Is US Weather Becoming More Variable?

 

 

 

 

 

 

 

 

 

We are often told that our weather is becoming more unpredictable and extreme. Global Warming will bring more rain to some areas while making other areas drier.

Is there any truth in this?

 

Well, certainly not in the USA. The NCDC fortunately provide comprehensive climatic data, which allows us to check these things out. Consequently, we can look at precipitation records year by year back to 1895 and see them split into  nine separate regions.

http://www.ncdc.noaa.gov/oa/climate/research/cag3/regional.html

I have taken the period 1901-2010 and identified the top 10 driest and top 10 wettest years in each region. The number of such extreme years occurring in each decade are shown below.

 

	WEST	NORTH WEST	SOUTH WEST	WEST NORTH	SOUTH	EAST NORTH	CENTRAL	SOUTH EAST	NORTH EAST	TOTAL
1901-10	3	0	4	1	3	1	1	1	1	15
1911-20	1	0	0	1	2	0	1	0	1	6
1921-30	2	4	2	2	2	1	2	5	1	21
1931-40	2	2	1	4	1	3	3	1	0	17
1941-50	2	3	2	0	3	0	2	2	2	16
1951-60	2	2	3	2	4	2	2	1	1	19
1961-70	0	1	1	0	1	3	1	1	4	12
1971-80	1	1	1	2	1	2	2	2	2	14
1981-90	4	3	4	3	0	4	1	2	2	23
1991-00	2	3	1	3	2	2	3	2	1	19
2001-10	1	1	1	2	1	2	2	3	5	18
TOTAL	20	20	20	20	20	20	20	20	20	180

 

A “normal” decade, of course, would come out with 1.8 extreme years per region, or 16.4 for all nine regions. So clearly the latest decade works out as pretty unexceptional and, furthermore, shows a trend back to “normal” weather after the more volatile decade of the 80’s. The following graph gives a better perspective back to 1901.

 

 

 

The last decade is clearly in line with most of the previous decades of the 20thC. Only the 1910’s and 1960’s had significantly more stable weather.

Global Weirding? Not in the US, at any rate.