Episode Details

This week we talk about oceanic surface temperatures, trade winds, and global climate change.

We also discuss the Polar Jet Stream, hurricanes, and climate models.

Recommended Book: Kleptopia by Tom Burgis

Transcript

Under normal circumstances, the Pacific Ocean’s average surface temperature, the distribution of heat across its vast expanse, is moderated by trade winds that blow east to west along the equator, which help move warm water from South America over toward Asia.

Those winds are called trade winds because, back during the European age of Exploration, they helped ships from Europe head west toward Asia and the Americas. And these winds form in part because of the Earth’s rotation, the Coriolis effect funneling air toward the equator, where it is then more concentrated and thus potent, which is useful if you’re trying to move a ship with sails, but also serves the purpose of moving warm water from one part of the ocean to another part of the ocean.

As those warmer surface waters are shifted from the Americas to Asia, water is pulled up to the surface from lower down in the ocean as part of a process called upwelling. This process results in cooler temperatures on the surface, because lower down, oceanic water is colder, and that lower-down water is also more rich in nutrients, which has the knock-on effect of stimulating more biological activity along these cooling surface waters.

That’s the normal state of things in the Pacific Ocean.

There are sometimes deviations in this norm, however, that result in very different outcomes; these deviations are broadly called the El Niño Southern Oscillation Cycle, and that cycle consists of opposite El Niño and La Niña climate patterns.

During La Niña patterns, trade winds are more powerful than usual and they shove a lot more of that warm surface water to Asia than is typical, and that has the net impact of moving more deep-down cold, nutrient-rich, ocean water to the surface.

This, in turn, nudges the Polar Jet Stream, which is a channel of fast-moving, westerly winds that lives about 30,000 ft or just over 9000 meters up in the sky, and which crosses both warmer, mid-latitudes and far colder Arctic latitudes, further north. The Polar Jet Stream is responsible for moderating or intensifying weather patterns around the world, and like the trade winds, it’s influenced by the spin of the planet, but it’s also adjusted by surface systems, like the temperature of the Pacific. So the arrival of a La Niña pattern pushes the jet stream further north, and as a result, weather patterns change, and in North America, we tend to see drought in the southwest, heavier rains and flooding and in the Pacific Northwest and Canada, warmer winters in the South, and cooler winters in the North.

La Niñas also tend to result in more severe hurricane seasons in the Atlantic basin, while suppressing hurricane activity in the central and eastern Pacific basins.

El Niño, in contrast, results from weaker trade winds, which, because these winds don’t pack as much of a punch, means less warm water is being shoved from South America to Asia, and thus the surface temperature of that part of the Pacific is warmer, lacking that upwelling of cold water to replace the warm water that would otherwise be displaced over to Asia.

El Niño also adjusts the location of the jet stream, but in the opposite direction, pulling it south of its usual spot. That then causes more heat and dryness across the northern US and Canada, but makes the southern US and Gulf Coast a lot wetter, leading to more flooding.

What I’d like to talk about today are predictions about an anticipated upcoming El Niño climate pattern, and why some climate scientists are warning that it could be a doozy.

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Climate scientists with the US’s National Oceanic and