A Geologists View of Climate Change

Global warming is real. Comparison of the two pictures (below) of the Rhone glacier in 1895 and 2010 shows just how much ice is melting and how fast. The ice that used to cover the slope of the mountain falling down towards the village of Furka simply isn't there any more, The ice is retreating by 7m per year.

Some global warming is natural - from a geologists point of view we are interested in the difference between the normal level and the current level. This difference is called the Enhanced Greenhouse Effect (EGE).


What the Syllabus Says - and the Details


A major cause of the EGE is carbon dioxide in the atmosphere (there are other causes; mostly methane). The major sources of carbon dioxide in the atmosphere are volcanic emissions and the burning of fossil fuels.

Currently, humans are attempting to reduce carbon dioxide emissions by the use of energy efficiency, renewable energy resources; hydroelectric, wind, geothermal (including heat engines) and by use of nuclear energy - which is non-renewable.

It is possible that, in the future, some of the carbon dioxide produced by power stations may be sequestered (stored by being pumped underground) in old oil/gas fields.

The enhanced “greenhouse effect” is a major contributor to global temperature increases. We can track this temperature rise with data for the past 140 years.

You need to be able to interpret data showing evidence for the increased rate of “greenhouse gas” emissions - such as working out the increase in average global temperature between 1860 and 2010 from the graph above.

There is evidence of increasing carbon dioxide, a major greenhouse gas, in the atmosphere from direct measurement and ice cores. We use ice the carbon dioxide content of the air trapped in ice at the poles to get data for the period before we actually started taking measurements. 

There are both positive and negative natural effects of the carbon dioxide content in the atmosphere. Positive effects speed up global warming, negative ones slow it down.

The melting of the ice-caps causes a reduction of icecap albedo (the ability of the ice to reflect heat and light from the Sun). As less heat is being reflected, more stays on the Earth. This causes the Earth's temperature to rise further - it gives accelerating warming.
On the other hand, carbon dioxide gets dissolved in sea water where it is used by plants for photosynthesis an by shellfish to produce their shells. When these shellfish die their shells can go on to form limestone. This locks away the carbon dioxide so it can't add to global warming. This is a negative effect on global warming - but not a big enough one, as can be seen from the graph of carbon dioxide in the atmosphere above.

Global warming affects continental ice sheet dimensions. As the atmosphere warms up, the ice melts so the ice sheets shrink. The maps below show how the Arctic is failing to keep more and more of its 'older ice' through the summers.

As the Earth warms, some elements of weather become more extreme and unpredictable. We see this happening in the forms of; windier weather (including more hurricanes), wetter weather due to more evaporation from the oceans and also by the shifting of weather patterns due to alterations of the temperature patterns in the atmosphere.

Global warming also affects global sea level. As yet, sea level changes don't seem that large, except it takes a vast amount of melted ice to raise the sea level across the whole world by the 20cm rise shown in the graph below.

There is good evidence of global sea level change during Pleistocene glaciations on a much larger scale than the current levels. There have been rises in sea level as shown by submerged forests and drowned valleys and falls in sea level as shown by raised beaches.

Raised beaches - beach areas which are no longer at sea level and have grown grass etc on top of them - as shown in this picture of Langerstone Point.

Submerged forests - forests that have been flooded by the sea due to rises in sea levels since they started growing. The one below is at Borth in Wales.

Drowned valleys form where an increase in sea level floods the bottom of a valley near the sea. The map below shows how the sea has 'invaded' a number of valleys in eastern China.

You need to be able to use maps, photographs, and diagrams to identify the characteristics of these three features. Be careful with your explanations though - isostasy is responsible for most raised beach and submerged forest features in Britain.