Hot­ter yet poorer

Cities suf­fer­ing from global warm­ing and lo­calised, ur­ban heat­ing may lose up to 11% of GDP by 2100.

The Star Malaysia - Star2 - - Ecowatch -

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.

— AFP

A heat­stroke vic­tim in Karachi, Pak­istan dur­ing a heat­wave in June 23, 2015. The death toll from that one hot day in south­ern Pak­istan ex­ceeded 450.

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