Climate Change - There continues to be debate amongst the experts on the exact nature of climate change. The Ministry for the Environment is however publishing clear advice on the possible implications. The advice on their web-site was last up-dated in July 2014 as follows: Projections of climate change depend on future greenhouse gas emissions which are uncertain. Also, global climate models used to predict future climate vary in their sensitivity to these emissions. The combination of these factors means that projections of future climate are usually expressed as a range of likely values. This information is mostly from 'middle-of-the-range' climate change projections. Temperature - Temperatures are likely to be around 0.9˚C warmer by 2040 and 2.0˚C warmer by 2090, compared to 1990. By the end of the century, Marlborough is projected to have about 10–40 extra days per year where maximum temperatures exceed 25˚C. The number of frosts could decrease by around 20–45 per year, with even greater reductions in frosts possible further inland. Rainfall - Rainfall will vary locally within the region. While annual rainfall is likely to increase in the inland high country, eastern Marlborough and the Kaikoura Coast are likely to become drier. In Blenheim, there is likely to be little change in average annual rainfall by 2090. Seasonal projections show summer and autumn rainfall both increasing by 5 per cent in Blenheim, with very little change in winter and spring rainfall by 2090. Very heavy rainfall events are likely to become more frequent. Sea-level rise - New Zealand tide records show an average rise in relative mean sea level of 1.7 mm per year over the 20th century. Sea levels are expected to continue to rise into the future. The Ministry for the Environment recommends planning for future sea-level rise of at least 0.5 m, along with consideration of the consequences of a mean sea-level rise of at least 0.8 m (relative to the 1980–1999 average) by the 2090s. Storms - The number of storms crossing the Tasman Sea is expected to increase in summer and decrease in winter, by the end of the century. The intensity of these storms is likely to decrease in both summer and winter. Wind - The frequency of extreme winds over this century is likely to increase by between 2 and 5 per cent in almost all regions of New Zealand in winter, and decrease by a similar amount in summer. There may be more north-easterly events over the top of the South Island and less frequent westerly winds. As can be seen from the earlier discussion the demand for water throughout Marlborough is heavily influenced by the weather. The expectation that summer rainfall is likely to increase in Blenheim will help to supress the demand for irrigation water. However as the average is not expected to change, there may be a shift in the peak demand to the spring that is likely to be correspondingly drier. Climate change is only one of the variables to take into account in the design and operation of the infrastructure. However it is critically important and is being incorporated into all current designs National and International Comparison By both national and international standards water consumption in Marlborough appears to be very high. As discussed earlier the warm dry summers experienced in Marlborough, particularly in the south are conducive to high water consumption. A comparison between New Zealand and other developed nations is shown in Figure 12. It is derived from a study into water sustainability by researchers in Beijing. Whilst it is consistent with other available international data the basis of calculation in the study is not known and cannot be directly compared with the local statistics but a general relativity can be inferred. Page 45