Global Warming Part 2

The human causes of global warming have been in the news a lot in recent years - you can probably think of a few examples. Human factors are the result of growing population and economic developments.

They include:

• the burning of fossil fuels for transport, industry and power, producing carbon dioxide
• world-wide deforestation, sometimes involving rainforest burning, which also produces carbon dioxide
• car exhausts and nitrogen fertilisers, producing nitrous oxide
• CFCs found in fridges, air conditioning and aerosols and as a biproduct of the production of polystyrene packaging, like pizza and burger boxes
• methane, produced from rice fields, landfill sites and from both ends of cattle

Physical causes

Physical causes of global warming and cooling include:

• variations in solar energy - sunspot activity raises global temperature
• volcanic eruptions - large quantities of volcanic dust in the atmosphere shield the earth from incoming insolation, lowering global temperature. For example, the eruption of Mount Pinatubo in 1991 caused a dip in global temperatures in the early 1990s
• Milankovitch cycles or variations in the tilt and/or orbit of the earth around the sun
• changing oceanic circulation such as the periodic warming (El Nino) and cooling (La Nina) of areas of the tropical Pacific Ocean

These physical causes of global temperature change have always existed and have been responsible for alternate heating and cooling cycles of the earth's temperature.