Temperature trends and evidence for Elevation Dependent Warming on Mount Kenya

Abstract

Global climate models are important tools for understanding differential impacts of climate change around the world. These models depend on the existence of accurate and timely data for calibration and validation, and in some parts of the world such data is scarce. Tropical mountains are modelled to warm faster than other areas of the globe, due to a theory known as Elevation Dependent Warming (EDW). However empirical evidence for EDW is limited, particularly in tropical Africa. This study examines three types of datasets (reanalysis datasets, meteorological station data, and in-situ data loggers) to investigate temperature trends in Mount Kenya, an equatorial mountain in central Kenya. Reanalysis datasets investigated were TerraClimate (1958-2021), ERA5 (1979- 2022), and CFSR (1979- 2022), and meteorological stations examined were Munyaka Station (2070 m.a.s.l.), Naro Moru Gate Station (2420 m.a.s.l), and Naro Moru Met Station (3048 m.a.s.l), all with data from 1991-2022. Finally, six in-situ temperature loggers were placed at 200 m vertical elevation intervals from 3000 m.a.s.l to 4000 m.a.s.l, and these data were compared with historical observations at comparable elevations. The reanalysis datasets all displayed significant warming, but with widely varying magnitudes, ranging from 0.12°C to 0.48°C/decade. Meteorological station data, on the other hand, did not provide any evidence of warming. In-situ data loggers showed warming of 4-5°C for of absolute minimum temperatures since the 1950s. Despite the differences in the data sources, there was general agreement for lapse rates, which ranged from 0.5°C to 0.55°C/100 m. Each data source has its shortcomings, and a thorough knowledge of error and conditions of use and is needed before a dataset can be put to use.