Why aren't we in an ice age?

There's a theory that early humans managed to extend the current interglacial through relatively minor perturbations like deforestation. This theory suggests that the global climate is very sensitive to even minor changes, so the major changes we're currently introducing are very risky and dangerous.

See the links below for further discussion of this early anthropocene climate change theory. As bucket noted, we appear not to be due for another ice age for 20,000-50,000 years.

http://www.scienceonline.org/cgi/content/summary/2...

The Holocene interglacial started further back than you state but it was interrupted by the Younger Dryas event which had causes we're still trying to determine. If the ice returned 6,000 years ago that would be a far shorter interglacial than we've had since the ice age began and though the interglacials have many common features they don't all begin or end in the same way or at the same rate. There is a lot of necessary speculation and inference done from fairly tenuous ice core and sediment data so there is a lot we don't know. That data can be cherry-picked as well such as excluding tree-ring data that doesn't agree with preconceived notions.

Interglacials don't always last the same amount of time and it's unclear exactly why they begin or end. Theories include orbital eccentricities, solar output variation and other things but the Earth has endured far more CO2 than we could possibly put into the air with no dire consequences and endless warming. You're right that this interglacial has been unusual and beneficial for humanity, the variations have been minor with no rapid cooling or warming compared to many past interglacials.

You probably know that the Little Ice Age included the Maunder Minimum, a period with no sunspots, which was the coldest part of the period. Today's sun is nearly devoid of sunspots, the oceans are in a cooling trend that may last decades and we're nearing the end of the average length of an interglacial. Draw your own conclusions from that but even another Little Ice Age would cause far more death and damage than warming would do. You can adapt to heat but you would find it very hard to live under a mile of ice.

Humans have survived temps warmer than they are now and also far colder, but cold temps and ice would cause the population of most species to plummet dramatically as natural adaptation is too slow to keep up. It would get very crowded in equatorial areas if the ice does return since there is little land mass there, most of the land on Earth would be covered in glacial ice again.

"Perspective that with or without human perturbations, the current warm climate may last another 50,000 years. The reason is a minimum in the eccentricity of Earth's orbit around the Sun. "

http://www.scienceonline.org/cgi/content/summary/2...

At any rate, cooling into an ice age is relatively slow (many thousands of years) compared to the current anthropogenic warming trend.

Cave men drove SUVs.

Edit - what does linlyons mean by "what is happening today?"

It's not warming anymore.

we just had one...google/yahoo little ice age...in the 1600s there was a terrible cooling... you can look it up!