The increase of hurricane activity in recent years is often linked to rising sea temperatures and thus, indirectly, to global warming. But a recent study makes this link less direct than it once seemed.

The study, published in the journal Nature, examines hurricane activity over the past 5,000 years. It includes evidence for increased hurricane activity at times in the past when the seas were cooler than they are now.

There is nothing in the study that contradicts a link between global warming and increasing hurricanes. But the evidence found suggests there are be other factors involved as well, probably including El Niño and the West African monsoon.

For the present day this means a change in these other factors could either increase hurricane activity even further, or calm it down in spite of the warm seas.

An abstract of the study is available from Nature here and an article about it is available from the International Herald Tribune here