Fig. 4: Stratospheric water vapor trends with and without multi-decadal variations.

Panels a–c show linear trends with MDVs: trends estimated for the full simulation period 1980–2020 (a); trends for the period 2005–2020 from CLaMS simulation (b); trends for the period 2005–2020 from the SWOOSH dataset (c). Panels f–h show the corresponding trends without MDVs (see “Methods”). The color shading and contours show trends in ppmv per decade and percentage per decade (relative to the water vapor mixing ratio averaged over the full period), respectively. Statistically significant trends (at the 5% significance level) are dot-hatched. The thick magenta line indicates the climatological tropopause. Magnitudes of 15-year trends with (d, e) and without MDV (i, j) estimated from CLaMS (gray) and SWOOSH (cyan) are shown for the southern mid-latitudes (25–50°S, 500–600 K, d and i) and northern mid-latitudes in the mid-stratosphere (25–50°N, 500–600 K, e and j). The dots represent the means and lines depict the spread spanning from the 2.5th to the 97.5th percentile. The vertical dotted lines indicate thresholds for the trends to reach significance at the 5% level.