July temperatures in New Hampshire change from ~28C during the day to ~15C at night, so a diurnal change of 13 degrees. January temperatures are about 1C in the day to ~-18C at night, so a diurnal change of ~19 degrees. Let’s average those and say the diurnal temperature cycle in NH is about 15 degrees. And the seasonal temperature cycle is about 30 degrees. People, plants and animals who live here understand these changes and have adapted to them in their own way, usually by slowing down or shutting down in the winter.
What about an ice age? How much would you need to change the modern annual average temperature to cause an ice age? What temperature change would allow huge ice sheets to form over Scandinavia and Canada and most of the Rocky Mountains? -50 degrees? -100 degrees?
The annual average global temperature would need to cool by 6 degrees. That’s all. Annual average temperature in New Hampshire would go from a high of 14C to 8C, and the low would go from 2C (just above freezing, which is 0C) to -4C. The summers would not be warm enough to melt all the snow, ice sheets would build, crops would no longer grow this far north, humans would need to migrate south.
So next time you read an article about future global warming, and it says the annual mean temperature will only rise about 3 degrees, think to yourself, THAT’S HUGE!! New Hampshire’s climate would be more like North Carolina.
Lesson: Start investing in palm trees.