2023 weather: heatwaves, floods, and storms wreak havoc globally

2023, there were many heat, fire, and weather disasters. In the U.S., Texas and the Southwest had a heat wave with temperatures over 37.8 Celsius for all of July.

April, Fort Lauderdale, Florida had a historic flood with 25 inches of rain in one day. In July, severe storms caused flooding in Vermont and New York. A strong storm system caused flooding and heavy rain along the Atlantic coast in December. The West Coast had flooding and mudslides at the start and end of the year due to atmospheric rivers. In August, California experienced a tropical storm, which is very rare.

Wildfires severely damaged Hawaii, Louisiana, and other states. Canada also experienced its worst fire season ever, causing thick smoke to spread over much of North America.

In 2023, the world experienced its highest recorded temperatures, causing chaos globally. While El Niño contributed to this, the main cause of the increasingly severe weather is global warming.

So, how exactly does global warming link to fires, storms and other disasters? I, an atmospheric scientist, study the changing climate. Here's the information you need to understand.

Destructive heat and wildfires

Greenhouse gases, such as carbon dioxide from vehicles and power plants, accumulate in the atmosphere and act like a thermal blanket, warming the planet.

These gases admit high-energy solar radiation and absorb outgoing low-energy radiation in the form of heat from the Earth. The energy imbalance at the Earth's surface gradually raises the surface temperature of the land and oceans.

As many countries saw in 2023, the most direct consequence of this warming is that it causes more days with abnormally high temperatures.

Large areas of North America, Europe, and China experienced extreme heat waves that broke many local high temperature records. Phoenix recorded its highest minimum nighttime temperature, with the temperatures never falling below 97 F (36.1 C) on July 19. Also, for 30 days, the daily high temperatures in Phoenix remained at 110 F (43.3 C) or higher.

While heat waves are a result of weather changes, global warming has increased the base temperature, leading to more frequent, intense, and prolonged heat waves.

This heat also contributes to wildfires.

Increased evaporation dries out the soil, grass, and other organic materials, creating ideal conditions for wildfires. A lightning strike or a spark from a power line is all it takes to start a fire.

In 2023, Canada lost much of its snow cover early, allowing the ground to dry and large fires to burn throughout the summer. Similarly, the ground was extremely dry in Maui in August when a windstorm caused a fire in the city of Lahaina, Hawaii.

How global warming fuels extreme storms

As the atmosphere and oceans store more heat as energy, it doesn't just increase the temperature - it can also increase the amount of water vapor in the atmosphere.

Water vapor condensing to liquid and falling as rain releases a large amount of energy. People commonly refer to this as latent heat, and it acts as the main fuel for all storm systems.

Higher temperatures and increased atmospheric moisture can fuel stronger, longer-lasting storms. This is the primary cause of the record-breaking storms in 2023. Severe storms accounted for nineteen of the 25 weather and climate disasters causing over US$1 billion in damage each until early December 2023, while severe storms resulted in two further flooding events.

Latent heat from warm ocean water similarly fuels tropical storms. They only form when the sea surface temperature reaches a critical level of around 80 F (27 C).

In October 2023, Hurricane Otis rapidly escalated from a tropical storm to a Category 5 hurricane in less than 24 hours, devastating Acapulco, Mexico with its power, and causing over 50 fatalities due to inadequate building structures and insufficient evacuation time. It was the second fastest intensification ever recorded after Hurricane Patricia in 2015.

A recent study has found an increase of 28.7% in the maximum intensification rates of North Atlantic tropical cyclones between the average of 1971-1990 and the average of 2001-2020. Additionally, the number of storms escalating from a Category 1 storm or weaker to a major hurricane within 36 hours has more than doubled.

In September 2023, a rare tropical-like cyclone, Storm Daniel, hit the Mediterranean, highlighting grave future risks and communities' lack of preparedness. This fatal storm struck Libya, causing dam collapses due to heavy rain, resulting in thousands of casualties.

Cold snaps have global warming connections, too

It might seem counterintuitive, but global warming can also contribute to cold snaps 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 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 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.

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