In a detailed study in the January 31st issue of the journal Nature, an international team of scientists posited that global warming deriving from greenhouse gasses affects rainfall patterns differently than from solar heating.
The scientists use computer model simulations to demonstrate that rainfall across the earth has increased less over the current warming period than during the Medieval Warming Period – despite the fact that temperatures during this era are far higher.
Scientists utilized an atmosphere-ocean coupled climate model to simulate current and past climate conditions. What they discovered is for every degree rise in the earth’s temperature, the global rainfall rate since the industrial revolution has increased less by approximately 40%.
The difference in heating from greenhouse gasses and solar radiation is due to sea surface temperature. The gradient of sea surface temperature, or SST, across the tropical Pacific weakens when warming is due to increased greenhouse gasses. But solar radiation affects SST differently, and raises the temperature.
The weaker the SST the less rainfall, particularly over the tropics; the greater the SST, the greater the rainfall.
Scientists believe that with future warming from greenhouse gases, the weaker gradient and smaller increase in yearly rainfall will be the norm.