The global warming controversy concerns the public debate over whether global warming is occurring, how much has occurred in modern times, what has caused it, what its effects will be, whether any action can or should be taken to curb it, and if so what that action should be. In the scientific literature, there is a strong consensus that global surface temperatures have increased in recent decades and that the trend is caused by human-induced emissions of greenhouse gases. No scientific body of national or international standing disagrees with this view, though a few organizations with members in extractive industries hold non-committal positions, and some have tried to persuade the public that climate change is not happening, or if the climate is changing it is not because of human influence, attempting to sow doubt in the scientific consensus.
Global cooling was a conjecture, especially during the 1970s, of imminent cooling of the Earth culminating in a period of extensive glaciation, due to the cooling effects of aerosols or orbital forcing. Some press reports in the 1970s speculated about continued cooling; these did not accurately reflect the scientific literature of the time, which was generally more concerned with warming from an enhanced greenhouse effect.
The temperature record of the last 2,000 years is reconstructed using data from climate proxy records in conjunction with the modern instrumental temperature record which only covers the last 170 years at a global scale. Large-scale reconstructions covering part or all of the 1st millennium and 2nd millennium have shown that recent temperatures are exceptional: the Intergovernmental Panel on Climate Change Fourth Assessment Report of 2007 concluded that "Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1,300 years." The curve shown in graphs of these reconstructions is widely known as the hockey stick graph because of the sharp increase in temperatures during the last century. As of 2010 this broad pattern was supported by more than two dozen reconstructions, using various statistical methods and combinations of proxy records, with variations in how flat the pre-20th-century "shaft" appears. Sparseness of proxy records results in considerable uncertainty for earlier periods.
Hubert Horace Lamb was an English climatologist who founded the Climatic Research Unit in 1972 in the School of Environmental Sciences at the University of East Anglia.
John Raymond Christy is a climate scientist at the University of Alabama in Huntsville (UAH) whose chief interests are satellite remote sensing of global climate and global climate change. He is best known, jointly with Roy Spencer, for the first successful development of a satellite temperature record.
James Edward Hansen is an American adjunct professor directing the Program on Climate Science, Awareness and Solutions of the Earth Institute at Columbia University. He is best known for his research in climatology, his 1988 Congressional testimony on climate change that helped raise broad awareness of global warming, and his advocacy of action to avoid dangerous climate change. In recent years he has become a climate activist to mitigate the effects of global warming, on a few occasions leading to his arrest.
Wallace "Wally" Smith Broecker was an American geochemist. He was the Newberry Professor in the Department of Earth and Environmental Sciences at Columbia University, a scientist at Columbia's Lamont–Doherty Earth Observatory and a sustainability fellow at Arizona State University. He developed the idea of a global "conveyor belt" linking the circulation of the global ocean and made major contributions to the science of the carbon cycle and the use of chemical tracers and isotope dating in oceanography. Broecker popularized the term "global warming". He received the Crafoord Prize and the Vetlesen Prize.
Charles David Keeling was an American scientist whose recording of carbon dioxide at the Mauna Loa Observatory confirmed Svante Arrhenius's proposition (1896) of the possibility of anthropogenic contribution to the greenhouse effect and global warming, by documenting the steadily rising carbon dioxide levels. The Keeling Curve measures the progressive buildup of carbon dioxide, a greenhouse gas, in the atmosphere.
An abrupt climate change occurs when the climate system is forced to transition at a rate that is determined by the climate system energy-balance, and which is more rapid than the rate of change of the external forcing, though it may include sudden forcing events such as meteorite impacts. Abrupt climate change therefore is a variation beyond the variability of a climate. Past events include the end of the Carboniferous Rainforest Collapse, Younger Dryas, Dansgaard-Oeschger events, Heinrich events and possibly also the Paleocene–Eocene Thermal Maximum. The term is also used within the context of climate change to describe sudden climate change that is detectable over the time-scale of a human lifetime, possibly as the result of feedback loops within the climate system or tipping points.
Spencer R. Weart is the former director of the Center for History of Physics of the American Institute of Physics (AIP) from 1971 until his retirement in 2009.
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to Earth's climate. The current rise in global average temperature is more rapid than previous changes, and is primarily caused by humans burning fossil fuels. Fossil fuel use, deforestation, and some agricultural and industrial practices increase greenhouse gases, notably carbon dioxide and methane. Greenhouse gases absorb some of the heat that the Earth radiates after it warms from sunlight. Larger amounts of these gases trap more heat in Earth's lower atmosphere, causing global warming.
Hockey stick graphs present the global or hemispherical mean temperature record of the past 500 to 2000 years as shown by quantitative climate reconstructions based on climate proxy records. These reconstructions have consistently shown a slow long term cooling trend changing into relatively rapid warming in the 20th century, with the instrumental temperature record by 2000 exceeding earlier temperatures.
The Global Atmospheric Research Program was a fifteen-year international research programme led by the World Meteorological Organization and the International Council of Scientific Unions. It began in 1967 and organised several important field experiments including GARP Atlantic Tropical Experiment in 1974 and the Alpine Experiment (ALPEX) in 1982. Its field experiments helped make significant progress in meteorology in particular allowing major improvements in Numerical Weather Prediction.
Guy Stewart Callendar was an English steam engineer and inventor. His main contribution to human knowledge was developing the theory that linked rising carbon dioxide concentrations in the atmosphere to global temperature. He was the first to demonstrate that the Earth's land temperature had increased over the previous 50 years in 1938. This theory, earlier proposed by Svante Arrhenius, has been called the Callendar effect. Callendar thought this warming would be beneficial, delaying a "return of the deadly glaciers."
Climate change denial, or global warming denial, is denial, dismissal, or unwarranted doubt that contradicts the scientific consensus on climate change, including the extent to which it is caused by humans, its effects on nature and human society, or the potential of adaptation to global warming by human actions. Many who deny, dismiss, or hold unwarranted doubt about the scientific consensus on anthropogenic global warming self-label as "climate change skeptics", which several scientists have noted is an inaccurate description. Climate change denial can also be implicit when individuals or social groups accept the science but fail to come to terms with it or to translate their acceptance into action. Several social science studies have analyzed these positions as forms of denial or denialism, pseudoscience, or propaganda.
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. Many other theories of climate change were advanced, involving forces from volcanism to solar variation. In the 1960s, the evidence for the warming effect of carbon dioxide gas became increasingly convincing. Some scientists also pointed out that human activities that generated atmospheric aerosols could have cooling effects as well.
The Soon and Baliunas controversy involved the publication in 2003 of a review study written by the aerospace engineer Willie Soon and astronomer Sallie Baliunas in the journal Climate Research, which was quickly taken up by the George W. Bush administration as a basis for amending the first Environmental Protection Agency's Report on the Environment.
The Wegman Report was prepared in 2006 by three statisticians led by Edward Wegman at the request of Rep. Joe Barton of the United States House Committee on Energy and Commerce to validate criticisms made by Stephen McIntyre and Ross McKitrick of reconstructions of the temperature record of the past 1000 years, in particular the reconstructions by Mann, Bradley and Hughes of what had been dubbed the hockey stick graph.
The North Report was a 2006 report evaluating reconstructions of the temperature record of the past two millennia, providing an overview of the state of the science and the implications for understanding of global warming. It was produced by a National Research Council committee, chaired by Gerald North, at the request of Representative Sherwood Boehlert as chairman of the U.S. House of Representatives Committee on Science.
Climate communication or climate change communication is a field of environmental communication and science communication focused on the causes, nature and effects of anthropogenic climate change.
