7.9.+Causes+of+Climate+change

= 9. What are the causes of climate change? = The drivers of climate change is the greenhouse effect. This is made up of 2 components, the natural greenhouse, without which there would be no life on earth, and the enhanced greenhouse effect which has been largely caused by human behaviour. The natural greenhouse effect means that we do not getting widely varying surface temperatures as some of the other planets do, so that living things can survive. This animation explains really well how it works @http://news.bbc.co.uk/1/shared/spl/hi/sci_nat/04/climate_change/html/greenhouse.stm The small quantities of CO2, methane, ozone etc, trap heat that reaches into our atmosphere from the sun The sun's radiation travels through space. As it approaches earth, some is reflected back out into space but most of it is absorbed by the earth, which warms the surface. Some of this heat is re-radiated as infra-red this time, into the atmosphere. Some of the infra-red is radiated out into space, but greenhouse gases absorb some of this and trap it, maintaining the warmth of Earth even when the sun is not shining on that part of the earth. Where the **g**reen**h**ouse **g**ases (**GHGs**) remain stable and at their natural level, then the climate also remains stable. However, if for some reason, the level of GHGs becomes disturbed, then the climate too becomes unpredictable. It can be seen fairly clearly that the levels of GHGs are changing, and most people believe it is human behaviour that has caused this.

This diagram shows exactly who is emitting GHGs and how much - worth a look:

So what are the causes of changing levels of GHGs?
As can be seen, over the past 100 years all 3 of these have been increasing significantly. Remember that while CO2 is the most prolific, methane ( X 21 to X 30 CO2) and nitrous oxide (X300 CO2) are much more dangerous mass for mass. Look at the graph below, and the average world temperature has increased over about the same period. OK we have to be dubious about the use to scale so that the graphs possibly match more than they should do - but as one goes up, the other seems to. Now increase in temperatures do not causes more gases to be emitted - human development does that, so we need to strongly consider just how influential human activity is in creating those rising temperatures.

The other 2 issues we need to look at is which countries are contributing the most and what activities are causing the biggest problems?



From these graphs you should be able to write a clear enough summary that explains (a) the link between temperature rise - one symptom of climate change (b) Which countries have the longest history of adding to GHGs and who are the current major emitors (c) Where do the GHGs come from (d) The role of the different GHGs in the total emissions

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