Guest Essay by Kip Hansen — 12 December 2023
Snow – those marvelous little crystals of frozen water that drift down from the sky – in gentle silence, in the fury of an artic-like blizzard, or in any and everything in between.
Where I grew up, snow was something that we traveled a couple of hours to visit for the day. Once a decade, we’d rent a cabin up in snow- country and spend a week with aunts and uncles and cousins. But I never had to live where it snowed in the winter – I surfed in the winter. Sometimes university friends and I would drive up to sled and toboggan on Saturday and drive back down to surf on Sunday.
[This essay is only 1500 words — with a lot of graphics….]
I saw a few weeks ago that some climate skeptic had twitted (Xed?) that snow was not decreasing, but rather increasing. He used little graph:
Well, fair enough, that is the Rutgers Snow Lab graph for Fall Northern Hemisphere Snow Extent covering the satellite era (1967-present). Most readers here are generally familiar with the climatic history of the last century or so, and might notice something: during the “Global Cooling Period” late 1960s through the mid-1970s there were years with very high fall snow extent, over on the left side, which are similar to the last couple of decades, on the right.
Note: NOAA and NASA (for weather and climate) use: Meteorological seasons: “spring … includes March, April, and May; meteorological summer includes June, July, and August; meteorological fall includes September, October, and November; and meteorological winter includes December, January, and February.”
But, this is just the fall months: September, October, November (although Astronomical Winter does not begin until 21 December). And it is only the Northern Hemisphere. Only the Northern Hemisphere [NH hereafter] because almost all of the planet’s snow, excluding the ice caps, is found in the Northern Hemisphere – there is some in the south up in the Andes of South America – but its extent is insignificant. NASA’s Earth Observatory offers this for Winter 2022:
If you look closely, you can see the little strip of white snow atop the western mountains ranges of South America.
It is not valid to show just the Fall NH Snow Cover Extent and then say: “See, more snow, I told ya so!”.
Total NH snow cover extent has been really very stable across the satellite period:
Both the highs and lows are pretty stable, at least since 1972 [I have some personal doubts about the two very high ‘lows’ prior to 1972 and will query Rutgers on those two data points]. The high extent seems to be centered on about 45,000,000 km2, maybe a little more. The lowest extent somewhere between 25 and 75 million km2.
Here’s another way to look at it:
The red and blue traces are “…extremes are calculated using the 56-yr record from Jan 1967 to Dec 2022 “ so the highest for that week in the 56-year record and the lowest. So, we can see that 2022, the black trace, was very near the highest extent in early Fall (late September) and Oct-Nov. Otherwise, right on the mean through the Spring, and quite low late spring and through the summer.
The point of that exercise was to show that snow cover extent is variable, year to year, and within the same year, season-to-season – 2022 from lowest in 56 years in July to highest in 56 years in November – shifting to dropping below average Dec to Jan. That is just one year.
Now, here’s what all that is composed of during the seasons:
So, snowier Falls, a bit snowier Winters, and less snowy Springs. The vertical scales are very close, about million Km2 top to bottom, but each graph is a different portion of the whole vertical scale, it is not appropriate to set them side by side. Properly, they look like this:
So, we see that the increase in the Fall does not quite make up for the decline in the winter and spring. But, looking back up at the NH Snow Extent graph up a bit (it’s blue) we’ll see that there is a slight decline since the turn of the century, but overall stable.
With snow, Snow Cover Extent is not the same as Amount of Snow – more commonly measured as depth in inches (or cm or feet or meters) or as water content. Snow is hard to measure – obviously there is fluffy snow, grainy snow, wet snow, powder snow — many, many types of and conditions of snow – it is often said that the Inuit or the Greenlanders have “40-50-200-400 – take your pick – words for snow”. [This is not strictly true, of course, but they do have a lot of words describing types of falling snow and snow conditions on the ground.]
The U.S. National Weather Service gives us this:
Three Types of Measurements are Reported:
- Liquid equivalent of snowfall (last 24-hrs) reported in HUNDREDTHS (such as 0.22′)
- Snowfall (newly fallen snow) is reported in INCHES and TENTHS (such as 2.4″). It is taken as soon as snow has stopped falling if possible and no more than 4 times a day.
- Snow Depth (total depth of snow on the ground) is reported to the nearest WHOLE INCH (such as 11″). It is typically reported at 7am.
[This copy-and-pasted quote from weather.gov contains an error. Liquid equivalent of snowfall is reported in hundredths of inches – ” – not feet – ‘ – as indicated above, see here. I have requested a clarification. Just heard from NWS and they are correcting the typo.)
Snowfall totals are complicated and determining ground snow conditions can be complex. This is illustrated by the many factors reported daily by National Weather Service’s National Operational Hydrologic Remote Sensing Center on its National Snow Analyses page:
This is the National Snow Analysis for 11 December 2023. It is not yet winter in the northern hemisphere, only late fall. In the U.S. Northeast, much of the existing snow was melted by extensive warm rain just yesterday (10 December) but higher elevations are now again snow covered this morning as temperatures plunged overnight while rain was still falling. There is an amusing error in the Automated Model Discussion portion in the upper right: the model reports 2,888.6 inches (240 feet) of snow as the maximum snow depth (cue: rants about models in comments).
How about across the world?
If we want the statistician’s answer (statistical trends) to the question: “Are we seeing more snow this century than previously?”, we can again go to Rutgers Snow Lab for that answer – at least for Snow Cover Extent (not the same as “more snow”):
Over the satellite era (1967-present), Snow Cover Extent is increasing at a rate of about 2% per year for both Eurasia and Northern Hemisphere (alone) or NH+Greenland. Note that including Greenland in the NH calculation reduces the percentage of increase. Why? Greenland doesn’t change much, if at all. (It’s a math thing….)
Snow Cover Extent is important climatically because it changes the albedo of the Earth’s surface. But in many other senses, such as hydrologically, the water equivalent of the snow is much more important, because as the snow pack slowly melts it percolates down into the aquafers and provides water to streams and rivers.
So, do we know the answer to the question:
“Has global warming/climate change resulted in More or Less snow worldwide (say, over the last 50 years)?”
We don’t know.
Even with satellites and advanced computer algorithms, the most recent paper on Snow Water Equivalent—amount of water falling as snow—measured by satellites concludes:
“At present, information on water stored as seasonal snow is highly uncertain. Because of surface monitoring limitations, satellite measurements are critical, but current missions are inappropriate for determining snow mass with the spatial, temporal, and accuracy characteristics required to deliver climate services, effective water resource management, and skillful environmental prediction such as streamflow.” [ source ]
Bottom Line:
1. As with many things climatic, the best answers to the posed question: “Are we getting more or less snow over the last 30 years (1 climatic period)?” is “We don’t really know.” And “It depends on what you mean.”
2. If we just mean Snow Cover Extent, the answer is “Yes, we are seeing an increase of about 2% per decade over the last 50 years” which is a pretty good estimate from satellite measurements. This does not mean that everywhere is seeing more snow – but only the worldwide and regional totals are seeing more snow.
3. Astronomical Winter arrives next week – and I say “Let it snow!”
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Author’s Comment:
The snow issue, as part of the overall global warming/climate change meme, is a mess. The IPCCists and Climate Crazies demand that there must be less snow, less ice, shrinking glaciers because “global boiling”.
It is much better for your mental and intellectual health to look at the actual measurements in a scientific way — just look at them and let the measurements have their say.
Like so many climate-related metrics, the numbers available for snow may not be as accurate as we need and, in many cases, available metrics don’t measure what we want to know.
So, Let It Snow!
Thanks for reading.
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