Furthermore, using the modified Mann–Kendall test (Mann 1945; Kendall 1975; Yue & Wang 2004) that is both non-parametric and applicable to data that are serially correlated, Table 4 shows the test of statistical significance of linear trends in the annual frequency of occurrence of the CTs under all the considered experiments. There is a statistically significant decrease in the frequency of occurrence of CT1+ in the historical climate (both from ERA5 and the GCM ensemble). Also, toward the end of the 21st century under the SSP5-8.5 scenario, the frequency of occurrence of CT1+ is projected to decrease (Table 4). From Supplementary Material, Table A1, six of the ensemble members agree with ERA5 on the significant decreasing trend in the frequency of occurrence of CT1+ under the historical climate. Also, from Supplementary Material, Table A2, eight of the ensemble members agree on the significant projected decrease in the frequency of occurrence of CT1+. CT1− is a summer BL CT. Table 4 shows that the increase in the frequency of occurrence of CT1− is statistically significant both under the historical and SSP5-8.5 experiments. From Supplementary Material, Table A1, six of the ensemble members agree with ERA5 on the significant increased frequency of occurrence of CT1−; and eight of the ensemble members agree on the significant projected increase in the frequency of occurrence of CT1− (Supplementary Material, Table A2).