Global climate change Over the past century, the global average surface temperature has increased by 0.3 to 0.6 degrees Celsius, and sea levels have risen by 10 to 25 centimeters.

The current concentration of carbon dioxide in the earth's atmosphere has increased from 280 ppm before the industrial revolution (1750) to nearly 360 ppm.

An assessment report issued by the Intergovernmental Panel on Climate Change in 1996 showed that if the pattern of world energy consumption does not fundamentally change, the concentration of carbon dioxide in the atmosphere will reach 560 ppm by the middle of the 21st century, and the global average temperature may rise by 1.5 to 4 degrees Celsius.

Ozone Layer Destruction and Depletion Since the ozone layer hole appeared over Antarctica in 1985, the depletion of the ozone layer above the Earth has continued unabated.

By 1994, the ozone layer destruction area over Antarctica had reached 24 million square kilometers.

Now over the United States, Canada, Western Europe, the former Soviet Union, China, Japan and other countries, the ozone layer has begun to thin.

Before the control of ozone-depleting substances (ODS) was implemented (before 1996), the world's ODS emissions into the atmosphere had reached 20 million tons.

Since ODS is quite stable and can exist for 50-100 years, most of the emitted ODS still remains in the atmosphere.

As they rise toward the stratosphere, they react with the ozone layer there and break down ozone molecules.

Therefore, even if the world completely stops emitting ODS, it will take another 20 years before humans can see signs of ozone layer recovery.

Acid rain pollution The term "acid rain" is now used to refer to the transfer of acidic substances from the atmosphere to the ground in the form of wet deposition (rain, snow) or dry deposition (acidic particles).

Most of the acid rain is sulfuric acid and nitric acid, which mainly comes from the extensive use of fossil fuels by humans, which releases large amounts of sulfur dioxide and nitrogen oxides into the atmosphere.

Europe is a major acid rain area in the world, and the United States and eastern Canada are also major acid rain areas.

Acid rain in Asia is mainly concentrated in East Asia. South China is the most serious area of ??acid rain, becoming another major acid rain area in the world.

Due to the weak ability of soils in Europe to buffer acidic substances, acid rain has degraded 30% of European forest areas due to the impact of acid rain.

In Northern Europe, due to the high natural acidity of the soil, water and soil acidification are particularly serious. The acidification of some lakes has led to the extinction of fish.

Data from the U.S. National Surface Water Survey show that acid rain causes 75% of lakes and about half of rivers to become acidic.

The Canadian government estimates that 43% of Canada's land mass (mainly in the east) is highly sensitive to acid rain, and 14,000 lakes are acidic.

Water acidification will change aquatic ecology, while soil acidification will impoverish the soil and lead to the degradation of terrestrial ecosystems.

Land Desertification Desertification is the most serious environmental and socioeconomic problem in the world today.

In 1991, the United Nations Environment Program assessed the global desertification situation as follows: The global desertification area has reached nearly 3.6 billion hectares, accounting for approximately 1/4 of the global land area, and has affected 1/6 of the world's population (about 900 million people).

More than 100 countries and regions.

Moreover, desertification is expanding at such a rate that 6 million hectares of land worldwide become desert every year, of which 3.2 million hectares are pasture, 2.5 million hectares are dry land, 125,000 hectares are irrigated land, and 21 million hectares of land are degraded due to

And grains cannot grow.

Asia is the region with the highest concentration of people affected by desertification in the world. The countries most severely affected by desertification are China, Afghanistan, Mongolia, Pakistan and India.

Water crisis Many regions of the world face serious water crises.

According to international experience, 1,000 cubic meters of reusable freshwater resources per person per year is a basic indicator. Countries below this indicator may suffer from long-term water shortages that hinder development and harm health.

However, currently about 20 countries in the world have fallen below this indicator, mainly located in West Asia and Africa, with a total population of over 100 million.

On the other hand, water pollution caused by domestic wastewater, industrial wastewater, agricultural sewage, solid waste leakage, atmospheric pollutants, etc. has greatly reduced the amount of freshwater resources available worldwide.

The World Bank report estimates that more than 1 billion people around the world do not have access to safe drinking water due to water pollution and lack of water supply facilities.

Destruction of forest vegetation Due to the difficulty of speculation, there is no accurate value for the world's forest area.

However, it is estimated that the forest area on the earth is about 3-6 billion hectares, accounting for about 20%-40% of the land area. About half of them are tropical forests (including tropical rainforests and tropical monsoon forests), and the other half are composed of subarctic coniferous forests.

Mainly Ye Lin.

Judging from the measured dry weight of forest plants, tropical forests are twice as large as subarctic coniferous forests. Therefore, tropical forests account for a large part of the total terrestrial biomass.

However, during the process of industrialization, one-third of the temperate forests in Europe, North America and other places were cut down. Therefore, in the past thirty years, developed countries have carried out large-scale development of tropical forests around the world.

European countries entered Africa, the United States entered Central and South America, and Japan entered Southeast Asia. They cut down tropical forests in large quantities, and their imported tropical wood increased more than ten times.

The large-scale destruction of forests has caused a variety of environmental consequences, including: changes in rainfall distribution, increased carbon dioxide emissions, climate anomalies, soil erosion, frequent floods, and reduced biodiversity.