This is part of the Regional Summary series at www.appinsys.com/GlobalWarming
East Africa has no continuous long-term stations in the GISS database.
The following figures show average temperature anomalies for 1880 – 2006 (from the GHCN database) and then superimposed on the IPCC model plot (from AR4 Fig 9.12) (pink= models with CO2, blue= models without CO2, black= observed).
Unfortunately there are no long-term temperature stations in Eastern Africa in the GISS database. Zanzibar displays warming in the 1930’s, while Dar Es Salaam has the period missing.
Many partial records for the region indicate no distinct trend.
The disappearing Mount Kilimanjaro glacier has been touted as an effect of anthropogenic global warming. However, its decline is due to solar effects and lack of precipitation. In fact the Mount Kilimanjaro glaciers mainly sublimate directly to the atmosphere, rather than melting into runoff water. The temperature never gets above freezing, so melting can occur only in small localizations.
A recent study of Mount Kilimanjaro: “Kilimanjaro Glaciers: Recent Areal Extent From Satellite Data and New Interpretation of Observed 20th Century Retreat Rates” by Cullen, Molg, Kaser, Hussein, Steffen, and Hardy (Tropical Glaciology Group, Department of Earth and Atmospheric Sciences, University of Innsbruck, Austria; Cooperative Institute for Research in Environmental Sciences, University of Colorado, and Climate System Research Center, Department of Geosciences, University of Massachusetts) (Geophysical Research Letters, 2006) states: “All ice bodies on Kilimanjaro have retreated drastically between 1912–2003. Despite air temperatures always being below freezing, areal retreat of plateau glaciers is governed mostly by solar radiation induced melt on vertical walls that characterize their north and south margins [Mölg et al., 2003]. Though the processes responsible for the formation of the vertical walls is still not well understood, once established, the vertical wall retreat is irreversible, and no change in 20th century climate appears to have significantly altered their ongoing demise. ... Rather than changes in 20th century climate being responsible for their demise, glaciers on Kilimanjaro appear to be remnants of a past climate that was once able to sustain them. Hastenrath [2001, 2006] suggests an increase in net shortwave radiation, accompanied by a decrease in cloudiness and precipitation, initiated the retreat of the glaciers during the last two decades of the 19th century. This is supported by a recent finding that a higher frequency of climatically significant Indian Ocean Zonal Mode events in the 19th century (1820–1880) may have provided a mechanism to contribute to a wetter climate in East Africa, and thus stable glaciers.“
In another paper “Modern Glacier Retreat on Kilimanjaro as Evidence of Climate Change: Observations and Facts” by Kaser, Hardy, Molg, Bradley and Hyera (Tropical Glaciology Group, Department of Geography, University of Innsbruck, Austria, Climate System Research Center, Department of Geosciences, University of Massachusetts, and Tanzania Meteorological Agency) (International Journal of Climatology, 2004) [http://www.geo.umass.edu/faculty/bradley/kaser2004.pdf] the researchers state: “From a hydrological point of view, meltwater from Kibo’s glaciers has been of little importance to the lowlands in modern times… Most glacier ablation is due to sublimation, and where ice does melt it immediately evaporates into the atmosphere… The scenario presented offers a concept that implies climatological processes other than increased air temperature govern glacier retreat on Kilimanjaro in a direct manner. However, it does not rule out that these processes may be linked to temperature variations in other tropical regions.” The following figure is from this paper, showing the decrease in glacier extents going back at least as far as the late 1800s.
An article in the American Scientist (“The Shrinking Glaciers of Kilimanjaro: Can Global Warming Be Blamed” by Philip Mote and Georg Kaser, July-August 2007) blames a decrease in precipitation and an increase in sublimation. The following figure shows the temperature trend for 1958 – 2006 for the Kilimanjaro summit altitude from “reanalysis” of weather-balloon readings. The authors describe the physical features of the glaciers (penitents, vertical walls, etc.) indicating that melting is not causing the disappearance.
The following figure shows the extensive deforestation around Mt Kilimanjaro. Given that “an estimated 62 percent of precipitation occurs over land as a result of evapotranspiration from lakes and wetlands and dense vegetation, particularly forests, which pump ground water into the sky.” [http://www.irinnews.org/report.aspx?reportid=61528] the extensive deforestation will have a significant impact on precipitation.
A recent South African technical paper by a Professor Emeritus of the Department of Civil and Biosystems Engineering of the University of Pretoria, and other engineers (“Linkages Between Solar Activity, Climate Predictability and Water Resource Development” by W J R Alexander, F Bailey, D B Bredenkamp, A van der Merwe and N Willemse Journal of the South African Institution of Civil Engineering, Vol. 49 No 2, June 2007) provides evidence of the relationship between solar activity and hydrological events [http://nzclimatescience.net/images/PDFs/alexander2707.pdf]. The following figure is from their paper, showing the correlation between sunspot number and lake level for Lake Victoria in East Africa. This link between sunspot cycle and climate has been confirmed by a new study showing that sunspot cycles can be used to predict heavy rains, flooding and subsequent disease outbreaks in East Africa. [http://www.nsf.gov/news/news_summ.jsp?cntn_id=109789].
Much of the media hype says that Africa will suffer from global warming (see: www.appinsys.com/GlobalWarming/ReutersAfrica.htm). However, the World Bank World Development Report “Agriculture for Development” 2008 [www.worldbank.org/WDR2008] states: “Sub-Saharan African countries account for 89 percent of the rural population in agriculture-based countries … real agricultural GDP growth in Sub-Saharan Africa has accelerated from 2.3 percent per year in the 1980s, to 3.3 percent in the 1990s, and to 3.8 percent per year between 2000 and 2005. Rural poverty has started to decline in 10 of 13 countries analyzed over the 1990–2005 period.”