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Changing face of the earth

  ”The Day After Tomorrow” has been called the best disaster film of the first decade of the 21st century and was released in 2004. Since the beginning of summer this year, the extreme high temperature events in the northern hemisphere have caused frequent mention of this old film on social media. “It’s a bit fitting to some extent,” wrote a Douban commentary on August 6 this year.
  The reality, however, is the exact opposite of the catastrophe depicted in the movie. What we are experiencing is an extreme heat event, and “The Day After Tomorrow” is about the extreme cold brought by three super hurricanes, and the area north of the US centerline has become a “snow world”.
  Although the phenomena are different, in the opinion of most scientists, the root cause is that the earth’s climate change caused by human activities has greatly increased the frequency and intensity of extreme weather.
  What’s even more irritating is that the foreshadowings before the cataclysm depicted in such fantasy films are appearing one by one in the real world.
  In “The Day After Tomorrow”, the earliest foreshadowing was the sudden appearance of cracks on the Antarctic glaciers, but in reality, in late July this year, the media took pictures of icebergs rupturing near Greenland in the northern hemisphere.
  The anomalies of these small heat waves have received little attention at the public level, but their impact is larger and more profound than the extreme heat events that have occurred this year.
  The acceleration of glacier melting has a weather vane significance for meteorological researchers. Meteorologists believe that there is a “climate tipping point” on the earth, which means that after this point, everything will change and there will be no going back. These tipping points include the Greenland ice sheet, the Antarctic ice sheet, the boreal forest, etc. The change.
  And all this has happened or is happening.
nature and people

  On August 3 this year, the China Meteorological Administration officially released the “Blue Book on Climate Change in China (2022)” to the public when mankind was suffering from the scorching sun. The Blue Book provides a comprehensive and objective view of how Earth’s climate has shifted.
  According to the latest monitoring information on climate change in China, Asia and the world, the Blue Book shows that the global warming trend is still continuing. In 2021, China’s average surface temperature, coastal sea level, and permafrost active layer thickness and other climate change indicators, Break observation records.
  In terms of specific meteorological indicators, the “Blue Book” shows that in the “atmosphere”, comprehensive observations of the climate system and a number of key indicators show that the global warming trend is still continuing. China’s warming rate is higher than the global average over the same period, and it is a sensitive area for global climate change. The average annual precipitation in China shows an increasing trend, and the regional differences in precipitation change are obvious. Extreme weather and climate events such as high temperature and heavy precipitation in China are becoming more frequent and stronger.
  On the “hydrosphere” indicator, the “Blue Book” shows that ocean warming has accelerated since the late 1980s, and the global average sea level has continued to rise. The sea level change along the coast of China generally showed a fluctuating upward trend. From 1980 to 2021, the sea level rise rate along China’s coast was 3.4 mm/year, higher than the global average for the same period.
  The indicators of the “cryosphere” are also not optimistic. The “Blue Book” shows that the global glaciers are in a state of melting and retreating as a whole, and the melting has accelerated since the mid-1980s. Arctic sea ice extent is showing a significant decreasing trend. The permafrost along the Qinghai-Tibet Highway shows a trend of degradation. In 2021, the average thickness of the active layer in the permafrost area along the Qinghai-Tibet Highway will be 250 cm, the highest value ever recorded.
  The steady decline of various indicators is the background of this summer’s sweltering heat. According to the monitoring and assessment of the National Climate Center on August 3, the comprehensive intensity of regional high temperature and heat wave events since June 13 has now ranked the third strongest since 1961, second only to 2013 and 2017.
  There is no doubt that when the climate continues to change rapidly, the living environment of human beings will no longer be suitable, and we urgently need to save ourselves. The first step to change is to correctly understand the principles of the formation of the earth’s climate and the causes of climate change.
The “Blue Book” shows that the global warming trend is still continuing. China’s warming rate is higher than the global average over the same period, and it is a sensitive area for global climate change.

  Climate change includes changes caused by both natural and human factors. However, the most important research direction is undoubtedly the human factor. In Rio de Janeiro, Brazil, in 1992, more than 150 countries formulated the United Nations Framework Convention on Climate Change (referred to as the “Framework Convention”). The Framework Convention defines “climate change” as: changes in the composition of the global atmosphere caused directly or indirectly by human activities, excluding changes in natural climate states observed over comparable time periods.
  The Framework Convention distinguishes between climate change caused by human activities changing the composition of the atmosphere and climate change caused by natural causes. That said, when we talk about “climate change” now, we mean climate change that is influenced by human activity.
  Impact on human activity is all the more important because it’s an area where we can make a difference. Wei Ke, a meteorologist and deputy director of the Monsoon System Research Center of the Institute of Atmospheric Physics, Chinese Academy of Sciences, gave a precise analogy: The process of climate change due to natural influence is very slow, just like a person will die when he is 100 years old. This is not worth making a fuss. However, the meteorological changes caused by human activities are very fast, which is equivalent to a person dying after two weeks of living, so there is a problem.
the scale of the earth

  The emphasis on the impact of human activities does not mean that the study of natural factors is not important. After all, natural and human factors jointly affect the climate.
  In the formation of each extreme event, human factors play a hidden probability role, while natural causes are more direct guides. For example, in this year’s extreme high temperature event, global warming is the climate background for frequent high temperature and heat wave events in the northern hemisphere, and the abnormal atmospheric circulation is the direct cause.
  In addition, the natural reasons include the ongoing La Niña event (spanning 3 years), which has provided important climatic background conditions for the occurrence and development of high temperature in the south since June this year. lead to a wide range of high temperature weather.
  Li Qinglan, a meteorologist and a researcher at the Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, told that according to statistical analysis, in the summer following most La Niña events, the Western Pacific subtropical high (referred to as the subtropical high) tends to move northward. Since late June this year, the subtropical high has moved northward, especially after the typhoon “Siamba” moved northward in early July, the subtropical high has strengthened to the west, and the Iranian high has been extended to the east. Combined with the mid-latitude continental high, a stable formation has formed over my country. The warm high pressure belt, which in turn caused a wide range of high temperature weather. Further, the water vapor carried by the subtropical high makes the central and eastern parts of my country relatively humid and the body temperature is higher.
  Therefore, natural causes remain the focus of research by meteorologists. In this field, “climate change” has been specifically referred to the influence of human factors, then climate change due to natural causes is called “natural variability” (Natural Variability).

atural variability can be caused by internal changes in nature, such as the internal fluctuations of the climate system, such as the Pacific decadal oscillation and the Atlantic multi-decadal oscillation. Natural variability can also be caused by external forcing, examples include changes in solar output and volcanic activity.
  From the perspective of influencing factors, there is no doubt that the influencing factors of human activities are only “the only person”, while the factors of natural variability are many and complex.
  Scientific research believes that changes in solar radiation, changes in Earth’s orbit, volcanic activity, and changes in atmospheric and ocean circulation are natural factors that cause global climate change.

  To clarify the different impacts of the two, Li Qinglan said that human activities, especially fossil energy consumption activities, have caused climate change with global warming as the main feature. However, natural factors are the main cause of the earth’s climate change, and climate disasters on earth are mainly caused by natural factors. The influence of human factors is not clear, and there are still debates.
  The most extreme scenario of climate disasters caused by natural causes is the “mass extinction” event once performed by the earth. Scientific research has shown that such an event has been played out 5 times, will it be repeated?
life is fragile

  Whether natural or man-made, it is not the earth that is vulnerable, but life, under possible climate change and extreme weather. This is why humans need to save themselves.
  During the existence of billions of years, the earth has experienced more extreme cold, and the entire earth was covered with ice and snow. At that time, even the oceans had ice sheets thousands of meters thick, which was called “ice and snow earth”.
  Li Qinglan introduced that the atmospheric circulation played an important role in the formation of the ice and snow Earth. When the ice line was outside the tropics, the Hadley circulation hindered its formation by transporting heat from the tropics to the subtropics; As it advances into the tropics, the near-surface branch of the Hadley circulation transports relatively cold air from the ice surface to near the ice line and to the open ocean, promoting the formation of snow globes.
Scientific research believes that changes in solar radiation, changes in Earth’s orbit, volcanic activity, and changes in atmospheric and ocean circulation are natural factors that cause global climate change.

  The earth has also experienced hotter periods. Zhou Tianjun, a researcher at the Institute of Atmospheric Physics of the Chinese Academy of Sciences, once drew a “earth-scale time”. According to him, 125,000 years ago, the atmospheric temperature was 0.5 to 1.5 degrees Celsius higher than it is now, and 15 million years ago, the atmospheric temperature was 5 to 10 degrees Celsius higher than it is now. The most extreme was about 55.8 million years ago, when the temperature was 10 to 25 degrees Celsius higher.
  Therefore, under the time scale of the earth, human beings with a history of more than 10,000 years have only seen too many “new things” in the world.
  Excluding the most extreme scenarios, the largest climate change events that humans have experienced are 4K events. The 4K event refers to a sudden climate change event about 4,200 years ago, which manifested as a large-scale climate anomaly, and the Asian monsoon also changed in reverse. , the decline of the early ancient civilizations of Greece and Egypt, etc.
  ”The 4K event is also closely related to natural internal variability.” Li Qinglan told that the 4K event may be a serious ancient ENSO event.
  It should be noted that ENSO refers to El Nio–Southern Oscillation, which is the wind field and sea surface temperature oscillations that occur in the equatorial eastern Pacific Ocean. ENSO is an ocean-air interaction phenomenon at low latitudes, which manifests as El Niño-La Niña transition in the ocean and the Southern Oscillation in the atmosphere.
  In the 4K event that may have changed the history of human civilization 4,200 years ago, as the North Atlantic cooled, heat accumulated in the south, which may have caused an increase in the temperature contrast between sea surface water and deep water in the warm pool of the Western Pacific. , which is conducive to the formation of ENSO phenomenon, and eventually leads to the reverse phase changes of the East Asian monsoon and the Indian monsoon.
  Of course, compared with ancient Egypt and ancient Greece 4,200 years ago, the level of technology mastered by modern humans is not comparable. Today, we can respond more effectively to extreme weather. However, we should still be in awe of the power of nature.
hidden crisis

  Climate change caused by natural causes is slow, but the consequences are catastrophic. This leaves human beings with a long and difficult time to choose.
  In the movie “The Day After Tomorrow”, when a climatologist gave a report to the U.S. government, emphasizing the vulnerability of the climate structure, it was ignored by senior government officials on the grounds that “the U.S. economy is as fragile as the climate”.
  What we know is that human society since industrialization has had an important impact on the natural world that has never been seen before. The dependence and waste of traditional energy sources lead to the emission and accumulation of greenhouse gases, and the resulting climate change makes human response tend to develop more traditional energy sources. The situation of moving the whole body in one shot exacerbates the environmental change.
  In the view of meteorologist Wei Ke, we have crossed the “climate tipping point”. This year is the third year of the climate crisis, and the continuous and extreme high temperature weather is already reminding us. Although there is not much that humans can do in the face of natural causes, reducing the impact of human factors can at least greatly reduce the probability of extreme climates.
  The consensus among meteorologists is that the climate crisis is already one of our most pressing and present challenges, and that the choice between environmental protection and economic development will continue to backfire on us. Although it is not as fast and extreme as the performance of “The Day After Tomorrow”, the emergence of this problem and the torture it sends are the meaning of this type of fantasy work.
In the view of meteorologist Wei Ke, we have crossed the “climate tipping point”. This year is the third year of the climate crisis, and the continuous and extreme high temperature weather is already reminding us.

  Returning to the focus on “natural variability”, climate change is certainly a long-term challenge, but it is worth noting that it also includes more subtle and more violent types of climate disasters, that is, “natural variability” in natural variability. “External forcing” factors, examples include changes in solar output and volcanic activity.
  Solar radiation is the most important factor in the formation of climate. There are many reasons for the change of solar radiation, mainly including the change of the earth’s orbit and the change of solar activity.
  Li Qinglan said that the three factors of the earth’s orbit—eccentricity, the inclination of the earth’s axis, and the position of the vernal equinox—all fluctuate with certain cycles, resulting in changes in radiation and climate change.
  Changes in solar activity mainly include sunspot activity and changes in the solar constant. Sunspot activity has a cycle of about 11 years, and in the long run, solar radiation is positively correlated with solar activity. The cold period of nearly 500 years in my country is just at the low level of solar activity, and the three cold periods correspond to the inactive periods of solar activity.
  Volcanic activity, by changing the transparency of the atmosphere, affects the amount of solar radiation reaching the surface. Strong volcanic eruptions, ejected volcanic dust and sulfuric acid aerosols, can be sprayed into the stratosphere. Since they are not washed and dropped by rain, they can strongly reflect and scatter solar radiation, weakening the direct radiation reaching the ground.
  In addition, asteroids colliding with the earth will also cause changes in the earth’s climate.
  The story of the extinction of dinosaurs as we know it was caused by a medium-sized asteroid. Li Qinglan introduced that the asteroid impact occurred on land, and the projectiles produced by the violent earthquake were rapidly ejected and burned in the air, which may bring about a large-scale fire, and the dust generated may always be dispersed in the atmosphere, affecting the atmospheric light transmittance and plant photosynthesis. , causing the global temperature to plummet.
  If it hits the ocean area, that’s not a good thing. Li Qinglan said that a large amount of water vapor is injected into the middle atmosphere, and the water vapor will easily condense at the temperature of the middle atmosphere, forming sulfuric acid-type aerosols, which will stay in the stratosphere for a long time. The years-long “covering the sky and the sun” will be a disaster for living things.
  Li Qinglan believes that humans should be alert to the effects of “natural external forcing”, especially volcanic forcing.
  It is especially vigilant that most of the volcanoes that can cause environmental damage are distributed on the land of the northern hemisphere, and about 90% of the population and most crops also grow in the northern hemisphere, so the northern hemisphere is more likely to be affected by volcanic eruptions. far-reaching.
  ”There are many studies predicting that the dormant period of the Yellowstone volcano in the United States is about to end, and the next supervolcanic eruption will be ushered in at any time. We should be vigilant and pay attention to this.” Li Qinglan said.

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