What is remarkable about our Fall into Winter? It seems inevitable. Our days get rapidly shorter. We get colder. And our winter rains return, with lots of snow in the mountains.
But as soon as you look at the details, you realize that what we think is simple and inevitable is really a wondrous combination of factors. For instance, we cool off this time of year twice as fast as we warm up in the Spring. Every four days, we ratchet down one degree Fahrenheit in average high temperature. That average cooling slows to a crawl by the Winter Solstice (near Christmas), and begins its slow ascent toward Summer on the 6th of January (the Twelfth Day of Christmas).
Yet our coldest day of the year at the Portland airport was February 2, 1950 when we sank to -3 F. Although we have observed a trace of snow as early as October 31, we typically get our greatest snowfalls after the first of the year and can still get significant snow as late as March. Our greatest accumulation of snow at the Portland airport occurred January 31, 1950, just as we experienced our only two days below zero.
Other areas at the same latitude are much different. Even areas just east of the Cascades in Oregon see much more severe winters that can show up faster in the Fall and disappear sooner in the Spring than they do here. On December 8th, 2013, it was 41 degrees below zero F near Redmond, Oregon in our last major Arctic outbreak.
A year ago February, I debated two Canadian politicians at Upper Canada College in Toronto. Toronto was experiencing record cold and snow as we were experiencing record warmth. The 50 degree F difference between Portland and Toronto high temperatures was astounding. Yet part of that difference is very normal, because we are kept relatively warm for our latitude by the relatively warm Pacific Ocean nearby. The rest of the difference depends on our location relative to the circumpolar jet stream. If the jet stream stays to our north, we gain access to warm equatorial air and above average temperatures. But that also means that others will find themselves on the cold side of the jet, exposed to bitter Arctic cold. Toronto and New England were far less lucky than we were in February, 2015.
Communities farther north experience much greater seasonal swings and much greater climate variations. This year Juneau, Alaska had an unusually early three inches of snow in mid-October. Anyone attempting to sail across the Arctic Ocean or even across Hudson Bay will usually attempt a crossing at sea ice minimum in September. But they do not want to be late, because the sea ice returns with a vengeance in October! The Arctic is notoriously unforgiving.
In contrast, the tropics hardly have seasons at all. When I spent time on the Kwajalein Atoll watching incoming Intercontinental Ballistic Missiles fired from Vandenberg Air Force Base in California, I was impressed by the heat and humidity. But I was also impressed by the fact that they had never recorded a temperature above 98 F or below 70 F.
Every school boy can tell us why the seasons change and why the effects of that change are more spectacular in the polar regions. It is all about the 23.4 degree tilt of the Earth’s axis relative to the plane of the ecliptic, the plane defined by the earth’s orbit about the Sun. Since our North Pole always points to the North Star as we orbit the Sun, the Northern Hemisphere sees the noonday Sun highest in the sky in June and lowest in December. Above the Arctic Circle, the Sun disappears for days to months in the winter and never sets for the same period in the summer.
Unfortunately, school boys seem to forget some of what they learned by the time they graduate from college. One study of graduates of Harvard University found that fully half could not correctly explain why the seasons change. That question is considered a good measure of both scientific literacy and scientific curiosity.
Such lack of literacy has broad implications for the ability of average citizens to withstand the scamming of science that is so prevalent today.The incorrect answer that we all too frequently hear is that the Earth is closest to the Sun in the Northern Hemisphere summer and farthest in our winter. If that were true, why is it hot in Australia in January?
But even more amazing is that our elliptical orbit takes us significantly closer to the Sun in January, giving us about 80 watts per square meter more insolation (incoming solar radiation). Hence, despite our dark dreary winter days, the Sun is actually getting brighter during our Fall, becoming brightest in January. We don’t perceive it that way, because the Sun is so low in our sky this time of year.
A reasonable person might conclude that the Earth as a whole must, therefore, be warmest in January. That, too, is incorrect. The global temperature measured by NASA satellites shows a substantial three degree Celsius seasonal variation that dwarfs monthly excursions from ‘normal’ by a factor of nearly ten. The Earth is actually warmest in the Northern Hemisphere summer when sunlight is weakest! Why? Because most of the world’s landmass is in the Northern Hemisphere and it heats up far more easily than do our oceans which are mainly in the Southern Hemisphere.
All of this should tell us that the Earth’s seasons and climate system are far more complex than we might otherwise imagine. That should make us very wary of explanations that are too convenient, are too simplistic, and are offered by those without scientific training. Of the infinite number of possible explanations, only ONE is correct, yet many may seem plausible to non-scientists. This has invited the now daily scamming of science by those promoting solutions to problems that do not exist. Many people fall victim to ‘the sky is falling’ scam and its numerous variants.
Our climate provides fertile ground for scams because of the wide climate variations seen at mid and high latitudes. Our climate is rarely “normal.” Yet “abnormal” is perfectly “normal.” This October we experienced near record rainfall, presumably as a consequence of the Super El Niño we experienced earlier in the year.
Does that mean Thanksgiving in Portland this year will be wetter and warmer than normal? AccuWeather is betting it will be. But their long range forecast also shows a significant dip below normal before Thanksgiving. Such forecasts are, at best, educated guesses.
Our climate does seem to get stuck in a rut. But as soon as we think it will remain there, it abruptly changes. Mother Nature has a perverse sense of humor with those who assert more knowledge than they have. Last year in late November, Oregon State University’s chief climate alarmist, Phil Mote, confidently predicted a warm dry winter, just five days before we began the wettest winter in our history.
We had a wonderful Spring and Summer this year, with a long growing season and moderate temperatures. 2016 was a far cry from 2011 when the Pacific Northwest suffered the coldest Spring in the temperature record followed by a cool Summer.
We should be thankful if our day of Thanksgiving this year turns out to be pleasant but not surprised if it disappoints us. Part of our remarkable ‘Fall into Winter’ is substantial natural variability.
Gordon J. Fulks lives in Corbett and can be reached at firstname.lastname@example.org. He holds a doctorate in physics from the University of Chicago’s Laboratory for Astrophysics and Space Research.