JOHANNESBURG, 21 August 2008 (IRIN) - One symptom of climate change is more severe tropical cyclones, hurricanes and typhoons, featuring in the headlines more often.

What is a tropical cyclone?

A tropical cyclone is a generic term for a small, intensely developed low-pressure cell that forms over warm oceans. Its diameter can range from 200km to 2,000km, with a warm centre and strong cyclonic winds, moving clockwise in the southern hemisphere.

What is a tropical depression?

Tropical cyclones with a maximum wind speed of less than 60km per hour are called tropical depressions.

What is a tropical storm?

When a tropical cyclone reaches speeds ranging from 60km per hour to 110km per hour it is called a tropical storm and given a name.

What is the difference between a hurricane, a typhoon and a tropical cyclone?

"Hurricane" and "typhoon" are regionally specific names for a strong tropical cyclone.

When wind speeds reach more than 119km per hour, a tropical cyclone is called:

- a "hurricane" over the North Atlantic Ocean, the Northeast Pacific Ocean east of the International Date Line or the South Pacific Ocean east of 160°E

- a "typhoon" over the Northwest Pacific Ocean, west of the International Date Line

- "severe tropical cyclone" over the Southwest Pacific Ocean west of 160°E or Southeast Indian Ocean east of 90°E

- "severe cyclonic storm" over the north Indian Ocean

- "tropical cyclone" over the southwest Indian Ocean

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Sources:

The Atlantic Oceanographic and Meteorological Laboratory The South African Weather Service

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