Newsletter Issue 60 (October 2025)

The Weather of September 2025 – A stormy and hot September

September 2025 was marked by the successive strikes of tropical cyclones Tapah, Mitag and Ragasa. The ferocious strike of Super Typhoon Ragasa necessitated the issuance of the Hurricane Signal No. 10 on 24 September once again after Typhoon Wipha, tying the record of issuing the No. 10 Signal twice in the same year since 1964. Despite the succession of tropical cyclones affecting Hong Kong, September 2025 was hotter than usual in Hong Kong.

CO2 levels increase by record amount to new highs in 2024

Carbon dioxide (CO2) levels in the atmosphere soared by a record amount to new highs in 2024, committing the planet to more long-term temperature increase. The WMO Greenhouse Gas Bulletin said continued emissions of CO2 from human activities and an upsurge from wildfires were responsible, as well as reduced CO2 absorption by “sinks” such as land ecosystems and the ocean – in what threatens to be a vicious climate cycle.

Future sea-level rise is certain, but the amount and speed are not

Despite recent advances in ice-sheet modelling, deep uncertainty remains about the possible impact of accelerating ice-mass loss from the Antarctic Ice Sheets on the high-range of sea-level projections, especially beyond the 21st century, due to limitations in understanding and representing physical processes at ice margins and their feedback in the climate system. This includes potential runaway processes such as “Marine Ice Cliff Instability”.

Forecasting the future: the role of AI in transforming weather prediction and policy

AI is redefining the boundaries of what is possible in weather and climate prediction. From nowcasting to seasonal forecasting, its ability to deliver faster, more accurate and more accessible insights is already reshaping operational practices. Yet, its transformative potential will only be fully realized through thoughtful integration, robust evaluation and inclusive governance.

Global Seasonal Climate Update for NDJ 2025-2026

For November–December–January (NDJ) 2025/26, SST anomalies in the Niño 3.4 and Niño 3 regions are forecast to decline, with the potential transition to a weak La Niña. However, continued above-average SSTs in the western Pacific are expected to sustain a strong east–west SST gradient, reinforcing La Niña-like conditions across the equatorial Pacific. The Indian Ocean Dipole index is projected to remain in its negative phase, supported by persistent warmth in the eastern Indian Ocean.

Strengthen early warnings and climate action, UN Secretary-General tells WMO Congress

No country is safe from the devastating impacts of extreme weather, United Nations Secretary-General António Guterres told the WMO on 22 October, calling for a rapid expansion of early warning systems to protect lives and economies. The UN SG told the interactive dialogue in a WMO conference chamber: “Without your rigorous modelling and forecasting, we would not know what lies ahead — or how to prepare for it.”

Report warns that climate change, biodiversity loss, and pollution currently affect all ocean basins

The 9th edition of the Copernicus Ocean State Report highlights the deep and widespread links between ongoing ocean change and changes in marine ecosystems, human society, and the economy. The global ocean is affected by record-breaking temperatures, accelerating sea level rise, and continued acidification, with no part of the ocean untouched by what the UN has termed the triple planetary crisis of climate change, biodiversity loss, and pollution.

國新辦新聞發佈會介紹“十四五”時期氣象高品質發展成就

10月11日，國務院新聞辦公室在京舉行“高品質完成‘十四五’規劃”系列主題新聞發佈會。中國氣象局黨組書記、局長陳振林指出，“十四五”時期，氣象部門深入貫徹習近平總書記重要指示精神，認真落實國務院《氣象高品質發展綱要（2022—2035年）》，努力構建科技領先、監測精密、預報精准、服務精細、人民滿意的現代氣象體系，“十四五”氣象發展規劃各項任務圓滿完成，2024年全國氣象高品質發展指數較2020年提升18.35%。

從遙遠海洋的壯美現象，到服務現實的科學探索——中國學者持續深化兩類ENSO領域研究

(Deepseek 撮要) 任宏利及來自中國氣象科學研究院、國家氣候中心、南京資訊工程大學等多位學者組成的ENSO研究團隊針對「東部型」與「中部型」兩類ENSO展開系統研究，突破傳統認知：首創專用指標與國際標準，揭示兩者在動力機制與時間尺度上的差異，並開發首個動力—統計預測系統。成果深化了對ENSO多樣性的科學理解，顯著提升中國的氣候預測能力與國際影響力，為應對極端天氣與氣候變化提供重要支撑。

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