This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

I’m ready for summer, but if this year is anything like last year, it’s going to be a doozy. In fact, the summer of 2023 in the Northern Hemisphere was the hottest in over 2,000 years, according to a new study released this week. 

If you’ve been following the headlines, you probably already know that last year was a hot one. But I was gobsmacked by this paper’s title when it came across my desk. The warmest in 2,000 years—how do we even know that?

There weren’t exactly thermometers around in the year 1, so scientists have to get creative when it comes to comparing our climate today with that of centuries, or even millennia, ago. Here’s how our world stacks up against the climate of the past, how we know, and why it matters for our future. 

Today, there are thousands and thousands of weather stations around the globe, tracking the temperature from Death Valley to Mount Everest. So there’s plenty of data to show that 2023 was, in a word, a scorcher. 

Daily global ocean temperatures were the warmest ever recorded for over a year straight. Levels of sea ice hit new lows. And of course, the year saw the highest global average temperatures since record-keeping began in 1850.  

But scientists decided to look even further back into the past for a year that could compare to our current temperatures. To do so, they turned to trees, which can act as low-tech weather stations.

The concentric rings inside a tree are evidence of the plant’s yearly growth cycles. Lighter colors correspond to quick growth over the spring and summer, while the darker rings correspond to the fall and winter. Count the pairs of light and dark rings, and you can tell how many years a tree has lived. 

Trees tend to grow faster during warm, wet years and slower during colder ones. So scientists can not only count the rings but measure their thickness, and use that as a gauge for how warm any particular year was. They also look at factors like density and track different chemical signatures found inside the wood. You don’t even need to cut down a tree to get its help with climatic studies—you can just drill out a small cylinder from the tree’s center, called a core, and study the patterns.

The oldest living trees allow us to peek a few centuries into the past. Beyond that, it’s a matter of cross-referencing the patterns on dead trees with living ones, extending the record back in time like putting a puzzle together. 

It’s taken several decades of work and hundreds of scientists to develop the records that researchers used for this new paper, said Max Torbenson, one of the authors of the study, on a press call. There are over 10,000 trees from nine regions across the Northern Hemisphere represented, allowing the researchers to draw conclusions about individual years over the past two millennia. The year 246 CE once held the crown for the warmest summer in the Northern Hemisphere in the last 2,000 years. But 25 of the last 28 years have beat that record, Torbenson says, and 2023’s summer tops them all. 

These conclusions are limited to the Northern Hemisphere, since there are only a few tree ring records from the Southern Hemisphere, says Jan Esper, lead author of the new study. And using tree rings doesn’t work very well for the tropics because seasons look different there, he adds. Since there’s no winter, there’s usually not as reliable an alternating pattern in tropical tree rings, though some trees do have annual rings that track the wet and dry periods of the year. 

Paleoclimatologists, who study ancient climates, can use other methods to get a general idea of what the climate looked like even earlier—tens of thousands to millions of years ago. 

The biggest difference between the new study using tree rings and methods of looking back further into the past is the precision. Scientists can, with reasonable certainty, use tree rings to draw conclusions about individual years in the Northern Hemisphere (536 CE was the coldest, for instance, likely because of volcanic activity). Any information from further back than the past couple of thousand years will be more of a general trend than a specific data point representing a single year. But those records can still be very useful. 

The oldest glaciers on the planet are at least a million years old, and scientists can drill down into the ice for samples. By examining the ratio of gases like oxygen, carbon dioxide, and nitrogen inside these ice cores, researchers can figure out the temperature of the time corresponding to the layers in the glacier. The oldest continuous ice-core record, which was collected in Antarctica, goes back about 800,000 years. 

Researchers can use fossils to look even further back into Earth’s temperature record. For one 2020 study, researchers drilled into the seabed and looked at the sediment and tiny preserved shells of ancient organisms. From the chemical signatures in those samples, they found that the temperatures we might be on track to record may be hotter than anything the planet has experienced on a global scale in tens of millions of years. 

It’s a bit sobering to know that we’re changing the planet in such a dramatic way. 

The good news is, we know what we need to do to turn things around: cut emissions of planet-warming gases like carbon dioxide and methane. The longer we wait, the more expensive and difficult it will be to stop warming and reverse it, as Esper said on the press call: “We should do as much as possible, as soon as possible.” 

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Related reading

Last year broke all sorts of climate records, from emissions to ocean temperatures. For more on the data, check out this story from December.

How hot is too hot for the human body? I tackled that very question in a 2021 story.  

Another thing

Readers chose thermal batteries as the 11th Breakthrough Technology of 2024. If you want to hear more about what thermal batteries are, how they work, and why this all matters, join us for the latest in our Roundtables series of online events, where I’ll be getting into the nitty-gritty details and answering some audience questions.

This event is exclusively for subscribers, so subscribe if you haven’t already, and then register here to join us tomorrow, May 16, at noon Eastern time. Hope to see you there! 

Keeping up with climate  

Scientists just recorded the largest ever annual leap in the amount of carbon dioxide in the atmosphere. The concentration of the planet-warming gas in March 2024 was 4.7 parts per million higher than it was a year before. (The Guardian)

Tesla has reportedly begun rehiring some of the workers who were laid off from its charging team in recent weeks. (Bloomberg)

→ To catch up on what’s going on at Tesla, and what it means for the future of EV charging and climate tech more broadly, check out the newsletter from last week if you missed it. (MIT Technology Review)

A new rule could spur thousands of miles of new power lines, making it easier to add renewables to the grid in the US. The Federal Energy Regulatory Commission will require grid operators to plan 20 years ahead, considering things like the speed of wind and solar installations. (New York Times)

Where does carbon dioxide go after it’s been vacuumed out of the atmosphere? Here are 10 options. (Latitude Media)

Ocean temperatures have been extremely high, shattering records over the past year. All that heat could help fuel a particularly busy upcoming hurricane season. (E&E News)

New tariffs in the US will tack on additional costs to a wide range of Chinese imports, including batteries and solar cells. The tariff on EVs will take a particularly drastic jump, going from 27.5% to 102.5%. (Associated Press)

A reporter took a trip to the Beijing Auto Show and drove dozens of EVs. His conclusion? Chinese EVs are advancing much faster than Western automakers can keep up with. (InsideEVs)

Harnessing solar power via satellites in space and beaming it down to Earth is a tempting dream. But the reality, as you might expect, is probably not so rosy. (IEEE Spectrum)

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

Tesla, the world’s largest EV maker, laid off its entire charging team last week. 

The timing of this move is absolutely baffling. We desperately need many more EV chargers to come online as quickly as possible, and Tesla has been a charging powerhouse. It’s in the midst of opening its charging network to other automakers and establishing its technology as the de facto standard in the US. Now, we’re already seeing new Supercharger sites canceled because of this move. 

The charging meltdown at Tesla could slow progress on EVs overall, and ultimately, the whole situation shows why climate technology needs a whole lot more than Tesla. 

Tesla first unveiled the Supercharger network in 2012 with six locations in the western US. As of 2024, the company operates over 50,000 Superchargers worldwide. (By the way, I want to note that I briefly interned at Tesla in 2016. I don’t have any ties to or financial interest in the company today.) 

The Supercharger network helped make Tesla an EV juggernaut. Fast charging speeds and a navigation system that took the guesswork out of finding charging stations helped ease the transition for people buying their first EVs. Tesla operates more fast chargers than anyone else in the US, and the reliability of those chargers is leagues better than that of competitors. For a long time, this was all exclusive to Tesla drivers. 

Over the past year, Tesla has begun cracking open the doors to its charging network. The company made some of its stations available to all EVs, in part to go after incentives designated for private companies building public chargers. 

In the US, Tesla has also persuaded other automakers to adopt its charging connector, which it standardized and named the North American Charging Standard. In May 2023, Ford announced a move to adopt the NACS, and nearly every other automaker selling EVs in the US has followed suit.

Then, last week, Tesla laid off its 500-person charging team. The move came as part of wider layoffs that are expected to affect 10% of Tesla’s global workforce. Even interns weren’t immune.

Tesla “still plans to grow the Supercharger network,” though the focus will shift to maintaining and expanding existing locations rather than adding new ones, according to a post from CEO Elon Musk on the site formerly known as Twitter. (How does the company plan to expand or even maintain existing locations with apparently no dedicated charging team? Your guess is as good as mine. Tesla didn’t respond to a request for comment.)

But the effects from losing the charging team were immediate. Tesla backed out of a handful of leases for upcoming Supercharger locations in New York. In an email, the company told suppliers to hold off on breaking ground on new construction projects. 

The move is a concerning one at a crucial time for EV charging infrastructure. Right now, there are nowhere near enough chargers installed in the US to support a shift to electric vehicles. If EVs make up half of new-car sales by the end of the decade, we’ll need roughly 1.2 million public chargers installed by then, according to a 2023 study from the National Renewable Energy Laboratory. Today, the country has 170,000 charging ports available. 

In a recent poll, nearly 80% of US adults said that a lack of charging infrastructure is a primary reason for not buying an EV. That was true whether they lived in a city, in the suburbs, or in more rural areas.

In a way, it does make sense that Tesla appears to be uninterested in being the one to build out a public charging network. Chargers are costly to build and maintain, and they might not be all that profitable in the near term. 

According to analysis by BNEF, Tesla pulled in about $1.7 billion from charging last year, only about 1.5% of the company’s total revenue. Opening up chargers to vehicles from other automakers could help push revenue from this source up to $7.4 billion annually by the end of the decade. But that’s still a relatively small piece of Tesla’s total potential pie. 

Musk seems more interested in pursuing buzzy ideas like robotaxis than doing the difficult and expensive work of providing EV charging as a public service. 

Honestly, I think this move is a wake-up call for the EV industry. Tesla has played an undeniable role in bringing EVs to the mainstream. But we’re in a new stage of the game now, one that’s less about sleek sports cars and more about deploying known technologies and keeping them working. 

Other companies may step in to help fill the charging gap Tesla is opening. Revel expressed interest in taking over those canceled leases in New York City, for instance. But I wouldn’t hold my breath for a shiny new company to be our charging hero. 

Cutting emissions and remaking our economy will require buckling down to deploy and maintain solutions that we already know work, whether that’s in transportation or any other sector. For EV charging, and for climate technology as a whole, we need more than Tesla. Here’s hoping we can get it. 

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Related reading

Perhaps the single biggest remaining barrier to EV adoption is a lack of charging infrastructure, as I wrote in a newsletter last year.

We need way more chargers to support the number of new EVs that are expected to hit the roads this decade. I dug into how many for a news story last year.

New battery technology could help EV batteries charge even faster. Learn what could be coming next in this story from August.

Another thing

Meat is a major climate problem. Whether solutions come in the form of plant-based alternatives or products grown in the lab, we shouldn’t expect them to solve every problem under the sun, argues my colleague James Temple, in a new essay published this week. Give it a read! 

Keeping up with climate  

Alternative jet fuels have a corn problem. The crop can be used to make fuels that qualify for tax credits in the US, but critics are skeptical about just how helpful they’ll be in efforts to cut emissions. (MIT Technology Review)

This startup is making fuel from carbon dioxide. Infinium’s Texas facility came online in late 2023, and its synthetic fuels could help clean up aviation and trucking—but only if the price is right. (Bloomberg)

New York City pizza shops are going electric. A citywide ordinance just went into effect that requires wood- and coal-burning ovens to cut their pollution, and many are turning to electric ovens instead of undertaking the costly upgrade. (New York Times)

Building a new energy system happens one project at a time. I loved this list of 10 potentially make-or-break projects that represent the potential future of our grid. (Heatmap)

→ The list includes a new site from Fervo in Utah, expected in 2026. Get the inside look at the company’s technology in this feature story from last year. (MIT Technology Review)

Funding for climate-tech startups in Africa is growing, with businesses raising more than $3.4 billion since 2019. But there’s still a long way to go to help the continent meet its climate goals. (Associated Press)

One very big, and very simple, thing is holding back heat pumps: a lack of workers. We need more people to make and install the appliances, which help cut emissions by using electricity to efficiently heat and cool spaces. (Wired)

→ Heat pumps are booming, and they’re on our list of 2024 Breakthrough Technologies. (MIT Technology Review)

Compressing air and storing it underground could help clean up the grid. Yes, really. Canadian company Hydrostor is close to breaking ground on its first large long-duration energy storage project later this year in Australia. (Inside Climate News)

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

Batteries are on my mind this week. (Aren’t they always?) But I’ve got two extra reasons to be thinking about them today. 

First, there’s a new special report from the International Energy Agency all about how crucial batteries are for our future energy systems. The report calls batteries a “master key,” meaning they can unlock the potential of other technologies that will help cut emissions. Second, we’re seeing early signs in California of how the technology might be earning that “master key” status already by helping renewables play an even bigger role on the grid. So let’s dig into some battery data together. 

1) Battery storage in the power sector was the fastest-growing commercial energy technology on the planet in 2023. 

Deployment doubled over the previous year’s figures, hitting nearly 42 gigawatts. That includes utility-scale projects as well as projects installed “behind the meter,” meaning they’re somewhere like a home or business and don’t interact with the grid. 

Over half the additions in 2023 were in China, which has been the leading market in batteries for energy storage for the past two years. Growth is faster there than the global average, and installations tripled from 2022 to last year. 

One driving force of this quick growth in China is that some provincial policies require developers of new solar and wind power projects to pair them with a certain level of energy storage, according to the IEA report.

Intermittent renewables like wind and solar have grown rapidly in China and around the world, and the technologies are beginning to help clean up the grid. But these storage requirement policies reveal the next step: installing batteries to help unlock the potential of renewables even during times when the sun isn’t shining and the wind isn’t blowing. 

2) Batteries are starting to show exactly how they’ll play a crucial role on the grid.

When there are small amounts of renewables, it’s not all that important to have storage available, since the sun’s rising and setting will cause little more than blips in the overall energy mix. But as the share increases, some of the challenges with intermittent renewables become very clear. 

We’ve started to see this play out in California. Renewables are able to supply nearly all the grid’s energy demand during the day on sunny days. The problem is just how different the picture is at noon and just eight hours later, once the sun has gone down. 

In the middle of the day, there’s so much solar power available that gigawatts are basically getting thrown away. Electricity prices can actually go negative. Then, later on, renewables quickly fall off, and other sources like natural gas need to ramp up to meet demand. 

But energy storage is starting to catch up and make a dent in smoothing out that daily variation. On April 16, for the first time, batteries were the single greatest power source on the grid in California during part of the early evening, just as solar fell off for the day. (Look for the bump in the darkest line on the graph above—it happens right after 6 p.m.)

Batteries have reached this number-one status several more times over the past few weeks, a sign that the energy storage now installed—10 gigawatts’ worth—is beginning to play a part in a balanced grid. 

3) We need to build a lot more energy storage. Good news: batteries are getting cheaper.

While early signs show just how important batteries can be in our energy system, we still need gobs more to actually clean up the grid. If we’re going to be on track to cut greenhouse-gas emissions to zero by midcentury, we’ll need to increase battery deployment sevenfold. 

The good news is the technology is becoming increasingly economical. Battery costs have fallen drastically, dropping 90% since 2010, and they’re not done yet. According to the IEA report, battery costs could fall an additional 40% by the end of this decade. Those further cost declines would make solar projects with battery storage cheaper to build than new coal power plants in India and China, and cheaper than new gas plants in the US. 

Batteries won’t be the magic miracle technology that cleans up the entire grid. Other sources of low-carbon energy that are more consistently available, like geothermal, or able to ramp up and down to meet demand, like hydropower, will be crucial parts of the energy system. But I’m interested to keep watching just how batteries contribute to the mix. 

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Now read the rest of The Spark

Related reading

Some companies are looking beyond lithium for stationary energy storage. Dig into the prospects for sodium-based batteries in this story from last year.

Lithium-sulfur technology could unlock cheaper, better batteries for electric vehicles that can go farther on a single charge. I covered one company trying to make them a reality earlier this year.

Another thing

Thermal batteries are so hot right now. In fact, readers chose the technology as our 11th Breakthrough Technology of 2024.

To celebrate, we’re hosting an online event in a couple of weeks for subscribers. We’ll dig into why thermal batteries are so interesting and why this is a breakthrough moment for the technology. It’s going to be a lot of fun, so subscribe if you haven’t already and then register here to join us on May 16 at noon Eastern time.

You’ll be able to submit a question when you register—please do that so I know what you want to hear about! See you there! 

Keeping up with climate  

New rules that force US power plants to slash emissions could effectively spell the end of coal power in the country. Here are five things to know about the regulations. (New York Times)

Wind farms use less land than you might expect. Turbines really take up only a small fraction of the land where they’re sited, and co-locating projects with farms or other developments can help reduce environmental impact. (Washington Post)

The fourth reactor at Plant Vogtle in Georgia officially entered commercial operation this week. The new reactor will provide electricity for up to 500,000 homes and businesses. (Axios) 

A new factory will be the first full-scale plant to produce sodium-ion batteries in the US. The chemistry could provide a cheaper alternative to the standard lithium-ion chemistry and avoid material constraints. (Bloomberg)

→ I wrote about the potential for sodium-based batteries last year. (MIT Technology Review)

Tesla has apparently laid off a huge portion of its charging team. The move comes as the company’s charging port has been adopted by most major automakers. (The Verge)

A vegan cheese was up for a major food award. Then, things got messy. (Washington Post)

→ For a look at how Climax Foods makes its plant-based cheese with AI, check out this story from our latest magazine issue. (MIT Technology Review)

Someday mining might be done with … seaweed? Early research is looking into using seaweed to capture and concentrate high-value metals. (Hakai)

The planet’s oceans contain enormous amounts of energy. Harnessing it is an early-stage industry, but some proponents argue there’s a role for wave and tidal power technologies. (Undark)

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

From toaster ovens that work as air fryers to hair dryers that can also curl your hair, single tools that do multiple jobs have an undeniable appeal. 

In the climate world, hydrogen is perhaps the ultimate multi-tool. It can be used in fuel cells or combustion engines and is sometimes called the Swiss Army knife for cleaning up emissions. I’ve written about efforts to use hydrogen in steelmaking, cars, and aviation, just to name a few. And a new story for our latest print issue explores the potential of hydrogen trains. 

Hydrogen might be a million tools in one, but some experts argue that it can’t do it all, and some uses could actually be distractions from real progress on emissions. So let’s dig into where we might see hydrogen used and where it might make the biggest emissions cuts. 

Hydrogen could play a role in cleaning up nearly every sector of the economy—in theory. The reality today is that hydrogen is much more of a climate problem than a solution.

Most hydrogen is used in oil refining, chemical production, and heavy industry, and it is almost exclusively generated using fossil fuels. In total, hydrogen production and use accounted for around 900 million metric tons of carbon dioxide emissions in 2022.

There are technologies on the table to clean up hydrogen production. But global hydrogen demand hit 95 million metric tons in 2022, and only about 0.7% of that was met with low-emissions hydrogen. (For more on various hydrogen sources and why the details matter, check out this newsletter from last year.) 

Transforming the global hydrogen economy won’t be fast or cheap, but it is happening. Annual production of low-emissions hydrogen is on track to hit 38 million metric tons by 2030, according to the International Energy Agency. The pipeline of new projects is growing quickly, but so is hydrogen demand, which could hit 150 million metric tons by the end of the decade. 

Basically every time I report on hydrogen, whether in transportation or energy or industry, experts tell me it’s crucial to be smart about where that low-emissions hydrogen is going. There are, of course, disagreements about what exactly the order of priorities should be, but I’ve seen a few patterns.

First, the focus should probably be on cleaning up production of the hydrogen we’re already using for things like fertilizer. “The main thing is replacing existing uses,” as Geert de Cock, electricity and energy manager at the European Federation for Transport and Environment, put it when I spoke with him earlier this year for a story about hydrogen cars.  

Beyond that, though, hydrogen will probably be most useful in industries where there aren’t other practical options already on the table. 

That’s a central idea behind an infographic I think about a lot: the Hydrogen Ladder, conceptualized and updated frequently by Michael Liebreich, founder of BloombergNEF. In this graphic, he basically ranks just about every use of hydrogen, from “unavoidable” uses at the top to “uncompetitive” ones at the bottom. His metrics include cost, convenience, and economics. 

At the top of this ladder are existing uses and industries where there’s no alternative to hydrogen. There, Liebrich agrees with most experts I’ve spoken with about hydrogen. 

On the next few rungs come sectors where there’s still no dominant technical solution for cleaning up emissions, like shipping, aviation, and steel production. You might recognize these as famously “hard to solve” sectors. 

Heavy industry often requires high temperatures, which have historically been expensive to achieve with electricity. Cost and technical challenges have pushed companies to explore using hydrogen in processes like steelmaking. For shipping and aviation, there are strict limitations on the mass and size of the fueling system, and batteries can’t make the cut just yet, leaving hydrogen a potential opening. 

Toward the bottom of Liebreich’s ladder are applications where we already have clear decarbonization options available today, making hydrogen a long shot. Take domestic heating, for example. Heat pumps are breaking through in a massive way (we put them on our list of 10 Breakthrough Technologies this year), so hydrogen has some stiff competition there. 

Cars also rank right at the bottom of the ladder, alongside two- and three-wheeled vehicles, since battery-powered transit is becoming increasingly popular and charging infrastructure is growing. That leaves little room for hydrogen vehicles to make a dent, at least in the near future.

I’m not counting hydrogen out as a fuel for any one use, and there’s plenty of room to disagree on particular uses and their particular rungs. But given that we have a growing number of options in our arsenal to fight climate change, I’m betting that as a general rule, hydrogen will find its niches rather than emerge as the magic multi-tool that saves us all.

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Related reading

A fight over hydrogen trains reveals that cleaning up transportation is a political problem as much as it is a technical one. Read more in this story from Benjamin Schneider, featured in our latest magazine issue. 

Where hydrogen comes from matters immensely when it comes to climate impacts. Read more in this newsletter from last year.

Hydrogen is losing the race to cut emissions from cars, and I explored why for a story earlier this year. 

Another thing

It’s here! The Build issue of our print magazine just dropped, and it’s a good one. 

Dive into this story about how artificial snowdrifts could help protect seal pups from climate change. Volunteers in Finland brave freezing temperatures to help create an environment for endangered seals to thrive. 

Or if you’re feeling hungry, I’d recommend this look at how Climax Foods is using machine learning to create vegan cheeses that can stand up to discerning palates. (I have tasted these and can attest that some of them are truly uncanny.) 

Find the full issue here. Happy reading! 

Keeping up with climate  

A solar giant is moving manufacturing to the US. Tariffs and tax incentives are reshaping the solar market, but things could get challenging fast, as my colleague Zeyi Yang reported this week. (MIT Technology Review)

In a new op-ed, Daniele Visioni makes the case that proposals to crack down on geoengineering are misguided. He calls for more research, including outdoor experiments, to make better decisions about climate interventions. (MIT Technology Review)

Americans have some surprising feelings about EVs. And in a recent survey, fewer than half of US adults said they think EVs are better for the climate than gas-powered ones. (Sustainability by numbers)

An Australian supplier of fast charging equipment for EVs is in financial trouble. Tritium told regulators that it’s insolvent, and it’s unclear whether the company will be able to fill orders or service existing chargers. (Canary Media)

Offshore wind has faced its fair share of challenges, but the death of a mega-turbine may have played a major role. GE Vernova canceled plans for a 18-megawatt machine, causing ripples that ended in New York’s move to cancel contracts for three massive projects last week. (E&E News)

The UK’s final coal power station is set to close within the year. Here’s a look at the last site generating what used to be the country’s main source of energy. (The Guardian)

Is it time to retire the term “clean energy”? The term is a convenient way to roll up energy sources that cut emissions, like renewables and nuclear power, but some argue that it glosses over environmental harms. (Inside Climate News)

California saw batteries become the single largest source of power on the grid one evening last week—a major moment for energy storage. (Heatmap News)

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

The votes have been tallied, and the results are in. The winner of the 11th Breakthrough Technology, 2024 edition, is … drumroll please … thermal batteries! 

While the editors of MIT Technology Review choose the annual list of 10 Breakthrough Technologies, in 2022 we started having readers weigh in on an 11th technology. And I don’t mean to flatter you, but I think you picked a fascinating one this year. 

Thermal energy storage is a convenient way to stockpile energy for later. This could be crucial in connecting cheap but inconsistent renewable energy with industrial facilities, which often require a constant supply of heat. 

I wrote about why this technology is having a moment, and where it might wind up being used, in a story published Monday. For the newsletter this week, let’s take a deeper look at the different kinds of thermal batteries out there, because there’s a wide world of possibilities. 

Step 1: Choose your energy source

In the journey to build a thermal battery, the crucial first step is to choose where your heat comes from. Most of the companies I’ve come across are building some sort of power-to-heat system, meaning electricity goes in and heat comes out. Heat often gets generated by running a current through a resistive material in a process similar to what happens when you turn on a toaster.

Some projects may take electricity directly from sources like wind turbines or solar panels that aren’t hooked up to the grid. That could reduce energy costs, since you don’t have to pay surcharges built into grid electricity rates, explains Jeffrey Rissman, senior director of industry at Energy Innovation, a policy and research firm specializing in energy and climate. 

Otherwise, thermal batteries can be hooked up to the grid directly. These systems could allow a facility to charge up when electricity prices are low or when there’s a lot of renewable energy on the grid. 

Some thermal storage systems are soaking up waste heat rather than relying on electricity. Brenmiller Energy, for example, is building thermal batteries that can be charged up with heat or electricity, depending on the customer’s needs. 

Depending on the heat source, systems using waste heat may not be able to reach temperatures as high as their electricity-powered counterparts, but they could help increase the efficiency of facilities that would otherwise waste that energy. There’s especially high potential for high-temperature processes, like cement and steel production. 

Step 2: Choose your storage material

Next up: pick out a heat storage medium. These materials should probably be inexpensive and able to reach and withstand high temperatures. 

Bricks and carbon blocks are popular choices, as they can be packed together and, depending on the material, reach temperatures well over 1,000 °C (1,800 °F). Rondo Energy, Antora Energy, and Electrified Thermal Solutions are among the companies using blocks and bricks to store heat at these high temperatures. 

Crushed-up rocks are another option, and the storage medium of choice for Brenmiller Energy. Caldera is using a mixture of aluminum and crushed rock. 

Molten materials can offer even more options for delivering thermal energy later, since they can be pumped around (though this can also add more complexity to the system). Malta is building thermal storage systems that use molten salt, and companies like Fourth Power are using systems that rely in part on molten metals. 

Step 3: Choose your delivery method

Last, and perhaps most important, is deciding how to get energy back out of your storage system. Generally, thermal storage systems can deliver heat, use it to generate electricity, or go with some combination of the two. 

Delivering heat is the most straightforward option. Typically, air or another gas gets blown over the hot thermal storage material, and that heated gas can be used to warm up equipment or to generate steam. 

Some companies are working to use heat storage to deliver electricity instead. This could allow thermal storage systems to play a role not only in industry but potentially on the electrical grid as an electricity storage solution. One downside? These systems generally take a hit on efficiency, the amount of energy that can be returned from storage. But they may be right for some situations, such as facilities that need both heat and electricity on demand. Antora Energy is aiming to use thermophotovoltaic materials to turn heat stored in its carbon blocks back into electricity. 

Some companies plan to offer a middle path, delivering a combination of heat and electricity, depending on what a facility needs. Rondo Energy’s heat batteries can deliver high-pressure steam that can be used either for heating alone or to generate some electricity using cogeneration units. 

The possibilities are seemingly endless for thermal batteries, and I’m seeing new players with new ideas all the time. Stay tuned for much more coverage of this hot technology (sorry, I had to). 

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Related reading

Read more about why thermal batteries won the title of 11th breakthrough technology in my story from Monday.

I first wrote about heat as energy storage in this piece last year. As I put it then: the hottest new climate technology is bricks. 

Companies have made some progress in scaling up thermal batteries—our former fellow June Kim wrote about one new manufacturing facility in October.

Another thing

The state of Louisiana in the southeast US has lost over a million acres of its coast to erosion. A pilot project aims to save some homes in the state by raising them up to avoid the worst of flooding. 

It’s an ambitious attempt to build a solution to a crisis, and the effort could help keep communities together. But some experts worry that elevation projects offer too rosy an outlook and think we need to focus on relocation instead. Read more in this fascinating feature story from Xander Peters.

Keeping up with climate  

It can be easy to forget, but we’ve actually already made a lot of progress on addressing climate change. A decade ago, the world was on track for about 3.7 °C of warming over preindustrial levels. Today, it’s 2.7 °C with current actions and policies—higher than it should be but lower than it might have been. (Cipher News)

We’re probably going to have more batteries than we actually need for a while. Today, China alone makes enough batteries to satisfy global demand, which could make things tough for new players in the battery game. (Bloomberg) 

2023 was a record year for wind power. The world installed 117 gigawatts of new capacity last year, 50% more than the year before. (Associated Press)

→ Here’s what’s coming next for offshore wind. (MIT Technology Review)

Coal power grew in 2023, driven by a surge of new plants coming online in China and a slowdown of retirements in Europe and the US. (New York Times)

People who live near solar farms generally have positive feelings about their electricity-producing neighbors. There’s more negative sentiment among people who live very close to the biggest projects, though. (Inside Climate News)

E-scooters have been zipping through city streets for eight years, but they haven’t exactly ushered in the zero-emissions micro-mobility future that some had hoped for. Shared scooters can cut emissions, but it all depends on rider behavior and company practices. (Grist)

The grid could use a renovation. Replacing existing power lines with new materials could double grid capacity in many parts of the US, clearing the way for more renewables. (New York Times) 

The first all-electric tugboat in the US is about to launch in San Diego. The small boats are crucial to help larger vessels in and around ports, and the fossil-fuel-powered ones are a climate nightmare. (Canary Media)

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

Usually when we talk about climate change, the focus is squarely on the role that greenhouse-gas emissions play in driving up global temperatures, and rightly so. But another important, less-known phenomenon is also heating up the planet: reductions in other types of pollution.

In particular, the world’s power plants, factories, and ships are pumping much less sulfur dioxide into the air, thanks to an increasingly strict set of global pollution regulations. Sulfur dioxide creates aerosol particles in the atmosphere that can directly reflect sunlight back into space or act as the “condensation nuclei” around which cloud droplets form. More or thicker clouds, in turn, also cast away more sunlight. So when we clean up pollution, we also ease this cooling effect. 

Before we go any further, let me stress: cutting air pollution is smart public policy that has unequivocally saved lives and prevented terrible suffering. 

The fine particulate matter produced by burning coal, gas, wood, and other biomatter is responsible for millions of premature deaths every year through cardiovascular disease, respiratory illnesses, and various forms of cancer, studies consistently show. Sulfur dioxide causes asthma and other respiratory problems, contributes to acid rain, and depletes the protective ozone layer. 

Air pollution is killing millions of people per year.

It would be a vastly better outcome for humanity if we could cut it rapidly, despite the resulting warming impact on the climate. https://t.co/JYWAWwVtiG

— Zeke Hausfather (@hausfath) April 8, 2024

But as the world rapidly warms, it’s critical to understand the impact of pollution-fighting regulations on the global thermostat as well. Scientists have baked the drop-off of this cooling effect into net warming projections for the coming decades, but they’re also striving to obtain a clearer picture of just how big a role declining pollution will play.

A new study found that reductions in emissions of sulfur dioxide and other pollutants are responsible for about 38%, as a middle estimate, of the increased “radiative forcing” observed on the planet between 2001 and 2019. 

An increase in radiative forcing means that more energy is entering the atmosphere than leaving it, as Kerry Emanuel, a professor of atmospheric science at MIT, lays out in a handy explainer here. As that balance has shifted in recent decades, the difference has been absorbed by the oceans and atmosphere, which is what is warming up the planet. 

The remainder of the increase is “mainly” attributable to continued rising emissions of heat-trapping greenhouse gases, says Øivind Hodnebrog, a researcher at the Center for International Climate and Environment Research in Norway and lead author of the paper, which relied on climate models, sea-surface temperature readings, and satellite observations.

The study underscores the fact that as carbon dioxide, methane, and other gases continue to drive up temperature​​s, parallel reductions in air pollution are revealing more of that additional warming, says Zeke Hausfather, a scientist at the independent research organization Berkeley Earth. And it’s happening at a point when, by most accounts, global warming is about to begin accelerating or has already started to do so. (There’s ongoing debate over whether researchers can yet detect that acceleration and whether the world is now warming faster than researchers had expected.)

Because of the cutoff date, the study did not capture a more recent contributor to these trends. Starting in 2020, under new regulations from the International Maritime Organization, commercial shipping vessels have also had to steeply reduce the sulfur content in fuels. Studies have already detected a decrease in the formation of “ship tracks,” or the lines of clouds that often form above busy shipping routes. 

Again, this is a good thing in the most important way: maritime pollution alone is responsible for tens of thousands of early deaths every year. But even so, I have seen and heard of suggestions that perhaps we should slow down or alter the implementation of some of these pollution policies, given the declining cooling effect.

A 2013 study explored one way to potentially balance the harms and benefits. The researchers simulated a scenario in which the maritime industry would be required to use very low-sulfur fuels around coastlines, where the pollution has the biggest effect on mortality and health. But then the vessels would double the fuel’s sulfur content when crossing the open ocean. 

In that hypothetical world, the cooling effect was a bit stronger and premature deaths declined by 69% with respect to figures at the time, delivering a considerable public health improvement. But notably, under a scenario in which low-sulfur fuels were required across the board, mortality declined by 96%, a difference of more than 13,000 preventable deaths every year.

Now that the rules are in place and the industry is running on low-sulfur fuels, intentionally reintroducing pollution over the oceans would be a far more controversial matter.

While society basically accepted for well over a century that ships were inadvertently emitting sulfur dioxide into the air, flipping those emissions back on for the purpose of easing global warming would amount to a form of solar geoengineering, a deliberate effort to tweak the climate system.

Many think such planetary interventions are far too powerful and unpredictable for us to muck around with. And to be sure, this particular approach would be one of the more ineffective, dangerous, and expensive ways to carry out solar geoengineering, if the world ever decided it should be done at all. The far more commonly studied concept is emitting sulfur dioxide high in the stratosphere, where it would persist for longer and, as a bonus, not be inhaled by humans. 

On an episode of the Energy vs. Climate podcast last fall, David Keith, a professor at the University of Chicago who has closely studied the topic, said that it may be possible to slowly implement solar geoengineering in the stratosphere as a means of balancing out the reduced cooling occurring from sulfur dioxide emissions in the troposphere.

“The kind of solar geoengineering ideas that people are talking about seriously would be a thin wedge that would, for example, start replacing what was happening with the added warming we have from unmasking the aerosol cooling from shipping,” he said. 

Positioning the use of solar geoengineering as a means of merely replacing a cruder form that the world was shutting down offers a somewhat different mental framing for the concept—though certainly not one that would address all the deep concerns and fierce criticisms.

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Read more from MIT Technology Review’s archive: 

Back in 2018, I wrote a piece about the maritime rules that were then in the works and the likelihood that they would fuel additional global warming, noting that we were “about to kill a massive, unintentional” experiment in solar geoengineering.

Another thing

Speaking of the concerns about solar geoengineering, late last week I published a deep dive into Harvard’s unsuccessful, decade-long effort to launch a high-altitude balloon to conduct a tiny experiment in the stratosphere. I asked a handful of people who were involved in the project or followed it closely for their insights into what unfolded, the lessons that can be drawn from the episode—and their thoughts on what it means for geoengineering research moving forward.

Keeping up with Climate 

Yup, as the industry predicted (and common sense would suggest), this week’s solar eclipse dramatically cut solar power production across North America. But for the most part, grid operators were able to manage their systems smoothly, minus a few price spikes, thanks in part to a steady buildout of battery banks and the availability of other sources like natural gas and hydropower. (Heatmap)

There’s been a pile-up of bad news for Tesla in recent days. First, the company badly missed analyst expectations for vehicle deliveries during the first quarter. Then, Reuters reported that the EV giant has canceled plans for a low-cost, mass-market car. That may have something to do with the move to “prioritize the development of a robotaxi,” which the Wall Street Journal then wrote about. Over on X, Elon Musk denied the Reuters story, sort of—posting that “Reuters is lying (again).” But there’s a growing sense that his transformation into a “far-right activist” is exacting an increasingly high cost on his personal and business brands. (Wall Street Journal)

In a landmark ruling this week, the European Court of Human Rights determined that by not taking adequate steps to address the dangers of climate change, including increasingly severe heat waves that put the elderly at particular risk, Switzerland had violated the human rights of a group of older Swiss women who had brought a case against the country. Legal experts say the ruling creates a precedent that could unleash many similar cases across Europe. (The Guardian)

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

Aging can be scary. As you get older, you might not be able to do everything you used to, and it can be hard to keep up with the changing times. Just ask nuclear reactors.

The average age of reactors in nuclear power plants around the world is creeping up. In the US, which has more operating reactors than any other country, the average reactor is 42 years old, as of 2023. Nearly 90% of reactors in Europe have been around for 30 years or more. 

Older reactors, especially smaller ones, have been shut down in droves due to economic pressures, particularly in areas with other inexpensive sources of electricity, like cheap natural gas. But there could still be a lot of life left in older nuclear reactors. 

The new owner of a plant in Michigan that was shut down in 2022 is now working to reopen it, as I reported in my latest story. If the restart is successful, the plant could operate for a total of 80 years. Others are seeing 20-year extensions to their reactors’ licenses. Extending the lifetime of existing nuclear plants could help cut emissions and is generally cheaper than building new ones. So just how long can we expect nuclear power plants to last? 

In the US, the Nuclear Regulatory Commission (NRC) licenses nuclear reactors for 40-year operating lifespans. But plants can certainly operate longer than that, and many do. 

The 40-year timeline wasn’t designed to put an endpoint on a plant’s life, says Patrick White, research director at the Nuclear Innovation Alliance, a nonprofit think tank. Rather, it was meant to ensure that plants would be able to operate long enough to make back the money invested in building them, he says. 

The NRC has granted 20-year license extensions to much of the existing US nuclear fleet, allowing them to operate for 60 years. Now some operators are applying for an additional extension. A handful of reactors have already been approved to operate for a total of 80 years, including two units at Turkey Point in Florida. Getting those extensions has been bumpy, though. The NRC has since partially walked back some of its approvals and is requiring several of the previously approved sites to go through additional environmental reviews using more recent data. 

And while the oldest operating reactors in the world today are only 54, there’s already early research investigating extending lifetimes to 100 years, White says. 

The reality is that a nuclear power plant has very few truly life-limiting components. Equipment like pumps, valves, and heat exchangers in the water cooling system and support infrastructure can all be maintained, repaired, or replaced. They might even get upgraded as technology improves to help a plant generate electricity more efficiently. 

Two main components determine a plant’s lifetime: the reactor pressure vessel and the containment structure, says Jacopo Buongiorno, a professor of nuclear engineering at MIT. 

• The reactor pressure vessel is the heart of a nuclear power plant, containing the reactor core as well as the associated cooling system. The structure must keep the reactor core at a high temperature and pressure without leaking. 

• The containment structure is a shell around the nuclear reactor. It is designed to be airtight and to keep any radioactive material contained in an emergency. 

Both components are crucial to the safe operation of a nuclear power plant and are generally too expensive or too difficult to replace. So as regulators examine applications for extending plant lifetimes, they are the most concerned about the condition and lifespan of those components, Buongiorno says. 

Researchers are searching for new ways to tackle issues that have threatened to take some plants offline, like the corrosion that chewed through reactor components in one Ohio plant, causing it to be closed for two years. New ways of monitoring the materials inside nuclear power plants, as well as new materials that resist degradation, could help reactors operate more safely, for longer. 

Extending the lifetime of nuclear plants could help the world meet clean energy and climate goals. 

In some places, shutting down nuclear power plants can result in more carbon pollution as fossil fuels are brought in to fill the gap. When New York shut down its Indian Point nuclear plant in 2021, natural gas use spiked and greenhouse gas emissions rose. 

Germany shut down the last of its nuclear reactors in 2023, and the country’s emissions have fallen to a record low, though some experts say most of that drop has more to do with an economic slowdown than increasing use of renewables like wind and solar. 

Extending the global nuclear fleet’s lifetime by 10 years would add 26,000 terawatt-hours of low carbon electricity to the grid over the coming decades, according to a report from the International Atomic Energy Agency. That adds up to roughly a year’s worth of current global electricity demand. That could help cut emissions while the world expands low-carbon power capacity. 

So when it comes to cleaning up the power grid, there’s value in respecting your elders, including nuclear reactors. 

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Now read the rest of The Spark

Related reading

A nuclear power plant in Michigan could be the first reactor in the US to reenter operation after shutting down, as I wrote in my latest story. 

Germany shut down the last of its nuclear reactors in 2023 after years of controversy in the country. Read more in our newsletter from last April.  

The next generation of nuclear reactors is getting more advanced. Kairos Power is working on cooling its reactors with salt instead of pressurized water, as I reported in January. 

Another thing

A total solar eclipse will sweep across the US on Monday, April 8. Yes, it will affect solar power, especially in states like Texas that have installed a lot of solar capacity since the 2017 eclipse. No, it probably won’t be a big issue for utilities, which are able to plan far in advance for the short dip in solar capacity. Read more in this story from Business Insider. 

Keeping up with climate  

Tesla’s EV sales slipped in the first quarter compared to last year. The automaker still outsold Chinese EV giant BYD, which briefly held the crown for EV sales in late 2023. (New York Times)

A startup is making cleaner steel in a commercial prototype. Electra wants to help tackle the 7% of global emissions that come from producing the material. (Bloomberg)

Burying plant waste can help remove carbon dioxide from the atmosphere. But there are problems with biomass burial, a growing trend in carbon removal. (Canary Media)

Shareholders are voting on whether recycling labels on Kraft Heinz products are deceptive. It’s part of a growing pushback against companies overselling the recyclability of their packaging. (Inside Climate News)

→ Think your plastic is being recycled? Think again. (MIT Technology Review)

Soil in Australia is shaping up to be a major climate problem. While soil is often pitched as a way to soak up carbon emissions, agriculture practices and changing weather conditions are turning things around. (The Guardian)

Two climate journalists attempted to ditch natural gas in their home. But electrification turned into quite the saga, illustrating some of the problems with efforts to decarbonize buildings. (Grist)

Solar panels are getting so cheap, some homes in Europe are sticking them on fences. With costs having more to do with installation than the cost of solar panels, we could see them going up in increasingly quirky places. (Financial Times)

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

If you’ve ever eaten at a fusion restaurant or seen an episode of Glee, you know a mashup can be a wonderful thing. 

Plug-in hybrid vehicles should be the mashup that the auto industry needs right now. They can run a short distance on a small battery in electric mode or take on longer drives with a secondary fuel, cutting emissions without asking people to commit to a fully electric vehicle.

But all that freedom can come with a bit of a complication: plug-in hybrids are what drivers make them. That can wind up being a bad thing because people tend to use electric mode less than expected, meaning emissions from the vehicles are higher than anticipated, as I covered in my latest story.

So are you a good match for a plug-in hybrid? Here’s what you should know about the vehicles.

Electric range is limited, and conditions matter

Plug-in hybrids have a very modest battery, and that’s reflected in their range. Models for sale today can generally get somewhere between 25 and 40 miles of electric driving (that’s 40 to 65 kilometers), with a few options getting up to around the 50-mile (80 km) mark.

But winter conditions can cut into that range. Even gas-powered vehicles see fuel economy drop in cold weather, but electric vehicles tend to take a harder hit. Battery-powered vehicles can see a 25% reduction in range in freezing temperatures, or even more depending on how hard the heaters need to work and what sort of driving you’re doing.

In the case of a plug-in hybrid with a small battery, these range cuts can be noticeable even for modest commutes. I spoke with one researcher for a story in 2022 who told me that he uses his plug-in hybrid in electric mode constantly for about nine months out of the year. Charging once overnight gets him to and from his job most of the time, but in the winter, his range shrinks enough to require gas for part of the trip.

It might not be a problem for you lucky folks in California or the south of Spain, but if you’re in a colder climate, you might want to take these range limitations into account. Parking in a warmer place like a garage can help, and you can even preheat your vehicle while it’s plugged in to extend your range.

Charging is a key consideration

Realistically, if you don’t have the ability to charge consistently at home, a plug-in hybrid may not be the best choice for you.

EV drivers who don’t live in single-family homes with attached garages can get creative with charging. Some New York City drivers I’ve spoken with rely entirely on public fast chargers, stopping for half an hour or so to juice up their vehicles as needed.

But plug-in hybrids generally aren’t equipped to handle fast charging speeds, so forget about plugging in at a Supercharger. The vehicles are probably best for people who have access to a charger at home, in a parking garage, or at work. Depending on battery capacity, charging a plug-in hybrid can take about eight hours on a level 1 charger, and two to three hours on a level 2 charger. 

Most drivers with plug-in hybrids wind up charging them less than what official estimates suggest. That means on average, drivers are producing more emissions than they might expect and probably spending more on fuel, too. For more on setting expectations around plug-in hybrids, read more in my latest story here.

We could see better plug-in models soon (in some places, at least)

For US drivers, state regulations could mean that plug-in offerings could expand soon.  

California recently adopted rules that require manufacturers to sell a higher proportion of low-emissions vehicles. Beginning in 2026, automakers will need clean vehicles to represent 35% of sales, ramping up to 100% in 2035. Several other states have hopped on board with the regulations, including New York, Massachusetts, and Washington.

Plug-in hybrids can qualify under the California rules, but only if they have at least 50 miles (80 km) of electric driving range. That means that we could be seeing more long-range plug-in options very soon, says Aaron Isenstadt, a senior researcher at the International Council on Clean Transportation.

Some other governments aren’t supporting plug-in hybrids, or are actively pushing drivers away from the vehicles and toward fully electric options. The European Union will end sales of gas-powered cars in 2035, including all types of hybrids.

Ultimately, plug-in hybrid vehicles can help reduce emissions from road transportation in the near term, especially for drivers who aren’t ready or willing to make the jump to fully electric cars just yet. But eventually, we’ll need to move on from compromises to fully zero-emissions options.  

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Now read the rest of The Spark

Related reading

Real-world driving habits can get in the way of the theoretical benefits of plug-in hybrids. For more on why drivers might be the problem, give my latest story a read. 

Plug-in hybrids probably aren’t going away anytime soon, as I wrote in December 2022. 

Still have questions about hybrids and electric vehicles? I answered a few of them for a recent newsletter. Check it out here.

Another thing

China has emerged as a dominant force in climate technology, especially in the world of electric vehicles. If you want to dig into how that happened, and what it means for the future of addressing climate change, check out the latest in our Roundtables series here. 

For a sampling of what my colleagues got into in this conversation, check out this story from Zeyi Yang about how China came to lead the world in EVs, and this one about how EV giant BYD is getting into shipping. 

Keeping up with climate  

The US Department of Energy just awarded $6 billion to 33 projects aimed at decarbonizing industry, from cement and steel to paper and food. (Canary Media)

→ Among the winners: Sublime Systems and Brimstone, two startups working on alternative cement. Read more about climate’s hardest problem in my January feature story. (MIT Technology Review)

In the latest in concerning insurance news, State Farm announced it won’t be renewing policies for 72,000 property owners in California. As fire seasons get worse, insuring properties gets riskier. (Los Angeles Times)

Surprise! Big fossil-fuel companies aren’t aligned with goals to limit global warming. A think tank assessed the companies’ plans and found that despite splashy promises, none of the 25 largest oil and gas companies meet targets set by the Paris Agreement. (The Guardian)

An AI model can predict flooding five days in advance. This and other AI tools could help better forecast dangerous scenarios in remote places with fewer flood gauges. (Bloomberg)

Boeing’s 737 Max planes have been all over the news with incidents including a door flying off on a recent Alaska Airlines flight. Some experts say the problems can be traced back in part to the company’s corner-cutting on sustainability efforts. (Heated)

In Denver, e-bike vouchers get snapped up like Taylor Swift tickets. The city is aiming to lower the cost of the vehicles for residents in an effort to reduce the total number of car trips. It’s obviously a popular program, though some experts question whether the funding could be more effective elsewhere. (Grist)

A nuclear plant in New York was shut down in 2021—and predictably, emissions went up. It’s been a step back for clean energy in the state, as natural gas has stepped in to fill the gap. (The Guardian)

Germany used to be a solar superpower, but China has come to dominate the industry. Some domestic manufacturers aren’t giving up just yet, arguing that local production will be key to meeting ambitious clean-energy goals. (New York Times)

A company will pour 9,000 tons of sand into the sea in the name of carbon removal. Vesta’s pilot project just got a regulatory green light, and it’ll be a big step for efforts to boost the ocean’s ability to soak up carbon dioxide from the atmosphere. (Heatmap)

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

Spend enough time in a city and you’ll get to know its unique soundscape. In New York City, it features the echoes of car stereos, the deep grumbles of garbage truck engines, and, increasingly, the high-pitched whirring of electric bikes.

E-bikes and scooters are becoming a staple across the city’s boroughs, and e-bikes in particular are especially popular among the tens of thousands of delivery workers who zip through the streets.

On a recent cloudy afternoon in Manhattan, I joined a few dozen of them at a sign-up event for a new city program that aims to connect delivery drivers with new charging technologies. Drivers who enroll in the pilot will have access to either fast chargers or battery swapping stations for six months.

It’s part of the city’s efforts to cut down on the risk of battery fires, some of which have been sparked by e-bike batteries charging inside apartment buildings, according to the fire department. For more on the program and how it might help address fires, check out my latest story. In the meantime, here’s what I heard from delivery drivers and the startups at the kickoff event.

On a windy late-February day, I wove my way through the lines of delivery workers who showed up to the event in Manhattan’s Cooper Square. Some of them straddled their bikes in line, while others propped up their bikes in clusters. Colorful bags sporting the logos of various delivery services sprouted from their cargo racks.

City officials worked at tables under tents, assigning riders to one of the three startups that are partnering with the city for the new program. One company, Swiftmile, is building fast-charging bike racks for drivers. The other two, Popwheels and Swobbee, are aiming to bring battery swapping to the city.

Battery swapping is a growing technology in some parts of the world, but it’s not common in the US, so I was especially intrigued by the two companies who had set up battery swap cabinets.

Swobbee runs a small network of swapping stations around the world, including at its base in Germany. It is retrofitting bikes to accommodate its battery, which attaches to the rear of the bike. Popwheels is taking a slightly different approach, providing batteries that are already compatible with the majority of e-bikes delivery drivers use today, with little modification required.

I watched a Popwheels employee demonstrate the company’s battery swapping station to several newly enrolled drivers. Each one would approach the Popwheels cabinet, which is roughly the size and shape of a bookcase and has 16 numbered metal doors on the front. After they made a few taps on their smartphone, a door would swing open. Inside, there was space to slide in a used battery and a cord to plug into it. Once the battery was in the cabinet and the door had been shut, another door would open, revealing a fully charged e-bike battery the rider could unplug and slide out. Presto!

The whole process took just a minute or two—much quicker than waiting for a battery to charge. It’s similar to picking up a package from an automated locker in an upscale apartment building.

The crowd seemed to grow during the two hours I spent at the event, and the line stretched and squeezed closer to the edge of the sidewalk. I made a comment about the turnout to Baruch Herzfeld, Popwheels’ CEO and co-founder. “This is nothing,” he said. “There’s demand for 100,000 batteries in New York tomorrow.”

Indeed, New York City has roughly 60,000 delivery workers, many of whom rely on e-bikes to get around. And commuters and tourists might be interested in small, electrified vehicles. Meeting anything close to that sort of demand will take a whole lot more battery cabinets, as one can service just up to 50 riders, according to Popwheels’ estimates.

After they’d signed up and seen the battery swap demo, drivers who were ready to take batteries with them wheeled their bikes over to a few more startup employees, who helped make a slight tweak to a rail under their seats for the company’s batteries to slide into. Some adjustments required a bit of elbow grease, but I watched as one rider slid his new, freshly charged battery into place. He hopped on his bike and darted off into the bike lane, integrating into the flow of traffic.

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Now read the rest of The Spark

Related reading

For more on the city’s plans for battery swapping and how they might cut fire risk, give my latest story a read.

Gogoro, one of our 15 Climate Tech Companies to Watch in 2023, operates a huge network of battery swapping stations for electric scooters, largely in Asia.

Some companies think battery swapping is an option for larger electric vehicles, too. Here’s how one startup wants to use modular, swappable batteries to get more EVs on the road.

Another thing

Harvard researchers have given up on a long-running effort to conduct a solar geoengineering experiment. 

The idea behind the technique is a simple one: scatter particles in the upper atmosphere to scatter sunlight, counteracting global warming. But related research efforts have sparked controversy. Read more in my colleague James Temple’s latest story.

Keeping up with climate  

The Biden administration finalized strict new rules for vehicle tailpipe emissions. Under the regulations, EVs are expected to make up over half of new vehicle sales by 2030. (NPR)

The first utility-scale offshore wind farm in the US is officially up and running. It’s a bright spot that could signal a turning point for the industry. (Canary Media)

→ Here’s what’s next for offshore wind. (MIT Technology Review)

The UK has big plans for heat pumps, but installations aren’t moving nearly fast enough, according to a new report. Installations need to increase more than tenfold to keep pace with goals. (The Guardian)

States across the US are proposing legislation to ban lab-grown meat. It’s the latest escalation in an increasingly weird battle over a product that basically doesn’t exist yet. (Wired)

Low-cost EVs from Chinese automakers are pushing US-based companies to reconsider their electrification strategy. More affordable EV options? A girl can dream. (Bloomberg)

→ EV prices in the US are inching down, approaching parity with gas-powered vehicles. (Washington Post)

Goodbye greenwashing, hello “greenhushing”! Corporations are increasingly going radio silent on climate commitments. (Inside Climate News)

The Summer Olympics are fast approaching, and organizers in Paris are working to reduce the event’s climate impact. Think fewer new buildings, more bike lanes. (New York Times)

Early springs mean cherry blossoms are blooming earlier than ever. Warmer winters in the future could cause an even bigger problem. (Bloomberg)

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

If you follow papers in climate and energy for long enough, you’re bound to recognize some patterns. 

There are a few things I’ll basically always see when I’m sifting through the latest climate and energy research: one study finding that perovskite solar cells are getting even more efficient; another showing that climate change is damaging an ecosystem in some strange and unexpected way. And there’s always some new paper finding that we’re still underestimating methane emissions. 

That last one is what I’ve been thinking about this week, as I’ve been reporting on a new survey of methane leaks from oil and gas operations in the US. (Yes, there are more emissions than we thought there were—get the details in my story here.) But what I find even more interesting than the consistent underestimation of methane is why this gas is so tricky to track down. 

Methane is the second most abundant greenhouse gas in the atmosphere, and it’s responsible for around 30% of global warming so far. The good news is that methane breaks down quickly in the atmosphere. The bad news is that while it’s floating around, it’s a super-powerful greenhouse gas, way more potent than carbon dioxide. (Just how much more potent is a complicated question that depends on what time scale you’re talking about—read more in this Q&A.)

The problem is, it’s difficult to figure out where all this methane is coming from. We can measure the total concentration in the atmosphere, but there are methane emissions from human activities, there are natural methane sources, and there are ecosystems that soak up a portion of all those emissions (these are called methane sinks). 

Narrowing down specific sources can be a challenge, especially in the oil and gas industry, which is responsible for a huge range of methane leaks. Some are small and come from old equipment in remote areas. Other sources are larger, spewing huge amounts of the greenhouse gas into the atmosphere but only for short times. 

A lot of stories about tracking methane have been in the news recently, mostly because of a methane-hunting satellite launched earlier this month. It’s designed to track down methane using tools called spectrometers, which measure how light is reflected and absorbed. 

This is just one of a growing number of satellites that are keeping an eye on the planet for methane emissions. Some take a wide view, spotting which regions have high emissions. Other satellites are hunting for specific sources and can see within a few dozen meters where a leak is coming from. (If you want to read more about why there are so many methane satellites, I recommend this story from Emily Pontecorvo at Heatmap.)

But methane tracking isn’t just a space game. In a new study published in Nature, researchers used nearly a million measurements taken from airplanes flown over oil- and gas-producing regions to estimate total emissions. 

The results are pretty staggering: researchers found that, on average, roughly 3% of oil and gas production at the sites they examined winds up as methane emissions. That’s about three times the official government estimates used by the US Environmental Protection Agency. 

I spoke with one of the authors of the study, Evan Sherwin, who completed the research as a postdoc at Stanford. He compared the challenge of understanding methane leaks to the parable of the blind men and the elephant: there are many pieces of the puzzle (satellites, planes, ground-based detection), and getting the complete story requires fitting them all together. 

“I think we’re really starting to see an elephant,” Sherwin told me. 

That picture will continue to get clearer as MethaneSAT and other surveillance satellites come online and researchers get to sift through the data. And that understanding will be crucial as governments around the world race to keep promises about slashing methane emissions. 

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Now read the rest of The Spark

Related reading

For more on how researchers are working to understand methane emissions, give my latest story a read. 

If you’ve missed the news on methane-hunting satellites, check out this story about MethaneSAT from last month. 

Pulling methane out of the atmosphere could be a major boost for climate action. Some startups hope that spraying iron particles above the ocean could help, as my colleague James Temple wrote in December. 

Another thing

Making minor changes to airplane routes could put a significant dent in emissions, and a new study found that these changes could be cheap to implement. 

The key is contrails, thin clouds that planes produce when they fly. Minimizing contrails means less warming, and changing flight paths can reduce the amount of contrail formation. Read more about how in the latest from my colleague James Temple. 

Keeping up with climate  

New rules from the US Securities and Exchange Commission were watered down, cutting off the best chance we’ve had at forcing companies to reckon with the dangers of climate change, as Dara O’Rourke writes in a new opinion piece. (MIT Technology Review)

Yes, heat pumps slash emissions, even if they’re hooked up to a pretty dirty grid. Switching to a heat pump is better than heating with fossil fuels basically everywhere in the US. (Canary Media)

Rivian announced its new R2, a small SUV set to go on sale in 2026. The reveal signals a shift to focusing on mass-market vehicles for the brand. (Heatmap)

Toyota has focused on selling hybrid vehicles instead of fully electric ones, and it’s paying off financially. (New York Times)

→ Here’s why I wrote in December 2022 that EVs wouldn’t be fully replacing hybrids anytime soon. (MIT Technology Review)

Some scientists think we should all pay more attention to tiny aquatic plants called azolla. They can fix their own nitrogen and capture a lot of carbon, making them a good candidate for crops and even biofuels. (Wired)

New York is suing the world’s largest meat company. The company has said it’ll produce meat with no emissions by 2040, a claim that is false and misleading, according to the New York attorney general’s office. (Vox)

A massive fire in Texas has destroyed hundreds of homes. Climate change has fueled dry conditions, and power equipment sparked an intense fire that firefighters struggled to contain. (Grist)

→ Many of the homes destroyed in the blaze are uninsured, creating a tough path ahead for recovery. (Texas Tribune)

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

Hydropower is a staple of clean energy—the modern version has been around for over a century, and it’s one of the world’s largest sources of renewable electricity.

But last year, weather conditions caused hydropower to fall short in a major way, with generation dropping by a record amount. In fact, the decrease was significant enough to have a measurable effect on global emissions. Total energy-related emissions rose by about 1.1% in 2023, and a shortfall of hydroelectric power accounts for 40% of that rise, according to a new report from the International Energy Agency.

Between year-to-year weather variability and climate change, there could be rocky times ahead for hydropower. Here’s what we can expect from the power source and what it might mean for climate goals. 

Drying up

Hydroelectric power plants use moving water to generate electricity. The majority of plants today use dams to hold back water, creating reservoirs. Operators can allow water to flow through the power plant as needed, creating an energy source that can be turned on and off on demand. 

This dispatchability is a godsend for the grid, especially because some renewables, like wind and solar, aren’t quite so easy to control. (If anyone figures out how to send more sunshine my way, please let me know—I could use more of it.) 

But while most hydroelectric plants do have some level of dispatchability, the power source is still reliant on the weather, since rain and snow are generally what fills up reservoirs. That’s been a problem for the past few years, when many regions around the world have faced major droughts. 

The world actually added about 20 gigawatts of hydropower capacity in 2023, but because of weather conditions, the amount of electricity generated from hydropower fell overall.

The shortfall was especially bad in China, with generation falling by 4.9% there. North America also faced droughts that contributed to hydro’s troubles, partly because El Niño brought warmer and drier conditions. Europe was one of the few places where conditions improved in 2023—mostly because 2022 was an even worse year for drought on the continent.

As hydroelectric plants fell short, fossil fuels like coal and natural gas stepped in to fill the gap, contributing to a rise in global emissions. In total, changes in hydropower output had more of an effect on global emissions than the post-pandemic aviation industry’s growth from 2022 to 2023. 

A trickle

Some of the changes in the weather that caused falling hydropower output last year can be chalked up to expected yearly variation. But in a changing climate, a question looms: Is hydropower in trouble?

The effects of climate change on rainfall patterns can be complicated and not entirely clear. But there are a few key mechanisms by which hydropower is likely to be affected, as one 2022 review paper outlined: 

• Rising temperatures will mean more droughts, since warmer air sucks up more moisture, causing rivers, soil, and plants to dry out more quickly. 
• Winters will generally be warmer, meaning less snowpack and ice, which often fills up reservoirs in the early spring in places like the western US. 
• There’s going to be more variability in precipitation, with periods of more extreme rainfall that can cause flooding (meaning water isn’t stored neatly in reservoirs for later use in a power plant).

What all this will mean for electricity generation depends on the region of the world in question. One global study from 2021 found that around half of countries with hydropower capacity could expect to see a 20% reduction in generation once per decade. Another report focused on China found that in more extreme emissions scenarios, nearly a quarter of power plants in the country could see that level of reduced generation consistently. 

It’s not likely that hydropower will slow to a mere trickle, even during dry years. But the grid of the future will need to be prepared for variations in the weather. Having a wide range of electricity sources and tying them together with transmission infrastructure over wide geographic areas will help keep the grid robust and ready for our changing climate. 

Related reading

Droughts across the western US have been cutting into hydropower for years. Here’s how changing weather could affect climate goals in California.

While adaptation can help people avoid the worst impacts of climate change, there’s a limit to how much adapting can really help, as I found when I traveled to El Paso, Texas, famously called the “drought-proof city.”

Drought is creating new challenges for herders, who have to handle a litany of threats to their animals and way of life. Access to data could be key in helping them navigate a changing world.

Another thing

Chinese EVs have entered center stage in the ongoing tensions between the US and China. The vehicles could help address climate change, but the Biden administration is wary of allowing them into the market. There are two major motivations: security and the economy. Read more in my colleague Zeyi Yang’s latest newsletter here. 

Keeping up with climate  

A new satellite that launched this week will be keeping an eye on methane emissions. Tracking leaks of the powerful greenhouse gas could be key in addressing climate change. (New York Times)

→ This isn’t our first attempt at tracking greenhouse gases from space—but here’s how MethaneSAT is different from other methane-detecting satellites. (Heatmap)

Smarter charging of EVs could be essential to the grid of the future, and California is working on a new program to test it out. (Canary Media)

The magnets that power wind turbines nearly always wind up in a landfill. A new program aims to change that by supporting new methods of recycling. (Grist)

→ One company wants to do without the rare earth metals that are used in today’s powerful magnets. (MIT Technology Review)

Data centers burn through water to keep machinery cool. As more of the facilities pop up, in part to support AI tools like ChatGPT, they could stretch water supplies thin in some places. (The Atlantic)

No US state has been more enthusiastic about heat pumps than Maine. While it might seem an unlikely match—the appliances can lose some of their efficiency in the cold—the state is a success story for the technology. (New York Times)

New rules from the US Securities and Exchange Commission would require companies to report their emissions and expected climate risks. The final version is watered down from an earlier proposal, which would have included a wider variety of emissions. (Associated Press)