What does it mean that global warming exceeds 1.5 degrees? UN report: Extreme weather, sea level rise, ecological destruction and disease

CNN said on Oct. 31 that leaders attending the Group of 20 summit had reached an agreement to commit to "meaningful and effective" measures to achieve the goal of "limiting global warming to 1.5 degrees Celsius." Why emphasize this seemingly inconspicuous "1.5 degrees Celsius"? What exactly does it mean that global warming exceeds this limit?

CNN said 1.5 degrees Celsius was the standard established by the 2015 Paris Agreement. Under the Paris Agreement, states parties should limit global average warming to 2 degrees Celsius above pre-industrial levels and strive to limit them to 1.5 degrees Celsius. Since the beginning of the industrial revolution in human society, the emission of greenhouse gases such as carbon dioxide has soared, resulting in a rapid increase in global temperatures. Using pre-Industrial Revolution levels as a baseline, "the average temperature on earth today has warmed by about 1.3 degrees Celsius, very close to the critical warming threshold of 1.5 degrees Celsius," which many scientists believe could lead to severe climate change effects.

Scientists define "natural carbon dioxide levels" as the amount of carbon dioxide in the atmosphere before the Industrial Revolution, which was about 0.028% (280 ppm), a value that has now increased to 410 ppm with the use of large quantities of fossil fuels. "At the current rate of fossil fuel consumption, we will reach twice the amount of pre-industrial atmospheric carbon dioxide in just a few decades."

According to the BBC, global temperatures have risen faster than ever before due to the massive emissions of greenhouse gases such as carbon dioxide caused by human activities since the Industrial Revolution. According to the World Meteorological Organization, the planet has not warmed up to more than 2.5 degrees Celsius overall in 3 million years, but according to today's trend, global temperatures will be 3-5 degrees Celsius higher than pre-industrial levels by 2100, which will lead to "catastrophic consequences". The United Nations Intergovernmental Panel on Climate Change has also produced a thematic report on the climate impact of global temperature rises, listing the impacts of global warming.

The report shows that the primary impact of global warming is the accelerated melting of sea ice and the ice sheets of Greenland and Antarctica. Statistics show that the global ice sheet area is now reduced by about 13% every decade. This negative impact has manifested itself in places like Alaska, causing the death of large numbers of fish and other animals and frequent flooding along the coast. With the infusion of large amounts of glacial meltwater into the ocean, global sea levels have risen significantly. If global warming is limited to 1.5 degrees Celsius, global sea levels will rise by 26-77 centimeters, about 10 centimeters lower than the sea-level rise caused by global warming of 2 degrees Celsius. This means that as many as 10 million people will be protected from the effects of sea intrusion, flooding and damage to infrastructure. The Copenhagen Accords, signed in 2009, set a target of controlling global warming by 2 degrees Celsius. But many island nations argue that the goal of controlling a 2-degree Celsius warming is not enough to avoid the risk of them being submerged by rising sea levels.

At the same time, global warming has also caused serious impacts on the ecology of nature. If global warming rises by 1.5 degrees Celsius, about 6 percent of the 105,000 species studied, 8 percent of plants and 4 percent of vertebrates will lose their suitable living environment, and if global warming is 2 degrees, the corresponding affected will include 18 percent of insects, 16 percent of plants and 8 percent of vertebrates, the report said. The resulting climate change will also lead to degradation of high-latitude tundra and northern forests, and increased carbon dioxide concentrations will lead to ocean acidification, affecting the growth, development and even survival of marine life, threatening large biological populations from algae to fish.

In addition, global warming will lead to frequent or even simultaneous occurrence of extreme events such as heat waves and droughts. Higher temperatures will lead to more cases of insect-borne diseases and malaria, diarrhoea, heat stress, heart defects and malnutrition. Rising carbon dioxide levels have a negative impact on the nutritional value of crops such as rice, and the climate crisis has reduced crop yields and affected global food supplies. As insects such as bees and butterflies are drastically reduced due to the climate crisis, it means that crops that rely on them to spread pollen are also in crisis.

The report concludes that efforts should be made to limit global warming to 1.5 degrees Celsius, as this small gap is key to life and death in some regions.

Global Times reporter Chenyang

Editor/Ma Xiaoqing