Hurricane Beryl: Record-breaking sign of warming world

Hurricane Beryl is wreaking havoc in parts of the Caribbean – and putting the role of climate change under the spotlight.

With maximum sustained wind speeds of more than 160mph (257km/h), it became the earliest category five Atlantic hurricane in records going back around 100 years.

In fact, there has only been one previous recorded case of a category five Atlantic hurricane in July – Hurricane Emily, on 16 July 2005.

The causes of individual storms are complex, making it difficult to fully attribute specific cases to climate change.

But exceptionally high sea surface temperatures are seen as a key reason why Hurricane Beryl has been so powerful.

Usually, such strong storms only develop later in the season, after the seas have heated up through the summer.

Hurricanes generally need the sea surface to be at least 27C in order to have a chance of developing. As the map below shows, waters along Hurricane Beryl’s path have been exceptionally warm for this early in the season.

All else being equal, warmer seas mean more powerful hurricanes, because the storms can pick up more energy, enabling higher wind speeds.

“We know that as we warm the planet, we’re warming our sea surface temperatures as well,” explains Andra Garner, an assistant professor at Rowan University in the US.

"And we know that those warm ocean waters are a critical fuel source for hurricanes."

In the main Atlantic hurricane development region, the ocean heat content – the energy stored throughout the water column - is at levels not usually seen until September.

That is when the Atlantic hurricane season is usually at its most active, as the sea surface is typically at its warmest at the end of summer.

This is illustrated by the chart below, where a dot represents a major hurricane between 1940 and 2024. As you can see, most major hurricanes happen in late August and September, and earlier ones are very rare.

While a category five hurricane is unheard of this early in the season, its strength fits into the broader picture of how these storms are changing in a warming world.

The number of hurricanes has not been increasing, but a higher proportion of them are expected to reach the highest categories globally as temperatures rise.

“Although it is uncertain to what extent climate change contributed to the early formation of Hurricane Beryl, our climate models suggest that the mean intensity of hurricanes will increase in the future due to enhanced global warming,” explains Hiroyuki Murakami, research scientist at Noaa’s Geophysical Fluid Dynamics Laboratory.

Another factor to consider this year is regional weather patterns.