US Precipitation Becoming Less Extreme, Not More
By Paul Homewood
I mentioned this NOAA graph earlier. They define it thus:
The percentage areas of the contiguous United States are computed based on the U.S. Climate Divisional Dataset. Those climate divisions having the monthly average temperature/total precipitation in the top ten percent (> 90th percentile) of their historical distribution are very warm/wet and those in the bottom ten percent (< 10th percentile) are very cold/dry.
To try and tidy up their presentation, I have downloaded their data and worked out 12-month running averages:
As I mentioned before, looking at national numbers can cover up a host of sins. For instance, record breaking droughts in the West could be cancelled out by floods in the East, leaving National figures looking average.
The beauty of NOAA’s approach is that it splits out the wet and dry by area.
There is no surprise to see that the percentage of very dry areas has been well down in recent years, even in 2015 despite the drought in California.
What is more interesting though is the very wet graph. There is no evidence at all of any increase in the last 30 years or so, and peaks are not getting higher. Indeed, the index actually peaks in 1941.
We care often told climate change means that extremes of dryness and wetness will grow . In the US, at least, the very opposite is true.