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The impacts of global warming
AS Geography
Prediction problems
Projected temperature changes relative to 1980–99 based on three economic scenarios
Prediction problems
• The Intergovernmental Panel on Climate Change (IPCC) has produced a range of ‘scenarios’ showing possible future temperature rises (see previous slide).
• The forecasts of warming range from 1.5 to 6.0C by 2100.
• The large range reflects the fact that there are many uncertain factors impacting on predictions of future climate change.
Prediction problems
• There is uncertainty about the size of the global population in 2100.
• The rates of economic growth and related growth in emissions are not known.
• The future energy mix, i.e. fossil fuels versus renewable sources, is difficult to predict.
• The exact physical response of the climate system to enhanced greenhouse emissions is unclear, especially the scales of positive and negative feedback.
• If people adopt a ‘sustainable’ approach to economic growth, global warming might be minimal, but a ‘business as usual’ track may lead to major warming.
Sea-level rise
• Sea-level rise is also uncertain. The IPCC estimates a rise in the range of 0.2 to 0.8 m by the 2090s.
• Uncertainty about the exact rise is cause for concern for low-lying coastal countries such as the Netherlands, Bangladesh, and many small island states in the Pacific and Indian Oceans.
A tipping point?
• There are concerns that global warming may not be gradual.
• The idea of a tipping point is that the Earth’s climate may ‘jump’ quickly from its current state to a new one rather than changing by gradual transition.
• A possible cause of this ‘jump’ might be positive feedback mechanisms that amplify minor changes.
A tipping point?
• Possible feedback mechanisms:• Mass forest death, caused by small
temperature rises, triggering huge releases of carbon dioxide.
• Arctic sea-ice melt leading to a huge rise in albedo. This would lead to the retention of more solar radiation and the reflection of less back into space. The outcome would be ‘runaway’ warming.
• Changes to the pattern of ocean current circulations could drastically alter temperatures in some latitudes (a Day After Tomorrow scenario).
The Arctic
• The high northern latitudes above the Arctic Circle are a unique environment.
• Indigenous people, such as the Inuit and Saami, eke out an existence in an incredibly harsh climate.
• In 2005 the Arctic Climate Impact Assessment (ACIA) identified a series of major climate change impacts in the Arctic.
• The Arctic is probably the first location in the world to record a full range of clear global warming signals.
The Arctic
Arctic region: summary of key changes
The Arctic
• Ecosystems are under particular threat as sea ice and tundra recede.
• Tundra areas are likely to become forested and this will have a huge impact on both flora and fauna.
• Migratory mammals, such as caribou and polar bears, are particularly threatened.
• The impacts on people are likely to be equally severe.
The Arctic
• There may be positive outcomes, such as a longer tourist season, shorter winters and more opportunities for farming.
• In Greenland, retreating ice is already exposing mineral and fossil fuel deposits.
• On balance, however, the 2005 ACIA paints a gloomy future for one of the last pristine environments left on Earth.
Africa
• Much of Africa is vulnerable to climate change.• High poverty rates, heavy dependence on
subsistence farming or a few cash crops, high rates of HIV/AIDS and low levels of investment are commonplace.
• Reliance on farming and scarce natural water resources, plus a lack of capital, make adapting to climate change a major challenge.
• Some areas may benefit from a longer growing season, but most areas will suffer.
Africa
Global warming vulnerability in Africa
Africa
• An Oxfam report, ‘Africa up in Smoke’ (2005), suggested that climate-change stress could lead to a range of disastrous scenarios for much of Africa, including:
• more frequent drought and associated famine• heightened tensions over scarce resources,
leading to more conflict• reduced food security due to more unreliable
rainfall• reduced cash crop yields and/or failure of some
cash crops in some areas • rising water stress• changes to ecosystems as climate belts shift • possibly more frequent cyclones and floods