What are some examples of positive and negative feedback mechanisms in climate change?

Answer 1

Positive - Reflective ice melts, exposes dark ground, things get warmer faster.

Ocean waters warm, release more CO2, things get warmer faster.

The only negative feedback I've heard about is more high altitude clouds form, block the Sun, things get cooler.

But clouds are complicated. Low altitude clouds make things warmer.

Most scientists think positive feedbacks will dominate, and global warming will get worse faster than the very conservative IPCC report says. Richard Lindzen is the rare exception, and even he admits that his views are an unproven theory which he's working on.

deathkomes4ya - James Lovelock is a well respected scientist who has published extensively on the self regulating nature of the Earth. The data on global warming has convinced him that this time is different. See:

http://www.ecolo.org/lovelock/lovebioen.htm

Answer 2

Yeah global warming has very few negative feedbacks, but if the world has shown us one thing its that it eventually balances itself.

One eventual positive feedback is if Greenland melts, Europe loses its Gulf Stream and will become like Alaska and Northern Canada / Europe, which are usually snowbound. I'm Irish and our coasts never freeze over, and we only get proper snow maybe once every few years, now on the same Latitude in other countries there are polar bears and frozen coasts.

If the Gulf Stream was lost western Europe would become like Alaska, but like Bob said snow and ice reflect light/heat which would alleviate a certain degree of the greenhouse affect and so would be a negative feedback, The process would also ruin much of Europe and coincidently eliminate one of the human sources of the global warming problem... Proving once again the system works...

The variable in this scenario is that depending on the mean temperature of the planet by the time this happens, snow and ice on these latitudes might lose their integrity so this negative feedback is circumstantial to timing, and if current trends continue would only be a stumbling block in the global warming process.

Answer 3

There's several of them and perhaps the one causing the greatest concern is the melting of permafrost.

Permafrost is a permanently frozen layer of ground but it's only near the surface that is frozen (soil is an excellent insulator). Beneath the surface the soil functions quite normally with bio processes at work, root systems growing etc. On the surface, grass, plants etc can grow.

In soils such as peat, which is composed largely of dead plant matter, there is a process of methanogenisis or biomethanation that takes place - the creation of methane gas from the decomposition of organic matter. This gas can't escape into the atmosphere because it's trapped by the layer of permafrost.

Here's how the feedback mechanism applies in this instance. The world warms up which causes the permafrost to melt, as it melts the methane trapped beneath it is released, this in turn caused more warming, more melting, more methane etc.

It's estimated that there's 70 billion tons of methane trapped beneath the tundra permafrost worldwide. Methane is 23 times more effective at contributing to global warming than carbon dioxide (specifically - it has a 100 year GWP of 23), if all the methane were to be released it would be equivalent to approx 1.5 trillion tons of CO2, enough to overload natural cycles 500 times over.

Just in the last few years and in Siberia alone there's been a million square kilometres of permafrost that has melted. In places like Siberia, Scandinavia, Canada etc the melting of permafrost has given rise to an unusual phenomena - drunken forests. With the permafrost melted the tree roots are less firmly anchored into the ground and the trees are leaning at random angles giving the appearance of being drunk. Here's a pic - http://bilder.bodenkunde.info/Siberia/assets/images/Tundra_drunken_forest_1462.JPG

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The largest feedback mechanisms are the oceans and the atmosphere itself. Each year oceans absorb 120 billion tons of CO2 from the atmosphere, at the same time they release 119 billion tons, effectively they're a sink for a billion tons of CO2 a year.

The rates of absorption and release are determined by the temp of the water, as tempos increase the oceans release more CO2 which leads to more warming, more CO2 released and so on.

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