Daniel SwainJan 11, 2025
Our paper on "Hydroclimate volatility on a Warming Earth" is out in Nature Reviews Earth & Environment. We assess existing scientific literature & conduct new analysis--concluding that "#HydroclimateWhiplash" is increasing due to #ClimateChange. [Thread] https://www.nature.com/articles/s43017-024-00624-z
Hydroclimate volatility on a warming Earth - Nature Reviews Earth & Environment

Rapid transitions between extreme wet and extreme dry conditions — ‘hydroclimate whiplash’ — have marked environmental and societal impacts. This Review outlines observed and projected changes in hydroclimate whiplash, suggesting that subseasonal and interannual volatility will increase markedly with ongoing warming.

Nature
Show threadDaniel SwainJan 11, 2025
"Hydroclimate volatility" refers to rapid transitions between unusually wet & dry conditions relative to local baseline. For quantitative analysis, we define a new "hydroclimate whiplash" metric using Standardized Precipitation & Evaporation Index (SPEI). https://www.nature.com/articles/s43017-024-00624-z
Hydroclimate volatility on a warming Earth - Nature Reviews Earth & Environment

Rapid transitions between extreme wet and extreme dry conditions — ‘hydroclimate whiplash’ — have marked environmental and societal impacts. This Review outlines observed and projected changes in hydroclimate whiplash, suggesting that subseasonal and interannual volatility will increase markedly with ongoing warming.

Nature
Show threadDaniel SwainJan 11, 2025
One key aspect of the framework for understanding such volatility is that it encompasses both "supply" & "demand" side of water balance--that is, not only precipitation (or lack thereof), but also evaporation (or evaporative demand). Precipitation doesn't tell the whole story!
Show threadDaniel SwainJan 11, 2025
On the "wet" side, it's essentially a story of heavy precipitation events. But on the "dry" side, it's a combination of usually low precipitation AND excess evaporation (or, more precisely, evaporative demand--i.e., "potential evaporation"). https://www.nature.com/articles/s43017-024-00624-z
Hydroclimate volatility on a warming Earth - Nature Reviews Earth & Environment

Rapid transitions between extreme wet and extreme dry conditions — ‘hydroclimate whiplash’ — have marked environmental and societal impacts. This Review outlines observed and projected changes in hydroclimate whiplash, suggesting that subseasonal and interannual volatility will increase markedly with ongoing warming.

Nature
Show threadDaniel SwainJan 11, 2025
We introduce analogy of the "Expanding Atmospheric Sponge" to illustrate the practical consequences of warming atmosphere's increased ability to"hold" water vapor--which raises ceiling not only on intensity of precipitation, but also evaporative demand. https://www.nature.com/articles/s43017-024-00624-z
Hydroclimate volatility on a warming Earth - Nature Reviews Earth & Environment

Rapid transitions between extreme wet and extreme dry conditions — ‘hydroclimate whiplash’ — have marked environmental and societal impacts. This Review outlines observed and projected changes in hydroclimate whiplash, suggesting that subseasonal and interannual volatility will increase markedly with ongoing warming.

Nature
Show threadDaniel SwainJan 11, 2025
Using our new "hydroclimate whiplash" metric, which accounts for both precipitation & evaporative demand, we found that such whiplash has *already* (as of 2023) increased by 31–66% globally (depending on dataset)--& could more than double w/3°C of warming. https://www.nature.com/articles/s43017-024-00624-z
Hydroclimate volatility on a warming Earth - Nature Reviews Earth & Environment

Rapid transitions between extreme wet and extreme dry conditions — ‘hydroclimate whiplash’ — have marked environmental and societal impacts. This Review outlines observed and projected changes in hydroclimate whiplash, suggesting that subseasonal and interannual volatility will increase markedly with ongoing warming.

Nature
Show threadDaniel SwainJan 11, 2025
We also find that the observed historical increase in global hydroclimate whiplash is greater than predicted by a leading climate model large ensemble (CESM2-LE) for our present level of warming, though there is considerable uncertainty at regional scales. https://www.nature.com/articles/s43017-024-00624-z
Hydroclimate volatility on a warming Earth - Nature Reviews Earth & Environment

Rapid transitions between extreme wet and extreme dry conditions — ‘hydroclimate whiplash’ — have marked environmental and societal impacts. This Review outlines observed and projected changes in hydroclimate whiplash, suggesting that subseasonal and interannual volatility will increase markedly with ongoing warming.

Nature
Show threadDaniel SwainJan 11, 2025
At global scales, the primary cause for observed (and projected further) increase in volatility is the "Expanding Atmospheric Sponge"--which drives both more intense downpours & evaporative demand & thus contributes to increasing swings between wet & dry. https://www.nature.com/articles/s43017-024-00624-z
Hydroclimate volatility on a warming Earth - Nature Reviews Earth & Environment

Rapid transitions between extreme wet and extreme dry conditions — ‘hydroclimate whiplash’ — have marked environmental and societal impacts. This Review outlines observed and projected changes in hydroclimate whiplash, suggesting that subseasonal and interannual volatility will increase markedly with ongoing warming.

Nature
Show threadDaniel SwainJan 11, 2025
This effect, however, is modulated at regional scales by (dynamical) changes in atmospheric circulation--essentially, shifts in horizontal or vertical wind patterns & subsequent moisture transport--that can amplify or offset thermodynamic contributions. https://www.nature.com/articles/s43017-024-00624-z
Hydroclimate volatility on a warming Earth - Nature Reviews Earth & Environment

Rapid transitions between extreme wet and extreme dry conditions — ‘hydroclimate whiplash’ — have marked environmental and societal impacts. This Review outlines observed and projected changes in hydroclimate whiplash, suggesting that subseasonal and interannual volatility will increase markedly with ongoing warming.

Nature
Show threadDaniel SwainJan 11, 2025
Projected, and even observed, changes in atmospheric circulation at regional scales remain (relatively) poorly understood. But predominant importance of the the "Expanding Atmospheric Sponge" globally lends confidence to our primary conclusions. https://www.nature.com/articles/s43017-024-00624-z
Hydroclimate volatility on a warming Earth - Nature Reviews Earth & Environment

Rapid transitions between extreme wet and extreme dry conditions — ‘hydroclimate whiplash’ — have marked environmental and societal impacts. This Review outlines observed and projected changes in hydroclimate whiplash, suggesting that subseasonal and interannual volatility will increase markedly with ongoing warming.

Nature
Show threadDaniel Swain
How are consequences of hydroclimate volatility different from wet and dry extremes (e.g., floods & droughts) in isolation? Well, sometimes the temporal sequencing matters a great deal for widely ranging reasons, from public health to geohazards. https://www.nature.com/articles/s43017-024-00624-z
Hydroclimate volatility on a warming Earth - Nature Reviews Earth & Environment

Rapid transitions between extreme wet and extreme dry conditions — ‘hydroclimate whiplash’ — have marked environmental and societal impacts. This Review outlines observed and projected changes in hydroclimate whiplash, suggesting that subseasonal and interannual volatility will increase markedly with ongoing warming.

Nature
Jan 11, 2025 at 12:16amFedica
Show threadDaniel SwainJan 11, 2025
A particularly stark & timely example of consequences of a "wet-to-dry" whiplash episode is unfolding this week in Southern California, where devastating wildfires followed two wet winters (w/abundant vegetation growth) & a record dry period subsequently. https://x.com/Weather_West/status/1877476551761031466
Dr. Daniel Swain (@Weather_West) on X

In 2024, Southern California experienced an exceptional episode of wet-to-dry hydroclimate whiplash. Very wet conditions in winters of 2023 and 2024 gave way to a record-dry start to 2025 wet season (with periods of record warmth and evaporative demand in between). #CAwx #CAfire

X (formerly Twitter)
Show threadDaniel SwainJan 11, 2025
Ultimately, we find that there is abundant evidence from the (over 200) papers we reviewed, and from our own summary analysis, that increasing #HydroclimateVolatility will likely be a near-universal signature of #ClimateChange over global land areas. https://www.nature.com/articles/s43017-024-00624-z
Hydroclimate volatility on a warming Earth - Nature Reviews Earth & Environment

Rapid transitions between extreme wet and extreme dry conditions — ‘hydroclimate whiplash’ — have marked environmental and societal impacts. This Review outlines observed and projected changes in hydroclimate whiplash, suggesting that subseasonal and interannual volatility will increase markedly with ongoing warming.

Nature
Show threadDaniel SwainJan 11, 2025
Finally, I wanted to thank my co-authors: Andy Prein, John Abatzoglou, Christine Albano, Manuela Brunner, Noah Diffenbaugh, Deepti Singh, Christopher Skinner, & Danielle Touma. This was truly a collaborative & multi-year effort; without them, it would not have come to fruition.