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Carbon Cycle
by
Elena Lioubimtseva
LAST REVIEWED: 21 April 2021
LAST MODIFIED: 29 September 2014
DOI: 10.1093/obo/9780199874002-0107

Introduction

The global carbon cycle plays a central role in regulating atmospheric carbon dioxide (CO₂) levels and thus Earth’s climate. The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the atmosphere, the terrestrial biosphere, the oceans, sediments, and the Earth’s interior. It comprises a sequence of interrelated processes that are essential to making the Earth capable of sustaining life and regulating global climate. An examination of the carbon budget of a pool or reservoir can provide information about whether the pool or reservoir is functioning as a source or a sink for carbon dioxide. Accurate assessment of carbon pools, anthropogenic CO₂ emissions, and their redistribution among the atmosphere, ocean, and terrestrial biosphere is critically important to better understand the global carbon cycle, to project future climate changes, and to support the climate policy process.

General Overviews

Initially discovered by Joseph Priestley in the 18th century (Priestley 1970) and studied by chemists and biologists for more than three centuries, the carbon cycle has become a central subject of multidisciplinary and interdisciplinary studies during the past decades. Being an essential driver of the Earth’s climate system, the carbon cycle has attracted the interest of geographers, ecologists, soil scientists, climatologists, meteorologists, hydrologists, and geologists, as well as economists and political scientists. While a number of gases are implicated in global warming, carbon dioxide (CO₂) is the most important contributor, and in one sense the entire phenomenon can be seen as a human-induced perturbation of the carbon cycle. A very detailed interdisciplinary assessment of the state of knowledge of the carbon cycle in Field and Raupach 2004 consists of chapters by the world’s

Industrial revolution climate change

History of climate change science

Aspect of the history of science

The history of the scientific discovery of climate change began in the early 19th century when ice ages and other natural changes in paleoclimate were first suspected and the natural greenhouse effect was first identified. In the late 19th century, scientists first argued that human emissions of greenhouse gases could change Earth's energy balance and climate. The existence of the greenhouse effect, while not named as such, was proposed as early as 1824 by Joseph Fourier. The argument and the evidence were further strengthened by Claude Pouillet in 1827 and 1838. In 1856 Eunice Newton Foote demonstrated that the warming effect of the sun is greater for air with water vapour than for dry air, and the effect is even greater with carbon dioxide.

John Tyndall was the first to measure the infrared absorption and emission of various gases and vapors. From 1859 onwards, he showed that the effect was due to a very small proportion of the atmosphere, with the main gases having no effect, and was largely due to water vapor, though small percentages of hydrocarbons and carbon dioxide had a significant effect. The effect was more fully quantified by Svante Arrhenius in 1896, who made the first quantitative prediction of global warming due to a hypothetical doubling of atmospheric carbon dioxide.

In the 1960s, the evidence for the warming effect of carbon dioxide gas became increasingly convincing. Scientists also discovered that human activities that generated atmospheric aerosols (e.g., "air pollution") could have cooling effects as well (later referred to as global dimming). Other theories for the causes of global warming were also proposed, involving forces from volcanism to solar variation. During the 1970s, scientific understanding of global warming greatly increased.

By the 1990s, as the result of improving the accuracy of computer models

Columnist: Climate — The politicization of science

Published 12:00 am Tuesday, September 27, 2016

“It will be like weather forecasting on earth … One can’t predict the weather more than a few days in advance.” — Stephan Hawking (1942-), “Information Preservation and Weather Forecasting for Black Holes,” 2014.

“If you don’t like the weather in New England now, just wait a few minutes,” is a saying generally attributed to Mark Twain, a Missouri native, but Hartford resident for 17 years. Having grown up in New Hampshire and having lived my adult life in Connecticut, I can attest to the validity of his observation.

At a time when politicians – and politics – have become more divisive than at any point since the 1960s, few issues generate more hyperbole than “climate change,” or “global warming” as it was called last year. Climate, as those of us from New England well know, is in constant flux and always has been.

Global warming is a phenomenon that appears to be fact – at least in certain parts of the world. Arctic ice caps are shrinking, but those in Antarctica are getting bigger.

During the 1970s, the media was concerned about global cooling. Over millennia, the earth has warmed and cooled thousands of times. Mountains have risen, seas have been altered and deserts and jungles created – all before the advent of man.

William Happer, a physicist at Princeton and former director of the Department of Energy’s Office of Science during the first Bush administration, recently wrote a paper, “Harmful Politicization of Science.” He has been maligned by those who forbid counter-arguments to the narrative that man bears responsibility for climate change.

In the paper, Professor Happer explained he did not see great risk in warming trends, as they have not reached the same intensity as they had from roughly 900 AD to 1250 AD when vikings settled Iceland and Greenland. He wrote: “The current debates about global climate change are complicated by our not under