Updated Aug 16, 2018

El Niño may make a comeback this fall and winter

Note: Temperature anomalies are relative to the 1985 to 2012 average; Data: National Oceanic and Atmospheric Administration; Map: Chris Canipe/Axios

Odds favor a return this year of the climate phenomenon known as El Niño — above-average sea surface temperatures in the equatorial tropical Pacific Ocean and related changes in weather patterns.

Why it matters: Depending on their intensity and exact location, El Niño events can alter global weather patterns — favoring above average precipitation in the parched state of California, for example, while inducing drought elsewhere. Typically, such events develop sometime in late summer or early fall, and peak during the winter.

Such events also can provide a natural pulse of heat released from the ocean to the atmosphere, boosting the odds that 2018 and possibly 2019 could be among the top five warmest years on record.

The big picture: The last El Niño event took place in 2015 and 2016, and it was one of the strongest on record. Michelle L’Heureux, a meteorologist at NOAA's Climate Prediction Center in Maryland, tells Axios that the upcoming event — which has about a 70% likelihood of occurring by the upcoming winter — is unlikely to be as potent.

"If something forms it’s likely to be on the weaker side of things," she said. "In general, weaker events tend to be a bit tougher to predict than stronger events.”

For signs of El Niño, scientists like L'Heureux look at sea surface temperatures in specific parts of the tropical Pacific, known as El Niño regions. These are the boxed areas on the sea surface temperature chart. In recent weeks, ocean temperatures have increased in parts of these areas.

But the formation of El Niño is a complicated dance between air and sea, and now, L'Heureux says, it's the atmosphere's turn to alter trade winds in a way that reinforces the changes in the water. These air and ocean feedbacks are what really get an El Niño going.

Go deeper

Hottest decade on record

Illustration: Aïda Amer/Axios

2019 wasn't just the second-hottest year on record — the 2010s will go down as the hottest decade in human memory, per a new report.

Driving the news: The Copernicus Climate Change Service found "an unrelenting upward trend in temperatures as emissions of greenhouse gases trap heat in the atmosphere and change the climate," the N.Y. Times notes.

Go deeperArrowJan 8, 2020

Alaska experienced its hottest year on record in 2019

Photo: Vintagepix/Getty Images

Alaska endured its hottest year in recorded history in 2019, according to the National Centers for Environmental Information.

By the numbers: The state's average temperature sat at 32.2°F, which was 6.2°F hotter than the long-term average. Last year's temperatures topped 2016's previous record, which saw the statewide average at 31.9°F. For the first time on record, Anchorage recorded a 90°F day in July.

Go deeperArrowJan 8, 2020

Study: Climate change effects apparent in daily global weather data

Concrete blocks are placed along the shoreline to try and prevent further coastal erosion, on December 2019 in Mahibadhoo, Maldives.

The imprint of climate change is now apparent in global weather data at a daily level, according to a new paper in the peer-reviewed journal Nature Climate Change.

Why it matters: "If verified by subsequent work, the findings ... would upend the long-established narrative that daily weather is distinct from long-term climate change," the Washington Post reports.

Go deeperArrowJan 3, 2020