Higher and foundation tier
The Greenhouse effect
Without the natural Greenhouse effect the
Earth would be too cold for life. Scientists estimate that the
Earth would be some 180C
colder without this natural warming effect. The small amount of
carbon dioxide and
other greenhouse gases such as methane and water vapour in the
atmosphere act like a blanket and trap enough of the sun's heat to keep the
temperature on our planet
within a stable range capable of maintaining life.
The swings in the Earth's temperature
and weather which we often complain and moan about so often are very small and mild when compared to
the climates on other planets. Our weather and
temperature in our atmosphere are both
controlled by the presence of certain greenhouse gases. If we increase
the amounts of these gases then more of the sun's heat will be trapped
in the atmospher and temperatures
on Earth will start to rise. This
warming of the Earth can lead to climate change which can have a huge affect on all life on our planet.
Over the last 150 years the amount of the greeenhouse gas
carbon dioxide in the atmosphere
has more than doubled. This is mainly due to:
- the burning of fossil fuels such as coal to generate
electricity as well as the burning of natural gas to
heat homes and industry.
- The burning of petrol and diesel as a fuel for transport in motor vehicles, trains etc.
- Wide spread deforestation also releases large amounts of CO2
into the atmosphere and also prevents the removal
of CO2 by photosynthesis. The clearing of forests to make way for farming also has a large impact on the
amount of CO2 released as farming is an energy intensive activity.
Large areas of forest are being cleared in countries like Brazil to make way for cattle and to produce large amounts of timber to sell which boasts their economies and provides jobs.
- Cows release, either by burping or farting,
up to 500 litres of methane per day and there are approximately
987 million cow on Earth.
Scientists have estimated that cows alone release just over 3 gigatonnes (3 billion tonnes) of
methane into the atmopshere every year; and this amount is growing year upon year.
Methane is up to 28 times as effective at trapping
the Sun's heat in the atmosphere
as carbon dioxide gas. The increase in the food requirements of a
growing world population
means more farming
which ultimately means less forests and more cows. This cycle leads to an increase in both methane and carbon dioxide concentrations in
- In Asia rice is a major part of people's diet. The growing of rice in paddy fields also releases large amounts of
methane gas into the atmosphere. The paddy field used to grow rice contain lots of slow
moving water with low oxygen levels, this water contain bacteria which produce large quantities of methane gas.
The carbon dioxide and other gases such as methane
are able to trap more of the sun's
heat in the atmosphere, this has seen average global
temperatures rise. Many scientists believe that this increase
in temperature is one of the main drivers for
climate change and could cause:
- melting of the ice-caps and cause widespread
- change the planet's climate, in Britain we could see
more stormy wet winters and dry summers, with droughts and other extreme weather
patterns becoming more common.
Many plants and animal species may die out and become extinct simply because they will be unable to adapt to their new environment
e.g. Beech trees are tall trees with fairly shallow roots, and this shallow root system means they cannot tolerate
prolonged hot dry conditions such as those which are likely to be present in a world experiencing global warming.
- Some scientists believe that global warming may alter or change
hot water ocean currents that bring hot water
from the tropics to the cooler parts of the northern and southern hemispheres. If
these hot water currents stop or retreated further south then global
warming could actually put large areas of the Earth in an ice-age. e.g.
There is a warm water ocean current called the
Gulfstream which brings hot water from the Gulf of Mexico to warm the northern hemisphere, including Britain.
is evidence that the amount of hot water carried by the Gulfstream is reducing and it may even stop altogether.
- As carbon dioxide levels rise more of it will dissolve in the ocean. This
will acidify the oceans and seas which will have a lower pH. This will harm many
aquatic plants and other organisms living in marine environments. Rising sea
temperatures can also have dramatic affects on many marine
organisms e.g. rising sea temperatures can put enormous stress on corals, living in coral reefs. The rising temperature stress
the coral and this causes them to expel their algae. This results in coral bleaching, where the coral loses their colour.
This leaves the coral open to disease and may result in the coral dying. However as the
seas and oceans warm their ability to dissolve
carbon dioxide decreases, this will ultimately lead to an increase in
CO2 levels in the atmosphere and an increase in the rate of
How does the Greenhouse effect work?
The Sun emits short wave infrared radiation
which provides the warm needed for life to thrive on Earth. This
infrared emitted by the Sun is able to pass through the
atmosphere and warm the land and oceans. When the hot land and sea
cool back down you might expect the infrared (heat) radiation
they give off to escape back into space, however they emit
infrared radiation of a longer wavelength
which certain gases such as carbon dioxide,
methane and water vapour trap and
stop it from being emitted into space. The end result is that the heat
is trapped in the atmosphere - The Earth
up, this is the Greenhouse effect.
Time to act?
Since the industrial revolution,
over 180 years ago the average global temperature has risen by about 1.10C. This might
not sound like much but many scientists are worried that if the temperature rises by 1.50C then many of the ecosystems
on Earth could become permanently damaged, there could be widespread climate change
with severe flooding and droughts
with more severe and frequent storms/hurricanes/typhoons and the possibility of wide spread impacts on water and food
production. Many plants and animals
will not be able to adapt or change their behaviour to deal with this new climate
and will ultimately through loss of habitat and food become extinct.
Many countries have agreed to cut their emissions
of carbon dioxide gas in order to try and prevent further warming. However not all countries have signed up to this
pledge, indeed some of the largest producers of greenhouse gases are refusing to cut their emissions in case it damages
their economies. At the COP 26 in Glasgow some countries want to delay cutting their emissions until later in this century. With the havoc caused by the Covid-19 pandemic it remains unclear as to how many governments will react in order
to revive the economies of their countries. Some campaigners are hoping that a new "world" might emerge following Covid where
there could be a green revolution and the accelerated introduction of new greener and less polluting technologies in an attempt to reduce
the effects of climate change.
It is important to realise that not everyone agrees that the Greenhouse effect is actually real; there is a small group of scientists who argue that the
Earth has gone through natural periods in the past where average
temperatures have risen and fallen over time. They would say that it is difficult for
scientists to model such complex systems as the Earth's weather and climate. This leads to simplified models, opinions
and data which not everyone agrees with. As a scientist you should consider all the facts available and not be swayed by
the media or accepted opinion, other people and organizations may have their own agenda which they wish to push, which
could result in them twisting or distorting the facts. You need to consider all the information from all available
sources before making up your own mind!
- Human activity such as the burning of fossil fuels, agriculture, food production and many industrial processes are increasing
the amounts of greenhouse gases into the atmosphere. Greeenhouse gases
are gases which trap
the infrared radiation (heat) from the sun and prevent it from escaping back into space.
Carbon dioxide, methane and water vapour
are all good greenhouse gases.
- Rising temperatures due to the Greenhouse effect or global warming can affect the weather and climate of planet
- Rising temperatures can result in:
- ice-caps at the poles melting, this will result in sea levels rising and cause widespread global flooding.
- As the planet warms this will lead to weather patterns changing. Some areas will get more rain while others will become
drier. There is likely to be more storms, droughts, floods and heatwaves. Plant and
animal species may become
extinct due to the fact they are unable to survive in fast changing habitats.
- Some scientists believe that global warming may even trigger an ice-age.