A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds and a spiral arrangement of thunderstorms that produce heavy rain or squalls.

The majority of these systems form each year in one of seven tropical cyclone basins, which are monitored by a variety of meteorological services and warning centres.

The factors that determine tropical cyclone activity are relatively well understood: warmer sea levels are favourable to tropical cyclones, as well as an unstable and moist mid-troposphere, while vertical wind shear suppresses them. All of these factors will change under climate change, but is not always clear which factor dominates.

How can climate change affect tropical cyclones?

Climate change may affect tropical cyclones in a variety of ways: an intensification of rainfall and wind speed, a decrease in overall frequency, an increase in frequency of very intense storms and a poleward extension of where the cyclones reach maximum intensity are among the possible consequences of human-induced climate change.

The proportion of severe Tropical Cyclones has increased, possibly due to anthropogenic climate change. This proportion of intense Tropical Cyclones is projected to increase further, bringing a greater proportion of storms having more damaging wind speeds, higher storm surges, and more extreme rainfall rates.
Warming of the surface ocean from anthropogenic (human-induced) climate change is likely fueling more powerful Tropical Cyclones.

The destructive power of individual Tropical Cyclones through flooding is amplified by rising sea level, which very likely has a substantial contribution at the global scale from anthropogenic climate change.

In addition, Tropical Cyclones precipitation rates are projected to increase due to enhanced atmospheric moisture associated with anthropogenic global warming.

Additional changes such as the poleward migration of the latitude of maximum intensity, increasing rates of rapid intensification, and a slowing of the forward motion of Tropical Cyclones have been observed in places, and these may be climate change signals emerging from natural variability.

While there are challenges in attributing these past observed changes to anthropogenic forcing, models project that with global warming, some regions will experience increases in rapid intensification, slowing of the forward motion of TCs, or a poleward migration of the latitude of maximum intensity, in coming decades.