What a Csa climate is like
Csa Hot-summer Mediterranean. The classic Mediterranean pattern: summers are dry and hot, and the rain arrives in the milder months. Olives, vines and citrus do well.
The rules behind the code, in plain English:
- Temperate (coldest month between 0 °C and 18 °C).
- Dry summer: the driest summer month gets under 40 mm and under a third of the wettest winter month.
- Hot summer: the warmest month averages 22 °C or more.
Dataset wording: "Temperate, dry summer, hot summer". In the maps of Beck et al. (2023) the class is written: C: Not B and Thot > 10 and 0 < Tcold < 18; s: Psdry < 40 and Psdry < Pwwet/3; a: Thot >= 22.
Hot-summer Mediterranean climate has long, dry, hot summers and mild, wetter winters. Skies are sunny for much of the year, and the rain comes mostly in autumn and winter. Olives, vines, citrus fruit, figs and cork oak thrive, and the hills are covered in drought-hardy scrub. Homes use thick walls, shutters and shaded courtyards to stay cool, and life moves outdoors on summer evenings.
How much of the world is Csa?
- 1.2%of the world's land outside Antarctica, 1991 to 2020
- 1,677,599 km²area, 1991 to 2020
- 2,096cities of 15,000 or more people (GeoNames) have this climate now
In 1901 to 1930 it covered 1.1% of that land, so its area then was 9.37% smaller than in 1991 to 2020.
How the Csa area is projected to change by 2071 to 2099
These figures compare the area of Csa in each future map with 1991 to 2020. They come from the Beck et al. (2023) model projections under three emissions scenarios. They show what the scenarios imply, not what will happen.
| Map | Share of land | Change in area vs 1991 to 2020 |
|---|---|---|
| 1901 to 1930 (past) | 1.1% | -9.37% |
| 1991 to 2020 (now) | 1.2% | - |
| 2071 to 2099, SSP1-2.6 (low emissions) | 1.5% | +19.99% |
| 2071 to 2099, SSP2-4.5 (middle of the road) | 1.6% | +27.98% |
| 2071 to 2099, SSP5-8.5 (high emissions) | 1.8% | +42.46% |
Shares are of land outside Antarctica. A negative change means the zone shrinks.
What happens to today's Csa land
Of the land that is Csa in 1991 to 2020, this is how much stays Csa and where the rest ends up in 2071 to 2099, by scenario:
| Scenario (2071 to 2099) | Stays Csa | Where the rest goes (biggest first) |
|---|---|---|
| SSP1-2.6, low emissions | 90% | BSh (4.2%), BSk (4.2%), Aw (0.7%), Cfa (0.6%) |
| SSP2-4.5, middle of the road | 82% | BSh (9.7%), BSk (6.9%), Aw (0.8%) |
| SSP5-8.5, high emissions | 68% | BSh (24%), BSk (6.3%), Aw (0.8%) |
Looking back, 75% of today's Csa land was also Csa in 1901 to 1930. The rest was Csb (13%), Dsa (4.3%), BSk (3.1%), Dsb (1.9%), Cfa (1.4%).
Where Csa is found
The countries with the most Csa land in 1991 to 2020:
| Country | Area | Share of all Csa | Share of the country |
|---|---|---|---|
| Turkey | 308,014 km² | 18% | 40% |
| Spain | 192,169 km² | 11% | 38% |
| United States | 142,111 km² | 8.5% | 1.5% |
| Italy | 126,718 km² | 7.6% | 42% |
| Morocco | 98,953 km² | 5.9% | 17% |
| Iran | 98,445 km² | 5.9% | 6.1% |
| Greece | 86,859 km² | 5.2% | 67% |
| Algeria | 78,720 km² | 4.7% | 3.4% |
Places with a Csa climate today
The biggest cities in the 1991 to 2020 map that sit in Csa (at most two per country):
Other temperate climates (group C)
Frequently asked questions
What does Csa mean in the Köppen climate classification?
Temperate (coldest month between 0 °C and 18 °C). Dry summer: the driest summer month gets under 40 mm and under a third of the wettest winter month. Hot summer: the warmest month averages 22 °C or more. The code is a short way of writing that: the first letter is the major group (C, temperate) and the letters after it say more about rain and temperature.
What is a hot-summer mediterranean climate like?
Dry, hot summers and mild, wetter winters. The classic Mediterranean pattern: summers are dry and hot, and the rain arrives in the milder months. Olives, vines and citrus do well.
How much of the world has a Csa climate?
1.2% of the world's land outside Antarctica was Csa in 1991 to 2020, about 1,677,599 km² (Beck et al. 2023, 1 km maps).
Will the Csa climate zone grow or shrink?
Under the middle-of-the-road scenario (SSP2-4.5), the area of Csa in 2071 to 2099 is 27.98% larger than in 1991 to 2020. This is a model projection, not a forecast, and it differs under other scenarios (see the table on this page).
Data: Beck et al. (2023), CC BY 4.0. See data sources and licences. Köppen-Geiger classes describe long-term averages, not weather.