APPENDIX
THE FACTORS OF TEMPERATURE
To calculate the probable temperature of January or July at any point, the following procedure should be adopted:
Draw a circle round the point of angular radius ten degrees (i.e. set the compass to cover ten degrees of latitude) and divide this into two halves by a line passing from north to south through the centre. By means of squared tracing paper, or otherwise, measure: (a) the amount of ice in the whole circle; (b) the amount of land in the western half; (c) the amount of land in the eastern half. (a) is expressed as a percentage of the area of the whole circle; (b) and (c) as percentages of the area of a semicircle.
The term “ice” includes ice-sheets such as that of Greenland or Antarctica, and also frozen sea or sea closely covered by pack-ice; the latter figure may vary in different months.
The temperature in January or July is then calculated from the following formula:
Temperature = basal temperature + ice coeff. x per cent. of ice + land west coeff. x per cent. of land to west + land east coeff. x per cent. of land to east.
The basal temperatures and the appropriate coefficients are given in the following table.
In calculating the effect of a given slight change of land and sea distribution, it is not necessary to employ the basal temperature. Instead the equation can be treated as a differential, and the change of temperature due to the change of land and ice calculated from the figures in columns 3 to 5. The figures are given in degrees absolute, 273°0 = 32° F. To convert differences to Fahrenheit, multiply by 1°8.
| Latitude. | Basal Temp. (Water Zone). | Ice Coeff. | Land, West Coeff. | Land, East Coeff. |
| Jan. | a. | |||
| 70 N. | 298.8 | - 0.49 | - 0.43 | - 0.20 |
| 60 | 277.4 | - 0.07 | - 0.31 | - 0.01 |
| 50 | 276.8 | - 0.09 | - 0.29 | 0.09 |
| 40 | 282.5 | — | - 0.17 | 0.04 |
| 30 | 289.6 | — | - 0.08 | 0.03 |
| 20 | 294.2 | — | - 0.01 | - 0.01 |
| 10 | 298.6 | — | - 0.01 | 0.03 |
| 0 | 299.3 | — | 0.01 | 0.00 |
| 10 S. | 298.2 | — | 0.04 | - 0.01 |
| 20 | 296.2 | — | 0.07 | 0.00 |
| 30 | 293.5 | — | 0.06 | 0.03 |
| 40 | 289.3 | — | 0.09 | - 0.03 |
| July. | ||||
| 70 N. | 279.3 | - 0.16 | 0.02 | 0.02 |
| 60 | 280.7 | — | - 0.01 | 0.11 |
| 50 | 285.8 | — | 0.04 | 0.06 |
| 40 | 291.1 | — | 0.05 | 0.07 |
| 30 | 296.8 | — | 0.08 | - 0.01 |
| 20 | 297.6 | — | 0.07 | 0.02 |
| 10 | 298.8 | — | 0.03 | - 0.01 |
| 0 | 298.6 | — | 0.02 | - 0.01 |
| 10 S. | 296.9 | — | 0.04 | - 0.03 |
| 20 | 293.1 | — | 0.02 | - 0.02 |
| 30 | 288.2 | — | - 0.01 | - 0.01 |
| 40 | 284.0 | — | 0.00 | - 0.03 |
In the case of the calculation of the effect of comparatively slight and irregular changes in land and sea distribution in a limited area, such as those of the Littorina Sea referred to on p. 128, it may be found that a ten-degree circle is too wide an area to employ, the changes from land to sea at one point being nullified by changes from sea to land at another more distant point. In such a case a smaller unit such as a circle of five degrees radius can be employed. As a rough approximation it may be said that the effect of the conversion of a square mile of land into sea, or vice versa, on the temperature of a neighbouring point is inversely proportional to its distance. Since the area of a five-degree circle is one-quarter that of a ten-degree circle, while the average distance of the land composing it is one-half, we have to divide our regression coefficients by two in order to fit the new data.
This method was applied to obtain the probable temperature distribution on the shores of the Littorina Sea at its maximum extension, and gave results which agreed remarkably well with those calculated by geologists from the animal and plant life of the time.
See London Q. F. R. Meteor. Soc., 43, 1917, pp. 169-171.