Scientists are working to understand whether there is a link between climate change and the number and strength of hurricanes and tropical cyclones.

INTRODUCTION
Tropical cyclones are given different names in different parts of the world (e.g. hurricane in the Atlantic, typhoon in the Pacific).

They are among the most devastating of natural disasters, and can cause immense loss of live and damage to infrastructure – as shown in recent years by Hurricane Katrina in the United States and Cyclone Nargis in Myanmar.

These storms develop only under particular conditions of atmospheric pressure and ocean temperature and there is an intense scientific debate about whether climate change is increasing the threat they pose.

The Intergovernmental Panel on Climate Change noted in its most recent report (2007) that there has been an increase in the strength (but not the number) of hurricanes in the North Atlantic since 1970. It said this increase was correlated with an increase in sea surface temperatures.

For other regions, the IPCC said the scientific data was not adequate to draw strong conclusions.

Overall, it concluded that there was a more than 50 percent likelihood that human activities were contributing to an increase in the intensity of hurricanes.

More recent scientific studies have, however, produced some contradictory evidence. This has led some non-scientists to claim that the IPCC has exaggerated the threat.

The most recent major scientific study of the relationships between these storms and rising global temperatures attempted to draw a more comprehensive conclusion than the IPCC.

It concluded that studies consistently indicate that rising temperature caused by emissions of greenhouse gases “will cause the globally averaged intensity of tropical cyclones to shift towards stronger storms”.

But it predicted that the number of tropical cyclones would fall, meaning that overall there would be fewer but more intense tropical cyclones as global temperatures rise.

Regardless of the exact effect of rising global temperatures on these big storms, coastal areas are likely to become more vulnerable to them because of rising sea levels.

SOLUTIONS
There is some evidence that coastal mangrove forests can absorb some of the destructive energy of major storms and protect the communities that live behind the forests.

Vast areas of mangroves have been felled in recent decades to make way for coastal developments and shrimp farms, leaving these areas more prone to damage.

Countries such as Indonesia and Vietnam have begun replanting mangrove forests to create a protective coastal buffer.

Other ways for countries and communities to reduce the threat from major storms include early warning systems and well-organised plans for evacuating coastal areas and ensuring the food, medicines and other supplies can be quickly delivered to affected areas.

REPORTING TIPS
The US Society of Environmental Journalists has a toolkit on hurricanes and tropical storms. It includes a wide range of sources of information and interviewees, most but not all of which are US-focused.

The US National Oceanic and Atmospheric Administration has a useful set of answers to freqently asked questions about hurricanes and cyclones.

Its National Hurricane Center, together with the Central Pacific Hurricane Center and the Joint Typhoon Warning Center provide accurate and up-to-date information about all tropical storms that could develop into full cyclones or hurricanes.

CASE STUDY – Bangladesh
In 1991, a major tropical cyclone struck the coast of Bangladesh and caused killed nearly 150,000. In November 2007 the same area was hit by a similarly strong storm called Cyclone Sidr.

This time though Bangladesh was much better prepared. Village committees had been set up to organise disaster preparedness at the community level and ‘cyclone preparedness’ volunteers had been trained in what to do in case of an imminent threat.

Before the cyclone arrived aid agencies and Bangladeshi officials arranged for food, blankets and water purification supplies to be sent to the areas in anticipation of a major emergency.

An early warning system put out an alert and trained volunteers helpe hundreds of thousands of people to evacuate their homes and move inland to higher ground.

The event was still a tragedy – with more than 3,500 lives lost, farmland and crops devasted, and massive damages to houses and other infrastructure – but the disaster plans and response prevented tens of thousands more deaths.

LINKS TO OTHER TOOLKIT PAGES
Climate Change
Reporting on Disasters

FURTHER READING
UK Met Office – tropical cyclones