Already Over 2 degrees Celsius in Parts of the World
A Washington Post analysis of multiple temperature data sets found numerous locations around the globe that have warmed by at least 2 degrees Celsius over the past century. That's a number that scientists and policymakers have identified as a red line if the planet is to avoid catastrophic and irreversible consequences. But in regions large and small, that point has already been reached.
The Post analyzed four data sets, and found: Roughly one-tenth of the globe has already warmed by more than 2 degrees Celsius, when the last five years are compared with the mid- to late 1800s. That's more than five times the size of the United States.
Temperature change, 2014-2018 compared with 1880-1899
-1
1.5
2ºC
0
6+
Insufficient data
Atlantic Ocean
Indian Ocean
Pacific Ocean
Source: Berkeley Earth
About 20 percent of the planet has warmed by 1.5 degrees Celsius, a point at which scientists say the impacts of climate change grow significantly more intense.
The fastest-warming zones include the Arctic, much of the Middle East, Europe and northern Asia, and key expanses of ocean. A large part of Canada is at 2C or higher.
Straddling the equator, the tropics are already hot because they receive the most sunlight. As the sun hits the tropics, enormous columns of air rise skyward and then outward. But as greenhouse gases trap more heat, those columns of air are pushed farther toward the north and south poles.
Air that rises in the tropics falls back down over the middle latitudes. With a warming planet, though, the air is falling in different places.
One region where that air sinks is the South Atlantic Ocean, where the tropical expansion has led to a southward shift in the location of a gigantic counterclockwise circulation of winds. These winds, in turn, drive key ocean currents, including a warm, salty, 60-mile-wide stream called the Brazil Current, which is being pushed even farther south.
Near Uruguay, the Brazil Current collides with the cold and nutrient-rich Malvinas Current that flows north from waters off Argentina. Where the two currents meet — what is known as the “confluence” — features sudden temperature contrasts and fosters rich fisheries.
But that zone, too, is on the move. Research suggests it is shifting southward at a rate of more than 40 miles per decade.
The result has been a stunning temperature change off the Uruguayan coast.
“The southward displacement of warm waters creates a very strong signal,” explains oceanographer Alberto Piola, a professor at the University of Buenos Aires.
The hot spot emerges most dramatically in The Post’s analysis when the most recent five years are compared with the last two decades of the 19th century. By this standard, it has only recently crossed the 2C threshold.
In 2012, scientists first flagged it as one of the ocean’s fastest-warming stretches. And they’ve attributed the changes to a broad global pattern that can’t be explained just by natural climate variability.
The consequences of a 2 degree warming are dire
When temperatures rise 1.5 to 2 degrees Celsius for the globe, according to a recent report by the United Nations Intergovernmental Panel on Climate Change, one of the most severely affected ocean animals will be bivalve species — clams, oysters, mussels and their relatives. Above 1.8 degrees Celsius or so, they face “very high risks” of population decline if not extinction, the report said.[....]
Climate change can make for winners and losers, especially when it comes to fisheries. Along the U.S. coast, fast-warming waters drove lobsters away from southern New England and into the Gulf of Maine, leading to crashing fisheries in one spot and a boom in another. That could be happening here, too.
Scientists say they are struggling to keep up with the impacts of a warming world, whether measuring changes in the Arctic or disappearing kelp forests in the southern Pacific.
“We’re really playing catch-up,” said marine scientist Boris Worm of Dalhousie University in Canada. “Everything we base our civilization on is based on the accumulated experience from the last 7,000 years, about how the world works, and how we can survive in this world that had an exceptionally stable climate.
“And we’re shifting away from that equilibrium at breakneck speed now. We’re living in a no-analog world that none of us has any experience with.”
Comments
Post a Comment