Pacific-Australia Climate Change Science and Adaptation Planning Program (PACCSAP)

2014 Climate extremes in the western tropical Pacific

Countries in the western tropical Pacific are particularly vulnerable to impacts from extremes in temperature, rainfall and sea-level rise, as well as tropical cyclones.

What are climate extremes? Sea level: Natural sea level changes due (a) Current temperature (b) Future temperature to tides, weather and climate variability are short-term weather Climate extremes can be quite large at any one time or longer-term climatic events that are Current Future compared to sea-level rise as a result of climate climate rare or uncommon in occurrence, and climate change alone. Global-average often excessively severe in impact. More hot sea level has risen 19 cm since 1901, weather Extreme events resulting from natural primarily due to thermal expansion of Cold Hot temperature temperature Less cold water as the oceans warm, and melting More variability in large-scale climate processes, extremes extremes weather record hot from season to season and year to year, of glaciers, ice caps and ice sheets on of occurence Frequency weather can cause massive loss and damage to land with increased run-off to the sea. infrastructure, industry and environmental Cold Moderate Hot Cold Moderate Hot What might happen assets, and can impact on the health, safety (a) Current temperature (b)(c) CurrentFuture temperature rainfall (d) Future rainfall and overall wellbeing of local communities. in the future? Current These large-scale processes include the Temperature: Scientists are very Current Future climate El Niño Southern Oscillation (ENSO), the confident that the intensity and frequency climate climate South Pacific Convergence Zone (SPCZ), of extreme heat will continue to increase Less light More hot rainfall the West Pacific Monsoon (WPM) and the for the rest of the 21st century. Events weather Intertropical Convergence Zone (ITCZ). that areCold considered a heat wave in theHot Less cold temperature temperature MoreHeavy More heavy Longer-term variability and climate change current climate are projected to weather Future extremes extremes recordrainfall hot rainfall Frequency of occurence Frequency compound these impacts, particularly become of occurence Frequency longer. weatherextremes climate in terms of increased vulnerability to Rainfall: Almost all Pacific island countries natural, climate-related disasters. Cold Moderate Hot Cold Moderate Hot are projected to get more rainfall and Light Moderate Heavy Light Moderate Heavy (c) Current rainfall (d) Future rainfall What has happened in the past? fewer droughts, with some showing Comparison of current and future extreme rainfall little change. Longer-term projections and temperature in the western tropical Pacific. Temperature: There has been a trend Current of extreme rainfall days differ for each climate toward more frequent hot days and warm Pacific island country, but scientists are nights, and fewer cool days and cool nights, Less light as average air temperatures have increased rainfall significantly over the last 50 years. Heavy More heavy Future Rainfall: Rainfall extremes are primarily rainfall rainfall Frequency of occurence Frequency climate influenced by year-to-year and decade-to- extremes decade variability associated with ENSO and the intensity/location of other major Light Moderate Heavy Light Moderate Heavy climate features such as the SPCZ, ITCZ and WPM. As an example, La Niña events in recent years have been associated with severe drought in and floods in Fiji. Tropical cyclones: On average, nine tropical cyclones occur in the western Pacific region between November and April each year, mostly between January and March. The greatest numbers of cyclones occur in the Vanuatu-New Caledonia region. The frequency and intensity of cyclones varies significantly High-energy, Pacific storm-driven extreme wave event (left) which impacted the islands of six Pacific nations from year to year, largely due to ENSO. including Takuu , Papua (right), December 2008. (Photo: Jeffrey Holdaway, On the Level Productions). confident that they will be more intense Tropical cyclones: Tropical cyclones Building resilience for a and more frequent over the entire region. are potentially life threatening to local more sustainable future Over the course of the 21st century, the communities and can cause a great Climate extremes are only some of many change is likely to be slightly greater in deal of loss and damage to industry, challenges that climate variability and some countries like Fiji and , and also infrastructure and natural resources. change present to local communities in countries in the west such as Palau, Papua This damage can incur massive social, the western tropical Pacific. Adaptation New Guinea and the Solomon Islands. economic and environmental costs. is essential to enhance the resilience However, longer-term changes in ENSO Sea level: Coastal flooding and erosion of the most vulnerable communities in are still uncertain. For example, an increase from combined storm surges and high tides the face of potential climate impacts. in the frequency or intensity of El Niño in could become more frequent in the future. future could lead to an increase in drought The timely provision of reliable scientific This could directly impact on the health and in some countries, despite the overall understanding and evidence to inform wellbeing of coastal communities through increase in mean rainfall across the region. decision-making will enable more effective potential injury and loss of life, and loss and efficient adaptation planning: an Tropical cyclones: Scientists are confident and damage to coastal resources, industry essential requirement for securing that over the course of the 21st century and infrastructure. In the longer-term, these sustainable development in the region. tropical cyclones will become less frequent events could cause saltwater contamination in the Pacific region, but more intense. of freshwater aquifers, surface water storages and agricultural soils, and also Sea level: Extreme sea level events the loss of culturally significant sites. will happen more often as the effects of natural variability are compounded by long-term sea-level rise due to climate change. This includes coastal flooding that occurs in association with tropical cyclones and other high energy, low-pressure storms that generate extreme winds and oceanic swells. What are some of the impacts? Temperature: Very hot days and long hot spells lead to heat stress which in turn poses threats to the health and wellbeing of local communities. Extreme temperatures in association with dry periods contribute to drought conditions, posing a risk to water security for domestic, Damage caused by Tropical Cyclone Evan in Apia, , December 2012. industrial and agricultural purposes. (Photo: Meteorology Division, Samoa Ministry of Natural Resources & Environment) High temperatures also increase energy demand for domestic and industrial cooling, posing a risk for energy security. Rainfall: Flooding and erosion caused by extreme rainfall events can damage infrastructure, roads, agricultural land and human settlements. Flooding of rivers can combine with high sea levels from natural tidal fluctuations and/or storm surges to increase the impact of coastal inundation and erosion.

Storm-surge waves driven by Tropical Cyclone Cyril, overtopping Alofi wharf, Niue, February 2012.

Other fact sheets in • Sea-level rise in the • Climate variability and climate change • Large-scale climate features • Ocean acidification in the the series include: western tropical Pacific in the western tropical Pacific in the western tropical Pacific western tropical Pacific

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