A mechanism for sun-climate connection

Mechanisms by which small changes in the sun's energy output during the solar cycle can cause changes in weather and climate have been a puzzle and the subject of intense research in recent decades. Here we report that differences in surface circulation conditions during solar maximum and minimum periods are caused by differences in the frequencies with which circulation perturbations in the stratosphere reach the surface. A much greater fraction of stratospheric perturbations penetrate to the surface during solar maximum conditions than during minimum conditions. This difference is more striking when the zonal wind direction in the tropics is from the west: no stratospheric signals reach the surface when equatorial 50 hPa winds are from the west under solar minimum conditions, and over 50 percent reach the surface under solar maximum conditions. It has been previously shown that stratospheric circulation perturbations reaching the surface change weather patterns by imposing atmospheric pressure anomalies characteristic of the Arctic oscillation.