Catastrophism is the theory that the Earth has been affected in the past by sudden, short-lived, violent events, possibly worldwide in scope. The dominant paradigm of modern geology is uniformitarianism , in which slow incremental changes, such as erosion, create the Earth's appearance...

 to account for erratic boulders and other "diluvium" as relics of the Biblical flood. This was strongly opposed by Charles Lyell
Charles Lyell
Sir Charles Lyell, 1st Baronet, Kt FRS was a British lawyer and the foremost geologist of his day. He is best known as the author of Principles of Geology, which popularised James Hutton's concepts of uniformitarianism – the idea that the earth was shaped by slow-moving forces still in operation...

's version of Hutton's uniformitarianism, and was gradually abandoned by Buckland and other catastrophist geologists. A field trip to the Alps with Agassiz in October 1838 convinced Buckland that features in Britain had been caused by glaciation, and both he and Lyell strongly supported the ice age theory which became widely accepted by the 1870s.

In the same general period that scientists first suspected climate change and ice ages, Joseph Fourier
Joseph Fourier
Jean Baptiste Joseph Fourier was a French mathematician and physicist best known for initiating the investigation of Fourier series and their applications to problems of heat transfer and vibrations. The Fourier transform and Fourier's Law are also named in his honour...

, in 1824, found that Earth's atmosphere kept the planet warmer than would be the case in a vacuum, and he made the first calculations of the warming effect. Fourier recognized that the atmosphere transmitted visible light waves efficiently to the earth's surface. The earth then absorbed visible light and emitted infrared radiation in response, but the atmosphere did not transmit infrared efficiently, which therefore increased surface temperatures. He also suspected that human activities could influence climate, although he focused primarily on land use changes. In a 1827 paper Fourier stated, "The establishment and progress of human societies, the action of natural forces, can notably change, and in vast regions, the state of the surface, the distribution of water and the great movements of the air. Such effects are able to make to vary, in the course of many centuries, the average degree of heat; because the analytic expressions contain coefficients relating to the state of the surface and which greatly influence the temperature."

John Tyndall
John Tyndall
John Tyndall FRS was a prominent Irish 19th century physicist. His initial scientific fame arose in the 1850s from his study of diamagnetism. Later he studied thermal radiation, and produced a number of discoveries about processes in the atmosphere...

 took Fourier's work one step further when he investigated the absorption of heat in different gases.

First calculations of human-induced climate change, late 1800s

By the late 1890s, American scientist Samuel Pierpoint Langley had attempted to determine the surface temperature of the moon by measuring infrared radiation leaving the moon and reaching the earth. The angle of the moon in the sky when a scientist took a measurement determined how much and water vapor the moon's radiation had to pass through to reach the earth's surface, resulting in weaker measurements when the moon was low in the sky. This result was unsurprising given that scientists had known about the greenhouse effect for decades.

Meanwhile, Swedish scientist Arvid Högbom had been attempting to quantify natural sources of emissions of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

  for purposes of understanding the global carbon cycle. Högbom decided to compare the natural sources with estimated carbon production from industrial sources in the 1890s.

Another Swedish scientist, Svante Arrhenius
Svante Arrhenius
Svante August Arrhenius was a Swedish scientist, originally a physicist, but often referred to as a chemist, and one of the founders of the science of physical chemistry...

, integrated Högbom and Langley's work. He realized that Högbom's calculation of human influence on carbon would eventually lead to a doubling of atmospheric carbon dioxide, and used Langley's observations of increased infrared absorption
Absorption spectroscopy
Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating field. The intensity of the absorption varies as a...

 where moon rays pass through atmosphere at a low angle, encountering more , to estimate an atmospheric warming effect from a future doubling of . He also realized the effect would also reduce snow and ice cover on earth, making the planet darker and warmer. Adding in this effect gave a total calculated warming of 5-6 degrees Celsius. However, because of the relatively low rate of production in 1896, Arrhenius thought the warming would take thousands of years and might even be beneficial to humanity.

Controversy and disinterest, early 1900s to 1950s

Arrhenius' calculations were disputed and subsumed into a larger debate over whether atmospheric changes had caused the ice ages. Experimental attempts to measure infrared absorption in the laboratory showed little differences resulted from increasing levels, and also found significant overlap between absorption by and absorption by water vapor, all of which suggested that increasing carbon dioxide emissions would have little climatic effect. These early experiments were later found to be insufficiently accurate, given the instrumentation of the time. Many scientists also thought that oceans would quickly absorb any excess carbon dioxide.

While a few early 20th-Century scientists supported Arrhenius' work, including E. O. Hulburt and Guy Stewart Callendar, most scientific opinion disputed or ignored it through the early 1950s.

Concern and increasing urgency, 1950s and 1960s

Better spectrography
A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...

 in the 1950s showed that and water vapor absorption lines did not overlap completely. Climatologists also realized that little water vapor was present in the upper atmosphere. Both developments showed that the greenhouse effect would not be overwhelmed by water vapor.

Scientists began using computers to develop more sophisticated versions of Arrhenius' equations, and carbon-14
Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological...

 isotope analysis showed that released from fossil fuels were not immediately absorbed by the ocean. Better understanding of ocean chemistry led to a realization that the ocean surface layer had limited ability to absorb carbon dioxide. By the late 1950s, more scientists were arguing that carbon dioxide emissions could be a problem, with some projecting in 1959 that would rise 25% by the year 2000, with potentially "radical" effects on climate.

By the 1960s, aerosol
Technically, an aerosol is a suspension of fine solid particles or liquid droplets in a gas. Examples are clouds, and air pollution such as smog and smoke. In general conversation, aerosol usually refers to an aerosol spray can or the output of such a can...

 pollution ("smog") had become a serious local problem in many cities, and some scientists began to consider whether the cooling effect of particulate
Particulates – also known as particulate matter , suspended particulate matter , fine particles, and soot – are tiny subdivisions of solid matter suspended in a gas or liquid. In contrast, aerosol refers to particles and/or liquid droplets and the gas together. Sources of particulate matter can be...

 pollution could affect global temperatures. Scientists were unsure whether the cooling effect of particulate pollution or warming effect of greenhouse gas emissions would predominate, but regardless, began to suspect the net effect could be disruptive to climate in the matter of decades. In his 1968 book The Population Bomb
The Population Bomb
The Population Bomb was a best-selling book written by Paul R. Ehrlich and his wife, Anne Ehrlich , in 1968. It warned of the mass starvation of humans in the 1970s and 1980s due to overpopulation, as well as other major societal upheavals, and advocated immediate action to limit population growth...

, Paul R. Ehrlich
Paul R. Ehrlich
Paul Ralph Ehrlich is an American biologist and educator who is the Bing Professor of Population Studies in the department of Biological Sciences at Stanford University and president of Stanford's Center for Conservation Biology. By training he is an entomologist specializing in Lepidoptera , but...

 wrote "the greenhouse effect is being enhanced now by the greatly increased level of carbon dioxide... [this] is being countered by low-level clouds generated by contrails, dust, and other contaminants... At the moment we cannot predict what the overall climatic results will be of our using the atmosphere as a garbage dump."

Scientists increasingly predicting warming, 1970s

Scientists in the 1970s started to shift from the uncertain leanings in the 1960s to increasingly a prediction of future warming. A survey of the scientific literature from 1965 to 1979 found 7 articles predicting cooling and 44 predicting warming, with the warming articles also being cited much more often in subsequent scientific literature.

Several scientific panels from this time period concluded that more research was needed to determine whether warming or cooling was likely, indicating that the trend in the scientific literature had not yet become a consensus. On the other hand, the 1979 World Climate Conference of the World Meteorological Organization
World Meteorological Organization
The World Meteorological Organization is an intergovernmental organization with a membership of 189 Member States and Territories. It originated from the International Meteorological Organization , which was founded in 1873...

 concluded "it appears plausible that an increased amount of carbon dioxide in the atmosphere can contribute to a gradual warming of the lower atmosphere, especially at higher latitudes....It is possible that some effects on a regional and global scale may be detectable before the end of this century and become significant before the middle of the next century."

In July 1979 the United States National Research Council
United States National Research Council
The National Research Council of the USA is the working arm of the United States National Academies, carrying out most of the studies done in their names.The National Academies include:* National Academy of Sciences...

 published a report,

concluding (in part):
The mainstream news media at the time did not reflect scientific opinion. In 1975, Newsweek
Newsweek is an American weekly news magazine published in New York City. It is distributed throughout the United States and internationally. It is the second-largest news weekly magazine in the U.S., having trailed Time in circulation and advertising revenue for most of its existence...

magazine published a story that warned of "ominous signs that the Earth's weather patterns have begun to change," and reported "a drop of half a degree [Fahrenheit] in average ground temperatures in the Northern Hemisphere between 1945 and 1968." The article continued by stating that evidence of global cooling was so strong that meteorologists were having "a hard time keeping up with it." On October 23, 2006, Newsweek issued an update stating that it had been "spectacularly wrong about the near-term future".

Climate change scientific consensus begins development, 1980-1988

By the early 1980s, the slight cooling trend from 1945-1975 had stopped. Aerosol pollution had decreased in many areas due to environmental legislation and changes in fuel use, and it became clear that the cooling effect from aerosols was not going to increase substantially while carbon dioxide levels were progressively increasing.

In 1985 a joint UNEP/WMO/ICSU Conference on the "Assessment of the Role of Carbon Dioxide and Other Greenhouse Gases in Climate Variations and Associated Impacts" assessed the role of carbon dioxide and aerosols in the atmosphere, and concluded that greenhouse gases "are expected" to cause significant warming in the next century and that some warming is inevitable. In June 1988, James E. Hansen made one of the first assessments that human-caused warming had already measurably affected global climate.

Modern period: 1988 to present

Both the UNEP and WMO had followed up on the 1985 Conference with additional meetings. In 1988 the WMO established the Intergovernmental Panel on Climate Change
Intergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change is a scientific intergovernmental body which provides comprehensive assessments of current scientific, technical and socio-economic information worldwide about the risk of climate change caused by human activity, its potential environmental and...

 with the support of the UNEP. The IPCC continues its work through the present day, and issues a series of Assessment Reports and supplemental reports that describe the state of scientific understanding at the time each report is prepared. Scientific developments during this period are discussed in the articles for each Assessment Report.

Discovery of other climate changing factors

Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

In 1859, John Tyndall
John Tyndall
John Tyndall FRS was a prominent Irish 19th century physicist. His initial scientific fame arose in the 1850s from his study of diamagnetism. Later he studied thermal radiation, and produced a number of discoveries about processes in the atmosphere...

 determined that coal gas
Coal gas
Coal gas is a flammable gaseous fuel made by the destructive distillation of coal containing a variety of calorific gases including hydrogen, carbon monoxide, methane and volatile hydrocarbons together with small quantities of non-calorific gases such as carbon dioxide and nitrogen...

, a mix of methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

 and other gases, strongly absorbed infrared radiation. Methane was subsequently detected in the atmosphere in 1948, and in the 1980s scientists realized that human emissions were having a substantial impact.

Milankovitch cycles
Milankovitch cycles
Milankovitch theory describes the collective effects of changes in the Earth's movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković, who worked on it during First World War internment...

Beginning in 1864, Scottish geologist James Croll
James Croll
James Croll was a 19th century Scottish scientist who developed a theory of climate change based on changes in the Earth's orbit.-Life:...

 proposed that changes in earth's orbit could trigger cycles of ice ages by changing the total amount of winter sunlight in the high latitudes. His ideas were widely discussed but not accepted. Serbian geophysicist Milutin Milanković
Milutin Milankovic
Milutin Milanković was a Serbian geophysicist and civil engineer, best known for his theory of ice ages, suggesting a relationship between Earth's long-term climate changes and periodic changes in its orbit, now known as Milankovitch cycles. Milanković gave two fundamental contributions to global...

 developed these concepts in more detail in 1941 with the publication of Kanon der Erdbestrahlung und seine Anwendung auf das Eiszeitenproblem (Canon of Insolation of the Earth and Its Application to the Problem of the Ice Ages). Milanković's ideas became the consensus position in the 1970s, when ocean sediment dating matched the prediction of 100,000 year ice-age cycles.

A chlorofluorocarbon is an organic compound that contains carbon, chlorine, and fluorine, produced as a volatile derivative of methane and ethane. A common subclass are the hydrochlorofluorocarbons , which contain hydrogen, as well. They are also commonly known by the DuPont trade name Freon...

In 1973, British scientist James Lovelock
James Lovelock
James Lovelock, CH, CBE, FRS is an independent scientist, environmentalist and futurologist who lives in Devon, England. He is best known for proposing the Gaia hypothesis, which postulates that the biosphere is a self-regulating entity with the capacity to keep our planet healthy by controlling...

 speculated that chlorofluorocarbons (CFCs) could have a global warming effect. In 1975, V. Ramanathan
Veerabhadran Ramanathan
Veerabhadran Ramanathan is Victor Alderson Professor of Applied Ocean Sciences and director of the Center for Atmospheric Sciences at the Scripps Institution of Oceanography, University of California, San Diego. He has contributed to many areas of the atmospheric sciences including developments to...

 found that a CFC molecule could be 10,000 times more effective in absorbing infrared radiation than a carbon dioxide molecule, making CFCs potentially important despite their very low concentrations in the atmosphere. While most early work on CFCs focused on their role in ozone depletion
Ozone depletion
Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of about 4% per decade in the total volume of ozone in Earth's stratosphere , and a much larger springtime decrease in stratospheric ozone over Earth's polar regions. The latter phenomenon...

, by 1985 scientists had concluded that CFCs together with methane and other trace gases could have nearly as important a climate effect as increases in CO2.

Published works discussing the history of climate change science

Historian Spencer Weart wrote The Discovery of Global Warming
The Discovery of Global Warming
The Discovery of Global Warming is a book by the physicist and historian Spencer R. Weart published by Harvard University Press in 2003; revised and updated edition, 2008. It traces the history of scientific discoveries that led to the current scientific opinion on climate change.- External links :*...

that summarized the history of climate change science, and provided an extensive supplementary website at the American Institute of Physics
American Institute of Physics
The American Institute of Physics promotes science, the profession of physics, publishes physics journals, and produces publications for scientific and engineering societies. The AIP is made up of various member societies...


The IPCC published a review of the later period of climate science in December 2004, "16 Years of Scientific Assessment in Support of the Climate Convention".

The American Meteorological Society
American Meteorological Society
The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, the American Meteorological Society has a membership...

 published "The Myth of the 1970s Global Cooling Consensus" that focuses on the middle period in climate science.

The Long Thaw by David Archer
David Archer (scientist)
David Archer is a computational ocean chemist, and has been a Professor at the Department of The Geophysical Sciences at the University of Chicago since 1993. He has published research on the carbon cycle of the ocean and the sea floor...

 is primarily about current understanding of climate science but also includes information about the science's history.

Keeping Your Cool - Canada in a Warming World by Andrew Weaver
Andrew J. Weaver
Andrew J. Weaver is a climate modeller in the School of Earth and Ocean Sciences at the University of Victoria, British Columbia, and a lead author of a chapter on Global Climate Projections in the Intergovernmental Panel on Climate Change's report Climate Change 2007: The Physical Science Basis. ....

 addresses many questions about climate science including extensive discussion of its history.

See also

  • Description of the Medieval Warm Period and Little Ice Age in IPCC reports
  • Historical climatology
    Historical climatology
    Historical climatology is the study of historical changes in climate and their effect on human history and development. This differs from paleoclimatology which encompasses climate change over the entire history of the earth. The study seeks to define periods in human history where temperature or...

  • History of geology
    History of geology
    The history of geology is concerned with the development of the natural science of geology. Geology is the scientific study of the origin, history, and structure of the Earth. Throughout the ages geology provides essential theories and data that shape how society conceptualizes the...

  • History of geophysics
    History of geophysics
    The historical development of geophysics has been motivated by two factors. One of these is the research curiosity of humankind related to Planet Earth and its several components, its events and its problems...

External links