As heat makes its way through the atmosphere instead of returning to Earth, it is absorbed by greenhouse gas molecules when it winds back to the planet’s surface. Certain gases, known as greenhouse gases, let sunlight shine directly onto the Earth’s surface but also capture the heat reflected into the atmosphere. Too much carbon dioxide and other greenhouse gases can cause the Earth’s atmosphere to capture more and more heat. The right amount of greenhouse gases in the atmosphere is crucial to ensuring that the atmosphere stores enough heat to support all kinds of life on Earth.
The greenhouse effect is a process in which radiation from the Earth’s atmosphere warms the Earth’s surface and surface temperature through the atmosphere. It is a phenomenon caused by the gases present in the atmosphere, which influence the behavior of the thermal energy emitted by the sun. This process, known as the greenhouse effect, occurs when the sun’s rays reach Earth’s atmosphere, but most of the radiation bounces off into space.
Greenhouse gases absorb infrared radiation in the form of heat that circulates through the atmosphere rather than being lost to space. If greenhouse gases increase the rate at which the atmosphere absorbs short wave radiation from the sun, this has a weak impact on global temperature. When greenhouse gases absorb this infrared radiation as a heat trap, however, capture it in the atmosphere, the greenhouse effect is created, leading to global warming and climate change.
The greenhouse effect is the warming of the earth’s surface and troposphere, the lower layers of the atmosphere, caused by the presence of water vapor, carbon dioxide, methane, and certain other gases in the air. The contribution of greenhouse gases to the greenhouse effect depends on how much heat they absorb, how much they release, and how long they remain in the atmosphere. The most abundant greenhouse gas is water vapor, which is different from other greenhouse gases in that changes in atmospheric concentration are linked to human activities, but also to the warming caused by the other greenhouse gas we emit.
This process takes place because the gases in the Earth’s atmosphere trap some of the solar heat and make the planet warmer than it would otherwise have been. This atmospheric greenhouse effect has kept the average temperature of the earth over billions of years many times higher and enabled the development of life as we know it. Since the loss of radiation energy in the atmosphere became more important than at the earth’s surface, the decrease in the concentration of water vapor was an important greenhouse gas.
By the end of 2019, combined impacts of long-lived greenhouse gases (atmospheric gases that absorb and emit heat) on Earth’s surface temperature had increased by 45% since 1990, the year countries signed the UN Kyoto Protocol, which was to serve as a benchmark for their efforts to reduce emissions from a baseline. If this trend continues and the emission of methane and other greenhouse gases rises, by 2100 the global average surface temperature could rise by 4.8 degrees Celsius relative to preindustrial levels. Over geological time the atmosphere has changed and in the past, there have been higher concentrations of greenhouse gases in the atmosphere, but never before has the Earth been exposed to such a large increase of these gases in the atmosphere in such a short period of time.
Man-made carbon dioxide emissions, the most commonly emitted greenhouse gas by human activities, continued from 1750 to 2010 and were largely generated over the past 40 years by burning fossil fuels and industrial processes.
According to the National Oceanic and Atmospheric Administration (NOAA) since the beginning of the Industrial Revolution in the early 19th century, burning fossil fuels such as coal, oil, and gasoline has increased the concentration of greenhouse gases in the atmosphere (CO 2). The greenhouse effect is a natural phenomenon, but it is possible that it is amplified as a result of human activities by the emission of greenhouse gases into the atmosphere. Since the beginning of the industrial revolution, human activities that burn coal and oil as fuel have increased the frequency of heat-trapping gases in the atmosphere and increased the greenhouse effect.
In 1859, John Tyndall showed that the greenhouse effect is due to the fact that only a small proportion of the main gases in the atmosphere have an effect: carbon dioxide has the most important effect due to water vapor and a small proportion of hydrocarbons. The planet Venus is experiencing an out-of-control greenhouse effect as a result of an atmosphere with 96% carbon dioxide at the surface and an atmospheric pressure equivalent to 900 m underwater on Earth. The IR radiation that escapes into space is absorbed by the atmosphere and greenhouse gases (water vapor, carbon dioxide, and methane) are excreted towards space, causing the surface to warm up further and heating the lower atmosphere.
Several stations around the world, including a number of Australian stations operated by the Bureau of Meteorology and CSIRO, monitor (CO 2) and other greenhouse gases and contribute to Global Atmosphere Watch’s data. The Annual Greenhouse Gas Index (AGGI) of NOAA is an annual report on the combined impact of long-lived greenhouse gases (atmospheric gases that absorb and emit heat) on the surface temperature of the Earth.
In terms of heat which are absorbed and re-emitted by the gases that contribute the most to the Earth’s greenhouse effect, the best known is global warming methane (GWP), which is 2.3 times more effective than nitrous oxide and 2.96 times less effective than carbon dioxide. All sectors of the global economy – production, agriculture, transport, and power generation – contribute greenhouse gases to the atmosphere and if they move away from fossil fuels, we can avoid some of the worst impacts of climate change.