Oh, I hesitate to wade into this in the company of friends, and science isn't my strongest stuff, but . . .
Yes, the climate has shifted numerous times over the millennia, but the models that I believe were developed in the 1950s pointed to the carbon dioxide that all our fuel-burning releases as holding heat in the atmosphere. (jeez, someone more up on this could explain it better.) And the incremental warming of our atmosphere seems to bear out those predictions. While most of us don't see/feel the effects--we see weather, not climate--those in the extreme north and south regions do. Glaciers in the far north, and ice cover in Antarctica, for instance, are receding at an alarming rate.
Besides general climate warming--which is undeniably happening, for whatever reason--the models also predict more extremes of weather. Which we DO experience: hotter hots, colder colds, heavier rains & drier dry spells, later frost dates, more severe storms, and so on.
Dave Schultz (PhD), who worked for NOAA and taught at U. of Oklahoma when I lived there--we were kayaking and camping buddies--explained it much better. He's in England now. And two scientists up the road (everyone lives up the road here, I'm at 6400 feet, the low end of our district) are in total agreement.
The same public relations outfits that served big tobacco for years, putting out the word that smoking was no threat to health, now serve big oil/gas by poisoning the public discussion on climate change. Within companies like Exxon-Mobil, these companies have for years had very private and closely held policies to deal with their reactions to climate change as it affects their operations. Shipping, for instance, may open up in far northern regions where ice has prevented it.
I am not an alarmist when it comes to climate change. I believe its effects are damaging to human interests. But I am an optimist, and expect that when we do finally get serious about the problem that nature will allow a turn-around when we make the proper adjustments. My #1 evidence of nature aiding our attempts to undo former wrongs is the Cuyahoga River. I remember when it caught fire--yes, the river caught fire from an overload of waste. I'm told the Cuyahoga is pretty much a sportsman's paradise now. And in all my doings in woods and agriculture, I've seen nature turn quickly to heal past damage. Seems like healing and growth are nature's default settings.