Best get used to it: Korea's summers will grow hotter through 2100

At around noon on Thursday, intense sunlight was beating down on Seoul Plaza's open grass field in Jung District, central Seoul. Suffocating heat radiated from the ground. Tourists clung to the thin shadows cast by the stone walls of Deoksu Palace. Children giggled as they dove into the water fountains gurgling cool water. 

The daily changing-of-the-guard ceremony at Gyeongbok Palace, scheduled for 2 p.m. that day, was canceled out of concern for the performers' safety. A heat stress index reading taken at Seoul Plaza registered 34 degrees Celsius (93 degrees Fahrenheit). The index quantifies a person's experience of strain caused by heat; at 33 degrees or above, even resting or sitting is evaluated as having a high risk of heat stress impact.

Outdoor sports have gone on alert. KBO, the national baseball organization, said Thursday that, following an emergency committee meeting with the general managers of all 10 clubs on heat wave measures, it would cancel all 15 games scheduled to be played at five stadiums across the country from Friday to Sunday. 

This brings the total number of games canceled this season due to the heat wave to 30. Earlier, the KBO had canceled all KBO League and Futures League games scheduled for Wednesday and Thursday. The cancellations follow the collapse of a 23-year-old spectator at a KBO game in Incheon on Tuesday. The spectator was reportedly dehydrated and was experiencing low blood pressure brought on by the heat.

A national high school baseball tournament, dubbed "Bonghwangdaegi National High School Baseball Championship" (translated), that was set to open on Friday has also rearranged its games. Only morning games will be played on opening day, with additional reserve days secured for each stadium.

Extreme heat is forecast to continue and become more frequent. 

The Korea Meteorological Administration (KMA) released an analysis Thursday, based on standard climate change scenarios, of current heat stress conditions during outdoor work in summer — from June through August — and future projections through 2100.

It found that the nationwide average summer heat stress index, currently 26.9 degrees Celsius, is projected to rise to between 29.5 and 33.2 degrees Celsius in the latter half of the 21st century, from 2081 to 2100. If the world sharply cuts greenhouse gas emissions, the increase would be smaller, about 2.6 degrees Celsius (4.7 degrees Fahrenheit). But if emissions keep rising at current rates, the index could jump by as much as 6.3 degrees.

"In the future, summer temperatures are expected to rise due to climate change, and particularly under the high-carbon scenario, the likelihood of heat stress occurring during outdoor work is expected to increase significantly," KMA official Lee Mi-sun said.

Notably, the number of days where heat stress can occur even while sitting or resting outdoors without any work — days with a heat stress index of 33 degrees Celsius or above — has increased markedly. Even with carbon reduction efforts, the number of days with a heat stress index of 33 or above is projected to rise just over 10-fold, from the current 1.8 days to 19.2 days in the latter half of the 21st century.

Without carbon reduction efforts, that figure could surge as much as nearly 30-fold, with severe heat stress exposure occurring on more than 51 days — meaning that even simply sitting outside could be uncomfortable due to heat throughout the entire summer. In the greater Seoul area, the number of such days is projected to rise to as many as 54.5 under the high-carbon scenario.

"In countries like Japan, outdoor activities are recommended to be suspended when the heat stress index exceeds 33 degrees Celsius," KMA's climate science bureau official Shim Seong-bo said. "Areas like the western Seoul metropolitan area, which are close to the sea and have higher humidity, showed a larger increase in the summer heat stress index than other regions."

BY CHON KWON-PIL [lee.jian@joongang.co.kr]