Asian Megacity Heat Stress Under Future Climate Scenarios: Impact of Air-Conditioning Feedbacks

Future heat stress under six future global warming (ΔT_GW) scenarios in an Asian megacity (Osaka) is estimated using a regional climate model with an urban canopy and air-conditioning (AC). An urban heat 'stress' island is projected in all six scenarios (ΔT_GW = +0.5 to +3.0 ºC in 0.5 ºC steps; based on IPCC RCP8.5). Under ΔT_GW = +3.0 ºC conditions, people outdoors experience 'extreme heat stress', which could result in dangerously high increases in human body core temperature. AC-induced feedback increases heat stress roughly linearly as ΔT_GW increase, reaching 0.6 ºC (or 12% of heat stress increase). As this increase is similar to current heat island mitigation techniques, this feedback needs to be considered in urban climate projections, especially where AC use is large.