The weather in Beijing is 8.2.

1, increasing the temperature during the day and decreasing the temperature at night, that is, increasing the temperature difference between day and night, which is conducive to accumulating sugar products of photosynthesis and increasing the yield. The reason is that the temperature is moderately increased during the day, the activity of enzymes is enhanced and photosynthesis is accelerated. Because there is no light at night, you can only breathe. If the temperature decreases, the activity of enzyme decreases, and the respiration will slow down, thus reducing the consumption of organic matter.

Introduction to the first greenhouse effect

The greenhouse effect refers to the heat preservation effect caused by the lack of heat exchange between the enclosed space transmitting sunlight and the outside world, that is, the short-wave radiation of the sun can penetrate the atmosphere and enter the ground, and the long and short radiation released after the ground warms is absorbed by substances such as carbon dioxide in the atmosphere, thus producing the effect of atmospheric warming. Carbon dioxide in the atmosphere is like a thick layer of glass, which makes the earth a big greenhouse. It is estimated that if there is no atmosphere, the average surface temperature will drop to -23℃, while the actual average surface temperature is 15℃, which means that the greenhouse effect will increase the surface temperature by 38℃.

In addition to carbon dioxide, methane, ozone, chlorofluorocarbons, water vapor and other gases that play an important role in the greenhouse effect. With the rapid increase of population and the rapid development of industry, the carbon dioxide discharged into the atmosphere has also increased accordingly; Because of a large number of deforestation, the carbon dioxide that forests should absorb in the atmosphere has not been absorbed, and the greenhouse effect has been continuously enhanced because of the gradual increase of carbon dioxide. According to analysis, in the past two hundred years, the concentration of carbon dioxide has increased by 25%, and the average temperature of the earth has increased by 0.5℃. It is predicted that by the middle of the next century, the average temperature on the earth's surface will rise by 1.5-4.5℃, especially in the middle and high latitudes.

The air contains carbon dioxide, which has remained basically unchanged for a long time in the past. This is because the carbon dioxide in the atmosphere is always in a dynamic equilibrium state of "increasing while consuming". 80% of carbon dioxide in the atmosphere comes from the breathing of people, animals and plants, and 20% comes from the burning of fuel. 75% of carbon dioxide scattered in the atmosphere is absorbed by groundwater and atmospheric precipitation such as oceans, lakes and rivers and dissolved in water. Another 5% of carbon dioxide is converted into organic matter through plant photosynthesis and stored. This is why carbon dioxide accounts for 0.03% (volume fraction) of air composition for many years.

But in recent decades, due to the rapid increase of population and the rapid development of industry, the carbon dioxide produced by breathing and burning coal, oil and natural gas has far exceeded the past level. On the other hand, due to deforestation, a large number of farmland has been built into cities and factories, destroying vegetation and reducing the conditions for converting carbon dioxide into organic matter. In addition, the surface water area is gradually shrinking, the precipitation is greatly reduced, the conditions for absorbing and dissolving carbon dioxide are reduced, the dynamic balance of carbon dioxide generation and transformation is destroyed, and the carbon dioxide content in the atmosphere is increased year by year. The increase of carbon dioxide content in the air changed the temperature of the earth.

In the air, nitrogen and oxygen account for the highest proportion, and both of them can transmit visible light and infrared radiation. But carbon dioxide can't. It cannot penetrate infrared radiation. Therefore, carbon dioxide can prevent the surface heat from radiating into space and has the function of regulating the earth's temperature. Without carbon dioxide, the average annual temperature of the earth would be 20℃ lower than it is now. But if the carbon dioxide content is too high, it will make the earth seem to be in a pot, and the temperature will gradually rise, forming a "greenhouse effect." Besides carbon dioxide, there are other gases that can also cause the greenhouse effect. Among them, carbon dioxide accounts for about 75%, chlorofluoroalkanes account for about 15% ~ 20%, and there are more than 30 kinds of methane and nitric oxide.

If the carbon dioxide content doubles, the global temperature will increase by 3℃ ~ 5℃, and the polar regions may increase by 10℃, and the climate will be obviously warmer. Rising temperature will lead to increased rainfall in some areas, drought in some areas, increased intensity and frequency of hurricanes and intensified natural disasters. What is even more worrying is that due to the rising temperature, glaciers in polar regions will melt and sea levels will rise, and many coastal cities, islands or low-lying areas will face the threat of rising sea water or even be swallowed up by sea water. In the late 1960s, a drought lasted for six years in the pastoral areas of sub-Saharan Africa. Due to lack of food and pasture, livestock were slaughtered, and more than 6.5438+0.5 million people died of hunger.

This is a typical example of the "greenhouse effect" bringing disaster to mankind. Therefore, we must effectively control the increase of carbon dioxide content, control population growth, use fuel scientifically, strengthen afforestation, green the earth, and prevent global disasters caused by the greenhouse effect.

Scientists predict that the global average temperature will rise by 1 times for every increase of carbon dioxide in the atmosphere in the future, and the temperature increase in polar regions will be about three times higher than the average. Therefore, rising temperatures will inevitably melt polar ice, leading to rising sea levels. Sea level rise has a very serious impact on human society. If the sea level rises 1 m, the land directly affected is about 5× 106 km2, the population is about 1 billion, and the cultivated land accounts for about 1/3 of the total cultivated land area in the world. If extreme storm surge and salt water intrusion are taken into account, the coastal areas below 5 meters above sea level will be affected, and the population and grain output of these areas account for about 1/2 of the world. Some coastal cities may move inland, and most coastal plains will be salinized or swamped, which is not suitable for grain production. At the same time, it will also cause disasters to the middle and lower reaches of the river. Seawater intrusion will cause the river water level to rise, sediment deposition to accelerate, flood threat to intensify, and the downstream environment of the river to deteriorate sharply. The greenhouse effect and global warming have attracted worldwide attention. At present, the international convention on climate change is being promoted, and reducing carbon dioxide emissions has become the general trend.

Scientists predict that if I start cutting trees moderately now, global warming will be reduced by 5% by 2050. There is also the area of the earth and the sun's irradiation. The earth does not run on the same level as the equator in the solar system. This is the latitude of the earth, which is divided into five zones.

How are the five belts formed?

Latitude of five regions of the earth.

According to the variation of the height of the sun and the length of day and night with latitude, e799bee5baa6e78988e69d, an area with the same characteristics on the earth's surface, is divided into five hot zones according to latitude, namely, tropical zone, south temperate zone, north temperate zone, south frigid zone and north frigid zone.

In a year, the direct point of the sun always moves back and forth between 23 26 north latitude and 23 26 south latitude. Only in the area between the Tropic of Cancer and the south can you see the sun shining directly overhead. This area gets the most sunlight and heat in the world, and is called the tropical area. South of the Antarctic Circle and north of the Arctic Circle, the height of the sun is very small, and extreme days and nights can be observed. The obtained solar heat is very small and the temperature is very low, which is called the frigid zone. Between the Tropic of Cancer and the South Arctic Circle, the light and heat obtained are between the tropical zone and the cold zone, with moderate temperature and distinct seasons all year round, which is called temperate zone.

Tropical zone: the zone between the Tropic of Cancer and the Tropic of Cancer, located on both sides of the equator, with a latitude of 46 52' from north to south, accounting for 39.8% of the global total area. The sun height in this belt is very high all year round, and there are two opportunities for direct sunlight in the vast area between the two tropic of cancer, and the sun height angle varies between 90-43 8'. On the equator, the length of day and night is equal throughout the year, and the length of day and night gradually increases from south to north, but the difference between the longest and shortest day time is only 2 hours and 50 minutes. Therefore, the tropical region is characterized by high temperature all year round, with small amplitude, only relatively hot season and cool season or rainy season and dry season.

Temperate zone: the mid-latitude region between the Tropic of Cancer and the Arctic Circle. The south temperate zone and the north temperate zone span 43 8' respectively, and the total area of the south temperate zone and the north temperate zone accounts for 52% of the global total area. The height of the sun varies greatly in this area, and the tropic of cancer ranges from 90 to 43 8'. With the increase of latitude, the height of the sun gradually decreases, and the amplitude of the polar circle ranges from 46 52 ′ to 0. The height of the sun changes from big to small once a year, and the temperature also changes from high to low. The length of day and night also varies greatly, increasing to 24 hours in the polar circle. It can be seen that in the temperate zone, the height of the sun is smaller than that in the tropics, the heat obtained is less than that in the tropics, and the temperature is lower than that in the tropics. The height of the sun and the length of day and night vary significantly, so the four seasons are clearly the characteristics of temperate zones.

Cold zone: the zone with the north and south poles as the center and the polar circle as the boundary, accounting for only 8.2% of the global total area. The height of the sun in this belt is very small all the year round, the highest polar circle is 46 52', and the polar region is only 23 26', with a negative value. Extreme day and night phenomena become more and more obvious with the increase of latitude. Because the height of the sun is very low during extreme days, the ground gets little heat, and there is no solar radiation at extreme nights. Therefore, this area has the lowest temperature on the earth's surface. There are only winter and summer in a year, and there is no difference between spring and autumn. On the earth's surface, the spatial distribution of tropical zone, temperate zone and cold zone is characterized by uneven distribution of heat. The tropics are the largest heat source on the earth's surface and the poles are the largest cold sources, so the heat transfer and exchange between the equator and the poles is of decisive significance to the formation and distribution of global atmospheric circulation and ocean currents. The vast temperate zone is a zone of contact and heat exchange between cold and warm air, where the weather characteristics with four distinct seasons are formed.

How are the five belts formed?

The inclination of the earth's axis of rotation causes five belts formed by the direct sunlight at different angles, different sunshine hours and different times (in the equatorial region, the sun will never directly hit the ground, and the north and south poles will never directly hit the ground). So some places still bask in the sun directly in autumn. Second, the temperature is relatively high.

For example, some areas in the south, however, the farther north, the shorter the autumn, just like Beijing this year, when it changes, it suddenly gets cold. ..