Enlarge / Damage from the 1964 earthquake and tsunami in Kodiak, Alaska. (credit: Education Images via Getty )

On an overcast day in September, Heidi Geagel negotiates familiar potholes on a gravel road in Seldovia, Alaska. Cresting a hill topped with a small chapel, her town spreads out below—in the bay, gently rocking fishing boats; onshore, the Linwood Bar & Grill, the Crab Pot Grocery, and a couple dozen homes on stilts.

Geagel, Seldovia’s city manager, turns around to three people sitting in the back seat, who partner with the United States’ National Tsunami Hazard Mitigation Program and have traveled in from Anchorage and Fairbanks for a meeting with community leaders about tsunami hazards. She points out how much of the landscape could be underwater if one of the giant, fast-moving waves were to hit: “Pretty much the entire map of Seldovia is in the inundation zone, except for this hill.”

Alaska is uniquely vulnerable to two types of tsunamis. The first, tectonic tsunamis, are linked to the long string of volcanic islands that curves like a tail from the state’s southern tip; these islands mark the northern edge of the Ring of Fire, a geologically active zone that generates approximately 90 percent of the world’s earthquakes. Tracing those islands, deep under water, is the Alaska-Aleutian subduction zone, a trench where vast plates of hard rock overlap and friction slowly builds. Once or twice a year, the subduction zone generates earthquakes strong enough to trigger tsunami alerts; every 300 to 600 years or so, it ruptures in a megaquake that sends devastating tectonic tsunamis to Alaska’s shores.

Enlarge (credit: Marc Bruxelle )

"Climate breakdown has begun," declared UN Secretary-General António Guterres. Guterres is not a climate expert himself, but in this case, he's basing his opinion on the data and analyses generated by the actual experts. If you thought this year was a bit of a weather suffer-fest, it probably wasn't your imagination, as the Northern Hemisphere has just experienced its hottest summer on record, driving the year to date into the second-hottest position.

While the weather isn't climate, the climate sets limits on the sort of weather we should expect. And a growing number of analyses of this year's weather are showing that climate change has been in the driver's seat for a number of events.

Hot, hot, hot

On Wednesday, the World Meteorological Organization released its August data , showing that the month was the second hottest on record and the hottest August we have experienced since temperature records have been maintained. The only month that has ever been warmer is... the one immediately before it, July of 2023.

Enlarge / Youth plaintiffs are greeted by supporters as they arrive for the nation's first youth climate change trial at Montana's First Judicial District Court on June 12, 2023. (credit: William Campbell / Contributor | Getty Images North America )

A Montana state court today sided with young people who sued the state for promoting the fossil fuel industry through its energy policy , which they alleged prohibits Montana from weighing greenhouse gas emissions in approving the development of new factories and power plants. This prohibition, 16 plaintiffs ages 5 to 22 successfully argued, violates their constitutional right to a "clean and healthful environment in Montana for present and future generations."

Experts previously predicted that a win for youths in Montana would set an important legal precedent for how courts can hold states accountable for climate inaction. The same legal organization representing Montana's young plaintiffs, Our Children's Trust, is currently pursuing similar cases in four other states, The Washington Post reported .

The Post described this landmark case as "the nation’s first constitutional and first youth-led climate lawsuit to go to trial."

Enlarge / Elkhorn coral fragments rescued from overheating ocean nurseries sit in cooler water at Keys Marine Laboratory. (credit: NOAA )

Armed with scrub brushes, young scuba divers took to the waters of Florida’s Alligator Reef in late July to try to help corals struggling to survive 2023’s extraordinary marine heat wave. They carefully scraped away harmful algae and predators impinging on staghorn fragments, under the supervision and training of interns from Islamorada Conservation and Restoration Education , or I.CARE.

Normally, I.CARE’s volunteer divers would be transplanting corals to waters off the Florida Keys this time of year, as part of a national effort to restore the Florida Reef . But this year, everything is going in reverse.

As water temperatures spiked in the Florida Keys, scientists from universities, coral reef restoration groups, and government agencies launched a heroic effort to save the corals. Divers have been in the water every day, collecting thousands of corals from ocean nurseries along the Florida Keys reef tract and moving them to cooler water and into giant tanks on land.

Enlarge / A tourist refreshes at a vapor barrier in Budapest, Hungary, on July 16, 2023. (credit: Arpad Kurucz/Anadolu Agency via Getty Images )

Because you’re a smooth-skinned mammal, no weather feels quite as oppressive as a humid heat wave. The more water vapor in the air, the less efficiently your sweat can evaporate and carry excess heat away from your skin. That’s why 90° Fahrenheit in humid Miami can feel as bad as 110° in arid Phoenix .

Climate change has supercharged this summer’s exceptionally brutal heat all around the world —heat waves are generally getting more frequent, more intense, and longer. But they are also getting more humid in some regions, which helps extend high temperatures through daytime peaks and into the night. Such relentless, sticky heat is not just uncomfortable, but sometimes deadly, especially for folks with health conditions like cardiovascular disease.

One of the more counterintuitive effects of climate change is that a warmer atmosphere can hold more water vapor than a colder one. A lot of it, in fact: Each 1.8° Fahrenheit bump of warming adds 7 percent more moisture to the air. Overall, atmospheric water vapor is increasing by 1 to 2 percent per decade . That additional wetness is why we’re already seeing supersize downpours, like the flooding that devastated Vermont earlier this month .

Enlarge / A billboard in Phoenix, Ariz. displays the temperature on July 18, 2023 during an unprecedented string of days with high temperatures above 110° F. (credit: Patrick T. Fallon/AFP via Getty Images)

Widespread summer heatwaves like those currently baking the Northern Hemisphere, with temperatures soaring above 110 degrees Fahrenheit simultaneously in North America, Asia and Europe, will be common in just a few decades unless greenhouse gas emissions are immediately curtailed, an international team of scientists said Monday.

If global warming reaches 2 degrees Celsius above the pre-fossil fuel era, such heat waves will happen every two to five years, the researchers said as they released a rapid attribution analysis of the blistering conditions experienced by hundreds of millions of people in recent weeks. If emissions continue on the same increasing path as now for a few more years, the 2 degree Celsius mark will be passed in about 30 years, according to the new analysis by World Weather Attribution .

In the current climate, warmed by 1.1° C (1.9° F) by humans, these extreme heatwaves are no longer rare, “due to warming caused by burning fossil fuels and other human activities,” the authors wrote. “Events like these can now be expected approximately once every 15 years in North America, about once every 10 years in southern Europe and approximately once every five years in China.”

Enlarge / Wildfire smoke hovers over the Pacific coast of northern New South Wales, Australia in September 2019. (credit: Orbital Horizon/Copernicus Sentinel Data/Gallo Images via Getty Images)

The aerosol fallout from wildfires that burned across more than 70,000 square miles of Australia in 2019 and 2020 was so persistent and widespread that it brightened a vast area of clouds above the subtropical Pacific Ocean.

Beneath those clouds, the ocean surface and the atmosphere cooled, shifting a key tropical rainfall belt northward and nudging the Equatorial Pacific toward an unexpected and long-lasting cool phase of the La Niña-El Niño cycle, according to research published today in Science Advances.

Aerosols from wildfires are basically fire dust—microscopic bits of charred mineral or organic matter that can ride super-heated wildfire clouds up to the stratosphere and spread across hemispheres with varied climatic effects, depending on where they’re produced and where they end up.

Enlarge / Fire-damaged trees in a boreal forest near the Saskatchewan River in Alberta, Canada. As northern forests burn, they're releasing massive amounts of carbon. (credit: Ed Jones/Getty Images)

The far north is both a massive carbon sink and a potent environmental time bomb . The region stores a huge amount of CO ₂ in boreal forests and underlying soils. Organic peat soil , for instance, covers just 3 percent of the Earth’s land area (there’s some in tropical regions, too), yet it contains a third of its terrestrial carbon. And Arctic permafrost has locked away thousands of years’ worth of plant matter, preventing rot that would release clouds of planet-heating carbon dioxide and methane .

But in a pair of recent papers, scientists have found that wildfires and human meddling are reducing northern ecosystems’ ability to sequester carbon, threatening to turn them into carbon sources . That will in turn accelerate climate change, which is already warming the Arctic four and a half times faster than the rest of the world, triggering the release of still more carbon—a gnarly feedback loop.

Enlarge / Wolf Point Creek is likely the most-well-studied glacier-fed stream in the world. (credit: Elizabeth via Flickr (CC BY-NC 2.0) )

Pushing off from the dock on a boat called the Capelin , Sandy Milner’s small team of scientists heads north, navigating through patchy fog past a behemoth cruise ship. As the Capelin slows to motor through humpback whale feeding grounds, distant plumes of their exhalations rise from the surface on this calm July morning. Dozens of sea otters dot the water. Lolling on backs, some with babes in arms, they turn their heads curiously as the boat speeds by. Seabirds and seals speckle floating icebergs in this calm stretch of Alaska’s Glacier Bay.

Some two hours later, the craft reaches a rocky beach where Wolf Point Creek meets the sea. The creek is a relatively new feature on the landscape: Land at its mouth first became ice-free in the 1940s due to the melting and retreat of a glacier. It took shape through the 1970s, fed by a mountain lake that slowly formed as an isolated chunk of glacier ice slowly melted. Wolf Point Creek is special because almost its entire life span — from the first, sparse trickles melting out under the ice edge to a mature stream ecosystem teeming with aquatic life, from tiny midge larvae to small fish, and with willows and alder weaving along its edges — is known in intimate detail, its history painstakingly documented.

Milner, a stream ecologist at the University of Birmingham in the UK, has returned almost annually to this spot since the 1970s to catalog how life — particularly aquatic invertebrates — has arrived, thrived and changed over time. He was here to observe meager midges in 1977 and to spot a hundred prospecting pink salmon in 1989. A decade later, his team cataloged 10,000 of the fish spawning in Wolf Point Creek.