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
within a stable range capable of maintaining life.
The swings in the Earth's temperature and weather which we complain about so often are very small and mild when compared to the climates on other planets. Our weather and temperature are both
controlled by the presence of greenhouse gases. If we increase
the amounts of these gases then more of the sun's heat will be trapped 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 planet Earth.
Over the last 150 years the amount of carbon dioxide in the atmosphere
has more than doubled. This is mainly due to:
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. Some scientists believe that this increase
in temperature is one of the main drivers for climate change and could cause:
- the burning of fossil fuels such as coal to generate electricity, gas for heating homes and industry and petrol and
diesel which is burned as a fuel for transport in motor vehicles, trains etc.
- Wide spread deforestation also releases large amounts of CO2 into the atmosphere and prevents 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.
- Cows release, either by burping or farting,
up to 300g of methane per day and there are 987 million cows on Earth. 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 the growing of rice in paddy fields also releases large amounts of methane gas into the atmosphere. Here slow
moving water with low oxygen levels contain bacteria which produce large quantities of methane gas.
- melting of the ice-caps and cause widespread flooding
- 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.
- 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 bound 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 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. There
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 lower the pH and can harm many
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 n increase in the rate of global warming.
How does the Greenhouse effect work?
The Sun emits short wave infrared radiation which provides the warm needed for life to thrive on Earth. The short wave
infrared emitted by the Sun is able to pass through the atmosphere and warm the land and oceans. When the 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 warms
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 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 the 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 economy. 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 and they argue that the
Earth has gone through natural periods in the past where average temperatures have risen and fallen. It is difficult for
scientists to model such a complex system as the Earth's weather and climate. This leads to simplified models and 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 burning fossil fuels, agriculture, food production and many industrial processes are increasing
the amounts of greenhouse gases into the air. Greeenhouse gases
are gases which trap
the infrared radiation (heat) from Earth and prevent it from escaping 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.