Climate change is having a breakout performance this year. Throughout the U.S., the slow-motion calamity long described in scientific studies and news articles has been visible to the naked eye or felt on tingling flesh — here too wet, there too dry, everywhere too hot. It’s only human to wonder where the higher, safer ground might be. Where to run?

The answer: No one really knows. It’s not just that the map of places prone to extreme events is expanding, making the question both more pertinent and more difficult. It’s that, even as the reality of global climate change becomes ever more certain, predicting its local effects remains anything but a sure bet.

Consider America’s two Portlands — Oregon and Maine. Tucked into the northwest and northeast corners of the Lower 48, each was thought to be a safe haven from the ravages of climate change. Not anymore.

———

In 2011, students in an urban studies class at Portland State University in Oregon were asked to consider the future impact of climate change on the region. Their 93-page report states: “Climate change impacts in Oregon are predicted to be less severe than in other areas of the country. Generally, models project warmer, wetter winters and hotter, drier summers in the Willamette Valley and other areas west of the Cascade Range. This will likely make the Willamette Valley a more desirable place for environmentally displaced people to locate.”

Indeed, the Northwest is often cited as a potential retreat from climate chaos. But the term “hotter, drier summers” has taken on some unexpected detail in recent months.

Fires have burned 380,000 acres of Oregon this year, following a hot, dry and fiery 2020. A half dozen major fires still burn in the state. Air quality is a major concern throughout Oregon. At one point this summer, it was considered good news that the smoke from forest fires was so heavy that the dense cloud that resulted might reduce temperatures by a degree or two.

In June, Portland reached a record 116 degrees in the midst of a freakish heat wave. The temperature, which followed record-breaking highs on each of the two previous days, could have been worse. In the village of Lytton, British Columbia, 400 miles north of Portland, the temperature hit 121 degrees.

———

Portland, Maine, is another place that has received attention as a potential refuge from climate chaos. It makes sense. Portland is cool and coastal while being less vulnerable to the sea rise that is already complicating life in many East Coast cities.

On the other hand, Portland is not exactly balmy, with an average low temperature in January of 13 degrees. So any prospect of the city getting colder is cause for concern.

To understand how that could happen, it’s necessary to understand the evolution of the Atlantic Meridional Overturning Circulation, the ocean current system of which the Gulf Stream is a part. The AMOC, as it’s known, transports warm surface waters up the East Coast of North America before crossing the Atlantic to Northern Europe.

A study published in August in the journal Nature Climate Change notes that, over the last century, “the AMOC may have evolved from relatively stable conditions to a point close to a critical transition.” The change to the AMOC is related to a North Atlantic “cold blob” created by a melting Greenland ice sheet and greater rainfall in the region.

“The warm, salty Gulf Stream feeds into the northward flowing current that forms the upper limb of the AMOC in the northern North Atlantic,” writes Columbia University oceanographer Arnold Gordon in an email. But not all of the Gulf Stream flows north into the AMOC. Part of it turns south. “The ratio of the northward flowing limb and the southward flowing limb varies,” Gordon writes. With climate change, he writes, “the models suggest less will go northward.”

The potential outcome of this global atmospheric and underwater turmoil is colder water off the coast of Portland. Instead of getting a little warmer from climate change, Gordon writes, Maine’s largest city might get a little cooler.