What do spraying sulphate aerosols into the atmosphere, fertilising the ocean with iron and building giant mirrors in space have in common? They are all large-scale climate engineering plans aimed at keeping our planet cool. They are also risky, have questionable effectiveness and are likely to alter climate systems in unexpected ways - basically they could make everything worse, instead of better.
Painting cities white, however, has just been proven to work.
The research, led by Sonia Seneviratne of ETH Zurich with researchers from UNSW, University of Tasmania, CSIRO and Pacific Northwest National Laboratory in the US, showed modifications like lightening buildings, roads and other infrastructure in high population areas reduced temperatures by 2 to 3°C.
"Extreme temperatures are where human and natural systems are most vulnerable. Changing the radiative properties of land helps address this issue with fewer side effects," said Director of the ARC Centre of Excellence for Climate Extremes, Prof Andy Pitman.
"This research suggests that by taking a regional approach, at least in temperate zones, policy and investment decisions can be pragmatically and affordably focused on areas of greatest need."
We're not quite ready to crack open the Dulux, though.
Professor Sonia Seneviratne points out regional land-based climate engineering can be effective, but we need to consider competing demands for land use - like food production, biodiversity, carbon uptake, recreational areas and "much more, before putting it into effect."
"We must remember land-based climate engineering is not a silver bullet, it is just one part of a possible climate solution, and it would have no effects on global mean warming or ocean acidification."
"There are still important moral, economic and practical imperatives to consider that mean mitigation and adaption should still remain at the forefront of our approach to dealing with global warming."