During my early experiences as a regular passenger on commerical
airlines, in the early 1970's, it seemed that once you took off and
flew through the near-surface clouds, the flight was usually very
smooth, the air was clear, and the sky bright blue (during the
daylight hours). Lately it seems that every flight I take involves
some "light chop" for some point after we reach cruising altitude.
Transcontinental flights are the worst, I think it's been a long time
sinces I've been on a coast-to-coast flight that didn't involve having
the "fasten seat belt" sign on for periods of 30 minues or more. In a
couple of flights, the pilots even told the flight attentdants to sit
down and buckle up -- that's when I really get nervous. Also, it's
pretty common to spend 1-2 hours flying though high clouds, even at
39,000 feet. Like I said, I never remember any of this when I flew
during the 1970's. All the turbulence happened when the plane was
closer to the ground.

Is there something more than my subjective recollection here at work?
Has there been some sort of measurable increase in turbulent weather
and high-altitude clouds over the past 35 years?

Thanks,

Ted