Fact-check log

The Met Office describes the Koppen climate classification as one of the most widely used systems of climate zones, dividing climates into five groups based on rainfall and temperature, including tropical climates (A). Met Office

Tropical climates, in Met Office wording, are close to the equator and have high temperatures and rainfall. Met Office

The Met Office finds tropical rainforest climates in South America, Africa and South-east Asia. Met Office

Lying either side of the equator, tropical rainforest climates are characterised by high temperatures and year-round rainfall. Met Office

Average temperatures are usually around 20-30 °C, with minor variation over the year. Met Office

Rainfall is over 60 mm of rain in every month, giving rise to thick rainforest and some of the highest densities of biodiversity seen on land. Met Office

Tropical regions also contain other climate zones, which are hot but have distinct dry seasons, unlike rainforests. Met Office

Tropical monsoon climates have a season of heavy rainfall, connected to a seasonal change in wind direction. Met Office

Tropical savannah climates have a more pronounced dry season than monsoon areas. They also have grasslands, rather than rainforests. Met Office

The Intertropical Convergence Zone, or ITCZ, is a band of low pressure around the Earth which generally lies near to the equator. Met Office

The trade winds of the northern and southern hemispheres come together here, which leads to the development of frequent thunderstorms and heavy rain. Met Office

These thunderstorms can reach, and sometimes exceed, 16 kilometres, 55,000 feet or 10 miles in height above the surface. Met Office

The resulting circulation, with air converging near the surface around the equator and diverging above, is known as the Hadley Cell. Met Office

The ITCZ moves throughout the year and follows the migration of the Sun's overhead position, typically with a delay of around 1-2 months. Met Office

In July and August, the ITCZ lies well to the north of the equator over Africa, Asia and Central America before moving south into South America, central Africa and Australia by January and February. Met Office

Another term for the ITCZ, used historically in seafaring circles, is the doldrums, since the winds along the band of low pressure are typically calm. Met Office

For countries nearer the equator, the Met Office says, seasons become defined by wetter or drier weather, as the temperatures vary little during the year. Met Office

Usually, countries located close to the equator with tropical climates have only two seasons, the dry season and the wet season. Met Office

During the wet season there is typically heat build up over the course of the day, allowing thunderstorms to grow and eventually produce rain in the afternoon, continuing overnight. Met Office

One of the most important biodiversity hotspots in the world, the Met Office says, is the Amazon basin. Met Office

The vast Amazonian system is large enough to modify its own weather and climate, which helps to perpetuate the rainforest and all of its dependent species, industries and communities. Met Office

That interconnected system faces the threat of effectively drying out, "tipping" this region from lush rainforest to a drier state of degraded forest or even savanna grassland. Met Office

Projections have shown that a combination of substantial deforestation in conjunction with climate change could be sufficient to set in train an irreversible path to one of these new states. There is uncertainty about just how quickly this could happen. Met Office

Ten per cent of the world's biodiversity is thought to exist within this region, in the Met Office's 2024 wording. Met Office

The Met Office has been actively involved in research in the Amazon for over 40 years. One current major project is AmazonFACE, funded jointly by the governments of the UK and Brazil, which studies the response of the forest to higher levels of carbon dioxide. Met Office

The rainforest biome remains warm all year and must stay frost-free. The average daily temperatures range from 20°C (68°F) to 25°C (77°F). NASA

NASA says rainforests receive the most rain of all of the biomes in a year, and that a typical year sees 2,000 to 10,000 millimeters (79 to 394 inches) of rain. NASA

There are two types of rainforests, tropical and temperate. Tropical rainforests are found closer to the equator where it is warm. Temperate rainforests are found near the cooler coastal areas further north or south of the equator. NASA

The tropical rainforest is a hot, moist biome where it rains all year long. NASA

It is known for its dense canopies of vegetation that form three different layers. NASA

The top layer or canopy contains giant trees that grow to heights of 75 m (about 250 ft) or more. This layer of vegetation prevents much of the sunlight from reaching the ground. NASA

The middle layer, or understory, is made up of vines, smaller trees, ferns, and palms. NASA

The bottom layer or floor of the rainforest is covered with wet leaves and leaf litter. This material decomposes rapidly in the wet, warm conditions, sending nutrients back into the soil. Few plants are found on the floor of the forest due to the lack of sunlight. NASA

A large number of plants from the understory are used as common houseplants, NASA notes, and the majority of common houseplants come from the rainforest. NASA

For Manaus, Brazil, NASA lists monthly precipitation from 1970-2000 that sums to 2,323 mm for the year, with April the wettest month at 310 mm and August the driest at 68 mm. Monthly average temperatures stay between 27°C and 28°C. NASA

The Amazon River runs almost 4,000 miles (about 6,400 km) across northern South America from the Andes to the Atlantic Ocean. NASA

It carries twenty percent of all river water discharged into Earth’s oceans, ten times the volume of the Mississippi River. NASA

If the Amazon River Basin were draped over the continental United States, NASA says, it would cover more than three fourths of the country. NASA

Surrounding the waters of the basin are over 2.7 million square miles (7 million square kilometers) of lush forest. NASA

A NASA Earth Observatory feature dated 31 December 2002, still on the page we checked, says that perhaps as much as one half of all life forms on the planet live in the Amazon River Basin, and later that the region supports perhaps half of all species on the planet. NASA

The Amazon Rainforest engages in a perpetual, self-watering cycle by storing and recycling at least one-half — some scientists think perhaps even two-thirds — of the regional rainfall. NASA

More than 9 feet (2.7 meters) of rain fall in portions of Amazonia each year, in that NASA wording. NASA

In fact, 75 percent of the energy that drives atmospheric circulation comes from the heat released during tropical rainfall. NASA

Located on the equator, Amazonia has a rainy season and a dry season, instead of the four seasons of temperate latitudes. The rainy season starts in the south in December, and gradually moves north through May. NASA

The Amazon rainforest experiences seasons, NASA says, but the changes are far more subtle: temperatures and sunlight remain pretty consistent year-round, but rainfall varies cyclically. NASA

Though there are regional variations, June through September are generally the driest months, and December through March are the wettest. While it still rains a significant amount all year, precipitation often drops by half from the wettest months to the driest. NASA

An analysis of geostationary satellite data found that Amazon forests were slightly greener, about 10 to 15 percent on average, during the dry season, because some trees put out an extra flush of leaves in anticipation of extra sunlight. NASA

While some recent findings indicate the Amazon rainforest may be close to becoming a source of carbon, it has generally functioned as an enormous carbon sink. NASA

The forest pumps huge quantities of water into the air through transpiration. That moisture fuels vast "flying rivers" and provides about half of the rain that falls back down on the region. NASA

The Amazon Basin covers 2,700,000 square miles (7,000,000 square kilometers), making it the largest drainage basin in the world. It occupies more than 40% of South America’s land area, and much of the basin is covered by dense tropical rainforest. NASA JPL

Each of the two predominant seasons, dry and wet, is approximately six months in duration. NASA JPL

The driest month in the Amazon Basin is August, when the average rainfall is approximately 2 inches (5 centimeters). During the wet season, rainfall is greatest from December to May, and can exceed 8 inches (20 centimeters) per month. NASA JPL

Over a year, the Amazon Basin averages an extraordinary 6 to 10 feet (1.8 to 3 meters) of rainfall. NASA JPL

The Amazon rainforest recycles much of the annual rainfall back into the atmosphere, and NASA JPL notes that the release of moisture back to the atmosphere hastens the onset of the wet season. NASA JPL

A rainforest, in Britannica wording, is a luxuriant forest, generally composed of tall, broad-leaved trees and usually found in wet tropical uplands and lowlands around the Equator. Britannica

Rainforests usually occur in regions where there is a high annual rainfall of generally more than 1,800 mm (70 inches) and a hot and steamy climate. The trees found in these regions are evergreen. Britannica

Rainforests may also be found in areas of the tropics in which a dry season occurs, such as the "dry rainforests" of northeastern Australia. In these regions annual rainfall is between 800 and 1,800 mm and as many as 75 percent of the trees are deciduous. Britannica

Tropical rainforests are found primarily in South and Central America, West and Central Africa, Indonesia, parts of Southeast Asia, and tropical Australia. Britannica

The climate in these regions is one of relatively high humidity with no marked seasonal variation. Temperatures remain high, usually about 30 °C (86 °F) during the day and 20 °C (68 °F) at night. Britannica

Where altitude increases along the borders of equatorial rainforests, the vegetation is replaced by montane forests, as in the highlands of New Guinea, the Gotel Mountains of Cameroon, and in the Ruwenzori mass of Central Africa. Britannica

Other kinds of rainforests include the monsoon forests, most like the popular image of jungles, with a marked dry season and a vegetation dominated by deciduous trees such as teak, thickets of bamboo, and a dense undergrowth. Britannica

Mangrove forests occur along estuaries and deltas on tropical coasts. Britannica

Temperate rainforests filled with evergreen and laurel trees are lower and less dense than other kinds of rainforests because the climate is more equable, with a moderate temperature range and well-distributed annual rainfall. Britannica

Most rainforest soils tend to be permanently moist and soggy. They are not very fertile, because the hot, humid weather causes organic matter to decompose rapidly and to be quickly absorbed by tree roots and fungi. Britannica

Rainforests exhibit a highly vertical stratification in plant and animal development. The highest plant layer, or tree canopy, extends to heights between 30 and 50 metres. Britannica

Most of the trees are dicotyledons, with thick leathery leaves and shallow root systems. The nutritive, food-gathering roots are usually no more than a few centimetres deep. Britannica

The next lowest layer of the rainforest is filled with small trees, lianas, and epiphytes, such as orchids, bromeliads, and ferns. Britannica

Contrary to popular belief, the rainforest floor is not impassable. The ground surface is bare, except for a thin layer of humus and fallen leaves. Britannica

The climate of the ground layer is unusually stable. The upper stories of tree canopies and the lower branches filter sunlight and heat radiation, as well as reduce wind speeds, so that the temperatures remain fairly even throughout the day and night. Britannica

Tropical rainforests, which worldwide make up one of Earth’s largest biomes (major life zones), are dominated by broad-leaved trees that form a dense upper canopy and contain a diverse array of vegetation and other life. Britannica

Contrary to common thinking, not all tropical rainforests occur in places with high, constant rainfall; for example, in the so-called "dry rainforests" of northeastern Australia, the climate is punctuated by a dry season, which reduces the annual precipitation. Britannica

Tropical rainforests grow mainly in three regions: the Malesian botanical subkingdom, from Myanmar to Fiji, including Thailand, Malaysia, Indonesia, the Philippines, Papua New Guinea and parts of tropical Australia; tropical South and Central America, especially the Amazon basin; and West and Central Africa. Britannica

Tropical rainforests represent the oldest major vegetation type still present on the terrestrial Earth. Britannica

The flowering plants (angiosperms) first evolved and diversified during the Cretaceous Period about 100 million years ago, when global climatic conditions were warmer and wetter than those of the present. The vegetation types that evolved were the first tropical rainforests, which blanketed most of Earth’s land surfaces at that time. Britannica

It is no surprise, therefore, to find the greatest diversity of flowering plants today in the tropical rainforests where they first evolved. Britannica

Tropical rainforests today serve as sinks for more than 50 percent of all atmospheric carbon dioxide absorbed by plants annually, and they exhibit unparalleled biodiversity. Britannica

The tropical rainforest of Africa was the habitat in which the ancestors of humans evolved, and it is where the nearest surviving human relatives — chimpanzees and gorillas — live still. Britannica

Not until the past century, however, has widespread destruction of tropical forests occurred. Tropical rainforests and tropical deciduous forests are now being destroyed at a rapid rate, Britannica says, to provide resources such as timber and to create land for other purposes, such as cattle grazing. Britannica

FAO's Global Forest Resources Assessment 2020 found that the world has a total forest area of 4.06 billion hectares, which is about 31 percent of the total land area. Those figures are for forests in general, not rainforest alone. FAO

Protecting forests is key to conserving natural resources, FAO says, as they harbour most of the Earth's terrestrial biodiversity and help mitigate climate change impacts. FAO

According to the State of the World's Forests report cited on the same FAO page, forests contain 60,000 different tree species, 80 percent of amphibian species, 75 percent of bird species, and 68 percent of the Earth's mammal species. Those figures are for forests, not rainforest alone. FAO

The global forest area continues to decrease, and the world has lost 178 million hectares of forest since 1990. However, the rate of net forest loss decreased substantially over the period 1990-2020. FAO

Africa had the largest annual rate of net forest loss in 2010-2020, at 3.9 million hectares, followed by South America, at 2.6 million hectares. FAO

In the five-year period 2015-2020, the annual rate of deforestation was estimated at 10 million hectares, down from 12 million hectares in 2010-2015 and 16 million hectares in 1990-2000. FAO defines deforestation as the conversion of forest to other land uses, such as agriculture and infrastructure. FAO