Global historical population exposure to heating and cooling degree days

The interplay between population growth and climate warming is reshaping human exposure to temperature extremes worldwide, yet how this composite effect varies across regions and income groups remains insufficiently quantified. Here, we examine whether global climate warming, in combination with population redistribution, is shifting the balance between heating and cooling demand, and how this transition varies across countries with different socioeconomic conditions. By integrating gridded population data with long-term changes in cooling and heating degree days, we assess population exposure to heat and cold at global and regional scales. Combining population distribution with degree-days changes, we find that the global balance of temperature-related demand is shifting from heating toward relatively greater cooling demand. Notably, low- and lower-middle-income countries, which have relatively limited resilience to heat stress, face greater cooling demand challenges and account for 63.65% of global cooling-related population exposure, which has increased by 31.24% over the past four decades. In contrast, high and upper-middle-income countries, which are more resilient, account for 90.69% of global heating-related population exposure, growing at a rate of 22.29%. Our findings highlight pronounced inequalities in population exposure to temperature extremes, provide a global assessment of the shifting balance between heating and cooling demand, and offer insights relevant to climate adaptation and public health policy development.