From Envirowiki

Climate change has a number of known and hypothesised tipping points. These are points at which the warming climate creates a positive feedback which leads to more warming. There may also be negative feedback loops in climate change, which would lead to stabilisation at a certain temperature, until climate forcings were increased to a level great enough to overcome the stabilisation points.

Contents 1 Known tipping points 1.1 Ice cap melting 1.2 Ocean Floor Methane Hydrates 1.3 Drying of the Amazon Rainforest 1.4 Permafrost Thawing 2 Ocean algae die-off 3 References

[edit] 1 Known tipping points

[edit] 1.1 Ice cap melting

With global warming, the amount of ice in the polar regions will be reduced. Ice has a high albedo (it can reflect a lot of energy in the form of light). Usually, the substance below the ice - water in the arctic, and rock in the antarctic - has a much lower albedo, meaning it absorbs more of the light energy from the sun, and re-emits it as heat. So the more ice melts, the faster those areas warm, and hence the mean temperatue of the planet increases.

In August 2008, the ice in the Arctic ocean became completely surrounded by ocean (no ice-land bridges) for the first time since the last ice age, and in human history^[1].

[edit] 1.2 Ocean Floor Methane Hydrates

Trapped on the bottom of the world's oceans are around 10 (possibly up to 20) billion tonnes carbon as methane hydrates^[2], a solid form of water containing high levels of methane, a greenhouse gas 23 times more potent than CO₂. The atmosphere currently contains around 700 million tonnes (GtC), so even if only 10% of these hydrates were released, the atmospheric concentration would more than double (to ~750-800ppmv).

The hydrates are held in place by low temperatures and high pressures. [[Ocean temperature increase|Increasing temperatures] could melt the hydrates, and changes in pressure (ie. due to sea level rise) could destabilise the hydrates, which are lighter than water, and may then float to the surface.

Large hydrate releases have occurred in the past, how ever, not for many millions of years.

[edit] 1.3 Drying of the Amazon Rainforest

[edit] 1.4 Permafrost Thawing

Permafrost is permanently frozen ground, mostly around the Arctic (Siberia and Canada). Along with rising global temperatures, climate change is making the the Arctic region warm even faster. Depending on the extent of warming, large areas of permafrost may begin to thaw, and in the process create lakes in which microbial activity can convert the existing organic matter into methane. In drier areas, carbon dioxide may be emitted. Western Siberia alone holds around 500GtC^[3].

[edit] 2 Ocean algae die-off

Oceanic algae is one of the world's largest carbon sinks, removing up to 60GtC per annum from the atmosphere^[3]. it is currently dieing off at a rate of 1-4% per year.

[edit] 3 References

1. ↑ Geoffrey Lean (2008-08-31). "For the first time in human history, the North Pole can be circumnavigated", The Independent. Retrieved on 2008-09-02. 
2. ↑ Gerald R. Dickens (2004-11). "Methane Hydrate and Abrupt Climate Change", Geotimes. Retrieved on 2008-09-27. 
3. ↑ ^{3.0 3.1} Spratt, David; Philip Sutton (2008-07). Climate Code Red: the case for emergency action, first, Scribe Publications, 320. ISBN 978-1-921372-20-9. Retrieved on 2008-09-28.