Climate change: Even weak Hurricanes are getting stronger

Hurricanes are expected to become stronger as the weather warms, with more of them becoming major storms. But it’s not just the biggest cyclones that are getting worse. New research finds that weak tropical cyclones, including low-category tropical storms and hurricanes, are intensifying over time.

Tropical cyclones

The study, published Wednesday in the journal Nature, uses data collected by thousands of scientific instruments scattered across the world’s oceans. Tropical cyclones leave telltale signs in the water, speeding up ocean currents as they move. Scientists can estimate a storm’s wind speed by measuring these currents.

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It is one of the first studies to use direct measurements from the ocean, rather than satellite data, to track changes in tropical cyclone intensity over time.

That’s important, say the authors. Satellites have been invaluable in tracking hurricane activity around the world for the past 40 years, but they do have their limitations. Satellites can show scientists where storms are forming and where they are moving, but they are less reliable when it comes to exact measurements of a storm’s intensity.

Scientists often rely on aircraft missions to gather up-close information about a hurricane’s wind speed and other physical characteristics. But it’s not possible to collect that kind of data for every single cyclone that forms around the world.

This makes it difficult to track long-term trends in hurricane intensity.

Category 1 tropical storms and hurricanes

Still, some previous studies have tried, and there are some indications that tropical cyclones are getting stronger over time. A 2020 study found that the proportion of hurricanes that become major storms, Category 3 or higher, has increased in recent decades.

The new study adds a direct line of evidence that tropical cyclones are getting stronger. Ocean measurements suggest that tropical cyclones are likely to intensify at a rate of about 1.8 meters per second every decade. The study suggests that this strengthening trend holds true for storms around the world.

The study has one major limitation: The findings are only reliable when it comes to weak tropical cyclones, such as Category 1 tropical storms and hurricanes. That’s because there simply hasn’t been enough data for stronger storms, which means that there is not enough evidence yet to say for sure.

But in a commentary on the new research, also published Wednesday in Nature, atmospheric scientist Robert Korty says he suspects the findings are probably true for stronger storms as well. For one thing, he points out, the measures included in this study are simply snapshots in time. Some of these storms may have been weak when they passed over ocean sensors, but would later intensify into larger storms.