Human-Caused Global Warming Produces Less Rainfall

Groundhog Day is just around the corner, which means that Punxsutawney Phil will predict whether or not we'll have six more weeks of winter. Our favorite furry mammal may be getting an unexpected helper when it comes to his decision, though: climate change. Climate scientists have announced that they have found evidence to back predictions for a future with lower average rainfall, even though Earth's past warming episodes have led to more precipitation, not less.

During the Medieval Warm Period from 100 to 1250 AD, the Earth received more solar radiation than it does today. This actually caused more rain to fall during that period. However, the late 20^th century saw a huge warming trend that saw less rainfall. The scientists hoped to answer why this was.

The findings, published in the journal Nature, looked at the effect of greenhouse gas emissions on global warming. The team of U.S. and Chinese scientists modeled climate data over the last millennium. They showed that the two causes, greenhouse emissions and solar radiation, induce warming in different regions of the atmosphere, which causes different outcomes for rainfall formation.

When heat-absorbing greenhouse gasses are present in the atmosphere, they cause a narrowing of the usual temperature different between different layers of the atmosphere. This, in turn, causes a more stable atmosphere that's less likely to produce storms or rain. Solar heating alone, on the other hand, will induce an overall higher level of rainfall, explaining the different between the Medieval Warm Period and today.

There are some points to be made about the model that the scientists crafted, though. It estimates the global average for future rainfall rather than local averages. This means that a certain area could potentially see more rainfall than usual, depending on the conditions.

While the model doesn't give a concrete answer about the climate's future, it does provide an explanation for the difference in rainfall seen between the past and today. If we're lucky, though, Punxsutawney Phil will predict six more weeks of winter.