The most immediate feeling of the effect of global warming on people will likely be the unbearable long hot days of summer. The Joule-Thompson compression-expansion based air conditioner will be desperately needed in this situation. However, their use intensifies the warming effect especially in urban areas due to greenhouse gas coolants, energy consumption, CO2 emissions and urban heat island effect. Recently, the common mineral Barite, barium sulphate, demonstrated passive radiative cooling, providing an environmental temperature reduction of 4-10 °C, a promising materials technology for confronting the urban warming effect of climate change, an eco-friendly cooling alternative to air conditioners, now that’s really cool! See full story at Advanced Science News.