Tipping elements in the Earth's climate system

As we're at the end of the year I thought it might be good to have a little recap on the principal aim of this blog, which is to cover and explain climate tipping points, and then to illustrate this with some new examples of effected systems we haven't covered yet :). 

The term “tipping point” commonly refers to a critical threshold at which a tiny perturbation can qualitatively alter the state or development of a system. Here we introduce the term “tipping element” to describe large-scale components of the Earth system that may pass a tipping point.

Timothy Lenton et. al. (2007) offer a formal definition of the term ‘tipping element’, “to describe subsystems of the Earth system that are at least subcontinental in scale and can be switched—under certain circumstances—into a qualitatively different state by small perturbations. The tipping point is the corresponding critical point—in forcing and a feature of the system—at which the future state of the system is qualitatively altered”.

Human activities may have the potential to push components of the Earth system past critical states into qualitatively different modes of operation, implying large-scale impacts on human and ecological systems. 

Notable examples include the potential collapse of the Atlantic thermohaline circulation (THC) (Rahmstorf and Ganopolski, 1999) and dieback of the Amazon rainforest (Cox et. al., 2000).

A shutoff in North Atlantic Deep Water formation and the associated Atlantic THC can occur if sufficient freshwater (and/or heat) enters the North Atlantic to halt density-driven North Atlantic Deep Water formation. However the IPCC (2007) argues that an abrupt transition of the THC is “very unlikely” (probability <10%) to occur before 2100 and that any transition is likely to take a century or more.

A large fraction of precipitation in the Amazon basin is recycled, and, therefore, simulations of Amazon deforestation typically generate ≈20–30% reductions in precipitation (Zeng et. al., 1996), lengthening of the dry season, and increases in summer temperatures (Kleidon and Heimann, 2000) that would make it difficult for the forest to reestablish, and suggest the system may exhibit bistability.

Hope you have a good new year, in 2014 we’ll use Lenton, 2007, further to illustrate all the most likely potential policy relevant tipping points across the globe as well as have at more in depth look at our above case studies. Not to mention a few other randoms I hope.

Check out the full article here: http://www.pnas.org.libproxy.ucl.ac.uk/content/105/6/1786.full

References

Cox, P.M. Betts, R.A. Jones, C.D. Spall, S.A. and Totterdell, I.J. (2000) Nature 408:184–187.

IPCC (2007) Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, eds Solomon, S. Qin, D. Manning, M. Chen, Z. Marquis, M. Averyt, K.B. Tignor, M. and Miller, H.L. Cambridge Univ Press,Cambridge, UK.

Kleidon, A. and Heimann, M. (2000) Clim Dyn 16:183–199.

Lenton, T.M. Held, H. Kriegler, E. Hall, J.W. Lucht, W. Rahmstorf, S. Schellnhuber, H.J. (2008)
Tipping elements in the Earth’s climate system. Proc. Natl Acad. Sci. USA 105, 1786–1793.

Rahmstorf, S. Ganopolski, A. (1999) Clim Change 43:353–367.

Zeng, N. Dickinson, R.E. and Zeng, X. (1996) J Clim 9:859–883.

How Much is too Much?

One of the most important questions for scientists and policy makers is: what is dangerous climate change?

Of course, this will depend on where you live. For example, low-lying islands are far more susceptible to sea-level rise than large land masses. In 2005, Britain was hosting the G8 summit in Gleneagles, Scotland. The meeting came up with a ‘magic number’ of 2  above pre-industrial average temperature; below this threshold, there would be both winers and losers due to regional climate change, but above this figure everyone is likely to lose. This is backed up by the IPCC, an independent scientific body of thousands of scientists worldwide.

Thus 2 seems to be the point at where numbers increase radically, i.e. a climate threshold/tipping point. For this reason 2 degrees Celsius has become a powerful symbol of the challenge facing human society. The major problem is that we are unlikely to be able to keep mean global temperature below the magic 2 degrees Celsius as nation states haven’t been proactive enough in their carbon reduction proposals and execution of them.

Today's global surface temperature increase since pre-industrial times is 0.8° C (NASA GISS 2013). Even if we were to keep atmospheric carbon dioxide levels at the 2,000 levels this would still another 0.6 degrees Celsius at least (Maslin, 2008), so without doing anything we are at 1.4 degrees Celsius. Not to mention the fact that in 2013 atmospheric carbon dioxide passed a new high of 400ppm! Thus surpassing the critical 2 degrees Celsius is a likely, if not inevitable event in our lifetime.

Below is a list, taken from Maslin (2008), of likely impacts of increasing global average temperature.

·      1-2 degrees Celsius  above pre-industrial  

• Major impacts on ecosystems and species
• Increases of heat waves, droughts, floods and spread of infectious disease.

·      2-3 degrees Celsius above pre-industrial

.
•     Major loss of coral reef system and other species.
•         Large impacts on agriculture, water resources and health.
•     Significant increases in droughts and extreme rainfalls.
•      Up to 74cm sea level rise in next100 years.
•      Terrestrial carbon sink becomes a source, accelerating global warming.

·      1-3 degrees Celsius bove pre-industrial? 

• Greenland ice-cap starts to melt (7m).

·      1-4 degrees Celsius above pre-industrial?

• North Atlantic circulation collapse

·      3-4 degrees Celsius above pre-industrial  

• Major species extinction.

·      2- 4.5 degrees Celsius above pre-industrial?

•     1-3 billion people suffer from water scarcity
•     Food yields fall everywhere, global production plummets.
•     Fifth of world population effected by flooding.
•      Significant increase in human deaths due to malnutrition, disease, heat wave, flood and drought.

·      5-6 degrees Celsius or higher above pre-industrial 

•      Don’t go there…..

Reference


Maslin, M. (2008) Golbal Warming. A Very Short Introduction. Oxford University Press, Oxford.

The Revenge Of Gaia

The 19th annual Conference of the Parties (COP) to the UN Framework Convention on Climate Change (UNFCCC) is beginning in Warsaw this week with an apparent ‘mood of realism’ over future climate deals. This is much needed as the the Overseas Development Institute (ODI) has recently stated that rich countries are spending seven times more supporting coal, oil and gas than they are on helping poorer nations fight climate change!

Against this backdrop I thought it might be 'fun' to examine an apocalyptic scenario I’ve wanted to cover for a little while given that it encompasses James Lovelock's ideas.

James Lovelock is one of the most famous geographers/environmentalists out there. He had a great 'eureka' moment over the earth's atmosphere. This was known as Gaia - a new way of thinking about the Earth as a holistic, self-regulating system. In essence he believes that if left to itself, the Earth will stabilise itself between certain boundary points (think back to the ball rolling in the bowl analogy) and can thus be viewed as an organism i.e. alive! It's a fascinating idea, and one that I put some stock in so I would thoroughly recommend investigating Gaia and James Lovelock himself - especially as i will be later returning to his ideas on nuclear energy as the only realistic green alternative to fossil fuels. His ideas are certainly 'out-there' at times, but are enthralling to read, if not daunting, and I feel are possible to be proved correct, although maybe not too the the extent he fears. The general scientific consensus is that warming will be more than 2 degrees celsius, meaning some regions of the globe will experience some dangerous climate change.

To get to the point of Lovelock's ideas in relation to tipping points, i.e. moving beyond a self-regulating, self-stabilising system (due to human input of Green House Gases (GHGs). Here is an exert from the BBC 4 series Beautiful Minds. If you could watch it now it will nicely summarise the degree of danger Lovelock perceives us to be in. Only 1 billion people to survive? 

Note in the video when he states: 

"When it gets too much, Gaia can't cope with it" - this is him referring to the tipping point.

As I'm sure you've gathered he is certainly in the 'Alarmist' camp, and is certainly controversial, it is wrong to simply dismiss him as over dramatic (although some people do just that). The melting of ice caps will as he says reduce the reflectivity (known scientifically as 'albedo') and cause further warming. As we've previously covered in the blog, this is known as a positive feedback mechanism as the process was instigated by rising CO2 levels. Lovelock believes that the further warming from this effect alone will equal the GHGs impact thus he thinks we are already in an irreversible dangerous world where terrible climate impacts await us in the next 100 years as the globe heats up. The possibility exists, to him, that less than a billion people will survive. This just isn't something people are willing to really contemplate yet.

James Lovelock's new book: The Revenge of Gaia, further builds on these ideas. He states that the Earth is about to pass into a morbid fever (remember that he likes to view the earth as an organism) that may last as long as 100,000 years. He states that as members of the Earth's family and an intimate part of it, that you and especially civilisation are in grave danger. We are the ones responsible and will suffer the consequences: as the century progresses, the temperature will rise 8 degrees centigrade in temperate regions and 5 degrees in the tropics. Much of the tropical land mass will become scrub and desert, and will no longer serve for regulation; this adds to the 40 percent of the Earth's surface we have depleted to feed ourselves.

Curiously, aerosol pollution of the northern hemisphere reduces global warming by reflecting sunlight back to space. This "global dimming" is transient and could disappear in a few days like the smoke that it is, leaving us fully exposed to the heat of the global greenhouse. Lovelock believes we are in a fool's climate, accidentally kept cool by smoke, and before this century is over billions of us will die and the few breeding pairs of people that survive will be in the Arctic where the climate remains tolerable. 

It really is hard to even imagine the necessary degeneration needed for this to occur. 

To answer the question posed in my introductory post, over whether the film 'The Day After Tomorrow', was total bullsh*t or not? It seems not. Even wind turbines are turning against us.

Here's the Amazon link to his book:   

http://www.amazon.co.uk/Revenge-Gaia-Earth-Fighting-Humanity/dp/0141025972/ref=sr_1_1?s=books&ie=UTF8&qid=1384199245&sr=1-1&keywords=the+revenge+of+gaia

Over and out.