Global warming refers to the observed increase in our Earth’s average temperature. Although our planet experiences natural climatic variations, records show that over the past couple of decades the earth has warmed above natural trends.
In its Fifth Assessment Report (AR5), the Intergovernmental Panel on Climate Change (IPCC) stated that over the past century, the earth’s average surface temperature has risen by approximately 0.85oC (±0.18oC). The IPCC also stated that eleven of the past twelve years have ranked amongst the warmest in instrumental records.
An increase in the earth’s average surface temperature alters the climatic system which affects weather patterns all across the globe. In July 2013, the World Meteorological Organization (WMO) announced that due to increasing temperatures and changing climatic patterns, more intense, extreme and unprecedented weather events are occurring every year. In their report ‘The Global Climate 2001 – 2010: a decade of climate extremes’, the WMO stated that compared to the previous decade, there had been a 20% rise in lives lost by extreme weather events.
Further, records show that sea level is rising consistently with global warming. The IPCC states that global average sea level rose by approximately 1.8 mm per year between 1961 and 2003 and 3.1 mm between 1993 and 2003.However, scientists note that the increasing rate of sea level rise could be attributed to natural variations and trends as opposed to long-term change.
One of the primary causes of global warming is the enhanced greenhouse gas effect. The greenhouse gas effect is a vital and natural phenomenon by which greenhouses gases (e.g carbon dioxide, water vapour, nitrous oxide and methane) trap thermal energy from the sun in the earth’s atmosphere to keep it warm. This is referred to as the ‘greenhouse gas effect’, as illustrated in the image above.
Although the greenhouse gas effect is a natural and vital process, when too many gases are released in to the atmosphere, too much heat is trapped. The vast majority of climate researchers agree that this is causing global warming.
Over the past couple of decades the concentration of greenhouse gases has been increasing. There is progressively stronger evidence to suggest that this is as a result of human activity and the increase in anthropogenic greenhouse gas concentrations. There are a variety of activities which release these greenhouse gases including burning fossil fuels, clearing forests, fertilizing crop, storing waste and raising livestock.
Although not the most potent, Carbon Dioxide (CO2) is the most significant of greenhouse gases and is responsible for around two thirds of human-induced global warming. According to WWF, 97% of the CO2 emitted by western industrialized countries comes from burning coal, oil and gas for energy.
Unless greenhouse gas emissions are reduced, global warming and climate change will intensify throughout the 21st Century. Average global temperatures are predicted to increase worldwide by between 2oF to 11.5oF by 2100.