Global warming will reach 1.5C threshold this decade -report
02/11/2023 17:26
*
New study published ahead of UN annual climate talks
*
Says Earth's climate more sensitive to emissions than
thought
*
Some scientists not convinced by new findings
By Gloria Dickie
LONDON, Nov 2 (Reuters) - Climate change is accelerating
and the world will cross the 1.5 degrees Celsius (2.7
Fahrenheit) warming threshold this decade, according to research
published on Thursday that scientists said should raise alarms
at this year's COP28 climate talks.
Countries pledged in the 2015 Paris Agreement to hold global
warming to within 1.5C above pre-industrial temperatures but the
new paper by a team of scientists, including from NASA and
Columbia University, adds to evidence suggesting that this goal
is already out of reach.
Most emissions scenarios under the United Nations
Intergovernmental Panel on Climate Change (IPCC) envision the
world breaching 1.5C during the 2030s.
"The 1.5C limit is deader than a doornail," said study
co-author James Hansen of Columbia University's Earth Institute
who was among the first scientists to alert the world in the
1980s to the climate-warming impact of greenhouse gases.
"The shortcoming of our scientific community is to not make
clear to the political leaders what the situation is," he said.
The world already has warmed by nearly 1.2C (2.2F) above
preindustrial temperatures.
The study has received mixed feedback from other climate
scientists. Some questioned its findings, with Michael Mann of
the University of Pennsylvania saying in a blog post that they
were "very much out of the mainstream".
The new report comes after months of extreme weather shocks
worldwide, from heatwaves in China to severe flooding in Libya,
with 2023 set to be the warmest year on record.
Countries will gather later this month in Dubai for the
annual U.N. climate summit to discuss global policy efforts to
rein in greenhouse gas emissions.
EARTH SENSITIVITY
The study's findings, published in the journal Oxford Open
Climate Change, result from two factors.
Scientists have underestimated how sensitive the Earth's
climate is to rising carbon dioxide levels. The IPCC has given a
best-guess estimate that the doubling of atmospheric carbon
dioxide levels would yield global warming of around 3C (5.4F).
A better understanding of ancient climate data - gleaned
from sources such as ice cores and tree rings - has resulted in
a higher estimate of around 4.8C (8.6F), the study said.
So far, atmospheric carbon dioxide concentrations have risen
from around 280 parts per million (ppm) in the preindustrial era
to about 417 ppm today.
Another factor cited by the report relates to China's
progress in cleaning up air pollution, caused mainly by sulphur
dioxide spewed from coal plants, alongside global efforts to
curb such emissions from shipping.
Cleaning the skies, while bringing health benefits and
saving lives, accelerates climate change. Aerosols scatter and
reflect solar radiation.
Pennsylvania's Mann took issue with the notion that
models have underestimated climate sensitivity, as well as with
the impact of declining sulphur dioxide emissions from shipping.
Others said the study was in line with other recent
research.
"Everything is accelerating," said climate scientist Klaus
Hubacek of the University of Gronigen.
Earlier this week, research published in the journal Nature
Climate Change suggested the world would need to reach net zero
emissions by 2034 for a 50% chance of containing warming to 1.5C
- far sooner than the global goal of 2050.
(Editing by Katy Daigle and Gareth Jones)
((Gloria.Dickie@thomsonreuters.com;))