With climate change exacerbating the heat-island effect, increasing urban temperatures and adding to heat-related deaths, cities like San Francisco have turned to innovative coating systems that reflect solar rays to cool temperatures and reduce energy use on cooling systems.
New research, led by ETH Zurich with support from the University of Tasmania, UNSW, CSIRO and the US Pacific Northwest National Laboratory has found that merely making buildings, roads and infrastructure lighter can help reduce urban temperatures by 2C to 3C.
The researchers aren’t talking about the weight of the buildings, but rather the colour. By coating infrastructure in lighter colours – ideally white – temperatures can be reduced. However, the researchers note that demand for land use for food production, carbon capture and biodiversity need to be considered before people get their paintbrushes out.
Unlike many other climate-engineering methods proposed to tackle climate change, many of these regional modifications have already been tested and proven to work. Critically, this method has fewer risks compared with injecting aerosols into the atmosphere.
“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.”
By contrast other proposed forms of large-scale climate engineering, such as spraying sulphate aerosols into the atmosphere, fertilising the ocean with iron and even building giant mirrors in space, have questionable effectiveness and are likely to alter climate systems in unexpected ways. They could make situations worse for some countries.
The researchers gained their results by modelling how changing only the radiative properties of agricultural land and high population areas across North America, Europe and Asia would impact average temperatures, extreme temperatures and precipitation.
The results showed small impacts on average temperatures, little change in precipitation — except in Asia — but significant reductions in extreme temperatures.
“Regional land-based climate engineering can be effective but we need to consider competing demands for land use, for instance for food production, biodiversity, carbon uptake, recreational areas and much more before putting it into effect,” said lead author Prof Sonia Seneviratne of ETH Zurich.
“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.”