FIND OUT MORE. Habitats 82–84 • Human Impact 64–65 • Winds 51
The Earth has three main climate zones – tropical,
temperate, and polar. These zones can be divided further
into smaller zones, each with its own typical climate.
A region’s climate, together with its physical
characteristics, determines its plant and animal life.
HAS THE EARTH’S CLIMATE CHANGED OVER TIME?
Over the past two million years, the Earth’s climate
has slowly changed. Long, cold periods called ice
ages, or glacials, have been interspersed with warmer
periods. The last glacial ended about 10,000 years
ago. At its height, all of northern Europe and parts
of North America, Siberia, New Zealand, Tasmania,
and the southernmost tip of South America were
covered by ice sheets up to 1,000 m (3,280 ft) thick.WHAT IS A MICROCLIMATE?
A small area with a different climate to its surroundings
is said to have its own microclimate. Examples include
a city or a rooftop garden. The air temperature in cities
may be 6 ̊C (11 ̊F) warmer than the surrounding
countryside because buildings and paved streets hold
the Sun’s heat longer than vegetation. Artificial heating
in buildings also contributes to higher city temperatures.
1 EARTH’S MAJOR CLIMATE ZONES
These are many ways to classify climate. Most methods (including the
one shown here, which divides the Earth’s surface into nine different
climate zones) use a combination of temperature and rainfall.POLAR AND TUNDRA
Polar climates are cold and dry,
with long, dark winters. In the
tundra (a treeless region bordering
the Arctic), temperatures only
rise above freezing for a few
months each year.DESERT
The Earth’s deserts are hot and dry
all year round, and usually receive
less than 250 mm (10 in) of rainfall
a year. Deserts form inland in Asia
and Australia but not so much
elsewhere where other factors
come in to play.TROPICAL GRASSLAND
Tropical grasslands, such as the
African savannah, lie between
desert areas and tropical
rainforests. The climate is hot all
year round, but with a distinct
wet season and dry season.BOREAL FOREST
Boreal (cold coniferous) forests lie
south of the tundra, stretching
across much of northern Canada,
Scandinavia, and Russia.
Temperatures fall below freezing
for 4–6 months a year.MOUNTAIN
On mountains, the temperature
decreases with altitude (height)
and many high peaks are always
covered in snow. Mountain
climates are usually wetter and
windier than lowland regions.DRY GRASSLAND
Dry grasslands are found in the
centre of continents where
temperature variations are
extreme. They have hot summers,
cold winters, and little rainfall, so
very few trees can grow there.TROPICAL RAINFOREST
Rainforests are found in tropical
regions near the Equator. Here,
the climate is hot and wet all
year round, with temperatures
remaining at around
27–28 ̊C (80–82 ̊F).MEDITERRANEAN
A Mediterranean climate is
found in regions bordering
the Mediterranean Sea, and in
Australia and California, USA.
It is characterized by hot, dry
summers and cool, wet winters.TEMPERATE FOREST
Temperate climates have warm
summers and cool winters with
rain all year round. Temperate
forests are characterized by
deciduous trees, which lose their
leaves during the winter.Climate Zones
CLIMATE ZONE CLASSIFICATION
POLAR AND TUNDRA
BOREAL FOREST
MOUNTAINWILL THE EARTH’S CLIMATE CHANGE IN FUTURE?
Some scientists believe that the Earth will enter
another ice age in thousands of years. However, all
scientists believe that pollution caused by human
activities is slowly causing the planet to grow
warmer – a phenomenon called global warming.TEMPERATE FOREST
MEDITERRANEAN
DESERTDRY GRASSLAND
TROPICAL GRASSLAND
TROPICAL RAINFORESTLOUIS AGASSIZ
Swiss, 1807–1873
Naturalist Louis Agassiz
studied glaciers and the
effects of ice erosion in
areas where glaciers no longer
existed. He put forward the
theory that much of Europe
and North America was once
covered by ice sheets.
Through his work, the
idea of “ice ages” became
generally accepted.climate
zones