If the use of fossil fuel continues, scientists warn that warming will melt the ice caps, "which will expose bare ground, increase heat absorption at high latitudes, and cause more warming." (photo: Diane Cook/Len Jenshel/National Geographic)
Crocodiles
and Palm Trees in the Arctic? New Report Suggests Yes.
By Marianne Lavelle,
National Geographic
15 June 16
If
we keep burning fossil fuels, Earth will be 8 degrees warmer, returning to the
climate of 52 million years ago, according to new research. It's the most dire
prediction yet.
In
even the bleakest climate change scenarios for the end of this century, science
has offered hope that global warming would eventually slow down. But a new
study published Monday snuffs out such hope, projecting temperatures that rise
lockstep with carbon emissions until the last drops of oil and lumps of coal
are used up.
Global
temperatures will increase on average by 8 degrees Celsius (14.4 degrees F)
over preindustrial levels by 2300 if all of Earth’s fossil fuel resources are
burned, adding five trillion metric tons of carbon to the atmosphere, according
to the research by Canadian scientists published in Nature Climate Change. In the Arctic, average
temperatures would rise by 17 degrees C (30.6 degrees F).
Those conclusions
are several degrees warmer than previous studies have projected.
If
these temperatures do become reality, greenhouse gases would transform Earth
into a place where food is scarce, parts of the world are uninhabitable for
humans, and many species of animals and plants are wiped out, experts say.
"It
would be as unrecognizable to us as a fully glaciated world," says Myles Allen, head of a climate dynamics group at
the University of Oxford in the United Kingdom. Allen was not involved in the
new study, but his research has focused on carbon’s cumulative impacts on
climate.
Noting
that it took less warming, 6 degrees C (10.8 degrees F), to lift the world out
of the Ice Age, Allen said,
"That's the profundity of the change we're talking about."
The
8-degree rise in global temperatures would blast past the 2 degrees C (3.8 degrees
F) limit that nations agreed upon last year in the Paris talks.
It
also would heat the world to a level approaching that of the early Eocene
period, 52 million to 56 million years ago, when palm trees grew as far north as Alaska and
crocodiles swam in the Arctic.
Mammals
survived Eocene temperatures; this is when early primates appeared. Some
horses, however, shrank to the size of house cats, adjusting through
evolution to a diet altered either by heat or carbon. Today's organisms and
ecosystems may not be able to adapt to warming over the next 200 to 300 years—an
instant on the geological time scale, says Scott Wing, the Smithsonian Institution’s curator
of fossil plants.
Also,
Wing notes that when the Eocene heat began, the Earth's poles weren't covered
with ice as they are today. "In the future, warming will melt ice caps,
which will expose bare ground, increase heat absorption at high latitudes, and
cause more warming," Wing says. Polar
melt would commit the Earth to sea-level rise that would mean upheaval for
coastal populations, which make up more than 40 percent of humanity.
The
study predicts that precipitation would quadruple in the tropical
Pacific, while it would be reduced by up to third in the Americas and a factor
of two over parts of Australia, the Mediterranean, southern Africa, and the
Amazon.
Allen
says not only could tropical rain forest systems collapse, but drought in
southern Europe and the United States would be "completely catastrophic
for agriculture." Wealthy nations might maintain food supply, but not
places like southern Africa. "A lot of people would have to leave, or a
lot of people would die," Allen says.
Katarzyna Tokarska, a researcher at the
University of Victoria in British Columbia, Canada, led the new modeling in an
effort to address a key question left unanswered by the Intergovernmental Panel on
Climate Change (IPCC) in its consensus reports. The IPCC's
worst-case scenario only charts warming up to two trillion metric tons of
cumulative added carbon in 2100. In the new study, Tokarska and her colleagues
asked what would happen if all known and recoverable fossil fuel
resources were used.
The
IPCC's worst-case projection is a temperature rise of 2.6 degrees C to 4.8
degrees C by 2100, and the few studies that go beyond that year suggest that
warming would slow because of the physics of greenhouse gases at high
concentrations. Tokarska and her team say that these past projections failed to
include the complex give-and-take of carbon on Earth. Most importantly,
oceans—like a saturated sponge—lose their ability to absorb more heat and
carbon, leaving it nowhere to go but the atmosphere.
Of
course, no one can say whether civilization will continue to burn oil and coal
as long as it's available. Sheik Ahmed Yamani, Saudi Arabia's oil minister in
the 1970s, famously said the Stone Age didn't end because humanity ran out of
stones, and the oil age will end before it runs out of oil. But experts suspect
that continued burning of fossil fuels is virtually inevitable until cleaner
alternatives are cheaper and widely available globally.
Allen
says the new findings are important at a time when some climate action opponents
assert that warming would have beneficial effects.
The
IPCC's limited time horizon can create such a misperception,says Matthew Huber, an earth
scientist at both Purdue and the University of New Hampshire.
"The
fixation on what happens by the year 2100 is unhealthy and ignores the large
risks that become apparent when thinking on longer time scales and with a more
complete treatment of real physical and biological processes," he says.
Huber
says the new research doesn't mean there would be tropical conditions in the
Arctic. His own studies indicate that such a transformation would require 10
degrees C (18 degrees F) more warming at the poles than the new study projects.
Yet he
says the temperature rise likely would be enough to spur killer heat waves in
highly populated regions of the planet.
"The
health and economic impacts of such warming would be vast and unprecedented in
human history,” he says.
Allen
agrees with the authors of the new study that their work bolsters the case for
a "carbon budget" approach to climate policy: setting a cap on
cumulative emissions. In contrast, the current approach of reducing emission
rates simply defers dangerous warming.
A
carbon budget approach implies that carbon emissions must reach zero—either by
"keeping it in the ground," as some activists put it, or by capturing
carbon or storing it.
The
Paris Accord avoided mention of a carbon budget, but Allen says the science
should point policy in that direction.
"The
first thing we need to do to get to zero [emissions] is acknowledge we need to
get there," he says.
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