An assessment of the impacts of climate change in the Waikato region: Applying CMIP5 data

Report: TR 2015/26

Author: Drs Meng Wang, Yinpeng Li and Chonghua Yin

Climate change is projected to alter long-term average climatic conditions and climatic variability in New Zealand. The best estimates are for a temperature increase of 0.2–2.0°C by 2040 and 0.7–5.1°C by 2090, with marked seasonal changes in rainfall and extreme events (Ministry for the Environment, 2008 (based on CMIP3 data).

This report provides a broad technical assessment of the physical effects of climate change in the Waikato region. Projections cover short (2030), medium (2070) and long-term (2100) timeframes. Ensembles (or parallel scenarios) of up to 40 CMIP5 Global Climate Models (GCMs) were used to generate the future scenarios. Eight climatic indices were used to represent the major climate change-induced effects, including mean temperature, mean precipitation, extreme precipitation change, peak streamflow change, Potential Evapotranspiration Deficit (PED), Temperature-Humidity Index (THI), Growing Degree Days (GDD), and extreme wind.