Table 5.1: Values or sources of climate parameters suggested for use in scenario analysis
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| Climate factor | For screening assessment scenarios | For detailed study scenarios |
|---|---|---|
| Mean temperature | Mid-range 2030s and 2080s projections (central panel Figure 2.2; Figure 2.3; central values from Tables 2.2 and 2.3) | Low, mid and high scenarios from ranges given in Tables 2.2 and 2.3, or approach a science provider1 for regional numbers |
| Frost occurrence | For 2100, two top panels of Figure 2.8. For 2030s, 2080s use mid-range CLIMPACTS2 or move current seasonal frequency distribution of daily minimum temperature right by seasonal mean change3 | Use CLIMPACTS to develop low/medium/high scenario frost changes, and/or approach a science provider for regional numbers |
| Extreme high temperatures | For 2100 use lower two panels of Figure 2.8 | Use CLIMPACTS to develop low/medium/high scenario maximum temperatures and/or approach a science provider for location-specific weather generator results |
| Growing degree days (GDDs) | Use CLIMPACTS for a mid-range scenario | Use CLIMPACTS to develop low/medium/high scenario changes and/or approach a science provider for location-specific projections |
| Winter chilling | Approach a science provider for weather generator based location-specific projections | |
| Mean rainfall (annual, seasonal) | Use low, middle, high scenarios4 from Figures 2.5, A10, A11 for 2030s and 2080s | Use low, middle, high scenarios4 from Figures 2.5, A10, A11 for 2030s and 2080s |
| Heavy rainfall6 | Use factors from Table 5.2 with 5, 10, 50, 100 year ARI values from HIRDS5 or from local data analyses | Obtain assistance from a science provider with site-specific applications of the gamma function analysis outlined in Appendix 3, or obtain updated guidance based on modelling results published after this Guidance Manual. |
| Flood | Use factors from Table 5.2 with the rainfalls used to drive the design floods | Approach specialist hydrologists for targeted advice |
| Water deficit (for irrigation) | Use weather generator in CLIMPACTS for locations of interest, for low-middle-high greenhouse gas scenarios | |
| Snow | Assume snowline rises by 140 m for each 1°C increase in annual average temperature | Requires research and development of linked spatial weather generator/snow budget modelling software for future projections |
| Strong winds | Increase of 40% by 2030s and 100% by 2080s in annual frequency of winds above 30 m/s (but see next column). Increase of 3% in annual maximum wind speed | Changes in the frequency of strong winds and ARI of damaging winds are still very uncertain. Consult with a science provider if screening indicates possible problems |
| Sea level, coastal hazard | Refer to coastal hazards Guidance Manual | Refer to coastal hazards Guidance Manual |
Notes for Table 5.1: These are suggestions for scenario analyses, and not firm scientific predictions. Entries in this table - especially for strong winds and heavy rainfall - are likely to be revised as science and modelling develop further. Many of the entries in the "initial screening study" column focus on the 2030s and the 2080s. For other planning horizons within the coming century, climate factors for screening studies can be estimated by interpolating between present, 2030 and 2080 values.
- MFE will be placing a list of science and service providers that can help with climate change issues on their website. NIWA can provide regional climate scenario details and climate data, universities contain staff with climate expertise, many regional councils hold local climate data and expertise, and engineering and planning consultancies, university groups and Crown Research Institutes can assist with assessments and planning.
- CLIMPACTS: This is an integrated assessment model developed by the International Global Change Institute (IGCI, University of Waikato) and a consortium of CRIs (see Glossary). An "open-framework" version of the model, called SimCLIMtm, is now available which allows users to develop their own model for any area and spatial resolution. To request a demonstration copy of CLIMPACTS or to find out more about CLIMPACTS or SimCLIMtm, contact IGCI (email: igci@waikato.ac.nz; http://www.waikato.ac.nz/igci).
- This requires site-specific historical temperature data. Approach a climate data provider (Note 1).
- Because rainfall is so critical for many applications, we suggest using low, medium and high scenarios for screening studies rather than just a middle scenario.
- HIRDS is the High Intensity Rainfall Design System available on CD from NIWA.
- As explained in Section 2.2.4, there is still considerable uncertainty in the likely size of future changes in heavy rainfall events. The heavy rainfall guidance provided here should be viewed as interim, and is likely to be updated once new model results become available.
