A short paper on global warming

This is a lot of words. You can cut off the early human activity ability according to the situation, that is, the ability to destroy nature is very weak, and at most it can only cause local microclimate changes, so people and nature can live in peace for millions of years. However, great changes have taken place since the industrial revolution. Industrialization means burning a lot of coal and oil, which means emitting a lot of waste gas into the earth's atmosphere. Among them, carbon dioxide gas causes atmospheric greenhouse effect, which makes global warming, polar ice melts and sea level rises; Sulfur dioxide and nitrogen oxides can form acid rain; Chlorofluorocarbons will destroy the upper ozone layer, leading to the thinning of the Antarctic ozone hole and the global ozone layer. In addition, the polluted gases emitted by industrialization also make the cities where human beings live together become air pollution islands with extremely high concentration ... While developing economy and improving the quality of life, human beings have also created a huge disaster. Many disasters seem to be natural disasters, but in fact they are often man-made disasters caused by human beings themselves. The destroyed earth's atmosphere is taking terrible revenge on mankind, and nature will never forgive human ignorance.

1In June 1992, heads of state and government of the world gathered in Rio de Janeiro, Brazil, and signed the United Nations Framework Convention on Climate Change. Why has the common scientific problem of climate change become so worrying?

It turns out that since the industrial revolution, the content of carbon dioxide (CO2) in the global atmosphere has increased by 25% in one hundred years due to the massive burning of fossil fuels and the destruction of forests. According to the current increase rate of CO2 concentration, the CO2 content in the atmosphere will double to 2 100. According to the assessment report issued by the United Nations, the global average temperature will rise by 1.0 ~ 3.5℃ compared with the present, which will lead to the melting of polar ice and the sea level rising by 1.5 ~ 95 cm, thus flooding a large area of economically developed coastal areas and possibly causing a series of other serious problems. Governments around the world began to pay attention to this situation and its harmful consequences, and discussed the issue of reducing carbon dioxide emissions.

What is the greenhouse effect?

The global average ground temperature is about 65438 05℃. If there is no atmospheric cover, according to the principle that the solar heat obtained by the earth is equal to the heat released by the earth into space, it can be calculated that the annual average temperature of the earth's ground is-18℃. This temperature difference of 33℃ is caused by the atmosphere protecting the earth like a quilt. This is the greenhouse effect.

Everything in the universe radiates electromagnetic waves. The higher the temperature of an object, the shorter the wavelength of radiation. The surface temperature of the sun is about 6000K, and its electromagnetic wave wavelength is very short, which is called solar short-wave radiation (including visible light from purple to red). The ground is heated by the short-wave radiation of the sun, and at the same time, electromagnetic waves are radiated all the time to cool down. The electromagnetic wave emitted by the earth is called ground long wave radiation because of its low temperature and long wavelength. Short-wave radiation and long-wave radiation have different experiences when passing through the earth's atmosphere: the atmosphere is almost transparent to solar short-wave radiation, but strongly absorbs ground long-wave radiation. While absorbing long-wave radiation from the ground, the atmosphere itself radiates long-wave radiation with longer wavelength (because the temperature of the atmosphere is lower than that of the ground). The part that goes down to the ground is called inverse radiation. The ground will heat up after receiving inverse radiation, which can also be said that the atmosphere plays a role in heat insulation for the ground. This is the principle of atmospheric greenhouse effect.

This heat insulation effect of the earth's atmosphere is similar to the glass on the warm roof where flowers are planted (greenhouse effect can also be called greenhouse effect or greenhouse effect), because glass also has the heat insulation effect of transmitting solar short-wave radiation and absorbing ground long-wave radiation.

The greenhouse effect originates from greenhouse gases.

We know that not every gas in the atmosphere will strongly absorb the long-wave radiation on the ground. Greenhouse gases in the earth's atmosphere are called greenhouse gases, which mainly include carbon dioxide, methane, ozone, nitrous oxide, freon and water vapor. They absorb almost all the long-wave radiation emitted from the ground, and only a narrow section absorbs very little, which is the so-called "blind zone". The earth mainly returns 70% of the heat obtained from the sun to space in the form of long-wave radiation through this blind area, thus keeping the ground temperature unchanged. The greenhouse effect we are talking about mainly refers to the situation that human activities increase the quantity and types of greenhouse gases, reduce the value of 70% of the heat that can return to space in this blind area, and increase the residual heat left behind, thus warming the earth.

However, although greenhouse gases such as carbon dioxide have strong ability to absorb long-wave radiation on the ground, they are very few in the atmosphere. If the atmospheric state with a pressure of one atmosphere and a temperature of 0℃ is called the standard state, then the whole atmosphere of the earth is compressed to this standard state with a thickness of 8000 meters. At present, the content of CO2 in the atmosphere is 355ppm, that is, 355ppm is one in a million). If converted into a standard state, it is 2.8 meters thick. In the 8000-meter-thick atmosphere, it accounts for a little bit of this 2.8-meter-thick atmosphere. The methane content is 1.7ppm and the thickness is1.4cm.. The ozone concentration is 400ppb(ppb is one thousandth of ppm), which is only 3 mm thick after conversion. Nitrous oxide is 3 10ppb, 2.5mm. There are many kinds of Freon, but the most abundant Freon 12 in the atmosphere is only 400ppt(ppt is one thousandth of ppb), which is only 3 microns in standard state. This shows that there are very few greenhouse gases in the atmosphere. Because of this, the greenhouse gases released by human beings can easily lead to global warming if they are not restricted.

As early as 1938, British meteorologist Kalinda pointed out that the concentration of CO2 at that time had increased by 6% compared with the beginning of the century, and there was a global warming trend from the end of last century to the middle of this century, which caused great repercussions in the world. Therefore, in 1958, Lin Kai of Scripps Institute of Oceanography in the United States set up observation stations at the altitude of 3400 meters in Maunalo and Yasan, Hawaii, and began to accurately observe the CO2 content in the atmosphere. Hawaii is located in the middle of the North Pacific Ocean, almost unaffected by land air pollution, and the observation results are quite reliable.

It can be seen from the variation curve of atmospheric CO2 concentration observed from Mauna Loa Mountain 1958 April to 199 1 year June that the atmospheric CO2 content is only about 3 15ppm in1year, which is at/Kloc-0. The seriousness of the problem also lies in that of the 5.5 billion tons of fossil fuels burned by human beings every year (about 4 tons of CO2 are produced per ton), only about one meter enters the atmosphere, and the remaining one meter is mainly absorbed by the ocean and land plants. Once the ocean is saturated with carbon dioxide, the content of carbon dioxide in the atmosphere will increase exponentially. From the figure, we can also find that the CO2 content varies seasonally, and the difference between winter and summer can reach 6ppm. This is mainly due to the influence of Xia Rong. The vegetation on the vast continent in the northern hemisphere is dry in winter. Because plants absorb a lot of CO2 in summer, the concentration of CO2 in the atmosphere is relatively low.

According to the measurement of CO2 concentration in the air of sealed bubbles in Antarctic and Greenland ice sheets, the CO2 content in the ancient atmosphere has been relatively stable, about 280ppm. Only from the middle of18th century, that is, before and after the industrial revolution, did it gradually rise. It took 240 years for humans to increase the concentration of carbon dioxide in the atmosphere from 280ppm to 355ppm.

Methane is an important greenhouse gas after carbon dioxide. Although its concentration in the atmosphere is much lower than that of carbon dioxide, its growth rate is much larger. According to the data of the second climate change assessment report published by the United Nations Intergovernmental Panel on Climate Change (IPCC) 1996, during the 240 years from 1750 to 1990 * *, CO2 increased by 30%, while methane increased by 145% in the same period. Methane, also known as biogas, is produced when organic matter decays under anoxic conditions, such as rice fields, compost and livestock manure. Nitrous oxide is also called nitrous oxide, because inhaling a certain concentration of this gas will cause facial muscle spasm and look like laughing. This is mainly due to the use of chemical fertilizers, burning fossil fuels and biological production. Although the ozone content in the stratosphere decreased, the ozone content in the troposphere increased. Freon gas is a compound of chlorine, fluorine and carbon, which does not exist in nature and is completely made by human beings. Because of its low melting point and boiling point, non-flammable, non-explosive, tasteless, harmless and excellent stability, it is widely used in the production of refrigerants, foaming agents and detergents. Although the highest concentrations of Freon 12 and Freon 1 1 in the earth's atmosphere are few, these annual growth rates are very high, reaching an annual growth rate of 5%. According to the Montreal Protocol of 1987, its concentration in the atmosphere will gradually decrease at the beginning of the 20th century.

It should be noted that although the concentration of greenhouse gases except CO2 in the atmosphere is far less than that of CO2, and some are even several orders of magnitude smaller, its greenhouse effect is much stronger than that of CO2. According to the second IPCC report, their greenhouse effect is only one order of magnitude lower than that of CO2. This is noteworthy.

Consequences of the greenhouse effect

As mentioned earlier, before the industrial revolution, the content of carbon dioxide in the atmosphere was 280ppm. According to the current growth rate, it will increase to 550ppm by 2 100, which is almost doubled. Many meteorologists all over the world are trying to study how much the global average temperature will rise by 2 100 after the carbon dioxide content doubles.

At present, the concrete method is to design a numerical model to calculate according to the laws of atmospheric movement and physical state change. However, because people's understanding of the changing law of atmospheric motion is not perfect and the simplified design methods adopted are different, the calculation results of each model are often very different. Therefore, in 1980s, the American Academy of Sciences organized an evaluation committee to study and comprehensively evaluate the results of these models, and finally came to the conclusion that the global average temperature would increase by 1.5 ~ 4.5℃ after CO2 doubling. This is the figure used in the first report of the United Nations Intergovernmental Panel on Climate Change, the most authoritative organization on this issue.

In recent years, the simulation ability of climate model has been greatly improved, mainly considering the role of aerosols (tiny particles suspended in the air) in the atmosphere. Because when burning fossil fuels, it will release CO2, and at the same time, it will release huge aerosols such as sulfides. This kind of aerosol particles will block some sunlight from reaching the ground, reduce the ground temperature and play a role in cooling down. According to IPCC's estimation, its value can reach -0.5 W/m2, which is equivalent to 1/3(+ 1.56 W/m2) of CO2 warming effect, and slightly larger than methane warming effect (+0.47 W/m2). Mainly based on this improvement, in the second report published by IPCC 1996, the global average temperature rise after CO2 doubling of 2 100 was revised from 1.5 ~ 4.5℃ to 1.0 ~ 3.5℃. The assessment report also points out that the warming value of 2 100 will only reach about 50 ~ 90% due to the huge thermal inertia of the ocean.

The model calculation results also show that the global average warming 1.0 ~ 3.5℃ is not evenly distributed in the world. There is no or almost no temperature rise in equatorial and tropical areas, and the temperature rise is mainly concentrated in high latitudes, and the number can reach 6 ~ 8℃ or even more. This will cause another serious consequence, that is, the ice sheets at the poles and Greenland will melt, causing sea levels to rise. The permafrost zone of the high-latitude continent in the northern hemisphere will also melt or thin, resulting in a large area of swamp. In addition, the volume expansion of seawater after ocean warming will also lead to sea level rise. In the first assessment report of IPCC, it was estimated that the sea level would rise by 20 ~ 150 cm (corresponding temperature rise 1.5 ~ 4.5℃), and it was revised to 15 ~ 95 cm (corresponding temperature rise/.0 ~ 3.5℃) in the second assessment report. That is, it is about 25% lower than the first evaluation result. The IPCC's second assessment report also pointed out that the global sea level has risen by10 ~ 25cm since the end of 19, because the global average temperature has risen by 0.3 ~ 0.6℃.

Global sea level rise will directly inundate coastal lowland areas with dense population and developed industry and agriculture, with very serious consequences. 1995165438+1At the second Conference of the Parties to the United Nations Framework Convention on Climate Change held in Berlin in October, 44 small island countries formed the Alliance of Small Island States and called for the right to exist.

In addition, it is pointed out that the increase of CO2 will not only lead to global warming, but also lead to the adjustment of global atmospheric circulation and the expansion of climatic zones to the polar regions. The precipitation in mid-latitude areas, including northern China, will decrease. With the increase of evaporation caused by warming, the climate will tend to be dry. The adjustment of atmospheric circulation, in addition to mid-latitude drought, may also cause climate anomalies and some disasters in other parts of the world. For example, the intensity of typhoons at low latitudes will increase and the source of typhoons will expand northward. Rising temperature will also cause or aggravate the epidemic of some infectious diseases. Take tuberculosis as an example. In the past five years, the incidence of phlegm disease in the world has doubled or quadrupled. At present, about 500 million people in the world get phlegm disease every year, and more than 2 million of them die.

However, the greenhouse effect is not all bad. The coldest high latitudes are the most warm, and agricultural areas will be greatly promoted to the polar regions. The increase of CO2 is also beneficial to the photosynthesis of plants and directly increases the yield of organic matter. Some experts pointed out that in the history of China and the world, the warm period is mostly a prosperous period with more precipitation and smaller arid area.

There are also different views on the issue of atmospheric greenhouse effect. Some scientists believe that the current numerical model is immature and the calculation results are too exaggerated; A rise of 0.3 ~ 0.6℃ in a hundred years is a normal climate change, which cannot be proved to be caused by the atmospheric greenhouse effect. This is a minority opinion.

However, it is an indisputable fact that the concentration of CO2 in the atmosphere and the global temperature are increasing rapidly, and the increase of greenhouse gases will lead to global warming. If we wait until the problem is clearly perceived, it is often difficult to reverse it. Therefore, we must attach great importance to it in order to take countermeasures to protect the atmospheric environment on which human beings depend.

Global countermeasures

The countermeasures of global warming caused by atmospheric greenhouse effect mainly include the following three aspects.

The first aspect is to reduce CO2 in the current atmosphere. The most practical way is to plant trees extensively, strengthen greening and stop deforestation; The photosynthesis of sunlight absorbs and fixes a large amount of CO2 in the atmosphere. There are some ways to absorb CO2 through chemical reaction, but the technology is not mature and it is difficult to implement it on a large scale economically.

The second aspect is adaptation. This is a problem that must be considered anyway. For example, in addition to the construction of coastal protection dams and other engineering measures to prevent seawater intrusion, the types and varieties of local crops are gradually changed in a planned way to adapt to the changing climate. Because of the cold summer in northern Japan, rice was not planted in the past, and even if it was planted, the yield was very low. Thanks to the cultivation of cold-resistant and stress-resistant varieties, rice can not only grow in the northernmost Hokkaido, but also have a high yield. This is a good example. Climate change is a relatively slow process. As long as we can predict the trend of climate change as soon as possible, we can find adaptive countermeasures and implement them smoothly.

The third aspect is to reduce carbon dioxide emissions. This is the gist of the Framework Convention on Climate Change signed by the world leaders at the World Conference on Environment and Development in Rio de Janeiro, Brazil 1992. The Convention requires developed countries to reduce their carbon dioxide emissions to the level of 65,438+0,990 in 2000, and provide funds and technology transfer to developing countries to help them reduce their carbon dioxide emissions. The rapid increase of CO2 concentration in the global atmosphere in the last century was mainly caused by emissions from developed countries. Developing countries should first get rid of poverty and develop, and developed countries have the obligation to do so.

As the Convention is a framework, it is not binding. However, the reduction of carbon dioxide emissions directly affects the economic interests of developing countries, so some developed countries not only do not reduce emissions, but also increase emissions. Now it seems impossible to reduce carbon dioxide emissions to the level of 1990 in 2000. At the Third Conference of the Parties to the United Nations Framework Convention on Climate Change (Kyoto Conference, Japan), which ended on June 5438+0997+February 1 1, developing countries and developed countries launched a sharp and intense struggle. Finally, the developed countries gave in and the dystocia Kyoto Protocol was finally passed. The Protocol stipulates that all developed countries should reduce the emissions of six greenhouse gases (carbon dioxide, nitrous oxide, methane and three chlorofluorocarbons) by 5.2% at the level of 20 10 compared with 1990. This is a binding international emission reduction agreement, although it is still far from the target of reducing emissions by 20 10/5% and 20% in 2020 required by developing countries.