Cyclone information saves lives, but studies incomplete

Studies show cyclones are fuelled by both evaporation from the ocean and the wind speed difference between the upper and lower atmosphere. Photo/File

Wanganui is lucky. Extreme weather events are rare. However, the folk in Florida are not so fortunate.

During the hurricane season, the meteorologists issue large maps of Florida, the Gulf of Mexico and the Caribbean, with latitude and longitude marked. These are distributed to all postal addresses. Spare copies are left in most businesses, especially the supermarkets. The supermarkets themselves print these hurricane-tracking maps on their tough paper grocery bags.

Why do they do this? Because every year there are storms and hurricanes that travel toward Florida at 20 to 30 knots, pursuing a meandering path with occasional abrupt changes in direction. The media issue regular updates, giving speed, coordinates and predictive movements of the threatening weather.

The good news is that, with this information available, there is usually a 24- to 48-hour warning and time to evacuate if you live on the coast, or batten down if you don't. Most of these storms are not too threatening or give your area a wide birth.

We lived there for 20 years and only suffered hurricane damage and flooding twice.

Climate change scientists wonder what the effect of global warming on storms will be. Theoretically, more heat in the system should mean more frequent and stronger storms, but even though there has been a large number of stronger Pacific cyclones this year, they cannot yet be linked to climate change. There are, as usual, a lot of other factors involved.

Recent studies show that cyclones are fuelled and affected by many things, especially evaporation from the ocean. The warmer the ocean, the more destructive the storm will be. However, it seems that the wind speed difference between the upper and lower atmosphere is also important. An increase in this difference would prevent the formation of hurricanes. This may apply more to the North Atlantic. The number of storms in the Pacific might not necessarily change. This is confusing.

Consequently, the IPCC concludes that although there is some evidence for more, and stronger, Atlantic hurricanes over the past 40 years, worldwide there is no trend in either the frequency or intensity of tropical storms. They add that it may take a long time for any trend to become apparent (IPCC, New Scientist).

Weather is tricky stuff, and research is bedevilled with contradictions. As usual, climate scientists get blamed for our ignorance, especially if they publicly admit that there are many uncertainties. In time, these will be understood. This is important. Extreme weather systems are immensely destructive and cause considerable loss of life and property.

This is partly because of an increasing world population living in low-lying areas subject to flooding. If scientists could understand more about how weather systems are fuelled and guided, they might find some way to change their course and intensity and reduce the human cost and property damage.

It is nice to be living 100 metres above sea level, and not 10 centimetres, as we were for 20 years in Florida before coming here.

Ian Sutherland is a retired pathologist with a lifelong interest in conservation.