A new study reads like a detective story, involving the illicit use of a synthetic chemical banned by a landmark environmental treaty and the scientists who track the violations down.

Why it matters: In the study published in Nature, an international team of researchers used a high-resolution air-observing network to hunt down the suspected source region for a disturbing uptick in emissions of a banned, ozone-destroying chemical known as CFC-11. The increase was first reported last year, minus a clear emissions source.

• A single molecule of CFC-11 lingers in the air for about 52 years, during which time it can destroy parts of the protective ozone layer, which shields the Earth from the sun's harmful UV radiation. It's also a powerful greenhouse gas.
• CFC-11 is used to produce foam insulation for refrigerators, air conditioners and buildings.

Driving the news: The study found that illegal use of CFC-11 in two industrial provinces in eastern China, Shandong and Hebei, are likely responsible for up to 60% of the globally observed spike in CFC-11, which is banned under the Montreal Protocol.

What they did: For the research, scientists used observations taken downwind of China at Gosan, South Korea, and Hateruma, Japan. Sensors there sniff the air nearly continuously for CFC-11 and other compounds.

• Scientists used computer models to generate back trajectories to see where the air came from when CFC-11 spikes occurred.

What they found: Emissions of CFC-11 from eastern mainland China were about 7 million kilograms per year higher from 2014 to 2017 when compared to 2008–2012, the study finds.

What they're saying: Co-author Ray Weiss says the Chinese emissions may only account for about half of the total increase in CFC-11 emissions since 2013, but that finding the other sources is difficult due to a lack of observing networks.

• For example, he tells Axios there are no CFC monitoring stations in China.
• Gaps also exist for parts of Africa and the Middle East.
• "This brings to us the importance of a comprehensive mechanism for monitoring and enforcement of the treaty, otherwise all the benefits ... would only remain on paper," says Avipsa Mahapatra of the Environmental Investigations Agency, who was not involved in the new study.

What's next: While China works to crack down on illicit production and use of CFC-11, the global community faces another looming test: How to verify nations' commitments under the Paris Climate Agreement.

Go deeper: Read the full story

A struggle is brewing between the nation's weather and climate agencies and the wireless industry concerning 5G spectrum and the accuracy of your weather forecast, Axios' Kim Hart and I report.

Why it matters: A significant degradation in forecast accuracy could cause ripple effects throughout the economy, and could cost lives.

Details: In March, the FCC began auctioning off spectrum in the 24 GHz band of radio frequencies, which are high-frequency microwave licenses to be used in delivering the 5G services the nation's carriers are vying to deploy.

The problem: These auctioned airwaves are near those used by NOAA and NASA sensors on Earth-observing satellites, particularly a sensor called the Advanced Technology Microwave Sounder. It's designed to see through clouds to understand what is happening inside weather systems, and it operates at a frequency of 23.8 GHz.

"Microwave satellite data is the weather-equivalent of a medical CAT scan," says Jordan Gerth, a meteorologist at the University of Wisconsin.

• Right before the auction began, NOAA and NASA warned that using the 24 GHz airwaves for 5G purposes could interfere with weather-forecasting sensors on polar-orbiting satellites.

Since the auction began, NOAA and NASA's concerns over the interference concerns have grown louder.

• On May 16, acting NOAA administrator Neil Jacobs told Congress that the emissions limit advanced by the FCC would result in about a 77% data loss from passive microwave sounders.
• "If you look back in time to see when our forecast skill was roughly 30% less than it was today, it's somewhere around 1980," Jacobs said.

The other side: This week, the wireless industry's main lobbying group CTIA torched the Commerce Department for using what it says are false interference claims to undermine the Trump administration's 5G strategy, and for not voicing concerns earlier in the 5-year planning process.

Meteorologists disagree: "The CTIA post is misleading if not inaccurate," Gerth tells Axios. "If 5G networks are deployed under the terms of the sale, this is a legitimate threat to forecast quality."

• "Our frequency allocations are based on the properties of molecules; we cannot sense somewhere else."

What's next: The U.S. will negotiate interference issues and technology standards with other countries that use global airwaves for 5G this fall at the World Radiocommunication Conference in Egypt.

Go deeper: Read the full story.

A team of scientists report in Science Thursday they can now show how quickly E. coli can become resistant to tetracycline, Eileen Drage O'Reilly reports.

• Bacteria can pass genes with resistance to each other and then use a pump to keep most of the antibiotic out for the 2 hours it takes to render the previously sensitive bacteria resistant to the drug.

Why it matters: Antibiotic resistance is a growing threat that's projected to kill 10 million people every year by 2050. The discovery of how it occurs, at least in a lab setting, could help scientists develop an inhibitor that could be combined with an antibiotic to boost its effectiveness, study co-author Christian Lesterlin tells Axios.

What they found, per Lesterlin, of the University of Lyon in France:

• The bacterium can become resistant in less than 2 hours after getting the new genetic material: "It all happens very quickly."
• The role of the multidrug efflux pump is "essential" to the acquisition of new resistance by gene transfer between the E. coli.
• Even when the antibiotic tetracycline is present, the cells use the pump to export the antibiotics from the cell and "buy time for the cell" to acquire resistance.

What they're saying: ETH Zurich's Vanessa R. Povolo and Martin Ackermann write in an accompanying perspective piece that the findings offer what could be an "important element" in the fight against antibacterial resistance — that the development of pump inhibitors will be key.

What's next: Lesterlin says they hope to perform follow-up tests in mammals, as well as testing other antibiotics or with other bacteria to see if they have similar responses.

Go deeper: Read the full story

A little-known index is key to understanding how the Earth's climate continues to build up heat in the air and oceans, resulting in sweeping changes across the globe.

Why it matters: Known as the Annual Greenhouse Gas Index, or AGGI, which NOAA produces, it clearly shows that despite numerous agreements and goals for cutting greenhouse gas emissions, the ability of the atmosphere to trap extra heat keeps growing.

Details: This year the AGGI rose to a value of 1.43, meaning that the increase in the atmosphere’s heat-trapping capacity attributable to human activity has risen 43% since 1990. James Butler, who directs NOAA's air monitoring program, tells Axios the growth in the AGGI is accelerating.

“It’s a measure of what we’ve already committed towards causing climate to change,” Butler says. "Since 1990, we’ve added 43% more long-lived greenhouse gases than in the previous 240 years.”

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This submarine’s historic tour under Thwaites Glacier will help scientists predict sea level rise (Carolyn Beeler, PRI/The World)

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The Baffling Case of the Belugas that Won’t Bounce Back (Amorina Kingdon, Hakai Magazine)

The definition of the kilogram just changed. Here's what that means (Jaclyn Jeffrey-Wilensky, NBC News)

Climate change: Sea level rise could displace millions of people within two generations (Jonathan Bamber and Michael Oppenheimer, The Conversation)

Scientists now have evidence that a volcanic eruption millions of years ago spread ash across the surface of Mars, according to a new study.

Why it matters: Scientists have long-suspected that early Mars played host to explosive volcanic eruptions, but proof eluded them until now. Thanks to newly analyzed photos from orbit, researchers now have evidence that those eruptions did occur when the planet was still a wet world.

Details: Early in Mars’ history, water vapor likely dissolved in the planet’s magma, producing extreme pressure and causing volcanic explosions that then resulted in ash falling down to the planet’s surface.

• However, when the planet dried out, those explosive eruptions gave way to oozing flows instead, the researchers found.
• The new study in the journal Geology found that deposits of olivine in a region known as Nili Fossae appear to have been caused by an ashfall, not oozing lava or an asteroid impact, as earlier work suggested.
• The authors of the study found that the ash fell along the crater’s surface in “long continuous layers,” according to a news release.

What’s next? NASA is gearing up to send another rover to the Martian surface in 2020 that should be able to sample this site.

• “What’s exciting is that we’ll see very soon if I’m right or wrong,” Christopher Kremer, a study author, said in the statement.

The AGGI data NOAA released this week shows that methane, a more powerful but shorter-lived greenhouse gas compared to carbon dioxide, has rapidly increased during the past 5 years. The rate of methane increase has jumped 50% since 2007–2013, NOAA says.

Details: Scientists have been trying to explain this increase. Experts tell Axios it's clear the long-term growth in methane concentrations is related to human activities, from cattle farming to natural gas drilling.

"I think we are confident that part of the recent increase is due to greater extraction and use of natural gas, especially in the U.S.," says Drew Shindell of Duke University. "Even if leak rates were constant, when we use more, we leak more."

What's next: But scientists still need a better understanding of how much of the recent methane rise is natural, how much could be a climate change feedback, such as melting permafrost, or other sources. New monitoring networks or satellites could solve this, Shindell says.