If carbon emissions are not reduced, by the end of this century the number of days in summer when people are exposed to extreme heat stress even when merely resting outdoors will increase to nearly 29 times the current level. The warning is that, at this rate, heat waves could arrive that threaten not only outdoor labor but everyday life as a whole.

According to an analysis released on the 6th by the Korea Meteorological Administration that examined future summer (June~August) wet-bulb globe temperature (WBGT) under standard climate change scenarios, in a high-carbon scenario where greenhouse gas reductions are insufficient, the average summer WBGT jumps from the current 26.9 degrees to 33.2 degrees by the end of the century (2081~2100). Even under a low-carbon scenario with aggressive greenhouse gas cuts, it rises to 29.5 degrees.

The WBGT is ‘an international standard that evaluates heat stress risk from heat waves by reflecting factors such as air temperature and humidity’. The higher the number, the greater the likelihood of experiencing heat stress and heat illness while working. For example, at a WBGT of 25 degrees, the risk of heat stress arises only during very strenuous work, but once it exceeds 33 degrees, heat stress can occur even while resting or merely sitting.

Heat stress refers to the load placed on the human body when activity in high temperatures keeps body temperature above the normal range. Heat stress can cause dizziness, fatigue, lethargy, cramps, and loss of consciousness.

The Korea Meteorological Administration projected particularly high WBGT values in more humid areas such as Jeju, Gwangju in South Jeolla, and along the west and south coasts compared with other regions. Under the high-carbon scenario, the average summer WBGT in these areas exceeds 34 degrees by the end of the century, indicating a sharply elevated heat stress risk during outdoor work.

The largest increases in WBGT were in western Greater Seoul and western South Chungcheong. In the capital region, values rise to as high as 33.7 degrees by the end of the century, and in South Chungcheong to 33.4 degrees, increases of up to 6.6 degrees and 6.4 degrees, respectively, from today.

The rise in WBGT is not confined to specific areas. At present, 92.8% of basic local governments nationwide have an average summer WBGT below 28 degrees, but over time the number of areas exceeding 30 degrees surges. In particular, under the high-carbon scenario, the share of jurisdictions with an average summer WBGT of 33 degrees or higher increases to 66.4% of the total.

The number of days with a WBGT of 33 degrees or higher also grows sharply. Currently it averages only 1.8 days in summer, but by the end of the century it rises to 19.2 days even under the low-carbon scenario, more than tenfold. Under the high-carbon scenario, it reaches 51.6 days, appearing 28.7 times more often than now.

Lee Mi-seon, head of the Korea Meteorological Administration, said, “In the future, summer temperatures will rise due to climate change, and the likelihood of heat stress is expected to increase substantially.”