This story was originally published by Grist and is reproduced here as part of the Climate Desk collaboration.

The wheels on this bus do indeed go round and round. Its wipers swish. And its horn beeps. Hidden in its innards, though, is something special—a motor that doesn’t vroom but pairs with a burgeoning technology that could help the grid proliferate with renewable energy.

These new buses, developed by a company called Zum, ride clean and quiet because they’re fully electric. With them, California’s Oakland Unified School District just became the first major district in the United States to transition to 100 percent electrified buses.

The vehicles are now transporting 1,300 students to and from school, replacing diesel-chugging buses that pollute the kids’ lungs and the neighborhoods with particulate matter. Like in other American cities, Oakland’s underserved areas tend to be closer to freeways and industrial activity, so air quality in those areas is already terrible compared to the city’s richer parts.

Buses, garbage trucks, and other electric vehicles with defined routes can serve as reliable backup batteries during times of peak power demand.

Pollution from buses and other vehicles contributes to chronic asthma among students, which leads to chronic absenteeism. Since Oakland Unified only provides bus services for its special-need students, the problem of missing school for preventable health issues is particularly acute for them. “We have already seen the data—more kids riding the buses, that means more of our most vulnerable who are not missing school,” said Kyla Johnson-Trammell, superintendent of Oakland Unified School District, during a press conference Tuesday. “That, over time, means they’re having more learning and achievement goes up.”

What’s more, a core challenge of weaning our society off fossil fuels is that utilities will need to produce more electricity, not less of it. “In some places, you’re talking about doubling the amount of energy needed,” said Kevin Schneider, an expert in power systems at Pacific Northwest National Laboratory, who isn’t involved in the Oakland project. 

Counterintuitively enough, the buses’ massive batteries aren’t straining the grid; they’re benefiting it. Like a growing number of consumer EV models, the buses are equipped with vehicle-to-grid technology, or V2G. That allows them to charge their batteries by plugging into the grid, but also send energy back to the grid if the electrical utility needs extra power. “School buses play a very important role in the community as a transportation provider, but now also as an energy provider,” said Vivek Garg, co-founder and chief operating officer of Zum.

And provide the buses must. Demand on the grid tends to spike in the late afternoon, when everyone is returning home and switching on appliances like air conditioners. Historically, utilities could just spin up more generation at a fossil fuel power plant to meet that demand. But as the grid is loaded with more renewable energy sources, intermittency becomes a challenge: You can’t crank up power in the system if the sun isn’t shining or the wind isn’t blowing.

“We’re still going to need more generation, more power lines, but energy storage is going to give us the flexibility.”

If every EV has V2G capability, that creates a distributed network of batteries for a utility to draw on when demand spikes. The nature of the school bus suits it perfectly for this, because it’s on a fixed schedule, making it a predictable resource for the utility. In the afternoon, Zum’s buses take kids home, then plug back into the grid. “They have more energy in each bus than they need to do their route, so there’s always an ample amount left over,” said Rudi Halbright, product manager of V2G integration at Pacific Gas and Electric Company, the utility that’s partnered with Zum and Oakland Unified for the new system.

As the night goes on and demand wanes, the buses charge again to be ready for their morning routes. Then during the day, they charge again, when there’s plentiful solar power on the grid. On weekends or holidays, the buses would be available all day as backup power for the grid. “Sure, they’re going to take a very large amount of charge,” said Kevin Schneider, an expert in power systems at Pacific Northwest National Laboratory, who isn’t involved in the Oakland project. “But things like school buses don’t run that often, so they have a great potential to be a resource.”

That resource ain’t free: Utilities pay owners of V2G vehicles to provide power to the grid. (Because V2G is so new, utilities are still experimenting with what this rate structure looks like.) Zum says that that revenue helps bring down the transportation costs of its buses to be on par with cheaper diesel-powered buses. Oakland Unified and other districts can get still more money from the EPA’s Clean School Bus Program, which is handing out $5 billion between 2022 and 2026 to make the switch.

The potential of V2G is that there are so many different kinds of electric vehicles (or vehicle types left to electrify). Garbage trucks run early in the day, while delivery trucks and city vehicles do more of a nine-to-five. Passenger vehicles are kind of all over the place, with some people taking them to work, while others sit in garages all day. Basically, lots of batteries—big and small—parked idle at different times to send power back to the grid.

All the while, fiercer heat waves will require more energy-hungry air conditioning to keep people healthy. (Though ideally, everyone would get a heat pump instead.) “We’re still going to need more generation, more power lines, but energy storage is going to give us the flexibility so we can deploy it quicker,” Schneider said. In the near future, you may get home on a sweltering day and still be able to switch on your AC—thanks to an electric school bus sitting in a lot. 

This story was originally published by Grist and is reproduced here as part of the Climate Desk collaboration.

The wheels on this bus do indeed go round and round. Its wipers swish. And its horn beeps. Hidden in its innards, though, is something special—a motor that doesn’t vroom but pairs with a burgeoning technology that could help the grid proliferate with renewable energy.

These new buses, developed by a company called Zum, ride clean and quiet because they’re fully electric. With them, California’s Oakland Unified School District just became the first major district in the United States to transition to 100 percent electrified buses.

The vehicles are now transporting 1,300 students to and from school, replacing diesel-chugging buses that pollute the kids’ lungs and the neighborhoods with particulate matter. Like in other American cities, Oakland’s underserved areas tend to be closer to freeways and industrial activity, so air quality in those areas is already terrible compared to the city’s richer parts.

Buses, garbage trucks, and other electric vehicles with defined routes can serve as reliable backup batteries during times of peak power demand.

Pollution from buses and other vehicles contributes to chronic asthma among students, which leads to chronic absenteeism. Since Oakland Unified only provides bus services for its special-need students, the problem of missing school for preventable health issues is particularly acute for them. “We have already seen the data—more kids riding the buses, that means more of our most vulnerable who are not missing school,” said Kyla Johnson-Trammell, superintendent of Oakland Unified School District, during a press conference Tuesday. “That, over time, means they’re having more learning and achievement goes up.”

What’s more, a core challenge of weaning our society off fossil fuels is that utilities will need to produce more electricity, not less of it. “In some places, you’re talking about doubling the amount of energy needed,” said Kevin Schneider, an expert in power systems at Pacific Northwest National Laboratory, who isn’t involved in the Oakland project. 

Counterintuitively enough, the buses’ massive batteries aren’t straining the grid; they’re benefiting it. Like a growing number of consumer EV models, the buses are equipped with vehicle-to-grid technology, or V2G. That allows them to charge their batteries by plugging into the grid, but also send energy back to the grid if the electrical utility needs extra power. “School buses play a very important role in the community as a transportation provider, but now also as an energy provider,” said Vivek Garg, co-founder and chief operating officer of Zum.

And provide the buses must. Demand on the grid tends to spike in the late afternoon, when everyone is returning home and switching on appliances like air conditioners. Historically, utilities could just spin up more generation at a fossil fuel power plant to meet that demand. But as the grid is loaded with more renewable energy sources, intermittency becomes a challenge: You can’t crank up power in the system if the sun isn’t shining or the wind isn’t blowing.

“We’re still going to need more generation, more power lines, but energy storage is going to give us the flexibility.”

If every EV has V2G capability, that creates a distributed network of batteries for a utility to draw on when demand spikes. The nature of the school bus suits it perfectly for this, because it’s on a fixed schedule, making it a predictable resource for the utility. In the afternoon, Zum’s buses take kids home, then plug back into the grid. “They have more energy in each bus than they need to do their route, so there’s always an ample amount left over,” said Rudi Halbright, product manager of V2G integration at Pacific Gas and Electric Company, the utility that’s partnered with Zum and Oakland Unified for the new system.

As the night goes on and demand wanes, the buses charge again to be ready for their morning routes. Then during the day, they charge again, when there’s plentiful solar power on the grid. On weekends or holidays, the buses would be available all day as backup power for the grid. “Sure, they’re going to take a very large amount of charge,” said Kevin Schneider, an expert in power systems at Pacific Northwest National Laboratory, who isn’t involved in the Oakland project. “But things like school buses don’t run that often, so they have a great potential to be a resource.”

That resource ain’t free: Utilities pay owners of V2G vehicles to provide power to the grid. (Because V2G is so new, utilities are still experimenting with what this rate structure looks like.) Zum says that that revenue helps bring down the transportation costs of its buses to be on par with cheaper diesel-powered buses. Oakland Unified and other districts can get still more money from the EPA’s Clean School Bus Program, which is handing out $5 billion between 2022 and 2026 to make the switch.

The potential of V2G is that there are so many different kinds of electric vehicles (or vehicle types left to electrify). Garbage trucks run early in the day, while delivery trucks and city vehicles do more of a nine-to-five. Passenger vehicles are kind of all over the place, with some people taking them to work, while others sit in garages all day. Basically, lots of batteries—big and small—parked idle at different times to send power back to the grid.

All the while, fiercer heat waves will require more energy-hungry air conditioning to keep people healthy. (Though ideally, everyone would get a heat pump instead.) “We’re still going to need more generation, more power lines, but energy storage is going to give us the flexibility so we can deploy it quicker,” Schneider said. In the near future, you may get home on a sweltering day and still be able to switch on your AC—thanks to an electric school bus sitting in a lot. 

This story was originally published by Grist and is reproduced here as part of the Climate Desk collaboration.

After unleashing widespread flooding and knocking out electricity for half of Puerto Rico, this season’s third hurricane, Ernesto, has turned north and is approaching Bermuda. In an average Atlantic season, the third hurricane doesn’t spin up until September 7, so Ernesto has arrived way, way early. As of August 9, this summer had already produced a third of the activity in a typical season— with nearly 90 percent of it remaining.

All that makes Ernesto, now a Category 2 hurricane, an ominous sign of what’s still to come in the next few months—and what to expect as the planet rapidly warms. “Being a little more than three weeks ahead of schedule for the third hurricane is pretty impressive,” said Brian McNoldy, a hurricane researcher at the University of Miami.

This spring, scientists predicted that the Atlantic Ocean would play host to an exceptionally active hurricane season, with five major hurricanes and 21 named storms, for one particularly good reason—the ocean is exceptionally warm, and is expected to stay that way. In July, the nursery for Atlantic hurricanes was running 2.8 degrees Fahrenheit higher than the long-term average. “Hurricanes are a lot like engines—they need some sort of fuel,” said Daniel Gilford, who studies hurricanes at Climate Central, a nonprofit research organization. “They need something to be able to accelerate and pick up wind speed, and the thing they use to do that largely is the ocean surface.”

As water evaporates off the ocean, buoyant clouds form, releasing heat and lowering atmospheric pressure. That sucks in air, creating winds and a vortex. Hurricanes also love high humidity because dry air can slow the speed of the updrafts that the storms need to grow big and strong. Hurricanes hate wind shear—winds moving at different speeds and directions at different altitudes. El Niño tends to encourage the proliferation of wind shear over the Atlantic, while La Niña tends to discourage it. Right now the conditions are “neutral,” as El Niño has faded and La Niña has yet to officially form.

So warm ocean temperatures aren’t the only ingredient to make a hurricane, but they’re certainly the fuel. As Ernesto was chugging across the Atlantic between West Africa and the Caribbean, it was encountering abnormally high ocean temperatures made at least 50 to 100 times more likely because of climate change, according to Climate Central’s analysis. (To be clear, this isn’t saying that Ernesto itself was more likely because of climate change—that will require further analysis.) More remarkable still, the group found that Hurricane Beryl, a Category 5 that slammed into Texas in early July, fed on ocean temperatures made 100 to 400 times more likely by climate change. “We also know that storms are moving slower, they are lasting longer, and these things we expect to be influenced by climate as well,” Gilford said.

High ocean temperatures also feed the “rapid intensification” of hurricanes, defined as a jump in sustained wind speeds of at least 35 mph in 24 hours. Hurricane Beryl did that on its way to Texas, shattering records for how quickly it developed into a monster storm. Rapid intensification makes hurricanes extra dangerous because a coastal city might be preparing for a Category 2 to make landfall, only for a Category 5 to suddenly appear. And the problem is only getting worse, as research has found a dramatic increase in the number of rapid intensification events close to shore.

Luckily for Bermuda, Ernesto hasn’t rapidly intensified—though it’s come close this week—but it’s still a very dangerous Category 2. “The shear is potentially a little bit stronger than originally thought,” said Samantha Nebylitsa, who studies hurricanes at the University of Miami, and “dry air just has been really impeding the intensification. It’s just not letting up.” That could well weaken the storm into a Category 1 by the time it hits Bermuda.

The Atlantic is likely to continue providing more fuel as summer winds down. Because the ocean takes longer to heat up than the land, the peak of hurricane season isn’t until September. And the season doesn’t officially close until the end of November. “The best predictions suggest that we are maybe only about 15 or 20 percent the way through of the total activity we expect this year,” Gilford said. “There’s a lot more to come down the pipeline in 2024.”

This story was originally published by Grist and is reproduced here as part of the Climate Desk collaboration.

After unleashing widespread flooding and knocking out electricity for half of Puerto Rico, this season’s third hurricane, Ernesto, has turned north and is approaching Bermuda. In an average Atlantic season, the third hurricane doesn’t spin up until September 7, so Ernesto has arrived way, way early. As of August 9, this summer had already produced a third of the activity in a typical season— with nearly 90 percent of it remaining.

All that makes Ernesto, now a Category 2 hurricane, an ominous sign of what’s still to come in the next few months—and what to expect as the planet rapidly warms. “Being a little more than three weeks ahead of schedule for the third hurricane is pretty impressive,” said Brian McNoldy, a hurricane researcher at the University of Miami.

This spring, scientists predicted that the Atlantic Ocean would play host to an exceptionally active hurricane season, with five major hurricanes and 21 named storms, for one particularly good reason—the ocean is exceptionally warm, and is expected to stay that way. In July, the nursery for Atlantic hurricanes was running 2.8 degrees Fahrenheit higher than the long-term average. “Hurricanes are a lot like engines—they need some sort of fuel,” said Daniel Gilford, who studies hurricanes at Climate Central, a nonprofit research organization. “They need something to be able to accelerate and pick up wind speed, and the thing they use to do that largely is the ocean surface.”

As water evaporates off the ocean, buoyant clouds form, releasing heat and lowering atmospheric pressure. That sucks in air, creating winds and a vortex. Hurricanes also love high humidity because dry air can slow the speed of the updrafts that the storms need to grow big and strong. Hurricanes hate wind shear—winds moving at different speeds and directions at different altitudes. El Niño tends to encourage the proliferation of wind shear over the Atlantic, while La Niña tends to discourage it. Right now the conditions are “neutral,” as El Niño has faded and La Niña has yet to officially form.

So warm ocean temperatures aren’t the only ingredient to make a hurricane, but they’re certainly the fuel. As Ernesto was chugging across the Atlantic between West Africa and the Caribbean, it was encountering abnormally high ocean temperatures made at least 50 to 100 times more likely because of climate change, according to Climate Central’s analysis. (To be clear, this isn’t saying that Ernesto itself was more likely because of climate change—that will require further analysis.) More remarkable still, the group found that Hurricane Beryl, a Category 5 that slammed into Texas in early July, fed on ocean temperatures made 100 to 400 times more likely by climate change. “We also know that storms are moving slower, they are lasting longer, and these things we expect to be influenced by climate as well,” Gilford said.

High ocean temperatures also feed the “rapid intensification” of hurricanes, defined as a jump in sustained wind speeds of at least 35 mph in 24 hours. Hurricane Beryl did that on its way to Texas, shattering records for how quickly it developed into a monster storm. Rapid intensification makes hurricanes extra dangerous because a coastal city might be preparing for a Category 2 to make landfall, only for a Category 5 to suddenly appear. And the problem is only getting worse, as research has found a dramatic increase in the number of rapid intensification events close to shore.

Luckily for Bermuda, Ernesto hasn’t rapidly intensified—though it’s come close this week—but it’s still a very dangerous Category 2. “The shear is potentially a little bit stronger than originally thought,” said Samantha Nebylitsa, who studies hurricanes at the University of Miami, and “dry air just has been really impeding the intensification. It’s just not letting up.” That could well weaken the storm into a Category 1 by the time it hits Bermuda.

The Atlantic is likely to continue providing more fuel as summer winds down. Because the ocean takes longer to heat up than the land, the peak of hurricane season isn’t until September. And the season doesn’t officially close until the end of November. “The best predictions suggest that we are maybe only about 15 or 20 percent the way through of the total activity we expect this year,” Gilford said. “There’s a lot more to come down the pipeline in 2024.”

This story was originally published by Grist and is reproduced here as part of the Climate Desk collaboration.

The city is a growing paradox. Humanity needs its many efficiencies: people living more densely and taking up less land—with easy access to decarbonized public transportation—collaborating and innovating as urbanites have always done. But as the climate warms, city dwellers suffer extreme heat more than their rural counterparts as a result of what’s known as the urban heat-island effect. All that concrete, asphalt, and brick absorbs the sun’s energy, accelerating urban temperatures well above those in the surrounding countryside. 

In the United States, heat already kills more people than any other form of extreme weather, and nowhere is it more dangerous than in cities. So scientists and urban designers are now scrambling to research and deploy countermeasures, especially in the Southwest—not more energy-chugging air conditioning, but more passive, simple cooling techniques. “Cool roofs,” for instance, bounce the sun’s energy back into space using special coatings or reflective shingles. And urban green spaces full of plants cool the surrounding air. 

“In the same way that the urban environment that we have built around us can exacerbate heat, it can also be modified to reduce that heat,” said Edith de Guzman, a researcher at UCLA and director of the Los Angeles Urban Cooling Collaborative. “If we also invested in increasing the reflectivity of existing materials in the built environment, we could reduce the number of ER visits and the number of deaths substantially, in some cases over 50 percent.”

While scientists have long known about the heat-island effect, they’re getting more of the granular data they need to determine what interventions cities should invest in and where. Realizing the many benefits of greening cities with more vegetation at ground level, local governments have already been handing out incentives to plant more trees. But they could be doing much more to encourage the spread of cool roofs, which would make heat waves less dangerous.

New research suggests cities are ignoring the power of cool roofs at their own peril. A study in the journal Geophysical Research Letters earlier this month modeled how much cooler London would have been on the two hottest days in the extra-hot summer of 2018 if the city widely adopted cool roofs compared to other interventions, like green roofs, rooftop solar panels, and groundlevel vegetation. Though simple from an engineering standpoint, cool roofs turned out to be the most effective at bringing down temperatures. 

“We considered it to be practicable everywhere,” said Oscar Brousse, a geographer who specializes in urban climatology at University College London and the study’s lead author. “Because in theory there is no reason—except heritage or protection by UNESCO or something like that—that would prevent you from doing it.”

Cool roofs have the luxury of scale: You can swap out basically any dark, heat-absorbing roof for one made of reflective materials, or simply paint the structure white. (Think about how much hotter you’d get on a 95-degree day wearing a black shirt than a white one.) Even clay roof tiles can be painted with light-colored coatings.

“Each neighborhood has its own unique signature of heat… We need to start from what’s on the ground and build from there.”

Putting them atop single-family homes is a bit trickier, given the proliferation of dark wooden shingles. “This is both about the industry getting locked into a specific type of roofing shingle and municipal building codes not pushing for anything better, despite a growing awareness of the importance of cool roofs,” said Vivek Shandas, who studies the urban heat-island effect at Portland State University but wasn’t involved in the new study. 

With the right policies and incentives, though, cities can encourage the adoption of more reflective shingles. In 2015, Los Angeles became the first major city to require that all new residential construction come with cool roofs by default. While a cool roof can cost the same or slightly more than a traditional one, the Los Angeles Department of Water and Power offers rebates for homeowners to make the switch. But until more municipal codes push the industry to switch to cool roofs, “the wide adoption will remain woefully inadequate for the scale of the challenge we face,” Shandas said.

One tricky thing about the heat-island effect is that no two neighborhoods warm up the same way. Differences in geography, like proximity to lakes that provide cooling and hills that block winds, help determine how hot a given neighborhood already gets and how effective different interventions might be. Wealthier neighborhoods tend to be greener to begin with, whereas lower-income neighborhoods have often been deliberately zoned to host more industrial activities—lots of big buildings and concrete that soak up heat.

“Each neighborhood has its own unique signature of heat,” Shandas said. “We need to start from what’s on the ground and build from there, as opposed to taking, carte blanche, the entire city and throw a bunch of different interventions on it.”

While the new study found that widely deployed cool roofs could reduce temperatures across London by about 2 degrees Fahrenheit on average, in some places it’s by up to 3.6 degrees F. Both ground-level vegetation and rooftop solar panels wouldn’t have that same sort of success: They’d lower temperatures in London by about half a degree F on average. Green roofs would decrease temperatures during the day, but then increase it again at night by releasing accumulated heat, so that, on average, the effects cancel each other out. 

To be clear, this study was just looking at temperatures, not the many other benefits of efforts to cool cities down. A green roof, for instance, serves as a refuge for native plant and animal species. Green spaces on the ground can also prevent flooding if consciously designed to be absorbent. And greenery is just straight-up nice, boosting the mental health of residents. 

While solar panels wouldn’t cool London as much as cool roofs, they could still provide a building with a host of climate-friendly benefits. Electricity from those panels could power ultra-efficient heat pumps, which provide warmth in the winter then reverse in the summer to act like air conditioners. “So even if you don’t decrease the temperature, you would have the means for decreasing it indoors and providing cool shelters,” Brousse said.

Deploying more air conditioners, however, would raise temperatures across London by 0.27 degrees F on average, but up to 1.8 degrees F in the dense city center. That’s because air conditioners cool a space by pumping indoor heat outdoors, essentially recycling heat across a metropolis. 

The research suggests that the more passive cooling techniques that cities deploy, the less reliant they’ll be on air conditioning to provide indoor shelter for the vulnerable. And the better that scientists and urban designers can characterize heat in a given neighborhood, the better they’ll be able to collaborate with that community on solutions. “We should resist the urge to just find one way to do it,” said de Guzman of the Los Angeles Urban Cooling Collaborative. “From a scientific and heat mitigation standpoint, we need to have a combined approach.”

This story was originally published by Grist and is reproduced here as part of the Climate Desk collaboration.

The city is a growing paradox. Humanity needs its many efficiencies: people living more densely and taking up less land—with easy access to decarbonized public transportation—collaborating and innovating as urbanites have always done. But as the climate warms, city dwellers suffer extreme heat more than their rural counterparts as a result of what’s known as the urban heat-island effect. All that concrete, asphalt, and brick absorbs the sun’s energy, accelerating urban temperatures well above those in the surrounding countryside. 

In the United States, heat already kills more people than any other form of extreme weather, and nowhere is it more dangerous than in cities. So scientists and urban designers are now scrambling to research and deploy countermeasures, especially in the Southwest—not more energy-chugging air conditioning, but more passive, simple cooling techniques. “Cool roofs,” for instance, bounce the sun’s energy back into space using special coatings or reflective shingles. And urban green spaces full of plants cool the surrounding air. 

“In the same way that the urban environment that we have built around us can exacerbate heat, it can also be modified to reduce that heat,” said Edith de Guzman, a researcher at UCLA and director of the Los Angeles Urban Cooling Collaborative. “If we also invested in increasing the reflectivity of existing materials in the built environment, we could reduce the number of ER visits and the number of deaths substantially, in some cases over 50 percent.”

While scientists have long known about the heat-island effect, they’re getting more of the granular data they need to determine what interventions cities should invest in and where. Realizing the many benefits of greening cities with more vegetation at ground level, local governments have already been handing out incentives to plant more trees. But they could be doing much more to encourage the spread of cool roofs, which would make heat waves less dangerous.

New research suggests cities are ignoring the power of cool roofs at their own peril. A study in the journal Geophysical Research Letters earlier this month modeled how much cooler London would have been on the two hottest days in the extra-hot summer of 2018 if the city widely adopted cool roofs compared to other interventions, like green roofs, rooftop solar panels, and groundlevel vegetation. Though simple from an engineering standpoint, cool roofs turned out to be the most effective at bringing down temperatures. 

“We considered it to be practicable everywhere,” said Oscar Brousse, a geographer who specializes in urban climatology at University College London and the study’s lead author. “Because in theory there is no reason—except heritage or protection by UNESCO or something like that—that would prevent you from doing it.”

Cool roofs have the luxury of scale: You can swap out basically any dark, heat-absorbing roof for one made of reflective materials, or simply paint the structure white. (Think about how much hotter you’d get on a 95-degree day wearing a black shirt than a white one.) Even clay roof tiles can be painted with light-colored coatings.

“Each neighborhood has its own unique signature of heat… We need to start from what’s on the ground and build from there.”

Putting them atop single-family homes is a bit trickier, given the proliferation of dark wooden shingles. “This is both about the industry getting locked into a specific type of roofing shingle and municipal building codes not pushing for anything better, despite a growing awareness of the importance of cool roofs,” said Vivek Shandas, who studies the urban heat-island effect at Portland State University but wasn’t involved in the new study. 

With the right policies and incentives, though, cities can encourage the adoption of more reflective shingles. In 2015, Los Angeles became the first major city to require that all new residential construction come with cool roofs by default. While a cool roof can cost the same or slightly more than a traditional one, the Los Angeles Department of Water and Power offers rebates for homeowners to make the switch. But until more municipal codes push the industry to switch to cool roofs, “the wide adoption will remain woefully inadequate for the scale of the challenge we face,” Shandas said.

One tricky thing about the heat-island effect is that no two neighborhoods warm up the same way. Differences in geography, like proximity to lakes that provide cooling and hills that block winds, help determine how hot a given neighborhood already gets and how effective different interventions might be. Wealthier neighborhoods tend to be greener to begin with, whereas lower-income neighborhoods have often been deliberately zoned to host more industrial activities—lots of big buildings and concrete that soak up heat.

“Each neighborhood has its own unique signature of heat,” Shandas said. “We need to start from what’s on the ground and build from there, as opposed to taking, carte blanche, the entire city and throw a bunch of different interventions on it.”

While the new study found that widely deployed cool roofs could reduce temperatures across London by about 2 degrees Fahrenheit on average, in some places it’s by up to 3.6 degrees F. Both ground-level vegetation and rooftop solar panels wouldn’t have that same sort of success: They’d lower temperatures in London by about half a degree F on average. Green roofs would decrease temperatures during the day, but then increase it again at night by releasing accumulated heat, so that, on average, the effects cancel each other out. 

To be clear, this study was just looking at temperatures, not the many other benefits of efforts to cool cities down. A green roof, for instance, serves as a refuge for native plant and animal species. Green spaces on the ground can also prevent flooding if consciously designed to be absorbent. And greenery is just straight-up nice, boosting the mental health of residents. 

While solar panels wouldn’t cool London as much as cool roofs, they could still provide a building with a host of climate-friendly benefits. Electricity from those panels could power ultra-efficient heat pumps, which provide warmth in the winter then reverse in the summer to act like air conditioners. “So even if you don’t decrease the temperature, you would have the means for decreasing it indoors and providing cool shelters,” Brousse said.

Deploying more air conditioners, however, would raise temperatures across London by 0.27 degrees F on average, but up to 1.8 degrees F in the dense city center. That’s because air conditioners cool a space by pumping indoor heat outdoors, essentially recycling heat across a metropolis. 

The research suggests that the more passive cooling techniques that cities deploy, the less reliant they’ll be on air conditioning to provide indoor shelter for the vulnerable. And the better that scientists and urban designers can characterize heat in a given neighborhood, the better they’ll be able to collaborate with that community on solutions. “We should resist the urge to just find one way to do it,” said de Guzman of the Los Angeles Urban Cooling Collaborative. “From a scientific and heat mitigation standpoint, we need to have a combined approach.”

This story was originally published by Grist and is reproduced here as part of the Climate Desk collaboration.

One of the iconic sensory experiences of riding a train is actually the sound of ingenuity. As steel railroad tracks heat up, they grow: Eighteen hundred feet of rail expands by more than an inch for every 10 degrees Fahrenheit of temperature increase. So rails used to be laid down in sections — each between 30 and 60 feet long — with small gaps.

“The very specific railway noise that you hear — chuchat … chuchat … chuchat … chuchat … chuchat — is because there is a gap between the rails, and this gap is meant for such expansion,” said Dev Niyogi, who studies urban climate extremes at the University of Texas at Austin. 

Still, in a severe heat wave, the rail can swell until the underlying ties can no longer contain it. Then the rail gets visibly wavy, morphing into what’s known as a sun kink. That’s a serious hazard for trains, which can derail on misaligned tracks. In extreme cases, the track can violently buckle, going from a straight shot to grotesque curves almost instantly. So if it’s excessively hot out, rail services will slow their trains as a precaution, which provides less of the mechanical energy that can lead to buckling. Amtrak, for instance, restricts speeds to 80 miles per hour if the rail temperature hits 140 degrees. That was partly the reason behind Amtrak delays in the Northeast Corridor, which runs between Washington, D.C. and Boston, during a brutal heat wave last month. (Amtrak did not respond to multiple requests to comment for this story.) 

As extreme heat waves get worse, more tracks will turn into sun kinks — disrupting commuter rail service that reduces carbon emissions and slows that warming. In 2019, a study estimated that the U.S. rail network could see additional delay costs totaling between $25 billion and $45 billion by the year 2100, in a scenario that assumed greenhouse gas emissions decline in the next 20 years. 

Compared to a tree falling on top of a track and blocking traffic, or a switch breaking, heat is a much larger, harder problem for rail operators to deal with. “Heat waves tend to be regional, so the impacts can be huge,” said Jacob Helman, one of the author’s of that 2019 study and a senior climate consultant at Resilient Analytics, which provides infrastructure vulnerability assessments. “It can impact the entire Northeast Corridor over the course of five days.”

As climate change drives hotter and longer heat waves, companies are reevaluating their operations and adapting new technologies. Railroads already use remote sensors to determine the temperature of their rails, but are getting still more sophisticated as heat waves intensify. They’re using computer modeling, for example, to figure out how to make tracks more resistant to buckling, among many other steps. “The industry is implementing new ways to use advanced sensors, satellite imaging, and AI to constantly monitor track health and respond to any potential hazards,” said Scott Cummings, assistant vice president of research and innovation at MxV Rail, a subsidiary of the Association of American Railroads. 

In 2019, a study estimated that the U.S. rail network could see additional delay costs totaling between $25 billion and $45 billion by the year 2100, in a scenario that assumed greenhouse gas emissions decline in the next 20 years. 

While those gaps in the rail reduce the problem of buckling, each wheel of a train rolling over each gap results in wear and tear both on the rail and the cars. In response, railroads have for decades been deploying “continuous welded rail,” or CWR — segments of track stretching a quarter mile or more. CWR is held firmly in place by concrete ties (the strips under the rails that used to be made of wood), themselves held in place with ballast stones poured in between them. “It’s all just so much more rigid,” said Daniel Pyke, a rail expert at Sensonic in the United Kingdom, which makes train safety tech. “You’ve got so much more mass there to keep everything in place.” 

Railroads even adapt tracks to a specific climate: By installing continuous welded rail on a day with the right conditions, crews prepare it for the local high and low temperatures. “Tracks are laid and secured at the ‘neutral temperature,’ which is the average temperature of the rails,” said Farshid Vahedifard, a professor of civil and environmental engineering at Tufts University who studies the impact of climate change on infrastructure. “This helps ensure that the rail remains stable throughout temperature fluctuations.” As regional temperatures rise, railroads might opt to lay down track on hotter days, thus preparing the rail for increasingly extreme heat. (Though when the rails get cold in winter, they contract, which can cause cracking.)

Another intervention is painting the rails white, which reflects a good amount of the sun’s energy off the steel. “It sounds crazy,” Pyke said, “but it works.” It’s labor-intensive — you have to keep reapplying because of the wear-and-tear on the paint and the fact that it dirties over time — but track-mounted machines can do the work quickly. 

A new technology known as distributed acoustic sensing uses fiber optic cables running along railways to “listen” for defects. Disturbances on the track jostle the optics, changing how light travels through them. That’s analyzed by a special device to determine whether a rockfall has crashed into the tracks, or if a crack has formed in the rails, as each kind of disturbance has its own unique signal. 

As the track heats up and expands, the fiber optics already hear “thermal pops.” Theoretically, Pyke said, Sensonic’s technology could detect the unique ground vibrations associated with buckling. They’d just need data — perhaps they can manually heat up a test track to induce a sun kink — to train the algorithm on what to listen for. “We already produced some rock fall, landslide sensors, and they’re looking for ground vibration,” Pyke said. “So I would imagine — I can’t promise — but I would imagine we would tweak those to be able to detect it.”

If railroads can get better data on their vulnerability to buckling — like specific track temperatures over wide areas, instead of relying on inferences from local air temperatures — they could more accurately determine how much to slow trains as a precaution. That would avoid delays, keep commuters  from returning to their cars, save railroads money, and generally make trains safer. “You can make more informed decisions about speed orders,” said Helman from Resilient Analytics. “Maybe it doesn’t need to be 40 miles per hour. Maybe it only needs to be 10. Maybe you don’t need it at all.”