Extended Data Fig. 4: Change in zonal-mean quantities for mid-Holocene (6 ka) minus preindustrial in a nine-model mean.

Each panel is a Hovmöller figure showing zonal-mean climate anomalies by latitude (0° N to 90° N, y-axis) and calendar month (1–12, x-axis). a, The change in forcing is strongest in summer, and the insolation gradient change is weaker through much of the year. b, High-latitude warming anomalies dominate between June and December, with reductions in sea-ice extent likely to be causing the anomalous propagation of polar warmth into winter. c, The localized meridional temperature gradient anomalies (the derivative of temperature) shows weaker temperature gradients at 70° N between September and June. Negative values indicate a reduced temperature gradient. During summer (June through September) the temperature gradient anomaly is negative between 15° N and 50° N. d, Changes in 500 hPa geopotential height. e, Vertically integrated zonal winds show reduced jet-stream strength for much of the year. f, Vertically integrated omega (vertical motion, with positive values indicating anomalous downward motion). g, Precipitation minus evaporation anomalies show decreases in mid-latitude net precipitation through much of the year. h, Evaporation. i, Total precipitation shows decreases in mid-latitude rainfall through much of the year. Large increases in localized total precipitation correspond to a shift in the intertropical convergence zone and increased monsoon strength. j, Convective precipitation shows enhanced monsoon systems. k, Large-scale precipitation (including extratropical cyclones) decreases from January through October, with the largest reductions in August. Vertically integrated quantities (e,f) are ‘mass-weighted’: the quantities are integrated on pressure levels from the surface to the top of atmosphere and divided by the standard gravity, then multiplied by −1 to give more easily interpretable quantities.