The cold environment

Abstract

Most of the world is cold by human standards. It is little appreciated that the average global ground-level air temperature is only about 9°C (integrating the atmospheric temperatures of all latitudes and all seasons). Figure 2.1 shows the mean surface air temperatures at various latitudes in midsummer and midwinter. It is evident that temperatures decline towards the poles, and that the seasonal amplitude of temperature change is greater at higher latitudes. It may also be seen that there are differences between the northern hemisphere and the southern hemisphere, with the south being substantially colder at equivalent latitudes. Because sea temperatures are much less variable and cannot be less than −1.9°C (see p. 4), coastal temperatures are usually milder than inland temperatures. The lowest recorded temperatures have therefore been collected from the centre of land masses at high latitude. In the northern hemisphere the lowest officially recorded temperature (−68°C) was reported from Oymyakon in easter Siberia, at least 400 km from the nearest coast and about 350 km south of the arctic circle. Paradoxically, it is appreciably warmer at the North Pole (situated on floating sea ice) than in northern Canada, Greenland or Siberia. The Antarctic situation is different, given the polar land masses and overlying ice-sheet, thousands of metres thick. The lowest ‘ground level’ temperature (–89.2°C) was recorded at the Vostok Base (USSR), nearly 1400 miles from the coast of Antarctica (and at an altitude of over 3000 m).