Last week’s Chicago heat wave was not a cheery time to think about the central United States getting hotter and drier.
But that’s what researchers at the University of Copenhagen’s Niels Bohr Institute say could happen if an important system of oceanic currents called the Atlantic Meridional Overturning Circulation suddenly shuts down irreversibly — perhaps within two years, perhaps by midcentury, maybe at the century’s end.
It’s yet another reminder to quickly ramp up efforts to stop contributing to global warming by doing such things as burning fossil fuels. Keeping the earth livable should be at the top of everyone’s to-do list. The smoke from Canadian forest fires that has rendered Chicago area air unhealthy or even dangerous on recent days is a sign the Midwest is not immune to the dangers of climate change.
The Atlantic currents are one of those tipping points that keep climate scientists up at night. Like a tower that loses one of its supports and suddenly begins collapsing, it’s too late to try to fix tipping points once they start to crumble. Already the system of currents has started to slow down. Recent studies show the system of currents is the weakest it’s been in 1,000 years.
The currents carry warm, salty water from the tropics to the North Atlantic, moderating weather in adjacent lands. The currents then send heavier and colder water back toward the tropics along the ocean floor. Northern Europe enjoys less harsh winters because of the currents, and the tropics get a cooling effect. If the currents stop circulating as they do now, sea levels could rise along the U.S. East Coast even faster than they are already doing. Northern Europe could get a new Ice Age.
The study published last week in Nature Communications, suggests Greenland ice melted by global warming and flowing into the ocean could severely skew the Atlantic currents or even stop them from circulating altogether, more quickly than has been predicted. Such a development could affect weather across the planet, the scientists said. As the South Atlantic warms, the rain and snow we are used to in Chicago could shift farther south.
‘Illinois is not prepared’
The impact of climate change is already here. Among the likely signs: On Friday, the National Weather Service said nearly 200 million people in the United States were under a heat advisory or flood warning or watch. People in Phoenix could get third-degree burns by falling on pavement. Excessive heat fueled thunderstorms in the Northeast. The West has been suffering from a historic drought. Waters off the southern U.S. warmed to levels unprecedented since human beings started to roam the earth.
As of Friday, July was on a pace to be the hottest month on record.
Apart from the Atlantic currents possibly changing, other factors already are heating up Illinois, and neither Chicago nor the rest of the state is prepared to deal with it, said Jen Walling, executive director of the Illinois Environmental Council.
“Illinois is not prepared for the heat, for tornadoes, all those things,” Walling said.
Some scientists say the new study should be taken with a grain of saltwater. The United Nations Intergovernmental Panel on Climate Change thinks it unlikely the system of currents will collapse in this century.
But that’s not a reason to put off action. Global warming must be stopped before people suffer the worst effects, and that can’t be done in a day. Once the planet passes such tipping points as the loss of the Atlantic currents, it will be too late.
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