Climate Change

What is Climate Change?

A climate is the sum of the weather a place experiences over a number of years. Climate change occurs when there is a change in weather patterns. Such changes are usually small compared to the variability of the weather so can only be understood by studying weather statistics.

The Earth's climate is always changing - via the great difference between today's climate and the ice ages. Usually the changes are slow and there is time for life to adapt. Currently, however, the increase in greenhouse gases caused by human activity is causing much more rapid change with worrying implications.

What causes Climate Change?

The observed increase in globally averaged temperatures since the mid-20th century is very likely due to the increase greenhouse gas concentrations caused by burning fossil fuels (coal oil and natural gas) and deforestation. There are a number of greenhouse gases. The most significant is CO2.

The temperature of the Earth depends on the balance between radiation received from the sun and radiation which the Earth emits into space. Greenhouse gases absorb some of the infra-red radiation emitted by the Earth and reflect it back to the Earth's surface thus increasing the Earth's temperature until a point is reached where the inbound and the outbound radiation balance. The rise in the Earth's temperature causes changes in weather patterns and hence climate.

How does Climate Change affect us?

Changes in climate alter the temperature and precipitation. This can impact in Health, agriculture, energy use, water supply and the viability of eco-systems. Increasing temperatures also cause sea level rise.

- Health- Increase temperature and Air Pollution Related Diseases, such as malaria and asthma.

- Agriculture-Crop Losses: the crops we grow for food need specific conditions for temperature and water to grow. Climate change (global warming) can lead to extreme weather such as flood and draughts that may distroy the crops and lead to starvation and hunger.

- Increasing demand for energy - The temperature rise lead to a higher demand of air conditioning, which request for more energy and thus producing more greenhouse gases that will increase the temperature even more.

- Reduction of water supply may occur both due to changes in rainfall patterns and to increased seasonality of of river flue due to less rain being stored in mountain snows.

- Disappearing Habitats: changes in temperature and precipitation alter habitates and will drive some animals to extintion. For example coral reefs will be lost due to warmer water and increased ocean acidity (see below).This reduces habitats for many other sea creatures, and it will disrupt the food web in the ocean.

Increased greenhouse gas concentrations cause two other problems:

1. Sea Level Rise due to melting ice which is on land and to the expansion of water as it warms up.

2. Ocean Acidification: The oceans absorb carbon dioxide (CO2) which reacts with water to form carbonic acid. It makes the ocean more acidic. It affects marine animals with carbonate shells and skeletons.

A.B.

A. Marine lives (Source:GEO5)

B. Coral bleaching (Source: http://africanalchemy.wordpress.com/2010/07/26/fading-to-a-ghost-coral-bleaching/)

This diagram summarizes the impact of increased greenhouse gas emissions.

Source: US EPA

For more information on climate change and ocean acidification watch the following TED videos and click the websites:

James Hansen, Why I must speak out about climate change, TED Video
Rob Dunbar, Discovering ancient climates in oceans and ice, TED Video
Centre for Climate and Energy Solutions' Climate Change 101 - provides and introduction to climate change science
Real Climate - provides answers to questions asked by climate skeptics and others
Sustainable Energy without the Hot Air by Prof David McKay - provides what can be done to reduce carbon emissions