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Last Summer Was the Hottest in 2,000 Years

On historical heat data, clean hydrogen, and solar geoengineering

Last Summer Was the Hottest in 2,000 Years
Heatmap Illustration/Getty Images

Current conditions: Wildfires continue to burn out of control in western Canada • An early season heat wave will bring record high temperatures to parts of Florida • One in eight Europeans now live in an area at risk of flooding.


1. Study: Last summer was the hottest in 2,000 years

We already know that last summer was the hottest “on record” – but those records only really go back to the 1850s or so. A new study published in the journal Nature looks further into the past and concludes that last summer was the warmest in some 2,000 years in the Northern Hemisphere. To reach this conclusion, researchers examined thousands of tree rings, which offer clues about a year’s temperature and moisture levels. The tree ring data suggests last summer was about 4 degrees Fahrenheit warmer than the average temperature of the years 1 AD to 1890 AD. The study warns that summer 2024 could be even warmer than 2023.

A separate study out yesterday concluded that Southeast Asia’s intense April heat wave was fueled by man-caused climate change. In the Philippines, for example, a 15-day heat wave pushed the heat index to 113 degrees Fahrenheit, disrupting daily life and forcing many schools to close. This extreme weather would have been “impossible” without climate change, the study found.

2. House Democrats launch probe into Trump’s meeting with Big Oil execs

House Democrats have launched an investigation into a recent Mar-a-Lago dinner where former President Donald Trump reportedly asked Big Oil bosses to put $1 billion toward his 2024 presidential campaign and promised to roll back some environmental rules should he win back the White House. The House oversight committee sent letters to oil executives from Cheniere Energy, Chesapeake Energy, Chevron, Continental Resources, EQT Corporation, ExxonMobil, Occidental Petroleum, Venture Global and the American Petroleum Institute. They want the companies to list who attended the meeting, provide copies of any documents distributed, describe any policies that were discussed, and disclose any contributions made to Trump’s campaign during or after the dinner, according toThe Washington Post. The top Democrat on the committee, Rep. Jamie Raskin, gave the executives a deadline of May 27 to turn over information, but the committee’s investigative powers are limited by the GOP’s control of the House. “If the oil companies decline to turn over the information, Democrats will not be able to subpoena the firms, stymying their investigation,” explained the Post.

3. Trump chides Biden on new Chinese EV tariffs

President Biden confirmed yesterday that he is imposing a 100% tariff on Chinese-made electric vehicles, as well as tariff increases on other clean energy technologies including lithium batteries, solar cells, and critical minerals. Former President Trump, speaking from outside the New York courtroom where his hush money trial is taking place, said: “Where have they been for three-and-a-half years? They should have done it a long time ago.”

There is no equivalence between Biden’ tariffs and the 10% across the board tariff on all imported goods from all countries that Trump has proposed, wrote Heatmap’s Robinson Meyer. “Biden’s new tariffs focus on certain strategic sectors that American officials believe the country must cultivate to stay at the technological frontier, coupled with pre-existing subsidies meant to spur domestic production of those goods. Some of the tariffs only kick in beginning in 2026 — far enough in the future, policymakers hope, for the market to prepare. Trump’s tariffs, meanwhile, would intentionally and chaotically hike prices.”

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  • 4. DOE offers Plug Power $1.66 billion conditional loan for green hydrogen plants

    The Department of Energy yesterday offered Plug Power a conditional commitment of $1.66 billion in loan guarantees to build up to six clean hydrogen plants that use the company’s electrolyzer technology. The hydrogen would “power fuel cell-electric vehicles used in the material handling, transportation, and industrial sectors, resulting in an estimated 84% reduction in greenhouse gas emissions compared to conventional hydrogen production,” the DOE announcement said. Most hydrogen production uses fossil fuels to run an electrolyzer that splits water into hydrogen and oxygen. But clean hydrogen relies on electrolyzers powered by renewable sources – or natural gas with carbon capture. The Biden administration sees clean hydrogen as a key part of its push to decarbonize heavy industry. The deal isn’t done yet – Plug will have to prove its projects will benefit local communities and “satisfy certain technical, legal, environmental, and financial conditions” before the loan goes ahead. But the news sent Plug’s stock soaring nonetheless.

    5. California officials pause solar geoengineering study over safety concerns

    In case you missed it earlier this week (I did!), officials in California have ordered researchers to stop using an aerosol sprayer to test a potential solar geoengineering process for cooling the planet, The New York Timesreported. The Cloud Aerosol Research Instrument, or CARI, sits on the flight deck of the Hornet, a decommissioned aircraft carrier in Alameda, California. It sprays sea salt aerosol particles into the air, a process that could one day be used to brighten clouds and reflect the sun’s rays. This experiment, which began in early April, marked the first time such a device had been tested outdoors in the U.S. But the city of Alameda told the scientists to stop their research until the health and environmental impacts of the experiment can be evaluated. “The city is evaluating the chemical compounds in the spray to determine if they are a hazard either inhaled in aerosol form by humans and animals, or landing on the ground or in the bay,” city officials said.


    Police in the U.K. could soon carry “Ghostbusters-style devices” that use electromagnetic rays to stop e-bike engines if a rider is suspected of being involved in a crime.

    Jessica  Hullinger profile image

    Jessica Hullinger

    Jessica Hullinger is a freelance writer and editor who likes to think deeply about climate science and sustainability. She previously served as Global Deputy Editor for The Week, and her writing has been featured in publications including Fast Company, Popular Science, and Fortune. Jessica is originally from Indiana but lives in London.


    How Floods Are Contributing to Pregnancy Loss in India

    “She was traumatized by the flood and wasn’t getting a nutrient-rich diet for several weeks.”

    A pregnant woman and flooding.
    Heatmap Illustration/Getty Images

    Ashwini Khandekar was in her first few months of pregnancy when the flood came. This was July 2021, the peak of the annual monsoon season, when a downpour destroyed more than 300 houses in Ganeshwadi, a village 400 kilometers south of Mumbai in India’s Maharashtra state. Authorities instructed Khandekar and her husband to evacuate, she told me, “but I couldn’t leave my house because all the evacuation centers were full. I had nowhere to go.” Though in the end her home was spared, for the next 15 days, Khandekar lived in constant fear, praying until the waters finally abated.

    Four months later, Khandekar went to the doctor for a prenatal checkup. Her child, she learned, showed signs of anencephaly, a condition in which the fetal brain and skull fail to develop normally. Usually, babies born with anencephaly die within a few hours, and most pregnancies end in miscarriage. To cross-check the doctor’s claims, Khandekar visited eight more hospitals. Everyone confirmed the same. “I was heartbroken,” she said.

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    AM Briefing: Deadly Weekend

    On a devastating landslide, the most active storm day of the year so far, and more.

    City in the morning.
    Heatmap Illustration/Getty Images

    Current conditions: Early summer heat wave threatens the South • Temperatures climb to a near-record 125 degrees Fahrenheit in Pakistan • It’s 60 degrees and rainy in Paris where the French Open is underway.


    1. Over 2,000 people buried by landslide in Papua New Guinea

    A massive landslide reportedly buried alive more than 2,000 people in northern Papua New Guinea on Friday. Over 670 people have already been reported dead but experts warn the death toll will rise far higher as rescuers pick through the devastation. Aid workers have also reportedly struggled to reach the affected area with roads blocked and the ground still unstable.

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    Why Republicans Grilled the Energy Secretary About UFOs

    You have to get creative when you allege a “war on energy” during an oil boom.

    Jennifer Granholm and UFOs.
    Heatmap Illustration/Getty Images

    When Donald Trump met with a group of oil executives at Mar-a-Lago last month, his message was somewhere between “refreshingly blunt” and “blatant shakedown.” Attendees spilled to The Washington Post that Trump told the executives they should raise a billion dollars for his campaign so he could make them even richer by reducing their taxes and removing regulations on their industry.

    One can’t help but wonder if any of them thought to themselves that as appealing as that kind of deal might be, there’s no reason for them to be desperate. After all, the Biden years have actually been quite good for the fossil fuel industry.

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