Isothermal Curves and Zones of Physical Climate

Late 19th century chart outlining the mean annual temperatures across the globe.

This vibrant color lithograph map shows the world according to its mean annual temperatures in 1891. Frigid, temperate and torrid zones are represented by shades of brown, green and pink, respectively.

Variations within each physical climate zone are shown with possible incremental gradients of 3 or 4 degrees Fahrenheit, between zero and eighty six degrees. The approximate thermal equator is also shown snaking along either side of the latitudinal equator near the middle of the page.