This is a follow up to those posts done by guest contributor Steven Goddard.
One of the NWF claims about global warming is that snow in the Colorado mountains is diminishing and has become very erratic, as seen in the NWF graphic at left.
In this article I will show that the claim is incorrect – Colorado snowfall has been generally increasing for the last hundred years and that year over year variability has always been extremely high.
Fortunately, there are excellent long term records of snowfall available from NOAA’s Western Regional Climate Center. I chose the Crested Butte, Colorado station because it is centrally located in the mountains (so is representative of a wide region) and has the most complete and continuous snow record of every month for the past 100 years. I have randomly sampled quite a few other stations in Colorado. None seem to have as a complete a record as Crested Butte, and the pattern described for Crested Butte seems to be fairly consistent in the mountainous regions of the state.
Below are graphs showing annual and monthly snowfall totals (in inches) for Crested Butte since 1909. The trend lines were generated using Google Spreadsheet’s linest() function. Note that every month is trending upwards in snowfall and the standard deviation is very high. Also note that there were several very dry years early in the 20th century with very little snow – and the last few decades have seen more consistent snowfall. Since 1981, every year has received more than 100 inches of snow. Prior to 1930, it was not uncommon to have snow years with less than 100 inches of snow. Prior to 1930, the average annual snowfall was 177 inches. Since 1930, the average annual snowfall has been 200 inches – a 10% increase.
Note – the raw data is incorrect for 1910, 1919, and 1924 due to a significant number of missing measurements, so I substituted a calculated annual value based on the trend line. This probably overestimates the snowfall for 1919 and 1924, and is thus conservative.
Click images below for full-sized ones.
Standard deviation = 67 Mean = 195 Trend = +7.7 inches per decade
Mean = 23.4 Standard Deviation = 15.1
Standard deviation = 25.9 Mean = 33.5
Standard deviation = 27.9 Mean = 38.4
Standard deviation = 19.3 Mean = 33.5
Standard deviation = 18.2 Mean = 31.0
Standard deviation = 13.1 Mean = 16.9
In summary, snowfall is increasing annually and we see upward trends in the months of “snowfall season” in Colorado. Year over year variability has always been very high and may actually be lower in recent years. And, the Colorado mountains no longer have extremely low snow years like they did 80 years ago. By the data, it seems the NWF claims are unfounded.