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.
7. National Survey of US Public Transit Agency Experience with and Response to Extreme Weather Events
Extreme weather events pose serious challenges public transit systems. They disrupt transit operations, impair service quality, increase threats to public safety, and damage infrastructure. This report presents findings from a June 2016 national survey of public transit agencies in the United States to understand what types of extreme weather transit agencies are experiencing, what risks are associated with extreme events and how they are responding or preparing for them.
The survey collected data from approximately 900 transit professionals who work in planning, operation, maintenance, and engineering in 273 transit agencies in the U.S. Survey items captured data on recent experiences with extreme weather events, perception of weather risks to the local transit system, assessment of the agency’s capacity and challenges in dealing with weather risks, and organizational responses and adaption to extreme weather events and potential climate risks. A total of 352 individuals representing 197 transit agencies responded to the survey (41% response rate) resulting in a rich and unique dataset on extreme weather and transit.
This report provides a descriptive summary and assessment of aggregate survey responses. Findings are presented in four parts: recent experience with extreme weather; perception of weather and climatic risks; assessment of organizational priority, capacity and challenge of managing extreme weather; organizational responses and adaptation to extreme weather events.