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Observational analysis shows a positive trend in solar irradiance across three wavelengths in Nigeria, indicating desert encroachment risks.
A locally developed python programming language algorithm was used in the deduction of optical depth (OD) for solar irradiance measurement at 500nm, 675nm and 875nm solar wavelengths at Ilorin (Long. 8.573°N, Lat. 4.5444°E) Nigeria. Results obtained indicate a positive trend in all three wavelength measurements in January of 2003, 2013, and 2024. The correlation with report of desert encroachment which was measured as about 0-6km per year indicates clearly that OD measurement can be used as a precursor to desert encroachment. Results of measurements made in November, December and January of 2003/2004, 2013/2014 and 2024/2025 give a positive trend in both parameters especially at the 500nm and 675nm wavelengths. Hence the result is quite encouraging being the first of such comparison at the sub-Saharan site.
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Godwin et al. (2025) studied this question.
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