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June 29th, 2020

The South Pole feels Pacific heat

CU Boulder scientists spell out the evidence and consequences of rapid warming at the South Pole and call for action to “flatten the curve” of global carbon emissions in an article released today.

In a “news and views” piece in the journal Nature Climate Change, Sharon Stammerjohn of INSTAAR and Ted Scambos of the Cooperative Institute for Research in Environmental Sciences (CIRES) track how surface temperatures over the South Pole region have changed from steady or slightly cooling to warming rapidly. They highlight a new study by an international team of researchers led by Kyle Clem, that finds a dramatic switch in the warming rate at the South Pole.

The climate of Antarctica tends to be more variable than that of the rest of the planet, showing major swings in temperatures over decades. Much of this variability comes from the western Pacific Ocean, driven by a giant complex of temperature trends called the Inter-decadal Pacific Oscillation. Like El Niño but larger, the Inter-decadal Pacific Oscillation tends to persist for tens of years and then “flip” into an opposite phase.

Over the last half of the twentieth century, surface temperatures over the South Pole were steady or slightly cooling. “A cooling trend at South Pole from the 1960s to about the year 2000 built a mindset (for some) that the South Pole was cooling and therefore warming was not global,” said Scambos. “But it is; it’s just a question of patience.”

When the Pacific pattern flipped again, around the year 2000, the South Pole began to warm at three times the global rate, the Clem study found. The change in the Pacific pattern combined with stronger westerly winds around Antarctica, which are linked to global warming, to pump warmer air to the South Pole.

Scambos observed, “Although the pattern will reverse again (it likely has already, in recent years), the system now may be more like a tilted staircase—rapid warming during periods of western Pacific warmth, and slower warming or slight cooling in other times as the warming planet exerts a less-direct influence while the Pacific is in the other pattern.”

“I see warming at South Pole as the ultimate canary in the coal mine, one that we can no longer ignore,” said Stammerjohn. “While warming at the South Pole may not specifically affect global climate directly, the same causes that allowed the South Pole to warm are already affecting other, more vulnerable areas around Antarctica that indeed affect everything else on this planet.”

“Increased regional warming and melting of Antarctica is already impacting global ocean circulation and sea-level rise, as well as altering global atmospheric circulation patterns,” she continued. “The most dire concern related to all of these changes is the fact that Antarctica's weak underbelly, the marine-grounded West Antarctic Ice Sheet, is rapidly melting from below, and is already precariously perched on a very delicate tipping point. If that point is crossed due to business-as-usual and persistent warming, will lead to catastrophic continental ice mass loss, followed by the rapid disappearance of coastlines everywhere.”

Stammerjohn and Scambos end their article by calling out the severe dangers of a warmer world and calling for action to bring down the carbon emissions that are changing the global climate. “Unless we take measures to flatten the curve on global carbon emissions...The collateral damage will not just be accelerated warming and disappearing coastlines, but everything we value that sustains us,” they write.

“We also know, perhaps better than before, we can live more sustainably.”

A penguin stands atop an ice floe near the coast of Antarctica. Photo courtesy of Ted Scambos.