Climate change poses a major hazard to Pacific Island countries and East Timor. Recognising this vulnerability, the Australian government has supported a program of work called the Pacific-Australia Climate Change Science and Adaptation Planning program which seeks to build the scientific understanding of Pacific climate and associated climate change. This program is being delivered in partnership between CSIRO, the Bureau of Meteorology, Australian Universities and Geoscience Australia working closely with National Meteorological Services and other agencies in the Pacific.

We will describe the development of homogenous rainfall and temperature datasets for the western Pacific, and associated analysis of these data. Mean warming trends are spatially homogenous and dominate across the region with mean warming 0.18°C per decade over the last 50 years. Trends in total rainfall are spatially heterogeneous and largely non-significant over the same period. Only in the subtropics is there a drying trend, consistent with broader trends seen in parts of southern and eastern Australia. The 50-year rainfall trend appears to have reversed markedly over the past three decades consistent with a southwestward shift of the South Pacific Convergence Zone and the ITCZ/West Pacific Monsoon expanding northwards west of 140°E since the late 1990s.

We have also analysed a suite of indices defining a range of climate extremes which have been developed by the WMO Expert Team on Climate Change Detection and Indices. In this way the current research fits in to an existing global framework, building on an international effort to improve understanding of extreme climate variability and trends. Homogeneous warming exists in station-level temperature extremes for over 30 stations. In some cases the frequency of warm nights/days has increased more than four fold over the last 50 years, which in contrast the number of cool nights/day has decreased dramatically, with these becoming rare in the most recent period.