Readers of my weblog know I have been very critical of peer-reviewed papers and research projects that present multi-decadal global climate model predictions as robust science; e.g. see
The models predictions used to create these scenarios cannot even be verified until decades from now, and, even in a hindcast mode, they have never been able to satisfactorily predict regional climate variability under the current climate, much less how the regional weather features would change under human climate forcings.
The abstract reads [highlight added]
“Probable changes in mean and extreme precipitation in East Africa are estimated from general circulation models (GCMs) prepared for the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4). Bayesian statistics are used to derive the relative weights assigned to each member in the multimodel ensemble. There is substantial evidence in support of a positive shift of the whole rainfall distribution in East Africa during the wet seasons. The models give indications for an increase in mean precipitation rates and intensity of high rainfall events but for less severe droughts. Upward precipitation trends are projected from early this (twenty first) century. As in the observations, a statistically significant link between sea surface temperature gradients in the tropical Indian Ocean and short rains (October–December) in East Africa is simulated in the GCMs. Furthermore, most models project a differential warming of the Indian Ocean during boreal autumn. This is favorable for an increase in the probability of positive Indian Ocean zonal mode events, which have been associated with anomalously strong short rains in East Africa. On top of the general increase in rainfall in the tropics due to thermodynamic effects, a change in the structure of the Eastern Hemisphere Walker circulation is consistent with an increase in East Africa precipitation relative to other regions within the same latitudinal belt. A notable feature of this change is a weakening of the climatological subsidence over eastern Kenya. East Africa is shown to be a region in which a coherent projection of future precipitation change can be made, supported by physical arguments. Although the rate of change is still uncertain, almost all results point to a wetter climate with more intense wet seasons and less severe droughts.”
An excerpt from the text reads
“The higher frequency of flooding observed in East Africa in recent years could give indications that the CGCM-simulated precipitation responses are already occurring. Although the time series of the simulated precipitation show upward trends from early in the present century, parts of East Africa could still be experiencing drier conditions. For example, local trends in Rwanda and Burundi (region III) have been negative over the last decades of the twentieth century, either because of natural variability or model deficiencies in this complex region. From an applications perspective, there have also been reports of continued decline in streamflow and water levels in, for example, Lake Victoria, which may seem paradoxical given the recent high frequency of flooding in East Africa. We note that river/ dam levels are also determined by other factors (e.g., water use, drainage, and evaporation), which have not been considered in this paper.”
This text shows that even with the limited hindcast validation of their model results, they do not agree in some regions with their forecast trend. They provide qualitative rationalizations to dismiss these areas of disagreement. Such inadequacies should have alerted the Editor who handled this paper that the study is not robust, as it is unable to even accurately simulate the current climate.
Until, the funding agencies and journals recognize that this is not robust science, we will continue to read such flawed studies.