Low- and high-tech solutions for urban heat peril

By Richard Ingham ,AFP

BONN, Germany — Climatologists call it the ��urban heat island�� effect �X when a heat wave transforms a city into a furnace where citizens swelter, suffer or even die. The phenomenon is a major worry in hot countries where global warming will drive peak temperatures even higher in coming decades. Urban planners and researchers, gathering in a parallel conference to U.N. climate talks in Bonn, turned a spotlight on the problem on Wednesday. But they also pointed to an emerging arsenal to fight it, from planting trees to designing breeze-channeling buildings. The urban heat island derives from simple physics. Cities store heat from the sun and traffic in concrete and tarmac during the day, and release it at night. But in a heat wave, an infernal cycle starts up.

The night is not long enough for all the heat to dissipate, so at dawn the new day is already warm … and can only get warmer. Without cooling or respite, old or sick people are especially at risk. A heat wave that gripped Europe in 2003 killed more than 70,000 people, according to peer-reviewed research. ��Urban heat island is a big problem for us,�� said Catarina Freitas, head of sustainable environment management for Almada, a city south of the Portugese capital, Lisbon. The difference between central Almada and its outskirts can be a whopping 4 degrees Celsius (7.2 degrees Fahrenheit), she explained. ��In the summer of 2013, we were caught in a severe heat wave. We had 1,400 more deaths during this period compared to previous years … We had a nighttime temperature of 33 degrees �X we couldn’t cool down our bodies, it was a nightmare.�� Michael Boswell, a professor at California Polytechnic State University, said Los Angeles, a sprawling car-dependent city of 4 million people and few parks, has also found itself vulnerable. ��Currently, downtown LA experiences six days a year that exceed 95 Fahrenheit or 35 Celsius,�� he told AFP. ��By 2050 they anticipate 22 days �X and by 2100 they anticipate 54 days.�� So what can we do to roll back urban heat? ��The first thing that you can do is plant trees, to provide shade,�� said Ingrid Coninx at Wageningen University and Research Centre in the Netherlands. ��But when you plant trees you have to do it in the right way. If you prevent downward breeze from reaching the street, you could make things warmer and trap pollution.