Climate Change in the Pacific 2022: Historical and Recent Variability, Extremes and Change

This report presents key scientific findings from the second phase of the Climate and Oceans Support Program in the Pacific (COSPPac, July 2018–June 2023), Seasonal Prediction and the Pacific Sea Level and Geodetic Monitoring (PSLGM) Projects. The report contributes to COSPPac’s aim for Pacific Island national meteorological services to understand and use climate, ocean and sea level data and information to develop and disseminate useful products and services to Pacific Island governments and communities, building resilience against the impact of climate change, climate variability and disasters.

The report also provides an update of scientific understanding of large-scale climate processes, variability and extremes in the western tropical Pacific first presented in the Pacific Climate Change Science Program (PCCSP) Climate Change in the Pacific: Scientific Assessment and New Research, Volume 2, Country Reports (2011) and the Pacific–Australia Climate Change Science and Adaptation Planning (PACCSAP) Program Climate Variability, Extremes and Change in the Western Tropical Pacific: New Science and Updated Country Reports (2014). The work is designed to complement the recently released ‘NextGen’ Projections for the Western Tropical Pacific country reports and provide finer-scale partner country historical climate change information not presented in the Intergovernmental Panel on Climate Change (IPCC)’s Sixth Assessment Report (AR6), Climate Change 2021: The Physical Science Basis, and World Meteorological Organization (WMO) Regional Association Five (RA-V) Pacific Regional Climate Centre (RCC) Network’s Pacific Climate Change Monitor (PCCM) Report (2022). Chapter 1 provides a general introduction to the content, structure and methods used for each country report in subsequent chapters.

Each subsequent country chapter has nine sections that provide: (1) a climate and ocean summary; (2) country description; (3) data availability; (4) rainfall seasonal cycle and observed trends; (5) air temperature seasonal cycle and observed trends; (6) tropical cyclone seasonal cycle and observed trends; (7) sea surface temperature (SST) seasonal cycle and observed trends; (8) sea level seasonal cycle and observed trends; and (9) wave climate, seasonal cycle, trends, and extreme value analysis. Trend lengths vary depending on data availability and quality. It is anticipated that this report, associated products and capacity-building activities will provide decision-makers and other stakeholders in the partner countries, as well as the wider scientific community, with up-to-date, robust climate change science information for the region and the individual countries. While producing this report, the authors identified a decline in the quality and quantity of Pacific Island climate data and metadata beginning in the 1990s.

Few Pacific national meteorological services are documenting equipment maintenance/change, calibration, exposure and site changes. More than half of the countries represented in this report currently have less than two stations near-complete maximum and minimum temperature time series from the 1980s to 2020. In some cases, this represents a national network decline of greater than 80% in 30 years. Pacific Island governments and donors are requested to prioritise climate and ocean observations for the purposes of ongoing climate change monitoring in the Pacific.