The United States experienced the coldest October in a decade, and last year was one of the wettest on record. While California is experiencing another year of deadly wildfires, the Midwest and other areas faced severe springtime flooding. The changing climate is increasingly evident in such record-setting and extreme weather events, which are expected to occur more frequently and intensely in coming years. Yet, research published in Nature Communications in October suggests that current climate change predictions may still be too optimistic: based on new calculations, sea levels are predicted to rise three times more than previously anticipated. More than 150 million people currently live on land that will be below the high tide line by 2050.

Figure. An offshore oil rig is docked for repairs in Sabine Pass, Texas. Obama-era federal clean-water protections had placed limits on the use of polluting chemicals near streams and wetlands; however, these were repealed on September 12 by the Trump administration. Photo by Brandon Thibodeaux / The New York Times/Redux.

The significant and long-lasting health consequences of climate change are detailed in the Lancet Countdown's annual report, published in the November 16 Lancet. It notes that although the Earth has warmed 1[degrees]C compared with the preindustrial temperature average, it's expected to be more than 4[degrees] warmer during the lifetimes of today's children. The health consequences will be far-reaching: increasing food insecurity, as crop yields decline further; greater susceptibility to diseases, like dengue fever and Vibrio cholerae, which are being transmitted more easily, for longer periods of time, and in more geographically diverse regions; organ damage, especially to the lungs and heart, due to worsening air pollution; and an increasing number of heat wave exposures, which also threaten public safety, as documented in decades of research linking heat to spikes in rates of violence and crime. Despite this outlook, the Trump administration continues to prioritize rolling back or weakening environmental protections. In an analysis published on September 12, the New York Times reported the administration had targeted 85 air, land, and water rules: 53 had already been eliminated and 32 were in the process of being rolled back by the end of 2019. These protections address issues such as water pollution, toxic substances and safety, air pollution and emissions, drilling and extraction, and infrastructure and planning. The administration has also sought to stop state environmental efforts. In September, it also revoked a waiver allowing California to set stricter car emission standards. A subsequent report from Carnegie Mellon University researchers highlighted the importance of air pollution policies: annual average fine particulate matter in the United States rose by 5.5% from 2016 to 2018 after decreasing by 24.2% during the previous seven years. The researchers conclude that 9,700 additional premature deaths in 2018 were associated with this increase in air pollution.

As the Trump administration announced in November that it would begin withdrawing from the Paris climate agreement to reduce greenhouse gas emissions, more than 11,000 scientists worldwide issued a stark environmental warning in a report published online on November 5 in BioScience. Using blunt language and simple graphics to illustrate the impact of human activities on greenhouse gas emissions, the scientists cited their "moral obligation" to declare "clearly and unequivocally that planet Earth is facing a climate emergency."-Corinne McSpedon