How to understand the key and focal issues of global climate change
BIOX.CN 2005-4-149: 41:00 Source: Life Jingwei
Climate change is a typical global environmental problem. In 1970s, scientists proposed that climate warming was a global environmental problem. In the 1980s, with the deepening understanding of the relationship between human activities and global climate, and the emergence of the hottest weather in hundreds of years, this issue began to become an international political and diplomatic issue. 1938 to 1992 At the United Nations Conference on Environment and Development held in Rio de Janeiro, the Framework Convention on Climate Change was adopted and opened for signature. Climate change is directly related to the mode of economic development and the structure and quantity of energy utilization, and is becoming a major international issue that has a far-reaching impact on global development in the 2/kloc-0 century.
I climate change and its trends
In geological history, the earth's climate has undergone major changes. Ten thousand years ago, at the end of the last ice age, the earth's climate was relatively stable, and it was in a state that human beings were used to at present. The temperature of the earth is determined by the rate at which solar radiation strikes the surface of the earth and the rate at which the earth emits infrared radiation into space after absorbing heat. In the long run, the energy absorbed by the earth from the sun must be in balance with the radiant energy emitted by the earth and the atmosphere. Trace gases such as water vapor and carbon dioxide in the atmosphere, such as methane, ozone and freon, can make the short-wave radiation of the sun pass through almost without attenuation, but they can absorb the long-wave radiation of the earth. Therefore, these gases have similar effects to greenhouse gases and are called. Quot greenhouse gases ". Greenhouse gases absorb long-wave radiation and reflect it back to the earth, thus reducing the net energy emission to outer space, and the atmosphere and the earth's surface will become hot, which is the "greenhouse effect". Nearly 30 kinds of gases that can produce greenhouse effect have been found in the atmosphere, among which carbon dioxide plays an important role, and methane, freon and nitrous oxide also play a very important role (see Table 2). From the comparison of long-term climate data, there is a significant correlation between temperature and carbon dioxide (see figure 1). At present, the issue of climate change discussed by the international community mainly refers to climate warming caused by the increase of greenhouse gases.
Table 2 Main greenhouse gases and their characteristics
Annual increase of concentration in gas atmosphere (ppm(%) Life span (year) Greenhouse effect (CO2 = 1) Main source of existing contribution rate (%)
Coal, oil, natural gas and deforestation
CFC 0.00085 2.250-1023400-1500024 Foaming agent, aerosol, refrigerant and cleaning agent.
Methane1.7140.812-17115 wetlands, paddy fields, fossils, fuels and livestock.
Fossil fuels, fertilizers and deforestation
Quoted from Global Environment Facility: Attaching Importance to Global Environment, 1998.
Some scientific observations since the beginning of this century show that the concentration of various greenhouse gases in the atmosphere is increasing. Before 1750, the carbon dioxide content in the atmosphere was basically maintained at 280ppm. After the industrial revolution, with the continuous growth of human activities, especially the consumption of fossil fuels (coal, oil, etc.). ) and the massive destruction of forest vegetation, greenhouse gases such as carbon dioxide emitted by human beings continue to increase, and the content of carbon dioxide in the atmosphere gradually increases. The annual increase is about 1.8ppm (about 0.4%), and it has now risen to nearly 360ppm. According to the measurement results, the increase of carbon dioxide in the atmosphere is about half of man-made emissions. According to the assessment of the Intergovernmental Panel on Climate Change (IPCC), the global average surface temperature has increased by 0.3℃ to 0.6℃ in the past century. The global sea level has risen by 10 to 25 cm. Many scholars predict that by the middle of the next century, if the world energy consumption pattern does not change fundamentally, the concentration of carbon dioxide in the atmosphere will reach 560ppm, and the average temperature of the earth will rise sharply. The Intergovernmental Panel on Climate Change published a new assessment report in 65,438+0996. It is once again affirmed that the increase of greenhouse gases will lead to global climate change. According to various computer models, if the carbon dioxide concentration increases from 280ppm before the industrial revolution to 560ppm, the global average temperature may rise by 1.5℃ to 4℃.
Figure 1 Changes of atmospheric carbon dioxide concentration and temperature
Second, the factors affecting climate change.
Nature itself emits all kinds of greenhouse gases, but it also absorbs or decomposes them. In the long-term evolution of the earth, the changes of greenhouse gases in the atmosphere are very slow and circular. Carbon cycle is a very important natural cycle process of chemical elements, and a large amount of carbon exchange occurs between the atmosphere and terrestrial vegetation, between the atmosphere and marine surface plants and plankton every year. From the perspective of natural forests, the absorption and emission of carbon dioxide are basically balanced. Human activities have greatly changed the land use pattern, especially after the industrial revolution, a large number of forest vegetation has been cut down rapidly, the use of fossil fuels has also increased at an alarming rate, and man-made greenhouse gas emissions have also increased accordingly. Globally, energy production increased by 50% from 1975 to 1995. Carbon dioxide emissions increase accordingly (see Figure 2-2). So far, most of the fossil fuels produced in the world have been consumed by developed countries, and their accumulated carbon dioxide emissions have reached an alarming level. For example, by the early 1990s, the cumulative emissions of the United States reached nearly17 billion tons, the European Union reached nearly12 billion tons, and the former Soviet Union reached nearly 1 10. Developed countries are still the main emitters of greenhouse gases such as carbon dioxide, and the United States is the largest emitter in the world. The total emissions of some developing countries, including China, are also growing rapidly. After the disintegration of the former Soviet Union, China's emissions ranked second in the world, which became a concern of developed countries. However, in terms of per capita and cumulative emissions, developing countries are still far below developed countries (see table 3).
Figure 2 1950- 1995 Global Carbon Emissions from Fossil Fuel Combustion.
Table 3 Carbon dioxide emissions (million tons) Per capita emissions (tons) of 15 countries with the largest carbon dioxide emissions
Usa 488 1 19.4438+03
2 China 2668 2.27
3 Russia 210314.11
4 Japan 1093 8.79
Germany 878 10.96
6 India
Ukraine 61111.72
8 UK 566 9.78
Canada 4 10 14.99
10 Italy
France 362 6.34
Poland 3428+0
Mexico 333.77
Kazakhstan 298 17.48
South Africa 290 7.29
All world resources: world resources) 1996-97-97.
The future trend of man-made greenhouse gas emissions mainly depends on the changing trend of population growth, economic growth, technological progress, energy efficiency improvement, energy conservation, relative prices of various energy sources and many other factors. Several internationally renowned energy agencies-International Energy Agency, US Department of Energy and World Energy Council-put forward various possible trends of man-made carbon dioxide emissions according to different scenarios of economic growth and energy demand. Judging from these scenarios and trends, the economic growth is moderate, and there is no strong restriction on the use of fossil fuels. By 20 10, fossil fuels will still account for about 3/4 of the global commercial energy, and their consumption may exceed 35% of the current level, and the carbon dioxide emissions related to energy use may increase by 30-40%. Energy consumption and carbon dioxide emissions in developing countries will increase relatively rapidly. By 20 10, it is likely to increase from less than 1/3 of global carbon dioxide emissions in the early 1990s to nearly 1/2, with China and India accounting for about half of the emissions of developing countries. Even so, the per capita and cumulative emissions of developing countries are still lower than those of developed countries. By the middle of the next century, developed countries will still be the main responsible persons for the cumulative emission of carbon dioxide in the atmosphere. Of course, if all countries in the world adopt economic and energy development strategies that are more suitable for environmental requirements,
Table 4 Energy consumption and carbon dioxide emissions estimated by World Energy Council (1990-2020)
High-growth (1990-2020) Revised Reference Scheme (1990-2020) Reference Scheme (1990-2020) Strengthening Ecological Protection (1990-2020)
Annual economic growth rate (%)
OECD countries/former Soviet Union and Central European countries
developing country
Proportion of world energy demand growth (%)98-84 54 30
Ratio of annual carbon dioxide emission exceeding 1990 (%) 93 73 42 5
World resources institute, etc. : world resources) 1996-97-97.
Three. Impact and harm of climate change
In recent years, the hottest weather in the history of hundreds of years has appeared in all countries in the world, and El Niñ o phenomenon has also occurred frequently, causing huge economic losses to all countries. Developing countries have weak resilience and suffer the most, and developed countries have not been spared. 195 Chicago heat wave killed more than 500 people,193 a hurricane in the United States caused a loss of 40 billion dollars. In the 1980s, the amount of climate-related claims in the insurance industry was $654.38+04 billion, and it was almost $50 billion during the period from 654.38+0990 to 654.38+0995. These conditions show that the adaptability of human beings to meteorological disasters caused by climate change, especially climate warming, is quite weak, and actions need to be taken to prevent it. According to some current development trends, scientists predict the possible impacts and hazards as follows:
1. Sea level rise
About13 of the world's population lives within 60 kilometers of the coastline, with developed economy and dense cities. The expansion of marine water bodies and the melting of polar ice and snow caused by global warming may raise the sea level by 50 cm in 2 100, endangering the global coastal areas, especially those with dense population and developed economy in estuaries and coastal lowlands. These areas may be flooded or invaded by seawater, and beaches and coasts will be eroded.