Frequent occurrence of abnormal weather, is climate change the root cause?
Sun Shao, Deputy Researcher of the Chinese Academy of Climate Sciences: For every 1 ℃ increase in temperature, the saturated water vapor in the atmosphere increases by about 7%, resulting in a significant increase in the frequency, intensity, and scale of polar precipitation work. Global warming will also affect atmospheric circulation patterns, leading to chaotic changes in the climate system and further increasing the frequency and intensity of polar precipitation work.
In addition, a direct impact of climate change is the northward movement of hurricane paths. "Warm seawater provides energy sources for hurricanes, while the weakened temperature gradient between tropical and temperate regions means that tropical cyclones will be able to more effectively transport water vapor to deeper inland areas
Freddie Otto, one of the founders of the "International Climate Attribution" organization: Climate change will not trigger climate work, as there are multiple reasons behind all climate work, but climate change will affect the probability and intensity of climate work. If a heavy smoker develops lung cancer, we cannot say that cigarettes cause cancer, but we can say that the harm that cigarettes pose to the body increases the probability of cancer
In recent years, the climate records around the world are being rewritten more and more frequently due to the extreme high temperature heat waves and extremely heavy rainstorm, mountain fires and droughts that last for months, and hurricanes that are "super long standby". People urgently need to find an answer - why are there more and more extreme climate jobs?
This is exactly the question that British scientist Frederike Otto attempted to answer. She and a group of researchers from around the world are known as "climate detectives", who conduct in-depth and rigorous statistical analysis of extreme climate work generated internationally, and provide scientific explanations as quickly as possible.
On August 10, 2023 local time, a fire broke out on the island of Maui in Hawaii, USA, sweeping across the entire island and causing thousands of residents to flee their homes. At the beginning of the 21st century, a group of scientists began to pay attention to the impact of climate change on polar climate work. Today, the research area has now developed into an independent science - Climate Attribution Science. This type of seminar aims to assist the public in timely understanding the possible causes of extreme climate work and how human behavior exacerbates the impact of these works, so that the government and the whole society can adjust and improve disaster prevention and relief strategies in advance. Attribution research provides us with a glimpse into the future of a warming world, making the connection between a series of disasters and climate change clearer, and allowing us to consider the relationship between climate and human social vulnerability in a new way. One of the reasons for disasters is ourselves.
Due to her contributions in the field of climate attribution, Otto was named one of the top ten figures in science by Nature in 2021, and was also named one of the 100 most influential figures by Time magazine in the same year.
If we want to prevent greater climate change, linking the meaning of climate change to everyone's daily life experiences is a very important part, and that's why I'm doing this assignment, "Otto told Breaking News (www.thepaper. cn).
However, science also has its limitations. We know that there will be more extreme climate work in the future, as humans are still warming the Earth, "Otto said." We live in an international world where the interests of a few people are maximized and the interests of the majority are harmed, and climate change is no exception
Is climate change the driving force of rainstorm and flood?
On March 19th, Sun Shao, Deputy Researcher of the Chinese Academy of Climate Sciences, visited and exchanged ideas in Southern California, USA. At this time, California is approaching the end of a long dry season that has lasted for several months. Between December 31, 2022 and March 25, 2023, California experienced at least 12 heavy rainfall events caused by atmospheric rivers, resulting in floods that claimed at least 22 lives. The so-called "atmospheric river" refers to a water vapor transport belt composed of atmospheric activities, which transports a lot of water vapor from tropical and subtropical waters to higher latitude areas to form precipitation, and can carry more than 10 times the average flow of the Mississippi River estuary, the largest river in the United States.
When I first arrived in the United States, it was still cloudy and rainy for the first two weeks, which was very unusual in the local area. This winter, there was a lot of rainfall in California, and I saw some local grass growing taller than people outside. And this winter, some areas in California experienced temperatures close to zero. These are all things that haven't happened in the past 10 years, "Sun Shao told Xiong News.
A few months later, the North China region of China experienced the most intense rainfall since 1964 from July 29th to August 1st. To some extent, this is also an extreme rainfall caused by the long-distance water and gas transportation of atmospheric rivers.
The direct cause of this work is the combined impact of Hurricane Dujuan and the subtropical high, which forms the north-south water vapor transport channel in eastern China. Following the northward movement of water vapor, it encountered obstacles from the Taihang Mountains and Yanshan Mountains, resulting in heavy rainfall in the eastern part of the Taihang Mountains. At the same time, Hurricane Kanu in the western Pacific also transported a lot of water vapor to northern China under the guidance of the subtropical high pressure. The convergence of the water vapor of the two hurricanes in the North China Plain led to the record breaking heavy rainfall work.
In Sun Shao's opinion, the recent rainstorm in North China has some similarities with the heavy rainstorm in Henan two years ago in terms of the cause of formation. Both of them are under the combined effect of double hurricanes and subtropical high pressure. A huge amount of water vapor is continuously transported to the north. After the two water vapor transport belts converge, they suffer from the effect of terrain uplift, and converge and uplift in front of the mountains to form a rainstorm.
On August 1, 2023, rainstorm to heavy rainstorm in many places in Beijing caused the river to rise. This climate system only needs to be able to maintain for a few hours to a whole day to trigger extreme rainfall processes. Conversely, all the conditions mentioned are indispensable, as long as they are the same, the rainfall intensity will significantly decrease, "said Sun Shao. In China, climate change remains a less frequently mentioned keyword after the emergence of extreme climate work. But in the international scientific community, it is a frequently mentioned backdrop.
A consensus in the scientific community now is that climate change can affect rainfall intensity through the addition of water vapor in the atmosphere. This is because global warming leads to an increase in surface temperature of seawater, an increase in transpiration power, and warmer atmospheres containing more water. For every 1 ° C increase in air temperature, 7% of moisture can be added to the atmosphere. Therefore, precipitation will increase in this situation. This explains why climate change has led to an increase in global extreme rainfall. However, Sun Shao further suggested that the addition of water vapor content can lead to an increase in total rainfall, rainfall intensity, and impact scale, but the assumption that the duration of rainfall will be extended is currently lacking scientific basis.
The sixth statement (2021) of the United Nations Intergovernmental Panel on Climate Change (IPCC), the most prestigious global climate science organization, acknowledges the above findings. The statement further points out that due to climate change caused by assumed reasons, extreme rainfall has become more frequent and intense in most regions of the world since the 1950s, especially in Europe, most of Asia, central and eastern North America, as well as parts of South America, Africa, and Australia; The floods in the above-mentioned areas may also become more frequent and severe, although other human factors may also have an impact.
Secondly, more chaotic connections come from climate change, which can also affect the frequency of conditions for heavy rainfall, such as storms and sudden storms, which in turn come from chaotic climate phenomena and certain atmospheric circulation patterns.
For example, when talking about the connection between climate change and hurricanes, Sun Shao agrees with the statement that rising sea temperatures and increased water vapor content will make it easier to form strong hurricanes. On the other hand, he points out that climate change cannot explain the phenomenon of double hurricanes. "In fact, with global warming, the number of hurricanes generated has not significantly changed in the past thirty years. The direct impact of climate warming is that hurricane paths have shifted northward; warm seawater provides energy sources for hurricanes, and the temperature gradient between tropical and temperate regions is weakened, which means that tropical cyclones will be able to transport water vapor more effectively to deeper inland areas," Sun Shao said.
On July 22, 2021, in Zhengzhou, Henan Province, after the extremely heavy rainstorm, the city was flooded in a large area. Back to the rainstorm in rainstorm in 2021, the rainfall in Zhengzhou, the provincial capital, for three days was almost equal to the average annual rainfall in the area. A climate attribution study announced by a team of experts from the Chinese Academy of Sciences and Peking University found that anthropogenic climate change increased the precipitation during this extreme work by 7.5%. Chao Qingchen, Director of the National Climate Center, recently pointed out in a media interview that since the beginning of this century, the frequency and intensity of extreme heavy rainfall across the country have been increasing. In the foreseeable future, the overall precipitation in China will show an increasing trend under global warming. From a regional perspective, heavy rainfall was originally more frequent in the south, but in recent years, it has been found that there is an increasing trend of heavy rainfall in the north.
In the past 12 years, the North China Plain region has witnessed several extremely heavy rainstorm, which has posed a severe socio-economic impact. However, Sun Shao and most climate experts point out that this does not mean a new pattern of "southern drought and northern flooding" is emerging in China.
The fundamental pattern of China's climate is that there is more precipitation in the south than in the north. Against the backdrop of worsening climate change, the extreme rainfall in the northern region shows a trend of frequent and strong occurrence, but it will not change the original climate pattern. "Sun Shao pointed out," Under the influence of climate change, the total rainfall in most regions of China will increase in the future. "In percentage, the rate of increase in the north may be higher than that in the south; in absolute value, the increase in the southern region is still more significant
Unveiling the veil of climate attribution
In January 2003, as the floodwaters of the River Thames continued to rise and gradually hit the home of Oxford University professor Myles Allen in the south of Oxford, England, he was drafting a paper later announced in Nature discussing "The Responsibility of Climate Change".
He wrote, "It may not always be impossible to attribute extreme climate work to climate change - however, given our current understanding of the climate system, it may still be difficult to achieve. If researchers can make breakthrough developments, science may be able to link extreme climate with climate change
At that time, I was thinking: as a scientist, how to use quantitative methods to calculate the degree of danger caused by climate change in specific jobs, "Allen recalled to the surging news.
Alan is a top global scholar of Earth system science and an expert on climate issues, having previously served in the Intergovernmental Panel on Climate Change (IPCC) of the United Nations. That year, Allen and his partner from Oxford University, Peter Scott, announced a paper in the journal Nature. The paper suggests that human induced climate change is likely to more than double the risk of a rare heatwave similar to that experienced in Europe in 2003, which resulted in over 70000 deaths.
On August 9, 2023 local time, in Louisiana, USA, a child pressed their face against a portable fan to cool down. This article is considered to be the first international study on the attribution of extreme climate work, which explores the scientific correlation between extreme climate work and climate change, and then begins to transform the attribution of extreme climate from a scientific impossibility to a new research category. In the following 20 years, attribution science gradually took root and sprouted. Global climatologists have discussed various climate works around the world, including extreme heat, heavy rainfall and floods, tropical cyclones, and droughts. Allen's intuition at the time was correct, and the attribution of extreme work was not only possible, but also became one of the most rapidly advancing frontiers in climate science.
In 2021, as the most prestigious climate research organization in the world, the Intergovernmental Panel on Climate Change (IPCC) made it clear for the first time in its latest sixth assessment statement that, based on increasing evidence of "extreme climate work attribution," greenhouse gas emissions caused by human activities need to be attributed to climate change and the increasingly frequent occurrence of extreme climate work. The necessity and importance of climate attribution have been confirmed for the first time.
The attribution of climate was like an unexpected journey to Otto. In 2011, after obtaining his doctoral degree in Berlin, Otto moved to London and worked at the Environmental Change Institute at Oxford University. At that time, Allen at Oxford University gave her a precious primitive climate database. At that time, Miles said to me, 'We have a bunch of climate data here, go ahead and do whatever you want,' "Otto recalled.
In 2015, Otto participated in the creation of the World Weather Attribution (WWA) organization, an international research initiative aimed at quickly announcing the scientific reality of specific polar climate work.
So, how do scientists find the correlation between climate change and polar climate work through climate attribution?
Otto and Sun Shao explained to the surging news that, first of all, it is necessary to choose a severe climate work with obvious influence and important significance, such as rainstorm, drought, heat wave, etc. This job should have a satisfying impact in terms of timing and geography.
We will consider whether the work is generated in a place where there has not been much research yet, and whether effective data and models can be obtained to open up the discussion, "Otto said.
Data collection is one of the key elements in determining whether climate attribution operations can be carried out, including climate observation data (temperature, precipitation, wind speed, etc.), surface data (soil moisture, vegetation, etc.), ocean data (sea surface temperature, ocean circulation, etc.), and other environmental data. Compared to developed countries that can collect data in a timely manner and have strong scientific research foundations, the application of climate attribution in our country and region is often hindered by many limitations.
Sun Shao introduced that after obtaining the data, scientists conducted specific analysis of climate data during their work period to understand the progress of the work, spatial and temporal distribution, and possible influencing factors. Then further simulation and attribution analysis will be conducted.
On July 23, 2023 local time, the destructive effects of the continuous rise in ocean temperatures around Florida, USA - coral bleaching and death. Scientists use climate models to simulate a real international climate environment, while another set of models constructs a climate environment without human activities producing greenhouse gases. After simulating and calculating two models, the "contribution" of climate change to the probability of extreme climate production was analyzed. The initial stage of climate attribution science has been controversial. Many scientists still hold a vague sentiment of 'unwilling to talk much' about the correlation between single pole climate work and anthropogenic climate change, thinking that 'the model is not good enough'.
Faced with these doubts, Otto explained a core procedure: peer review, all research methods, need to obtain widespread recognition from peers. On the other hand, ultimate transparency is an important pillar supporting the credibility of research. All the data is exposed, all the research methods have specific introductions, and everyone can reproduce the research to see if they can reach the same conclusion, "Otto said.
Although climate attribution can tell us a lot, it is not without limitations.
"At present, we can't attribute the intensity and duration of rainstorm alone, because there is no climate model that can draw accurate conclusions," Sun Shao's view is basically consistent with Otto's, "we can only confirm through the climate model that heavy rainfall will occur more and more frequently in China."
Otto emphasized that it is a misconception to believe that climate change is the sole cause of extreme climate work. If a heavy smoker develops lung cancer, we cannot say that cigarettes cause cancer, but we can say that the harm of cigarettes to the body increases the probability of cancer. Similarly, climate change will not cause climate work, as there are multiple reasons behind all climate work. However, climate change will affect the probability and intensity of work. Therefore, we need to understand how climate change affects individual climate work. Scientists can provide answers through extreme work attribution, "she said.
In addition, there are differences in the accuracy of attribution for different types of extreme climate work. The Otto team, who is currently studying wildfires in Canada, has found that attribution research for wildfires requires analyzing temperature changes, rainfall from the previous season, as well as humidity and wind power.
Wildfires are very chaotic, and compared to heatwaves and heavy rainfall that only require checking temperature and rainfall, attributing wildfires requires more time, "she said.
In addition to wildfires, there are also attribution studies related to drought and storms. Drought is often the result of multiple factors working together. Drought depends on previous years' rainfall, rainfall during drought periods, and vegetation types. "If it were trees, water would be retained in the soil, but if it were soil, it would quickly become dry." Regarding storms, Otto pointed out that there is currently no precise observational data or model to explain such issues.
Compared with other polar climate work, the research on the attribution of heat wave and rainstorm is the most convincing. "If there is a heat wave, we can always confidently say that due to climate change, the climate will become hotter, and more likely rainstorm will occur. On a global scale, we do see that due to climate change, the rainstorm will become more severe, which is very persuasive, but we cannot make such speculation about other types of work," Otto said.
How to face a more extreme future
What is the significance of understanding climate attribution in relation to real society and the future?
The correct understanding is the first line of defense in dealing with extreme climate work. Otto believed that people still lack understanding of how climate change affects the climate.
Many people think that all the bad jobs that arise are caused by climate change, and perhaps have nothing to do with climate change. This is all a misunderstanding, "she said.
Otto believed that part of the reason was due to the differences between climatologists who serve as daily climate forecasts and those who study long-term climate change, but climate attribution research is gradually bringing the two together.
After long-term engagement in various climate attribution studies, Otto discovered that population and regional vulnerability are decisive factors in determining whether extreme climate work will become a disaster.
Climate factors are sometimes not decisive factors in creating disasters. To determine whether the extreme climate present in the region can be called a disaster, it is necessary to consider the vulnerability of the region at the time of the incident. In some areas, due to the lack of such incidents, the awareness of prevention is poor, "said Sun Shao.
Otto also agreed that improving public awareness and perfecting warning systems were of paramount importance in disaster prevention operations at that time. Otto mentioned the 2021 European floods, in which at least 243 people died. "Germany is a prosperous country, and there are still people dying from floods. People's deaths are due to the local government not implementing any truly effective warning systems," she said.
On June 21, 2023 local time, in Berlin, Germany, activists brought "three monkeys" to raise awareness of climate change issues. Eliminating social injustice is the driving force behind Otto's engagement in climate change research. Climate change is exacerbating inequality, "she said. The worsening of the climate crisis will primarily threaten vulnerable groups, putting them at risk of losing their livelihoods, perhaps unable to afford food due to rising prices, while wealthy people have the means to adapt. The poor are most severely affected by climate change, and in Europe or the United States, those who die from heat waves are mostly low-income people who can only live in poorly insulated houses, usually in areas with severe air pollution. Otto stated, "Wealthy people can easily avoid the impact of climate change, which I think is why nothing will happen. Because we live in an international world where the interests of a few are maximized and the interests of the majority are harmed, climate change is no exception. The wealthy should bear the greatest responsibility for climate change," Otto said.
In southern countries, climate attribution research has become increasingly difficult due to the lack of reliable climate data and limited local research capabilities. But these regions are the easiest to be affected by climate change and its potential extreme climate impacts. Otto expects low-income countries to strengthen their research in these areas with the support of affluent nations in the coming years.
It is this somewhat politicized attitude that has led to some criticism of Otto, who accuse climate scientists of focusing on scientific research but remaining silent on other work.
Otto's response to this was, "There are no neutral scientists." She said, "The questions we raise are always influenced by our values, who is funding us, and where we live. Making science transparent is the real science - not pretending it didn't happen
During the conversation with the surging news, Otto repeatedly emphasized the importance of stopping the burning of fossil fuels: as long as the international community continues to burn fossil fuels, extreme work will become even more extreme, especially during heat waves. Due to increasingly extreme high temperatures, air conditioners powered by fossil fuels operate for long periods of time, and the gears of a vicious cycle also operate accordingly.
With the increasing maturity of climate attribution science, many experts from the legal field have pioneered a new possibility for the practical value of climate attribution - climate attribution science intervenes in public litigation such as court cases through evidence. In a study announced in Nature Climate Change in 2021, Otto and his collaborators analyzed 73 climate litigation cases worldwide and found that the evidence used was now ten years outdated.
In terms of policy formulation, the overall development has been very slow, and people affected by climate change have hardly received any compensation or assistance. In Otto's view, the losses and hazards are still borne by the affected parties, even if they are caused by the burning of fossil fuels. Many lawyers believe that we can use the court to accelerate climate change actions
Now, a German court is hearing a case where a Peruvian farmer has filed a lawsuit against Germany's largest fossil fuel company, RWE, claiming that RWE has always been a major emitter of greenhouse gases, which cause glacier retreat and increase the risk of flooding in the region. Coincidentally, Oregon City in the United States filed a lawsuit in June this year, accusing large oil and gas companies of losses caused by the 2021 heatwave. Otto admitted, "These cases have not been successful so far, but obviously testing is very important
In the movie 'Don't Hold Your Head High', Leonardo DiCaprio plays the scholar. Some people often compare the issue of climate change to the story in the movie 'Don't Hold Your Head High'. Leonardo DiCaprio plays a scholar who announces a warning that an asteroid will collide with Earth within six months, but finds that no one is willing to listen. But Otto doesn't think this is an appropriate metaphor. "I am an optimistic person. If we want to prevent climate change from worsening, linking the meaning of climate change to our daily experiences is an important part of it. In other words, investing funds in people, early warning systems, social security systems, and better healthcare systems is what truly helps people. Climate change is a social problem with technological solutions