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What's 'Normal' Weather Now? It's Time to Redefine It: WMO

By Terrell Johnson
Published: July 11, 2014

Mark Wilson/Getty Images

A surfer rides a large wave caused by Hurricane Arthur on July 4, 2014, in Avalon, North Carolina. The storm caused widespread power outages, flooding and damage across the Outer Banks over the 4th of July holiday weekend.

Rising greenhouse gas emissions are changing Earth's climate faster than at any time in human history, so the yardsticks we use to gauge what a "normal" climate is will have to change too, the World Meteorological Organization said this week.

In a news release titled "Scientists Urge More Frequent Updates of 30-Year Climate Baselines to Keep Pace With Rapid Climate Change," the United Nations-sponsored agency said that in 2014, the 30-year period most often used as the baseline for "climate normals" -- 1961 to 1990 -- is no longer a useful guide for today's climate.

These climate normals are made up of temperature, precipitation and other climate data, and used by climatologists and meteorologists to put current events in context at local, national and global levels. They help us determine, for example, how extreme the latest drought, heatwave or hurricane is, compared to recent history.

But these baselines are updated only once every 30 years, the WMO explains, and in today's fast-changing climate, that's not nearly fast enough. "As a result, decision-makers in climate-sensitive industries may be basing important decisions on information that may be out of date," the WMO adds in the news release.

The WMO urges national weather services around the world to begin using the 1981-2010 baseline for services like forecasting peak energy demand times and for recommending crop planting times.

While many -- including the U.S. National Weather Service -- already do, not having a global standard means that "different researchers and weather services are using different baselines, which results in inconsistent comparisons," the WMO adds.

That's why the later, 1981-2010 baseline should be adopted by weather services in all nations, and it should be updated far more frequently, the WMO says -- every 10 years rather than every 30 years.

"Today’s increasingly powerful computers and climate data management systems now make it much easier to conduct more frequent updates, which involve analyzing massive amounts of climate data," the WMO said in the news release. "Another advantage of decadal updates is that they will make it possible to incorporate data from newly established weather stations into the normals more rapidly."

Read the full story at the World Meteorological Organization.

 

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