Hi,
I have been working with the new data underpinning the CS3 climate interactive atlas, and specifically on the SPEI6 data for the historical time-series (1970-2014 or 2022) from both CMIP6 and ERA5. I observe a clear downward trend in the SPEI6 data for the historical time-series, both in the re-analysis and the modelled data. The mean SPEI6 in 1971 is around 0.5 while it goes down to around -1 in 2022. The CMIP6 also seem to have other issues: there are some unexpected peaks in the spei6 value in the historical period. Could you help me understand why this trend is observed? Am I interpreting the CS3 data incorrectly and if so how can I transform it to obtain a correct SPEI6 global monthly time-series? I compared the trends with published papers on the SPEI6 computed using ERA5 and they do not seem to exhibit the same trend.
Thank you.
Best,
Paola