This winter will be weird, and the weather will keep getting weirder

The Five-Year Forecast

Unseasonably warm, with freakish snowfalls and chance of cyclone. This winter will be weird, and the weather will keep getting weirder.

The next time you’re in Central Park, go up to Harlem Meer on the north end, then wander westward on the pathway into the heart of the park. After the first sharp turn, look off to the west and you’ll see a thick stand of ash, its rough bark set off by delicate oval leaves. Long before New York existed, the ash thrived in this region, and the city’s settlers used the tree’s dense but springy wood to make everything from church pews to baseball bats. The ash has been here since the beginning.

But its time is about to come to an end. In recent years, foresters have quietly decided not to plant any new ash trees. Why? Because the city is becoming too warm and dry for them, and they’re dying off. Green and white ash, our local varieties, are classified as “hardiness zone three or four,” northern trees that prefer moist, well-drained soil. New York used to be like that, 200 years ago—but the temperature in the past century has risen over two degrees, and it’s getting drier every year. “Last year we had stretches without rain that were practically six weeks long,” says Neil Calvanese, vice-president of operations for the Central Park Conservancy, which maintains the park. And the warmer weather has introduced new wood-eating bugs that afflict the tree. Normally an ash will live 250 years, but this summer Calvanese had to chop down a majestic 130-footer when it stopped thriving. “Ash in the park,” he says, “I really don’t see as having much of a future.”

So he’s decided to let the ash slowly die off. An urban forester has to think decades into the future, and the city’s only going to get hotter and hotter. Instead of the ash, city foresters are starting to plant trees like the persimmon, which thrives in southern climates like Washington’s or even Atlanta’s. Because that’s what the future of New York looks like, weather-wise: There will be fewer and fewer wooden baseball bats and church pews—but plenty of reddish-purple persimmon fruit.

Nor is Calvanese alone in planning for the next 50 years. In September, while unveiling plans for a new city bureau, the Office of Long-term Planning and Sustainability, the mayor pledged to make climate-change issues a priority. It’s not hard to understand why the idea finally occurred to Bloomberg. This summer, the weather was Topic A among New Yorkers, as we sweltered through a record-busting heat wave in July. You could see it in the worried faces of people as they marched miserably down the liquefying sidewalks this summer: Is this it? Has global warming finally arrived? Is this what we’re in for—permanently? The abrupt shift into a spookily mild fall, and especially the freakishly warm last few weeks, has only fanned the conversational fires.

If it seems like the city has been getting hotter for years, it’s not your imagination: Six of the top-ten hottest summers in the city have occurred since 1990. (In fact, we haven’t had a top-ten coolest summer since 1927.) But our summers aren’t the only extreme weather, because our winters have been breaking records in precisely the other direction. The last four winters have all had snowfalls way above average, a string that we haven’t seen since the 1800s. Worse, that record-breaking snow is coming in huge dumps—not a flake in the sky for months and months, then a huge blizzard that sweeps through town, brings the city to a halt, and vanishes a week later.

The weather isn’t just getting harsher: It’s getting weirder. Here’s why.

The little boy comes back.

If you had a satellite’s view of the Earth this summer, you would have noticed something odd happening to the equatorial Pacific: The water was getting warmer.

In June and July, government satellites and thermal buoys that track the heat of the ocean detected a huge mass of bathtub-warm water forming off the coast of Indonesia and Sri Lanka. By August, it had broken loose and begun to migrate across the ocean, headed toward Peru. The normally chilly waters of the Pacific gradually warmed and warmed, until by September the water along the entire equator—a mass twice the size of Europe—was one long ribbon of warm ocean.

It could mean only one thing: El Niño had returned.

El Niño—Spanish for “the little boy”—is one of the most powerful natural forces that affect global weather. An El Niño event begins when the trade winds in the Pacific break down. Normally they blow east to west, pushing the sun-warmed water on the surface of the Pacific toward Indonesia, where it piles up offshore and makes that nation particularly rainy and wet. Every two to seven years, though, for reasons that are still a bit mysterious, the trade winds falter. As they slacken, the trades’ grip on this pool of warm ocean-surface water slackens, and it begins to spread across the entire Pacific. A really strong El Niño will warm the coast of Peru by as much as eight degrees.

cont...

[link to nymag.com]