Aug 9 (Reuters) - Extreme heat waves that previously only
struck once every 50 years are now expected to happen once per
decade because of global warming, while downpours and droughts
have also become more frequent, a UN climate science report said
The report https://www.ipcc.ch/report/ar6/wg1 found that we
are already experiencing those effects of climate change, as the
planet has surpassed more than 1 degree Celsius in average
warming. Heat waves, droughts and torrential rains are only set
to become more frequent and extreme as the earth warms further.
It is the first time that the UN Intergovernmental Panel on
Climate Change (IPCC) has quantified the likelihood of these
extreme events in a wide variety of scenarios.
The report found that once-in-a-decade heavy rain events are
now 1.3 times more likely and 6.7% wetter, compared with the 50
years up to 1900 when major human-driven warming started to
Previously once-in-a-decade droughts could happen every five
or six years.
Scientists emphasized that these effects of climate change
are already here, with events like the heat wave in the U.S.
Pacific Northwest killing hundreds in June and Brazil currently
experiencing its worst drought in 91 years https://reut.rs/2X3Jsyh.
"The heat wave in Canada, fires in California, floods in
Germany, floods in China, droughts in central Brazil make it
very, very clear that climate extremes are having a very heavy
toll," said Paulo Artaxo, a lead author of the report and an
environmental physicist and the University of Sao Paulo.
(Graphic on warming planet https://tmsnrt.rs/3wcycMk)
The future looks even grimmer, with more warming meaning
more frequent extreme events.
Heat waves show stronger increases in frequency with warming
than all other extreme events. Twice in a century heat waves
could happen roughly every six years with 1.5 degrees Celsius of
warming, a level which the report says could be surpassed within
Should the world become 4 degrees Celsius hotter, as could
happen in a high-emissions scenario, those heat waves would
happen every one to two years.
Carolina Vera, another report author and a physical climate
scientist at University of Buenos Aires and Argentina's main
agency for science research (CONICET), said there is also an
increasing likelihood that multiple extreme weather events could
happen at the same time.
For example, extreme heat, drought and high winds -
conditions that could feed wildfires - are more likely to happen
at the same time.
The IPCC has a medium or high-level confidence that many
important agricultural regions around the world will see more
droughts or extreme rain. That includes parts of Argentina,
Paraguay, Bolivia and Brazil that are major growers of soybeans
and other global commodities.
"It is scary, sure, with the risk that fires, heat waves,
droughts will affect humans in the form of weather and food
insecurity, energy insecurity, water quality and health - mainly
in poor regions," said Jose Marengo, a climatologist at the
Brazilian Science Ministry's disaster monitoring center.
Marengo was a review editor for the IPCC report's chapter on
human influence on the climate system.
For example, regions that are already prone to drought are
likely to experience them more frequently, including in the
Mediterranean, southern Australia, and western North America,
said Friederike Otto, IPCC author and climatologist at
University of Oxford.
Increased frequency of drought and heavy rain also are not
mutually exclusive and are predicted in places like Southern
Africa, she said.
The projections on extreme weather events laid out in the
report reinforce the importance of curbing climate change to the
levels laid out in the Paris Agreement, scientists said.
"If we stabilize at 1.5 degrees, we can stop them from
getting much worse," Otto said.
(Reporting by Jake Spring in Brasilia; Additional reporting by
Nina Chestney in London and Andrea Januta in Guerneville,
California; Editing by Lisa Shumaker)