Climate Change Explained
Natural climate change
The climate of the Earth is not static and has changed many times over the billions of years of its existence. The various natural processes that affect the Earth's climate include the interactions between the ocean and the atmosphere, changes to the Earth's orbit around the sun, fluctuations in the energy received from the sun and emissions from volcanic eruptions. All of these affect the balance between the energy the Earth receives from the sun and the energy that is reflected off the Earth and lost back into space. This balance dictates the temperature and climate of the world.
The ‘Greenhouse Effect'
There are certain gases that have a major influence on the Earth's energy balance, these are known as ‘greenhouse gases' and include carbon dioxide, water vapour, methane and nitrous oxide. These greenhouse gases trap some of the energy reflected off the Earth and prevent it from escaping out to space, causing the atmosphere to warm. The gases act in a similar fashion as the glass of a greenhouse, hence the name ‘greenhouse effect'. This natural greenhouse effect keeps the Earth approximately 35oC warmer than it would otherwise be. Without it, the average global temperature would be -20oC and life on Earth would be very different!
Recent climate change
Recently the climate has been changing in unexpected ways and at an unexpected rate. Some examples of these changes are given below:
Global trends in the 20th century
- Average global temperatures increased by 0.6oC
- Sea-levels rose by 20cm
- A near worldwide decrease in sea-ice and mountain glacier extent was experienced.
UK trends:
- The UK is warmer now than at any time in the past 200 years.
- The 1990s was the hottest decade, in the warmest century, for the last millennium.
- Nine of the 10 warmest years on record were between 1995 and 2004.
- The hottest day ever recorded in the UK was on the 10 August 2003 when temperatures in Brogdale, Kent, reached 38.5 oC.
- July 2006 was hottest since records began.
Why is this happening?
Not all of these changes can be solely attributed to the natural climate variation described above. Over the last 200-250 years, since the industrial revolution, human activities have resulted in an increase in the level of greenhouse gases in the atmosphere. Atmospheric carbon dioxide alone has increased by 30% in this time and levels are currently at their highest for 800,000 years. Increased levels of greenhouse gases mean that more heat is trapped by the atmosphere, enhancing the greenhouse effect and causing the Earth to warm and the climate to change.
Image courtesy of the Climate Research Unit (CRU)
Where do greenhouse gases come from?
Human activities are increasing the levels of all greenhouse gases in the atmosphere. However, this website is going to concentrate on the most prevalent greenhouse gas -carbon dioxide. Carbon dioxide is released in much greater quantities than any other greenhouse gas and it is the one most affected by business activities.
6.5 billion tonnes of carbon dioxide are emitted annually from the burning of fossil fuels such as coal, oil and gas for energy production, transport and industrial processes. A further 1-2 billion tonnes are released due to deforestation to make way for agriculture, urbanisation and roads.
Internationally, the business sector is one of the largest emitters of carbon dioxide. In the UK, business emissions of carbon dioxide account for around 40% of total UK emissions.
