From CO2 Science: It is repeatedly alleged by climate alarmists that rising atmospheric CO2 is causing drought events to become more frequent and/or more severe. Proof of such allegations, however, has remained elusive, as multiple historical studies have revealed there has been no long-term change in drought trends over the modern era of rising CO2 (see, for example, the many research studies CO2 Science has highlighted on this topic in their Subject Index under the subheading of Drought on this page). The latest study to demonstrate as much comes from the work of Musei et al. (2021).
Paper reviewed: Musei, S.K., Nyaga, J.M. and Dubow, A.Z. 2021. SPEI-based spatial and temporal evaluation of drought in Somalia. Journal of Arid Environments 184: 104296, doi.org/10.1016.j.jaridenv.2020.104296.
Focusing on the drought-prone country of Somalia, the three researchers analyzed spatial-temporal patterns of the standardized precipitation evapotranspiration index (SPEI), a commonly-used measure of drought, over the 36-year period 1980-2015. SPEI data were obtained from the Global SPEI database at a spatial resolution of 0.5 degrees and a temporal resolution of one month.
Figure 1 below plots the distribution of drought on timescales of 1, 3, 6 and 12 months, illustrating the variability of these temporal sequences of drought. As noted there, it is seen that drought events are more frequent, but short in duration, at the smaller timescale sequences. This is not surprising given the larger temporal smoothing of the data at the larger timescale sequences. More importantly, however, none of the drought series presented in the figure below show any hint of recent change that might be construed to be driven by rising atmospheric CO2. Indeed, as reported by Musei et al. “the SPEI-based drought evaluation in Somalia reveals no specific spatial and temporal pattern of drought events.” And so, those climate alarmists who remain hell-bent in alleging rising CO2 is making droughts more frequent and/or severe will have to look elsewhere for proof than drought-prone Somalia!
Figure 1. Time series of drought in Somalia based on SPEI values averaged over 1 (Panel a), 3 (Panel b), 6 (Panel c) and 12 (Panel d) month periods. Source: Musei et al. (2021).