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Superstorms, abrupt climate shifts and New York City frozen in ice. That’s how the blockbuster Hollywood movie “The Day After Tomorrow” depicted an abrupt shutdown of the Atlantic Ocean’s circulation and the catastrophic consequences. While Hollywood’s vision was over the top, the 2004 movie raised a serious question: If global warming shuts down the Atlantic Meridional Overturning Circulation, which is crucial for carrying heat from the tropics to the northern latitudes, how abrupt and severe would the climate changes be? Twenty years after the movie’s release, we know a lot more about the Atlantic Ocean’s circulation. Instruments deployed in the ocean starting in 2004 show that the Atlantic Ocean circulation has observably slowed over the past two decades, possibly to its weakest state in almost a millennium. Studies also suggest that the circulation has reached a dangerous tipping point in the past that sent it into a precipitous, uns...

E-bikes have captured widespread attention across the U.S., and for good reason. They are the most energy-efficient way to move from place to place, providing exercise in the process, and offer enough assistance while pedaling uphill or into headwinds to make them usable for many types of riders. Greenhouse gas emissions from e-bikes are much lower than those from either gasoline-powered or electric cars. Some cities and states are encouraging the use of e-bikes by providing purchase incentives, often drawing on public funds dedicated to curbing climate change. Currently, over 100 cities and states have or plan to launch e-bike incentive programs, most funded by energy or environment initiatives. However, there has been little research on the effectiveness of these types of programs, how to design them or how to define goals. We study transportation from many angles, including innovation, sustainability and economics. Our new study, published in the journal Transportation Res...

Strong winds spread the largest wildfire in Texas history across more than 1 million acres of rangeland in the Panhandle, the heart of the state’s cattle-producing region, and into Oklahoma in late February 2024. Light precipitation on Feb. 29 helped firefighters as they tried to contain the Smokehouse Creek Fire and other blazes threatening homes and livestock, but the heat and winds picked up again on March 2. At least two people died and scores of structures, including homes, burned. Karen Hickman, a grassland ecologist at Oklahoma State University and president of the Society for Range Management, explained why the fires spread so fast, the risks to livestock and how quickly these ecosystems can recover. How did the fires spread so far so quickly? This region of Texas and Oklahoma is mostly rangeland where cattle graze. A combination of higher-than-average temperatures and low humidity had dried out the dormant plants. When the winds picked up following a couple of ho...

The U.S. Environmental Protection Agency has announced a new standard for protecting the public from fine particulate air pollution, known as PM2.5 because the particles are smaller than 2.5 millionths of a meter. These minute particles can penetrate deeply into the body and have been linked to many serious illnesses. The new rule sets an annual limit of 9 micrograms per cubic meter of air, down from the previous level of 12 micrograms. States will be required to meet this standard and to take it into consideration when they evaluate applications for permits for new stationary air pollution sources, such as electric power plants, factories and oil refineries. Under the Clean Air Act, the EPA is required to set air pollution standards at levels that protect public health. In the four articles that follow, scholars wrote about the many ways in which exposure to PM2.5 contributes to cardiovascular disease, lung cancer, other illnesses such as dementia, and premature deaths. 1. An...

Rechargeable batteries are great for storing energy and powering electronics from smartphones to electric vehicles. In cold environments, however, they can be more difficult to charge and may even catch on fire. I’m a mechanical engineering professor who’s been interested in batteries since college. I now lead a battery research group at Drexel University. In just this past decade, I have watched the price of lithium-ion batteries drop as the production market has grown much larger. Future projections predict the market could reach thousands of GWh per year by 2030, a significant increase. But, lithium-ion batteries aren’t perfect – this rise comes with risks, such as their tendency to slow down during cold weather and even catch on fire. Behind the Li-ion battery The electrochemical energy storage within batteries works by storing electricity in the form of ions. Ions are atoms that have a nonzero charge because they have either too many or not eno...