- The melting of land ice means that water stored as ice returns to the ocean
- Increases the volume of water in the oceans and causes sea level rise. This kind of sea level change is called eustatic sea level change.
- Thermal expansion also increases the volume of water, causing sea levels to rise further.
- This could cause 8-10 m sea level rise for every 1 degree celcius increase in temperature.
Sea level rise impacting on Bangladesh
- 80% of the land in Bangladesh is low-lying. Any rise in sea level will submerge large areas.
- This would affect lots of the large population of Bangladesh.
- Situation would be made worse by the fact that it's a poor country - population are vulnerable, with a low capacity to cope.
Sea level rise impacting on The Maldives
- Extremely low lying set of islands in the Indian Ocean.
- Rise in sea level of 0.5 m would sumberge most of the country.
- Population isn't poor but the economy is dependen on tourism which is threatened by sea level rise.
Permafrost is ground that has been permanently frozen for two or more years. Covers 20% of the Earth's land surface
Areas of permafrost are natural sinks of CO2. It's stored as organic material in the soil. Thawing permafrost releases some of this, contributing to global warming.
Thawing of permafrost causes the collapse of buildings and pipelines built on it. May bring economic benefits to humans because it's easier to extract natural resources from the land when it's unfrozen.
Effects on global weather patterns
Increase in frequency of extreme weather events --> increasing ocean temp means a higher chance of tropical cyclones.
Change in the distribution of climatic regions, eg. colder regions may shrink and warmer tropical regions may advance to higher latitudes
- This affects ecology. Species will have to migrate to remain in a suitable climate, if they don't they will die off.
- It also affects agriculture - some areas unsuitable for cultivation as the temp and timings of seasons change.
- Regional climate changes may bring benefits some human activities eg, economic benefits of tourism.
The IPCC's emissions scenarios
Predictions are of how human CO2 emissions will change up until 2100.
- Emissions not increasing much more (minimum emissions)
- Emissions continuing to grow as they are now ('business as usual')
- Emissions increasing a lot (maximum emissions)
- Emissions being controlled by sustainable management strategies.
They can put these scenarios into global climate models, to see how the climate could change with each scenario.
These can then be used to show how different climate changes can cause different impacts.
Why is it difficult to make predictions?
- We don't actually know how emissions will change so we don't know which scenario is most accurate.
- We don't know how much of the emissions will be taken in my CO2 sinks.
- We don't what exact climate changes each emission scenario will cause.
- The extent of climate change due to natural causes isn't known.
- We don't know what attempts there will be to manage the impacts of climate change, or how successful they'll be.
Climate change could lead to a tipping point - where a sliht rise in temperature would cause catastrophic and irriversable changes to the environment.
This may happen because of positive feedback loops - where a change in the climate is speed up by the impacts it's already caused.
The combined effect of positive feedback on several of the impacts of global warming eg. ice melt and the destruction of CO2 sinks, may lead to a tipping point.