Why are there so many hurricanes?

Another week, another hurricane. Is this year unprecedented?

Another week, another hurricane. Is this year unprecedented?

Just about. The only time on record that anything like this happened before was in 1947, when two hurricanes and one tropical storm hit Florida within five weeks. In the 38 years since 1966 only one hurricane - Andrew in 1992 - hit the state before last month.

Anything else?

Yes, since you ask. August saw a record number of tropical storms so big that they were given names. Eight of them. And the US suffered 173 tornadoes last month, easily outstripping the previous record of 128.

Is this the end of it?

Unlikely. Friday marked the half-way point in the hurricane season. Prof William Gray of Colorado State University, one of the world's top hurricane forecasters, predicts at least one more this month. But he foresees a quiet October, partly because another disturbance - El Niño - is gathering pace in the Pacific, and this tends to suppress hurricanes in the Atlantic.

Haven't there been rather a lot of hurricanes over the last few years?

Yes, indeed. The years since 1995 have been the worst on record. And experts predict it will go on for decades more.

What's going on?

A combination of factors must combine to make a hurricane. These include thunderstorms, distance from the Equator, and particular wind conditions. But one of the most vital is warm seawater: the Atlantic is very warm this year.

So it's all down to global warming?

Hard to say. There are natural cycles in the temperature of the oceans. But most scientists agree that hurricanes will get stronger as the world warms up. Whether they will be more frequent is a much more open question.