Another observation relevant to the TWAP transboundary lakes analyses is that lakes are increasingly being linked to water-related uncertainties associated with projected climate change impacts, a major consideration being possible modifications to the global hydrologic cycle. This issue is relevant within the context of the TWAP transboundary lake goals, particularly regarding lake basin adaptation and restoration strategies.

To this end, the IPCC scenario RCP8.5 (i.e., maximum temperature increase under a high emissions ‘business-as-usual’ scenario) was assessed using the IPSL-CM5A-LR model to make predictions extending to 2070. Predictions were made for the TWAP transboundary lake basins for the period from 2010 to 2070, as a worst-case basis for calculating predicted changes in monthly mean air temperatures and mean annual precipitation.

This analysis indicated the mean monthly air temperature for all 206 transboundary lake basins is predicted to generally increase in all five lake study regions by about 4 to 6 ℃, and possibly up to 8 ℃ in the high latitude regions.

The mean annual precipitation is predicted to increase for the European, African and North American transboundary lake basins. They are predicted to remain about the same for those in Asia, and to decrease for those in South America.

Changes in Mean Monthly Air Temperature and Mean Annual Precipitation for 206 Transboundary Lakes, 2010 to 2070

Focusing on the African transboundary lake basins clearly illustrates that significant differences in these parameters can be observed on a sub-continental scale. It was predicted, for example, that the transboundary lake basins located in the northern, middle and eastern African sub-regions would receive more precipitation in 2070 than in 2010. In contrast, those in western and southern Africa would receive less precipitation. All the African transboundary lake basins assessed would experience a higher mean atmospheric temperatures in 2070 than in 2010, with those in the western and eastern African sub-regions experiencing notably higher mean temperatures than those in the remaining sub-regions.

Changes in Mean Monthly Air Temperature and Mean Annual Precipitationfor African Transboundary Lakes, 2010 to 2070

Such strong sub-regional tendencies make it problematic to use combined sub-continental ranking scores to make unilateral and unequivocal comparisons regarding the prioritization of transboundary lake threats, which can readily lead to erroneous conclusions regarding the Adj-HWS, Incident BD and RvBD threat ranks. However, although not without controversy, such observations suggest that potential threats associated with climate-driven uncertainties also are factors to be appropriately considered in ranking the threats to transboundary lakes.