Study
reveals greater climate impacts of 2C temperature rise
Analysis
of difference between 1.5C and 2C of warming finds extra 0.5C would
mean longer heatwaves, greater droughts and threats to crops and
coral reefs
Damian
Carrington
Thursday
21 April 2016 13.00 BST
A difference of half
a degree centigrade may be barely noticeable day to day, but the
difference between 1.5C and 2C of global warming is a shift into a
new, more dangerous climate regime, according to the first
comprehensive analysis of the issue.
The scientists found
the additional 0.5C would lead to longer heatwaves, greater droughts
and, in the tropics, reduced crop yield and all coral reefs being put
in grave danger.
The global climate
change deal agreed in Paris in December pledged to “hold the
increase in the global average temperature to well below 2C above
pre-industrial levels and pursue efforts to limit the temperature
increase to 1.5C.” Vulnerable countries, such as low-lying islands,
have warned that 2C of climate change would wipe their nations from
the map.
Understanding the
different impacts from 1.5C or 2C of warming has been made more
urgent by the recent run of record temperatures, with 2014 and 2015
breaking long-term records and recent months smashing previous highs.
In February, the global temperature was 1.34C above the average from
1951-1980, according to Nasa data.
World's scientists
to join forces on major 1.5C climate change report
Read more
The new research was
published in the journal Earth System Dynamics, and lead author Carl
Schleussner, a scientific adviser at Climate Analytics in Germany,
said: “We analysed the climate models used by the Intergovernmental
Panel on Climate Change [and] considered 11 different indicators
including extreme weather events, water availability, crop yields,
coral reef degradation and sea-level rise. We found significant
differences [between 1.5C and 2C] for all the impacts we considered.”
The researchers
found: “For heat-related extremes, the additional 0.5C marks the
difference between events at the upper limit of present-day natural
variability and a new climate regime, particularly in tropical
regions.”
The analysis found
that regional dry spells increased by 7% with 1.5C of warming but by
11% with 2C, while sea level rises by 10cm more in the hotter
scenario. Some regions would be more affected than others with, for
example, water availability in the Mediterranean falling by 9% under
1.5C of warming but 17% under 2C.
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The research found
crop yields might rise in some high-latitude regions, but “tropical
regions like west Africa, south-east Asia, as well as central and
northern South America are projected to face substantial local yield
reductions, particularly for wheat and maize.”
Coral reefs, which
provide vital nurseries for many fish on which people rely on for
food, would be particularly affected by an additional 0.5C of
warming. “In a [2C] scenario, virtually all tropical coral reefs
are projected to be at risk of severe degradation due to
temperature-induced bleaching from 2050 onwards.” This is reduced
to 70% by 2100 for the 1.5C scenario, the scientists found.
Jacob Schewe, one of
the research team and at the Potsdam Institute for Climate Impact
Research in Germany, said: “Some researchers have argued that there
is little difference in climate change impacts between 1.5C and 2C.
Indeed, it is necessary to account for natural variability, model
uncertainties, and other factors that can obscure the picture. We did
that in our study, and by focusing on key indicators at the regional
level, we clearly show that there are significant differences in
impacts.”
Prof Nigel Arnell,
at the University of Reading, UK, who was not involved in the
research, welcomed the new study: “This study demonstrates that the
impacts in 2100 are lower under a 1.5C world than under a 2C world
and that the difference is greater for some sectors than for others.
Impacts on heat extremes are most affected.
“The study also
shows that the rate of change over time is really important for
future impacts, so in order to really understand the differences
between a 1.5C and a 2C world we need to run more comprehensive
global climate models with lower rates of [warming] than used so far
to see how the climate system responds.”
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