Greenhouse gas is a gas that is transparent for invisibility and is highly absorbed in the infrared range. The release of such substances into the environment becomes the cause of the greenhouse effect.
Where do greenhouse gases come from?
Greenhouse gases are present in the atmospheres of all planets in the solar system. The high concentration of these substances becomes the cause of the phenomenon of the same name. It's about the greenhouse effect. For a start, it's worth saying about its positive side. It is thanks to this phenomenon that the optimum temperature is maintained on Earth for the origin and maintenance of various forms of life. Nevertheless, when the concentration of greenhouse gases is overestimated, one can speak of a serious environmental problem.
Initially, natural processes were the cause of the appearance of greenhouse gases. So, the first of them were formed as a result of the heating of the Earth by the sun's rays. Thus, part of the thermal energy did not go into outer space, but was reflected by gases. As a result, a heating effect was created, similar to that which occurs in greenhouses.
At the time when the Earth's climate was just forming, a significant proportion of greenhouse gases were produced by volcanoes. At that time, water vapor and carbon dioxide in huge quantities entered the atmosphere and concentrated in it. Then the greenhouse effect was so strong that the oceans literally boiled. And only with the advent of the green biosphere (plants) on the planet did the situation stabilize.
Today the problem of the greenhouse effect is especially urgent. It is largely due to the development of industry, as well as an irresponsible attitude towards natural resources. Oddly enough, industrial production is not the only cause of environmental degradation. Even such a seemingly harmless industry as agriculture is also a danger. The most destructive is animal husbandry (namely the waste products of cattle), as well as the use of chemical fertilizers. The cultivation of rice also adversely affects the atmosphere.
Water vapor
Water vapor is a naturally occurring greenhouse gas. Despite the fact that it looks harmless, it accounts for 60% of the greenhouse effect that causes global warming. Taking into account that the air temperature is constantly increasing, the value of the concentration of water vapor in the air becomes higher and higher, and therefore there is reason to speak of a closed circuit.
The so-called anti-greenhouse effect can be considered a positive side of water evaporation. This phenomenon consists in the formation of a significant mass of clouds. They, in turn, to some extent protect the atmosphere from overheating through exposure to sunlight. Some balance is maintained.
Carbon dioxide
Carbon dioxide is a greenhouse gas that is one of the most abundant in the atmosphere. Its source can be volcanic emissions, as well as the process of life of the biosphere (and especially humans). Of course, some of the carbon dioxide is absorbed by the plants. However, due to the decay process, they release a similar amount of this substance. Scientists argue that the subsequent increase in the concentration of gas in the atmosphere can lead to catastrophic consequences, and therefore, ways to purify the air are constantly being researched.
Methane
Methane is a greenhouse gas that lives in the atmosphere for about 10 years. Given that this period is relatively short, this substance has the greatest potential for eliminating the effects of global warming. Despite this, the greenhouse potential of methane is more than 25 times more dangerous than carbon dioxide.
The source of greenhouse gases (when it comes to methane) is the waste products of livestock, rice cultivation, and the combustion process. The highest concentration of this substance was observed in the first millennium, when agriculture and animal husbandry were the main activities. By 1700, this figure had dropped significantly. Over the past several centuries, the concentration of methane has begun to rise again, due to the large amount of fuel burned, as well as the development of coal deposits. At the moment, there is a record level of methane in the atmosphere. Nevertheless, over the past decade, the growth rate of this indicator has slightly slowed down.
Ozone
Without such a gas as ozone, life on Earth would be impossible, because it acts as a barrier from aggressive sunlight. But the protective function is performed only by stratospheric gas. If we talk about tropospheric, then it is toxic. If we take into account this greenhouse gas in terms of carbon dioxide, then it accounts for 25% of the effect of global warming.
The lifetime of harmful ozone is about 22 days. It is removed from the atmosphere by binding in soil and then decomposing by ultraviolet radiation. It is noted that the ozone content can vary significantly geographically.
Nitrous oxide
About 40% of nitrous oxide is released into the atmosphere due to the use of fertilizers and the development of the chemical industry. Most of this gas is produced in tropical regions. Up to 70% of the substance is emitted here.
New gas?
Canadian scientists recently announced that they had discovered a new greenhouse gas. Its name is perfluorotributylamine. Since the middle of the twentieth century, it has been used in the field of electrical engineering. This substance does not occur in nature. Scientists have found that PFTBA warms the atmosphere 7,000 times more than carbon dioxide. Nevertheless, at the moment the concentration of this substance is negligible and does not pose a threat to the environment.
At the moment, the task of researchers is to control the amount of this gas in the atmosphere. If there is an increase in the indicator, this can lead to a significant change in climatic conditions and radiation background. At the moment, there is no reason to take any measures to reorganize the production process.
A little about the greenhouse effect
In order to fully appreciate the destructive power of the greenhouse effect, it is worth paying attention to the planet Venus. Due to the fact that its atmosphere is almost entirely composed of carbon dioxide, the air temperature at the surface reaches 500 degrees. Given the emissions of greenhouse gases into the Earth's atmosphere, scientists do not exclude a similar development of events in the future. at the moment, the planet is largely saved by the oceans, which contribute to the partial purification of the air.
Greenhouse gases form a kind of barrier that interferes with the circulation of heat in the atmosphere. This is what causes the greenhouse effect. This phenomenon is accompanied by a significant increase in the average annual air temperature, as well as an increase in natural disasters (especially in coastal zones). This is fraught with the extinction of many species of animals and plants. At the moment, the situation is so serious that it is no longer possible to completely solve the problem of the greenhouse effect. Nevertheless, it is still possible to control this process and mitigate its consequences.
Possible consequences
Greenhouse gases in the atmosphere are the main cause of climate change towards warming. The consequences can be as follows:
- Increase in climate humidity due to increased precipitation. However, this is only true for those regions that are already constantly suffering from abnormal rainfall and snowfall. And in arid regions, the situation will become even more dire, leading to a shortage of drinking water.
- Sea level rise. This can lead to flooding of part of the territories of island and coastal states.
- Extinction of up to 40% of plant and animal species. This is a direct consequence of habitat change and growth.
- Reduction of glacier area, as well as snow melting on mountain peaks. It is dangerous not only in terms of extinction of flora and fauna, but also in terms of avalanches, mudflows and landslides.
- Decline in agricultural productivity in arid climates. Where conditions can be considered moderate, there is a possibility of higher yields, but this will not save the population from hunger.
- Lack of drinking water, which is associated with the draining of underground sources. This phenomenon may be associated not only with the overheating of the Earth, but also with the melting of glaciers.
- Deterioration of human health. This is due not only to deteriorating air quality and increased radiation, but also to a decrease in the amount of food.
Reducing greenhouse gas emissions
It is no secret that the state of the Earth's ecology is deteriorating every year. The calculation of greenhouse gases leads to disappointing conclusions, and therefore it becomes relevant to take measures to reduce the amount of emissions. This can be achieved as follows:
- increasing production efficiency in order to reduce the amount of energy resources used;
- protection and increase in the number of plants that act as sinks of greenhouse gases (rationalization of forestry);
- encouraging and supporting the development of forms of agriculture that do not harm the environment;
- development of financial incentives, as well as tax reduction for enterprises that operate in accordance with the concept of environmental responsibility;
- taking measures to reduce the emission of greenhouse gases from vehicles;
- increase in penalties for environmental pollution.
Greenhouse gas calculation
All business entities are obliged to regularly calculate the damage caused to the environment and submit reporting documentation to the relevant authorities. Thus, the quantitative determination of greenhouse gas emissions is carried out as follows:
- identification of the amount of fuel that is burned during the year;
- multiplying the obtained indicator by the emission factor for each type of gas;
- the emissions of each substance are converted to carbon dioxide equivalents.
Sources of emissions associated with fuel combustion
The development of scientific and technological progress, of course, makes life easier for humans, but causes irreparable harm to the environment. This is largely due to the combustion of fuel. In this regard, the sources of greenhouse gases can be as follows:
- Energy industry. This includes power plants that supply resources to industries and residential buildings.
- Industry and construction. This category includes enterprises in all industries. Accounting is carried out for fuel used in the production process, as well as for auxiliary needs.
- Transport. Harmful substances are emitted into the atmosphere not only by cars, but also by air vehicles, trains, water transport and pipelines. Only the fuel used for the direct movement of goods or passengers is taken into account. Energy costs for domestic transportation are not included here.
- Communal sector. This is the service sector and housing and communal services. What matters is the amount of fuel that was spent to ensure the final energy consumption.
The problem of greenhouse gases in Russia
The mass of greenhouse gas emissions in Russia is increasing every year. If we consider the structure of pollution by sector, the picture will be as follows:
- energy industry - 71%;
- fuel extraction - 16%;
- industrial production and construction - 13%.
Thus, the energy sector is a priority in the work to reduce emissions of harmful gases into the atmosphere. The indicator of resource use by domestic consumers is more than 2 times higher than the world indicator and 3 times higher than the European one. The potential to reduce energy consumption reaches 47%.
Conclusion
Greenhouse gas pollution is a global problem and is considered at the highest international level. Nevertheless, it concerns every single person. Thus, there must be a sense of personal responsibility for the environment. The minimum contribution of each person is the planting of green spaces, compliance with fire safety rules in forests, as well as the use of safe products and goods in everyday life. If we talk about future prospects, we can talk about the transition to electric vehicles and safe heating of residential buildings. Promotional and educational activities are called upon to make a huge contribution to the preservation of the environment.
Greenhouse gases
Greenhouse gases are gases that are believed to cause the global greenhouse effect.
The main greenhouse gases, in order of their estimated impact on the Earth's heat balance, are water vapor, carbon dioxide, methane, ozone, halocarbons and nitrogen oxide.
Water vapor
Water vapor is the main natural greenhouse gas responsible for more than 60% of the effect. The direct anthropogenic impact on this source is insignificant. At the same time, an increase in the Earth's temperature caused by other factors increases evaporation and the total concentration of water vapor in the atmosphere at a practically constant relative humidity, which, in turn, increases the greenhouse effect. Thus, there is some positive feedback.
Methane
A gigantic release of methane accumulated under the seabed 55 million years ago warmed the Earth by 7 degrees Celsius.
The same can happen now - this assumption was confirmed by researchers from NASA. Using computer simulations of the ancient climate, they tried to better understand the role of methane in its change. Most research on the greenhouse effect now focuses on the role of carbon dioxide in this effect, although the potential of methane to hold heat in the atmosphere exceeds that of carbon dioxide by 20 times.
A variety of gas-fired appliances contribute to the increase in atmospheric methane
Over the past 200 years, the methane content in the atmosphere has more than doubled due to the decomposition of organic remains in swamps and damp lowlands, as well as leaks from man-made objects: gas pipelines, coal mines, as a result of increased irrigation and the release of gases from livestock. But there is another source of methane - decaying organic residues in ocean sediments, preserved frozen under the seabed.
Usually, low temperatures and high pressures keep methane stable under the ocean, but this was not always the case. During periods of global warming, such as the thermal maximum of the Late Paleocene, which took place 55 million years ago and lasted 100 thousand years, the movement of lithospheric plates, in particular, the Indian subcontinent, led to a drop in pressure on the seabed and could cause a large release of methane. When the atmosphere and ocean began to warm up, methane emissions could increase. Some scientists believe that the current global warming could lead to the development of events according to the same scenario - if the ocean warms up significantly.
When methane is released into the atmosphere, it reacts with oxygen and hydrogen molecules to produce carbon dioxide and water vapor, each of which has the potential to cause a greenhouse effect. According to earlier forecasts, all emitted methane will turn into carbon dioxide and water in about 10 years. If this is the case, then the increase in carbon dioxide concentration will become the main reason for the warming of the planet. However, attempts to confirm the reasoning with references to the past were not crowned with success - no traces of an increase in the concentration of carbon dioxide 55 million years ago were found.
The models used in the new study showed that with a sharp increase in the level of methane in the atmosphere, the content of oxygen and hydrogen reacting with methane in it decreases (up to the termination of the reaction), and the rest of the methane remains in the air for hundreds of years, in itself becoming the cause of global warming. And these hundreds of years are quite enough to warm up the atmosphere, melt the ice in the oceans and change the entire climate system.
The main anthropogenic sources of methane are digestive fermentation in livestock, rice growing, biomass combustion (including deforestation). As recent studies have shown, a rapid increase in atmospheric methane concentration occurred in the first millennium AD (presumably as a result of the expansion of agricultural production and livestock raising and the burning of forests). Between 1000 and 1700, methane concentrations fell by 40%, but began to rise again in recent centuries (presumably as a result of an increase in arable land and pastures and the burning of forests, the use of wood for heating, an increase in livestock, sewage, rice cultivation) ... Some contribution to the flow of methane is provided by leaks during the development of coal and natural gas deposits, as well as the emission of methane in the composition of biogas generated at landfills.
Carbon dioxide
Sources of carbon dioxide in the Earth's atmosphere are volcanic emissions, the vital activity of organisms, and human activities. Anthropogenic sources are the burning of fossil fuels, the burning of biomass (including deforestation), some industrial processes (for example, the production of cement). Plants are the main consumers of carbon dioxide. Normally, the biocenosis absorbs approximately the same amount of carbon dioxide as it produces (including due to decay of the biomass).
Influence of carbon dioxide on the intensity of the greenhouse effect.
Much more needs to be studied about the carbon cycle and the role of the oceans as a huge storehouse of carbon dioxide. As mentioned above, humanity adds 7 billion tons of carbon in the form of CO 2 to the 750 billion tons available each year. But only about half of our emissions - 3 billion tons - remain in the air. This can be explained by the fact that most of the CO2 is used by terrestrial and marine plants, buried in marine sedimentary rocks, absorbed by sea water or otherwise absorbed. Of this large portion of CO2 (about 4 billion tons), the ocean absorbs about two billion tons of atmospheric carbon dioxide each year.
All this increases the number of unanswered questions: How exactly does sea water interact with atmospheric air, absorbing CO 2? How much more carbon can the seas absorb, and how much global warming could affect their capacity? What is the ability of the oceans to absorb and store heat trapped by climate change?
The role of clouds and suspended particles in air currents, called aerosols, is not easy to account for when constructing a climate model. Clouds obscure the earth's surface, leading to cooling, but depending on their height, density and other conditions, they can also trap heat reflected from the earth's surface, increasing the intensity of the greenhouse effect. The action of aerosols is also interesting. Some of them alter water vapor, condensing it into small droplets that form clouds. These clouds are very dense and shade the Earth's surface for weeks. That is, they block sunlight until they fall out with precipitation.
The combined effect can be enormous: the 1991 eruption of Mount Pinatuba in the Philippines threw a colossal amount of sulfates into the stratosphere, causing a worldwide drop in temperature that lasted two years.
Thus, our own pollution, caused mainly by the burning of sulfur-containing coal and oils, can temporarily mitigate the effects of global warming. Experts estimate that aerosols reduced warming by 20% during the 20th century. In general, temperatures have been on the rise since the 1940s but have dropped since 1970. The aerosol effect may help explain the abnormal cooling in the middle of the last century.
In 2006, carbon dioxide emissions into the atmosphere amounted to 24 billion tons. A very active group of researchers objects to the opinion that one of the causes of global warming is human activity. In her opinion, the main thing is in the natural processes of climate change and an increase in solar activity. But, according to Klaus Hasselmann, head of the German Climatological Center in Hamburg, only 5% can be attributed to natural causes, and the remaining 95% is a man-made factor caused by human activities.
Some scientists also do not associate an increase in CO2 volume with an increase in temperature. If the rise in temperature is blamed on increased CO2 emissions, skeptics say temperatures should have risen during the postwar economic boom, when huge quantities of fossil fuels were burned. However, Jerry Malman, director of the Geophysical Laboratory for Fluid Dynamics, calculated that the increased use of coal and oils rapidly increased the sulfur content in the atmosphere, causing a cold snap. After 1970, the thermic effect of the long life cycle of CO 2 and methane suppressed the rapidly decaying aerosols, causing an increase in temperature. Thus, it can be concluded that the influence of carbon dioxide on the intensity of the greenhouse effect is enormous and undeniable.
However, the increasing greenhouse effect may not be catastrophic. Indeed, high temperatures can be welcome where they are rare. Since 1900, the greatest warming has been observed from 40 to 70 0 N latitude, including Russia, Europe, the northern part of the United States, where industrial emissions of greenhouse gases first began. Much of the warming occurs at night, primarily due to increased cloud cover, which trapped the outgoing heat. As a result, the sowing season has increased by a week.
Moreover, the greenhouse effect may be good news for some farmers. A high concentration of CO 2 can have a positive effect on plants, as plants use carbon dioxide in the process of photosynthesis, converting it into living tissue. Consequently, more plants means more absorption of CO 2 from the atmosphere, slowing global warming.
This phenomenon has been studied by American experts. They decided to create a model of a world with a dual CO 2 content in the air. To do this, they used a fourteen-year-old pine forest in Northern California. Gas was pumped through pipes installed among the trees. Photosynthesis increased by 50-60%. But the effect was soon reversed. The choking trees couldn't handle that much carbon dioxide. The advantage in the process of photosynthesis has been lost. This is another example of how human manipulation leads to unexpected results.
But these small positive aspects of the greenhouse effect do not compare with the negative ones. Take, for example, the experience with the pine forest, where the volume of CO 2 was doubled, and by the end of this century, the concentration of CO 2 is predicted to quadruple. One can imagine how catastrophic the consequences for plants can be. And this, in turn, will increase the volume of CO 2, since the fewer the plants, the greater the concentration of CO 2.
Consequences of the greenhouse effect
greenhouse effect gases climate
As the temperature rises, the evaporation of water from oceans, lakes, rivers, etc. will increase. Since heated air can contain a larger volume of water vapor, this creates a powerful feedback effect: the warmer it gets, the higher the water vapor content in the air, and this, in turn, increases the greenhouse effect.
Human activities have little effect on the amount of water vapor in the atmosphere. But we are emitting other greenhouse gases, which makes the greenhouse effect more and more intense. Scientists believe that the increase in CO2 emissions, mainly from the burning of fossil fuels, explains at least about 60% of the warming on Earth since 1850. The concentration of carbon dioxide in the atmosphere is increasing by about 0.3% per year, and is now about 30% higher than before the industrial revolution. If this is expressed in absolute terms, then each year humanity adds about 7 billion tons. Despite the fact that this is a small part in relation to the total amount of carbon dioxide in the atmosphere - 750 billion tons, and even less compared to the amount of СО 2 contained in the World Ocean - about 35 trillion tons, it remains very significant. The reason: natural processes are in equilibrium, such a volume of CO 2 enters the atmosphere, which is removed from there. And human activity only adds CO 2.
Water vapor
Analysis of air bubbles in ice suggests that there is more methane in the Earth's atmosphere now than at any time in the past 400,000 years. Since 1750, the average global atmospheric methane concentration has increased by 150 percent from about 700 to 1745 parts per billion by volume (ppbv) in 1998. Over the past decade, while methane concentrations have continued to rise, the growth rate has slowed. In the late 1970s, the growth rate was around 20 ppbv per year. In the 1980s, growth slowed to 9-13 ppbv per year. Between 1990 and 1998, there was an increase of between 0 and 13 ppbv per year. Recent studies (Dlugokencky et al.) Show a steady concentration of 1751 ppbv between 1999 and 2002.
Methane is removed from the atmosphere through several processes. The balance between methane emissions and methane removal processes ultimately determines atmospheric concentrations and the residence time of methane in the atmosphere. The dominant is oxidation by means of a chemical reaction with hydroxyl radicals (OH). Methane reacts with OH in the troposphere to produce CH 3 and water. Stratospheric oxidation also plays some (minor) role in removing methane from the atmosphere. These two reactions with OH account for about 90% of the removal of methane from the atmosphere. In addition to the reaction with OH, two more processes are known: 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.
Ozone
Ozone is a greenhouse gas. At the same time, ozone is essential for life, as it protects the Earth from the sun's harsh ultraviolet radiation.
However, scientists distinguish between stratospheric and tropospheric ozone. The first (the so-called ozone layer) is a permanent and basic protection against harmful radiation. The second is considered harmful, since it can be transported to the surface of the Earth, where it harms living beings, and, moreover, is unstable and cannot be a reliable protection. In addition, the increase in the tropospheric ozone content has contributed to the growth of the greenhouse effect of the atmosphere, which (according to the most widespread scientific estimates) is about 25% of the contribution of СО 2
Most tropospheric ozone is formed when nitrogen oxides (NOx), carbon monoxide (CO) and volatile organic compounds chemically react in the presence of sunlight. Transport, industrial emissions, and some chemical solvents are the main sources of these substances in the atmosphere. Methane, whose atmospheric concentration has increased significantly over the past century, also contributes to the formation of ozone. The lifetime of tropospheric ozone is approximately 22 days, and the main mechanisms for its removal are soil binding, decomposition by ultraviolet rays, and reactions with OH and HO 2 radicals.
Tropospheric ozone concentrations are highly variable and uneven in geographic distribution. There is a system for monitoring tropospheric ozone levels in the United States and Europe, based on satellites and ground-based observations. Because ozone requires sunlight to form, high ozone levels are typically observed during periods of hot and sunny weather. The current average concentration of tropospheric ozone in Europe is three times higher than in the pre-industrial era.
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 the concentration of ground-level ozone, the ability of the land surface to absorb CO2 was probably suppressed and therefore the rate of CO2 growth increased in the 20th century. Scientists (Sitch et al. 2007) believe that this indirect climate impact has nearly doubled the contribution of ground-level ozone to climate change. Reducing ozone pollution of the lower troposphere could offset 1–2 decades of CO 2 emissions, with relatively small economic costs (Wallack and Ramanathan, 2009).
Nitric oxide
The greenhouse activity of nitrous oxide is 298 times higher than that of carbon dioxide.
Freons
The greenhouse activity of freons is 1300-8500 times higher than that of carbon dioxide. Refrigeration units and aerosols are the main sources of freon.
see also
- Kyoto Protocol (CO 2, CH 4, HFCs, PFCs, N 2 O, SF 6)
Notes (edit)
Links
- Point Carbon is an analytical company specializing in providing independent estimates, projections, and information on greenhouse gas emissions trading.
- "GIS - atmosphere" automatic air quality monitoring system
| Climate, Climatology | |
|---|---|
| Changing of the climate | Paleoclimatology El Niño Geochemical cycle of carbon Proterozoic glaciation, Ice age, Little ice age Thermal maximum (Late Paleocene thermal maximum, Last glacial maximum) Glaciers Heat turnover |
| Global warming | Deforestation Countering climate change Global climate model Global cooling Global blackout Ozone hole Greenhouse effect Carbon dioxide Greenhouse gases Intergovernmental Panel on Climate Change United Nations Framework Convention on Climate Change (Kyoto Protocol) Peak oil Renewable energy Temperature trend Sea level rise Copenhagen Consenus |
Wikimedia Foundation. 2010.
The greenhouse effect in the atmosphere of our planet is caused by the fact that the flow of energy in the infrared range of the spectrum, rising from the Earth's surface, is absorbed by the molecules of gases in the atmosphere, and is radiated back in different directions, as a result, half of the energy absorbed by the molecules of greenhouse gases returns back to the surface of the Earth, causing it warming up. It should be noted that the greenhouse effect is a natural atmospheric phenomenon (Fig. 5). If there were no greenhouse effect on Earth at all, then the average temperature on our planet would be about -21 ° С, and so, thanks to greenhouse gases, it is + 14 ° С. Therefore, purely theoretically, human activities associated with the release of greenhouse gases into the Earth's atmosphere should lead to further warming up of the planet. The main greenhouse gases, in order of their estimated impact on the Earth's heat balance, are water vapor (36-70%), carbon dioxide (9-26%), methane (4-9%), halocarbons, and nitrogen oxide.
Rice.
Coal-fired power plants, factory chimneys, car exhaust and other human-made sources of pollution collectively emit about 22 billion tons of carbon dioxide and other greenhouse gases into the atmosphere per year. Livestock raising, the use of fertilizers, coal combustion and other sources provide about 250 million tons of methane per year. About half of all greenhouse gases emitted by humankind remain in the atmosphere. About three quarters of all anthropogenic greenhouse gas emissions over the past 20 years are caused by the use of oil, natural gas and coal (Fig. 6). Much of the rest is due to landscape changes, primarily deforestation.
Rice.
Water vapor is the most important greenhouse gas today. However, water vapor is also involved in many other processes, which makes its role far from unambiguous in different conditions.
First of all, during evaporation from the Earth's surface and further condensation in the atmosphere, up to 40% of all heat entering the atmosphere is transferred to the lower atmosphere (troposphere) due to convection. Thus, the water vapor during evaporation somewhat lowers the surface temperature. But the heat released as a result of condensation in the atmosphere goes to warm it up, and then, to warm up the surface of the Earth itself.
But after condensation of water vapor, water droplets or ice crystals are formed, which actively participate in the processes of scattering of sunlight, reflecting part of the solar energy back into space. Clouds, which are just clusters of these droplets and crystals, increase the fraction of solar energy (albedo) reflected by the atmosphere itself back into space (and then precipitation from the clouds can fall in the form of snow, increasing the surface albedo).
However, water vapor, even condensed into droplets and crystals, still has powerful absorption bands in the infrared region of the spectrum, which means that the role of the same clouds is far from unambiguous. This duality is especially noticeable in the following extreme cases - when the sky is covered with clouds in sunny summer weather, the temperature on the surface decreases, and if the same thing happens on a winter night, then on the contrary, it rises. The final result is also influenced by the position of the clouds - at low altitudes, powerful clouds reflect a lot of solar energy, and the balance may be in this case in favor of the anti-greenhouse effect, but at high altitudes, rarefied cirrus clouds let a lot of solar energy go down, but even rarefied clouds are almost insurmountable obstacles to infrared radiation and, and here we can talk about the predominance of the greenhouse effect.
Another feature of water vapor is that the humid atmosphere to some extent contributes to the binding of another greenhouse gas - carbon dioxide, and its transport by rainfall to the Earth's surface, where it, as a result of further processes, can be consumed in the formation of carbonates and combustible minerals.
Human activity has a very weak direct effect on the content of water vapor in the atmosphere - only due to an increase in the area of irrigated lands, changes in the area of swamps and the work of energy, which is negligible against the background of evaporation from the entire water surface of the Earth and volcanic activity. Because of this, quite often little attention is paid to it when considering the problem of the greenhouse effect.
However, the indirect effect on the water vapor content can be very large, due to the inverse relationships between the water vapor content in the atmosphere and the warming caused by other greenhouse gases, which we will now consider.
It is known that as the temperature rises, the evaporation of water vapor also increases, and for every 10 ° C the possible content of water vapor in the air almost doubles. For example, at 0 ° С the saturated vapor pressure is about 6 mb, at + 10 ° С - 12 mb, and at + 20 ° С - 23 mb.
It can be seen that the content of water vapor strongly depends on the temperature, and when it decreases for some reason, firstly, the greenhouse effect of water vapor itself decreases (due to the decreased content), and secondly, condensation of water vapor occurs, which, of course, the decrease in temperature is greatly slowed down due to the release of condensation heat, but after condensation, the reflection of solar energy increases, both of the atmosphere itself (scattering by droplets and ice crystals) and the surface (snow fall), which further lowers the temperature.
As the temperature rises, the content of water vapor in the atmosphere increases, its greenhouse effect increases, which intensifies the initial temperature rise. In principle, cloudiness also grows (more water vapor enters relatively cold regions), but extremely weakly - according to I. Mokhov, about 0.4% per degree of warming, which cannot greatly affect the growth of solar energy reflection.
Carbon dioxide- the second largest contributor to the greenhouse effect today, does not freeze out when the temperature drops, and continues to create a greenhouse effect even at the lowest temperatures possible under terrestrial conditions. Probably, it was precisely due to the gradual accumulation of carbon dioxide in the atmosphere due to volcanic activity that the Earth was able to get out of the state of the most powerful glaciations (when even the equator was covered with a thick layer of ice), into which it fell at the beginning and end of the Proterozoic.
Carbon dioxide is involved in a powerful carbon cycle in the lithosphere-hydrosphere-atmosphere system, and the change in the Earth's climate is associated primarily with a change in the balance of its entry into the atmosphere and removal from it.
Due to the relatively high solubility of carbon dioxide in water, the content of carbon dioxide in the hydrosphere (primarily the oceans) is now 4x104 Gt (gigatons) of carbon (henceforth, data on CO2 are given in terms of carbon), including the deep layers (Putvinsky, 1998). The atmosphere currently contains about 7.5x102 Gt of carbon (Alekseev et al. 1999). The content of CO2 in the atmosphere was not always low - so in the Archean (about 3.5 billion years ago) the atmosphere consisted of almost 85-90% of carbon dioxide, at significantly higher pressure and temperature (Sorokhtin and Ushakov, 1997). However, the influx of significant masses of water to the Earth's surface as a result of degassing of the interior, as well as the emergence of life, ensured the binding of almost all atmospheric and a significant part of carbon dioxide dissolved in water in the form of carbonates (about 5.5x107 Gt of carbon are stored in the lithosphere (IPCC report, 2000)) ... Also, carbon dioxide began to be converted by living organisms into various forms of combustible minerals. In addition, the binding of a part of carbon dioxide occurred due to the accumulation of biomass, the total carbon reserves of which are comparable to those in the atmosphere, and taking into account the soil, they exceed several times.
However, we are primarily interested in flows that ensure the flow of carbon dioxide into the atmosphere and remove it from it. The lithosphere now provides a very small flow of carbon dioxide entering the atmosphere primarily due to volcanic activity - about 0.1 Gt of carbon per year (Putvinsky, 1998). Significantly large flows are observed in the systems ocean (together with organisms living there) - atmosphere, and terrestrial biota - atmosphere. About 92 Gt of carbon is supplied to the ocean annually from the atmosphere, and 90 Gt is returned to the atmosphere (Putvinsky, 1998). Thus, the ocean annually extracts about 2 Gt of carbon from the atmosphere. At the same time, in the processes of respiration and decomposition of dead terrestrial living creatures, about 100 Gt of carbon per year enter the atmosphere. In the processes of photosynthesis, terrestrial vegetation also removes about 100 Gt of carbon from the atmosphere (Putvinsky, 1998). As we can see, the mechanism of input and output of carbon from the atmosphere is quite balanced, providing approximately equal fluxes. Modern human activity includes in this mechanism an ever-increasing additional flow of carbon into the atmosphere due to the combustion of fossil fuels (oil, gas, coal, etc.) - according to data, for example, for the period 1989-99, an average of about 6.3 Gt in year. The flow of carbon into the atmosphere also increases due to deforestation and partial combustion of forests - up to 1.7 Gt per year (IPCC report, 2000), while the increase in biomass contributing to the absorption of CO2 is only about 0.2 Gt per year instead of almost 2 Gt in year. Even taking into account the possibility of absorption of about 2 Gt of additional carbon by the ocean, there is still a rather significant additional flux (currently about 6 Gt per year), increasing the content of carbon dioxide in the atmosphere. In addition, the absorption of carbon dioxide by the okan may decrease in the near future, and the reverse process is even possible - the release of carbon dioxide from the oceans. This is due to a decrease in the solubility of carbon dioxide when the water temperature rises - for example, when the water temperature rises from only 5 to 10 ° C, the solubility coefficient of carbon dioxide in it decreases from about 1.4 to 1.2.
So, the flow of carbon dioxide into the atmosphere caused by economic activity is not large compared to some natural flows, however, its uncompensation leads to a gradual accumulation of CO2 in the atmosphere, which destroys the balance of CO2 intake and removal, formed over billions of years of evolution of the Earth and life on it.
Numerous facts from the geological and historical past indicate the relationship between climate change and fluctuations in greenhouse gases. In the period from 4 to 3.5 billion years ago, the brightness of the Sun was about 30% less than it is now. However, even under the rays of the young, "pale" Sun, life developed on Earth and sedimentary rocks were formed: at least on a part of the earth's surface, the temperature was above the freezing point of water. Some scientists suggest that at that time in the earth's atmosphere contained an axis 1000 times larger carbon dioxide than now, and this made up for the lack of solar energy, as more heat emitted by the Earth remained in the atmosphere. The growing greenhouse effect could become one of the reasons for the extremely warm climate later - in the Mesozoic era (the era of the dinosaurs). According to the analysis of fossil remains on the Earth at that time it was 10-15 wasps warmer than it is now. It should be noted that then, 100 million years ago and earlier, the continents occupied a different position than in our time, and the oceanic circulation was also different, therefore, the transfer of heat from the tropics to the polar regions could be greater. However, calculations carried out by Eric J. Barron, now at the University of Pennsylvania, and other researchers show that no more than half of the Mesozoic warming could be associated with paleocontinental geography. The rest of the warming is easily explained by the increase in carbon dioxide content. This assumption was first put forward by Soviet scientists A. B. Ronov from the State Hydrological Institute and M. I. Budyko from the Main Geophysical Observatory. Calculations supporting this proposal were carried out by Eric Barron, Starley L. Thompson of the National Center for Atmospheric Research (NCAR). From a geochemical model developed by Robert A. Berner and Antonio C. Lasaga of Yale University and the late Robert. Fields in Texas turned into a desert after a drought lasted for some time here in 1983. This pattern, as calculations using computer models show, can be observed in many places if, as a result of global warming, soil moisture in the central regions of the continents decreases. where grain production is concentrated.
M. Garrels of the University of South Florida, it follows that carbon dioxide could be released during extremely strong volcanic activity on the mid-ocean ridges, where rising magma forms a new ocean floor. Direct evidence of a link between atmospheric greenhouse gases and climate during glaciers can be “extracted” from air bubbles embedded in Antarctic ice that formed in ancient times as a result of the compaction of falling snow. A team of researchers, led by Claude Laurue of the Laboratory of Glaciology and Geophysics in Grenoble, studied a 2000 m long ice column (corresponding to a period of 160 thousand years) obtained by Soviet researchers at the Vostok station in Antarctica. Laboratory analysis of the gases contained in this ice column showed that in the ancient atmosphere the concentrations of carbon dioxide and methane changed in concert and, more importantly, "in time" with changes in the average local temperature (it was determined by the ratio of the concentrations of hydrogen isotopes in water molecules ). During the last interglacial period, which lasted already 10 thousand years, and in the interglacial period preceding it (130 thousand years ago), also lasting 10 thousand years, the average temperature in this area was 10 ° C higher than during the glaciations. (On the whole, the Earth during the indicated periods was 5 was warmer.) During the same periods, the atmosphere contained 25% more carbon dioxide and 100070 more methane than during the glaciations. It is unclear whether the change in greenhouse gas emissions was caused by climate change or vice versa. Most likely, the cause of glaciations was changes in the Earth's orbit and the special dynamics of the advance and retreat of glaciers; however, these climatic fluctuations may have been amplified by changes in biota and fluctuations in ocean circulation that affect atmospheric greenhouse gases. Even more detailed data on fluctuations in greenhouse gases and climate change are available for the last 100 years, over which there has been a further 25% increase in carbon dioxide and 100% methane. "Records" of the average temperature of the globe for the past 100 years have been studied by two research teams led by James E. Hansen of the Goddard Space Research Institute of the National Aeronautics and Space Administration, and T.M.L. England.
The retention of heat by the atmosphere is the main component of the Earth's energy balance (Fig. 8). About 30% of the energy coming from the Sun is reflected (left) either from clouds, particles, or the surface of the Earth; the remaining 70% is absorbed. The absorbed energy is re-emitted in the infrared range by the surface of the planet.
Rice.
These scientists used measurements from meteorological stations scattered across continents (the Climate team also included marine measurements in the analysis). At the same time, two groups adopted different methods for analyzing observations and accounting for "distortions" associated, for example, with the fact that some meteorological stations "moved" to another location in a hundred years, and some located in cities gave data that were "polluted »The influence of heat generated by industrial plants or accumulated daily by buildings and pavements. The latter effect, leading to the appearance of "heat islands", is very noticeable in developed countries, for example, in the United States. However, even if the estimated US correction (obtained by Thomas R. Karl from the National Climate Data Center in Asheville, North Carolina, and by PD Jones from the University of East Anglia) were extended to all data around the globe, both entries will contain “<реальное» потепление величиной 0,5 О С, относящееся к последним 100 годам. В согласии с общей тенденцией 1980-е годы остаются самым теплым десятилетием, а 1988, 1987 и 1981 гг. - наиболее теплыми годами (в порядке перечисления). Можно ли считать это «сигналом» парникового потепления? Казалось бы, можно, однако в действительности факты не столь однозначны. Возьмем для примера такое обстоятельство: вместо неуклонного потепления, какое можно ожидать от парникового эффекта, быстрое повышение температуры, происходившее до конца второй мировой войны, сменилось небольшим похолоданием, продлившимся до середины 1970-х годов, за которым последовал второй период быстрого потепления, продолжающийся по сей день. Какой характер примет изменение температуры в ближайшее время? Чтобы дать такой прогноз, необходимо ответить на три вопроса. Какое количество диоксида углерода и других парниковых газов будет выброшено в атмосферу? Насколько при этом возрастет концентрация этих газов в атмосфере? Какой климатический эффект вызовет это повышение концентрации, если будут действовать естественные и антропогенные факторы, которые могут ослаблять или усиливать климатические изменения? Прогноз выбросов - нелегкая задача для исследователей, занимающихся анализом человеческой деятельности. Какое количество диоксида углерода попадет в атмосферу, зависит главным образом от того, сколько ископаемого топлива будет сожжено и сколько лесов вырублено (последний фактор ответствен за половину прироста парниковых газов с 1800 г. и за 20070прироста в наше время). И тот и другой фактор зависят в свою очередь от множества причин. Так, на потреблении ископаемого топлива сказываются рост населения, переход к альтернативным источникам энергии и меры по экономии энергии, а также состояние мировой экономики. Прогнозы в основном сводятся к тому, что потребление ископаемого топлива на земном шаре в целом будет увеличиваться примерно с той же скоростью, что и сегодня намного медленнее, чем до энергетического кризиса 1970-х годов. В результате эмиссия (поступление в атмосферу) диоксида углерода в ближайшие несколько десятилетий, будет увеличиваться на 0,5-2070 в год. Другие парниковые газы, такие как ХФУ, оксиды азота и тропосферный озон, могут вносить в потепление климата почти столь же большой вклад, что и диоксид углерода, хотя в атмосферу их попадает значительно меньше: объясняется это тем, что они более эффективно поглощают солнечную радиацию. Предсказать, какова будет эмиссия этих газов - задача еще более трудная. Так, например, не вполне ясно происхождение некоторых газов, в частности метана; величина выбросов других газов, таких как ХФУ или озон, будет зависеть от того, какие изменения в технологии и политике произойдут в ближайшем будущем.
Carbon exchange between the atmosphere and various "reservoirs" on the Earth (Fig. 9). Each number indicates in billions of tons of carbon input or output (in the form of dioxide) per year, or its stock in a reservoir. In these natural cycles, one of which "closes" on land and the other on the ocean, just as much carbon dioxide is removed from the atmosphere as it enters, but human activities - deforestation and burning fossil fuels - lead to the fact that the carbon content in the atmosphere annually increases by 3 billion tons. Data from Stockholm University Bert Bohlin
Fig. 9
Let's assume we have a reasonable prediction of how carbon dioxide emissions will change. What changes in this case will occur with the concentration of this gas in the atmosphere? Atmospheric carbon dioxide is “consumed” by plants, as well as by the ocean, where it is consumed in chemical and biological processes. As the concentration of atmospheric carbon dioxide changes, the rate of "consumption" of this gas will likely change. In other words, the processes that cause changes in the content of atmospheric carbon dioxide must include feedback. Carbon dioxide is a “feedstock” for photosynthesis in plants, so its consumption by plants is likely to increase with its accumulation in the atmosphere, which will slow down this accumulation. Likewise, since the content of carbon dioxide in ocean surface waters is in approximate equilibrium with that in the atmosphere, an increase in the absorption of carbon dioxide in ocean water will slow down its accumulation in the atmosphere. It may happen, however, that the accumulation of carbon dioxide and other greenhouse gases in the atmosphere will trigger positive Feedback mechanisms that will amplify the climate effect. For example, rapid climate change can lead to the disappearance of some forests and other ecosystems, which will weaken the biosphere's ability to absorb carbon dioxide. Moreover, warming can lead to a rapid release of carbon from dead organic matter in the soil. This carbon, which is twice the amount in the atmosphere, is constantly converted to carbon dioxide and methane by soil bacteria. Warming can make them "work" faster, resulting in faster release of carbon dioxide (from dry soils) and methane (from rice paddies, landfills and wetlands). Quite a lot of "methane is also stored in sediments on the continental shelf and below the permafrost layer in the Arctic in the form of clathrates - molecular lattices consisting of methane and water molecules. Warming of shelf waters and melting of permafrost can lead to the release of methane. Despite these uncertainties, Many researchers believe that the uptake of carbon dioxide by plants and the ocean will slow the accumulation of this gas in the atmosphere - at least for the next 50-100 years.Typical estimates based on current emission rates show that of all carbon dioxide entering into the atmosphere, about half will remain there. This implies that a doubling of the concentration of carbon dioxide in comparison with 1900 (to the level of 600 million will occur approximately between 2030 and 2080. However, other greenhouse gases will most likely accumulate in the atmosphere faster.
The main reason for the influence on the climate is considered to be the increase in the share of greenhouse gases in the atmosphere, leading to an increase in temperature, followed by melting of glaciers and a rise in ocean levels, which will cause a radical change in the global climate. Over 130 years, from 1860 to 1990, the average global temperature of the atmosphere increased by 1 ° С and this trend continues to the present
For the first time, the idea of the greenhouse effect was expressed by J. B. Fourier in 1827. According to him, the atmosphere is like a transparent glass shell, which allows sunlight to penetrate to the earth's surface, but traps the latent radiation of the earth.
The essence greenhouse effect is as follows: greenhouse gases act as glass, with the result that heat is concentrated under the shell they create around the earth. The energy of light, penetrating through the atmosphere, is absorbed by the surface of our planet, turns into heat and is released in the form of heat. Heat, as you know, unlike light, does not go out through the glass, but accumulates inside the greenhouse, significantly increasing the air temperature and increasing evaporation. The main absorber of thermal radiation from the Sun and the earth's surface is water, which is present in the form of vapors and clouds. Less than 7% of the radiation emitted by the earth's surface passes through "transparency windows", but these windows are significantly reduced due to the presence of greenhouse gas molecules in the atmosphere.
Greenhouse gases
Methane... Global warming of 12% is due to methane (CH 4). It is formed in the process of anaerobic bacterial decomposition in swamps, rice fields and landfills, in the stomachs of cows and sheep and in the intestines of termites, leaks from gas wells, gas pipelines, stoves, furnaces. Over the past decades, the methane content has increased due to the increase in the area under rice, as well as as a result of the creation of large livestock farms. Methane remains in the troposphere for about 11 years. Each CH 4 molecule contributes to the greenhouse effect 25 times more than a CO 2 molecule. Methane emissions are increasing by 1% per year.
Nitrous oxide... Global warming of 6% is due to nitrous oxide (N 2 O). It is released during the decomposition of nitrogen fertilizers in soils, from the effluent of livestock farms, and during the combustion of biomass. It persists in the troposphere for an average of 150 years. Every molecule N 2 O is 230 times more effective in contributing to global warming than the CO 2 molecule. Emissions increase by 0.2% annually.
As a result of warming, irreparable damage to the fate of our planet may occur: the glaciers of Greenland, the Arctic Ocean, the South Pole, and finally, mountain glaciers will begin to melt; the level of the World Ocean will rise significantly (by 1.5-2 m and more). The average temperature of Antarctica will increase by 5 ° C, which is enough for the entire ice cap to melt. The level of the World Ocean will rise by 4.5-8 m everywhere and flood of many coastal areas (Shanghai, Cairo, Venice, Bangkok, large areas of fertile lowlands in India will be flooded), and millions of people will be forced to migrate inland, to mountainous regions; the influence of the ocean on land will increase through the intensification of storms, ebbs and flows. The equalization of temperature at the equator and the poles will lead to a disruption of the current circulation of the atmosphere, a change in the precipitation regime (scarce precipitation in the areas of agriculture), and a decrease in the production of grain, meat and other food products. The hope for irrigation of these territories is not great, because today the level of groundwater has dropped markedly, and by the middle of the century, their reserves will practically be used up. The influence of the "greenhouse effect" on the regional climate is already beginning to manifest itself: prolonged droughts in South Africa (5 years), North America (6 years), warm winters, etc.
Carbon dioxide... Intensive deforestation, burning of fuel, garbage very noticeably disrupts the existing balance of carbon dioxide in the atmosphere. Each carbon atom of the fuel attaches two oxygen atoms when burning to form carbon dioxide, so the mass of carbon dioxide increases compared to the mass of the fuel burned (1 kg of fuel → 3 kg of CO 2). At present, this gas is responsible for an intense warming of 57%. CO2 emissions increase by 4% annually.
Fluorocarbons(FHU, or CFC). The content of CFCs in the atmosphere is small compared to CO 2, but they have a rather high heat capacity: they absorb heat much more intensively (50 times higher) than carbon dioxide. These gases account for 25% of global warming. The main sources are leaks from air conditioners, evaporation from aerosol dispensers. CFCs can remain in the atmosphere for 22 to 111 years, depending on their type. CFC emissions increase by 5% annually.
The commercial production of fluorocarbons, often called freons, began in the mid-1930s. The largest amount of freon-11 (СFС1 3) and freon-12 (СF 2 С1 2) was used as foaming agents in the production of porous polymeric materials, fillers in aerosol packages, as well as refrigerants in refrigerators and air conditioners. Some CFCs were used as degreasing agents: freon-113 (C 2 F 3 C1 3) and freon-114 (C 2 F 4 C1 2). Later, due to the high chlorine content, the above freons were replaced by CHC1P 2, which destroys ozone to a lesser extent, but absorbs infrared rays to a greater extent and especially actively affects the greenhouse effect during its stay in the troposphere.
What are freons
In 1931, when a refrigerant, harmless to the human body, was synthesized - freon. Subsequently, more than four dozen different freons were synthesized, differing from each other in quality and chemical range. The cheapest and most effective were R-11, R-12, which were used for a long time. In the last 15 years, they have fallen out of favor due to their ozone-destructive properties. All freons are based on two gases - methane CH 4 and ethane - CH 3 -CH 3. In refrigeration technology, methane is R-50, ethane is R-70. All other freons are obtained from methane and ethane by replacing the hydrogen atoms with chlorine and fluorine atoms. For example, R-22 is produced from methane by replacing one hydrogen atom with chlorine and two with fluorine. The chemical formula of this freon is СНF 2 Cl. The physical qualities of refrigerants depend on the content of three components - chlorine, fluorine and hydrogen. So, in proportion to the decrease in the number of hydrogen atoms, the heat of refrigerants decreases, and the stability increases. They can exist for a long time in the atmosphere without breaking apart and causing harm to the environment. As the quantity of chlorine atoms increases, so does the toxicity of refrigerants and their ozone-destructive capacity. The harm caused by freons to the ozone discharge is estimated by the dose of the ozone-depleting potential, which is equal to 0 for ozone-safe refrigerants, R-13-R-a-410 In this case, the ozone-destructive potential of freon R-12 is taken as a piece, until the closing time is most widely distributed throughout the cosmos. Freon R-22 was chosen as the temporary task R-12, the ozone-depleting potential of which is 0.05. In 1987, the Montreal Protocol was adopted, restricting the use of ozone-destructive creatures. In particular, according to this act, the perpetrators will be forced to abandon the use of R-22 freon, on which 90% of all producers work today. In most European countries, the sale of suppliers on this freon will be discontinued already in 2002-2004. And many unprecedented models are already supplied to Europe only on zone-safe refrigerants - R-407C and R-410A.
If the accumulation of "greenhouse gases" in the atmosphere is not interrupted, then in the second half of this century their concentration will approximately double, which will lead (according to computer models) to a warming of the climate in different regions by an average of 1.5 - 4.5 ° С : in cold regions by 10 o C, and in tropical regions - only 1 - 2 o C.
As a result of warming, irreparable damage to the fate of our planet may occur: the glaciers of Greenland, the Arctic Ocean, the South Pole, and finally, mountain glaciers will begin to melt; the level of the World Ocean will rise significantly (by 1.5-2 m and more). The average temperature of Antarctica will increase by 5 "C, which is enough to melt the entire ice cap. The level of the World Ocean will rise by 4.5-8 m everywhere and flood of many coastal areas (Shanghai, Cairo, Venice, Bangkok, large areas of fertile lowlands will be flooded) in India), and millions of people will be forced to migrate inland, to mountainous areas; the influence of the ocean on land will increase through increased storms, tides, low tides. Equalization of temperature at the equator and poles will disrupt the current circulation of the atmosphere, change the precipitation regime (scarce precipitation in the areas of agriculture), a decrease in the production of grain, meat and other foodstuffs. There is little hope for irrigation of these territories, since today the level of groundwater has dropped markedly, and by the middle of the century their reserves will practically be used up. already beginning to show: prolonged droughts in South Africa (5 years), Severn oh America (6 years old), warm winters, etc.
With general warming, winters will be colder than before and summers hotter. In addition, droughts, floods, hurricanes, tornadoes and other weather and climatic anomalies will become more frequent and more severe. Warming will be accompanied by a decrease in bioproductivity, the spread of pests and diseases.
