Short answers, pulled from the story.
Rising ocean temperatures due to human-induced climate change provide more convective available potential energy, which fuels stronger storms. Satellite data since the early 1970s shows a clear link between rising sea surface temperatures and increased storm intensity.
The number of very severe cyclones rose by 150% between 1982 and 2019. Total duration of cyclones in the Arabian Sea increased by 80%, while very severe cyclones grew in duration by 260%.
Observations indicate little change in worldwide total frequency, yet North Atlantic and central Pacific regions saw increases. A 2020 paper comparing nine high-resolution models found robust decreases in the Southern Indian Ocean and broader Southern Hemisphere.
Warmer air holds approximately 7% more water vapor for every degree Celsius of warming, leading to heavier rainfall rates during storms. The World Meteorological Organization stated in 2017 that Hurricane Harvey's rainfall quantity very likely increased due to climate change.
Lower-resolution models cannot represent convection directly, relying instead on parametrizations that approximate smaller-scale processes. Higher-resolution global and regional models are computer-intensive, making it difficult to simulate enough storms for robust statistical analysis.