The weather on planet Earth is a vital and sometimes fatal force in human affairs. Efforts to control or reduce the harmful impacts of weather go back far in time. In this, the latest National Academies' assessment of weather modification, the committee was asked to assess the ability of current and proposed weather modification capabilities to provide beneficial impacts on water resource management and weather hazard mitigation. It examines new technologies, reviews advances in numerical modeling on the cloud and mesoscale, and considers how improvements in computer capabilities might be applied to weather modification. Critical Issues in Weather Modification Research examines the status of the science underlying weather modification in the United States. It calls for a coordinated national research program to answer fundamental questions about basic atmospheric processes and to address other issues that are impeding progress in weather modification.

As climate has warmed over recent years, a new pattern of more frequent and more intense weather events has unfolded across the globe. Climate models simulate such changes in extreme events, and some of the reasons for the changes are well understood. Warming increases the likelihood of extremely hot days and nights, favors increased atmospheric moisture that may result in more frequent heavy rainfall and snowfall, and leads to evaporation that can exacerbate droughts. Even with evidence of these broad trends, scientists cautioned in the past that individual weather events couldn't be attributed to climate change. Now, with advances in understanding the climate science behind extreme events and the science of extreme event attribution, such blanket statements may not be accurate. The relatively young science of extreme event attribution seeks to tease out the influence of human-cause climate change from other factors, such as natural sources of variability like El Niño, as contributors to individual extreme events. Event attribution can answer questions about how much climate change influenced the probability or intensity of a specific type of weather event. As event attribution capabilities improve, they could help inform choices about assessing and managing risk, and in guiding climate adaptation strategies. This report examines the current state of science of extreme weather attribution, and identifies ways to move the science forward to improve attribution capabilities.

New York, Wiley [1974].