Better late than never, we got a little bit busy this week.
Image above from data supplied by Dr. John Christy and rendered by the San Francisco Chronicle from their story here. An excerpt:
John Christy, the Alabama state climatologist who authored the study, said the amount of snow in the mountains has not decreased in the past 50 years, a period when greenhouse gases were supposed to have increased the effects of global warming.
The heaping piles of snow that fell in the Sierra last winter and the paltry amounts this year fall within the realm of normal weather variability, he concluded.
“The dramatic claims about snow disappearing in the Sierra just are not verified,” said Christy, a climate change skeptic and director of the Earth System Science Center at the University of Alabama in Huntsville. “It looks like you’re going to have snow for the foreseeable future.”
Here’s the Press release from UAH:
HUNTSVILLE, Ala. (Feb. 14, 2012) — During some winters a significant amount of snow falls on parts of California. During other winters — like this one (so far) — there is much less snow. But more than 130 years of snow data show that over time snowfall in California is neither increasing nor decreasing.
The analysis of snowfall data from as far back as 1878 found no long-term trend in how much snow falls in the state, especially in the critical western slope of the Sierra Nevada mountains, said John Christy, director of the Earth System Science Center at The University of Alabama in Huntsville.
“There isn’t a trend significantly different from zero for the whole period,” Christy said. “I also looked at just the past 50 years and there is no trend over this recent stretch either.”
Details of Christy’s research have been accepted for publication and released on-line by the American Meteorological Society’s “Journal of Hydrometeorology.”*
This line of research was spurred by recent concerns that snow in the Sierra Nevada mountains had decreased in recent years, perhaps due to man-made climate change, Christy said. Those worries, however, were not supported by credible, long-term data.
A native of Fresno, Christy wondered if the snow he remembered covering the Sierra Nevada’s peaks is actually disappearing. His preliminary investigation found a potentially useful set of data: Records of snow measurements at stations along the Southern Pacific Railroad.
“They took great care to measure snowfall because they had to know how much snow fell before sending trains through the mountain passes,” Christy said. “No one else had looked at this data in detail. The records are pretty thorough and the measuring tools — a device resembling a tall, sturdy yardstick — are easy to use and obviously don’t need power, so there aren’t many gaps in the record.”
There was, however, one catch: “They were good at measuring snow but the data they collected in written records had never been keyed in into a computer dataset. Before I could do the analysis I had to manually input 100,000 station-months of data.”
The railroad data was coupled with data from other sources, including hydro-power and regional water systems vitally interested in knowing how much water would be available from snow melt. Other data was collected from logging and mining companies, as well as National Weather Service stations and volunteers. That data had already been digitized by the National Climatic Data Center.
Christy divided the state into 18 regions, based on the amount of snow that falls and on the quality of the records for that region.
“There are six or seven regions with good, robust data going back to the late 1800s,” he said. “In each of those there are five to 15 stations with good records.”
Global warming theory says rising temperatures might reduce snowfall in some areas, while snow might increase in others. That sounds counterintuitive, but it does make sense: At lower, warmer elevations rising temperatures raise the altitude of the snow line, potentially reducing snow fall at lower elevations.
Warmer air also can hold more water vapor than cold air, so rising temperatures should increase the amount of water vapor available for snow and other precipitation.
In high elevation mountain regions where winter temperatures would be below freezing even if they rise two or three degrees, snow would still fall. Those still-cold temperatures combined with the extra water vapor suspended in the warmer air could increase snowfall at higher altitudes.
That’s the theory.
Looking at both the 130-year record and the most recent 50-year record — which includes the 1975 to 2000 period when global temperatures rose — the California data show no long-term changes in snowfall in any region.
“California has huge year-to-year variations and that’s expected to continue,” said Christy, a graduate of Fresno State University. “California is having a snow drought so far this winter, while last year the state had much heavier than normal snowfall. But over the long term, there just isn’t a trend up or down.
“Not to be a scaremonger, but if you go back and look at the paleoclimate reconstructions for the past thousand years, there have been some colossal droughts lasting 50 years or more,” he said. “Those have not been around since the 1400s, although nothing we know about climate science says they can’t come back — global warming or not.”
In earlier research, Christy also showed no long-term warming in the Sierra Nevada mountains.
— 30 —
Here’s the paper:
Searching for information in 133 years of California snowfall observations
| Abstract |
|---|
Monthly snowfall totals from over 500 stations in California, some of which date back to 1878, are examined. Most data were accessed through the NOAA archive, but several thousand station-months of data were separately keyed-in from image files of original documents. Over 26,000 of these entries were new relative to the NOAA archive, generally providing data prior to 1920.
The stations were then subdivided into 18 regions for the construction of representative time series of each area. There were problems with the basic data, the most difficult with which to deal was the increasing presence of “zero” totals which should have been recorded as “missing.” This and other issues reduce the confidence that the regional time series are representative of true variations and trends, especially for regions with few systematically reporting stations. Interpreting linear trends on time series with infrequent large anomalies of one sign (i.e. heavy snowfall years) and unresolved data issues should be done with caution. For those regions characterized by consistent monitoring and with the most robust statistical reproducibility, we find no statistically significant trends in their periods-of-record (up to 133 years) nor in the most recent 50 years. This result encompasses the main snowfall region of the western slope of the Sierra Nevada Mountains.
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Klas says:
February 18, 2012 at 3:27 am
Unless, of course, your assumption is incorrect and there has been NO meaningful warming–at least not enough to impact the evaporation/precipitation balance (the SIerras being a typical example, albeit not a compilation of all snow-accumulating areas).
For several years (at the minimum) we here in Reno, NV, at the eastern edge of the Sierra, have been constantly bombarded with cries of impending doom when it will snow no more.
Endless story after story in the local rags are meant to scare us into believing that CO2 is dooming the Sierra with drought and will kill all its creatures. Never mind that the Great Basin region periodically endures decade long droughts with some regularity,,,, and we’re enjoying a period of non-drought at the moment. (see tree stumps at the bottom of Lake Tahoe for clarification).
If this dry/no snow doom and gloom is true, why then are the ski resorts preparing to spend millionns and millions of dollars on improvements, including new chair lifts, restaurants, and lodging facilities??? It’s because the resort owners aren’t swallowing this drivel. What do they know that we don’t?
The latest exercise is to convince the Olympic powers that be to bring the Winter Games to Tahoe in 2022. Why on earth would they propose that if……SNOW IN THE SIERRA WILL BE A THING OF THE PAST???
http://www.renotahoewintergames.org/
Camburn,
take a look at this:
http://wattsupwiththat.com/2009/12/19/wikibullies-at-work-the-national-post-exposes-broad-trust-issues-over-wikipedia-climate-information/
“Warmer air also can hold more water vapor than cold air, so rising temperatures should increase the amount of water vapor available for snow and other precipitation.”
The above is taken from paragraph 13 of Mr Christy’s writings and I think it may be a mistake, at least according to http://www.ems.psu.edu/~fraser/Bad/BadClouds.hmtl.
I would just like to know that what I read is correct.
Keep up the good work Anthony.
Steven L. Schwab says:
February 18, 2012 at 3:43 am
Steven,
Those reading here do not have unlimited time. Therefore, we much appreciate comments that make sense.
The material in this post was authored by John Christy, the Alabama state climatologist. It is doubtful that the Great State of Alabama reimburses him on an article by article basis.
What “the tune of 90,000/year” means is a mystery. Do you mean dollars per year – not tunes? Thought so. So then, just who’s earning that amount of money? Here’s an example. About 10 years ago a small amount of money was available at the university where my wife taught. She filled out a request form and a $300 digital storage device was purchased by the computer science department in whose classrooms she taught. Do you think she should have claimed that $300 as personal income on a regular basis, year after year? Is she now $3,000 richer? Not even the IRS would buy into your shrill screed.
So, for your comment you are awarded the Shrill Screed Award.
Wear it proudly:
Steven L. Schwab, Shrill Screed
Woodshedder says:
February 18, 2012 at 10:29 am
Again OT………thank you for the link. All i can say is…..what qualifications would allow Mr. Connollay to be a site admistrator? It is most obvious from his posts on WUWT that he knows very little about climate and its interactions, workings etc. Do they just let any old person be a censur per se at Wiki?
How very disappointing!!!!!!
William M. Connolley says:
February 18, 2012 at 9:09 am
Including the ocean temperatures?
True enough. The ocean temperatures did increase along with the air over the last 100 years as we came out of the LIA, but they also have not risen over the last 15 years. And am I correct in assuming that if we get to17 years of no change that CAGW will be over?
See:
http://www.woodfortrees.org/plot/hadsst2gl/from:1995/plot/hadsst2gl/from:1997.08/trend
Camburn> Actually, when taken on a clmatic scale of a century, the temps of the USA have been flat.
You seem to have made that up. Notice that I gave you a link to actual data, and you just provided words, which you didn’t bother check? It isn’t that hard to do, e.g. http://epa.gov/climatechange/science/recenttc.html shows that you’re wrong.
> Wikipedia. I have tried to correct blatant errors on that site
Well, if you tried to insert the falsehood you’ve used here, I’d hope that it was removed. Feel free to tell us what page you updated, and with what, then we can all judge whether you were correctly reverted or not.
> http://wattsupwiththat.com/2009/12/19/wikibullies-at-work-the-national-post-exposes-broad-trust-issues-over-wikipedia-climate-information/
I’m glad you bring that up. Its rubbish.
> “Warmer air also can hold more water vapor than cold air”
It is a regrettable way to state it (your link, corrected). Air doesn’t “hold” water vapour. But (for the level of discussion we’re having here) its close enough. BadClouds.html will explain the fine details, if you care.
Insofar as this is a posting about snowfall in the westeren US, I might note the on-going snow event in the Cascades of Washington State:
NATIONAL WEATHER SERVICE SEATTLE WA
900 AM PST SAT FEB 18 2012
…AND HEAVY SNOW IN THE MOUNTAINS. THE SNOW IS SOMEWHAT HEAVIER THAN EARLIER FORECAST…WITH 20 INCHES SO FAR AT HURRICANE RIDGE IN THE OLYMPICS…18 INCHES AT MOUNT BAKER…AND A FOOT OR SO IN THE PASSES AND AT PARADISE. HAVE ALREADY UPGRADED TO A WARNING FOR THE OLYMPICS. IT LOOKS LIKE THIS STORM WILL BE ONE OF THE BIGGEST SNOW PRODUCERS OF THE WINTER.
The NPS, here:
http://www.nps.gov/mora/photosmultimedia/east-webcam.htm
. . . has a list of web cams – orange text. The link is to the “East” camera and it brings up a postage stamp size photo. Then you have to click on the “View Webcam” [orange text in the box] to get the current view. An updated photo comes in every few minutes.
Klas says: February 18, 2012 at 3:27 am
Warming causes more moisture in the air which leads to more extreme precipitation events. This includes more heavy snowstorms in regions where snowfall conditions are favourable.
——————————————————————–
Not according to AGW scientist David Vitner it doesn’t. Independent Newspaper, UK – “snow a thing of the past”.
http://www.independent.co.uk/environment/snowfalls-are-now-just-a-thing-of-the-past-724017.html
Global Warming causes less snow – unless it is snowing heavily and then it apparently causes more snow. Now we all experienced this ‘heads we win, tails you lose’ trick, but most of us left it behind in the playground. It looks like the AGW crowd are simply big kids that have never grown up.
.
For the record, here is a link to William M. Connolley’s deletion log on Wikipedia. It appears that he lost some admin privileges in 2009.
http://en.wikipedia.org/w/index.php?title=Special:Log&limit=500&type=delete&user=William+M.+Connolley&hide_review_log=0&month=&year=
Now, somewhat off topic;
DJ: That would a terrific choice for hosting the Winter Olympics, only it is too logical for the Oly. committee members. But, I wish Reno and Tahoe communities the best of luck in their efforts! They could probably run the luge slide all the way to Sacremento; now that would be some ride!
Back on topic:
Really!? Show us any references to that official prediction that predate the recent years of record snowfall. CAGW climate predictions have consistently been adjusted to match after record events ocurred; with the possible exception of higher temperatures, and there are darn few of them. Records that beat all previous recorded weather events are darn few.
Good catch R. Barker! What I want to know, does this mean they’re going to redefine “amateur” so they can keep out these records or do they plan to trash all manually collected records in their rush to censor science?
Excellent article Dr. Christy!! In my career, I’ve occasionally had to input thousands of data entries. My mind boggles, and my hand cramps, at the thought of entering 100,000 data points and then my eyes cross and water at the thought of double checking them. You’ve been verry busy!
William M. Connolley says:
February 18, 2012 at 10:58 am
Thank you for your generous offer to correct Wiki. I have sent you an e-mail and look forward to your reply.
> Global Warming causes less snow – unless it is snowing heavily and then it apparently causes more snow
Sort of. Its a bit more complicated than that, if you’re actually interested:
1. GW makes the world warmer; and this (to first order) makes for more WV and hence more precipitation.
2. In areas well below zero, the snow remains snow, even if it warms. But with more WV, there is more precipitation, hence more snow.
3. In areas near zero oC, some of the precipitation becomes rain now snow, so there is less snow (and some of the snow on the ground melts, obviously).
This, roughly, is why Greenland loses mass under moderate GW but Antarctica gains.
That is all to first order. There will, obviously enough, be areas where moisture decreases not increases.
William M. Connolley says:
February 18, 2012 at 10:58 am
a link to actual data,
My mother was born in the year where the blue curve is at a minimum, while I was born at the peak of the blue curve in the 1940s. As she bundled us up in layers of clothing and mittens and shoved us out the door into the snow and cold, she would say “Quite complaining. It was much colder and snowier when I was a kid.” She often would hold her hand at her waist and tell us how she had to walk 2 miles to 1st grade in snow so deep – all uphill. Both true. Then she would tell us it was uphill on the way home, too. My older sister would then say that Mom’s waist wasn’t as high at age 6 as at age 40 and the part of the story about “up-hill both ways” was a fabrication. That made a skeptic out of me.
Thanks, though, for upholding mom’s argument — She was spot on about that temperature difference.
there was a clear trend of lower minimums during the warming from ca 1910 to 1940 and a clear trend of higher minima during the warming from ca 1977 to 2007. Clearly warming from CO2 affects snaowfall differently than warming from unknown causes.
Adam Gallon says:
February 18, 2012 at 3:48 am
It’d be interesting to compare this graph, to one of temps in the area.
______
A big mistake that is made is thinking that local conditions in California have a high degree of influence as the cause of high or low snowfall years. Much greater correlation is found in temperatures of the Pacific Ocean in regions many thousands of miles away in the central and western pacific. It is here that moisture either is or isn’t picked up by storm systems and brought to California. Those same warm areas of the Pacific, far from California, also have a high degree of correlation with the jet stream tracks which will dictate the path of storms as the come in, or don’t come in from the Pacific. This year, for example, California has seen less snow but Alaska has gotten dumped on. All of that moisture (what CA didn’t get and AK did) would come, or did come from the Pacific. The jet stream brought that moisture to Alaska and California has been largely dry so far.
The fearsome Connolley is among us! All hail the Infallible One, for his Truth is the Only Truth, and when he stamps his foot and plants his staff majestically in front of himself and says, “NONE shall pass!”, he really means it, smiting all the Skeptical Balrogs into non-existence with his Wikipedia Eraser of Doom! Go Connolley! Smite them with your fantastic knowledge of unknown forcings and missing heat signatures – crush them with your solid understanding of how little is known about clouds and feedback mechanisms! Frighten them with End of the World scenarios and keep deleting all dissent – that’s the best way to force the non-believers into submission! That’s Post-Modern Science at its finest – emotion trumps truth while empirical measurements languish, forgotten…
Dr. Roy
Here is a source from the eastern slopes of the Sierras that goes back to 1968. I entered this into an excel spreadsheet for my own entertainment a year ago and no trend there either.
http://www.mammothmountain.com/MyMammoth/#mountainConditions
Oh OH……One might expect more snowfall in the near future. I was looking at temperatures, and this surprised me.
We are colder now than in 1945……
http://woodfortrees.org/plot/hadcrut3vgl/from:1945/to:2012/magnitude:2
If global warming does increase snowfall, and snowfall feeds glaciers. Then glaciers should be getting larger/thicker as a result of global warming – certainly in their upper reaches. But apparently they are decreasing – and this too is due to global warming. I’m getting confused.
A – Just ignore it.
B – Interesting that you choose your start year in the deepest part of a cooling so strong that there was concern at the time that it was the start of the next ice age. It’s also a very different time period from the original piece, which starts in 1880.
C – The ocean temperature measurements were so sparse before ARGO that ascribing any warming or cooling to the oceans is nothing but guesswork (and I’m being kind in using that term). The atmospheric temperatures above the oceans is guesswork before satellites. In any case, the original post was about the Sierras. As I pointed out earlier, the lack of change in snowfall in the Sierras means that either the temperature – snowfall theory is wrong or the temperatures that affect the snowfall in the Sierras hasn’t changed.
> We are colder now than in 1945
I’m surprised to see you say that; the plot you link to doesn’t show it, and the saem plot with the trend added indicates that it is warmer now.
> you choose your start year
Check the source. I just posted what was available. Feel free to do your research and find a contrary trend, if you can.
> ocean temperature measurements were so sparse before ARGO
You’ve made that up.
> Then glaciers should be getting larger/thicker as a result of global warming – certainly in their upper reaches. But apparently they are decreasing – and this too is due to global warming. I’m getting confused.
Yes, I think you are. You could try reading some science, it might help.
Dr. Christy: Thank you for your effort in bringing old records to light. There is another set of California records going back to 1769 that you might consider, related to the “Lynch Index” that was in the California Weather Sumary CD. Jim Goodridge sent me a California Weather CD in 2002 that contained the file “Lynch Index.xls” that tabulates Southern California rainfall from 1769-1770 to 1999-2000. The CA Weather CD updated to 2009 does not appear to have that file. The state climatologist at http://www.water.ca.gov/floodmgmt/hafoo/csc/ might provide some information.
The Lynch Index was based on the August 1931 report, “Rainfall and Stream Run-Off in Southern California Since 1769” by H. B. Lynch, for the Metropolitan Water District of Southern California. The report is available on-line at http://cepsym.info/history/RainfallStreamRunoffSoCA_since1769.pdf
and
http://books.google.com/books/about/Rainfall_and_stream_run_off_in_Southern.html?id=sJMJAQAAIAAJ
The Lynch Index spreadsheet correlates the index from the 1931 report with the rainfall record for Los Angeles. The index stops at 1930, and DWR did an extension to 2000. I did a linear regression analysis on the data, and also an extension (ref Bedient & Huber) of the data to present. Slopes of the regression lines are close to zero.
Moderators: The following text is verbatim from the spreadsheet. Truncate if it does not fit within your format and perhaps I can provide the information another way.
Thank you.
6.698624097
Lynch Year LA Rain Los Angeles
155 1770 23.14 1
125 1771 18.66 2
145 1772 21.65 3
110 1773 16.42 4
115 1774 17.17 5
90 1775 13.44 6
135 1776 20.15 7
75 1777 11.20 8
75 1778 11.20 9
125 1779 18.66 10
135 1780 20.15 11
125 1781 18.66 12
55 1782 8.21 13
65 1783 9.70 14
115 1784 17.17 15
110 1785 16.42 16
75 1786 11.20 17
90 1787 13.44 18
75 1788 11.20 19
135 1789 20.15 20
10 1790 1.49 21
90 1791 13.44 22 0.318
115 1792 17.17 23 0.338
85 1793 12.69 24 0.339
65 1794 9.70 25 0.342
65 1795 9.70 26 0.345
95 1796 14.18 27 0.347
65 1797 9.70 28 0.348
55 1798 8.21 29 0.350
115 1799 17.17 30 0.352
85 1800 12.69 31 0.355
95 1801 14.18 32 0.361
73 1802 10.90 33 0.397
80 1803 11.94 34 0.410
125 1804 18.66 35 0.407
75 1805 11.20 36 0.405
125 1806 18.66 37 0.422
65 1807 9.70 38 0.426
75 1808 11.20 39 0.432
65 1809 9.70 40 0.443
115 1810 17.17 41 0.448
155 1811 23.14 42 0.446
110 1812 16.42 43 0.416
85 1813 12.69 44 0.415
110 1814 16.42 45 0.415
195 1815 29.11 0.414
85 1816 12.69 0.410
155 1817 23.14 0.426
135 1818 20.15 0.441
135 1819 20.15 0.435
85 1820 12.69 0.432
145 1821 21.65 0.446
65 1822 9.70 0.450
65 1823 9.70 0.455
65 1824 9.70 0.450
220 1825 32.84 0.446
45 1826 6.72 0.451
65 1827 9.70 0.447
75 1828 11.20 0.456
35 1829 5.22 0.450
75 1830 11.20 0.444
55 1831 8.21 0.438
45 1832 6.72 0.438
165 1833 24.63 0.438
120 1834 17.91 0.452
110 1835 16.42 0.452
105 1836 15.67 0.459
95 1837 14.18 0.444
100 1838 14.93 0.443
145 1839 21.65 0.467
210 1840 31.35 0.482
40 1841 5.97 0.493
145 1842 21.65 0.491
65 1843 9.70 0.490
45 1844 6.72 0.483
65 1845 9.70 0.477
70 1846 10.45 0.470
135 1847 20.15 0.452
110 1848 16.42 0.450
75 1849 11.20 0.448
135 1850 20.15 0.444
60 1851 8.96 0.432
95 1852 14.18 0.427
125 1853 18.66 0.424
100 1854 14.93 0.428
120 1855 17.91 0.424
85 1856 12.69 0.429
45 1857 6.72 0.429
85 1858 12.69 0.431
65 1859 9.70 0.436
125 1860 18.66 0.439
90 1861 13.44 0.480
220 1862 32.84 0.472
40 1863 5.97 0.458
50 1864 7.46 0.459
95 1865 14.18 0.453
110 1866 16.42 0.439
135 1867 20.15 0.455
140 1868 20.90 0.451
110 1869 16.42 0.456
55 1870 8.21 0.461
50 1871 7.46 0.468
75 1872 11.20 0.469
80 1873 14.84 0.470
129 1874 23.78 0.468
92 1875 18.93 0.482
143 1876 26.07 0.498
38 1877 5.54 0.510
124 1878 21.26 0.507
54 1879 11.35 0.499
118 1880 20.34 0.495
71 1881 13.13 0.497
69 1882 10.40 0.497
68 1883 12.11 0.494
240 1884 38.18 0.475
61 1885 9.21 0.462
147 1886 22.76 0.449
90 1887 13.82 0.451
118 1888 13.76 0.450
134 1889 19.78 0.457
206 1890 34.32 0.460
109 1891 13.33 0.462
79 1892 11.80 0.451
158 1893 26.27 0.438
49 1894 7.47 0.434
123 1895 15.37 0.434
62 1896 8.54 0.441
119 1897 16.83 0.447
50 1898 7.15 0.442
41 1899 5.51 0.424
64 1900 7.90 0.431
117 1901 16.41 0.442
72 1902 10.48 0.452
137 1903 19.75 0.450
61 1904 8.74 0.443
137 1905 19.07 0.447
134 1906 18.75 0.398
152 1907 19.20 0.394
88 1908 13.02 0.391
140 1909 17.92 0.390
95 1910 12.64 0.392
121 1911 17.36 0.391
82 1912 10.37 0.345
81 1913 13.45 0.346
163 1914 23.63 0.351
120 1915 17.04 0.342
131 1916 20.69 0.332
100 1917 14.49 0.333
92 1918 14.53 0.377
66 1919 9.20 0.381
97 1920 11.27 0.369
103 1921 14.23 0.350
150 1922 19.04 0.344
72 1923 10.14 0.349
53 1924 6.12 0.345
64 1925 7.94 0.358
115 1926 17.56 0.361
119 1927 17.76 0.366
69 1928 9.77 0.378
76 1929 12.98 0.391
82 1930 11.21 0.395
1931 12.78 0.397
1932 16.83 0.397
1933 11.75 0.397
1934 14.68 0.397
1935 21.63 0.400
1936 12.02 0.410
1937 22.35 0.418
1938 23.44 0.432
1939 18.74 0.434
1940 13.54 0.438
1941 35.60 0.443
1942 11.80 0.439
1943 19.65 0.439
1944 18.78 0.442
1945 10.87 0.436
1946 11.07 0.434
1947 13.08 0.434
1948 7.00 0.438
1949 7.73 0.450
1950 10.65 0.444
1951 7.47 0.442
1952 26.98 0.439
1953 9.76 0.443
1954 13.07 0.447
1955 12.79 0.462
1956 18.17 0.461
1957 10.66 0.466
1958 23.37 0.471
1959 6.13 0.475
1960 9.37 0.495
1961 5.59 0.506
1962 21.46 0.508
1963 10.88 0.478
1964 7.12 0.490
1965 15.57 0.494
1966 18.92 0.503
1967 22.84 0.511
1968 15.72 0.506
1969 27.81 0.505
1970 7.77 0.500
1971 12.09 0.499
1972 7.43 0.496
1973 21.14 0.487
1974 14.92 0.483
1975 14.35 0.489
1976 10.12 0.495
1977 11.67 0.497
1978 31.57 0.498
1979 19.29 0.522
1980 26.46
1981 8.98
1982 11.53
1983 33.63
1984 8.28
1985 12.38
1986 19.82
1987 5.61
1988 12.47
1989 8.34
1990 7.02
1991 16.03
1992 20.86
1993 27.36
1994 8.11
1995 24.37
1996 12.44
1997 12.85
1998 30.57
1999 9.08
2000 11.79
Average 15.02
1884 Max 38.18
1790 Min 1.49
Count 230