Growing Season Length Isn't Increasing in the Lake Michigan Basin

A recent study by the USGS, which is receiving media attention, predicts the following:

One effect of increasing air temperature as a result of the changing climate was the appreciable increase in the length of the growing season in the Lake Michigan Basin. The increase in growing season will cause an increase in evapotranspiration across the Lake Michigan Basin, which will directly affect soil moisture and late growing season streamflows.

There is a problem that should cast some doubt on the likelihood of these predictions coming true: the length of the growing season is not increasing in the Lake Michigan Basin.

Among the 11 NOAA National Weather Service climate regions in the Lake Michigan Basin area, only one has a significant increasing trend in the growing season length over the last three decades – balanced out by another region that has a significant declining trend.  The other nine regions have no significant trends since 1985.

These climate regions all have growing season length data that goes back at least a century, and often well into the 19th century.  Since records began more than 100 years ago, six of the 11 regions have significant declining trends in the growing season length, while three have no significant trends, and two regions have increasing trends.

But when we look at the two regions with increasing trends, the alarmism falls even further apart.  For the Lansing area, all of the increase in growing season length occurred between the 1860s and the first decade of the 20th century.  Since 1910, there has been no significant trend – actually, the correlation is negative toward a decreasing growing season length.

In the Houghton Lake area, we see a similar story.  All of the increase in the growing season length took place between 1913 and 1960.  Since 1960, there has been no significant trend (with a negative correlation), and over the last three decades a declining trend toward a much shorter growing season has emerged.

In the Sault Ste. Marie region, the increasing trend during the last 30 years has just managed to offset the declining trend that existed from the 1930s through the early 1980s – meaning that overall, there has been no trend since records began in 1889.

Good luck explaining these trends within the context of anthropogenic global warming theory, whereby 55 percent of the climate regions have significant trends toward shorter growing seasons since records began, 27 percent have no significant trends, and of the 18 percent with significant increasing trends, these have trend profiles whereby all the increase in the growing season length occurred before the vast majority of man-made greenhouse gases were released.

The clear conclusion from the historical data in this region is that the growing season has gotten much shorter – not longer – in the Lake Michigan Basin since records began in the late 1800s and early 1900s, and over the last 30 years there does not appear to be any evidence that the growing season is getting longer.

These fundamental inconsistencies between historical trends and where the climate models have the region headed should raise serious questions as to whether the models are reliable, and they should have been explicitly discussed at length in both the USGS report and the media articles about the study.

A recent study by the USGS, which is receiving media attention, predicts the following:

One effect of increasing air temperature as a result of the changing climate was the appreciable increase in the length of the growing season in the Lake Michigan Basin. The increase in growing season will cause an increase in evapotranspiration across the Lake Michigan Basin, which will directly affect soil moisture and late growing season streamflows.

There is a problem that should cast some doubt on the likelihood of these predictions coming true: the length of the growing season is not increasing in the Lake Michigan Basin.

Among the 11 NOAA National Weather Service climate regions in the Lake Michigan Basin area, only one has a significant increasing trend in the growing season length over the last three decades – balanced out by another region that has a significant declining trend.  The other nine regions have no significant trends since 1985.

These climate regions all have growing season length data that goes back at least a century, and often well into the 19th century.  Since records began more than 100 years ago, six of the 11 regions have significant declining trends in the growing season length, while three have no significant trends, and two regions have increasing trends.

But when we look at the two regions with increasing trends, the alarmism falls even further apart.  For the Lansing area, all of the increase in growing season length occurred between the 1860s and the first decade of the 20th century.  Since 1910, there has been no significant trend – actually, the correlation is negative toward a decreasing growing season length.

In the Houghton Lake area, we see a similar story.  All of the increase in the growing season length took place between 1913 and 1960.  Since 1960, there has been no significant trend (with a negative correlation), and over the last three decades a declining trend toward a much shorter growing season has emerged.

In the Sault Ste. Marie region, the increasing trend during the last 30 years has just managed to offset the declining trend that existed from the 1930s through the early 1980s – meaning that overall, there has been no trend since records began in 1889.

Good luck explaining these trends within the context of anthropogenic global warming theory, whereby 55 percent of the climate regions have significant trends toward shorter growing seasons since records began, 27 percent have no significant trends, and of the 18 percent with significant increasing trends, these have trend profiles whereby all the increase in the growing season length occurred before the vast majority of man-made greenhouse gases were released.

The clear conclusion from the historical data in this region is that the growing season has gotten much shorter – not longer – in the Lake Michigan Basin since records began in the late 1800s and early 1900s, and over the last 30 years there does not appear to be any evidence that the growing season is getting longer.

These fundamental inconsistencies between historical trends and where the climate models have the region headed should raise serious questions as to whether the models are reliable, and they should have been explicitly discussed at length in both the USGS report and the media articles about the study.