written 4 September 2022
published 11 September 2022
One of the consequences of the disrupted climate is wild swings in the weather. For example, this summer, Dallas, Texas has been suffering from heat and drought conditions that have threatened the integrity of their electric grid. Wildfires burned through a Dallas suburb a month ago, destroying 15 homes. Two weeks later, that same area was flooded when a record breaking 15" of rain fell in 24 hours. Such massive rainfall is considered a 1,000 year event, but was intensely localized, with only 2" falling just 25 miles away. Roads turned into rivers, a State of Emergency was declared, hundreds of flights were cancelled, and one person died.
A similar 1,000 year flood hit Jackson, the capitol of Mississippi, population 153,000. In August, almost 13" fell in four days, about three time their normal monthly rainfall. Decades of structural racism had underfunded the city, causing decaying infrastructure, with 40 percent of treated water lost due to broken pipes and inefficient equipment. Consequently, the sudden influx of rainwater adversely impacted the city's water treatment plant, slowing down water production at the plant to the point of collapse. Throughout the entire city, there is now insufficient water volume, or quality, to fight fires, flush toilets, drink, cook or bathe. What city water is available must be boiled before use.
But flooding this August was not limited to the United States, and the worst has been in Pakistan, population 230 million. Since June, it has been raining for over 3 months, and monsoon storms have occurred twice as often as usual, delivering 5 times as much rain. This was on top of a record breaking heat wave from March to June, hitting 124°F at times, which caused massive glacier melt in the northern part of the country. The monsoon inundation caused many of the glacial melt lakes to burst their bounds, adding to the downstream disaster.
All of Pakistan is affected, but the south and northwest were hit the hardest. One third of the country is now flooded, displacing 33 million people, leaving 20 million homeless, with 1,200 dead so far. In the northwestern mountainous region, roads, bridges, and building have been destroyed, as raging rivers flowed through normal city streets. The southern portion is now a flooded lake, destroying the agricultural output of the country, which used to export rice, wheat, and sugar.
This flooding, the largest in living memory, is expected to cost more than $10B. Already a poor country, Pakistan is now dealing with not only the massive infrastructure destruction but a huge population that has lost everything, with no food, shelter, or potable water. The flood waters are contaminated with raw sewage and chemicals, insect populations have exploded, and water borne diseases are spreading rapidly.
This kind of inundation is referred to as an "atmospheric river". The warming atmosphere and oceans increase the volume of water carried in these systems. A recent study from the Scripps Institution of Oceanography indicates that flooding damages from these events now cost more than $1B per year in the 11 western American states. Lead author Tom Corringham said, “The threat of a megaflood in the western United States is very real. As atmospheric rivers become more intense, flood damages are on track to triple by the end of the century, but the impacts will be felt sooner."
The California counties identified most at risk of increased flood damages are Sonoma, Yuba, Sacramento, and Los Angeles. Reductions in greenhouse gas emissions could reduce damages, as would investment in floodplain restoration and flood-managed aquifer recharge. The researchers project that, if no action is taken, expected atmospheric river related flood damages will increase by 10 percent each decade until the 2050s, rising more steeply as the century progresses.
But the damage could be much larger. In 1861, it rained in California for 43 days, flooding more than 3/4 of the California Central Valley, taking 6 months to drain away. This was the first such event since the Europeans had arrived, but subsequent research has shown they happen every 150-200 years. Climate change will make things worse.
It's hard for humans to consider low probability, high risk future events such as the adverse impacts of climate change, and our economy is oriented toward short term benefits. Although we can now see the problem, are we wise enough to make the effort?
