Climate change and weather: How are they connected?
By Pam Shaouy
Record-breaking snowy winters. Stronger storms battering coastlines. Severe droughts ending with torrential rains. Extreme weather events have increased over the last few decades and especially over the last few years.
We’ve all heard that global warming can increase the frequency and severity of weather events. But do you know how, why and to what extent? Citizens’ Climate University explored these topics in a recent online presentation with climate researcher Dr. Jennifer Francis and meteorologist Bob Lindmeier. Watch the lesson for yourself, or keep reading for a recap of the key takeaways.
Arctic amplification and anomalies
Dr. Francis, a climate researcher at Rutgers University, is world-renowned for her research on the links between the Arctic and weather events. “The rapidly warming and melting Arctic is affecting weather patterns down here where we all live in mid-latitudes,” she said.
The average global temperature is on the rise. The last three years have been the hottest on record. Our changing climate affects the Arctic in two important ways.
First, the sea ice floating in the Arctic Ocean is becoming thinner. There’s also less ice, so more dark ocean water is exposed. When the sun hits ice, most of that energy is reflected back into outer space. Without the ice, the dark ocean absorbs even more of the sun’s energy. “More of that sun’s energy is entering the climate system, warming the ocean, melting even more ice, and setting up a vicious cycle that we call a positive feedback,” Dr. Francis explained.
Second, the Arctic is warming faster than any other place on our planet. This is called “Arctic amplification.”
The mid-Atlantic jet stream
Imagine a layer of atmosphere over the northern hemisphere. Warm air expands, so the layer is thicker over the mid-latitudes where the air is warmer. Cold air contracts, so the layer is thinner over the Arctic where the air is colder.
A fast-moving stream of air flows down the “hill” from the thicker layer over the mid-latitudes to the thinner layer over the Arctic. The stream turns right and circles the northern hemisphere, flowing west to east. “It becomes what we call the jet stream,” Dr. Francis noted.
But with Arctic amplification, the atmosphere above the Arctic is now warming and thickening faster than over the U.S. This makes the hill the jet stream travels down toward the Arctic less steep, so there’s less force driving the jet stream.
A weaker jet stream tends to swing north and south in bigger waves rather than flow across the northern hemisphere in gentle waves. North of the line is cold air. South of the line is warm air. A big wave and its trough can cause frigid Arctic air to plunge into the deep South.
“When we get these big waves like that in the jet stream, they tend to be quite persistent. They tend to stay in place for a long time,” Dr. Francis said. The result is a “stuck” weather pattern: think of 2015’s long, severe winter in the Northeast, or the years-long drought in California.
Dr. Francis continued, “But the other thing that happens with respect to these waves is the dynamics of the waves themselves.” When the jet stream comes out of the northwest over California, the dynamics favor dry and settled conditions. When the jet stream comes up from the southwest into the northeast, the dynamics favor a wet and stormy pattern. And if it’s cold, that means snow.
If this big atmospheric wave isn’t moving much, you can end up with extreme weather. “Remember when the waves get big, they tend to hang around longer,” Dr. Francis said. “So the weather associated with that big ridge and its trough, if it’s more persistent, is going to make the ‘stuck’ weather patterns that can lead to various kinds of extreme events.”
How bad is it?
Climate models show if we do nothing to curb greenhouse gas emissions, we may lose all the sea ice in the Arctic Ocean between 2040 and the end of the century. But if we curb them, we have the possibility of keeping some ice. “It’s within our power to do something about this,” Dr. Francis said.
A meteorologist’s perspective: Climate and weather connections
Bob Lindmeier, chief meteorologist at WKOW-TV in Madison, Wis., knows it can be challenging for TV weathercasters to report what climate researchers are publishing, but his field and his particular station are both very encouraging.
“Climate change is a subject that The American Meteorological Society really pushes our television broadcasters to communicate about,” Lindmeier said. “I’m fortunate to have a management that is supportive of me going on air and talking about climate change.”
“They want me to keep it relative to events that have recently occurred,” Lindmeier continued. “I have to be very careful when we have an extreme weather event to not immediately attribute that to climate change because we don’t know what percentage of climate change is affecting that particular extreme event. What we can say is this is an example of an extreme event that we’re seeing increase in frequency.”
Climate Central is one of Lindmeier’s most important tools for climate education. “This is a website that’s run by meteorologists, by researchers, all peer reviewed. Anything that I pull out of this website to show on air, I’m confident that it is the real science.”
Lindmeier likes to show how climate change impacts Madison and Wisconsin. When he shows Climate Central graphics about how climate change has already impacted temperatures or weather events locally, it resonates more with his audience than news about polar bears or world events. For example, the graphic to the right shows how dramatically climate change will affect future summers in Madison: by 2100, temperatures could be 11.5 degrees Fahrenheit hotter than today.
Lindmeier also emphasized it’s important and effective to talk to family and friends about climate change. Hopefully with the information you’ve learned here today, you can have more informed conversations about climate and weather, and continue to build political will for climate action.
Every week, Citizens’ Climate University hosts a live, online learning session to educate and empower climate action volunteers. Browse past lessons in CCL Community, and mark your calendar for upcoming sessions.