LA CORONILLA, Uruguay — 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 thinshelled, cold-water clams, which burrow a foot deep into the sand along a 13-mile 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.

"Kilometer after kilometer, 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 that 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 130,000 square miles of ocean, an area almost twice as big as this small country. And it has been heating up extremely rapidly — by over 2 degrees Celsius (3.6 degrees Fahrenheit) over the past century, double the global average. At its center, it's grown even hotter, warming by as much as 3 degrees Celsius (5.4 degrees Fahrenheit), 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 algae 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 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.

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 degrees Celsius, when the last five years are compared with the mid to late 1800s. That area is more than five times the size of the U.S.

About 20% of the planet has warmed by 1.5 degrees Celsius (2.7 degrees Fahrenheit), 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 has warmed by 2 C or more.

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 of warming varies depending on the time periods considered. Over the past five years, 8% to 11% of the globe crossed the threshold, the Post found, while over the past 10 years, the figures drop slightly to between 5% and 9%. Considering just the past five years increases the area by roughly 40%.

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 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 U.S. It has thawed the winters of New England and transformed the summers of Siberia.

***

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 in South America, too.

Still, the overall consequences of these oceanic changes are likely to be negative, said Bárbara Franco, who studies fisheries and climate change at the University of Buenos Aires. 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% 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 no-analog world that none of us has any experience with."

Takeaways

1 A Washington Post analysisof four global temperaturedata sets, spanning from the 1800s to the present, has found that over the past five years — the hottest on record — about 10% of the planet has exceeded warming of over 2 degrees Celsius, or 3.6 degrees Fahrenheit. Scientists have identified this as a clear line that the planet as a whole must not cross.

2 It's not just about the Arcticanymore. Depending on theanalysis used, we see 2 degree C of warming in much of Europe, northern Asia, the Middle East, and in key ocean hot zones.

3 Changes in ocean currents arecreating dramatic hot zones. Huge ocean currents are on the move, driven by changes in winds and atmospheric circulation.

4 These high levels of warming present major risks to marineeco systems. Clams are dying along beaches, ocean heat waves are killing fish and algae blooms are worsening.

5 Fish can swim elsewhere. That's not so easy for clams orcorals ... or people. When fast ocean warming occurs, only some species easily adjust.

6 More of the globe will be at 2C of warming very soon, according to the analysis using data from U.S. scientists and several academic groups. — the Washington post

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