CNN –
In the hottest year on record, dozens of extreme weather events were the fingerprints of a changing climate in a warming world.
Without heat there would be no weather; Heat is energy, and the weather is an expression of that energy, an atmosphere trying to balance itself. But too much heat in the system pushes the boundaries of what is technically possible and pushes it to extremes.
So it's perhaps no surprise that this year's record-breaking heat has been a “throughput line” in many of 2023's most brutal weather events, Kristina Dahl, a climate scientist at the Union of Concerned Scientists, told CNN.
“Climate change affects our weather on Earth every day,” Dahl said. “In my opinion, the burden of proof now is to show that climate change has not influenced any event, because it just so clearly influences everything around us.”
This year's extreme weather events are not unique – they are a sign of what is to come.
“These types of events will continue to become more frequent and more severe as we continue to warm the planet,” Dahl said.
These are just a few of the most notable examples of what a warming planet's extreme weather may look like in 2023.
Not only was record heat in the air, it also reached the oceans, which absorb most of the Earth's excess heat.
“Sea surface temperatures were just so much warmer than any previous year on record,” Dahl said.
Warm water acts as food for storms, and the exceptionally warm seawater in 2023 didn't just create more storms In the Atlantic by neutralizing the storm-dampening effect not only led to a strengthening El Niño, but also led to an explosive strengthening of storms forming around the world.
This explosive amplification, known as rapid intensification, becomes more likely as the atmosphere warms.
In 2023, a total of twelve tropical cyclones rapidly intensified in the Atlantic and Eastern Pacific basins.
NOAA/Getty Images
In this NOAA image captured by the GOES satellite, Hurricane Lee crosses the Atlantic Ocean as it heads west on September 8, 2023.
Lee was the strongest Atlantic hurricane this season, peaking in September as a rare Category 5 open-ocean hurricane after its winds increased to a staggering 85 miles per hour in 24 hours. The outbreak made Lee the Atlantic the third fastest rapidly intensifying storm on record.
Idalia, the only hurricane to make landfall in the U.S. this year, was another example of storms intensifying more frequently and quickly just before landfall.
The storm briefly reached Category 4 status before devastating Florida's Big Bend region as a Category 3 hurricane – the strongest storm to hit there in more than 125 years.
Felix Marquez/AP
An overturned semi-truck lies on the shoulder of a highway on the outskirts of Acapulco, Mexico, on Friday, October 27, 2023, after Hurricane Otis.
Hurricane Otis in the Eastern Pacific was the most extreme example of rapid strengthening in both basins this year. Otis' winds increased by a staggering 115 miles per hour in the 24 hours before the devastating Category 5 landfall in Acapulco, Mexico, in October.
Otis was the strongest Pacific storm ever to hit Mexico, coming just two weeks after Category 4 Hurricane Lidia – also a fast intensifier – made landfall just south of Puerto Vallarta as another of Pacific Mexico's strongest storms.
The rapid intensification also helped Hurricane Hilary maintain enough strength to hit California as a tropical storm – the first in the state since 1997. Hilary triggered a flood that broke tropical rainfall records in some states and caused extreme flooding that occurred in one of the driest states on earth lasted for months.
Unusual wildfire behavior marked the year, both where the fires started and where they didn't.
According to statistics from the National Interagency Fire Center, wildfires in the U.S. typically burn 7 to 8 million acres of land each year, but in 2023 they charred just 2.6 million acres.
That was due in part to a soggy start to the year in the typically fiery West, keeping wildfires to a minimum after years of destruction. One season doesn't make a trend, and as the world warms, wildfires are becoming more frequent and more severe – particularly in the West, the latest National Climate Assessment says.
Still, the season proved deadly and destructive as intense heat combined with a lack of rain parched the ground and left normally wet parts of the United States and much of Canada vulnerable to fires.
Patrick T. Fallon/AFP/Getty Images
The Ganer family searches through the ashes of their family home on Malolo Place after a wildfire in Lahaina, west Maui, Hawaii on August 11, 2023.
In August, tragedy struck on Hawaii's island of Maui in the form of the blazing Lahaina Inferno.
Wind-driven flames tore through drought-parched invasive grasses so quickly and engulfed everything in their path that some people fleeing for their lives had no choice but to jump into the Pacific Ocean. Many were unable to escape, and the Lahaina Fire was the deadliest on U.S. soil in more than 100 years.
Louisiana is one of the wettest states in the US, but after a summer of endless heat, no tropical systems and little rain, the ground turned to tinder. The massive drought peaked in November, with 75% of the state experiencing exceptional drought – the most extensive such area in the state's history.
As a result, the state experienced one of the worst fire seasons in decades, according to data provided to CNN by the Louisiana Department of Agriculture and Forestry. The fires burned into the fall in the southern half of the state, their smoke triggering “super fog” that led to a fiery, deadly pileup near New Orleans.
David Dee Delgado/Getty Images
A smoky Manhattan is seen on June 7, 2023, as wildfires in Canada enveloped New York City in toxic smoke.
Large parts of the USA were also affected by fires, even if they were not burning there.
Canada's worst wildfire season on record burned an area roughly the size of North Dakota, sending toxic plumes of smoke from the numerous major fires across the United States and as far away as Europe.
The smoke blocked the sun and caused a drop in air quality across the Northeast in June. An apocalyptic orange sky enveloped New York City as the city briefly experienced the worst air pollution in the world.
This summer, heat records were broken across the Northern Hemisphere, including much of the United States. In the US, a series of heat domes roasted the southern and central parts of the country.
The heat index topped 130 degrees in Kansas, New Orleans reached its highest temperature ever recorded – 105 degrees – and much of Texas and Florida sweltered under exceptionally sustained extreme heat.
But one city was emblematic of an extreme summer of heat that scientists said would be “virtually impossible” without human-caused climate change: Phoenix.
July in Phoenix was that Hottest month since records began for every US city. After brutally hot days and record-breaking nights, the city's average temperature this month was a staggering 102.7 degrees Fahrenheit.
Phoenix experienced an unprecedented 31 consecutive days of high temperatures exceeding 110 degrees.
Liliana Salgado/Portal
A billboard displays the temperature as Phoenix broke the heat record of over 110 degrees Fahrenheit for consecutive days on July 18, 2023.
The heat took its toll.
In Maricopa County, where Phoenix is located, at least 579 people died of heat-related causes in 2023. This was the deadliest year for heat there since the county began tracking in 2003.
Days in which temperatures rise above 100 degrees are becoming more common in many major U.S. cities as global temperatures rise, but Phoenix saw the biggest increase of all. Compared to the historical average, the city's temperature is above 100 degrees an average of 18 more days per year. That equates to about 111 days above 100 degrees per year.
Floods kill thousands
Storm Daniel caused deadly flooding in Greece, Turkey and Bulgaria in September before moving across the Mediterranean and targeting Libya. Fueled by the warm waters of the Mediterranean, Daniel became the “Medican” – a storm with characteristics similar to hurricanes and typhoons.
The storm unleashed torrential rains across Libya, with one city receiving 16 inches of rain in just 24 hours. The result was devastating floods in which an estimated 4,000 people died.
Mahmoud Turkia/AFP/Getty Images
An aerial photo shows Derna, Libya, on September 18, 2023, after deadly flash floods.
The city of Derna was hardest hit. The floods there caused two dams to burst and unleashed a massive wave of water that washed away much of the city's core.
The World Weather Attribution Initiative – a team of scientists who analyze the role of climate change following extreme weather events – has found that pollution caused by a warming planet makes Libya's deadly rains up to 50 times more likely and 50% worse.
A drug or even a tropical system is not necessary to trigger devastating floods in a warming world. As the atmosphere continues to warm, it can absorb more moisture like a towel and then release it in the form of even heavier torrents of flooding rain.
This scenario has played out multiple times in the U.S.: A series of deadly atmospheric rivers flooded California in January and March; The catastrophic flooding in July turned Vermont's capital, Montpelier, into a raging river and became fatal in New York State; and in September, New York City received a month's worth of rain in just a few hours, sending foot-high floods through parts of the city.
CNN's Laura Paddison and Nadeen Ebrahim contributed to this report.