Feedbacks include loss of Arctic sea ice, melting glaciers and ice sheets, release of 'frozen' methane as tundra melts, and growth of vegetation on previously frozen land.
Now, in the twenty-first century, as we approach an ice-free, accessible pole that has succumbed to our influence, we dream of a faraway frozen land unspoiled by humankind.
I asked to see the programme in action, so on a bright, sub-zero morning I accompanied a government delegation to the troubled province of Ghazni, taking off from a frozen landing site at the Nato base in Kabul in a US Army Chinook helicopter.
In summary, vegetation cover, freezing soil and snow cover are important factors influencing the land surface roughness conditions.
Barbara Stocking, the chief executive of Oxfam, which is holding a day of action against land grabs on Thursday, called on the World Bank to temporarily freeze all land investments in large scale agriculture to ensure its policies did not encourage land grabs.
My lessons began before we got off the frozen lake landing strip.
The luckless Mehmood, it turned out, had rashly frozen a land deal which involved a certain Asif Ali Zardari, the President of Pakistan.
It symbolises fertility, mysterious brotherhoods, and the struggle between the people and the spirits who freeze the land in the winter, leaving it barren.
Therefore, the active water cycle occurs in a much more limited coastal area, and a smaller amount of water is circulated (consistent with a larger amount of water frozen over land).
