What a Af climate is like
Af Tropical rainforest. Rain falls in every month, so there is no dry season to speak of. Temperatures hardly change through the year, and the vegetation is dense evergreen forest.
The rules behind the code, in plain English:
- Tropical (coldest month 18 °C or more).
- Even the driest month gets 60 mm of rain or more.
Dataset wording: "Tropical, rainforest". In the maps of Beck et al. (2023) the class is written: A: Not B and Tcold >= 18; f: Pdry >= 60.
Tropical rainforest climate means hot, damp air all year, with rain falling in every month and no real dry season. Days feel much alike from January to December, so the seasons are marked more by how heavy the rain is than by temperature. Dense evergreen forest grows here, along with crops such as bananas, cocoa, palm oil and rubber. Homes tend to be raised, shaded and open to the breeze, and people wear light, loose clothes and carry an umbrella.
How much of the world is Af?
- 5.1%of the world's land outside Antarctica, 1991 to 2020
- 6,825,054 km²area, 1991 to 2020
- 1,506cities of 15,000 or more people (GeoNames) have this climate now
In 1901 to 1930 it covered 5% of that land, so its area then was 1.2% smaller than in 1991 to 2020.
How the Af area is projected to change by 2071 to 2099
These figures compare the area of Af 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) | 5% | -1.2% |
| 1991 to 2020 (now) | 5.1% | - |
| 2071 to 2099, SSP1-2.6 (low emissions) | 4.9% | -2.42% |
| 2071 to 2099, SSP2-4.5 (middle of the road) | 4.9% | -3.92% |
| 2071 to 2099, SSP5-8.5 (high emissions) | 4.8% | -4.19% |
Shares are of land outside Antarctica. A negative change means the zone shrinks.
What happens to today's Af land
Of the land that is Af in 1991 to 2020, this is how much stays Af and where the rest ends up in 2071 to 2099, by scenario:
| Scenario (2071 to 2099) | Stays Af | Where the rest goes (biggest first) |
|---|---|---|
| SSP1-2.6, low emissions | 94% | Am (5.7%) |
| SSP2-4.5, middle of the road | 91% | Am (8.5%) |
| SSP5-8.5, high emissions | 87% | Am (12%), Aw (0.5%) |
Looking back, 94% of today's Af land was also Af in 1901 to 1930. The rest was Am (4.2%), Cfb (0.8%).
Where Af is found
The countries with the most Af land in 1991 to 2020:
| Country | Area | Share of all Af | Share of the country |
|---|---|---|---|
| Indonesia | 1,577,500 km² | 23% | 85% |
| Brazil | 1,522,425 km² | 22% | 18% |
| Colombia | 604,835 km² | 8.9% | 53% |
| Democratic Republic of the Congo | 559,832 km² | 8.2% | 24% |
| Peru | 523,848 km² | 7.7% | 40% |
| Papua New Guinea | 360,063 km² | 5.3% | 78% |
| Malaysia | 320,719 km² | 4.7% | 98% |
| Venezuela | 241,958 km² | 3.6% | 26% |
Places with a Af climate today
The biggest cities in the 1991 to 2020 map that sit in Af (at most two per country):
Other tropical climates (group A)
Frequently asked questions
What does Af mean in the Köppen climate classification?
Tropical (coldest month 18 °C or more). Even the driest month gets 60 mm of rain or more. The code is a short way of writing that: the first letter is the major group (A, tropical) and the letters after it say more about rain and temperature.
What is a tropical rainforest climate like?
Hot, wet and green every month of the year. Rain falls in every month, so there is no dry season to speak of. Temperatures hardly change through the year, and the vegetation is dense evergreen forest.
How much of the world has a Af climate?
5.1% of the world's land outside Antarctica was Af in 1991 to 2020, about 6,825,054 km² (Beck et al. 2023, 1 km maps).
Will the Af climate zone grow or shrink?
Under the middle-of-the-road scenario (SSP2-4.5), the area of Af in 2071 to 2099 is 3.92% smaller 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.