In an article entitled "Global Air Quality and Pollution" in Science magazine on February 5, 65438, Japanese scientist Hajime Akimoto studied the serious impact of environmental pollution and modern transportation on the atmosphere, agriculture and ecological environment. For example, aerosols and nitrogen oxides are some known pollution factors. And the pollution in Asia has surpassed that in North America and Europe. The author points out that it is obvious that improving air quality requires the efforts of all countries in the world.
Published in the same issue of Science, entitled "Modern Global Climate Change" is a report on the research results of scientists from the National Oceanic and Atmospheric Administration of the United States. The article points out that the climate change in contemporary society is mainly caused by human behavior. Specifically, the exploitation of oil and mining, the utilization of energy and the unreasonable use of land will change the composition of the atmosphere.
According to the report, although people have made progress in the study of climate change, there are still many unknown factors, such as how fast climate change will be. These unknown factors make it impossible for scientists to predict the serious consequences of climate change on human beings.
Air pollution and global climate change are still increasing, which means that we are making it more and more difficult for human beings to survive in the future. Therefore, how to face and solve this problem has become a top priority.
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I. Introduction
Since human beings have existed, in order to survive and seek a better living environment, human beings have been striving for living space from nature, which has also become one of the factors affecting environmental changes. The longer people live, the more people live, and the greater the impact. In the case of sparse population and underdeveloped technology, human beings burn forests in order to expand cultivated land, which has a regional and slow impact on nature. With the rapid increase of population and the rapid development of science and technology, the influence of human beings is accelerating, and it will evolve into forest shrinkage, soil erosion, water pollution, air pollution, biodiversity reduction, desertification and even global climate change.
Since the industrial revolution, human beings have produced a lot of greenhouse gases, such as carbon dioxide, nitrous oxide, methane and chlorofluorocarbons. The influence of human beings on nature is no longer limited to the surface, but extends to the atmosphere. Through the movement of the atmosphere, the influence is gradually distributed to the whole world, which greatly improves the possibility of global warming. Therefore, scientists are shocked that the climate is not only unpredictable, but also more likely to undergo drastic changes due to the excessive development of human beings. Since 1980, the global average temperature has risen rapidly, and abnormal weather and climate phenomena have occurred frequently, making climate change suddenly a topic attracting worldwide attention.
From a scientific point of view, this paper discusses the possible climate change caused by the increase of greenhouse gases, the scientific problems faced by predicting climate change, and the attitude we should adopt.
Second, the greenhouse effect.
The greenhouse effect is a natural phenomenon, which has existed on the earth since Pangu opened the sky. If the earth has no atmosphere, the average temperature of the earth's surface under radiation balance is about-18℃, which is much lower than the current global average temperature of 15℃. The existence of the atmosphere makes the surface temperature rise by about 33℃, and the greenhouse effect is the main reason for this temperature difference. Many gases in the earth's atmosphere hardly absorb visible light, but only absorb radiation emitted by the earth. These gases allow about 50% of solar radiation to pass through the atmosphere and be absorbed by the surface, but they intercept almost all the energy radiated by the surface and atmosphere, reduce the loss of energy, and radiate again, which makes the surface and troposphere temperature rise. The radiation from the atmosphere not only warms the surface temperature, but also continues to radiate at night, so that the surface will not become too cold due to the lack of solar radiation. The effects of these gases are similar to the warming effect of agricultural greenhouses, so they are called greenhouse gases, and their effects are called greenhouse effect. The greenhouse effect does not only happen on the earth. The main atmospheric component of Venus and Mars is carbon dioxide. The greenhouse effect of Venus atmosphere is as high as 523℃, while the atmosphere of Mars is too thin, and the greenhouse effect is only 10℃. ..
The greenhouse effect of the earth's atmosphere creates an environment suitable for living things. However, if the greenhouse gas content in the atmosphere is too high, it will intercept too much earth radiation and make the surface temperature rise gradually. Since industrial revolution in europe, fossil fuels (such as coal and oil) have been widely used in human industrial activities, and a large amount of carbon dioxide has been released into the atmosphere. In the thousand years before the industrial revolution, the carbon dioxide content in the atmosphere remained at about 280ppmv (that is, one million units of gas contained 280 units of carbon dioxide, as shown in figure 1). After the industrial revolution, the content of carbon dioxide increased rapidly, and it increased even faster after the 1950s, and the concentration reached 358ppmv at 1995.
From the end of18th century to the 1990s, the carbon dioxide content increased by 30%. These increases mainly come from burning fossil fuels, cement manufacturing and land use. Carbon in coal and oil is oxidized into carbon dioxide during combustion; When limestone is made into cement, it also produces carbon dioxide; The development and utilization of land not only reduces the amount of carbon dioxide absorbed by plants, but also accelerates the decomposition of broken branches and leaves to produce carbon dioxide. Most of the coal we use now is peat (more than 300 million years ago), a fossil gradually formed by trees buried in the stratum for some reason. More than 300 million years ago, plants absorbed the energy left by solar radiation, but modern humans used it up in one or two hundred years.
In addition, there are carbon dioxide, methane, nitrous oxide, chlorofluorocarbons (CFCs) and so on. Due to the increase of population and increasingly active economic activities, all these have increased rapidly (Figure 2). For example, from before the industrial revolution to 1994, the methane content increased from 700ppbv (one part per billion by volume) to1721ppbv; Nitrous oxide increased from 275ppbv to 3 1 1ppbv. CFC is a man-made chemical substance, which only appeared in large quantities in 1950' s and then increased rapidly. Recently, due to the prohibition of the use of chlorofluorocarbons by Montreal Convention, its content did not increase in11990s.
Compared with carbon dioxide, methane, nitrous oxide and chlorofluorocarbons have greater greenhouse effects. For example, the greenhouse effect of methane molecules is 265,438+0 times that of carbon dioxide molecules, 206 times that of nitrous oxide, and thousands to more than 10,000 times that of chlorofluorocarbons. But because the content of carbon dioxide is much higher than other gases, the greenhouse effect of carbon dioxide is still the biggest. Fig. 3 shows the proportion of radiation increase in the atmosphere caused by various man-made greenhouse gases between 1980 and 1990. Carbon dioxide accounts for 55%, methane accounts for 15%, nitrous oxide accounts for 6%, and CFC accounts for 24%.
Another feature of the above greenhouse gases is that they stay in the atmosphere for a long time (that is, their lifetime). The life span of carbon dioxide is 50 ~ 200 years, methane is 12 ~ 17 years, nitrous oxide is 120 years, and CFC- 12 is 102 years. Once these gases enter the atmosphere, they can hardly be recovered, and only through natural processes can they gradually disappear. Because of the long life of greenhouse gases in the atmosphere, its impact is long-term and global. Carbon dioxide molecules emitted into the atmosphere from any corner of the earth will have the opportunity to travel around the world and influence the climate in its life span of 100 years. Even if human beings immediately stop all man-made greenhouse gas emissions, the accumulated greenhouse gas will continue to exert its greenhouse effect after the industrial revolution and affect the climate of the earth.
Three. Possible effects of greenhouse gases on future climate
When there are many warm periods in the history of the earth's climate, the content of greenhouse gases is also high. Without human intervention, nature has its own rhythm, and life on earth can't escape if it wants to. However, the problem facing modern human beings is whether the excessive emission of man-made greenhouse gases has destroyed or will soon destroy the rhythm of nature, leaving a ruined future for future generations.
If the greenhouse gas content in the atmosphere continues to rise (inevitable fact! ), Intergovernmental Panel on Climate Change; IPCC scientists estimate that by 2 100, the global average temperature will be 0.9℃ to 3.5℃ higher than that of 1990 (Figure 4). The greenhouse effect of carbon dioxide accounts for about 70%, and other greenhouse gases account for about 30%. Because of the large heat capacity of the ocean, it is not easy to raise the temperature, and the temperature on land will rise much higher than that on the ocean, especially in the high latitudes of the northern hemisphere, because there are more land in the northern hemisphere. However, the temperature in the North Atlantic is not rising, but falling. It is estimated that the increase of carbon dioxide concentration will increase the global average precipitation, especially in high latitudes in winter. At low latitudes, precipitation generally increases in areas with relatively large precipitation, especially in South Asia and Southeast Asia. As the global average temperature rises, the seawater temperature also rises. The volume expansion and melting of polar ice and snow make the global average sea level rise gradually, which will be 38 cm to 56 cm higher than that of 1990 in 2 100 (Figure 5). The sea level rise is mainly caused by the expansion of seawater volume, and the melting of glaciers in Greenland and Antarctica has little effect.
In terms of climate variability and extreme climate, IPCC scientists have come to the following conclusions:
Small changes in climate mean or variability may lead to great changes in extreme climate frequency.
Overall warming will increase the frequency of high temperature, but decrease the frequency of low temperature.
The frequency of rainstorm may increase. In areas where the average precipitation decreases, the possibility of drought increases. The water cycle may be strengthened, which means that droughts and floods in some areas are aggravated and some areas are slowed down.
Whether the mid-latitude storm is strengthened or weakened is still inconclusive.
Current knowledge cannot determine the possible changes of tropical cyclones and typhoons.
Climate warming brings tropical oceans closer to El Ni? o phenomenon, and climate patterns similar to El Ni? o phenomenon may be more frequent.
Fourthly, the controversy of climate change prediction.
IPCC uses climate models in supercomputers to estimate the future climate. The knowledge and tools used are the most advanced technologies. However, the current understanding of nature is still not enough to accurately predict the climate in 2 1 century. Only a few controversial issues are discussed here.
The smaller the spatial scale, the more severe the weather phenomenon and the lower the accuracy:
Generally speaking, the spatial resolution of climate models is very poor. In many models, Taiwan Province Province does not even exist. So the regional climate predicted by different models is sometimes very different. Therefore, it is almost impossible to predict the future climate of Taiwan Province Province with the current climate model.
Humans still don't know many physical mechanisms that affect climate:
The most obvious example is suspended particles. When human beings burn fossil fuels, they will also produce sulfate suspended particles, which will increase atmospheric turbidity and cause air pollution and acid rain. Scientists warned in the 1950-60 s that air pollution caused by human beings would increase atmospheric turbidity and make the climate gradually cool. Therefore, if the cooling effect of suspended particles is considered, the degree of warming in many areas will decrease, and the rainfall will even change from decrease to increase (or from increase to decrease). IPCC scientists estimate that since the industrial revolution, the warming effect caused by man-made greenhouse gases is equivalent to about 2.5 watts per square meter. At the same time, the cooling effect of suspended particles is quite uncertain, ranging from 0 to 3 watts per square meter.
Climate models are still imperfect:
There are still many imperfections in the current climate model, which is similar to the model used to predict the weather. Many scientists argue that when we still can't accurately predict the weather after 10 with these models, how can we predict the climate in 2 1 century?
Natural change and man-made change;
How much of the climate change in the past 100 years is a natural change of climate? How much is caused by man-made pollution? There are still many discussions on this issue in the scientific community, and there is no conclusion yet. The most obvious example is IPCC's conclusion that the 20th century was warmer than other centuries: "The global average temperature is at least as warm as any century since 1400" (at least as warm as any century since 1400). Moreover, the phenomenon of global warming may be related to the Little Ice Age that lasted for hundreds of years and ended at the end of 19. The occurrence of the Little Ice Age has nothing to do with human activities. Whether the Little Ice Age ended because of the greenhouse effect caused by man-made greenhouse gases is another unanswered question. How to distinguish natural change from man-made change is a big challenge for scientists at present.
Verb (abbreviation for verb) Our attitude
The climatologist Henderson-Sellers made a questionnaire survey on the prevention and control of global warming, asking how confident it is to take preventive measures. As a result, the public demand is only 50%. Even so, scientists can't really guarantee. However, can we ignore the problem of global warming? The answer is no. There are three reasons:
The possibility of global warming:
Although we still don't know exactly how the accumulation of greenhouse gases will change the climate of the earth, we know that man-made pollution may indeed lead to climate change, and its impact can not be ignored. There are three reasons: (1) the greenhouse gas content in the atmosphere has increased due to human activities; (2) Greenhouse gases have the property of warming the earth's atmosphere; And (3) the life span of greenhouse gases ranges from ten years to hundreds of years, which can affect the earth's climate for hundreds of years.
Feedback function of climate system;
There are many positive feedback effects and negative feedback effects in the operation of climate system. Either the former or the latter may completely change the climate of the earth. Broecker, a famous scholar, recently published a paper warning that global warming may change the ocean circulation in the Atlantic Ocean, which will reduce the heat transferred to high latitudes and make Europe and even the world enter a cold climate. At first glance, the mechanism he proposed seems to alleviate global warming, but it is not the case. Because the cooling effect of this mechanism is far greater than the warming effect of global warming, but it causes more severe climate change. W. S. Broecker compares this mechanism to the Achilles heel of the climate system, that is, a small change may lead to a big change in the climate system, even a short one (the time scale is several years).
The risk of climate change is too great:
A typhoon, whether in a backward country like the Bay of Bengal or a rich country like the United States, may cause huge loss of life and property. Although there is still considerable uncertainty about how the climate will change, if global warming leads to more serious weather and climate changes, its impact will be unimaginable. In other words, the risks we face are unprecedented. What's more, the data show that when the greenhouse gas content in the ancient atmosphere was high, the climate was warmer; When the content is low, the climate is cold (Figure 6). What happened repeatedly in the past has a high probability of happening in the future.
Based on the above reasons, we should have the following cognition and understanding:
The concept of risk:
First of all, we should recognize the uncertainty of climate change prediction, and we should not completely deny the possibility of climate change just because the scientific community can't come up with a 100% credible result. People face many risks, big and small, in their life. Therefore, modern people spend a lot of time, money and energy to maintain their health, buy life insurance and health insurance to prevent problems before they happen. Before taking these measures to protect our own interests, we never need to be sure that unfortunate things will happen. Similarly, the future of mankind faces greater risks. What's more, in the past one or two hundred years, human beings have buried more unpredictable crises for their future. Instead of doing nothing in the face of an endless future, we should try our best to maintain the health of the earth. The interaction between man and nature should be mutual integration, not adaptation and healing afterwards. Even if the probability of global warming is not high, it is not serious, but any investment (tangible or intangible) in maintaining the global environment is worthwhile, because at least we have maintained a healthy living environment. Besides, if it really happens, the price paid by mankind will be extremely heavy. In the final analysis, maintaining the health of the earth is to continue the survival of mankind.
Abandon the concept of "muddling along";
The Kyoto Framework Convention on Climate Change has raised the issue of global warming to the highest point. Because of the great uncertainty, the climate change caused by man-made greenhouse gases has a great impact on the economies of all countries, and it is difficult for all countries to acquire knowledge in the international political arena. Taiwan Province Province's handling of this problem is still in the stage of muddling through. The government always talks about "solutions" rather than "solutions", hoping to apply a wider range of carbon dioxide emission standards. Some even suggested that relevant issues should be resolved through diplomatic negotiations. However, everyone knows how many diplomatic chips Taiwan Province Province has. Advocates of nuclear energy policy also take this opportunity to suggest the development of nuclear power generation. The cruel fact is that Taiwan Province Province will continue to invest in steel mills with high energy consumption. No matter how many nuclear power plants are built, it will not help. What's more, nuclear power plants have other environmental problems. The ostrich mentality not only can't solve the problem, but will only make the situation worse.
Create an "environment-friendly country";
At the end of the 20th century, the rapid economic development brought great pressure to the earth where human beings lived. Taiwan Province Province is densely populated, and the environmental pollution and ecological damage are more serious. The strategy we should adopt is to rethink Taiwan Province's economic policy and science and technology policy, so as to integrate economic development, science and technology development and environmental protection, rather than restrict each other. The strategy that Taiwan Province Province should adopt is not to deal with it, but to plan a sustainable development strategy that can give consideration to "moderate economic development" and "environmental protection", so that Taiwan Province Province can become an "environment-friendly country", fulfill its obligations as a member of the global village, and completely solve the regional and global environmental pollution problems.
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This paper discusses the greenhouse effect and future climate change, deliberately presenting scientific uncertainty naked. The author thinks this information is very important, because climate prediction will seriously affect the downstream impact assessment and coping strategies research, and even the direction of policy formulation. The concept of uncertainty or probability should also be included in the study of impact assessment and coping strategies. What we should do is to evaluate the possible impact of climate change according to different assumptions, rather than giving a categorical answer.
We don't want the government, enterprises, and even the public to know the uncertainty of climate change prediction, and ignore the huge impact that man-made environmental changes may bring. On the contrary, due to its uncertainty and possible disasters, we should devote more energy to research, education and prevention related to environmental protection, and try to combine green technology with economy to make environmental protection and moderate and necessary economic development form a win-win situation.