Reality Check on Nebraska's Climate

The Associated Press is pushing a story on how “climate change will affect Nebraska ag[riculture],” which is being picked up by a number of outlets (including some that should know better – like the Washington Times).

According to the article, “a University of Nebraska-Lincoln professor is warning that climate change will have drastic long-term effects on agriculture throughout the state.”

Some statements from the piece:

[Professor Don] Wilhite, the lead author of 'Understanding and Assessing Climate Change: Implications for Nebraska,' said climate models predict that the unusually hot and dry summer of 2012 will become the average conditions for Nebraska by the last quarter of this century. The report says the number of days with temperatures above 100 degrees is expected to increase substantially.

Direct from the NOAA National Climatic Data Center, here are the average maximum summertime temperatures for Nebraska since records began in 1895.

There has been no significant trend in Nebraska's maximum summertime temperature since records began 120 years ago.  Nor has there been a significant trend since 1970 (actually, the correlation is toward cooler summer maximum temperatures, not warmer), or over the last three decades.

Summertime precipitation in Nebraska tells the same story.

Absolutely no hint of a significant trend in summertime precipitation for the state since 1895 (in fact, there is almost a perfect non-correlation), nor since 1970 or during the past 30 years.

As for the number of days above 100º F, there is not a single one of the climate sub-regions within the state that has a significant increasing trend in the number of days above 100º F per year over the past century.  Quite the contrary.  The climate sub-regions of Lincoln, Norfolk, and Grand Island have significant declining trends.  On the balance of probabilities, the number of these extreme hot days throughout the state appears to be decreasing during the last 100 years, not increasing, and the 1930s were much hotter than any period since.

Another claim from the Associated Press article:

Heat and increased seasonal variability in precipitation is likely to enhance drought frequency and severity.”

Here is the annual drought severity index for Nebraska since records began.

Not only has there been absolutely no trend since 1895, but the period since the severe droughts of the 1930s and 1950s – which have not been repeated – has seen a trend towards fewer and less severe droughts.

Apparently, “climate change will disrupt agriculture production [in Nebraska] by mid-century, particularly crops and livestock, and degrade soil and water assets because of heavier but less-frequent rains.”  There are no climate sub-regions in the state with a significant increasing trend in the annual number of days with heavy downpours since 1970.  Similarly, no sub-regions show any significant trends over this timeframe towards greater 1-day maximum annual precipitation quantities, either.

Overall, historical climate trends in Nebraska appear to be strongly at odds with the climate predictions in this Associated Press article.