One thing I cannot understand; why, now that we have good records for most cities going back at least to the 1930's, are we still using 30 year means? As 'ORH_wxman' correctly pointed out in another thread back on Eastern, a 30 year period can easily encompass a warm or cold decadal period. Next year, when they switch to 1981-2010 I expect New York City to be below-normal temperature-wise most winters and above-normal for snow. Global warming; problem solved. Why don't they use 50 or 60 year