Maximum one-day snowfalls in the Big Apple are not on the rise

As the climate realists continue to perform the post-mortem on the failed New York City snowmageddon, we recall the alarmist predictions that such snowstorms are supposed to be gaining in intensity due to climate change.  In other words, the Big Apple should be experiencing greater one-day snowfall totals over time because of the ongoing climate chaos.

One set of charts is all that is required to debunk this theory.

Three NOAA National Weather Service climate sub-regions exist in New York City: Central Park, Kennedy Airport, and LaGuardia Airport.  The annual maximum one-day snowfall totals since records began for each site are shown in the chart below.

No significant trends toward higher maximum one-day snowfalls anywhere in the city.

Over at FiveThirtyEight, Nate Silver attempted to tackle another aspect of New York City's snowfall history, claiming that "[b]ig blizzards have become more common in New York."  To arrive at this conclusion, Silver regressed the "average days with more than a trace [greater than or equal to 0.05 inches] of snow" for the NYC-Central Park site from 1914 up to the present:

But while the total amount of snow has been about the same as usual, it has been snowing less often in New York. From 1914-15 through 1938-39, Central Park recorded an average of 37 days per winter on which there was at least a trace of snow. For the past 25 winters, there have been an average of 28 snow days instead. Alternatively, we can look at the number of days with more than a trace of snowfall. (A trace of snow is defined as any amount less than 0.05 inches.) These have decreased, too – in fact, they've fallen pretty sharply. A linear trend line drawn from the data suggests New York is getting about 10 days per winter with more than a trace of snow, compared to 18 a century ago.

Odd data.  When I go to the NOAA National Weather Service database and query the Central Park site for the number of days per winter with at least a trace of snow, I get an average of 16 per year from 1914-15 through 1938-39 (noting that there is not complete data for 1914/15, 1915/16, 1917/18, nor 1919/20 – meaning these years must be excluded from any analysis), not 37.  For the past 25 winters, I obtain only 11 per year on average with at least a trace of snow.

If we just look at the number of days with more than a trace of snowfall, it becomes clear that a linear regression over the entire time range – as FiveThirtyEight did – is not the best way to look at the data (note that incomplete data is also present for 1945/46, 1946/47, 1948/49, and 1952/53 – meaning they also had to be omitted).

Sure, overall, since records began in 1912/13, there is a net trend toward fewer days with more than a trace of snowfall in Central Park, but look closely at the data.  The data shows a trend upward from the early 1910s to the early 1960s, then a very sharp decline through the 1960s, and as the orange line shows, there has been no significant trend since 1970 (actually, the correlation is slightly positive, not negative).

Good luck ascribing this trend pattern to anthropogenic climate change.  If the fewer number of days now with more than a trace of snow in Central Park compared to a century ago were due to man-made greenhouse gases in the atmosphere, we would expect a declining trend to follow atmospheric greenhouse gas concentrations in order to reasonably postulate a causative relationship.  Instead we see absolutely no relationship since 1970 – the period over which atmospheric greenhouse gases have increased most rapidly.  All of the decline in the number of days with more than a trace of snow occurred between 1960 and 1970, and nothing since.

There is another way of looking at the problem: considering the number of days each year since records began with more than 2, 3, 6, or 12 inches of snow:

Don't let the eyes be tricked by the "snowiness" of the last decade in Central Park.  There are no significant trends in any of these data series.  And even though the number of days each year with more than six inches of snow looks to be sloping up at the end, the overall correlation since 1912 is negative, toward fewer of these heavy snow days rather than more.  If anthropogenic climate change wERE having any measurable impact on snowfall in the city, we would expect clear upward trends that roughly follow atmospheric greenhouse gas concentrations.  But we do not see any sign of this.

In sum, there is no clear or compelling evidence that anthropogenic climate change is leading to more intense snowfalls in New York City.

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