It is a vicious cycle – as the climate grows hotter, demand for air conditioning is booming and that’s contributing to making the climate even hotter. Air conditioning accounts for about a fifth of the electricity used in buildings around the world. Much of that electricity comes from power stations that emit greenhouse gases and, to make matters worse, air conditioners can also leak hydrofluorocarbon refrigerants, greenhouse gases thousands of times more powerful than CO2 over a 20-year period. As the UK endures longer and more intense heatwaves, air conditioning here is becoming increasingly popular. By the end of the century, air conditioning could increase the UK’s power consumption by up to an estimated 15% during the summer. A more efficient air conditioner is being developed by Barocal, a spin-off company from Cambridge University. This is a heat pump that does away with conventional refrigerants and uses solid materials to release or absorb heat at different pressures as they change volume. The materials are more efficient than liquid refrigerants, cheap and non-toxic, and the heat pumps can be used for either cooling or heating, helping solve two needs in one go.