Wondering About the Weather

Climatologists at the National Climatic Data Center in Asheville analyze weather data to explain the unusual winter of 2013-2014 and to forecast how a warming planet will affect climate in the future.

ASHEVILLE - Everywhere you look around North Carolina, it appears spring may have arrived, finally. The flowers are blooming, the trees are budding, and yes, the breeze is carrying the pollen along.

But after one of the longest and coldest winters the state has experienced in a long time, people are still wondering, “What’s up with the weather?”

The National Oceanic and Atmospheric Administration’s National Climatic Data Center in Asheville reports it was a weather of extremes. Overall, the agency’s data shows it was colder and drier than average. There was heavy snow and intense cold in the north and central parts of the country, which spilled down into North Carolina. All the while, the western part of the nation experienced record-breaking heat and drought.

“The thing about this winter is that it was really unusual compared to recent winters in the 21st century,” said Deke Arndt, Chief of the Climate Monitoring Branch at the National Climatic Data Center. “It was really cold in the east and really snowy in the east, but when you extend that record back, and you compare it to the late 20th century, or the middle of the 20th century, it wasn’t that unusual. We’ve experienced several winters like this in the past.”

It seems we have short-term weather memories. While the past winter was unusual, it wasn’t all that unique when you look back over 30-to-40 years of weather data. And climatologists also say the fact most everyone thought this winter’s weather was so unusual is proof we are getting used to shorter and warmer winters, which come with a slowly warming world.

“And it’s a key thing to know winters are changing in the US and in the northern hemisphere, which is why we don’t experience this type of winter as often as we used to,” adds Arndt.

As the world warms, the long-term climate trend is for winters to be warmer and shorter with summers to be hotter and longer. But climate scientists note the daily weather can still change because hot and cold air still moves around like it used to before the world was warming. That’s why it is important to understand the relationship between the ingredients that drive today’s weather and climate, and that relationship is based on how often those hot and cold ingredients come together. 

“Look at big weather events like a recipe for your favorite cakes or cookies,” explains Arndt. “Certain events have to come together to produce the big heat wave, the violent weather outbreak, the big cold outbreak, and the relationship between climate and those events is that climate informs when those ingredients come together."

Here’s a good analogy.

Imagine a man walking his dog up a hill. The man represents everyone who lives in a town or city, or a state or nation, or even the planet. The dog represents the day-to-day weather. The incline of the hill represents the temperature while the hill itself represents the climate.

As the man and his dog progress up the hill, though the temperature is gradually warming, the dog still wanders back and forth. In other words, the daily weather is changing. Everything is still warming, but the daily weather can change.

Here’s another way to think about the difference between climate and weather. Climate determines what clothes are in your closet and whether you buy a certain coat. Climate is long-term. Weather determines tactical decisions, such as what coat will you wear on a particular day.

But let’s go back to our recent winter weather. Scientists call it an exception. So what type of weather can we expect to see?

In general, winters will be warmer and shorter while summers will be longer and warmer. Scientists say rain and snow events will be different as well.

“The big change in precipitation is not how much, but how the mix will change over time,” said Dr. Thomas Peterson, Principal Scientist, NOAA National Climatic Data Center. Dr. Peterson also shared in the Nobel Prize for his work on the World Meteorological Report on Climate Change. “And we’re already seeing it around the world with the increase in heavy precipitation.”

The increase in precipitation follows logically with climate theory. Think about how a clothes dryer warms the air; warmer air evaporates water more quickly because warm air holds more water vapor. So if there is warmer air hovering over an area, and if warm air has the potential to hold more water vapor, then when something triggers a storm, there’s a chance it could be a heavier precipitation event.

The bottom line: scientists say that as the world warms, we can expect more rain events. That doesn’t mean areas will get additional rain, but the same amount of rain will likely land in heavier concentrations with longer dry spells in between.

A warmer world will also bring more heat events such as extreme droughts. There will also be fewer cold events.

The warmer, wetter atmosphere could also generate more severe storms.

All of this climate projection is based on an analysis of massive amounts of data. The Asheville center collects almost four petabytes, or one million gigabytes, of weather data per year. It is collected from weather stations, airports, weather observers and satellites. That’s enough information to fill 20 million four-drawer filing cabinets per year. Scientists hope people will use the information in planning for a changing climate.

“You have to know where you are to know where you are going, in terms of weather and climate,” explains Timothy Owens, Operations officer, NOAA National Climacic Data Center. "So we get a baseline of conditions each year, and then we project that out with the benefit of models.”

“Adaptation to climate change also adapts us better to our current environment," adds Dr. Peterson. “And adapting to our current environment adapts us better to climate change."

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