For years, the world has been steadily warming alongside rising greenhouse gas emissions, caused by the burning of fossil fuels.

2023 was no exception.

Things started out slow. January 2023 was warmer than usual, but still only the seventh warmest January on record.

By May, things were heating up. Halfway through the year, temperatures became extraordinary.

June registered as the warmest June on record since scientists began keeping track in the mid-19th century.

July broke the monthly record as well.

And again in August.

September 2023 wasn’t simply the warmest September on record, but “far and away the most atypically warm month of any in NOAA’s 174 years of climate keeping,” said U.S. National Oceanic and Atmospheric Administration scientist Sarah Kapnick.

October was the fifth consecutive record-breaker, sealing the fate for 2023 to be declared as the warmest year ever recorded.

The Hottest Year

How heat fueled extreme weather across the world in 2023

One after another, records have fallen in 2023 alongside skyrocketing temperatures.

Deadly floods, heatwaves and storms have unfolded against the backdrop of what climate scientists say is set to be the world’s hottest year on record, with observations stretching back to the 1800s.

The world, on average, has seen about 1.46 degrees Celsius (2.63 degrees Fahrenheit) of warming above pre-industrial temperatures this year, with global greenhouse gas emissions hitting new highs.

Every new benchmark brings crippling economic losses and untold human suffering to communities across the world.

This year’s added warming has been like pouring gasoline on a fire. Extremes became more extreme. Warmer ocean waters fed stronger storms. Heatwaves persisted for weeks instead of days. And wildfires, feeding on dry forests and high temperatures, burned out of control.

An El Nino climate pattern, which emerged in the Eastern Pacific in June, is making things worse, scientists said. It’s boosting the warming caused by climate change, unleashing more catastrophic extremes.

As world leaders seek to bring an end to fossil fuels at the United Nations climate summit COP28 in Dubai, scientists say the record-breaking extremes of 2023 serve as a sobering warning of what’s to come if society doesn’t curtail its use of coal, oil and gas.

Boiling Point

In October, Otis began swirling off Mexico’s southern Pacific coast. In a matter of hours, it went from a fairly weak tropical storm to a major hurricane before barrelling into the city of Acapulco, leaving dozens dead. It was the first eastern Pacific hurricane to remain at Category 5 after making landfall.

The speed and strength of Hurricane Otis

Model forecasts initialized one day prior to landfall failed to predict the strength of the storm, as it surged from tropical storm to Category 5 hurricane in under 24 hours.

Chart showing that model forecasts initialized one day prior to landfall failed to predict the strength of the hurricane Otis, as it surged from tropical storm to Category 5 hurricane in under 24 hours. The models all predicted the storm to stay in the tropical storm category, while the actual sustained wind speed rose to 166 mph.

Scientists blamed much warmer than usual ocean temperatures in October, with sea surface temperatures off the eastern coast of Mexico at around 31C (88F) as Otis gathered strength.

Hot water at greater depths, scientists said, may also have given Otis an extra boost.

Research released just days before Otis hit hinted at a worrying trend in other oceans. The study, published in the journal Scientific Reports, found Atlantic hurricanes are now far more likely to gain steam in a short window of time than they were decades ago.

Still, it will take some time for scientists to figure out exactly how climate change supercharged Otis.

Sea surface temperature fueled Otis

Extremely warm ocean water helped to propel Otis from tropical storm to Category 5 hurricane with sustained wind speeds of 166 mph (267 kph) in 24 hours, earning it recognition as one of the most rapidly intensifying storms ever recorded.

Map showing sea surface temperatures the day before hurricane Otis made landfall and its path from open sea into Aculpoco. The path crosses over a particularly warm 88 degree fahrenheit patch of ocean the day before landfall which helped fuel the surprisingly rapid intensification of the storm.

Deluged Cities

When the remnants of Typhoon Doksuri hit northeastern China midway through the summer, it deluged cities from Beijing to Tianjin. Flood waters submerged streets and tore through buildings, displacing more than 1 million people from their homes.

Typhoon brings historic rains to China

Heavy rainfall unleashed floods across parts of China in the wake of Typhoon Doksuri. Maximum 24-hour rainfall recorded between July 29 and Aug. 4 compared with historic single-day records in select national-level monitoring stations in Beijing and Hebei.

Chart showing maximum 24 hour rainfall totals at selected locations in Beijing and Hebei. The storms between July 29 and Aug. 4 recorded rainfall that eclipsed the all-time 24 hour rainfall records at these locations by between 1 and almost 5.5 inches.

The typhoon — the same weather phenomenon as a cyclone or hurricane — was part of a one-two punch, emerging after a period of record-breaking heat on land in northern China.

Scientists say it’s not surprising to have seen record-breaking rainfall following such heatwaves. After all, warmer air can hold more moisture. When clouds burst, they send a torrent of water rushing down.

Heatwaves on blast

Millions sweltered under stifling temperatures with the arrival of summer in the Northern Hemisphere — and the world’s warmest month ever recorded in July. Large swathes of North America, Europe and China saw blistering temperatures that triggered public health warnings, briefly shuttered tourist sites and helped to fuel deadly wildfires.

A remote township in China’s arid northwest hit 52.2C (126F), setting a new record for the country. Beijing suffered through 27 consecutive days of temperatures above 35C (95F), leading to a temporary ban on outdoor work in the Chinese capital.

Halfway across the world, the United States also sizzled. Phoenix, Arizona, saw a record 31-day streak of temperatures of 43C (110F) or greater from June 30 to July 30.

And in parts of Spain, Greece and Italy, temperatures climbed upwards of 45C (113F).

Phoenix registered a total of 55 days with temperatures reaching 43C (110F) or higher this summer — surpassing the last record set in 2020 by 2 days.

A thermal camera registers surface temperatures during the heatwave in Phoenix, showing yellows and whites for the hottest areas while blues and purples are cooler.

A thermal image with the same hiker overlooking Phoenix shows the image of the landscape in a range of colors that represent heat, with the hot ground being brightest, while the hiker and the top of the sky shows up as cooler darker colors.

Asphalt and concrete in direct sunlight can often reach surface temperatures as high as 82C (180F) on the hottest days, said surgeon Kevin Foster who directs the Arizona Burn Center in Phoenix.

An overhead image shows Phoenix residents walking across a city street in downtown during a heatwave in July

A thermal camera registered a street temperature of 65C (150F) on July 26 at 12:24 p.m. Doctors in Phoenix said they treated numerous patients who suffered burns from falling on the ground due to extreme surface temperatures.

A thermal image shows a similar set of pedestrians crossing the street, with the street a very bright yellow indicating extreme heat and a crosshair from the thermal camera registering the surface at 65C. The pedestrians show up as dark purple and black silhouettes indicating they are much cooler than the surface.

Firefighter EMT personnel assist a man who collapsed during the 27th day of the heatwave in Phoenix, Arizona.

Firefighter EMT personnel load a man on a gurney into the back of an ambulance in Phoenix. The man collapsed during the 27th day of the heatwave this July.

Heat is the leading weather-related cause of death in the United States, outpacing hurricanes by a factor of 8 to 1, according to the U.S. Center for Disease Control and Prevention. In Phoenix, the thermal camera registered a surface temperature of 49C (121F) at 4:03 p.m. on July 26, with an air temperature of 36C (97F), according to the National Weather Service.

The thermal image shows the rescue personnel loading the man on the gurney into the back of an ambulance while the camera registers a temperature of 49C.

Climate change is making heatwaves even worse.

The heatwaves that unfolded across three continents this summer would have been extremely rare without climate change, according to the World Weather Attribution (WWA) group, a team of international scientists who tease out the role played by climate change in extreme events.

In China, the heatwave would have been a 1-in-250 year event, they said.

In Phoenix, the summer heat of 2023 would have been virtually impossible without human-caused climate change.

World on fire

As the world registered its warmest June, July and August on record, fires broke out across the globe.

In early June, smoke from eastern Canadian wildfires blanketed cities across North America, creating hellish orange skies and triggering dangerous air quality alerts for the region. Canada went on to experience its worst wildfire season on record.

Daily organic carbon released into the atmosphere

A map of organic carbon being released from wildfires for the months of May through August.

More than 45 million acres (18.4 million hectares) of forest have burned across the country as of November 2023, or about 5% of Canadian forests, impacting woodlands from Alberta to Quebec to Nova Scotia. The fires release more than 400 million metric tons of carbon, nearly triple the previous record set in 2014 of 138 million metric tons.

Scientists said climate change made the fires in Eastern Canada from May through July at least twice as likely.

Two charts with one that shows the cumulative weekly wildfire carbon emissions in Canada. Starting in May, the amount of carbon emissions goes from zero to 400 million metric tons by September. The second chart shows the annual acres burned by wildfires in Canada. From 2012 to 2022, each year burned around 10 million acres (4 million hectares). In 2023, more than 45 million acres (18.4 million hectares) burned.

Apocalyptic fires also blazed through northeastern Greece following weeks of high heat which saw the Acropolis briefly close to tourists. The fires were the worst on European soil in decades, according to the EU’s Copernicus Climate Change Service, burning an area larger than New York City and costing the country some 1.66 billion euros ($1.8 billion).

Endless summer

The warm temperatures experienced so far throughout the year show no signs of letting up.

November once again was the warmest November ever recorded. And on Nov. 17 and 18, the Earth’s global average surface temperature was more than 2C (3.6F) higher than pre-industrial levels — the first time scientists have ever recorded such a reading.

Brazil — currently in the Southern Hemisphere’s summer — recorded its highest temperature ever as the southeastern town of Aracuai simmered at 44.8C (112.6F) on Nov. 19 as the full weight of El Nino bore down.

With El Nino set to reach its full strength in the Northern Hemisphere winter, more extreme weather events are likely to be unleashed around the world in 2024.

Photos by

Carlos Barria / Reuters

Edited by

Julia Wolfe, Katy Dagle and Lisa Shumaker