Every year we wonder if we’ll have a white Christmas, and every year we do. At least, that’s my recollection.

In early December the ground freezes, usually, or it always used to. The grass becomes a carpet of brown spikes, and sleet or slushy snow might fall and then melt off. When we were kids this tormented us – would Santa’s sleigh have anything to run on? But by Christmas Eve, snow always fell and blanketed spruces and backyards. Every Christmas Day in the 1950s and ’60s was white, as far as I remember.

I also remember being warned not to skate in mid-December but doing it anyway. By then every pond at least looked safe, and anyway, there would be cracking and bubbling to tell you if it wasn’t. In the 1970s we always skated before Christmas. And that was in southern Maine.

This year the pond up the road from my house in Troy has barely a skim of ice here in mid-December.

Making sense out of the weather is at least as tricky in the long term as the TV meteorologists find it one day at a time. And the facts of climate change can really be head-scratchers. Most scientists think global warming has kicked into gear, but some dissent.

The overall global surface temperature has risen about six-tenths of a degree Celsius since the late 1800s, and about three-tenths of a degree in the past 25 years. But also, the Southeast is cooler overall. And in the past 50 years, there has been a downward tendency in the difference between high and low daily temperatures over about half the earth’s land.

Bar graphs showing mean temperatures for Maine and the Northeast show no definite trends to an amateur eye. Some years spike high, like in 2001, 1998 and 1983, and some spike low, like in 1994 and 1971.

The same is true for snow cover. In the Northern Hemisphere it has shrunk by about 10 percent since 1966. The Arctic has lost ice. But at the same time, the Antarctic appears to have gained ice.

In my unofficial memory, the snow cover is decreasing. Some winters in the 1960s the snow was so deep in Cape Elizabeth that we climbed on the roof of the house and jumped. In December 1972, a friend and I were anxious to go snowshoeing, but there was hardly a dust of snow yet. My friend said to an old trapper in Buxton, “I wonder if there’s going to be ground cover this year.” The old guy scoffed: “There’s always ground cover.” Meaning that from late December to March, you need boots. I’m not sure that’s true in southern Maine any more.

It’s hard to believe March is any warmer than it ever was, given how long ice shelves line my ski-jump driveway. But officially, snow melt occurs roughly nine days earlier than it used to, and that I can believe. The occasional huge April snowstorm in Portland, like the one in 1982, seems to be extinct. In the 1960s my father kept records of the date the ice went out of Great Pond in Cape Elizabeth. It usually happened around the first of April. Now Great Pond doesn’t even freeze solid enough to skate on in any given winter.

I’m pretty confident Christmas Day will be white in Troy this year. But we won’t be skating anytime soon. In my recollection, global warming appears to be a fact of nature.

Contact Amateur Naturalist at dwilde@bangordailynews.net.