You’re absolutely correct. We are technically still in an ice-age due to the existence of ice upon the planet. Nested within the ice-age cycles are the glacials and right now we’re in an interglacial, and have been for about 10,000 years.

Both the ice-ages and the glacial maxima are tied to the movement of our planet within space.

The glacial periods occur when there is a decrease in the amount of incoming solar radiation coupled with a decrease in solar radiation absorption due to a lower angle of incidence of sunlight and a greater reflectance from Earth.

This is occasioned due to changes in the shape of Earth’s orbit around the Sun. The shape tends to, then from, circularity, such that we have an orbit that stretches elliptically then rebounds back to circularity.

The full cycle lasts some 100,000 years during which time there are 90,000 years of gradual cooling followed by 10,000 years of comparatively rapid warming. Having recently (geologically speaking) encountered the warming phase we are now in an interglacial period and are moving toward the next glacial maximum, albeit some 80,000 years from now.

During a full cycle the temperature swings by an average of 7°C. Other orbital variations that the planet goes through can amplify or attenuate the effects of obliquity such that the normal temperature range falls between 6°C and 8°C.

Much more impressive are the full ice-age cycles, these are tied to the orbit of the entire solar system around the galactic centre and have a periodicity of about 125 million years.

During a full cycle the average temperature of Earth will range from 4°C at the coolest to 35°C at it’s warmest.

During the cold phase all but the Equatorial Region of the planet will be frozen solid. By contrast, the hot phase sees tropical plants growing in the polar regions.

In the grand scheme of things our planet is presently a little cooler than average having, as it does, an average global temperature of 15°C.

As with the glacials, we’re also on the downward slope toward the next ice-age maximum. We’ve been generally cooling for the last 50 million years and have another 10 to 20 million years before we start warming up again. It’s going to be about 50 million years from now before Earth will be completely free of ice and can be truly said to be out of an ice-age.

One point you made that I would pick up on – you said that the planet was warming up by itself…

We should be cooling down, the last interglacial warming period ended some 10,000 years ago and since then the general trend has been a downward one with temperatures reducing by 1°C. Uninterrupted this cooling will continue at the same rate until we reach the next glacial maximum. However, all of this cooling, and more, has been compensated for by the warming we’ve seen in recent decades. The average temperature of Earth is higher now than it has been since the last but one glacial maximum some 130,000 years ago.

Over much shorter periods of time, ranging from a few days to a few hundred years, there are periods of natural warming and cooling. The reasons for these are many but they all revolve around the amount of solar radiation entering the atmosphere and the amount of thermal radiation being retained by it.

We have the capacity to affect both of these – we can pollute the atmosphere and block out sunlight (global dimming) and we can enhance the amount of heat being retained by increasing the levels of greenhouse gases present in the atmosphere (global warming).

30 years ago we nearly brought about a period of global cooling. The dimming caused by our polluted atmosphere was blocking so much sunlight that it countered the underlying warming and global temperatures levelled off. Since then the various Clean Air Acts have resulted in decreased levels of pollution. Ironically this has cleared the way for warming to return to the fore.