Last summer's extreme weather was a showcase of how global warming is altering our atmosphere, from a scorching heat wave that contributed to a spate of wildfires in Scandinavia and California to devastating floods and all-time record-high temperatures set around the Northern Hemisphere.

What's new: A new study, published last week in the journal Science Advances, ties these events and other summertime extremes to human-caused climate change via an increase in a specific jet stream phenomenon, lead author Michael Mann of Penn State tells Axios.

Details: Daniel Swain, a climate scientist at UCLA who was not involved in the new research, explains the phenomenon — known as quasi-resonant amplification, or QRA — this way: "Quasi-resonant amplification refers to a condition where high-altitude winds across the Northern Hemisphere enter a spatial configuration favorable for the development and persistence of big loops in the jet stream," he says.

• That extra-wavy jet stream can cause extreme events, such as heat waves and flooding rains, to occur on either side of the jet stream's "ridges" and "troughs," particularly when such patterns get locked in place.

What they did: The authors devised an indirect method of detecting changes in QRA events by examining the differences in temperature across the Northern Hemisphere and how it changes from north to south worldwide.

• The researchers also simulated the recent and future climate using numerous computer models to project how such jet stream patterns might change.

What they found: An uptick in such QRA events can, in part, be tied to rapid Arctic climate change.

• The Arctic is warming at about twice the rate of the rest of the planet, altering the temperature contrast between the equator and the pole. This gradient is a large part of what drives the jet stream.
• Overall, the jet stream phenomena tied to prolonged, severe weather extremes are likely to increase in frequency by about 50% during this century if current emissions trends continue.
• Some models show a tripling in QRA frequency.

The new study also found an unexpected result: Cutting aerosol pollution (tiny particles in the air from burning coal, for example) may prevent the jet stream from getting hung up as frequently in the future.

• Cleaning up aerosols quickly, such as by cutting power plant pollution in China and India, could lead to fewer QRA events during part of the 21st century.
• Mann cautioned that the computer models showed considerable uncertainty around this finding, though.

What they're saying: Jennifer Francis, a scientist at Woods Hole Research Center who was not involved in the new research, told Axios the study adds valuable new information.

"I think they're onto an important mechanism that helps explain the influences of a rapidly warming Arctic on summer weather extremes over midlatitude continents. ... The underlying drumbeat in both seasons is about persistent patterns and conditions that can turn into extreme events; in summer, this means heatwaves, floods and drought." 

In the largest examination to date of genetic material from ancient Americans, researchers found some genetic similarity among remains in Montana, Nevada and Brazil — showing there was likely a rapid migration of people from the tip of North America, Eileen Drage O'Reilly reports.

Why it matters: Researchers want to better understand how people first migrated, dispersed and settled into the different areas of the Americas. These genetic samplings — including some more than 10,000 years old — bolster theories of what may have happened, but also bring forth new questions, particularly about new lineages that were discovered.

Background: Existing theories range from people arriving via what was then the Bering Land Bridge between Russia and Alaska or coming along the Pacific Coast — and at different times.

• Relatively new information has shown there were likely people in North America before the so-called Clovis occupants around 13,000 years ago.
• Previous genomic studies have suggested the first American populations diverged from their Siberian and East Asian ancestors nearly 25,000 years ago and then split into distinct North and South American populations about 10,000 years later.

What's new:

1. A study in Science analyzed 15 diverse bone samples — 6 of which are more than 10,000 years old — from sites across North and South America.

• The findings suggest the population expanded "very rapidly" thousands of kilometers south, but in uneven spurts, and then diversified into multiple population types.
• For instance, as co-author Eske Willerslev of the University of Copenhagen pointed out in a press briefing, genomes from the Spirit Cave Mummy found in Nevada are related to those of the Anzick child found in Montana as well as remains found in Lagoa Santa, Brazil.
• "The implication of that is that, if you’re moving that far that fast across space ... there wasn’t anything to obstruct you or your movement, or mobility. And yet we know that we have people in the Americas prior to this time ..." says study co-author David Meltzer of Southern Methodist University.

"So that raises the really interesting question: Was no one else home? Yet we suspect archaeologically there was and we’re actually getting some hints in the genetic record that there were other populations present as well."

• The researchers also discovered a population about 11,700 years ago that had Australasian ancestry evident only in South America (it hasn't been found in North America yet).

2. Another study, in Cell Press, examines 49 individuals spanning about 10,000 years in Belize, Brazil, the Central Andes and southern South America.

• The findings show a North American Clovis-associated genome (called the Anzick-1) from around 12,800 years ago "shares distinctive ancestry" with the oldest Chilean, Brazilian and Belizean individuals.
• The authors say this supports the hypothesis that the Clovis people also migrated to Central and South America. However, they add, because the Anzick-1 gene itself is not found throughout South America, this means there must have been at least one other founding group.
• They also say there was evidence that ancient humans from California's Channel Islands have significant genetic similarities with those living in the Central Andes at least 4,200 years ago.

Read Eileen's full story here.

At least 7 new members of Congress elected Tuesday have STEM backgrounds — an unusually large number that comes in part due to a concerted effort to recruit candidates with science backgrounds.

Why it matters: Having a larger crop of members who understand complex scientific topics, from climate change to nuclear engineering, could result in legislation that better incorporates scientific information.

• It could also improve oversight of science-focused agencies like NASA and the Energy Department, experts tell Axios.

The big picture: Scientists were mobilized by how swiftly and broadly the Trump administration moved to roll back regulations on climate change, land use and other issues.

• The March for Science movement led to recruitment drives by groups such as 314 Action, a political action committee that sought to sign scientists up to run for office and support them financially. Several of their endorsed candidates won on Tuesday.

The winners: The list of new STEM members (all Democrats):

• Chrissy Houlahan, engineer — 6th district, Pennsylvania
• Lauren Underwood, registered nurse and health policy specialist — 14th district, Illinois
• Jeff Van Drew, dentist — 2nd district, New Jersey
• Sean Casten, biochemical engineer — 6th district, Illinois
• Kim Schrier, pediatrician —8th district, Washington
• Elaine Luria, nuclear engineer — 2nd district, Virginia
• Joe Cunningham, marine engineer — 1st district, South Carolina

These new members will join two Democratic incumbents: Rep. Bill Foster of Illinois, a physicist, and Rep. Jerry McNerney of California, who has a Ph.D. in mathematics.

There will be one new senator with a STEM background, too: Jacky Rosen, who defeated incumbent Republican Sen. Dean Heller in Nevada. Prior to serving in the House, she was a computer programmer and software developer.

• Some prominent science advocates lost re-election, however — notably Republican Rep. John Culberson of Texas, a key supporter of NASA's research programs.

The bottom line: "We need scientists in Congress to represent the scientific perspective whenever an issue is being discussed," Rush Holt, CEO of the American Association for the Advancement of Science — and himself a physicist and former congressman from New Jersey — tells Axios. Their specific expertise, he says, is less important than the fact that "they will have a professional background in evidence-based thinking."

It's not aliens! Despite speculation ignited by a pre-print study, it's highly unlikely that the interstellar object known as Oumuamua is an alien light sail or a spaceship.

SpaceX: The commercial space company led by Elon Musk has launched a $750 million leveraged loan led by Bank of America Merrill Lynch. The move could result in some of the company's financials becoming public, writes Dan Primack.

Nuclear power: The Union of Concerned Scientists, a high-profile environmental group, is joining other organizations in calling for U.S. nuclear power plants to stay open due to their low greenhouse gas emissions, Amy Harder writes.

Fact-checking Trump: In an Axios interview, President Donald Trump disavowed a seminal climate science report issued by his own government's scientists and said climate varies naturally. Amy Harder and I fact-checked his claims.

The Placebo Effect: In a NYT Magazine feature, Gary Greenberg details efforts to figure out why the so-called placebo effect seems to work so well in certain people with particular conditions. New findings may challenge conventional wisdom, with implications for drug development and approval, he writes.

Pyramids of Giza discovery: Researchers uncovered a ramp with postholes that may have been used to transport stones at 20-degree inclines in order to build the pyramids, helping to explain one of the great mysteries of these ancient structures, Kevin Rawlinson writes in The Guardian.

Whale shark ultrasound: Watch as fisheries scientist Rui Matsumoto performs an ultrasound on an adult female whale shark near the Galapagos Islands. Scientists know precious little about how these massive sharks reproduce, writes Jason Bittel for the Washington Post.

Historically, a story on the ozone hole would be a bummer.

Well, not this time. It's taken decades, but a UN report released this week shows that the Montreal Protocol on Substances that Deplete the Ozone Layer, a global treaty that went into force in 1987, is finally paying off in the form of a healing stratospheric ozone layer.

Why it matters: The ozone "hole" over Antarctica was one of the most shocking and disturbing scientific findings in global environmental history when it was made more than two decades ago.

• The stratospheric ozone layer shields the surface from harmful ultraviolet radiation from the sun.
• With a depleted ozone layer, there is a higher risk of skin cancer and other illnesses in humans and animals alike.

Details: Unlike what is happening with climate change, science translated almost directly into action on the ozone. Countries moved to ban the use of chlorofluorocarbons, or CFCs, which break down ozone in the upper atmosphere. Because of CFC's long atmospheric lifetime, we're only now seeing the dividends.

• The new UN report, which is the first ozone assessment since 2014, found that the amounts of ozone-destroying chemicals have continued to decline.
• They project the amount of ozone in the atmosphere in the Northern Hemisphere should return to 1980 levels by the 2030s. In the Southern Hemisphere, where atmospheric circulation has caused more severe ozone depletion, the UN projects the ozone hole will "gradually close" by the 2060s.

The bottom line: It's fortunate that scientists discovered the ozone hole when they did and that action was taken swiftly. Otherwise, we could've been dealing with far more severe ozone depletion throughout this century and into the next.