Washington Post
- Adam Taylor | Harry Stevens
How much warming can the world bear?
That question is one of the fundamental issues in dispute at the ongoing
U.N. climate change summit, known as COP26, in Glasgow, Scotland.
Here’s what different levels of warming would look like, and how
global temperature targets have been set.
Six years ago, when countries came together in Paris for the COP21
summit, at which the Paris climate accord was shaped, they committed
to limit the global average temperature rise to well below 2 degrees
Celsius (3.6 degrees Fahrenheit) above preindustrial levels.
However,
while the 2015 agreement set 2C as the minimum, it included language
that suggested countries should push for a more ambitious goal: 1.5C.
A preliminary draft of the COP26 agreement
released Wednesday “reaffirms”
the Paris agreement’s goal: limiting warming to well below 2C and
pursuing a target of 1.5C. But it does not commit to meeting the 1.5C
threshold.
The difference between the two targets may seem small, but they
represent vastly different levels of effort for countries seeking to
limit their carbon footprints, and strikingly divergent outcomes for
the planet.
Some experts doubt that 1.5C remains achievable. Limiting warming to
1.5C “will be very difficult,” Microsoft founder and philanthropist
Bill Gates told U.K. lawmaker Jeremy Hunt in
a conversation hosted by the think tank Policy Exchange
last week.
Evidence shows that the two targets also represent different scenarios
for the climate’s impact on human life.
A study released Tuesday by
the U.K. Met Office, Britain’s national weather service,
found that 1 billion people
could face heat stress, a potentially fatal combination of heat and
humidity, if temperatures rise by 2C.
“The higher the level of warming, the more severe and widespread the
risks to people’s lives, but it is still possible to avoid these
higher risks if we act now,” said Richard Betts, one of the leaders of
the project.
Tuvalu's foreign minister gave a speech to COP26 on Nov. 8, standing in the ocean to show how his Pacific island nation is on the front line of climate change. (Reuters)
How did the world agree upon a 2C target?
When world leaders came together in Paris in 2015, they were
looking to reverse a long period of international inaction after
the widely perceived failures of the 1992 Kyoto Protocol and the
2009 Copenhagen Accord.
The latter had included nonbinding language that referenced “the
scientific view that the increase in global temperature should
be below 2 degrees Celsius.”
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During his visit to the COP26 climate summit in Glasgow, Scotland, Rep. Garret Graves (R-La.) explained how he talks to his party about the climate crisis. (Casey Silvestri/The Washington Post) |
Nearly 200 countries signed onto the agreement in Paris, which
was adopted in 2015 and took effect in 2016.
Under the accord,
countries would set their own emission reduction targets and
plans to reach those targets, but agreed to the long-term
temperature goal to limit “the increase in the global average
temperature to well below 2C above preindustrial levels.”
Countries would also pursue “efforts to limit the temperature
increase to 1.5C above preindustrial levels, recognizing that
this would significantly reduce the risks and impacts of climate
change,” according to the text.
The two targets, one firm and one aspirational, represented a
fierce policy debate.
Developing countries had been pushing to
set a rise of 1.5C as a target for years. Small island nations
were often the most vocal in their support, pointing to the
existential threat they faced.
Around the world, many adopted the slogan
“1.5 to stay alive.”
Has there been a movement toward a 1.5C target?
The Paris agreement represented a significant shift. More than
100 countries expressed support for a target of 1.5C, including
for the first time some major emitters.
Notably, the United
States got on board, joining a group called the “High Ambition
Coalition” founded by the Marshall Islands in 2014.
Scientific pressure played a role in the change. In a paper
published during COP21, Nature Geoscience stated that “no
scientific assessment has clearly justified or defended the 2° C
target as a safe level of warming, and indeed, this is not a
problem that science alone can address.”
But there remained some skepticism, with oil and gas producing
Saudi Arabia among the countries
pushing back on the more ambitious targets. Some officials argued that countries should keep to the less
ambitious target so that countries were not set up for failure.
Former president Donald Trump pulled the United States out of
the Paris agreement and promoted the use of fossil fuels.
But,
under President Biden the United States has not only rejoined
that agreement but also the group of nations that say that 1.5C
should be the standard.
However, the
U.S. leader has also privately questioned
whether even the 2C goal is attainable if top emitters do not
stick to their pledges. And while the draft released from COP26
on Wednesday did include new terms, it did not set 1.5C as a
target.
What does the science say about the difference between 1.5C and 2C
warming?
The Intergovernmental Panel on Climate Change (IPCC), a
U.N. body responsible for assessing the scientific
research on climate change, has warned that even an
increase of 1.5C of global warming would result in
significant differences, with increased heat waves and
short cold seasons.
At 2C, however, the changes will be more profound. “With
every additional increment of global warming, changes in
extremes continue to become larger,” the IPCC wrote in a
report released earlier this year that evaluated more than
14,000 papers.
The
IPCC has found that an extreme heat event
that would have occurred once per decade in a climate
without human influence, would happen 4.1 times a decade
at 1.5C of warming. It would occur 5.6 times at 2C. Other
events such as heavy precipitation or drought would also
increase.
The IPCC also noted that it was very likely that the
relative sea level will continue to rise throughout the
21st century and beyond, and the level it rises will be
affected significantly by the level of climate change.
If
temperatures are confined to an increase of 1.5C, over the
next 2000 years sea levels could rise by as much as 10
feet, but it could be double that if temperatures grow by
2C, the IPCC research found, and potentially worse if ice
sheets in Antarctica become destabilized.
Individual papers have spelled out similar scenarios,
though they also show that increases of over 2C could be
far worse. The Met Office study
released on Tuesday found
that while a 2C increase would result in the number of
people living in areas affected by extreme heat stress
rising from 68 million today to 1 billion, a 4C rise could
see nearly half of the world’s population living in those
areas.
What are we at now?
A Washington Post analysis of multiple data sets
has found that Earth
has already warmed more than 1 degree Celsius on average
over the past century. Some places may already have seen
rises of 2C.
In their latest report, the IPCC estimated that under the
current scenario, the world would likely hit the 1.5C
threshold by 2040. Under the most optimistic scenario
presented in the report, global temperatures would reach
1.5C by the middle of the century and then drop back down
as emissions were cut further, potentially avoiding some
of the worst outcomes.
Under the worst scenario envisaged by the IPCC, the best
estimate was that the world will likely see a rise of 4.4C
by the end of the century — with an extreme impact on life
on Earth.
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