Blanket Earth

The main idea for our climate change is the 'Enhanced Greenhouse effect'.

The Greenhouse effect

There is a naturally occurring layer of greenhouse gases in our atmosphere that have made the Earth warm enough for life to flourish.

http://www.livescience.com/37743-greenhouse-effect.html

As the diagram above already explain, people can effect the greenhouse effect. Humans can produce more greenhouse gases which means less infrared radiation escapes to space and therefore warming the Earth too much. Hence the 'Enhanced Greenhouse Effect'. As the Earth warms, the ice caps will melt which will create a rise in sea levels and therefore more flooding.

Greenhouse gases

The natural gases that contribute are: Water vapour, Methane, Carbon dioxide and Nitrous oxide and the only gas that is artificial that contributes are F-gases ( CFCs).
Water vapour is the most abudant greenhouse gas and also it acts as a feedback to the climate. As Water vapour in

creases the Earth warms, as does precipitation creating more Water vapour.

Carbon dioxide is the most important human greenhouse gas which is produced by burning fossil fuels (there has been a rise in CO2 levels since pre-industrial times) and deforestation.

Methane is the second most important greenhouse gas as it is produced by farming (especially cattle and rice), fossil fuel extraction and the decaying of organic waste.

Nitrous oxide is also produced from farming (fertilisers and livestock waste) and industrial processes which also produces F-gases along with refrigeration.

Solar Variability

Its reasonable to assume that the changes in the source's output would be the cause of our climate to change but the amount of energy that the Earth receives from the Sun is relatively stable, however variations occur such as the sunspot cycle ( approximately every 11 years) which result in increased magnetic activity which can be released as solar flares.

A case study that shows a decrease in solar activity is thought to have triggered the Little Ice Age between approximately 1650 and 1850, when Greenland was largely cut off by ice from 1410 to the 1720s and glaciers advanced in the Alps.

If you would like to find out more you can read this article (http://climate.nasa.gov/causes/) by NASA which explains about the contributing gases, the effect that burning fossil fuels has and solar variability.