Changes in dryland temperature and precipitation are essential components of dryland climate change. This study applies the use of the monthly reanalysis data product of ERA5, which has a spatial resolution of 0.25°, to investigate the changes in the dryland climate between 1979 and 2018. The result revealed warming and drying of the drylands in recent decades, most notably in the current decade. The general global dryland temperature and precipitation increased and decreased significantly (0.01 significance level) at the rate of 0.032°C·year⁻¹ and 0.074 mm·month⁻¹·year⁻¹, respectively, in the last 40 years. Although precipitation generally decreased over the drylands, summer precipitation increased over southern Africa and Australia as well as northern Africa and south Asia dryland areas. Variation in the warming rate over the dryland zones at different periods was also observed. The semiarid and dry subhumid warmed continually from the first decade (0.02°C·year⁻¹ and 0.017°C·year⁻¹) to the fourth decade (0.077°C·year⁻¹ and 0.065°C·year⁻¹, respectively), while the hyperarid warmed at a slower rate in the last two decades compared to the prior decades. More intense warming was also observed in the areas where precipitation decreased, suggesting the effect of reduced evaporative cooling. These changes have implications on the dryland environment, such as aridity changes, which could affect the sustainable development of the areas through the corresponding impact on the ecosystem.

The diurnal temperature range (DTR) has generally decreased at global scale according to the IPCC reports and previous publications. Here, we examined the change in DTR within the past four decades and found that DTR decreased in wet areas, but it increased in dry areas. This is because the daily minimum air temperature (T_min) increased at a slower rate than the daily maximum air temperature (T_max) in the dry areas, while it increased more rapidly in the wet areas. The changes in cloud cover, water vapour and moisture flux were observed to have contributed to the observed change in DTR. The change in moisture flux largely contributed to this change through the indirect effect on the change in water vapour across the aridity gradient. The significant impact of moisture flux is linked to the differential change in moisture flux between the dry and wet zones.

This research aims to determine the temperature extremes for Ikeja (Lagos), Osogbo (Osun) and Maiduguri (Borno), Nigeria, West Africa using Statistica analytical tool. Thirty (30) years daily maximum and minimum temperature data for Lagos, Osogbo and Maiduguri used for this study were collected from Nigeria Meteorological Agency (NIMET), Oshodi, Nigeria. Analysis of extreme temperature trend indicated that in Ikeja the percentage occurrence of warm days (TX90P) in which the maximum temperature is above 34°C (90^th percentile value) is increasing and the percentage occurrence of cold days (TX10P) in which the maximum temperature is below 28°C [10^thpercentile value] is decreasing, in Osogbo the percentage occurrence of warm days (TX90P) in which the maximum temperature is above 35°C [90^th percentile value) is increasing at a slower rate whereas the percentage occurrence of cold days (TX10P, number of days) in which the maximum temperature is below 27°C [10^th percentile value] is constant while in Maiduguri the percentage occurrence of warm days (TX90P, number of days) in which the maximum temperature is above 41°C [90^th percentile value] is constant whereas the percentage occurrence of cold days (TX10P, number of days) in which the maximum temperature is below 30°C [10^th percentile value] is slightly increasing. Percentage of warm days indicate constant value at around 13-15% during the three (3) decades under investigation across the study areas while day time cooling increases slightly by 2% in Ikeja, 1% in Osogbo and 3% in Maiduguri significant level and Cold night decrease at 1% in Ikeja and remain constant in Osogbo but decrease by 5% in Maiduguri significant level.