20 13 extreme weather events

Why are extreme weather increasing? Zhou Botao, deputy director of the Climate Change Adaptation Office of the National Climate Center, said: This may be related to global warming. He believes that after global warming, the energy distribution in the atmosphere will change, such as the increase of evaporation and the acceleration of water circulation, which will lead to more extreme events.

Take drought and flood as an example. After climate warming, the temperature of land and ocean surface will rise, and evaporation and transpiration will occur more easily. The water vapor content in the atmosphere will increase, and the water that can be contained will also increase. This means that more water vapor is needed to achieve precipitation conditions. When the atmosphere is not saturated, it will continuously absorb water, making the land drier and forming drought. Once the atmosphere is saturated, it is easy to form heavy precipitation due to the increase of atmospheric water content, which may lead to floods. In addition, due to the strengthening of heat and water vapor exchange between the northern and southern hemispheres, the climate is more likely to become abnormal.

Under the background of global warming, the climate in China has also changed obviously in the last hundred years. In the past century, the annual average temperature in China has increased by 0.5℃-0.8℃. The trend of climate warming in China will be further intensified in the future. It is predicted that the annual average temperature in China may increase by 0.5℃-0.7℃ in 2020 and 1.2℃-2.0℃ in 2050. In the next 50 years, the average annual precipitation in China will increase. It is predicted that by 2020, the national average annual precipitation will increase by 2%-3%, and may increase by 5%-7% by 2050.

Zhou Botao said that with global warming, the frequency and intensity of global extreme events may increase in 2 1 century. It is expected that most land areas will be in more "hot water" in the future.

Scientists say that some extreme events, such as the drought in the United States on 201/kloc-0 and the heat wave in Europe in 2003, may be caused by the slowdown of huge wave weather flow in the northern hemisphere caused by global warming.

This conclusion comes from the study of the circuitous air system around the earth. Reuters said that this conclusion is helpful to deepen people's understanding of these extreme events.

Scientists say that this kind of earth airflow usually sucks warm tropical air when it flows north, and cold air from the Arctic when it flows south. However, in the summer of recent years, these air currents tend to slow down more frequently, leading to sultry weather in some areas.

"In some recent extreme weather events, these planetary waves stopped in their orbits for almost several weeks," wrote Vladimir Petoukhov, the lead author of the German potsdam institute for climate impact research research paper.

"Therefore, the heat is left behind, instead of bringing warm air first and then cold air as before." He said in the Proceedings of the National Academy of Sciences.

The temperature difference between the North Pole and its low latitude south is usually the main driving force of wave flow, and the distance between peaks usually covers 2500 km to 4000 km.

However, the use of fossil fuels by human beings leads to the accumulation of greenhouse gases in the atmosphere, which in turn causes the Arctic to heat up faster than other regions, slowing down this mechanism of promoting waves and currents.

Hans Joachim Schellnhuber, co-author of this study and director of potsdam institute for climate impact research, said that past studies have linked this extreme event to global warming, but they have not determined a fundamental mechanism.

This study only considers the northern part of the earth, and only in summer. Another study by Portuhov at 20 10 shows that the cold current in winter in Europe in recent years is related to the low ice content in the Arctic Ocean.

Nearly 200 governments agreed to reach a new agreement before 20 15 to curb the rise of global greenhouse gas emissions, which will take effect in 2020. El Nino means "child" in Spanish. El Nino is a phenomenon that leads to an abnormal rise in sea surface temperature around Christmas in the cold ocean current area on the west coast of the United States. It is like a "warm pool", which changes the atmospheric heating field through the change of surface temperature, thus bringing changes to the weather in various places, causing floods in the original dry and rainy places, while the rainy places are prone to long-term drought and lack of rain.

The basic feature of El Nino phenomenon is that the sea surface temperature along the Pacific coast rises abnormally, the sea water level rises, and a warm current flows southward. It turns cold water in the East Pacific into warm water, causing tsunamis and storms, causing drought in some areas and excessive rainfall in others.

In 1960s, meteorologists found that El Nino was closely related to the Southern Oscillation. When the pressure difference decreased, El Nino appeared. After El Nino, due to the warming of warm current, the monsoon flowing from east to west in the Pacific Ocean was greatly weakened, which significantly changed the atmospheric circulation and greatly affected the climate of countries along the Pacific Ocean. The originally wet area was dry, and there was a flood in the dry area. When this pressure difference increases, the seawater temperature will drop abnormally, which is called "La Nina phenomenon".

In recent years, scientists have put forward some new explanations for the El Ni? o phenomenon, that is, El Ni? o may be related to submarine earthquakes, changes in seawater salinity and changes in atmospheric circulation. El Nino occurs periodically, about once every 2-7 years. After entering the 1990s, with global warming, El Nino phenomenon appeared more and more frequently.

When El Nino occurred, it spread all over the central, eastern and Pacific waters, and the positive anomaly of surface water temperature was as high as 3℃ or above. The intense rise of seawater temperature has led to a great decrease of plankton in the water, which has hit Peru's fishery production and led to floods or droughts in Ecuador and other equatorial Pacific regions. This El Nino phenomenon is called El Nino event. It is generally believed that the sea surface temperature anomaly for three consecutive months is above 0.5℃, which can be considered as an El Ni? o event. On the contrary, if the negative sea surface temperature anomaly along the coast of South America is above 0.5℃ for three consecutive months, it is considered as an anti-El Ni? o event, also known as La Ni? a event.

At present, according to the research of meteorologists, it is generally believed that the occurrence of El Ni? o event is a harbinger of climate disasters in many parts of the world, so its monitoring has become an important content in climate monitoring. According to historical records, since 1950, there have been 13 El Nino phenomena all over the world. The one that happened in 1997 and continues to this day is the most serious. Mainly manifested in: from the northern hemisphere to the southern hemisphere, from Africa to Latin America, the climate has become weird and incredible. A cool place is like a fire. It suddenly snows in warm spring, but it doesn't rain when the rainy season comes, but floods in dry season. .....

Scientists believe that the occurrence of El Nino phenomenon is related to the deterioration of human natural environment, the direct result of the intensification of global greenhouse effect, and the result of human beings demanding too much from nature and not paying attention to environmental protection. According to the research on the relationship between the change law of solar activity and El Ni? o in the past hundred years, scientists found that the period from sunspot reduction to valley value is the frequent period of El Ni? o, with two or three El Ni? o occurrences.