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