Dangerous hot zones spreading
The day the yellow clams turned black is seared in Ramón Agüero’s memory.
It was the summer of 1994. A few days earlier, he had collected a generous haul, 20 buckets of the thin-shelled, cold-water clams, which burrow a foot deep into the sand along a 20-km stretch of beach near Barra del Chuy, just south of the Brazilian border. Agüero had been digging up these clams since childhood, a livelihood passed on for generations along these shores.
But on this day, Agüero returned to find a disastrous sight: the beach covered in dead clams.
“Kilometre after kilometre, as far as our eyes could see. All of them dead, rotten, opened up,” remembered Agüero, now 70. “They were all black, and had a fetid odor.” He wept at the sight.
The clam die-off was an alarming marker of a new climate era, an early sign of this coastline’s transformation. Scientists now suspect the event was linked to a gigantic blob of warm water extending from the Uruguayan coast far into the South Atlantic, a blob that has only gotten warmer in the years since.
The mysterious blob covers 337,000 square kilometres of ocean, an area nearly twice as big as this small country. And it has been heating up extremely rapidly – by over 2 C – over the past century, double the global average. At its centre, it’s grown even hotter, warming by as much as 3 C, according to one analysis.
The entire global ocean is warming, but some parts are changing much faster than others – and the hot spot off Uruguay is one of the fastest. It was first identified by scientists in 2012, but it is still poorly understood and has received virtually no public attention.
What researchers do know is that the hot zone here has driven mass die-offs of clams, dangerous ocean heat waves and algal blooms, and wide-ranging shifts in Uruguay’s fish catch.
The South Atlantic blob is part of a global trend: around the planet, enormous ocean currents are traveling to new locations. As these currents relocate, waters are growing warmer. Scientists have found similar hot spots along the western stretches of four other oceans – the North Atlantic, the North Pacific, the South Pacific, and the Indian.
A Washington Post analysis of multiple temperature data sets found numerous locations around the globe that have warmed by at least 2 C 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.
A study of data from Berkeley Earth shows how the temperature average of the last five years compares with 1880-1899:
• The Post analyzed four data sets, and found: roughly one-tenth of the globe has already warmed by more than 2 C, 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.
• About 20 per cent of the planet has warmed by 1.5 C, 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 2 C or higher.
Some entire countries, including Switzerland and Kazakhstan, have warmed by 2 C. Austria has said the same about its famed Alps.
The percentage of the globe that has exceeded 2 C varies depending on the time periods considered. Over the past five years, eight to 11 percent of the globe crossed the threshold, The Post found, while over the past 10 years, the figures drop slightly to between fiveand nine per cent. Considering just the past five years increases the area by roughly 40 per cent.
These hot spots are the scenes of a critical acceleration, places where geophysical processes are amplifying the general warming trend. They unveil which parts of the Earth will suffer the largest changes.
Extreme warming is helping to fuel wildfires in Alaska, shrink glaciers in the Alps and melt permafrost across Canada’s Northwest Territories. It is altering marine ecosystems and upending the lives of fishermen who depend on them, from Africa to South America to Asia.
It is making already hot places in the Middle East unbearable for outdoor workers and altering forests, lakes and rivers in the United States. It has thawed the winters of New England and transformed the summers of Siberia.
Over the past five years, Earth has passed a significant threshold. The planet is now more than 1 C warmer than it was in the mid- to late 1800s, before industrialization spread across the world.
The Post’s analysis relied upon four separate temperature records from the U.S. government and scientific researchers. Variations in the data sets themselves, and how they were analyzed, produce somewhat different assessments of the extent of the planet that has warmed by 2C.
Because the Earth goes through a number of natural cycles, climate scientists consider long periods, of multiple years, to analyze temperature change. The Post’s analysis considered two “preindustrial” periods – the 50 years from 1850 to 1899 and the 20 years from 1880 to 1899.
It also considered two end periods, the past five years and the past 10, which were compared with the two preindustrial periods to determine the amount of warming that has taken place.
The past five years are by far the hottest – and display the most numerous and expansive 2C hot spots. And while five years may be a brief period in climatic terms, 2019 is already following the same ultrawarm pathway.
Barring some dramatic event like a major volcanic eruption – which can cause temporary global cooling by spewing ash that blocks the sun – scientists expect this to continue and steadily worsen.
“We’re not going to really cool down much in the future, so the last five years are indicative of the new normal,” said Zeke Hausfather, a researcher with Berkeley Earth, which produces one of the data sets The Post analyzed.
While the global data sets do not agree about what is happening to every stretch of the Earth, they show unmistakable patterns.
For instance, an intriguing group of ocean hot spots appears again and again. One cause? The tropics are expanding.
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, 100-kmwide 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 70 km per decade.
When temperatures rise 1.5 to 2 C 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 C 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.
Still, the overall consequences of these oceanic changes are likely to be negative, Franco said. Fisheries in Uruguay and Brazil are projected to decline by more than a quarter by the end of the century.
That could mean major harm to any number of small-scale fisheries, far beyond the community that gathers the yellow clam. According to the United Nations’ Food and Agriculture Organization, workers in these smaller, often local and subsistence-driven fisheries account for 90 per cent of all fishery workers around the globe, largely in developing countries. In many cases, they are earning the equivalent of less than $1 per day.
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 noanalog world that none of us has any experience with.”
Top, the sun rises behind an empty yellow clam shell sitting on the beach in Barra Del Chuy, Uruguay. Above, this map, using data from Berkeley Earth, shows how the temperature average of the last five years compares with 1880-1899. Below, the rise in global average temperatures.