Polar extremes in any debate need each other for their own existence, but the temptation to make ideological investments in science should be resisted.

Identifies the polar extremes that make conflict resolution impossible.

Injuries have bitten deep into the blue riband events but two races at polar extremes promise to disperse the gloom.

Two people at the polar extremes of the same complex debate.

The arctic woolly-bear caterpillars are unique in their combination of adaptations to the polar extremes.

The volume of polar sea ice actually increased by a third in 2013.

Was there an open polar sea?

Scaling its sides, they eventually found a passage through to the polar sea.

These take the only craft to survive the fight, upriver; scale the waterfall at the end of the river and enter the polar sea.

This also allows the polar sea ice to increase its annual growth and temporary extent at a greater level due to lack of direct sunlight.

Alongside it are four statues of emperor penguins with their beaks tucked under their wings as though sheltering from a polar winter.

More important still, he spent time in the polar regions doing his own research, especially during the polar winter just before the expedition.

Later, as the expedition wore on and polar winter turned to spring, the 24- hour sun got to work on the fragile ice- pack.

The permanent darkness of a polar winter, he explains, differentiates early risers from people who naturally stay up late.

Fantastic photography and editing bring the polar winters to life tonight as this magical, magisterial series continues.