We are most definitely experiencing global climate change. According to the EPA and the National Academy of Sciences, "the Earth's surface temperature has risen by about 1 degree Fahrenheit in the past century, with accelerated warming during the past two decades. There is new and stronger evidence that most of the warming over the last 50 years is attributable to human activities." (i.e., greenhouse gases).
Mix into that combination the Sun's cycles, lunar gravitational pull, all of the changes below the Earth's surface (including below the oceans), polar ice melting and everything else that effects global weather patterns—it's no wonder that our seasons are changing.
Having been born in the land of Walk Softly and Carry a Big Shovel (Minnesota), we moved to Colorado in 1965 to get away from the frigid winters—which I understand have changed for Minnesotans, as well. Throughout my childhood and teen years, I remember
four very distinct seasons in Colorado: green and mild springtimes, hot and moist summers, cool and crisp autumns, and brisk and snowy winters. Now Colorado's seasons all seem to overlap one another, with unpredictable and often volatile weather changes. Perhaps you've heard our wx motto: If you don't like the weather, wait ten minutes and it will change!
Our last unpredicted weather shocker was the blizzard of 2001; it snowed ceaselessly for days and nights and when it finally stopped, we had 6 feet of snow, a collapsed awning, busted (big) trees, and we were snowbound for 5 days. The Mile-High City virtually shut down and I'd never seen that before! This was during Spring Break!

The wx forecaster had called for a foot or two of snow. Pffffft! We've also experienced merciless drought (followed by summers of endless wildfires) and an increase in tornado activity in the past decade or so.
I've learned to take wx forecasts with a grain of salt, and try to err on the "worst-case scenario" side.

I've also learned that when I look into all of the elements out of our control that effect the changing global climate, it can be pretty spooky. :-\
Hmmm....
