16 2 Climate Science – “Our climate is our future” Climate science – regional and local Dr. Cho Ming Cheng, Director of HKO, provided a summary of the significant regional-local climate science based on the latest observations and assessments of IPCC AR6, amongst other data: • The proportion and intensity of most intense tropical cyclones and the precipitation rates are increasing and are projected to increase due to climate change. Tropical cyclone induced storm surge, precipitation rate and wind waves will increase. They will have impacts on the GBA and Hong Kong. • 2022 was a year with heat extremes: 52 hot nights, 52 very hot days, and 15 days with temperature of 35°C or higher. Their respective numbers over 30-year periods have increased 42 times, 9 times and 13 times (25.0 / 18.9 / 0.9 (1992-2021) vs 0.6 / 2.2 / 0.07 (1885-1914)). • Under the intermediate GHG emissions scenario (SSP24.5), the climate projections for Hong Kong by the end of the century are: - Annual mean temperature will increase by 2°C relative to 1995-2014 average;1 - Annual number of hot nights and very hot days will increase to 117 and 95 respectively; and - Annual maximum daily rainfall will increase by 16%. • Under the very high GHG emissions scenario (SSP5-8.5), the climate projections for Hong Kong by the end of the century are: - Annual mean temperature will increase by 3.6°C relative to the1995-2014 average;2 - Annual number of hot nights and very hot days will increase to 167 and 152 respectively; - Annual maximum daily rainfall will increase by 29%. • Sea level rise (SLR) in Hong Kong - Sea level will continue to rise for centuries to millennia even under large net negative carbon dioxide emissions; - Sea level will increase by 0.56 m (likely range: 0.37 – 0.82 m) and 0.78 m (likely range: 0.57 – 1.08 m) by the end of the century under the intermediate and very high GHG emissions scenarios respectively, relative to the 1995-2014 average. These increases will become 0.94 m (likely range: 0.58 – 1.41 m) and 1.36 m (likely range: 0.92 – 1.99 m) respectively in 2150;3 - For the low confidence scenarios considered by IPCC, which indicate the potential impact of deeply uncertain ice sheet processes, sea level will increase by 0.57 m and 0.91 m under the intermediate and very high GHG emissions scenarios by the end of the century. These increases will become 1.0 m and 2.06 m respectively in 2150.4 Cho Ming Cheng, HKO
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