EVIDENCE FOR PAST CLIMATE CHANGE, IS CURRENT CHANGE HUMAN INDUCED?
Climatologists have used proxy data to determine various factors affecting climate systems in the past. Instrumental measurements of wind, rainfall, humidity, aerosol (atmospheric), and gaseous composition can be used to understand how these factors all contributed to the climate in the past. Temperature tells us exactly how much energy a system has and this is an important factor telling us or giving us information about the past climatic conditions. Proxy data such as Geological, Glacial assessments and sediments be it terrestrial or marine, organic or inorganic are all good resources of information of the past climatic conditions.
The evidence that we have that climate change has taken place from now compared to the past is the change in temperature, glaciers retreating, an increase in sea levels and dissociation and integration of the icesheet. The temperature has increased climatically in some areas and is said to be due to the industrial revolution resulting in global warming owing to the increase in green house gasses namely methane, carbon dioxide, ozone and nitrous oxides. Permafrost which is water which is in the soil water (H²O) that is frozen all year long now has formed large potholes and the frozen bottom of the rivers now flow away, is also another event that shows us air climate has changed.
Glaciers are said to have decreased in surface area now, because when glaciers are measured then we look at the total or net loss/gain divided by the surface area of the glacier. Size and mass are two separate means of measurements used to determine if climate change did occur. When the Larsen-B ice shelf disintegrated, it lost 3250km² when looking now at the shelf it has lost 5700 squared kilometers in total. Four other glaciers have said to melt as well and now the total amount of area of sea ice lost is 13500km squared. The amount of melting taking place or which has taken place over the years can be seen through satellite images. This melting is due to temperature changes owing to global warming. The sea level has increased by 15cm.
Sea ice as well has also started to melt but this does not contribute to sea levels. The melting of sea ice does contribute for the salinity status or profile of water columb (ocean) and also the frequency interactions of glaciers to the open ocean.
Low laying areas such as Bangladesh affected by melting owing to them having flat planes and could suffer because of the increasing sea levels. This melting is influenced by temperature changes.
The increase of the composition of the gases within the atmosphere contributes to the changes in the amount of solar radiation levels that will penetrate our earth. It is said that because of out burning of fossil fuels we are increasing the greenhouse gases within air atmosphere. These greenhouse gases actually absorb all the long wavelengths that were produces by ozone which converts the short wavelengths radiated by the sun. The greenhouse gases then absorbs these long wavelengths and causes an increase in temperature. This increase in temperature may allow certain areas to become hotter and other areas to become colder. Because of us burning fossil fuels we are therefore responsible for this climate changes that has taken place.
Some activities or occurrences were natural but we by out activities are speeding up these processes and are therefore partially to blame.
Biodiversity and Conservation Biology Department
University of the Western Cape