The past – impact of volcanic explosions on climate
Ice ages and hot periods – why
The milankovitch cycles are the frequent and regular changes in the way the earth orbits the sun, meaning that there are consistent sequences of ice ages and warm periods. Its orbit moves from being a circular movement around the sun to a slightly elliptical rotation path. The angle of the Earth’s axis also changes fractionally, occurring every forty-one thousand years. Finally, the direction of the tilt of the axis moves towards or away from the sun every twenty-six thousand years. These changes influence the length of the seasons and the amount of solar radiation received by the earth.
One possible explanation of this effect is the amount of land mass which is pointed towards the sun. In the Northern hemisphere, there is a significantly larger amount of land, and therefore vegetation. As this section of the Earth points in the direction of the sun and therefore receives more solar radiation, this vegetation absorbs more CO2; reducing the amount in the atmosphere. This results in the lowering of average temperatures.
When the opposite occurs plants release CO2, meaning average temperatures increase. This results in the rising temperature of the ocean, which leads to more frequent and severe storms – for example, hurricane Katrina was heated and fuelled by the hot, moist air in the Gulf of Mexico. The heating of the oceans also leads to ice caps/glaciers melting. Evidence of this occurs in Antarctica, where a huge section melted in just thirty-five days. The ice once served as a reflective surface; reflecting the sun’s solar waves back into the atmosphere (albedo effect). Now, however, as the ice is no longer there, the ocean absorbs these rays and heating the surrounding water.
Evaporation also dramatically increases, leading to heavier rainfall and flooding in certain areas. Evaporation also increases in dry areas, where soil moisture is removed. This leaves these particular areas, such as Northern Africa, in draught. This in turn leads to lack of resources and food for indigenous people, causing other human problems.
Another reason for the increasing temperatures is the greenhouse effect. As solar waves from the sun beat down to the Earth’s surface, some are reflected back into the atmosphere as infrared radiation. Here, however, greenhouse gases such as CO2 and water vapour trap these rays, causing the layer around the Earth to gradually heat.
Many people believe that human impacts are making this situation worse. The continuing burning of non-renewable sources such as fossil fuels to provide energy for dense populations increases the amount of CO2. This is also a result of deforestation as the burning of trees and plantations also causes the release of CO2.
Impacts on the UK and the whole globe have been predicted
Predicted impacts on climate change – UK and globally / already – loss of species / mosquitioes move to higher altitudes = increase diseases
Conclusions – were USA right not to sign the Kyoto agreement? Why?
Some predicted Future Effects of Climate Change