As already pointed out, a simple calculation gives the following:  if a cubic metre of water is cooled 1deg.  C., and the whole quantity of warmth thus taken from the water is given to the air, it will be sufficient to warm more than 3,000 cubic metres of air 1deg.  C. A few figures will give an impression of what this means.  The region lying between lats. 15deg. and 35deg.  S. and between South America and Africa —­ roughly speaking, the region investigated by the Fram Expedition —­ has an area of 13,000,000 square kilometres.  We may now assume that this part of the ocean gave off so much warmth to the air that a zone of water 100 metres in depth was thereby cooled on an average 2deg.  C. This zone of water weighs about 1.5 trillion kilogrammes, and the quantity of warmth given off thus corresponds to about 2.5 trillion great calories.

It has been calculated that the whole atmosphere of the earth weighs 5.27 trillion kilogrammes, and it will require something over 1 trillion great calories to warm the whole of this mass of air 1deg.C.  From this it follows that the quantity of warmth which, according to our calculation, is given off to the air from that part of the South Atlantic lying between lats. 15deg. and 35deg.  S., will be sufficient to warm the whole atmosphere of the earth about 2deg.  C., and this is only a comparatively small part of the ocean.  These figures give one a powerful impression of the important part played by the sea in relation to the air.  The sea stores up warmth when it absorbs the rays of the sun; it gives off warmth again when the cold season comes.  We may compare it with earthenware stoves, which continue to warm our rooms long after the fire in them has gone out.  In a similar way the sea keeps the earth warm long after summer has gone and the sun’s rays have lost their power.

Now it is a familiar fact that the average temperature of the air for the whole year is a little lower than that of the sea; in winter it is, as a rule, considerably lower.  The sea endeavours to raise the temperature of the air; therefore, the warmer the sea is, the higher the temperature of the air will rise.  It is not surprising, then, that after several years’ investigations in the Norwegian Sea we have found that the winter in Northern Europe is milder than usual when the water of the Norwegian Sea contains more than the average amount of warmth.  This is perfectly natural.  But we ought now to be able to go a step farther and say beforehand whether the winter air will be warmer or colder than the normal after determining the amount of warmth in the sea.

It has thus been shown that the amount of warmth in that part of the ocean which we call the Norwegian Sea varies from year to year.  It was shown by the Atlantic Expedition of the Michael Sars in 1910 that the central part of the North Atlantic was considerably colder in 1910 than in 1873, when the Challenger Expedition made investigations there; but the temperatures in 1910