Why do cold waves and snowstorms break out frequently in global warming?

Recently, many areas in the northern hemisphere, including China, have been hit by long-term cold currents and snowstorms. Some people think that this shows that the global warming trend has changed and the climate will change from "warm" to "cold". What caused the recent frequent occurrence of cold snap and snowstorm? Has the trend of global warming changed? Our reporter interviewed Ding, an academician of China Academy of Engineering and a climate expert, and made an in-depth analysis on these issues that people are generally concerned about. The change of Arctic Oscillation and "false El Nino" cause severe cold, and the climate in China may return to warmer in February. Reporter: Since the winter of last year, many parts of the world, including China, have frequently encountered cold currents and snowstorms. What is the main reason? D: Cold current and snowstorm are mainly concentrated in three places: one is the eastern part of North America, especially the southeastern part of North America; The second place is Northern Europe and Western Europe; The third place is the east of Asia, especially Northeast Asia, including North China and Northeast China of China. From our current analysis, there are at least two reasons why cold air appears early and lasts for a long time in the northern hemisphere. The first reason is that the Arctic Oscillation (the seesaw phenomenon of pressure change in the middle and high latitudes in the northern hemisphere) is in a negative phase. In winter, there is a great depression in the Arctic, which is very cold. Cold air is basically confined to the polar regions, surrounded by high pressure outside, and it is difficult for cold air to go south. This is the situation of atmospheric circulation that appeared in our previous decades, which is called the positive phase of the Arctic Oscillation. However, since the beginning of this century, the positive phase of high in the south and low in the north has gradually weakened and developed into a negative phase, which means that the polar pressure will increase and the pressure in the southern part of the northern hemisphere will gradually decrease. In this way, the high pressure ran to the polar region, and the polar low pressure was squeezed out. The cold air in the polar regions is very cold, forming a cold wave and a cold current. In fact, this phenomenon has appeared many times in history, but this time the high pressure enveloped the polar regions for a very long time, which was very abnormal. The second reason is that from July and August to 165438+ 10 last year, there was a "false El Nino" phenomenon in the ocean, and its climate impact was very similar to that of "La Nina". When La Nina appeared, the center of ocean warming was in the central and western Pacific Ocean, and there were usually cold years. It is cold and rainy in the north of China. For the severe winter in China, the influence of "false El Nino" is a very important factor. This reason is not the main reason for the United States and Europe. Reporter: So, when will this abnormal situation end? D: Now, the phenomenon of "false El Nino" has basically ended and is developing normally. We estimate that in February, the center of ocean warming will return to the equator, the Middle East and the Pacific Ocean, and once it returns to its normal position, the climate in China should start to warm. Arctic oscillation is gradually returning to normal. According to the forecast of the National Climate Center, it is generally believed that after the transition period of 65438+1late October, the climate in February may return to the original track, that is, return to the normal state of warmer weather. Severe cold weather is an "interlude" in the process of climate warming, not a "prelude" to climate cooling. Reporter: What are the main features of China's climate this winter? D: This winter, winter snow came one month earlier than usual. From June 5438 to February last year, it was very cold, with record-breaking low temperatures and strong snowstorms. However, this is not a large-scale rain and snow weather in the country, nor is it a national cold winter. This extreme weather event mainly affects the north, including North China, North Xinjiang, North Inner Mongolia and Northeast China. According to recent discussions among scientists, from the perspective of the whole history of China, this winter can only be regarded as moderately cold in the last two or three hundred years. Recently, the temperature in some parts of China is still high, and the national average is close to normal. Reporter: In recent years, "warm winter" has become a common word, but the winter in the last two years seems to be getting colder and colder. D: Actually, in the first 10 year of this century, we experienced three major "cold wave events": the winter from 2004 to 2005 was relatively cold, and two cold waves in eastern China had a great impact, and 40% of oranges in Taiwan Province Province were frozen. It was a major "cold event" in China under the background of climate warming, but no one paid attention to it. Then there was the freezing rain and snow disaster in early 2008, and the recent cold wave blizzard in the north. Reporter: In your opinion, is this extremely cold weather an "episode" in the process of climate warming or a "prelude" to climate cooling? D: We can see that the climate will continue to warm up after every "cold event". For example, after the winter of 2004-2005, 2007 was the warmest year with the highest average temperature in China. Therefore, it is difficult for a cold event to change the annual average temperature, let alone the whole warming trend. From this perspective, extreme cold weather may be an "episode" in the process of climate warming. The three "cold events" that China experienced in this century did not change the general trend of climate warming. Climate change leads to frequent extreme weather events, and we should be prepared for extreme "cold events" while dealing with climate warming. Reporter: Some foreign experts have suggested that in the next 20 to 30 years, the world will experience a "mini ice age" and the climate will get colder. What do you think of this view? D: There are three factors that affect the climate: the first is the greenhouse effect caused by greenhouse gas emissions; The second category is natural external forces such as solar activity and volcanic eruption. The most important period of solar activity is 1 1 year. When there are many sunspots, the earth may get warmer. Volcanic eruption spews out a lot of dust, the most important of which is sulfide, which can reflect sunlight and cool the earth; The third category is the changes within the climate system. The climate system consists of five layers: atmosphere, ocean, biosphere, earth circle and cryosphere. All these five layers can change themselves, and the interaction between them can also change. It is difficult to understand their internal changes. The world will experience a "mini ice age", which is a new viewpoint put forward by a foreign scientist. He put forward his own point of view from the angle that the ocean affects the climate. However, climate change is not only determined by the ocean, but also influenced by volcanic eruptions, solar activities and other types of internal changes in the climate system. It is difficult to make an accurate prediction of these factors. Therefore, I think the viewpoint of "Little Ice Age" is worthy of attention, but according to our current research, it is still difficult to draw such a conclusion. Reporter: What preparations should we make in the face of the changeable climate? D: In a place, if the average temperature remains the same, but the range of temperature change increases, it is also an obvious climate change. This problem is often ignored by everyone. People are more concerned about the change of climate average, but in fact this is only one aspect. The appearance of severe cold and severe cold should also attract our attention. Climate change causes extreme weather events to become frequent and their return period to be shortened. For example, the cold wave may be once in a hundred years before and once in 50 years after climate change. I think that warming is a general trend, and we should be prepared, but at the same time we should be prepared to deal with extreme "cold events". /20 100 1 19/n 2696793 16 . shtml