In Scotland, downpours bring 50% more rain

"Knowing the change in average rainfall is not enough to understand the change in intense rainfall. In fact changes in variability often have a greater impact on extremes," says Nicholas Watkins. (Credit: * zoute/Flickr)

Researchers looked at 63 years of European rainfall data and found changes in the character of rainfall in many locations. In Scotland, for example, the old adage “it never rains but it pours” has become truer than ever.

“We have found that in many places in Scotland the rain on heavy rainfall days has increased by over 50 percent,” says Sandra Chapman, a professor at the University of Warwick. “However, in some places in the Highlands this rain has shifted from light rain days so overall it’s not much wetter but when it does rain it is more intense.

“In other Scottish locations the change reflects an increase in the total amount of rain and snow overall,” adds Chapman. “We have also found related results across Europe. In southwest France it is drier with less rain on all types of rainy days but in Tuscany it is drier with heavy rainfall in particular being reduced.”

[why most rain falls on the driest soil]

While variability in the way it rains makes it intrinsically difficult to identify the character of local climate change, it’s not impossible, according to Chapman and colleagues, who published their findings in the journal Environmental Research Letters.

“Knowing the change in average rainfall is not enough to understand the change in intense rainfall. In fact changes in variability often have a greater impact on extremes,” says study coauthor Nicholas Watkins from the London School of Economics and the University of Warwick.

“The research demonstrates how rainfall variability—in particular what is known as the ‘long tail’ of rainfall distributions—makes it hard to identify changes just by looking at local observations. Even when we create data where changes are known to exist they can sometimes be impossible to identify because there aren’t many days in a season.

[big storms can make or break politicians]

“So just looking out your window—even if you do it every day and keep a careful log—can create a misleading impression about local climate change,” adds Watkins.

“Our method quantities this uncertainty directly from the observations; we can identify when we know things are changing, when we know things are not changing, and when we know that the data cannot tell us whether things are changing or not.”

Study coauthor David Stainforth from the London School of Economics says the team’s findings demonstrate “how the impacts of climate change are complicated and local. As a consequence it is likely that individuals will have different perspectives on anthropogenic climate change if their views are based mainly on personal experiences of weather rather than on the underlying fundamental science.

“This study, and an earlier related one on temperature differences by the same team, provides a new source of information to support local decisions made in the context of climate change; decisions relating to flood protection, insurance, water provision, agricultural planning, or even just what will grow best in your garden.”

Source: University of Warwick