Climate Statistics

Climate trends of these scenarios were analyzed by comparing climate statistics from the baseline 1975 to 2005 climate period to the predicted climate scenarios for the periods for 2035 to 2065 and 2065 to 2095. The climate statistics that were compared are monthly and annual mean of daily maximum and minimum air temperatures, monthly and annual precipitation totals, the number of wet days, and the number of days over 30 ºC.

Table 15. Selected GCMs from extremes and percentile ensemble methods.

Mode l Sce nario Re alization CESM1-CAM5 RCP85 r1i1p1 CSIRO-Mk3-6-0 RCP45 r8i1p1 CSIRO-Mk3-6-0 RCP85 r8i1p1 MIROC5 RCP26 r5i1p1 CanESM2 rcp45 r4i1p1 CanESM2 rcp45 r5i1p1 CanESM2 RCP85 r5i1p1 CSIRO-Mk3-6-0 RCP26 r2i1p1 CSIRO-Mk3-6-0 RCP45 r5i1p1 CSIRO-Mk3-6-0 RCP85 r5i1p1 CSIRO-Mk3-6-0 rcp85 r9i1p1 EC-EARTH rcp26 r12i1p1 HadGEM2-ES RCP45 r2i1p1 MIROC5 rcp85 r2i1p1 BNU-ESM rcp26 r1i1p1 BNU-ESM rcp85 r1i1p1 CSIRO-Mk3-6-0 rcp85 r8i1p1 EC-EARTH rcp26 r12i1p1 CanESM2 rcp85 r3i1p1 CanESM2 rcp85 r5i1p1 CESM1-CAM5 rcp26 r2i1p1 CSIRO-Mk3-6-0 rcp26 r2i1p1 CSIRO-Mk3-6-0 rcp26 r3i1p1 CSIRO-Mk3-6-0 rcp45 r4i1p1 CSIRO-Mk3-6-0 rcp85 r4i1p1 CSIRO-Mk3-6-0 rcp85 r5i1p1 HadGEM2-ES rcp26 r3i1p1 MIROC5 rcp45 r3i1p1 Extre me s GCM Sce nario Time Slice Me thod

Extre me s Pe rce ntile Ense mble 2035-2065 2065-2095 Pe rce ntile Ense mble

4.1.3.12035-2065

In Figure 14, the changes in monthly mean maximum and minimum temperatures and number of days greater than 30ºC are plotted for the 2035-2065 period. The monthly changes in mean maximum temperature demonstrated a median increase ranging from 1.8 to 2.8ºC. The CanESM2- RCP8.5-r4 scenario exhibited the highest increase in monthly mean maximum temperature for August with an absolute change of 5.0ºC, raising the monthly mean maximum temperature to 34.6ºC compared to the Tabora baseline mean maximum temperature 29.6ºC. The monthly changes in mean minimum temperature demonstrated a median increase ranging from 2.0 to 3.2ºC for the dry season months from May to September. The wet season shows median minimum temperature increases ranging from 1.8 to 2.6ºC. The CanESM2-RCP8.5-r5 scenario exhibited the highest increase in monthly mean minimum temperature for August with an absolute change of 5.7ºC raising the monthly mean minimum temperature to 20.9ºC compared to the Tabora baseline mean minimum temperature of 15.2ºC. All scenarios anticipate the number of days above 30ºC, or 30 degree days to increase in all months. The months with the greatest increase in hot days are June, July and August with median increases of 13, 20 and 17 days warmer than 30ºC. The increase in 30 degree days in the dry season may impact soil water as a higher rate of evaporation would be expected with higher temperatures.

The mean monthly total precipitation for the 2035-2065 time slice, see Figure 15, does not show very significant changes from the baseline period. Precipitation and temperature are plotted for each scenario with the results from WaNuLCAS in Appendix F and visualize the variability between generated scenarios.

Figure 16 shows the annual mean temperatures and total precipitation over the 2035-2065 period to demonstrate the variability of each model within the 30 year period, compared to the Tabora baseline period from 1975 to 2005. The annual total precipitation demonstrates the variability of precipitation between models better than monthly mean total precipitation over the 30 year period as the variations are not lost by taking the average for the 30 year normal.

4.1.3.2 2065-2095

In Figure 17 the changes in monthly mean maximum and minimum temperatures and the number of days greater than 30ºC are plotted for the 2065-2095 period. The monthly changes in mean

maximum temperature demonstrated a median increase ranging from 3.1 to 4.4ºC for the dry season months from May to September. The wet season shows median maximum temperature increases ranging from 2.8 to 3.2ºC. The EC-EARTH-r12 -RCP2.6 scenario exhibited the highest increase in monthly mean maximum temperature for August with an absolute change of 7.6ºC raising the monthly mean maximum temperature to 37.9ºC compared to the Tabora baseline mean maximum temperature 29.6ºC. The monthly changes in mean minimum temperature demonstrated a median increase ranging from 3.4 to 3.9ºC for the dry season months from May to September. The wet season shows median minimum temperature increases ranging from 3.9 to 5.2ºC in the dry season and 3.3 to 4.3ºC in the wet season. The EC-EARTH-r12 -RCP2.6 scenario exhibited the highest increase in monthly mean minimum temperature for August with an absolute change of 8.6ºC raising the monthly mean minimum temperature to 23.7ºC compared to the Tabora baseline mean minimum temperature of 15.2ºC.

All scenarios anticipate the number of 30 degree days to increase in all months. The months with the greatest increase in hot days are May, June, July, and August with median increases of 14, 22, 26, and 19 days warmer than 30ºC. These results for May and June are particularly significant compared the Tabora baseline. May and June have 0 and 1 day above 30ºC respectively whereas the predicted changes would increase the days to 15 and 22 days above 30ºC.

The BNU-ESM scenarios model a significant change in precipitation for August, where the number of wet days over the 30 period average at 28 days compared to the Tabora baseline period of 1.4 wet days. The BNU-ESM model ranked low in performance in the compromise programming validation method, which may suggest the BNU-ESM model structure is not appropriate for the Tabora region. The mean monthly total precipitation for the 2065-2095 time slice, see Figure 18, does not show very significant changes from the baseline period. The precipitation graphs for all models are in Appendix F and visualize the variability between generated scenarios.

Figure 19 shows the annual mean temperatures and total precipitation over the 2065-2095 period to demonstrate the variability of each model within the 30 year period, compared to the Tabora baseline period from 1975 to 2005. The trend for the annual maximum temperature increases over the 30 year period and the annual total precipitation decreases over the 30 year period. The

variability of precipitation is better represented by the annual total precipitation as the range is not smoothed by averaging.

The largest changes in temperatures for both time periods are anticipated to occur in the dry season month from May to August, it is possible that these changes may not significantly impact maize crop growth as the growing season takes place from December to April. The individual plot of maximum and minimum temperature and precipitation for each model and time slice is in Appendix F with results from the WaNuLCAS simulations.

Figure 19. Annual climate statistics for temperature and precipitation from 2065 to 2095 compared to the Tabora baseline data.