Temperature evolution from 1956 to 2015 in Burkina Faso: cases of Ouagadougou and Ouahigouya

The study examines the evolution of the annual values of temperatures (average, minimum, maximum), bioclimatic variables and daily temperature conditions over the period 1956-2015. In Ouagadougou, between 1956-1985 and 1986-2015, average values increased from 28.2 degrees C to 28.8 degrees C for TM, from 17.4 degrees C to 17.9 degrees C for TN and from 38.2 degrees C to 38.8 degrees C for TX. The bioclimatic variables SH (BIO9 - wet months) and SC (BIO10 - hot months) also increase: average of 26.6 degrees C then 27.5 degrees C for the first and of 31.5 degrees C then 32.3 degrees C for the second. In contrast, the average value of SF (BIO 11 - fresh month) decreases slightly from 26.1 degrees C to 26.0 degrees C. Between the two periods considered, the evolution of temperatures results in a decrease in the average frequencies of TN10p (fresh nights: 101 days in the period 1956-1985, then 86 days) and TX10p (fresh days: 76 days, then 67 days) and by an increase in TN90p (hot nights: 61 days, then 95 days) and TX 90p (hot days: 68 days, then 77 days). In Ouahigouya, the increase in temperatures is also very pronounced. Between 1956-1985 and 1986-2015, the average value of TM increases from 28.6 degrees C to 29.4 degrees C. But TX remains stable (averages of 39.6 degrees C and 39.7 degrees C respectively). It is thus the TN values that make the difference (averages of 16.7 degrees C and 18.5 degrees C). The bioclimatic variables increase all three (averages of 27.6 then 28.3 degrees C for SH, 32.0 then 33.0 degrees C for SC and 25.6 then 26.1 degrees C for SF). The average values of TN10p, TN90p, TX10p and TX90p, which were 123, 90, 63 and 109 days, respectively, in 1956-1985, become 69, 115, 59 and 114 days. As in Ouagadougou, the freshness are less frequent and the heats more frequent, but the most striking fact here is the rise in minimum temperatures.