What was done
The authors studied the distribution of flood flows in the Upper Mississippi, Lower Missouri and Illinois Rivers and their relationships to various climatic indices.

What was learned
Some large and statistically significant upward trends in flood flows were found in certain places along the Mississippi and Missouri Rivers.  However, the authors caution against jumping to conclusions too quickly; for many of the observed trends were highly dependent upon the length of data record and when the trends began and ended.  Hence, they state that "the trends seen today were not necessarily there in the past and they may not be there tomorrow."  They also emphasize that "the future remains unknown, and may eventually contradict the past."  As for causes of the apparent upward mean trend, a number were listed and discussed.  In their own words, however, "the least likely cause of the trend is anthropogenic climate change associated with increased greenhouse gases."

What it means
There are some indications of upward trends in flood flows on certain parts of the Mississippi and Missouri Rivers over the past several decades; but there are many reasons to question what they portend for the future and what may have been responsible for them.  With respect to potential causes, CO2-induced global warming appears on the bottom of the authors' list of possibilities.