It is generally believed that global warming drives an increase in heatwaves, but these changes vary regionally. Projected trends of heatwaves and comparisons between observed and projected heatwave trends are poorly understood. We selected multiple characteristics of global heatwave events, including indicators on heat-related health impacts under historical and future scenarios from the NASA Earth Exchange/Global Daily Downscaled Projections (NEX-GDDP) dataset. We quantified the trends in the frequency, intensity, duration and peak temperature of heatwave events and identified heatwave hotspots that respond dramatically to radiative forcing. Future simulations suggest a four-fold increase in the duration of heatwaves by 2050s, spatially concentrated in central Africa, northern South America and Southeast Asia, and the maximum duration of single heatwave event will be up to 44 days under a high emission scenario. Accelerated increasing trends are also detected in intensity, total duration and temperature of heatwaves with up to 2-fold, 8-fold and 9-fold larger than the trends of the baseline period under the high emission scenario. Considering socioeconomic exposure to extreme heatwaves, we identified some hotspot areas in western Europe, eastern North America and northern China that will face greater potential risks in the coming future and therefore need to urgently strengthen their adaptation capacity.