Why are climate change impacts so much worse than expected so much sooner than expected? A review of how global warming is changing extreme weather
Climate change now regularly causes catastrophic extreme weather: heat waves, droughts, wildfires, and floods. Yet conventional wisdom in the late 20th century was that significant damage from global warming would emerge only late in the 21st. While early projections of the rise in global mean temperature have proved largely accurate, the harmful impacts of climate change have arrived much sooner than projected. How has a well-projected warming of just over 1°C, a value an order of magnitude smaller than the temperature swing on a single sunny day, caused such severe impacts?
In this talk I argue, using published and new examples from observations and models, that the marked increase in extreme weather with warming arises from the simple statistics of extreme events combined with the quasi-exponential dependence of the saturation vapor pressure of water on temperature, physics (the Clausius-Clapeyron relation) that is pervasive in its influence on weather phenomena. Extremes may come about from an overlay of phenomena on different scales in space and time, and their most severe impacts often occur where changing weather extremes intersect with other anthropogenic influences on the environment. Finally, human and ecological systems were well adapted to a past, largely-stable climate, rendering them all the more vulnerable to events - temperatures, rates of rainfall, etc. - that exceed the thresholds of past experience.
This under-projection, for the most part, by climate science of emerging severe impacts of climate change points to limitations in how our science is done and suggestions for how we might do better in the future.
