The climate is warming, which has and will continue to result in means a number of changes to temperature, rainfall, drought, snow, wind and sea-level in New Zealand.
Changes that have already occurred include:
Mean annual temperature for New Zealand, calculated from NIWA's 'seven-station' series. This series uses climate data from seven geographically representative locations. The data are adjusted to take account of factors such as different measurement sites. The blue and red bars show the difference from the 1971-2000 average. The black dotted line is the linear trend over 1910 to 2010 (0.96°C/100 years).
Fewer frosts over most of the country: Canterbury and Marlborough, for example, experienced about 20 fewer frosts per year in the early 2000s than in the early 1970s.
Retreat of major South Island glaciers: the volume of ice in the Southern Alps reduced by almost 11% in the past 30 years. Twelve of the largest glaciers are unlikely to return to their earlier lengths without extraordinary cooling of the climate.
In December 2011, an unprecedented rainfall event occurred in Golden Bay and Nelson. The township of Takaka recorded 674 mm of rainfall in 48 hours – the largest 48 hour accumulation of rainfall ever recorded in an urban area in New Zealand. Analysis of this event indicates that the total moisture available for precipitation may have been 2-7% higher as a result of the emission of anthropogenic greenhouse gases.
Sea-levels have risen 0.16m during the 20th century averaged over the four main ports.
There is now strong evidence that the cause of the observed warming cannot simply be natural variation.
In its Fifth Assessment Report (AR5), the Intergovernmental Panel on Climate Change (IPCC) states with 95% confidence that humans are the principal cause of current global warming. This is known as anthropogenic global warming (AGW), and is primarily caused by the increase in greenhouse gas concentrations in the atmosphere resulting from human activity.