I was just reading some of Thoreau’s collected essays. In one, he relates how “ice out” (the melting of the ice) on Walden pond didn’t happen until mid-April (in the spring of 1847). I live about 12 miles from Walden Pond, and in recent years, the ice is usually gone by early March. Thoreau also said that old timers told him that ice out sometimes cam as late as mid-May. So were winters much colder then? Or was Thoreau just seeing an anomaly?
I am not an expert, but it’s probably global warming. The phenomenon is called season creep, and the Wikipedia has a brief rundown. (Season creep - Wikipedia)
The 1840s are considered to be part of the Little Ice Age. The end of it, true, but still part of it…
At least in the Arctic, there is no well-defined “Little Ice Age”, as can be seen here (a bit of a dip around 1500-1900, but it was cooling overall until 1900, due to orbital variations, which are still trending cooler, possibly eventually leading to a full-blown ice age - if that were still the only major influence).
Also, global warming doesn’t necessarily mean that it will always get warmer; for example, changes in atmospheric circulation patterns due to melting Arctic sea ice have been linked to severe winter weather outbreaks in recent winters, especially since 2007, including extreme cold spells (of course, heavy snowstorms are more of an extreme precipitation event since it may not be colder than normal; Antarctica is a desert because it is so cold there is little moisture in the air).
Indeed, it is entirely possible tha tthe long term result of global warning will be that things will get… cooler. But also, frighteningly, drier. The scary thing about anthropomophic climate change is that the end result is unpredictable; the popular image is of a hotter Earth where the oceans rise a bit, but the reality could be much more complex and seriously screw-things-uppy than that.