Climate change

Over the past century, the Earth’s average temperature has swiftly increased by about 1 degree Celsius (1.8 degrees Fahrenheit). The evidence is hard to dispute. It comes from thermometers and other sensors around the world. But what about the thousands of years before the Industrial Revolution, before thermometers, and before humans warmed the climate by releasing heat-trapping carbon dioxide from fossil fuels? Back then, was Earth’s temperature warming or cooling? Even though scientists know more about the most recent 6,000 years than any other multimillennial interval, studies on this long-term global temperature trend have come to contrasting conclusions. To try to resolve the difference, we conducted a comprehensive, global-scale assessment of the existing evidence, including both natural archives, like tree rings and seafloor sediments, and climate models. Our results, published Feb. 15, 2023, suggest ways to improve climate forecasting to avoid missing some...

New Zealand, where agriculture is one of the largest contributors to climate change, is proposing a tax on cow burps. The reason seems simple enough: Cows release methane, a potent greenhouse gas, and New Zealand has a goal of reaching net-zero emissions by midcentury. Right now, the country’s effects on climate change come roughly equally from carbon dioxide and methane. Worldwide, 150 governments have committed to cut methane emissions, both from agriculture and by cracking down on the largest source – fugitive leaks from natural gas pipelines and other fossil fuel infrastructure. But is methane from cows really as bad for the climate as methane from fossil fuels? And given its shorter lifetime in the atmosphere, is methane as bad as carbon dioxide? The answers involve renewable resources and the so-called circular economy. Understanding the effectiveness of different strategies is important as countries plan their routes to net-zero emissions, which is necessary...

The Research Brief is a short take about interesting academic work. The big idea Psychological trauma from extreme weather and climate events, such as wildfires, can have long-term impacts on survivors’ brains and cognitive functioning, especially how they process distractions, my team’s new research shows. Climate change is increasingly affecting people around the world, including through extreme heat, storm damage and life-threatening events like wildfires. In previous research, colleagues and I showed that in the aftermath of the 2018 fire that destroyed the town of Paradise, California, chronic symptoms of post-traumatic stress disorder (PTSD), anxiety and depression were highly prevalent in the affected communities more than six months after the disaster. We also found a graded effect: People whose homes or families were directly affected by fire showed greater mental health harm than those where who were indirectly effected, meaning people who witnessed the e...

Food loss and waste are major problems around the world. When food is tossed aside or allowed to spoil, it makes economies less productive and leaves people hungry. It also harms Earth’s climate by generating methane, a potent greenhouse gas. Food loss and waste accounts for 4% of global greenhouse gas emissions. If food waste were a country, it would be the third-largest emitter in the world, ahead of India and behind only China and the U.S. Worldwide, 1.3 billion tons of food are lost or wasted every year. Earth’s population is projected to increase from 8 billion today to roughly 10 billion by 2050. Feeding that many people will require nations to increase agricultural production by more than 70% and reduce food loss and waste. Expanding food cold chains to the world’s least-developed countries can have enormous impacts. But it also raises concerns if it’s not done in a way that avoids contributing to climate change. Inves...

Several major airlines have pledged to reach net-zero carbon emissions by midcentury to fight climate change. It’s an ambitious goal that will require an enormous ramp-up in sustainable aviation fuels, but that alone won’t be enough, our latest research shows. The idea of jetliners running solely on fuel made from used cooking oil from restaurants or corn stalks might seem futuristic, but it’s not that far away. Airlines are already experimenting with sustainable aviation fuels, including biofuels made from agriculture residues, trees, corn and used cooking oil, and synthetic fuels made with captured carbon and green hydrogen. United Airlines, which has been using a blend of used oil or waste fat and fossil fuels on some flights from Los Angeles and Amsterdam, recently announced plans to power 50,000 flights a year between its Chicago and Denver hubs using ethanol-based sustainable aviation fuels by 2028. The airline also launched a US$100 million fund on Feb...