Some people call what has been happening the last few years “weather weirding,” and March is turning out to be a fine example.

As a surreal heat wave was peaking across much of the nation last week, pools and beaches drew crowds, some farmers planted their crops six weeks early, and trees burst into bloom. “The trees said: ‘Aha! Let’s get going!’ ” said Peter Purinton, a maple syrup producer in Vermont. “ ‘Spring is here!’ ”

Now, of course, a cold snap in Northern states has brought some of the lowest temperatures of the season, with damage to tree crops alone likely to be in the millions of dollars.

Lurching from one weather extreme to another seems to have become routine across the Northern Hemisphere. Parts of the United States may be shivering now, but Scotland is setting heat records. Across Europe, people died by the hundreds during a severe cold wave in the first half of February, but a week later revelers in Paris were strolling down the Champs-Élysées in their shirt-sleeves.

Does science have a clue what is going on?

The short answer appears to be: not quite.

The longer answer is that researchers are developing theories that, should they withstand critical scrutiny, may tie at least some of the erratic weather to global warming. Specifically, suspicion is focused these days on the drastic decline of sea ice in the Arctic, which is believed to be a direct consequence of the human release of greenhouse gases.