As the climate becomes warmer on average, it makes intuitive sense that we will see more hot days and we've had predictions of this for some time. However, the duration of heatwaves — how many days in a row exceed a temperature that is unusually hot for a given region — can be very important for impacts on humans, livestock and ecosystems. Predicting how these durations will change under a long-term warming trend is more challenging because day-to-day temperatures are correlated — tomorrow's temperatures have a dependence on today's temperature. This study takes this effect into account, along with the warming seen in current and historical observations and projected for the future by climate models for a wide range of land regions. Not only do the heatwave durations increase, but each additional increment of warming causes a larger increase in the typical length of long heat waves. In other words, if the next decade brings as much large-scale warming as a previous decade, the additional increase in heatwave durations would be even larger than we've experienced so far.

Low carbon fuel policies are intended to reduce greenhouse gas (GHG) emissions from transportation. However, rigid carbon intensity (CI) accounting procedures in current policies may limit CI responsiveness across candidate sites and facilities. This study examines how low carbon fuel programs capture or overlook spatial variability and net electricity production in biofuel carbon intensity, influencing crediting outcomes and fuel selling prices.

The United States was the world’s largest source of carbon emissions for more than a century. In a new analysis, researchers document the changing trends in U.S. carbon emissions from the late 19th century to the early 21st century, focusing on emissions from fossil fuels and industry. They discuss the main factors that contributed to the rollercoaster of changes in historical carbon emissions. The authors close by offering lessons from the U.S. experience for developing countries.