History of climate change science

For example, Theophrastus, a pupil of Ancient Greek philosopher Aristotle in the 4th century BC, told how the draining of marshes had made a particular locality more susceptible to freezing, and speculated that lands became warmer when the clearing of forests exposed them to sunlight.

[6][7] Renaissance European and later scholars saw that deforestation, irrigation, and grazing had altered the lands around the Mediterranean since ancient times; they thought it plausible that these human interventions had affected the local weather.

European academics, suggesting that the temperate zones inhabited by the "Caucasian race" were naturally superior for the spread of civilization, proffered that the Orientals of the Ancient Near East had heedlessly converted their once lush lands into impoverished deserts.

James Hutton, whose ideas of cyclic change over huge periods were later dubbed uniformitarianism, was among those who found signs of past glacial activity in places too warm for glaciers in modern times.

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.

[22][23] The physicist Claude Pouillet proposed in 1838 that water vapor and carbon dioxide might trap infrared and warm the atmosphere, but there was still no experimental evidence of these gases absorbing heat from thermal radiation.

Few noticed the paper and it was only rediscovered in the 21st century,[26][27][28][29] John Tyndall took Fourier's work one step further in 1859 when he built an apparatus to investigate the absorption of infrared radiation in different gases.

Noting that the rings were thinner in dry years, he reported climate effects from solar variations, particularly in connection with the 17th-century dearth of sunspots (the Maunder Minimum) noticed previously by William Herschel and others.

In 1967, taking advantage of the ability of digital computers to integrate absorption curves numerically, Syukuro Manabe and Richard Wetherald made the first detailed calculation of the greenhouse effect incorporating convection (the "Manabe-Wetherald one-dimensional radiative-convective model").

[54][55] They found that, in the absence of unknown feedbacks such as changes in clouds, a doubling of carbon dioxide from the current level would result in approximately 2 °C increase in global temperature.

In his 1968 book The Population Bomb, Paul R. Ehrlich 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.

[58][59] In 1965, the landmark report "Restoring the Quality of Our Environment" by U.S. President Lyndon B. Johnson's Science Advisory Committee warned of the harmful effects of fossil fuel emissions: The part that remains in the atmosphere may have a significant effect on climate; carbon dioxide is nearly transparent to visible light, but it is a strong absorber and back radiator of infrared radiation, particularly in the wave lengths from 12 to 18 microns; consequently, an increase of atmospheric carbon dioxide could act, much like the glass in a greenhouse, to raise the temperature of the lower air.

[59] Nobel Prize winner Glenn T. Seaborg, Chairperson of the United States Atomic Energy Commission warned of the climate crisis in 1966: "At the rate we are currently adding carbon dioxide to our atmosphere (six billion tons a year), within the next few decades the heat balance of the atmosphere could be altered enough to produce marked changes in the climate--changes which we might have no means of controlling even if by that time we have made great advances in our programs of weather modification.

White House Urban Affairs Director,discussing the greenhouse effect andurging building of a monitoring system A 1968 study by the Stanford Research Institute for the American Petroleum Institute noted:[62] If the earth's temperature increases significantly, a number of events might be expected to occur, including the melting of the Antarctic ice cap, a rise in sea levels, warming of the oceans, and an increase in photosynthesis. ...

But the topics and the preparation work done on the NATO proposal by the German authorities gained international momentum, (see e.g. the Stockholm United Nations Conference on the Human Environment 1970) as the government of Willy Brandt started to apply them on the civil sphere instead.

[66] A 1969 memo from White House Urban Affairs Director Daniel Patrick Moynihan tried to impress the office of U.S. President Nixon with the projected severity of the greenhouse effect.

[72] He summarized the knowledge of the science at the time, the anthropogenic attribution of the carbon dioxide greenhouse gas, distribution and exponential rise, findings which still hold today.

– John Sawyer, 1972The first satellite records compiled in the early 1970s showed snow and ice cover over the Northern Hemisphere to be increasing, prompting further scrutiny into the possibility of global cooling.

[76] The article drew on studies documenting the increasing snow and ice in regions of the Northern Hemisphere and concerns and claims by Reid Bryson that global cooling by aerosols would dominate carbon dioxide warming.

A rapid climatic change may result in large scale crop failures at a time when an increased world population taxes agriculture to the limits of productivity.

Simple global-scale estimates[83] that recently have been actualized[84] and confirmed by more refined model calculations[85][86] show noticeable contributions from waste heat to global warming after the year 2100, if its growth rates are not strongly reduced (below the averaged 2% p.a.

In a separate development, an analysis of deep-sea cores published in 1976 by Nicholas Shackleton and colleagues showed that the dominating influence on ice age timing came from a 100,000-year Milankovitch orbital change.

"[88] In July 1979 the United States National Research Council published a report,[89] concluding (in part): When it is assumed that the CO2 content of the atmosphere is doubled and statistical thermal equilibrium is achieved, the more realistic of the modeling efforts predict a global surface warming of between 2 °C and 3.5 °C, with greater increases at high latitudes.

... we have tried but have been unable to find any overlooked or underestimated physical effects that could reduce the currently estimated global warmings due to a doubling of atmospheric CO2 to negligible proportions or reverse them altogether.One week before President Carter left office, the White House Council on Environmental Quality (CEQ) issued reports including a suggestion to limit global average temperature to 2°C above preindustrial levels, one goal agreed to in the 2015 Paris climate accord.

[91]In 1982, Greenland ice cores drilled by Hans Oeschger, Willi Dansgaard, and collaborators revealed dramatic temperature oscillations in the space of a century in the distant past.

They concluded that the changes in the atmosphere due to human pollution "represent a major threat to international security and are already having harmful consequences over many parts of the globe", and declared that by 2005 the world would be well-advised to push its emissions some 20% below the 1988 level.

In the 1995 Second Assessment Report (SAR), the IPCC made the widely quoted statement that "The balance of evidence suggests a discernible human influence on global climate".

[169][170][171] The fresh, 1100–1500 billion tons (GT) per year of meltwater from the ice dilutes the saline Antarctic bottom water,[172][173] weakening the lower cell of the Southern Ocean overturning circulation (SOOC).

[177] Some climate change deniers have argued that solar variation is a significant contributor to the observed global warming, which would reduce the relative importance of human-made causes.

[222] Continuing with the current trend, particularly in the case of low-ambition form, there is an expectation of 3° Celsius temperature increase by the end of the century, which is estimated to bring severe environmental, economic, and social consequences.