Greenhouse gases

Water vapor is the main natural greenhouse gas, which is responsible for more than 60% of the effect.

At the same time, an increase in the Earth's temperature caused by other factors increases the evaporation and the total concentration of water vapor in the atmosphere at an almost constant relative humidity , which, in turn, increases the greenhouse effect. Thus, there is some positive feedback . On the other hand, increased humidity contributes to the development of cloud cover, and clouds in the atmosphere reflect direct sunlight, thereby increasing the Earth's albedo . Increased albedo leads to an anti-greenhouse effect , slightly reducing the total amount of incoming solar radiation and the daily heating of the atmosphere.

Sources of carbon dioxide in the Earth’s atmosphere are volcanic emissions, the vital activity of the biosphere , and human activity. Anthropogenic sources are: burning fossil fuels ; biomass burning, including deforestation ; some industrial processes lead to significant carbon dioxide emissions (e.g. cement production). The main consumers of carbon dioxide are plants , but in equilibrium, most biocenoses produce about as much carbon dioxide as they absorb from rotting biomass . Anthropogenic emissions increase the concentration of carbon dioxide in the atmosphere, which is supposedly the main factor in climate change. Carbon dioxide is a "long living" in the atmosphere. According to modern scientific ideas, the possibility of further accumulation of CO ₂ in the atmosphere is limited by the risk of unacceptable consequences for the biosphere and human civilization, and therefore its future emission budget is the final value. The concentration of carbon dioxide in the Earth’s atmosphere compared to the pre-industrial era (1750) in 2017 increased from 277 to 405 ppm by 146% ^[2] .

The lifetime of methane in the atmosphere is approximately 10 years. A relatively short life time combined with a large greenhouse potential makes it a candidate for mitigating the effects of global warming in the near future.

Until recently, it was believed that the greenhouse effect of methane was 25 times stronger than that of carbon dioxide. However, now the UN Intergovernmental Panel on Climate Change (IPCC) claims that the “greenhouse potential” of methane is even more dangerous than previously estimated. According to a recent IPCC report quoted by Die Welt, for 100 years, the greenhouse activity of methane is 28 times stronger than that of carbon dioxide, and 84 times in a 20-year period. ^{[3] [4]}

The main anthropogenic sources of methane are digestive fermentation in livestock, rice growing , biomass burning (including deforestation). Recent studies have shown that a rapid increase in the concentration of methane in the atmosphere occurred in the first millennium AD (presumably as a result of the expansion of agricultural production and cattle breeding and forest burning). Between 1000 and 1700, methane concentration fell by 40%, but began to increase again in recent centuries (presumably as a result of an increase in arable land, pasture and forest burning, the use of wood for heating, an increase in livestock, sewage , and rice cultivation ) . Leaks in the development of coal and natural gas deposits , as well as methane emissions from biogas generated at landfills , make some contribution to methane production .

An analysis of air bubbles in ice indicates that there is now more methane in the Earth’s atmosphere than at any time over the past 400,000 years. Since 1750, the average global atmospheric concentration of methane has increased by 257 percent from approximately 723 to 1859 ppmv (ppbv) in 2017 ^[2] . Over the past decade, although the concentration of methane continued to increase, the growth rate slowed down. In the late 1970s, growth rates were around 20 ppbv per year. In the 1980s, growth slowed to 9-13 ppbv per year. Between 1990 and 1998, there was an increase between 0 and 13 ppbv per year. Recent studies (Dlugokencky et al.) Show a steady-state concentration of 1751 ppbv between 1999 and 2002. ^[five]

Methane is removed from the atmosphere through several processes. The balance between methane emissions and its removal processes ultimately determines atmospheric concentrations and the residence time of methane in the atmosphere. Oxidation by a chemical reaction with hydroxyl radicals (OH) is dominant. Methane reacts with OH in the troposphere, producing CH ₃ and water. Stratospheric oxidation also plays a certain (insignificant) role in the removal of methane from the atmosphere. These two reactions with OH account for about 90% of methane removal from the atmosphere. In addition to the reaction with OH, two more processes are known: the microbiological absorption of methane in soils and the reaction of methane with chlorine atoms (Cl) on the sea surface. The contribution of these processes is 7% and less than 2%, respectively. ^[6]

Ozone is necessary for life, since it protects the Earth from the harsh ultraviolet radiation of the sun.

However, scientists distinguish between stratospheric and tropospheric ozone. The first (the so-called ozone layer) is a constant and basic protection against harmful radiation. The second is considered harmful, as it can be transported to the surface of the Earth and, due to its toxicity, harm living creatures. In addition, an increase in the content of tropospheric ozone specifically contributed to the growth of the greenhouse effect of the atmosphere. According to the most widely accepted scientific estimates, the contribution of ozone is about 25% of the contribution of CO ₂ ^[7]

Most tropospheric ozone is produced when nitrogen oxides (NO _x ), carbon monoxide (CO), and volatile organic compounds react in the presence of oxygen, water vapor, and sunlight. Transport, industrial emissions, as well as some chemical solvents are the main sources of these substances in the atmosphere. Methane, whose atmospheric concentration has increased significantly over the last century, also contributes to ozone formation. The life time of tropospheric ozone is approximately 22 days, the main mechanisms for its removal are soil binding, decomposition by ultraviolet rays and reactions with OH and NO ₂ radicals. ^[eight]

Concentrations of tropospheric ozone are characterized by a high level of variability and unevenness in geographical distribution. There is a system for monitoring tropospheric ozone levels in the USA ^[9] and Europe ^[10] , based on satellites and ground-based observation. Because sunlight is required for ozone formation, high levels of ozone are usually observed during periods of hot and sunny weather.

An increase in ozone concentration near the surface has a strong negative effect on vegetation, damaging leaves and inhibiting their photosynthetic potential. As a result of the historical process of increasing surface ozone concentration, the ability of the land surface to absorb CO ₂ was probably suppressed, and therefore, the growth rate of CO ₂ in the 20th century increased. Scientists (Sitch et al. 2007) believe that this indirect effect on climate almost doubled the contribution of surface ozone to climate change. Reducing ozone pollution of the lower troposphere can compensate for 1-2 decades of CO ₂ emission, while the economic costs will be relatively small (Wallack and Ramanathan, 2009). ^[eleven]

The greenhouse activity of nitrous oxide is 298 times higher than that of carbon dioxide. In addition, nitrogen oxides can affect the ozone layer as a whole.

Since 1750, the average global atmospheric concentration of nitrous oxide N ₂ O increased by 122 percent from approximately 269 to 329 ppmv (ppbv) in 2017 ^[2] .

The greenhouse activity of freons is 1300-8500 times higher than that of carbon dioxide. The main source of freon are refrigeration units and aerosols.

• Carbon geochemical cycle
• Kyoto Protocol
• The methane hydrate gun hypothesis
• Sulfuryl fluoride
• Adaptation to global climate change

Recommended

• Rifkin J. Beyond Beef: The Rise and Fall of the Cattle Culture . - N. Y .: , 1992. - XI, 353 p. - ISBN 0-525-93420-0 .

• Article on carbon dioxide concentration fluctuations
• Point Carbon is an analytical company specializing in providing independent estimates, forecasts, and information on trading in greenhouse gas emissions.
• "G C - atmosphere" automatic system for monitoring the quality of atmospheric air