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3.3.2A Human Induced or Anthropogenic Factors OR Climate Change due to Human Activities
Climate forcings* or factors that push the climate to change include both natural factors and human influences. Two key natural events and processes are the intensity of the sun reaching the earth and the concentration of volcanic dust that reflects light back into space. Some form of human activity is linked to all other changes in the composition of the atmosphere and to the surface reflection determined by land use.
Human influences forcing climate change i.e. increased global temperatures include changes in greenhouse gas concentration, stratospheric ozone depletion, local air pollution, and changes in land use which affect the albedo or reflectivity.
All of these affect both how much of the sun’s energy gets through to earth’s atmosphere and how much of the energy that is reflected back away into space. See 3.2.1 Global Energy and Albedo 3.2.6 and the rest of this section a to d.
The series of 3 graphs below analyze two global temperature increases separately for the period 1860 to 2000. The observed temperatures are compared to the modeled temperatures i.e. those calculated by climate models for the same period.
Natural factors used for climate modeling were the sun’s variations and volcanic activity. Anthropogenic factors used for climate modeling were greenhouse gases and estimated sulphate aerosols.
The natural caused, human-caused observations, along with the model results are then put together. This combination can provide some insight or understanding of underlying causes of the major temperature changes.
a) Graph with natural temperature changes. The observed i.e. recorded differences and modeled differences from the normal (anomalies) are seen below for 1860-2000
Natural factors used for climate modeling were the sun’s variations and volcanic activity.