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Geographic Area Covered 

The Wellington Region governed by the Greater Wellington Regional Council, including Kapiti, Porirua, and Wellington City, Hutt Valley and the Wairarapa. 

Summary of the Report 

This report, prepared by NIWA for the Greater Wellington Regional Council, provides a comprehensive assessment of climate change and variability in the Wellington Region through the 21st century. It draws on global and national climate projections, including IPCC AR5 scenarios and NIWA’s downscaled regional climate models, to evaluate expected changes in temperature, precipitation, drought, extreme weather events, and sea-level rise. The report also considers implications for biodiversity, agriculture, biosecurity, hydrology, wildfire risk, and coastal hazards. 
 
The Wellington Region is expected to experience significant warming, with annual mean temperatures projected to increase by 1.2°C under RCP4.5 and 2.7°C under RCP8.5 by 2090. Inland areas, particularly Wairarapa, will see more hot days and fewer frosts. Rainfall patterns will shift, with increases in the west and decreases in the east. Drought risk will rise, especially in Wairarapa, with potential evapotranspiration deficits increasing by over 160 mm/year under high emissions scenarios. 
 
Extreme rainfall events are projected to intensify, with the 99th percentile of daily precipitation increasing by up to 25% around Wellington City. Windy days and extreme wind speeds may also rise, particularly in southern parts of the region. Solar radiation and relative humidity will undergo minor changes, while snow days will decline significantly. 
 
Sea-level rise poses a major threat to coastal infrastructure and ecosystems. Projections range from 0.28 to 0.98 meters by 2100, with additional risks from land subsidence and storm surges. Coastal areas such as Petone, Seaview, and parts of Wellington City are particularly vulnerable. 
 
Climate change will impact biodiversity through habitat shifts, increased pest risks, and altered species interactions. Agriculture will face challenges from changing rainfall, increased drought, and shifting growing conditions. Hydrological changes will affect river flows, with potential reductions in low flows and increases in flood risks. Wildfire danger is expected to rise, and soil temperature changes may influence plant growth and nutrient cycling. 
 
The report emphasizes the need for adaptive planning and ongoing monitoring to manage climate risks. It highlights the importance of integrating climate projections into regional planning and infrastructure development to enhance resilience in the Wellington Region.