No abstract

Mapping potential changes in bioclimatic characteristics are critical for planning climate change adaptation and mitigation goals. Assessment of such changes is particularly important for Southeast Asia, which has one of the world's highest ecological diversity. Twenty-three CMIP6 GCMs are used in this study to evaluate the change in 11 thermal bioclimatic indicators of Southeast Asia for two shared socioeconomic pathways (SSPs), 2-4.5 and 5-8.5. The spatial changes in the ensemble mean, 5th, and 95th percentile of each indicator for the near (2020-2059) and far (2060-2099) futures for the two SSPs to understand the changes with time and associated uncertainty. The results indicate large spatial heterogeneity and temporal variability in projected changes in bioclimatic indicators. A higher change was projected in the mainland SEA for the far future and less in maritime SEA for the near future. At the same time,uncertainty in the projected bioclimatic indices was higher for mainland SEA than maritime SEA. The multimodel ensemble mean (MME) revealed a change in mean temperature in the range of -0.71 to 3.23 °C for the near and 0.00 to 4.07 °C for the far future. The diurnal temperature range was projected to reduce over most of SEA in the range of -1.1 to -2.0 °C, while isothermality to decrease by -1.1 to -4.6%. The decrease in isothermality along with a decrease in seasonality indicates a possible shift in climate, particularly in the north of mainland-SEA in the future. Maximum temperature in the warmest month/quarter was projected to increase a little more than the coldest month/quarter and the mean temperature in the driest month to increase more than the wettest month. This would cause an increase in the annual temperature range in the future.

The global climate models (GCMs) performances of the recently released Coupled Model Intercomparison Project phase 6 (CMIP6) compared to its predecessor, CMIP5, are evaluated to anticipate the expected changes in climate over Egypt. Thirteen GCMs and their multi‐model ensemble (MME) of both CMIPs were used for this purpose. The future projections were compared for two radiative concentration pathways (RCP 4.5 and 8.5) and two shared socio‐economic pathways (SSP 2–4.5 and 5–8.5). The results revealed improvement in most CMIP6 models in replicating historical rainfall, maximum temperature (Tmax), and minimum temperature (Tmin) climatology over Egypt. The MME of the CMIPs revealed that both could reproduce Egypt's spatial distribution and seasonal climate variability. However, the bias in CMIP5 was higher than that for CMIP6. The uncertainties in simulating seasonal variability of rainfall and temperatures were lower for CMIP6 compared to CMIP5. The future projection of rainfall using CMIP6 MME revealed a higher reduction of precipitation (10–26 mm) in the economically crucial northern region than that estimated using CMIP5 (0–17 mm), compared to 133.5 mm rainfall in the base period. CMIP6 also projected a 0.74–1.63°C more rise in Tmax and Tmin compared to CMIP5 by the end of the century. The study indicates more aggravated scenarios of climate changes in Egypt than anticipated earlier, using the CMIP5 models. Therefore, Egypt needs to streamline the existing adaptation and mitigation measures to account for climate projections.