Everyone is starting to become used to the doom scenario of climate change. Even more, we all know it has something to do with carbon and most of us understand that a cold day doesn't make climate change fake news. Just imagine, the entire world deciding, from tomorrow on, to stop all carbon emission, stop eating meat, stop cultivating rice, etc. We'll just stop putting any extra carbon dioxide or any other greenhouse gas into the atmosphere. Would this just end the problem or is it already too late? Did we pass the point of no return? I'll give you some arguments.
forest fire (source: cloudfront.net)
The poles: a shrinking mirror
As you may know, the colour black absorbs heat while white will reflect it. It is the same principle as why you would prefer a white car on a hot summer day over a black car. This is the main reason why both northern and southern arctic regions are so important regarding climate change. This is called the famous albedo-effect. Incoming (shortwave) solar radiation gets reflected even before it could heat up the earth. As a consequence of this principle, a bigger proportion of whitish area on this planet will decrease the warming up of it. In other words, big snowy and icy regions help the earth to counter the greenhouse effect.
A simple representation of the albedo effect. source: sciencebuzz.org
Climate change is making our planet warmer and as a result the regions covered by snow or ice are decreasing. Especially the north pole is shrinking at enormous rate. The bottom picture shows the enormous reduction of the arctic extent. In the past 30 years, more than 20% of the north pole has disappeared. As a result, the albedo effect shrinks and the earth is heating up even more resulting in more ice and snow melt and the story can start all over.
shrinkage of the north pole(source: sciencenews.org)
What beast is hiding underneath the permafrost?
A big part of Russia, Canada and almost entire Alaska is covered by permanent frozen soil, called the permafrost. This permafrost soil may be a few meters thick but at certain locations it can go as deep as 200 meters. The upper layer of this frozen soil may thaw during summer which is called the upper layer. This process results in big swampy areas during the warmer summer months. Because of climate change, the thawing season is lasting longer and as a consequence this active layer is getting thicker every year. Moreover, as winters are shrinking and starting later, also the active layer will stay unfrozen longer.
permafrost extent (source: vox-cdn.org)
Sounds right, but what's the problem? This active layer is producing a massive amount of methane, a less abundant but much stronger greenhouse gas. The wetlands set the perfect conditions for microbiological life which consumes organic matter and transform it to greenhouse gasses such as methane and carbon dioxide. Moreover, there are enormous bubbles of methane covered by this frozen soil. For the moment, they are protected by a thick ever frozen layer. However, when the active layer will get deeper and deeper, it will reach this storage of methane one day and all the extra greenhouse gasses are released into the atmosphere.
In a nutshell, climate change will result in longer and warmer summers and shorter and less severe winters, especially in the Arctic. This will cause an active thawing layer to expand both in tickness as in worldwide area, favouring the conditions for microbiological methane production and opening enormous methane storages. The result is that there are more greenhouse gasses released to the atmosphere and climate change will be even stronger.
the permafrost feedback (source: iopscience.iop.org)
Water vapour, the dominant greenhouse gas.
While carbon dioxide may be the most well-known greenhouse gas, the most abundant one is water vapour. The amount of water vapour in our atmosphere is described by the Clausius-Clapeyron relation. It's a curve which relates the atmospheric temperature to the maximum amount of water vapour the air can contain. This means that the warming of the atmosphere has as a consequence that it will be able to contain more water vapour. Moreover, this Clausius-Clapeyron relation is exponential, it means that a doubling in temperature will lead to more than a doubling of the maximum amount of water vapour the air can contain, and thus, a stronger greenhouse effect. Again it's a spiral which is strengthening itself.
Forest fires, a massive amount of burning carbon
Climate change comes together with an increase in global temperature, a massive part of the world will become dryer and extreme storms will increase more or less globally. This will undoubtedly lead to a higher frequency of severe forest fires as drought season will last longer and lightning will lighten up entire forested areas. This will unleash an enormous amount of carbon, storage into forests, into the atmosphere where chemical reactions would transform this biological carbon to carbon dioxide, increasing the greenhouse effect on its turn. People can also expect some indirect consequences such as ash clouds falling down on snowy areas, strongly decreasing the surface albedo, which brings us back to my first argument.
It is not all gloom and doom. These positive feedback loops aren't the only one and other systems such as these may counteract climate change. Scientist may expect more clouds, white clouds. Depending on the type of clouds the global albedo will increase, slowing down climate change. Another example of a negative feedback is the increase of vegetation due to higher carbon dioxide levels, meaning that more carbon dioxide would be transferred to our beloved oxygen. In the end, it's a very very very complicated story.
References:
Anthony K., Anthony P., Grosse G., Chanton J. (2012) Geologic methane seeps along boundaries of Arctic permafrost thaw and melting glaciers . Nature Geoscience, vol. 5:419-426.
Flannigan M., Amiro B., Logan K., Stocks B., Wotton B. (2005) Forest Fires and Climate Change in the 21st Century. Mitigation and Adaptation for Global Change, vol. 11: 847-859.
Holden, J. (2012) An Introduction to Physical Geography and the Environment. Pearson Education, Essex, 876 p.
Houghton, J. (2004) Global Warming: the complete briefing. Cambridge University Press, Cambridge, 351p
IPCC. (2013) Climate Change 2013 The Physical Science Basis. Intergovernmental panel on climate change, Cambridge, 1535p.
Nisbet E., Dlugokencky E., Bousquet P. (2014) Methane on the Rise Again. Science, vol. 343: unknown.
Perkins S. (2009) Artic Freeze Triggers Big Squeeze. Science News, vol. 175: 10.
Rivkin F. (1998) Release of methane from permafrost as a result of global warming and other disturbances. Polar Geography, vol. 22: 105-118.
Schuur E., Abott B. (2011) High risk of permafrost thaw. Nature, vol. 480: 32-33.Wagner D., Liebner S. (2009) Global Warming and Carbon Dynamics in Permafrost Soils: Methane Production and Oxidation. In: Margesin R. (Ed.), Soil Biology: Permafrost Soils, Springer, Berlin, 219-235.