Bloomington homes suffered extensive damage from the storm back in June.
(Devan Ridgway / WTIU)
It may not be obvious, but climate change is impacting Indiana weather in multiple ways.
Gabriel Filipelli, professor and executive director of the IU Environmental Resilience Institute, said climate change means storms – like the one that hit Bloomington back in June – leave much more damage.
“Climate change makes all extreme events more extreme,” he said. “It does tend to make a much more dynamic atmosphere, which makes things like the storm that swept through in June that much more destructive.”
Gabriel Filipelli, professor and executive director of the IU Environmental Resilience Institute, said climate change can make storms more extreme and rainy. (Zoom)
Stalled highs and stalled lows cause high pressure systems to last for longer periods of time. This means in the winter, the weather turns colder and dryer, while in the summer, the weather turns hotter and dryer.
Indiana was in the middle of an “Omega block” – a high-pressure area – last month. The phenomenon blocks rain from entering the area and instead moves it north where the pressure is lower. As a result, September was very warm and dry.
On the other hand, if stuck in the middle of a stalled low pressure system, heavy rainfall and flooding can occur. That’s what happened in Missouri and Illinois last summer; when parts of St. Louis received nearly 2 inches of rain in 45 minutes, causing extreme flash flooding. As part of the Midwest, Indiana is vulnerable to similar weather events.
“If that would have occurred over Indianapolis, we would have struggled with neighborhood flooding, a lot of loss of property, a lot of roads flooded out,” he said. “Meaning, emergency service vehicles can't get to where they need to go. If you have to make a 911 call for a heart attack or something, and guess what? They can't actually get to you very easily, or it takes them longer.”
Climate attribution refers to the extent to which outside sources, such as humans, contribute to climate change. One example that fuels climate change is greenhouse gas emissions. Greenhouse gas emissions warm up the atmosphere, which holds more water vapor. This causes hurricanes such as Milton and Helene to bring more rain.
“What we're seeing is that hurricanes are getting wetter and wetter, meaning more and more water up in the atmosphere, so that when they die out over land, they dump all that water onto the land,” he said.
Bloomington received some of the excess rain from Hurricane Helene last month. Wind speeds reached 48 mph, and there were nearly 1.8 inches of rain. About 97,000 people in the state lost power.
Indiana is in the middle of a weather front, a transition zone between two contrasting air masses: warm, moist air from the Gulf of Mexico and cold air from the north. This can cause temperatures to vary wildly in the span of just a day.
This graph shows the average temperature change in Celsius in Indianapolis over time. Average temperatures have slowly been rising. (University of Reading)
“It's this constant play, but unfortunately, or fortunately, Indiana is right in the middle of that boundary,” Filipelli said. “If you don't like the weather, come back later today, because we have pretty variable weather patterns.”
Filipelli said being stuck in the middle of a weather front is warming Bloomington summers by 1 to 2 degrees over the past few years. While the difference may not seem significant, there have been more spikes in temperature. La Nina and El Nino are also contributing to warmer temperatures.
“What we're seeing is that our winter weather tends to get more and more of the tropical air masses than they did before. Before, winter patterns would set up so that we're mainly feeling cold air from Canada,” he said. “Now we're kind of sloshing back and forth between cold air from Canada and then warm air from the Gulf, warm and cold and warm, cold and warm and so on average, that's making winter temperatures relatively warmer than they were before, and incrementally warmer than their summer equivalents.”
La Nina, a climate pattern that is defined by the cooler-than-average sea temperatures in the Pacific, usually pushes colder water to the Americas and warmer toward Asia. It has traditionally resulted in warmer than average fall temperatures for the Ohio Valley in the past; this year is no different. But, Indiana could see above average precipitation in the winter, with potentially more snow. However, La Nina is weak this year, so there might not be any noticeable deviations from the average.
This graph shows the reported temperatures in Bloomington for the entire year of 2024 relative to the average. 2023 saw more significant spikes in temperature compared to the average in February, March and November. (Weather Spark)
This graph shows the reported temperatures in Bloomington for the entire year of 2024 relative to the average. So far this year, compared to the graph of 2023, there are a few more spikes in temperature in August and September. Both 2023 and 2024 experienced spikes in temperature in February and March. (Weather Spark)
“One can increasingly expect winters to have more and more snow-free days, more and more snow-free months,” Filipelli said. “On average, winters are warming up.”
Filipelli said we can curb the effects of climate change by reducing greenhouse gas emissions to the point where they can be absorbed by nature. This is called achieving net zero.
“Once we achieve that, the temperature will stabilize at whatever it is at that point,” he said. “But even with stabilizing whatever the temperature is then, it doesn't mean it's going back to old conditions. That would actually require you to roll back the clock a little bit, pull more carbon out.”
Even if we achieve net zero in Bloomington, for example, Filipelli said the temperature won’t stabilize just here. The entire world needs to achieve net zero in order to stabilize the temperature.
“Unfortunately, our atmosphere is global, so it [temperature] won't stabilize,” he said. “It would be great if it were that easy.”
