Is March In The Upper Midwest Losing It’s Freeze? The actual data doesn’t seem to support Climate Central’s recent claim.
Guest post by Steven Goddard
Yesterday, WUWT discussed an article on future regional temperature modeling from Heidi Cullen et. al at Climate Central claiming that most of the upper Midwest will no longer be freezing in March by the year 2090 – as a result of increases in atmospheric CO2 content. This was based on averaging the output of 16 different climate models. Here’s the image included in their press release:
Caption: In blue: projected areas with average March temperatures below freezing in the 2010s (above) compared to the 2090s (below), under a high carbon emissions scenario extending current trends. Click image for an interactive map
As you can see below, CO2 has been increasing rather steadily for the last few decades, particularly the last 30 years. No dispute there.
Source: Scripps Trends in Carbon Dioxide
If Climate Central’s press release theory were correct, we would expect to have already seen an increase in March temperatures, and an increase in number of years above freezing. Below is a graph of NCDC March temperatures for Wisconsin since 1979.
The orange line is the mean and the red line is the freezing line. Note that not only is there no trend towards a warmer March, but the standard deviation is high (3.67) and the range is also large – about 15 degrees difference between the warmest and coldest March.
Even so, the 100 year graph of March temperature in Wisconsin seems rather flat also.
The next graph is the number of years above freezing per decade. As you can see, there were fewer years above freezing in the last decade than there were in the 1980s.
Minnesota shows the same patterns – no warming and high variability. The number of years above freezing has also decreased.
And here is the 100 year March temperature graph, like Wisconsin, pretty flat:
Like Wisconsin, it seems there have been less days above freezing in recent decades:
Conclusion: Based on the NCDC data, there is no evidence that increases in CO2 over the last 30 years have affected March temperatures in the north central region of the USA or moved the freeze line north. Once again, we see a case of scientists trusting climate models ahead of reality.
More on Climate Central:
Here is Minnesota and Wisconsin with five different trend lines for different start years.
In order to highlight the lack of correlation between year and March temperature, I also made a scatter diagrams: