Lessons for Hong Kong in the way typhoon Haiyan wreaked destruction

In the aftermath of Super Typhoon Haiyan devastating large swathes of the Philippines, the news media have linked the storm's ferocity to climate change. So did Yeb Sano, lead negotiator for the Philippines at the United Nations climate talks that are currently under way in Poland. "What my country is going through as a result of this extreme climate event is madness. The climate crisis is madness," Sano said in an emotional speech three days after the storm hit.

Yet madness though the climate crisis may be, it is hard to link Haiyan to climate change. Indeed, it is not even straightforward determining whether it truly was the strongest storm ever to make landfall.

The latter claim is largely based on the US Navy's Joint Typhoon Warning Centre estimating that just before Haiyan made landfall, its maximum sustained winds were 314 km/h. The figure was derived from satellite observations, and is marginally higher than the previous record holder, Hurricane Camille, which came ashore in the southeastern US in 1969.

By another measure of strength - air pressure - Haiyan might rank as the 12th strongest tropical cyclone on record, according to Dr Jeff Masters, cofounder of the website Weather Underground. But it is, however, important to note that it was close to the theoretical upper limit for tropical cyclones.

Masters wrote that Haiyan was powered by unusually warm sub-surface waters east of the Philippines - which were four to five degrees Celsius above average last month. One factor in causing this warmth may have been relatively strong trade winds in recent years. But also, the anomalous warmth is consistent with climate change.

A paper submitted to Geophysical Research Letters this spring analysed the warming west Pacific waters. In the main development region for typhoons, the tropical heat potential had become 10 per cent higher than in the 1990s. This had made the region even more favourable for typhoon and super typhoon intensification.

Professor Johnny Chan Chung-leung, dean of the school of energy and environment at the City University of Hong Kong, has cautioned that warming Pacific Ocean temperatures need not necessarily result in more typhoons, as these also require stronger atmospheric circulations. Indeed, for 1960 to 2005 he found no increase in frequency of Pacific typhoons.