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Missouri Already Seeing Climate Change Cause 'Unprecedented' Warming And Precipitation

As the climate warms, extreme precipitation events are becoming more common in Missouri.
Carolina Hidalgo
/
St. Louis Public Radio
As the climate warms, extreme precipitation events are becoming more common in Missouri.

Missouri has experienced some of the warmest and wettest years on record in recent decades, said Pat Guinan, state climatologist and associate professor of climatology at the University of Missouri Extension.

The planet is warming at a dangerously fast rate, according to a landmark report from the United Nations released this month.

Climate change will intensify in the coming decades, bringing higher temperatures, more extreme weather and more wildfires to the U.S. — a dramatic reshaping of our environment undoubtedly driven by human activity, the report finds.

Still, not every region of the country will be affected in the same way.

St. Louis Public Radio’s Shahla Farzan spoke with Pat Guinan, Missouri’s state climatologist and associate professor of climatology at the University of Missouri Extension, about changes that Missouri residents can expect to see in the coming years.

Shahla Farzan: How is climate change affecting Missouri?

Pat Guinan: Since about the late 1990s, we have been in an unprecedented warming trend. There were warm periods in the 1930s and the 1950s. But since 1998, we've only had five years that actually were cooler than average. So nearly 80% of the years since 1998 have averaged above normal.

When you break it down into seasons, most of this warming has been occurring in our winters and our springs. But it's important to note that when you break up temperature, you have to look at maximum and minimum temperatures as well. Minimum temperature, that's where we've seen our strongest warming.

All four seasons, we're seeing that upward trend of warmer minimum temperatures. It's these minimum temperatures that we're seeing some really unusual warming taking place in our changing climate.

Farzan: So temperatures have been getting warmer in Missouri. Have we also seen changes in precipitation?

Guinan: Here in Missouri, we've been in an unprecedented wet period since about the early 1970s. In fact, four out of our top five wettest years have occurred since 1973: 1973, 1993, 2008 and 2015. We're seeing higher extreme events, not only on a daily basis, but when we look at the annual totals, when we look at seasonal totals, it all shows upward trends over the past few decades versus the long-term record. So if you think we've been seeing more extreme precipitation events, more flooding over the past few decades, we have — and the data really back that up.

Farzan: Could you explain what exactly is driving this wet period that we’ve seen over the past few decades in Missouri?

Guinan: One of the contributors is the warming temperatures [that are] allowing more water vapor into the atmosphere. These warming temperatures are occurring in the oceans, and the Gulf of Mexico is the source region for moisture into the middle part of the country.

When we get those southerly winds, it advects that moisture — Gulf of Mexico moisture — into the middle part of the country [and] you get atmospheres that become more efficient at creating precipitation. That's one of the reasons we're seeing this increasing trend of precipitation.

Over the past few decades, we're seeing less triple-digit heat [in Missouri], because there's more water vapor in the atmosphere, which suppresses maximum temperatures. When you have abundant moisture in the soil profile, as well as vegetation that uptakes that moisture through the root system and transpires that into the atmosphere, that's pumping more moisture into the atmosphere. That actually elevates minimum temperatures at night, because the air temperature never goes below the dew point.

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Farzan: Flooding is something that we're pretty accustomed to here in Missouri, but we have had some more extreme flood events. As recent as 2019, we had major floods that came through and devastated our corn and soybean crops. Is major flooding something we should expect to see more of?

Guinan: Indeed, we are seeing more extreme precipitation events. I looked at some of the long-term records from weather stations going back over 100 years. Three inch daily events increased by 35%, if you look at the past 20 years versus the long-term record.

We are indeed seeing more flooding that can be highly impactful on rivers and streams [and] our mainstream rivers. And of course, what happens upstream from the Mississippi and the Missouri River all can have impacts on what happens here in Missouri.

Farzan: What about drought? Is that an issue that's predicted to get worse in Missouri?

Guinan: Unprecedented wetness is what we've experienced here in Missouri over the past few decades, but we also have to recognize that drought has and always will be a part of the climate system. So when we look back at what's happened in Missouri, we've had some horrible drought periods. The 1930s, the Dust Bowl years, the dirty '30s, the 1950s. The mother of all droughts, was a five-consecutive-year period here in Missouri from 1952 to 1956. We really haven't seen a multiyear drought in more than a couple generations, and yet, they will be back.

We are in a warming world, and there are going to be periods like we've seen across the West, where much of the western U.S. is in some form of severe to exceptional drought. What is happening is the human component is another ingredient that is introduced into our climate system that does impact temperature and precipitation patterns.

So when we do have these drought periods, with warmer springs and warmer summers, that's going to put a little extra edge — especially during the growing season when the rains do not come, when vegetation is stressing, and it's not releasing that moisture into the atmosphere.

When these conditions do return, it'll be interesting to see how things compare with what we saw in the 1930s and the 1950s because that's where state records still stand. Our hottest temperature on record in Missouri occurred in July of 1954 in two locations; Union in Franklin County and Warsaw in Benton County reached 118 degrees. That still stands as our highest temperature reached in the state of Missouri.

Follow Shahla on Twitter: @shahlafarzan
Copyright 2021 St. Louis Public Radio. To see more, visit St. Louis Public Radio.

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