'완전 소멸' 선고받은 지구…심상치 않은 징후 포착 [와이즈픽]

Average temperature: 15 degrees Celsius. Oxygen concentration: 21%. Seawater salinity: 3.4%. The Earth is remarkably self-regulating. Through its self-regulating function, it has maintained optimal conditions for life. If this self-regulation collapses, catastrophe will ensue. A mere 1% increase in oxygen concentration leads to a 70% increase in wildfires caused by lightning strikes. A 6% salinity in seawater would lead to the extinction of most marine life. Humanity would be helpless in the face of disaster. Therefore, we must act before it strikes. Sea ice, where polar bears live. It expands in winter and shrinks in summer, reaching its smallest size in September. The problem is that global warming prevents it from recovering properly. This means that the total ice surface area is gradually shrinking. The rate at which solar radiation is reflected is called "albedo." We can gauge the stability of Earth's climate through albedo. This is how it works. As global warming reduces ice cover, the solar energy that's not reflected but absorbed increases the temperature of the Arctic Ocean. The warmed ocean water then melts the ice. With more ice loss, the albedo decreases further. The Earth is caught in a vicious cycle, retaining heat. Have you ever wondered why winters are getting colder, even though the Earth is getting warmer? It's due to a disruption in the jet stream, which carries 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. When the Arctic temperature rises and the jet stream weakens, cold air descends. This is easy to understand, like when you slow down a hula hoop, you fall. This January, one of the causes of the unusual waves that struck East Asia, including the Korean Peninsula, was a weakening of the jet stream. When discussing the Arctic, we can't leave out the topic of sea level. Will rising Arctic temperatures lead to rising sea levels? It's commonly believed that melting Arctic ice will cause sea levels to rise, but this is half true and half false. The melting of Arctic sea ice means that ocean temperatures have risen. Rising water temperatures cause sea water to thermally expand. Since its volume increases, sea levels will rise to some extent. This is simply the effect of rising water temperatures. The melting of ice floating on the ocean doesn't immediately lead to a noticeable rise in sea level. Just like melting ice in iced coffee doesn't cause the coffee to overflow. It's the same principle. Let's pause here. It's not the icebergs on the Arctic ocean, but the glaciers that cover the land that directly impact sea level rise. This video was recently filmed in Alaska, USA. This is what happened when glaciers melted, causing lake levels to rise. The rate at which glaciers are melting is alarming. The remains of long-lost climbers in the Alps are being discovered one after another thanks to the melting ice. Let's return to the Arctic. Arctic sea ice is linked not only to polar bears, but also to human habitats. As the icebergs that act as a shield melt, wind and waves intensify, increasing erosion. Polar ice researcher Robbie Mallett estimates that approximately 4.5 million people will be severely affected by erosion. Polar bears aren't just losing their habitat. Due to changes in their DNA, they could disappear from the face of the earth. Polar bears have maintained genetic diversity by migrating and mating with other species. This has increased their ability to adapt to climate change, reduced their risk of disease, and enhanced their survival. As ice melts and migration becomes impossible, the likelihood of interbreeding—that is, mating between members of the same species—has increased significantly. A decrease in genetic diversity can lead to decreased survival and reproductive capacity, ultimately leading to extinction. According to the U.S. National Snow and Ice Data Center (NSIDC), the area of ​​summer icebergs in the 2010s decreased by approximately 40% compared to the 1980s. In terms of volume, it has decreased by a staggering 70%. The Earth has experienced similar events in the past. Experts are focusing on the "last interglacial" 120,000 years ago. According to Swedish climate scientists, during that time, when the climate was similar to our current climate, all the Arctic sea ice melted. Another interglacial. The same thing is happening again. [David Barber / Director, Earth, Environment, and Resources Institute, University of Manitoba, Canada: In the near future, the Northern Hemisphere will be ice-free in the summer. This is a truly significant change in the Earth system.] However, the cause of the ice melt is different from the past. Greenhouse gases, which cause global warming, are considered the primary culprit in melting the Arctic ice, rather than natural factors like solar or volcanic activity. Ther...