Aerin

Interesting that, as recently as the late 1970's, one of the primary concerns about climate change was global cooling:

For most of the Earth's history, there were no "permanent" ice caps, as in the Arctic and Antarctic today.  We have, over the past few hundred years, made a partial emergence from our ice age caused by some as yet unexplained minor climatic variation; and there are certain signs that we may plunge back into the global cold temperatures characteristic of our epoch as seen from the perspective of the immense vistas of geological time.  It is a sobering fact that 2 million years ago the site of the city of Chicago was buried under a mile of ice.

Sagan goes on to discuss human-generated climate change via carbon emissions, but warns of this actually causing the Earth to get colder.  He cites a trend of rising temperatures from the industrial revolution to about 1940 (attributed to the burning of fossil fuels) and then a steep decline thereafter (attributed, possibly, to increased particles in the atmosphere raising the Earth's albedo and reflecting more of the sun's energy outward).

Of course, it was right about 1980 that global temperatures started rapidly rising again.

Still, sentences like this in a relatively recent book are pretty jarring:

There are worrisome positive feedback possibilities on a planet with declining temperatures.  For example, an increased burning of fossil fuels in a short-term attempt to stay warm can result in more rapid long-term cooling.