Will Surface Winds Weaken in Response to Global Warming?

Abstract:

A weakening of the tropical tropospheric circulation has been inferred from historical observations and model projections, but recent satellite-based trends in surface wind speed, precipitation, and evaporation offer a conflicting view. Here this apparent contradiction is reconciled through consideration of sea surface temperature (SST) pattern effects and differences between tropospheric and surface winds. The SST patterns are found to exert a strong influence on the surface winds, acting against the intrinsic large-scale circulation slow-down to produce a near-zero surface wind speed change averaged in space. The intrinsic slow-down and SST pattern effects combine to maintain a muted precipitation response despite the near-zero change in surface wind speed. Because the planetary boundary layer is decoupled from the free troposphere, the surface wind speed change cannot be regarded as an indicator for the trend of the tropical tropospheric circulation. As a result, there is no inconsistency between observed changes in surface winds and future projections of the atmospheric circulation: The total tropospheric circulation, dominated by the zonal wind (e.g., Walker cell), tends to slow down with global warming, while the meridional circulation (i.e. Hadley cell) and total surface winds are by no means predicted to weaken robustly.