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  • Written by Shuang-Ye Wu, Professor of Geology and Environmental Geosciences, University of Dayton
2023's extreme storms, heat and wildfires broke records – a scientist explains how global warming fuels climate disasters

The year 2023 was marked by extraordinary heat, wildfires and weather disasters.

In the U.S., an unprecedented heat wave[1] gripped much of Texas and the Southwest with highs well over 100 degrees Fahrenheit (37.8 Celsius) for the entire month of July.

Historic rainfall in April flooded Fort Lauderdale, Florida[2], with 25 inches of rain in 24 hours. A wave of severe storms in July sent water pouring into cities across Vermont[3] and New York. Another powerful system in December swept up the Atlantic coast with hurricane-like storm surge[4] and heavy rainfall. California faced flooding and mudslides from a series of atmospheric rivers[5] early in the year, then was hit in August by a tropical storm[6] – an extremely rare event there.

Wildfires ravaged Hawaii[7], Louisiana[8] and several other states. And Canada’s worst fire season[9] on record sent thick smoke[10] across large parts of North America.

A man in shorts in flipflops walks among burned out cars. Not much remains of the houses.
A person walks through a scene of destruction after a wildfire left almost the entire city of Lahaina, Hawaii, in ashes in August 2023. AP Photo/Rick Bowmer[11]

Globally, 2023 was the warmest year on record[12], and it wreaked havoc around the world. El Niño[13] played a role, but global warming[14] is at the root of the world’s increasing extreme weather.

So, how exactly is global warming linked to fires, storms and other disasters? I am an atmospheric scientist[15] who studies the changing climate. Here’s what you need to know.

Dangerous heat waves and devastating wildfires

When greenhouse gases, such as carbon dioxide from vehicles and power plants, accumulate in the atmosphere, they act like a thermal blanket[16] that warms the planet.

These gases let in high-energy solar radiation while absorbing outgoing low-energy radiation in the form of heat from the Earth. The energy imbalance[17] at the Earth’s surface gradually increases the surface temperature of the land and oceans.

How the greenhouse effect functions.

The most direct consequence of this warming is more days with abnormally high temperatures, as many countries saw in 2023.

Extreme heat waves hit large areas of North America, Europe and China, breaking many local high temperature records. Phoenix[18] went 30 days with daily high temperatures at 110 F (43.3 C) or higher[19] and recorded its highest minimum nighttime temperature, with temperatures on July 19 never falling below 97 F (36.1 C).

Although heat waves result from weather fluctuations, global warming has raised the baseline[20], making heat waves more frequent, more intense and longer-lasting.

Maps and charts show extreme heat events increasing in many parts of the U.S., both in length of heat wave season and in number of heat waves per year.
The number of multi-day extreme heat events has been rising. U.S. Global Change Research Program. U.S. Global Change Research Program[21]

That heat also fuels wildfires.

Increased evaporation removes more moisture from the ground, drying out soil, grasses and other organic material, which creates favorable conditions for wildfires[22]. All it takes is a lightning strike or spark from a power line to start a blaze.

Canada lost much of its snow cover[23] early in 2023, which allowed the ground to dry and vast fires to burn through the summer. The ground was also extremely dry in Maui in August when the city of Lahaina, Hawaii, caught fire[24] during a windstorm and burned.

How global warming fuels extreme storms

As more heat is stored as energy in the atmosphere and oceans, it doesn’t just increase the temperature – it can also increase the amount of water vapor[25] in the atmosphere.

When that water vapor condenses to liquid and falls as rain, it releases a large amount of energy. This is called latent heat[26], and it is the main fuel for all storm systems.

Two older adults look out a window over a yard turned to mud. The mudline on the house is almost up to the window sill, and the garage's doors have been torn off and are leaning down.
Tropical Storm Hilary flooded several areas in Southern California, stranding people for days. Josh Edelson/AFP via Getty Images[27]

When temperatures are higher and the atmosphere has more moisture, that additional energy can fuel stronger, longer-lasting storms[28]. This is the main reason for 2023’s record-breaking storms. Nineteen of the 25 weather and climate disasters that caused over US$1 billion in damage[29] each through early December 2023 were severe storms, and two more were flooding that resulted from severe storms.

Tropical storms are similarly fueled by latent heat coming from warm ocean water. That is why they only form when the sea surface temperature reaches a critical level of around 80 F[30] (27 C).

With 90% of the excess heat[31] from global warming being absorbed by the ocean, there has been a significant increase in the global sea surface temperature[32], including record-breaking levels in 2023.

Line chart shows daily ocean temperature records for every year since 1981, 2023 was far beyond any other year starting in mid-May. Global ocean heat in 2023 went far beyond any other year in over four decades of records. ClimateReanalyzer.org, Climate Change Institute, University of Maine, CC BY[33][34]

Higher sea surface temperatures can lead to stronger hurricanes[35] and longer hurricane seasons[36]. They can also lead to the faster intensification[37] of hurricanes.

Hurricane Otis, which hit Acapulco, Mexico, in October 2023, was a devastating example. It exploded in strength[38], rapidly intensifying from a tropical storm to a destructive Category 5 hurricane in less than 24 hours. With little time to evacuate and buildings not designed to withstand a storm that powerful[39], more than 50 people died. The hurricane’s intensification was the second-fastest ever recorded[40], exceeded only by Hurricane Patricia in 2015.

A recent study found that North Atlantic tropical cyclones’ maximum intensification rates increased 28.7%[41] between the 1971-1990 average and the 2001-2020 average. The number of storms that spun up from a Category 1 storm or weaker to a major hurricane within 36 hours more than doubled.

The Mediterranean also experienced a rare tropical-like cyclone[42] in September 2023 that offers a warning of the magnitude of the risks ahead – and a reminder that many communities are unprepared. Storm Daniel became one of the deadliest storms of its kind when it hit Libya[43]. Its heavy rainfall overwhelmed two dams, causing them to collapse, killing thousands of people[44]. The heat and increased moisture[45] over the Mediterranean made the storm possible.

Cold snaps have global warming connections, too

It might seem counterintuitive, but global warming can also contribute to cold snaps[46] in the U.S. That’s because it alters the general circulation of Earth’s atmosphere.

The Earth’s atmosphere is constantly moving in large-scale circulation patterns in the forms of near-surface wind belts, such as the trade winds, and upper-level jet streams. These patterns[47] are caused by the temperature difference between the polar and equatorial regions.

As the Earth warms, the polar regions are heating up more than twice as fast[48] as the equator. This can shift weather patterns, leading to extreme events in unexpected places. Anyone who has experienced a “polar vortex event” knows how it feels when the jet stream dips southward, bringing frigid Arctic air and winter storms, despite the generally warmer winters.

In sum, a warmer world is a more violent world, with the additional heat fueling increasingly more extreme weather events.

References

  1. ^ unprecedented heat wave (earthobservatory.nasa.gov)
  2. ^ flooded Fort Lauderdale, Florida (theconversation.com)
  3. ^ cities across Vermont (theconversation.com)
  4. ^ hurricane-like storm surge (www.washingtonpost.com)
  5. ^ atmospheric rivers (theconversation.com)
  6. ^ hit in August by a tropical storm (theconversation.com)
  7. ^ Wildfires ravaged Hawaii (theconversation.com)
  8. ^ Louisiana (apnews.com)
  9. ^ worst fire season (www.cbc.ca)
  10. ^ sent thick smoke (theconversation.com)
  11. ^ AP Photo/Rick Bowmer (newsroom.ap.org)
  12. ^ warmest year on record (climate.copernicus.eu)
  13. ^ El Niño (theconversation.com)
  14. ^ global warming (www.carbonbrief.org)
  15. ^ an atmospheric scientist (www.researchgate.net)
  16. ^ act like a thermal blanket (climate.nasa.gov)
  17. ^ energy imbalance (theconversation.com)
  18. ^ Phoenix (www.nasa.gov)
  19. ^ 110 F (43.3 C) or higher (apnews.com)
  20. ^ global warming has raised the baseline (www.worldweatherattribution.org)
  21. ^ U.S. Global Change Research Program (www.globalchange.gov)
  22. ^ creates favorable conditions for wildfires (theconversation.com)
  23. ^ lost much of its snow cover (theconversation.com)
  24. ^ Lahaina, Hawaii, caught fire (theconversation.com)
  25. ^ increase the amount of water vapor (theconversation.com)
  26. ^ latent heat (wxguys.ssec.wisc.edu)
  27. ^ Josh Edelson/AFP via Getty Images (www.gettyimages.com)
  28. ^ stronger, longer-lasting storms (theconversation.com)
  29. ^ over US$1 billion in damage (www.ncei.noaa.gov)
  30. ^ critical level of around 80 F (www.noaa.gov)
  31. ^ 90% of the excess heat (climate.nasa.gov)
  32. ^ global sea surface temperature (climatereanalyzer.org)
  33. ^ ClimateReanalyzer.org, Climate Change Institute, University of Maine (climatereanalyzer.org)
  34. ^ CC BY (creativecommons.org)
  35. ^ stronger hurricanes (www.gfdl.noaa.gov)
  36. ^ longer hurricane seasons (www.lsu.edu)
  37. ^ faster intensification (doi.org)
  38. ^ exploded in strength (www.nesdis.noaa.gov)
  39. ^ buildings not designed to withstand a storm that powerful (theconversation.com)
  40. ^ second-fastest ever recorded (www.nesdis.noaa.gov)
  41. ^ maximum intensification rates increased 28.7% (doi.org)
  42. ^ a rare tropical-like cyclone (modis.gsfc.nasa.gov)
  43. ^ hit Libya (wmo.int)
  44. ^ thousands of people (reliefweb.int)
  45. ^ heat and increased moisture (www.washingtonpost.com)
  46. ^ contribute to cold snaps (theconversation.com)
  47. ^ These patterns (theconversation.com)
  48. ^ more than twice as fast (scied.ucar.edu)

Authors: Shuang-Ye Wu, Professor of Geology and Environmental Geosciences, University of Dayton

Read more https://theconversation.com/2023s-extreme-storms-heat-and-wildfires-broke-records-a-scientist-explains-how-global-warming-fuels-climate-disasters-217500

Metropolitan republishes selected articles from The Conversation USA with permission

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