I remember being taught in grade school (50s-60s) that we we were in a warm period in between periods of glaciation, and that we would be re-entering a new glacial period in the next 10-20 thousand years or so.
O-D; article about Milankovitch cycles:
Science Daily Why Ice ages occur every 100,000 years or so. "The Milankovitch cycles "The explanation for the cyclical alternation of ice and warm periods stems from Serbian mathematician Milutin Milankovitch (1879-1958), who calculated the changes in Earth's orbit and the resulting insolation on Earth, thus becoming the first to describe that the cyclical changes in insolation are the result of an overlapping of a whole series of cycles: the tilt of Earth's axis fluctuates by around two degrees in a 41,000-year cycle. Moreover, Earth's axis gyrates in a cycle of 26,000 years, much like a spinning top. Finally, Earth's elliptical orbit around the sun changes in a cycle of around 100,000 years in two respects: on the one hand, it changes from a weaker elliptical (circular) form into a stronger one. On the other hand, the axis of this ellipsis turns in the plane of Earth's orbit. The spinning of Earth's axis and the elliptical rotation of the axes cause the day on which Earth is closest to the sun (perihelion) to migrate through the calendar year in a cycle of around 20,000 years: currently, it is at the beginning of January; in around 10,000 years, however, it will be at the beginning of July.
Based on his calculations, in 1941 Milankovitch postulated that insolation in the summer characterises the ice and warm periods at sixty-five degrees north, a theory that was rejected by the science community during his lifetime. From the 1970s, however, it gradually became clearer that it essentially coincides with the climate archives in marine sediments and ice cores. Nowadays, Milankovitch's theory is widely accepted. "Milankovitch's idea that insolation determines the ice ages was right in principle," says Blatter. "However, science soon recognised that additional feedback effects in the climate system were necessary to explain ice ages. We are now able to name and identify these effects accurately."
The efforts to "Stop Global Warming"-- if successful--might be more likely to propel us back into an early Ice Age, not a good thing.
I’m old enough to remember the “smog days” during the late 60’s and early 70’s. The skies where cloudy for days, almost an entire summer one year. Here, in N.J. we have blue skies again, have for several years now. The U.S. has done a great job in cleaning up, not only the air, but streams, rivers and lakes. We are not yet pollution free, but have made much more progress than most other countries. Other countries such as China, India, Russia, many African ones, and some South American countries have a long way to go.