New Yorkers sweating through this month’s heat wave can blame the oceans — a cool patch of water off the Pacific coast of Peru, more than 3,500 miles away (5,632 kilometers), and near-record warmth offshore in the Atlantic. The cause and effect is a reminder that climate change’s toll is coming due.
The cold water across the equatorial Pacific is locking in place two high pressure systems — reservoirs of heat — at either end of the continent. These weather patterns, also called ridges, promote heat and dry out the land beneath them. At the same time, the Atlantic Ocean is feeding its warmth onto the land, adding to heat that is already fixed across the U.S.
“Once you get a dome of heat like that it is very tough to get rid of it,” said Jim Rouiller, lead meteorologist at the Energy Weather Group LLC. “The weather models may chop it up, but it’s resilient, you might get two days of normal but we rebound again.
The first half of 2020 was already quite hot — just 0.05 degree Celsius lower than the record set in 2016, according to the National Centers for Environmental Information in Asheville, North Carolina. The odds are high 2020 will end up in the top five warmest years ever.
In the last 30 days, 97 all-time warm records were set around the U.S. with no low temperature marks being posted. In the previous 12 months, 179 warmest records were set to just 12 lows.
The heat in the year’s first half has already had consequences. It pushed waters in the Gulf of Mexico to record highs in spring, leading Florida to experience summer-like temperatures in April. It has also fueled the Atlantic along the U.S. East Coast to warmer-than-normal levels, a condition made worse in recent weeks as temperatures have soared across North America. Many daily heat records that fell in the last week were near the coastline, surprising some meteorologists.
Right now the Atlantic is quite hot. The water off Long Island is 76.3 degrees Fahrenheit (22.7 degrees Celsius), according to the U.S. National Data Buoy Center.
“Once a heat wave gets established, it tends to perpetuate itself because the soil gets drier and drier, which allows it to get hotter and hotter,” said Jennifer Francis, a researcher at the Woods Hole Research Center.
This is where climate change is making things worse, she said. As the planet warms, the contrast between the heat at the equator and the cold at the pole decreases. That saps the strength of the jet stream, which otherwise would serve to defuse the heat. The result is a circular river of winds too weak to move these big ridges of hot air across continents. Hence, the dome of heat stays stuck for weeks or months.
“Heat waves are getting hotter, pure and simple,” Francis said. “It’s one of the most direct symptoms of global warming.”
The intense heat raises the possibility for drought, which adds to the potential for temperatures to rise even more. Without moisture in the soil, the sun’s energy is focused on heating the air and not evaporating water, which just drives up temperatures even more. The cool Pacific water that’s helping produce the heat is close to becoming what’s known as a La Nina, which can cause droughts and floods worldwide.
There are silver linings. In the Midwestern crop belt, blasts of rain during the past few weeks should help alleviate the drought conditions that have crept up in states including Nebraska, Iowa, Indiana and Ohio. The rainfall, combined with sweltering heat, should be a boon for crops like corn, which typically go through the yield-setting pollination phase in July.
Matt Bennett, a farmer in central Illinois and commodity analyst at AgMarket.Net, planted his crops in April, earlier than usual, because of the warm temperatures. “Hot and wet is what you want,” he said.
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