It is therefore not the frequency but the intensity of cyclones that is worsening, with two combined phenomena: warming of the oceans - which creates more water vapour and therefore energizes cyclones as they form above the sea - and rising sea levels, which IPCC experts put at between 26 and 82 cm by the year 2100. The climate change now occurring is taking us towards ever more intense meteorological events. This was also the conclusion of two studies published in 2005, the first in Nature3, which showed that the total energy dissipated by hurricanes in the northern Atlantic and western Pacific had increased by 70 per cent over 30 years, and the second, in Science,4 which confirmed that the number of category four or five hurricanes increased by 57 per cent between 1970 and 2004.