01 Ocean temperatures and cyclone intensities worldwide

A scientific study performed by the Scripps Institute (Barnett et al. (2005) Science) compares recordings of ocean temperatures and respective computer simulations and shows that anthropogenic climate change is having a strong impact on increases in recorded temperatures of the upper ocean layers since 1960 (cf. Tourre/White GRL (2005)).

Other scientific studies by US researchers (Emanuel (2005), Nature; Webster et al. (2005), Science) have shown the following. There is evidence of a warmer trend during the summer season in all tropical oceans amounting to an average of 0.5°C since 1970. The intensity of tropical cyclones, characterised by the parameters of maximum wind speed and cumulative length of time with high wind speeds, increases in correlation with sea surface temperature (Fig. 1). As a consequence of this correlation, the global number of severe tropical cyclones (4-5 on the Saffir-Simpson Scale) has increased in relation to the annual total for all ocean basins. There has been a steep increase in absolute terms too, from about 8 per year at the beginning of the 1970s to 18 per year, i.e. more than double — in the period 2000-2004. At the same time, the proportion of weaker cyclones (Category 1) has decreased, while there is no recognisable trend as far as the moderate types (Categories 2-3) are concerned (Fig. 2).