Global Warming

Global Warming

Upsetting a delicate balance In the past the Earth's climate has changed as a result of natural causes in our atmosphere.

The changes we are witnessing and those that are predicted are largely due to human behaviour: we are burning fossil fuels, and heating up the planet at the same time. We blow exponential amounts of carbon dioxide (CO₂) into the atmosphere every year – 29 billion tonnes of it (2004) and rising – and this warms the globe.

Since the Industrial Revolution, humans have been burning fossil fuels on a massive scale. We use this energy, almost without care for the consequences, to run vehicles, heat homes, conduct business, and power factories.

Burning fossil fuels releases carbon dioxide stored millions of years ago as oil, coal or natural gas. In the last 200 years we have burned a large part of these stores, resulting in an increase in CO₂ in our atmosphere. Deforestation also releases CO₂ stored in trees and in the soil.

The increase of CO₂ in the atmosphere thickens the 'greenhouse blanket', with the result that too much heat is trapped into the Earth's atmosphere. This causes global warming: global temperatures rise and cause climate change.

Note: CO₂ is the most important gas causing global warming. Others include methane (CH₄), nitrous dioxide (NO₂), and several artificial gases (Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs); and Sulphur hexafluoride (SF₆). These 6 groups are accounted for under the Kyoto Protocol.

Sea Ice Extent Comparison at the North Pole - mimumum ice reach comparison between 1979 and 2005. © NASA

Current statistics

Data from the World Resources Institute show that humans have added 2.3 trillion tonnes of CO₂ to the atmosphere in the last 200 years. Half of this amount was added in the last 30 years. The largest absolute increase in CO₂ emissions occurred in 2004, when burning fossil fuels alone added more than 28 billion tonnes to the atmosphere.
Source: WRI, Navigating the numbers, based on data from IEA, EIA, Marland et al, and BP.

Overall, the concentration of CO₂ in the atmosphere has increased by 31% since 1750, i.e. since the Industrial Revolution. CO₂ emissions are now around 12 times higher than in 1900 as the world burns more and more coal, oil and gas for energy. A 1999 study by Mann et al. shows the dramatic increase in temperature in the Northern Hemisphere in the last 50 years. This well-known hockey stick curve has been validated by numerous other scientists.

The (not too distant) future

We simply cannot continue pumping CO₂ into the atmosphere without curbs and controls. Even with the best case scenario for the increase in CO₂ emissions it is predicted that the concentration of CO₂ in the atmosphere will reach double the level of before the Industrial Revolution by 2100. The worst case scenario brings this doubling forward to 2045 – less than 40 years from now! The Third Assessment Report of the UN's Intergovernmental Panel on Climate Change (IPCC) predicts global temperature rises by the end of the century of between 1.4°C and 5.8°C.

The Earth’s climate is driven by a continuous flow of energy from the sun. Heat energy from the sun passes through the Earth’s atmosphere and warms the Earth’s surface.

The fragile atmosphere protects us from the universe.

As the temperature increases, the Earth sends heat energy (infrared radiation) back into the atmosphere. Some of this heat is absorbed by gases in the atmosphere, such as carbon dioxide (CO₂) , water vapour, methane, nitrous oxide, ozone and helacarbons.

The greenhouse effect

These gases, which are all naturally occurring, act as a blanket, trapping in the heat and preventing it from being reflected too far from the Earth. They keep the Earth's average temperature at about 15°C: warm enough to sustain life for humans, plants and animals. Without these gases, the average temperature would be about minus 18°C - too cold for higher life. This natural warming effect is also sometimes called the greenhouse effect.

Carbon dioxide (CO₂)

CO₂ is the most significant of the gases in our atmosphere which keep the Earth warm. Four billion years ago its concentration in the atmosphere was much higher than today (80% compared to today's 0.03%), but most of it was removed through photosynthesis over time. All this carbon dioxide became locked in organisms and then minerals such as oil, coal and petroleum inside the Earth's crust.

The natural carbon dioxide cycle

A natural carbon dioxide cycle keeps the amount of CO₂ in our atmosphere in balance. Decaying plants, volcanic eruptions and the respiration of animals release natural CO₂ into the atmosphere, where it stays for about 100 years. It is removed again from the atmosphere by photosynthesis in plants and by dissolution in water (for instance in the oceans).

The amount of naturally produced CO₂ is almost perfectly balanced by the amount naturally removed. Even small changes caused by human activities can upset this equilibrium.

The world is warming faster than at any time in the last 12,000 years. The 1990s was the hottest decade in the past millennium.

As global warming tightens its grip, the effects are being felt from the highest mountain peaks to the depths of the oceans. In just the last few years there are numerous examples of how this is affecting people and nature all over the world.

• Global warming is melting glaciers in every region of the world, putting millions of people at risk from floods, droughts and lack of drinking water.
  
  
• March 2006 showed the smallest Arctic sea ice cover ever measured. In the space of one year an area about the size of Italy was lost. The National Snow and Ice Data Center in the United States found that sea ice extent had reduced by 300,000 square km in comparison to March 2005, itself already a record low year.
  
  
• 2003, Scotland's hottest year on record, saw hundreds of adult salmon die in Scotland’s famous fisheries, as rivers became too warm for salmon to be able to extract enough oxygen from the water.
  
  
• Coral reefs around the world have been severely damaged by unusually warm ocean temperatures. The Caribbean saw its warmest ever ocean temperatures in 2005, combined with the worst coral bleaching ever. At the current rate of degradation, the entire Great Barrier Reef could be dead within a human lifetime.
  
  
• Cities like Athens, Chicago, Milan, New Delhi and Paris have sweltered under heatwaves. The 2003 summer heatwave in Europe killed 14,800 people in France alone, according to official figures released in September 2003. The French National Institute for Health and Medical Research said that the death rate was on average 60% higher than usual.
  
  
• Summer temperatures in European capitals have increased by up to 2°C over the last 30 years, a WWF report showed.
  
  
• Rising sea levels threaten entire nations on low-lying islands in the Pacific and Indian Oceans. Read how WWF South Pacific tries to help concerned villagers.
  
  
• A report released by WWF and leading meteorologists shows that human-induced global warming was a key factor in the severity of the 2002 drought in Australia, generally regarded as the worst ever.