World Climate and Climate Change

Koeppen’s groups and codes of world climate, how climate changed in the past and why, greenhouse gases and global warming.

Key ideas

Koeppen’s empirical scheme links vegetation to temperature and rainfall: five groups shown by capital letters, with small letters for seasons.
Groups A, C, D and E are set by temperature; group B (dry climates) by precipitation.
Climate has changed before: warm periods long ago, Pleistocene ice ages, the Little Ice Age in Europe and warming since 1885.
Natural causes include changes in solar output with sunspots, Milankovitch changes in the earth’s orbit and tilt, and volcanic aerosols.
Greenhouse gases (carbon dioxide, methane, nitrous oxide, CFCs, ozone) let sunlight in but trap long-wave heat from the earth.
Forests and oceans are sinks that take in carbon dioxide; CFCs destroy ozone, causing the ozone hole over Antarctica.
Warming melts ice and expands sea water, raising sea level and threatening coasts and islands.

Group A (tropical)	coldest month 18 °C or more
Group C (warm temperate)	coldest month between −3 °C and 18 °C
Group D (cold snow forest)	coldest month −3 °C or below
Group E (cold)	every month below 10 °C
Small letters	f no dry season; m monsoon; w winter dry; s summer dry; S steppe; W desert
Examples	Af Amazon; Am India; Cs Mediterranean; Cwa north Indian plains; Cfb north-west Europe; EF Greenland interior
Steady rise	rise each year = per cent × amount ÷ 100; total = that × years
Key dates	Little Ice Age 1550–1850; warming from 1885; Koeppen’s scheme 1918; warmest year of the century 1998

Give the Koeppen group letter (A, C, D or E) for each humid place: (a) coldest −1 °C, warmest 7 °C (b) coldest −34 °C, warmest −4 °C

Working: A: coldest month 18 °C or more; C: coldest between −3 °C and 18 °C; D: coldest −3 °C or below; E: every month below 10 °C

Answer: (a) E (b) E