Saturday, April 24, 2010
Changes in the state of this system can occur externally (from extraterrestrial systems) or internally (from ocean, atmosphere and land systems) through any one of the described components. For example, an external change may involve a variation in the sun's output which would externally vary the amount of solar radiation received by the Earth's atmosphere and surface. Internal variations in the Earth's climatic system may be caused by changes in the concentrations of atmospheric gases, mountain building, volcanic emissions, and changes in surface or atmospheric reflectivity (albedo).
The work of climatologists has found evidence to suggest that only a limited number of factors are primarily responsible for most of the past episodes of climate change on the Earth. These factors include:
- Variations in the Earth's orbital characteristics.
- Atmospheric carbon dioxide variations.
- Volcanic eruptions
- Variations in solar output.
‘Loss of wildlife’
Global carbon dioxide levels have continued to rise, Arctic summer ice cover was lower in 2007 and 2008 than in the previous few decades, and the last decade has been the warmest on average for 150 years.
The best thing we could do is to prepare for the worst. Build better flood defences in vulnerable areas Lee, Bracknell
Persistent drought in Australia and rising sea levels in the Maldives were further indicators of possible future patterns, they said.
They argue that without action there will be much larger changes in the coming decades, with the UK seeing higher food prices, ill health, more flooding and rising sea levels.
Known or probable damage across the world includes ocean acidification, loss of rainforests, degradation of ecosystems and desertification, they said.
In 2007, the Intergovernmental Panel on Climate Change (IPCC) warned that the world faced more droughts, floods, loss of wildlife, rising seas and refugees.
But Professor Julia Slingo, chief scientist of the Met Office, Professor Alan Thorpe, Nerc’s chief executive, and Lord Rees, president of the Royal Society, said cutting emissions could substantially limit the severity of climate change.
Prof Slingo told BBC Radio 4′s Today programme the importance of the statement was that “it emphasises that whilst global mean temperature changes may not sound very large, the regional consequences of those are very great indeed”.
She said: “As the inter-governmental panel on climate change stated very clearly in 2007, without substantial reductions in greenhouse gas emissions we can likely, very likely, expect a world of increasing droughts, floods, species loss, rising seas [and] displaced human populations.
“What this statement says very clearly is that some of those things, whilst we can’t directly attribute them at the moment to global warming, are beginning to happen.”