Cyclone Chido fueled by ocean warming linked to climate change

Unusually warm ocean temperatures contributed to Cyclone Chido’s intensification. Climate Central’s Climate Shift Index: Ocean (Ocean CSI), which quantifies the influence of climate change on sea surface temperatures, found that the storm developed and intensified over waters whose elevated temperatures were made as much as 92 times more likely by human-caused climate change.

Key takeaways

1. Cyclone Chido intensified as it passed over waters that were, on average, 1.1°C (2.0°F) warmer than they would have been without human-caused climate change.

2. In the hours prior to making landfall, ocean temperatures were 1.2°C (2.2°F) higher than they would have been without human-caused climate change.

3. Human-caused climate change made these temperatures as much as 92 times more likely.

Expert quote

"Attribution science shows the influence of global warming on Cyclone Chido. Unusually high sea surface temperatures made more than 50 times more likely because of climate change provided fuel for this storm to grow more intense and more destructive." — Joseph Giguere, research associate at Climate Central

What is significant about Cyclone Chido?

Cyclone Chido reached peak intensity in the Indian Ocean, northeast of Madagascar, on Thursday, December 12, with sustained winds of 69 m/s (155 mph), equivalent to a Category 4 hurricane. It was the most intense tropical cyclone on record to make landfall in the French territory of Mayotte.

How did ocean temperatures play a role?  

As ocean temperatures warm in response to climate change, they provide unnatural extra fuel for tropical cyclones to intensify, and increase the likelihood that storms will undergo rapid intensification. Increased sea surface temperatures enable higher levels of local humidity, atmospheric instability, and potential intensity (e.g. Emanuel 2006).

It is important to note that the Ocean CSI does not directly quantify how climate change affected Cyclone Chido’s intensity; instead it speaks to the ocean conditions that allowed Chido to intensify. 

On average, temperatures along the track were made 1.1°C (2.0°F) warmer by human caused climate change (Figure 1). The strongest climate-driven warming signal corresponded with the period when Chido was rapidly intensifying into a tropical cyclone on December 10 and 11. In the hours prior to making landfall, temperatures were 1.2°C (2.2°F) higher than they would have been without human-caused climate change, the highest value along the track.

At three points along Chido’s track, the storm passed through areas with notable spikes in Ocean CSI: prior to becoming a tropical storm (December 8); after developing into a tropical cyclone (December 11); and in the hours prior to making landfall (December 14) (Figure 1). The sea surface temperatures Chido encountered at these three stages were made more than 66, 81, and 92 times more likely to occur today than in a world without climate change. 

We conclude that warmer sea surface temperatures along the track of Cyclone Chido were strongly influenced by climate change, which affected Chido’s environment and made it more likely for the storm to develop and intensify throughout its lifetime.

Methods

The Climate Shift Index: Ocean is computed using observations, models, and peer-reviewed attribution techniques, as described in Giguere et al. (2024).

Figure 1. Climate driven warming (top) and increase in likelihood of sea surface temperatures occurring as a result of climate change (bottom). Data from Climate Central’s Ocean CSI. Additionally, both figures present cyclone intensity (as a red, dashed line).

Major funding provided by the Bezos Earth Fund.