The year 2022 will be remembered in the United States for its devastating floods and storms, as well as its extreme heat waves and droughts.
By October, the United States had already experienced 15 disasters each causing more than $1 billion in damage, well above the average. The year began and ended with severe, widespread winter storms from Texas to Maine, affecting tens of millions of people and causing significant damage. Then, March set the record for the most reported tornadoes in the month – 233.
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Over a five-week period during the summer, five 1,000-year rainfall events occurred in St. Louis, eastern Kentucky, southern Illinois, Valley of death in California and Dallas, causing devastating and sometimes deadly flash floods. Severe flooding in Mississippi cut off Jackson’s troubled water supply for weeks. A historic flood in Montana, brought on by heavy rains and melting snow, has forced the evacuation of large areas of Yellowstone National Park.
“ While it is difficult to directly link specific extreme events to climate change, when these supposedly rare events occur with greater frequency in a warming world, it is difficult to ignore the changing state of our climate. ”
In the fall, Hurricanes Ian and Fiona inundated Florida and Puerto Rico with extreme rainfall and deadly and destructive storm surges. Ian became one of the costliest hurricanes in US history. And a typhoon pounded 1,000 miles (1,600 km) from the Alaskan coast.
While too much precipitation threatened some areas, extreme heat and too little precipitation heightened the risks elsewhere.
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Persistent heat waves persisted in many parts of the country, setting temperature records. Wildfires raged in Arizona and New Mexico amid a mega-drought in the southwestern United States, worse than anything the region has seen in at least 1,200 years.
The drought also left the Mississippi River so low near Memphis in the fall that barges could not pass without additional dredging and water discharges upstream. This hampered grain transportation during the critical harvest period. Along the Colorado River, officials discussed even tighter water use restrictions as water levels approached dangerously low levels in major reservoirs.
The United States was not alone in its climate disasters.
In Pakistan, record monsoon rains flooded more than a third of the country, killing more than 1,500 people. In India and China, heat waves and prolonged droughts have dried up rivers, disrupted power grids and threatened the food security of billions of people. Widespread flooding and landslides triggered by torrential rains have also killed hundreds in South Africa, Brazil and Nigeria.
In Europe, heatwaves have set record temperatures in Britain and other parts of the continent, leading to severe droughts, low river flows that have slowed shipping and wildfires in many parts of the continent. . Much of East Africa is still grappling with a multi-year drought – the worst in more than 40 years, according to the United Nations – leaving millions vulnerable to food shortages and starvation.
This is not just an abnormal 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 a significant increase in the frequency and intensity of extreme temperatures and rainfall, leading to more droughts and floods .
Floods and extreme droughts are also becoming deadlier and more costly, despite improved ability to manage climate risks, according to a study published in 2022. This is partly because today’s extreme events today, reinforced by climate change, often exceed the management capacities of communities.
Extreme events, by definition, rarely occur. A 100-year flood has a 1% chance of occurring in a given year. Thus, when such events occur with increasing frequency and intensity, they are a clear indication of a changing climatic state.
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Climate models have shown that these risks occur
Much of this is well understood and consistently reproduced by climate models.
As the climate warms, a change in temperature distribution leads to more extremes. For example, globally, a 1 degree Celsius increase in mean annual temperature is associated with a 1.2 C to 1.9 C (2.1 Fahrenheit to 3.4 F) increase in maximum temperature annual.
Additionally, global warming is causing changes in the way the atmosphere and ocean move. The temperature difference between the equator and the poles is the driving force of the global wind. As the polar regions warm at much higher rates than the equator, the reduced temperature difference causes global winds to weaken and lead to a more meandering jet stream.
Some of these changes can create conditions such as persistent high pressure systems and atmospheric blockage that lead to more intense heat waves. Heat domes over the southern and southern plains in June and in the west in September are two examples.
Warming can be further amplified by positive feedbacks.
For example, higher temperatures tend to dry out the soil, and lower soil moisture reduces the earth’s heat capacity, making it easier to warm. More frequent and persistent heat waves lead to excessive evaporation, combined with less precipitation in some areas, causing more severe droughts and more frequent wildfires.
Higher temperatures increase the atmosphere’s ability to hold moisture at a rate of about 7% per degree Celsius. This increase in humidity leads to more precipitation.
In addition, rainwater systems are powered by latent heat, which is the large amount of energy released when water vapor condenses into liquid water. Increasing the moisture content of the atmosphere also increases the latent heat of thunderstorm systems, increasing their intensity. Extremely heavy or persistent rainfall leads to increased flooding and landslides, with devastating social and economic consequences.
While it is difficult to directly link specific extreme events to climate change, when these supposedly rare events occur with greater frequency in a warming world, it is difficult to ignore the changing state of our climate.
The new abnormal
This year could provide a glimpse into our near future as these extreme weather events become more frequent.
To say this is the “new normal”, however, is misleading. This suggests that we have reached a new steady state, and that is far from the truth. Without a serious effort to reduce greenhouse gas emissions, this trend of more extreme events will continue.
Shuang-Ye Wu is a professor of geology and environmental geosciences at the University of Dayton.
This commentary was originally posted by The Conversation—US weather disasters of 2022, from storms and floods to heat waves and droughts
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