TOKYO -- The Earth's mean temperature is likely to rise 1.5 degrees Celsius from preindustrial revolution levels by as early as 2030, triggering a 77-centimeter surge in sea levels by 2100 and killing up to 90 percent of coral reefs, according to a special report released by a United Nations body of climate researchers monitoring global warming and recommending countermeasures.
The report, compiled by the Intergovernmental Panel on Climate Change (IPCC) and announced on Oct. 8, also claims that capping the temperature hike at 1.5 degrees, lower than the 2.0 degree ceiling set by the 2015 Paris Agreement to fight climate change, will cut risks from climate change, including a reduction of some 10 million people among those facing risks from sea level rises.
According to the IPCC's Fifth Assessment Report finalized in 2014 and other literature, it is presumed that human activities, such as the emission of greenhouse gases through the burning of fossil fuels, have already caused the planet's mean temperature to rise about 1 degree Celsius above pre-industrial levels. The report that was finalized at the 48th IPCC session that took place in Incheon, South Korea Oct. 1-6 concluded that the temperature rise is likely to reach upwards of 1.5 degrees between 2030 and 2052 if it continues to increase at the current rate.
To limit global warming to 1.5 degrees, carbon dioxide emissions from human activities have to reach "net zero" around 2050 and achieve "decarbonization," and the use of coal in electricity production has to be reduced to "close to 0 percent," according to the study.
The report also said that mean sea level rise is likely to be between 26 and 77 centimeters by 2100 with a 1.5-degree hike, down 4 to 16 centimeters estimated to occur from an increase of 2.0 degrees. The disappearance of sea ice in the Arctic Ocean during summer would happen once a century with a 1.5-degree rise, while the frequency would increase to once per decade if the global temperature goes up by 2.0 degrees.
The study reviewed the possibility of the loss of habitat for animals and plants. Of 105,000 species studied, 18 percent of insects, 16 percent of plants and 8 percent of vertebrates would lose at least half of the areas where they can survive if the temperature rises by 2.0 degrees, while those risks can be mitigated if the temperature hike is capped at 1.5 degrees. Coral reefs would become almost extinct if the global temperature rises as high as 2.0 degrees, but 10 to 30 percent may survive with a 1.5-degree hike.
"This report gives policymakers and practitioners the information they need to make decisions that tackle climate change while considering local context and people's needs," said Debra Roberts, co-chair of the IPCC Working Group II that addresses the impact of climate change. She emphasized such decisions are critical in ensuring a safe and sustainable world for everyone, both now and in the future. "The next few years are probably the most important in our society."
(Japanese original by Kazuhiro Igarashi, Science & Environment Department)