Table 2.1: Main features of New Zealand climate change projections for 2030s and 2080s
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| Climate variable | Direction of change | Magnitude of change | Spatial and seasonal variation |
|---|---|---|---|
| Mean temperature | Increase (VH) | Mid-scenario 0.5-0.7°C by 2030s, 1.5-2.0°C by 2080s (M) | Strongest warming in winter, tendency for slightly more warming in E and N |
| Daily temperature extremes (frosts, hot days) | Fewer cold temperatures and frosts (VH), more high temperature episodes (VH) | Whole frequency distribution moves right (see 2.2.3) | See 2.2.3 |
| Mean rainfall | Varies around country. By 2080s Taranaki, Manawatu-Wanganui, West Coast, Otago and Southland show increases; Hawke's Bay Gisborne, eastern Canterbury, eastern Marlborough show decreases (M) | Substantial variation around the country (see 2.2.2) | Tendency to increase in south and west, decrease in N and E. Largest projected seasonal decreases in spring in N and E of North Island |
| Extreme rainfall | Heavier and/or more frequent extreme rainfalls, especially where mean rainfall increase predicted (M) | No change through to halving of heavy rainfall return period by 2030s; no change through to fourfold reduction in return period by 2080s (L) [See note 2] | Increases in heavy rainfall most likely in areas where mean rainfall is projected to increase |
| Snow | Snow cover decrease, snowline rise, shortened duration of seasonal snow lying (all M) | ||
| Glaciers | Continuing long-term reduction in ice volume and glacier length (M) | Reductions delayed for glaciers exposed to increasing westerlies | |
| Wind (average) | Increase in the mean westerly windflow across New Zealand (M) | By 2080s, could be from slight increase up to doubling of mean annual westerly flow (L) | |
| Strong winds | Increase in severe wind risk possible (L) | Little change up to double the frequency of winds above 30m/s by 2080s (L) | |
| Storms | More storminess possible, but little information available for New Zealand (L) | ||
| Sea level | Increase (VH) | 9-88 cm rise (New Zealand average) between 1990 and 2100 (VH) | See Coastal Guidance Manual |
| Waves | Increased frequency of heavy swells in regions exposed to prevailing westerlies (M) | See Coastal Guidance Manual | |
| Storm surge | See Coastal Guidance Manual | ||
| Ocean currents | Various changes plausible, but little research or modelling yet done | See 2.2.9 |
Note 1: Further guidance on values suggested for preliminary scenario analyses of potential climate change effects is provided in Table 5.1.
Note 2. Changes in the return period of heavy rainfall events may vary between different parts of the country, and will also depend on the rainfall duration being considered. See Section 2.2.4 for further discussion.
