Desiccation cracks in a mud puddle. Photo Jakob Owens.
Drought is caused by either cold or hot conditions. Many people living outside the extreme climate zones are unaware of the fact that the largest deserts on Earth are the Antarctic and the Arctic, the latter of which includes Greenland, northern Canada, northern Alaska, Spitsbergen, and parts of Iceland and northernmost Siberia. Life conditions are very hostile in these areas and the species diversity of plants and animals is extremely low due to the low temperatures and the lack of water. It takes very special adaptations to live on ice. In addition, severe storms generate a chill factor that can kill people in minutes.
The other large deserts are sand and rock deserts situated in warm climate areas, except for the Gobi and the Kalahari deserts. It is not the heat that make them deserts, it is the scarcity of rain. Without water, no life. The third largest desert is Africa's Sahara, about 3/4 of the size of Antarctica. The Arabian desert, in size only 1/5 of Antarctica, is number four.
A desert is defined as an area with less than 250 mm precipitation per year. With that definition, about 1/3 of all land is classified as desert. It is remarkable how thoughtlessly people in the high-income countries of the world use water. Water wars are to be expected when the medium-income countries follow suite. Lack of water presents a greater problem than global warming. My database includes 2074 pages about drought and heat in different geographical areas, seen in the table.
| DROUGHT-HEAT subregister (pages) | 1033 |
| Africa | 156 |
| Sahara Desert | 2 |
| Africa | 15 |
| Algeria | 7 |
| Angola | 2 |
| Burundi | 1 |
| Chad | 4 |
| Egypt | 18 |
| Eritrea | 1 |
| Ethiopia | 26 |
| Gambia | 1 |
| Ghana | 1 |
| Kenya | 10 |
| Libya | 3 |
| Mali | 2 |
| Mauretania | 1 |
| Mozambique | 1 |
| Morocco | 11 |
| Namibia | 1 |
| Niger | 2 |
| Nigeria | 2 |
| Rwanda | 1 |
| Sahel & North Africa | 9 |
| Senegal | 1 |
| Somalia | 2 |
| South Africa | 4 |
| Sudan | 13 |
| Tanzania | 4 |
| Tunisia | 6 |
| Uganda | 4 |
| Zimbabwe | 3 |
| America Central - West Indies | 10 |
| America North | 122 |
| America South | 40 |
| Antarctic | 3 |
| Arctic - Greenland | 37 |
| Asia | 604 |
| of which >5 | |
| China | 178 |
| Indonesia | 94 |
| India | 69 |
| Thailand | 41 |
| Asia | 35 |
| Sri Lanka | 25 |
| Vietnam | 24 |
| Burma | 21 |
| Israel | 19 |
| Japan | 16 |
| Cambodia | 16 |
| Near-Middle East | 16 |
| Iran | 10 |
| Syria | 10 |
| Uzbekistan | 10 |
| Kazakhstan | 9 |
| Philippines | 7 |
| Laos | 6 |
| Atlantic Islands | 3 |
| Australia | 13 |
| Europe | 1037 |
| of which >5 | |
| Sweden | 393 |
| Europe | 181 |
| Germany | 88 |
| Finland | 83 |
| Spain | 48 |
| England | 40 |
| Denmark | 40 |
| Italy | 36 |
| France | 31 |
| Norway | 31 |
| Iceland | 25 |
| Russia | 17 |
| Turkey | 14 |
| Switzerland | 12 |
| Netherlands | 11 |
| Poland | 7 |
| Austria | 6 |
| Ukraine | 6 |
| Indian Ocean | 2 |
| Mediterranean | 6 |
| Pacific Ocean | 1 |
| World | 37 |