Average temperature 15 degrees. Oxygen concentration 21%. Seawater salinity 3.4%. The Earth is surprisingly self-managing. It has maintained the optimal conditions for life on its own through its self-regulating function. If the Earth's self-management collapses, a great disaster will occur. If the oxygen concentration increases by just 1%, wildfires caused by lightning will increase by 70%. If the seawater salinity concentration reaches 6%, most marine life will become extinct. Humanity will be miserable in the face of disaster. So, we must take action before it happens. The sea ice where polar bears live. It expands in the winter and shrinks in the summer, reaching its smallest size in September. The problem is that it is not recovering well due to global warming. This means that the total area of ​​the ice is gradually shrinking. The reflectivity of solar radiation is called 'albedo'. We can estimate the stability of the Earth's climate through this albedo. The process is as follows. As global warming reduces ice, the solar energy that is not reflected and absorbed increases the temperature of the Arctic Ocean. The warmed seawater melts the ice again. As the ice decreases, the albedo decreases further. The Earth is caught in a vicious cycle and retains heat. Have you ever thought about why winter cold is getting worse while the Earth is getting hotter? It is because there is a problem with the jet stream that lifts cold air to the poles, the top of the Earth. The jet stream becomes stronger as the difference in air temperature between the Arctic and mid-latitudes increases, but when the temperature in the Arctic rises and the jet stream weakens, the cold air descends. It is easy to understand if you think of it as falling down when you slow down a hula hoop. One of the causes of the strange waves that hit East Asia, including the Korean Peninsula, in January of this year was the weakening of the jet stream. We cannot talk about the Arctic without talking about sea levels. Will the sea level rise if the temperature in the Arctic rises? It is commonly thought that melting Arctic ice will cause sea levels to rise, but that is half right and half wrong. Melting Arctic sea ice means that the ocean temperature has risen. When the water temperature rises, sea water undergoes thermal expansion. Since its volume increases, the sea level will rise to some extent. This is only an effect of rising water temperature. Just because ice floating on the ocean melts, the sea level does not rise noticeably right away. Just because ice in iced coffee melts, the coffee does not overflow. It is the same principle. Let me pause here. What directly affects sea level rise is not the 'iceberg' on the Arctic Ocean, but the 'glaciers' that cover the land. This is a video taken in Alaska, USA, a while ago. This is what happened when the glacier melted and the lake level rose. The speed at which the glacier is melting is unusual. The remains of climbers who went missing in the Alps a long time ago are being found one after another due to the melting ice. Let's go back to the Arctic. Arctic sea ice is related not only to polar bears, but also to the human living environment. As the icebergs that act as a shield melt, the winds and waves become stronger, increasing erosion. Robbie Mallett, a polar ice researcher, estimates that about 4.5 million people will be seriously affected by erosion. Polar bears will not only lose their habitats. They could disappear from the face of the earth entirely due to changes in their DNA. Polar bears have secured genetic diversity by moving around and mating with other species. This has increased their ability to adapt to climate change, lowered their risk of disease, and improved their survival. However, as the ice melts and they cannot move, the possibility of winter interbreeding, or mating between the same species, has greatly increased. If genetic diversity decreases, not only will their survival ability decrease, but their reproductive ability will also decrease, which could eventually lead to extinction. According to the National Snow and Ice Data Center (NSIDC), the area of ​​summer icebergs in the 2010s has decreased by about 40% compared to the 1980s. In terms of volume, it has decreased by 70%. The earth has experienced similar things in the past. Experts are focusing on the 'last interglacial' of 120,000 years ago According to Swedish climate scientists, when the climate was similar to the current one, all the Arctic sea ice melted. The interglacial period has come again. The same thing is happening again. [David Barber / Director of the Institute of Earth Environment and Resources at the University of Manitoba, Canada: In the near future, there will be no ice in the Northern Hemisphere during the summer. This is a really big change in the Earth system.] However, the cause of the ice melting is different from the past. Rather than natural factors such as solar or volcanic activity, greenhouse gases that cause global warming are considered the main culprit for melting the Arctic ice. There have even been warnings that the Arctic sea ice could disappear completely in September, the middle of summer in the Arctic. This is the content of a paper published in the international academic journal 'Nature Communications' by a joint research team from POSTECH, the Canadian Environment and Climate Change Agency, and the University of Hamburg in Germany. The research team predicted that if the current greenhouse gas emissions continue, all the ice will melt in September 2030. Even if we reduce carbon emissions, they also projected that the ice in September could disappear by the 2050s. This does not mean, “Let’s give up because it won’t work no matter how hard we try.” The implications of the research results are more hopeful than gloomy. [Min Seung-gi / Professor, Department of Environmental Engineering, POSTECH: If we reduce greenhouse gas emissions significantly, we will see sea ice remaining in months other than September, but if we continue to increase greenhouse gas emissions as much as we are now, there will be almost no sea ice in the Arctic for three months from August to October, in the 2060s… I want to tell you that the effects, effects, and benefits of reducing greenhouse gases are much greater. If we go beyond carbon neutrality after the 2050s and move toward a scenario where carbon can be reduced from the atmosphere, the Arctic sea ice will naturally reappear in September.] When you first get behind the wheel, getting on and off the highway is incredibly scary. Getting off the highway is especially difficult. We can't just go straight ahead because it's difficult. "We're on the highway to climate hell," said UN Secretary-General Antonio Guterres. It's a warning that we need to take active measures now to get off the highway to hell in order to slow down climate change. Yoon Hyun-kyung ([email protected])