1. Compo GP, Whitaker PD, Sardeshmukh N, Matsui RJ, Allan X, Yin BE, Gleason RS, Vose G, Rutledge P, Bessemoulin S, Brönnimann M, Brunet RI, Crouthamel AN, Grant PY, Groisman PD, Jones M, Kruk AC, Kruger GJ, Marshall M, Maugeri HY (2011) The Twentieth Century Reanalysis Project. Quarterly J Roy Meteorol Soc 137:1–28. doi: 10.1002/qj.776
2. CSA (Central Statistical Agency) (2007) Central Statistical Agency Population and Housing Census of Ethiopia, Addis Ababa. Retrieved August, 2013, from CSA database
3. Gebre H, Kindie T, Girma M, Belay K (2013) Trend and variability of rainfall in Tigray, Northern Ethiopia: analysis of meteorological data and farmers’ perception. Acad J Agric Res 1(6):88-100
4. Hare W (2003) Assessment of Knowledge on Impacts of Climate Change, Contribution to the Specification of Art, 2 of the UNFCCC, WBGU
5. IPCC (2001a) Climate change 2001, the scientific basis. Cambridge University Press, Cambridge