In recent years, the East Asian (EA) region experienced escalated cost of damages associated with tropical cyclones (TC) during the mature boreal autumn (i.e., September−October). Questions arise whether such increased TC-associated cost of damages are indicative of increasing activity of TCs in EA, particularly during the mature boreal autumn. Here we show evidence of significantly increasing activity of TCs in EA from 1981 to 2019 that is mainly accompanied by an abrupt regime shift in TC passage frequency since 1998. Such trend and shift are robustly linked to the shift of the Pacific Decadal Oscillation (PDO) to its negative phase in the mid-1990s. Characterized by warm sea surface temperature anomalies in the subtropical North Pacific, a negative PDO phase is related to the weakening of the East Asian subtropical jetstream and the westward displacement of the WNP subtropical high, which initiates a favorable steering environment for increased TC passages into the EA region. Contrasting environmental patterns are associated in a positive PDO phase. Considering the prominence of EA in the global economy, our paper contributes additional insights on long-term tropical cyclone risk reduction and management in the region.

To imply the gravity of their impact on Christmas celebration, the term Christmas typhoon recently became more popular to refer to tropical cyclones (TC) in the Western North Pacific (WNP) during its less active season. The past 9 years from 2012 to 2020 saw more than 70% (210%) increases in Christmas typhoon occurrences in the WNP (Philippines). Furthermore, Mindanao Island, which is located in southern Philippines, has experienced an unprecedented 480% increase in TC passage in the same period. Here we show that the detected recent increase in Christmas typhoons are mainly associated with the shift of the Pacific Decadal Oscillation to its positive phase in early 2010s, which led to favorable changes in the large-scale environment for TC development such as higher relative vorticity, anomalous low-level westerlies, warmer sea surface temperatures in the central Pacific, and extended WNP subtropical high. We also found that the poleward shift of the Intertropical Convergence Zone and possibly, the recent recovery of the Siberian High contributed to such increased occurrences. As opposed to the more active TC season, there is a wide research gap during the less active season. We aim to fill in this knowledge gap to gain better insights on TC risk reduction.

To meet the growing demand for climate change information to guide national and local adaptation decision-making in the Philippines, the climate science and services community is producing an increasing volume of future climate data using a range of modelling approaches. However, there is a significant methodological challenge in how to best compare and combine information produced using different models and methods. In this paper, we present the landscape of climate model data available in the Philippines and show how multimodel, multi-method climate projections are being used and communicated to inform climate Climatic Change (2018) change policy and planning, focusing on the agriculture sector. We highlight the importance of examining and communicating methodological strengths and weaknesses as well as understanding the needs and capabilities of different user communities. We discuss the assessment of projections from different methods, including global and regional downscaled simulations, and discuss ways to summarise and communicate this information to stakeholders using coproduction approaches. The paper concludes with perspectives on how to best use an Bensemble of opportunity^to construct defensible, plausible and usable climate projections.