There are several classification systems for global climate currently in use, but the best-known is the Köppen classification system (sometimes known as the Köppen-Geiger system). It was invented in 1884 by Russian-German climatologist Wladimir Köppen (with later additions by climatologist Adolf Geiger). Like Rehder and Wyman at Harvard’s Arnold Arboretum, Köppen had worked in botany and used plant habitats extensively in developing it.
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The system relies on temperature and precipitation parameters to identify climatic zones. The system of three letters (with two special classifications for polar regions) results in 180 possible categories (though not all are used):
- Main climate
- Precipitation subgroup
- Temperature subgroup
Some examples. The southeastern United States is classified as Cfa: warm temperate, fully humid, hot summer. Central Australia is classified as Bwh: arid, winter dry, hot arid. Various classifications are applied to regions all around the world. Most of Scandinavia is classified as Dfc: continental, no dry season, cold summer.
The system is not static. Changes to the plots are made periodically, and can be tracked. As climatic data shows, there are not major changes in temperature or seasonality in the tropics or subtropics. And though variations happen all over the globe, the clear signs of warming occur in the far north, where the polar regions are gradually retreating.
The animated GIF showing 1976-1099 is based partly on data and mostly on a climatic model using the IPCC’s A1F1 emissions scenario, the most severe climatic impact with no mitigation, and it shows the steady northward migration of warmer zones all but overwhelming the current Arctic.
Even without 21st century predictions, the global zones are useful for predicting the spread of invasive species and pests (such as ticks), and helping predict other climatic impacts such as melting permafrost.
Animated Version of 20th Century Maps
Tomorrow: space weather.
Be brave, and be well.
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This post was previously published on Dailykos.com and is republished on Medium.
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