Kuala Lumpur - A fifth
of the world's major cities will face "unknown" climate
conditions by 2050, researchers warned on Wednesday, as rising
temperatures heighten the risks of drought and flooding.
Climate scientists at the Crowther Lab, a research group
based at ETH Zurich, a science and technology university,
analysed 520 cities across the world, including all capitals and
most urban centres with a population of more than 1 million.
Looking at current climate conditions in these cities -
including precipitation and seasonal data - scientists projected
what would happen as temperatures rise another half degree, to
near the lower 1.5 degree Celsius target set in the 2015 Paris
Agreement on climate change.
It showed that 22% of the cities will experience
unprecedented climate conditions by 2050, such as more intense
dry and monsoon seasons, said Jean Francis-Bastin, the lead
author of the report.
"It is a change in climate conditions that is likely to
increase the risk of flooding and extreme drought," he told the
Thomson Reuters Foundation. "It is unknown conditions."
Almost 70% of the world's population is expected to be
living in urban areas by 2050, according to the United Nations.
But many cities, especially in poorer nations, face
significant challenges, including large and growing slum
populations that lack basic services and are increasingly at
risk from climate disasters.
Under the Paris Agreement, which has been ratified by 185
countries, governments have pledged to keep global warming "well
below" 2C (3.6F) above pre-industrial times and strive for a
lower limit of 1.5C.
Limiting global temperature rise to 1.5C would avoid
economic losses of $12 trillion by 2050, according to the United
Nations.
Crowther Lab scientists said their study, published in the
journal PLOS ONE, was the first global analysis of the likely
shifts in climate conditions in major cities as a result of
global warming.
It showed that 77% of the cities it looked at will
experience a striking change in climate conditions by 2050.
Across the northern hemisphere, many cities in 30 years time
could resemble places that are over 1,000 km (620 miles) further
south towards the equator, said the study, which projected
conditions if current plans to cut climate-changing emissions go
ahead.
In Europe, cities will warm by an average of about 2.5
degrees Celsius across the year, but summers and winters could
be 3.5C and 4.7C warmer, respectively, Francis-Bastin said.
Globally, temperatures are likely to be 2.4C warmer on
average - enough to kill nearly every coral reef and soar past
targets set out in the Paris Agreement.
Under the study scenario, London's climate in 2050 could be
similar to Barcelona's current climate, with Madrid feeling more
like Marrakesh, Seattle more like San Francisco, and Tokyo more
like Changsha in central China, it said.
Cities in tropical regions, which are likely to see the
strongest impacts from climate change, will experience smaller
changes in average temperature, the study said.
But they will see shifts in rainfall patterns, leading to
more severe flooding and droughts, researchers said.
Of the 22% of cities that will see 'unprecedented' climate
shifts, 64% are located in the tropics and include Kuala Lumpur,
Jakarta, Rangoon and Singapore, researchers said.
The study may help cities modify their planning to combat
specific climate risks, Francis-Bastin said. He said he also
hoped it would help persuade people to change their lifestyles
to cut planet-warming emissions and cut the risks.
"We definitely and very quickly need to change the way we
are living on the planet. Otherwise we are just going to have
more and more droughts, flooding and extreme events," he said.