2022’s U.S. Climate Disasters: A Tale of Too Much Rain – and Too Little
This isn’t just a freak year: Such extreme events are occurring with increasing frequency and intensity.
Climate Change Is Intensifying These Disasters
The most recent global climate assessment from the United Nations Intergovernmental Panel on Climate Change found significant increases in both the frequency and intensity of extreme temperature and precipitation events, leading to more droughts and floods.
Extreme flooding and droughts are also getting deadlier and more expensive, despite an improving capacity to manage climate risks, a study published in 2022 found. Part of the reason is that today’s extreme events, enhanced by climate change, often exceed communities’ management capabilities.
Extreme events, by definition, occur rarely. A 100-year flood has a 1% chance of happening in any given year. So when such events occur with increasing frequency and intensity, they are a clear indication of a changing climate state.
Climate Models Showed These Risks Were Coming
Much of this is well understood and consistently reproduced by climate models.
As the climate warms, a shift in temperature distribution leads to more extremes. For example, globally, a 1 degree Celsius increase in annual average temperature is associated with a 1.2 C to 1.9 C (2.1 Fahrenheit to 3.4 F) increase in the annual maximum temperature.
In addition, global warming leads to changes in how the atmosphere and ocean move. The temperature difference between the equator and the poles is the driving force for global wind. As the polar regions warm at much higher rates than the equator, the reduced temperature difference causes a weakening of global winds and leads to a more meandering jet stream.
Some of these changes can create conditions such as persistent high-pressure systems and atmospheric blocking that bring more intense heat waves. The heat domes over the Southern Plains and South in June and in the West in September were both examples.
Warming can be further amplified by positive feedbacks.
For example, higher temperatures tend to dry out the soil, and less soil moisture reduces the land’s heat capacity, making it easier to heat up. More frequent and persistent heat waves lead to excessive evaporation, combined with decreased precipitation in some regions, causing more severe droughts and more frequent wildfires.
Higher temperatures increase the atmosphere’s capacity to hold moisture at a rate of about 7% per degree Celsius. This increased humidity leads to heavier rainfall events.
In addition, storm systems are fueled by latent heat – the large amount of energy released when water vapor condenses to liquid water. Increased moisture content in the atmosphere also enhances latent heat in storm systems, increasing their intensity. Extreme heavy or persistent rainfall leads to increased flooding and landslides, with devastating social and economic consequences.
Even though it’s difficult to link specific extreme events directly to climate change, when these supposedly rare events occur with greater frequency in a warming world, it is hard to ignore the changing state of our climate.
The New Abnormal
This year might provide a glimpse of our near future, as these extreme climate events become more frequent.
To say this is the “new normal,” though, is misleading. It suggests that we have reached a new stable state, and that is far from the truth. Without serious effort to curb greenhouse gas emissions, this trend toward more extreme events will continue.
Shuang-Ye Wu is Professor of Geology and Environmental Geosciences, University of Dayton. This article, which updates an article originally published on 21 September 2022, is published courtesy of The Conversation.
