The sun is extremely powerful (estimated 100 billion hydrogen bombs going off every second)... think about that number relative to earth. Not 100, or 100 million, but 100,000,000,000 one megaton bombs... every second of every day.
... and volatile (flares, CME's, radiation, sunspot cycles, etc). Small changes in that huge output over periods of time will affect earth's climate. Our orbit also varying over time. Virtually all the heat arriving to earth's atmosphere comes from the sun.
Look at ice ages, subsequent global warmings, more ice ages, re-warmings, etc...
Will global temperatures warm and cool over time, sure... over short and long periods of time. Geological record proves it. We'll heat up again and cool down again... and again... and again.
Consider also that every day we heat up and cool down, every month, every year, etc... Those changes are all natural and occur over all time periods. Many dozens of degrees cooling and heating changes constantly.
All of it naturally occurring for hundreds of millions of years.
Anyways, that's how I look at it. More than nuff said (by me).
