Los Angeles – The city of Los Angeles is collaborating with scientists from the University of Southern California to test different ways of reducing urban heat. Strategies include cool roofs and reflective sidewalks.

The mayor of Los Angeles Eric Garcetti has pledged to reduce the average temperature in the metropolis by 1.5 degrees Celsius over the next 20 years. But Garcetti has his work cut out for him. As the LA Times reported, climate models suggest that by 2050, the temperature in downtown LA will exceed 35 degrees 22 days per year. In 1990, only six days were that hot.

To accomplish what many fear is the impossible, Garcetti’s office is collaborating with scientists from the University of Southern California (USC) to test different ways of counteracting the heat island effect, which makes cities a few degrees warmer than the rural areas that surround them.

One strategy is to replace the city’s asphalt streets and sidewalks with high-tech materials that reflect more sunlight and stay cooler during the day and night. According to the LA Times, tests indicate that these can be to 6 degrees cooler than regular pavement in the mid-afternoon. Another option is the widespread use of cool roofs, which could reduce the city’s temperature by as much as 1 degree.

But as USC environmental engineer George Ban-Weiss warns, it’s unlikely that one single strategy will be the most effective option for all neighbourhoods. “The heat island effect is a regional phenomenon, and the way you choose your mitigation strategy could vary block to block.”

For example, adding cool roofs in an area with no tree cover would be less effective than planting more trees. Likewise, reflective pavements in an area with plenty of trees won’t reduce temperatures because the sidewalks don’t receive much sunlight to begin with, explains the article.

The city hopes that by 2019 it will have a better idea if its goal of lowering the temperature by 1.5 C is realistic and the best way to achieve this.