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Floodwaters surround a flood gauge just west of Hamburg, Iowa, on Wednesday, May 29.

An audible murmur ran through the crowd when images of flooding in Hamburg and the Glenwood, Iowa, area flashed on the screen.

They’d come to Creighton University on Sunday to hear noted climate scientist James Hansen speak about global warming, but in the back of so many minds was that climate change isn’t about polar bears and sea level rise. The consequences can be felt in the heart of a continent, too.

More extreme weather is one of the three most destructive effects of climate change, Hansen told the crowd. The two others are sea level rise and species extinction.

Taken by themselves, floods such as those that occurred in March in Nebraska and Iowa don’t prove much, he said, but a look at weather globally does. “There is an increased frequency of climate extremes, which is not natural,” he said with the slide as his backdrop. “People around here should recognize climate extremes.”

An Iowa native and former director of the NASA Goddard Institute for Space Studies, Hansen has been credited with bringing global warming to the national consciousness during testimony before Congress in 1988.

Global warming is amping up the worst kinds of weather, from greater heat and drought to more intense storms and heavier precipitation.

“The 100-year flood now occurs more than once a century, and don’t be surprised by a 500-year flood,” he said.

“Dry places (like the Middle East and U.S. Southwest) become drier, wet places (like Southeast Asia) become wetter,” he said. “At a place that is sometimes wet and dry (like Nebraska), those extremes tend to get greater.”