Target 300

Home About News Solutions Campaign Action Donate Contact

Future Impacts

Looking at the cake is like looking at the future. Until you have tasted it,what do you really know?And then, of course, it's too late. Too late.
Merlin in the movie "Excalibur" - 1981

Though one could argue, and indeed should argue, that the impacts we are already experiencing today are enough evidence that climate change has already gone too far, if we look to the future impacts of climate change, the case to act immediately on climate change becomes even stronger.

Index

1 degree is 1 degree too much

Globally, discourse around tackling climate change is often focused on preventing nominally dangerous climate change at two degrees. There is little direct evidence that two degrees present some magical threshold from beyond which climate change is dangerous. Evidence from the impacts we have already seen would seem to suggest other wise.

Mark Lynas in his book "Six Degrees" (Lynas 2007) looks at the effect of increasing temperatures are likely to have on the world. Each chapter looks at potential impacts for increasing temperatures rises in increments of 1 degree, based on historical scientific evidence, and each chapter paints an ever worsing picture.

His first chapter looks at the scenario around a 1 degree temperature rise, using data from the medieval warming period which occurred between 800-1300 AD, and the Holocene maximum of 6000 years ago. Lynas warns of the collapse of America's most important agricultural areas in the mid west due to increased drought and higher temperatures, possibly remobilising 9000 square kilometres of former mobile dunes, the slowing down of the Atlantic Meridional Overturning Circulation (of which the Gulf Stream is a part) and the resultant cooling of Europe, and the collapse of the Amazon forest system.

His book makes chilling reading and if only some of the predicate scenarios eventuate it will mean significant catastrophe for millions, and makes a mockery of any climate goal or target which ignores the potential devastation of a one degree temperature rise.

Feed Back Loops

A critical element of the current climate change problem is the issue of positive feed back loops within the climate system.

Some of the Earth's natural systems respond to global warming and can further increase or decrease global warming. If the response speeds up climate change it is called a positive feed back loop, a negative feed back loop if it slows climate change down.

Examples include the melting of the North Pole summer ice. As the North Pole summer ice melts and exposes more ocean surface less sunlight is reflected and more heat enters the Arctic system, this in turn melts more ice and so on.

Other critical positive feed back loops include reduction in the area of snow and ice which reflect sunlight, and the thawing of permafrost and consequent release of methane, collapse of the Amazon and other forests systems,and the releasing of soil carbon due to heating.

As positive feed back loops give rise to increased temperatures they trigger a chain reaction of further greenhouse gas releases and may even trigger other positive feed back loops.

Using the work presented in Mark Lynas's book Six Degrees (Lynas 2007) I have constructed a table which shows a chain reaction of impacts of feed back loops acting on other feedback loops eventually resulting in a 6 degree plus temperature rise.

Of significant concern is the possibility that these feed back loops will release so much greenhouse gases that even were humanity able to reduces it's emissions to zero and below there would more than enough greenhouse gases being emitted from degrading natural system to trigger further temperature rises.

The question of when these feedback loops are triggered, or using another term, pass their tipping points, is critical if we are to solve the problem of climate change.

Below are some examples of feed back loops that will increase global warming if not stopped. There are many others.

Melting of the North Pole

The following two images show the reduction of the surface area of the north pole. The first simage shows the 1981 summer ice extent and the sceond shows the 2007 summer melt which was the biggest on record at the time. As the area of summer ice reduces 80-90% of the light is captured by the darker sea water. By 2007 the Arctic had lost 80% of its volume of ice when compared to 40 years ago. Notice the collpase the of the old ice depictated in red.

The rate at melting of the North Pole summer ice has been far faster than anyone has predicted. The below graph shows the ranges of predicted melting rates of the Norht Pole by the Intergovernmental Pannel on Climate Change in its 4th Assement Report (2007) and what is actually happening and will happen if the recent melting trends continue.

Sea Level Rise

There is now significant evidence that Greenland has begun to rapidly melt (Anisimov 2007). A melting of Greenland would result in a 7.3 meters (Sommerkorn & Hamilton 2008)) sea level rise flooding large coastal area and many low lying islands. Hansen's recent work has shown that 450 ppm CO2 is enough to trigger a 60-80m sea level rise with the complete melt of the Antarctic Ice Sheets (Hansen 2008a).

Ecosystem Collapse

As the world heats up ecosystems around the world will stress and begin to fail. As each system fails more CO2 is released into the atmosphere. The below diagrams taken from work by Geof Carry from ANU (Carry 2002) represent just one example of this scenario and shows the predicted impacts of a two degree temperature rise on the fire regimes around Canberra. The changes in fire frequency are of such an extent that most ecosystems would fail.

Soil Carbon Collapse

The below image is from the UK Met Office Hadley Centre (Hadley Centre 2008). It shows predicted decline in world soil carbon as the world warms up and increased microbial activity beginning to break down the carbon in the soil releasing it into the atmosphere. The graph shows that soil becomes a net emitter of CO2 around 2080, and the carbon stored in vegetation also begins to decline at this point.

Tipping Points

If we understand the importance of feed back loops is the next issue we need to consider is at what point do they pass their tipping point, ie the point beyond which global warming temperature will enable the feed back loops to become self sustaining.

It is merely an application of common sense to understand that once a positive feed back loop that has been triggered by global warming unless there is a corresponding cooling returning the the conditions prior to the loop being triggered it will continue.

James Hansen comments on the issue of tipping points at the Zero Emission Network "Target Zero" Conference in Melbourne in 2007.

"We're at a point where it really is a crisis. Because the danger is, we are close to passing tipping points. We're close to the point where the rest of the arctic sea ice will disappear quite rapidly. And we're very close to the point where the West Antarctic ice sheet and the Greenland ice sheet could be unstable and begin to disintegrate out of our control."

In January 2008 James Hasen discussed the issue of tipping points further in a presentation to Royal College of Physicians, London. He presented this information on a table below (Hansen 2008b).

The table above shows that several critical systems pass their tipping points somewhere between 300 and 350 ppm CO2 and in the case of North Pole Summer Ice, between 300 and 325 ppm CO2.

Hansen makes reference to stop this positive feed back loop and restoring the summer Arctic ice the his recent draft paper titled “Target Atmospheric CO2: Where Should Humanity Aim?” (Hanson 2008a)‏

"Stabilization of Arctic sea ice cover requires, to first approximation, restoration of planetary energy balance. Climate models driven by known forcings yield at present planetary energy imbalance of +0.5-1 W/m2 (5), a result supported by observed increasing ocean heat content (48). CO2 amount must be reduced to 325-355 ppm to increase outgoing flux 0.5-1 W/m2, if other forcings are unchanged. A further reduced flux, by ~0.5 W/m2, and thus CO2 ~300-325 ppm, may be needed to restore sea ice to its area of 25 years ago."

The Point of No Return

"Now for a tincture of tenderness, but I must use only a drop. Oops, too much!" Professor Weirdo - Milton the Monster Show - 1960's

The point of no return is the point at which human effort can no longer reverse climate heating. After this point is reached, positive feed back loops, continue to heat our climate, out of our control.

James Hansen comments on the point of no return, "Our home planet is dangerously near a tipping point at which human-made greenhouse gases reach a level where major climate changes can proceed mostly under their own momentum." (Hansen 2008c)‏

However some scientists, such as James Lovelock state that we have passed the point of no return. Lovelock is quoted in an article in the Times (UK), ""Human outpourings of greenhouse gases have flicked the switch that turns the world from its colder to its warm state – and it is probably too late to stop it," he said. "The warming impact of the carbon we have already released is such that the Earth has taken over and our greenhouse gas emissions are being amplified by nature itself." (Leake 2007)‏

The point of no return is one of the most important concepts to understand in the climate debate, for it is absolutely critical that we do not pass this point. That fact that a number of credible scientists believe we are close to the point of no return or indeed have passed it suggests that much stronger action needs to be taken on climate change.

References

Anisimov, O.A., D.G. Vaughan, T.V. Callaghan, C. Furgal, H. Marchant, T.D. Prowse, H. Vilhjálmsson and J.E. Walsh, 2007: Polar regions (Arctic and Antarctic). Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, 653-685.

Cary, G.J. 2002, Importance of a changing climate for fire regimes in Australia. In Flammable Australia: The Fire Regimes and Biodiversity of a Continent. (Eds R.A. Bradstock, A.M. Gill, J.E. Williams ). Cambridge University Press.

Haley Centre (2008), Met Office Hadley Centre: Results from carbon cycle experiments, viewed 15 September 2008, http://www.metoffice.gov.uk/research/hadleycentre/models/carbon_cycle/results_trans.html

Hansen, J 2008a. draft paper "Target Atmospheric CO2: Where Should Humanity Aim?", Columbia University, viewed 15 September 2008 http://www.columbia.edu/~jeh1/2008/TargetCO2_20080407.pdf

Hansen, J 2008b Global Warming: The Perfect Storm. [slides] 29 Jan 2008 the Royal College of Physicians, London.

Hansen, J 2008c, Tipping point: Perspective of a climatologist in Eva Fearn (ed.) 2008, State of the Wild 2008-2009, Wildlife Conservation Society and Island Press, Washington

Leake, J 2007, Fiddling with figures while the Earth burns, TimesOnline, 6 May, viewed 15 September 2008 http://www.timesonline.co.uk/tol/news/uk/science/article1751509.ece

Lynas, M 2007, Six Degrees: Our future on a Hotter Planet, Fourth Estate, London

Sommerkorn,M & Hamilton, N 2008, Arctic Climate Impact Science: an update since ACIA WWF International Arctic Programme, Oslo.

Spratt, D & Sutton, P 2008, Climate Code Red: the case for a sustainable emergency, Friends of the Earth, Melbourne