2.4.13 (HL)—Global warming and cyclones

In the syllabus model, rising ocean temperatures from global warming increase the intensity and frequency of hurricanes and typhoons because warmer water and air provide more energy to developing storms.

Warmer surface water increases evaporation. Moist air rises and condenses, releasing latent heat; this can lower central pressure, strengthen inflow and winds, and supply more moisture for heavy rainfall. A larger area or longer season of suitably warm water can also create more opportunities for storms to develop.

Evidence should compare consistent records across a stated region and time period, separating storm counts from measures of intensity such as sustained wind speed or rainfall.

The causal chain is warmer ocean and air → greater evaporation and energy transfer → stronger storm development, with evidence assessed separately for frequency and intensity.

Intensity and frequency are different measures. One severe storm or one active season is not enough to establish a long-term trend in either measure.