Global Warming

What is Global Warming?

Carbon dioxide is one of a number of gases in our atmosphere that are known as 'greenhouse gases'.  The sun’s rays (made up of UV and Infra-red (IR) rays) pass through the atmosphere and warm the surface of the Earth.  These rays are reflected out into space again. Greenhouse gases such as carbon dioxide absorb some IR rays from the sun, and reflect them back towards the Earth, warming up the atmosphere and the Earth's surface.  These gases are needed as without them the surface temperature would be approximately 33^oC colder than it is now making it highly unlikely that plant and animal life would survive.

The Carbon Cycle

 

The carbon cycle is a naturally occurring process where carbon dioxide is removed from the atmosphere by organisms (such as plants) undergoing photosynthesis:

 

 

carbon dioxide  +    water     ---------->    glucose            +   oxygen

6CO₂(g)       +    6H₂O(l)   ---------->    C₆H₁₂O₆(s)         +   6O₂(g)

The carbon is trapped in the plant as glucose, this carbon can be transferred to animals when plants are eaten.

 Both plants and animals use glucose as a source of energy in the process of respiration:

glucose        +     oxygen  ---------->    carbon dioxide      +   water

C₆H₁₂O₆(s)    +     6O₂(g)    ---------->    6CO₂(g)                  +   6H₂O(l)

This (along with decomposition of plants and animals when they die) releases carbon dioxide back into the atmosphere.  This is not a problem as the amount carbon dioxide released is the same as the amount taken in when the plants grew originally, so the process can be considered ‘carbon neutral’.

 

On this basis carbon dioxide levels in the atmosphere would be sufficient to maintain a temperate climate.

Why is Global Warming an issue?

The problem exists in the combustion (burning) of fossil fuels.  Fossil Fuels contain carbon that was trapped millions of years ago.  This releases extra carbon dioxide into the atmosphere, which is not part of the natural carbon cycle.

 

This carbon dioxide absorbs more IR rays from the sun reflecting them back towards the Earth's surface, increasing the surface temperature.  This process is known as global warming, the video below describes the process:

 

 

Issues with Global Warming

As the surface temperature of the Earth increases a number of problems occur, many of which are linked together:

• Polar ice caps melt more quickly – sea levels rise, causing flooding in low lying coastal areas. Destroying habitats in both of these regions.

• Climate changes – Temperature rises will cause increased rainfall in some areas, tropical storms and flooding, yet in other areas would cause drought.