Global Systems
- Human Influence on Climate

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Is the Earth Warming?

All indications are that the earth is warming. In 2007 the Intergovernmental Panel on Climate Change (IPCC) reported the following evidence for global warming.

• Increases in global average air and ocean temperatures
• Widespread melting of snow and ice
• Rising global average sea levels

The Enhanced Greenhouse Effect

It is difficult to identify the exact effect of changes caused by humans because

• The relative short time we have been keeping records about climate (just over 100 yrs )
• Trends that drive climate change take much longer than this

The enhanced greenhouse effect is the increase in greenhouse effect supposedly caused by man.
Scientist believe that if the current rate of CO2 production remains at 2000 levels there will be an increase in global average temperature of 0.1oC per decade

Carbon Dioxide in the Air

It is estimated that humans only produce about 5% of the carbon dioxide in the air. The largest source is natural decay.

The theory is that carbon sinks balance the natural carbon dioxide levels produced. A carbon sink is a place or event that removes carbon dioxide from the atmosphere .

Since the Industrial Revolution it is believed the amount of carbon dioxide in the atmosphere has gone from 280 ppm to 391 ppm.

Methane

Methane can trap more than 20 times more heat than the equivalent mount of carbon dioxide. It is produced from the breakdown of organic matter. Sources are:

• Stomach of cows and sheep
• Rice paddies
• Garbage tips
• Coal mines
• Natural gas fields
• Methane trapped in permafrost

The amount of methane in the atmosphere is more than double that before the industrial revolution.

Nitrous Oxide

N2O is 200x better at trapping heat than CO2.  It is about 18% higher than before the industrial revolution. It comes from

• Car exhausts
• Some Industrial processes
• Burning of forests
• Use of nitrogen fertilisers

Loss of Ice

Some evidence to suggest Ice in Antarctica is not getting as large in the winter. This reduction in ice leads to heating effects by:

• Less heat reflected back into space
• More heat added to atmosphere from the ocean (more surface of water not covered by ice)
• Not as much dense (salted) water sinking and driving the “ global conveyer belt ”

Carbon dioxide absorption

CO₂ is absorbed at the surface of the water.  As water sinks it takes the CO₂ with it into the “global conveyer belt”

Shrinking Antarctica

Evidence suggests that the ice mass of Antarctica is changing ( reducing )

 

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