Hotter yet poorer
Cities suffering from global warming and localised, urban heating may lose up to 11% of GDP by 2100.
LAST month, it was reported in The Star that Kuala Lumpur is hotter by up to 10°C compared to its neighbouring rural areas such as Hulu Langat (tinyurl.com/ star2heat).
The cause of this is the “urban heat island” effect, where a city full of concrete, tarred roads and vehicles cars belching hot exhaust (with insufficient green areas) becomes a “bubble” of heat.
Not only does this mean higher air-con bills. The extra heat is causing more water evaporation which then results in higher rainfall.
Given that cities have much more concrete (which don’t absorb water) rather than earth (which does), what then happens is that the heavier rainfall rushes off the hard surfaces into drains and rivers – which are then unable to cope with the surge of water, resulting in flash floods.
And that’s one reason why Kuala Lumpur floods seemingly occur after heavy rains.
Climate expert Prof Datuk Dr Azizan Abu Samah from Universiti Malaya said that the differences in temperatures between urban and rural areas are also widening by 0.4°C per decade.
This trend is also happening worldwide. AFP reports that under a dual onslaught of global warming and localised, urban heating, some of the world’s cities may be as much as 8°C warmer by 2100, researchers have warned.
Such a temperature spike can have dire consequences for the health of city-dwellers, robbing companies and industries of able workers, and put pressure on already strained natural resources such as water.
The projection is based on the worst-case-scenario assumption that emissions of planet-warming greenhouse gases continue to rise throughout the 21st century.
The top quarter of most populated cities, in this scenario, could see the mercury rise 7°C or more by century’s end, said a study in the journal Nature Climate Change.
For some, nearly 5°C of the total would be attributed to average global warming. The rest would be due to the so-called Urban Heat Island (UHI) effect, which occurs when cooling parks and lakes are replaced by heat-conducting concrete and asphalt – making cities warmer than their surrounding areas.
“The top 5% (of cities per population) could see increases in temperatures of about 8°C and larger,” study co-author Francisco Estrada of the Institute for Environmental Studies in the Netherlands told AFP.
Estrada and a team used different projections of average planetary warming, combined with the UHI effect and potential harms, to estimate the future costs of warming on cities.
The average median city, right in the middle of the range, stands to lose between 1.4 and 1.7% of GDP per year by 2050 and between 2.3 and 5.6% by 2100, they concluded.
“For the worst-off city, losses could reach up to 10.9% of GDP by 2100,” wrote the team.
UHI “significantly” increases city temperatures and economic losses from global warming, they added.
This meant that local actions to reduce UHI – such as planting more trees or cooling roofs and pavements, can make a big difference in limiting warming and minimising costs.
Cities cover only about 1% of earth’s surface but produce about 80% of gross world product and account for around 78% of energy consumed worldwide, said the researchers.
They produce more than 60% of global carbon dioxide emissions from burning coal, oil and gas for fuel.