[Many countries have vowed to slash emissions even faster. So far those promises exist mostly on paper, but if nations follow through, the world could potentially limit total warming to around 2 to 2.4 degrees Celsius by 2100.]
By Brad Plumer and Nadja Popovich
Today, thanks to rapid growth in
clean energy, humanity has started to bend the emissions curve. Current
policies put us on pace for roughly 3 degrees Celsius of
warming by 2100 — a better result, but still devastating.
Many countries have vowed to slash
emissions even faster. So far those promises exist mostly on paper, but if
nations follow through, the world could potentially limit total warming to
around 2 to 2.4 degrees Celsius by 2100.
Yet scientists and world leaders
increasingly say even that much warming is too risky. To hold global
temperature rise to a safer limit of 1.5 degrees Celsius, far
more drastic action is needed.
As world leaders gather in Glasgow
for a United
Nations climate summit next week, the focus will be on one crucial number:
How many degrees hotter will the Earth get? And how do we keep that number as
small as possible?
Humans have so far warmed the planet
1.1 degrees Celsius (2 degrees Fahrenheit) since preindustrial times, mainly by
burning coal, oil and gas for energy, and by cutting down forests, which help
absorb the planet-warming emissions created by fossil fuel use. Humanity is already
paying a high price: This year alone, blistering heat waves killed hundreds
of people in the Pacific Northwest, floods devastated Germany and China, and
wildfires raged out of control in Siberia, Turkey and California.
How much worse could things get?
To figure that out, scientists at Climate Action Tracker, a research
group, regularly scrutinize all the climate and energy policies that countries
have enacted worldwide. They then estimate the effect of these policies on
future greenhouse gas emissions and calculate how much of a temperature
increase the world can expect.
It’s a simple measure of progress
to date in combating climate change. And the data offers reasons for both hope
and alarm.
How Things Improved
In 2014, Climate Action Tracker estimated that
the world was on track for nearly 4 degrees Celsius of warming
by 2100, compared with preindustrial levels.
Warming of 4 degrees has long been
deemed a worst-case scenario. One assessment by
the World Bank explored the risks, such as cascading global crop failures, and
bluntly concluded that 4 degrees “simply must not be allowed to occur.”
This year, however, Climate Action
Tracker painted a more optimistic picture, because countries have started doing
more to restrain their emissions. Current policies put the world on pace for
roughly 2.9 degrees Celsius of warming by 2100. (That’s a best
estimate: the potential range is between 2.1 degrees and 3.9 degrees Celsius.)
The United Nations will release its
own analysis of global climate efforts Tuesday, though it has reached broadly
similar conclusions in the past.
“There has been a genuine shift
over the past decade,” said Niklas Höhne, a German climatologist and founding
partner of NewClimate Institute, which created the Climate Action Tracker. “You
can say that progress has been too slow, that it’s still not enough, and I
agree with all that. But we do see real movement.”
There are several reasons for the
improved outlook.
In 2015, 195 nations signed the
Paris climate agreement, which for the first time required every country to
submit a plan for curbing emissions. While the plans were voluntary, they helped
spur new actions: The European Union tightened
caps on industrial emissions. China and India ramped up renewable
energy. Egypt scaled
back subsidies for fossil fuels. Indonesia began
cracking down on illegal deforestation.
Along the way, there was
backsliding. The Trump administration rolled
back some major climate policies. Deforestation in Brazil surged under
President Jair Bolsonaro.
But, on the whole, countries are
doing more than they were a decade ago.
Just as importantly, clean energy
advanced far more quickly than predicted. A decade ago, solar panels, wind
turbines and electric vehicles were considered niche technologies, too
expensive for widespread use. But costs have plummeted.
Today, wind and solar power are the
cheapest new source of electricity in most markets. Electric vehicle sales are
setting records. Automakers like Ford and General Motors are now preparing to
phase down sales of gasoline-powered cars in the years ahead.
At the same time, coal power, a
major source of emissions, has begun to wane. A decade ago, China and India
were building new coal-burning power plants nearly every week. That pace has
now slowed: After the Paris agreement, one
recent study found, countries canceled 76 percent of proposals for new coal
plants.
All of this has made a difference.
Between 2000 and 2010, global emissions rose 3 percent per year on average. But
between 2011 and 2019, emissions grew
more slowly, at roughly 1 percent per year.
The International Energy Agency now
projects that global carbon dioxide emissions could potentially peak
by the mid-2020s, then start gradually declining.
That would likely put the world on
pace to warm a bit less than 3 degrees by 2100, although there are still
uncertainties around whether current policies will work as intended and how
sensitive Earth’s climate actually is to our greenhouse gas emissions.
Still, scientists warn, that number
isn’t something to celebrate. Yes, 3 degrees is far less nightmarish than 4
degrees. But it is immensely dangerous.
Consider the vast ice sheets atop
Greenland and West Antarctica, which together hold enough water to raise global
sea levels nearly 40 feet and sink many of the world’s great coastal cities.
The Intergovernmental Panel on Climate Change recently
warned that at sustained global warming levels between 2 degrees and 3
degrees, those ice sheets could melt irreversibly for thousands of years until
they are almost entirely gone, condemning future generations to massive,
relentless sea-level rise for centuries to come.
“We know there are these big
tipping points in the climate system, and once we get past them, it’s too late
to go back,” said Andrea Dutton, a climate scientist at University of
Wisconsin-Madison who co-authored a study finding
that a 3 degree trajectory could lead to an abrupt jump in the rate of
Antarctic melt as early as 2060.
Promises on Paper
As governments have awakened to the
danger, they have vowed to do more. But so far, their promises often just exist
on paper.
Ahead of the Glasgow summit, at least
140 countries have
formally updated their plans to curb emissions through 2030. The
United States and European Union pledged to pursue deeper cuts. Indonesia and
Mexico promised to slow future growth in fossil-fuel use. But other major
emitters, like China and India, have yet to update their short-term plans.
If countries follow through on
these new pledges, Climate Action Tracker estimates, the world could
potentially get on track to hold warming to around 2.4 degrees
Celsius by 2100, although temperatures would keep rising thereafter.
But that’s a big if.
Many pledges aren’t yet backed up
by concrete policies, and countries aren’t all on track to meet them. One recent
study by the Rhodium Group found that even if the Biden administration
implemented a sweeping package of climate measures — including hundreds of
billions of dollars in clean energy spending that remains stalled in Congress —
and individual states adopted tougher rules of their own, the United States
would barely stay on track to meet its target.
And that’s not the hardest part. In
recent years, more than 50 countries plus the European Union have formally
vowed to get to “net zero” emissions, which is essentially a promise to stop
adding greenhouse gases to the atmosphere altogether by a certain date. The
United States said it would get to net zero by 2050. China said it would strive
to get there by 2060.
In theory, those goals could have a
powerful impact. Climate Action Tracker estimates that
if every country met its net zero pledge, the world could potentially limit
warming to around 2 degrees Celsius by the end of the century.
But these plans would
require extremely rapid reductions in fossil-fuel use from power
plants, factories and vehicles, as well as potentially new technology to pull
carbon dioxide out of the atmosphere. Many net zero goals remain largely
aspirational, and governments have not yet laid out credible plans for
achieving them.
“You can see the glass as half-full
or half-empty,” said Dr. Höhne. “The half-full story is that countries have
good intentions and are sending the right signals to investors. The half-empty
story is that none of the countries that have pledged to go to zero have
sufficient short-term policies to really put themselves on track.”
A Narrow Path Forward
Even as humanity has chipped away
at the climate problem over the past decade, scientists have made progress,
too. And their findings are dire: They have gathered stronger evidence that
even small temperature increases can be powerfully damaging.
In other words, the goal posts have
moved.
When the Paris agreement was
signed, nations agreed that they should keep total global warming “well below”
2 degrees Celsius and make a good-faith effort to stay at 1.5 degrees. But in
the years since, a slew of studies have found that 2 degrees of warming is
vastly more harmful than 1.5 degrees.
That extra half a degree sounds
small, but it could mean tens of millions more people worldwide exposed to
life-threatening heat waves, water shortages and coastal flooding. Half a
degree may mean the difference between a world with coral reefs and Arctic
summer sea ice, and a world without them.
“We’re already seeing today, at
just 1 degree of warming, that certain societal systems are more vulnerable to
disruption than we previously thought,” said Joeri Rogelj, director of the
Grantham Institute for Climate Change and the Environment at Imperial College
London.
In response, a growing number of
world leaders, including President Biden, have said that the world should hold
to 1.5 degrees of warming, although some countries like China
have not embraced the stricter goal.
Yet 1.5 degrees is a vastly harder
target to hit than 2 degrees or 3 degrees. It’s not nearly enough for global
emissions to peak in the next few years and then decline gradually. Instead,
global fossil-fuel emissions would have to plunge roughly in half this decade
and then reach net zero by around 2050.
This year, the International Energy
Agency laid
out a road map for what that might look like. By 2030, electric
vehicles would have to make up more than half of new car sales globally, up
from just 5 percent today. By 2035, wealthy countries would have to shut down
virtually all fossil-fuel power plants in favor of cleaner technologies like
wind, solar or nuclear power. By 2040, all of the world’s remaining coal plants
would have to be retired or retrofitted with technology to capture their carbon
emissions and bury them underground. New technologies would be needed to clean
up sectors like air travel.
The agency estimates that current
policies worldwide will deliver only one-fifth of the emission cuts needed this
decade to stay on track for 1.5 degrees. Without an immediate and rapid
acceleration of action, that climate goal could be out of reach within a few
short years.
“The pathway is extremely narrow,”
said Fatih Birol, the executive director of the International Energy Agency.
“We really don’t have much time left to shift course.”
