Analysing the risk of climate change using an irrigation demand model

Climate Research

Roger N. Jones¹ 

关键词: Climate change;    Impact assessment;    Risk analysis;    Irrigation;   

DOI  :  10.3354/cr014089

来源: Inter-Research Science Publishing

【 摘 要 】

ABSTRACT: Due to the high degree of uncertainty accompanying projections of greenhouse-induced climate change, specific impacts cannot be predicted with any accuracy. At best, a range of projected climate change bounded by its high and low extremes can beused to produce a range of impacts, results that are often too broad to be of practical use in planning for adaptation and mitigation. However, by addressing outcomes in the initial stages of an impact assessment through the construction of user-definedthresholds, it is possible to identify outcomes that should either be avoided, in the case of a negative impact, or aimed for, in the case of a positive impact. By quantifying these thresholds as functions of key climatic variables, and creatingprojections for these variables that take account of a comprehensive range of quantifiable uncertainties, the risk of threshold exceedance can be analysed. This information can then be used in a risk assessment to identify windows for adaptation,describing the timing and degree of adaptation needed to prevent Œdangerous¹ climate change occurring for a particular activity. This procedure is illustrated through the use of an irrigation demand model for perennial pasture, based on data collectedfrom a farm in northern Victoria, Australia. Seasonal water-use is used to estimate an annual farm cap of 12 Ml ha^-1 based on the annual water right. The exceedance of this farm cap in 50% of years is taken to represent a critical thresholdbeyond which the farmer cannot adapt. The method of risk analysis utilises projected ranges of regional rainfall and temperature change, combined with a sensitivity analysis, to construct risk response surfaces. Monte Carlo sampling is used to scale 100yr of weather-generated data to calculate the probability of the annual farm cap being exceeded across ranges of temperature and rainfall change projected at 10 yr intervals from 2000 to 2100. Based on the model projections of changing water demand, somedegree of adaptation is indicated by 2030, although the theoretical critical threshold is not approached until 2050. This procedure represents a considerable advance in Œbottom up¹ studies where the impact on a specific activity is being addressed. Itprovides a basis for the planning of adaptation measures and can potentially contribute to the assessment of dangerous climate change as required by the UN Framework Convention for Climate Change.

【 授权许可】

Unknown