Trend and Variations of Surface Air Temperatures across Selected Eco-Climatic Zones in Nigeria

Abstract

The trends and variability in surface air temperatures over selected eco-climatic zones in Nigeria were assessed using Merra-2 datasets from 1981 to 2018. A total of 15 stations spread across the eco-climatic zones in Nigeria were used for this study. The Mann-Kendall, linear trend and Sen’s slope trend test, time series plots and descriptive statistics were used. The coefficients of variability of surface air maximum temperature showed low variability for the Mangrove-swamp rainforest and moderate variability for the Guinea-wooded, Sudan and Sahel savannas. Similarly, the coefficients of variability of surface air minimum temperature showed moderate variability for all the selected eco-climatic zones. The M-K trend test showed that 14 stations had upward trends and 1 downward trend, with 13 stations having statistically significant trend in air surface maximum temperature. All the stations had statistically significant upward trends in air surface minimum temperature. The average increase in maximum and minimum air surface temperatures is estimated to be about 0.035°C and 0.036°C per year, respectively. For Nigeria, the average air surface temperature is estimated to increase by about 0.036°C per year, and the average air surface temperature is estimated to have increased by about 1.4°C over the 38 years. This study then gives a linear trend projection of about 4.3°C increase in estimated mean air surface temperature by year 2100 in Nigeria.