The greenhouse effect is a process that occurs when energy from a planet's host star goes through its atmosphere and heats the planet's surface, but greenhouse gases in the atmosphere prevent some of the heat from returning directly to space, resulting in a warmer planet. Earth's natural greenhouse effect keeps the planet from having the below freezing temperature that it would have if there were no greenhouse gases. Additionally, human-caused increases in greenhouse gases trap greater amounts of heat, causing the Earth to grow warmer over time.
Global warming potential (GWP) is the heat absorbed by any greenhouse gas in the atmosphere, as a multiple of the heat that would be absorbed by the same mass of carbon dioxide. GWP is 1 for CO2. For other gases it depends on the gas and the time frame.
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.
There is a strong scientific consensus that the Earth is warming and that this warming is mainly caused by human activities. This consensus is supported by various studies of scientists' opinions and by position statements of scientific organizations, many of which explicitly agree with the Intergovernmental Panel on Climate Change (IPCC) synthesis reports.
The Global Warming Petition Project, also known as the Oregon Petition, is a group which urges the United States government to reject the Kyoto Protocol of 1997 and similar policies. Their petition challenges the scientific consensus on climate change. Though the group claims more than thirty-thousand signatories across various scientific fields, the authenticity and methods of the petitioners as well as the signatories' credentials have been questioned, and the project has been characterized as a disinformation campaign engaged in climate change denial.
Sherwood B. Idso is the president of the Center for the Study of Carbon Dioxide and Global Change, which rejects the scientific consensus on climate change. Previously he was a Research Physicist with the U.S. Department of Agriculture's Agricultural Research Service at the U.S. Water Conservation Laboratory in Phoenix, Arizona, where he worked since June 1967. He was also closely associated with Arizona State University over most of this period, serving as an Adjunct Professor in the Departments of Geology, Geography, and Botany and Microbiology. His two sons, Craig and Keith, are, respectively, the founder and vice president of the Center for the Study of Carbon Dioxide and Global Change.
This glossary of climate change is a list of definitions of terms and concepts relevant to climate change, global warming, and related topics.
Oceanic anoxic events or anoxic events (anoxia conditions) describe periods wherein large expanses of Earth's oceans were depleted of dissolved oxygen (O2), creating toxic, euxinic (anoxic and sulfidic) waters. Although anoxic events have not happened for millions of years, the geologic record shows that they happened many times in the past. Anoxic events coincided with several mass extinctions and may have contributed to them. These mass extinctions include some that geobiologists use as time markers in biostratigraphic dating. On the other hand, there are widespread, various black-shale beds from the mid-Cretaceous which indicate anoxic events but are not associated with mass extinctions. Many geologists believe oceanic anoxic events are strongly linked to the slowing of ocean circulation, climatic warming, and elevated levels of greenhouse gases. Researchers have proposed enhanced volcanism (the release of CO2) as the "central external trigger for euxinia."
Contemporary climate change includes both global warming and its impacts on Earth's weather patterns. There have been previous periods of climate change, but the current rise in global average temperature is more rapid and is primarily caused by humans. Burning fossil fuels adds greenhouse gases to the atmosphere, most importantly carbon dioxide and methane. Smaller contributions come from agriculture, industrial processes, and forest loss. Greenhouse gases warm the air by absorbing heat radiated by the Earth, trapping the heat near the surface. Greenhouse gas emissions amplify this effect, causing the Earth to take in more energy from sunlight than it can radiate back into space.
Greenhouse gas emissions from human activities strengthen the greenhouse effect, contributing to climate change. Most is carbon dioxide from burning fossil fuels: coal, oil, and natural gas. The largest emitters include coal in China and large oil and gas companies, many state-owned by OPEC and Russia. Human-caused emissions have increased atmospheric carbon dioxide by about 50% over pre-industrial levels. The growing levels of emissions have varied, but it was consistent among all greenhouse gases. Emissions in the 2010s averaged 56 billion tons a year, higher than ever before.
The Great Global Warming Swindle is a 2007 British polemical documentary film directed by Martin Durkin. The film denies the scientific consensus about the reality and causes of climate change, justifying this by suggesting that climatology is influenced by funding and political factors. The program was formally criticised by Ofcom, the UK broadcasting regulatory agency, which ruled the film failed to uphold due impartiality and upheld complaints of misrepresentation made by David King, who appeared in the film.
The Global Carbon Project (GCP) is an organisation that seeks to quantify global greenhouse gas emissions and their causes. Established in 2001, its projects include global budgets for three dominant greenhouse gases—carbon dioxide, methane, and nitrous oxide —and complementary efforts in urban, regional, cumulative, and negative emissions.
This is a list of climate change topics.
A greenhouse gas (GHG or GhG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3). Without greenhouse gases, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F). The atmospheres of Venus, Mars and Titan also contain greenhouse gases.
Atmospheric methane is the methane present in Earth's atmosphere. Atmospheric methane concentrations are of interest because it is one of the most potent greenhouse gases in Earth's atmosphere. Atmospheric methane is rising.
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.
Climate change feedbacks are important in the understanding of global warming because feedback processes amplify or diminish the effect of each climate forcing, and so play an important part in determining the climate sensitivity and future climate state. Feedback in general is the process in which changing one quantity changes a second quantity, and the change in the second quantity in turn changes the first. Positive feedback amplifies the change in the first quantity while negative feedback reduces it.
The atmospheric carbon cycle accounts for the exchange of gaseous carbon compounds, primarily carbon dioxide, between Earth's atmosphere, the oceans, and the terrestrial biosphere. It is one of the faster components of the planet's overall carbon cycle, supporting the exchange of more than 200 billion tons of carbon in and out of the atmosphere throughout the course of each year. Atmospheric concentrations of CO2 remain stable over longer timescales only when there exists a balance between these two flows. Methane, Carbon monoxide (CO), and other man-made compounds are present in smaller concentrations and are also part of the atmospheric carbon cycle.
Increasing methane emissions are a major contributor to the rising concentration of greenhouse gases in Earth's atmosphere, and are responsible for up to one-third of near-term global heating. During 2019, about 60% of methane released globally was from human activities, while natural sources contributed about 40%. Reducing methane emissions by capturing and utilizing the gas can produce simultaneous environmental and economic benefits.
Agriculture contributes towards climate change through greenhouse gas emissions and by the conversion of non-agricultural land such as forests into agricultural land. In 2019 the IPCC reported that 13%-21% of anthropogenic greenhouse gasses came specifically from the Agriculture, Forestry, and Other Land Uses Sector (AFOLU). Emissions from agriculture of nitrous oxide, methane and carbon dioxide make up to half of the greenhouse-gases produced by the overall food industry, or 80% of agricultural emissions. Animal husbandry is a major source of greenhouse gas emissions.
