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"At last Peter learnt his lesson, that if you always tell lies, people will eventually stop believing you; and then when you're telling the truth for a change, when you really need them to believe you, they won't."
from "The boy who cried wolf", a European Children's Story

Update* - August 2009 The focus of the 350.org is slowly changing away from calling 350 ppm Co2 "Safe". They have removed the word "Safe" from some of their graphics and promotion material and are changing some of their explainations to now say the 350 target releates to 350 ppm CO2 -e rather than just CO2. Disapointingly at a recent public lecture given by Bill McKibben in Melbourne, 350 ppm CO2 was still being promoted as the "safe" target, despite a short caviet.

*The 350ppm page was orginally posted December 2008

350 ppm as a target? Better than a bigger number, but not safe.

Stalwart climate campaigner Bill McKibben recently founded the very energetic and valuable international climate campaign group 350.org. The 350.org campaign is trying to establish 350 ppm CO₂* as the preferred level for carbon dioxide in the air

* "ppm" = parts per million, ie. the proportion of the atmosphere made up a specific gas in 'one millionths'. So 3 ppm = three parts in every million parts of the atmosphere.

The good news - 350 ppm

If the world tried  to get the CO₂ in the air back to 350 ppm (from the 387 ppm where it is in 2008) we would have to:

• cut greenhouse gas emissions to zero, and
• draw massive quantities of excess CO₂ out of the air.

These are two things that are desperately needed if we are to have a safe climate..........so a target of 350 ppm atmospheric CO₂ is much better than targets such as 400ppm, 450 ppm or even 550 ppm which are taken to imply that humans can continue to emit more CO₂.

The bad news - 350 ppm

Unfortunately 350 ppm is not the target we should be pursuing if we want to get back to a safe climate - because 350 ppm CO₂ cannot restore the Arctic ice to its full extent and that is what's needed to restore other key elements of the Earth system (eg. the permafrost, the Himalayan ice fields and the Great Barrier Reef).

The effect of losing the Arctic summer ice

Given the unprecedented changes seen in recent years, many Arctic scientists are now predicting an ice-free summer Arctic by somewhere between 2011 and 2015 (3 - 7 years time if you are reading this in 2008!). (References: see Arctic sea ice loss)

When this ice loss is complete there will be a local Arctic warming pulse of about 5ºC, as highly reflective ice is relaced by dark ocean that is highly efficient in absorbing incoming solar radiation.  And this warming impulse will travel south over the sub-Arctic permafrost lands for about 1500 kilometres (Reference: see Permafrost melting: Lawrence 2008).

It estimated that there are at least 1.6 billion tonnes of carbon stored in the permafrost lands of the sub-Arctic (Reference: see Permafrost melting: Schuur 2008).

And according to a recent rough estimate there may at least a further 1.4 billion tonnes of carbon in the Arctic Ocean seabed (made up of submerged permafrost, trapped methane, etc.) (Reference: see Permafrost melting: Shakhova 2008 ).  

The permafrost lands alone contain carbon that is more than twice the total carbon currently in the atmosphere from both natural and human induced sources. (Reference: see Permafrost melting: Schuur 2008).

The loss of Arctic sea ice will contribute to a substantial mobilisation of these carbon stores leading to very large methane and CO₂ releases over the coming decades.

The CO₂ already in the air (in 2008) is sufficient even now to cause a 2.4ºC warming as the aerosol pollution that partly masks the warming effect of the CO₂ is eliminated due to pollution control and the shift to low and zero carbon fuels (Reference: See Atmospheric warming and masking processes: Ramanathan & Feng 2008).  The Arctic warming will make this disastrous situation substantially worse - even if no more carbon is released into the air from the human economy.

The added CO₂ from the permafrost will also contribute to serious acidification of the ocean and the destruction of plankton and marine animals that have calcium-based shells. (References: see Ocean acidification).  This is highly damaging to marine ecosystems and also degrades the capacity of the oceans to absorb CO₂ and lock it away in marine sediments as the calcareous shells fall to the ocean floor.

The loss of the Arctic sea ice will also condemn the Greenland ice sheet to nearly complete melting (Reference: Greenland ice sheet: Gregory et al.) causing many metres of sea rise - ultimately up to about 7 m in total (Reference: Greenland ice sheet: Gregory et al.).

The Greenland ice sheet contains 2.9 million cubic kilometres of ice – the second largest body of ice on earth, holding 6% of all fresh water on the planet. Research in 2004 published in Nature, suggested that Greenland’s ‘critical melt threshold’ is 3°C of regional warming (ie. local to the Arctic).  If this point is passed, as would happen if the Arctic sea ice is fully absent in summers, the Greenland ice sheet is likely to melt away completely, leading to an eventual sea level rise of around 7 metres. By considering IPCC emissions scenarios, researchers have concluded that the “Greenland ice-sheet is likely to be eliminated by anthropogenic climate change unless much more substantial emissions reductions are made than those envisaged by the IPCC.” (Reference for whole paragraph: Greenland ice sheet: Gregory et al. 2004)

So a major conclusion can be reached:

It is not possible to have a safe climate if the Arctic summer sea ice is missing for any extended period of time.

What needs to be done to restore the full extent of the Arctic summer sea ice and will a stabilisation target of 350 ppm enough?

In their Target CO₂ paper James Hansen and his co-authors have said:

"stabilization of Arctic sea ice cover requires, to first approximation, restoration of planetary energy balance. Climate models driven by known forcings yield a present planetary energy imbalance of +0.5-1 W/m2 [5]. Observed heat increase in the upper 700 m of the ocean [76] confirms the planetary energy imbalance, but observations of the entire ocean are needed for quantification. 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 imbalance reduction, and thus CO₂ ~300-325 ppm, may be needed to restore sea ice to its area of 25 years ago." (emphasis added)

(Reference: Hansen and the Target CO₂ paper: Hansen et al. 2008)

So Hansen et al. argue that if we want to get the Arctic Sea ice back to its area of 25 years ago then the world might have to aim for an atmospheric CO₂ reduction target somewhere in the range of 300 ppm - 325 ppm.

In the absence of any other information, the precautionary approach would be to aim for the lower end of the range ie. for 300 ppm. (To aim instead for the top of the range is to run a strong risk of not recovering the Arctic sea ice at all.)

But we do have some clues about where to aim.

In 2007, Mark Serreze, a senior research scientist at CU-Boulder's National Snow and Ice Data Center said the Arctic sea-ice extent trend had been negative in every month since 1979, when concerted satellite record keeping efforts began.

From:  http://nsidc.org/news/images/20081002_Figure3.png

We know from recent history that the loss of the Arctic sea ice was already underway by about 1980 when the CO₂in the air was about 340 ppm (Reference: Historic atmospheric CO₂ levels; also graph below) and the full heating effect of that level of CO₂ had not yet been felt.  And there was a significant warming period in the Arctic around 1940 when the CO₂ was about 310 ppm and the full heating effect of that lower level of CO₂ had not yet been felt. 

From:  http://globalwarmingart.com/wiki/Image:Carbon_History_and_Flux_Rev_png

From:  http://www.metoffice.gov.uk/climatechange/science/monitoring/

 So there can be no doubt that we already know from direct experience that a 350 ppm atmospheric CO₂ target is within the danger zone.

So why is 350.org promoting a 350 ppm target?

In the northern summer of 2007, Bill McKibben was shocked by the 23% collapse of the extent of the Arctic sea ice .  He recognised that a new, more stringent greenhouse gas target would be needed.

Shortly after the 2007 Arctic 'big melt' Bill McKibben came across the early draft of the Target CO₂paper by Hansen et al. (quoted above).  Hansen and his co-authors not only made the scientific observation that atmospheric CO₂ levels might need to be reduced to between 300 ppm and 325 ppm to enable the Arctic sea ice to be restored as discussed above, but also offered a policy recommendation that the world should adopt an "initial target" of 350 ppm for the stabilisation of the atmospheric CO₂ level.

"An initial CO₂ target of 350 ppm, to be reassessed as effects on ice sheet mass balance are observed, is suggested." (p. 13)
(Reference: Hansen and the Target CO₂ paper: Hansen et al. 2008) 

Bill was deeply struck by Hansen et al.'s statement in the abstract to the Target's paper where it said that: 

"If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO₂ will need to be reduced from its current 385 ppm to at most 350 ppm, but likely less than that".
(Reference: Hansen and the Target CO₂ paper: Hansen et al. 2008) 

Encouraged by his experience the year before, when his campaign group Step It Up catalysed 1400 protests across the US in favour of a national target to cut CO₂ emission 80% by 2050 - elevating the then strongest State Government policy to a national policy adopted by the Clinton and Obama Presidential campaigns, Bill saw Hansen's call for a 350 ppm initial target as just what was needed to give a credible foundation to a simple but powerful global campaign, credible because the target had been recommended by a world famous scientist.  Now activists could be encouraged to press governments to commit to an atmospheric stabilisation target of 350 ppm CO₂.

Bill McKibben and the 350.org team quickly began to apply internet campaigning and community marketing techniques to the 350 pm target:

• "There’s a number — a new number — that makes this point most powerfully. It may now be the most important number on Earth: 350. As in parts per million of carbon dioxide in the atmosphere." (source).
• 350 parts per million. That's the last number you need to know.... It's the safety zone for planet earth. (source)

From http://350.org/, the home page of 350.org

From: http://350.org/ - one of the set of five slides on the home page.

But is the 350 ppm CO₂ target the ultimate target to take us back to a safe climate, as asserted by the 350.org campaign?

No.

There is ample evidence from within the paper in which James Hansen and his co-authors first recommended the 350 ppm target that it was never seen as the ultimate target for climate safety.  It was simply a stepping stone to the ultimately necessary target.

• The originators of the 350 ppm target, James Hansen and his co-authors of the Target CO₂ paper, called the target an "initial target" - it was clearly never meant to be the last word on the subject: 
  On p. 13 they say: "An initial CO₂ target of 350 ppm, to be reassessed as effects on ice sheet mass balance are observed, is suggested."
• James Hansen et al. also clearly indicated in the Target CO₂ paper that the ultimate target was highly likely to be below 350 ppm:
  # In the Abstract of the paper they said: "If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO₂ will need to be reduced from its current 385 ppm to at most 350 ppm, but likely less than that."
  # On page 13 they wrote: "thus CO₂ ~300-325 ppm, may be needed to restore sea ice to its area of 25 years ago." (Note: the tilde in front of the 300 indicates that the target could even be lower than 300 ppm.)
  # On page 13 they wrote: "Coral reefs are suffering from multiple stresses, with ocean acidification and ocean warming principal among them [77]. ...... A 300-350 ppm CO₂ target would significantly relieve both of these stresses."
  # On page 13 they wrote: "Ongoing Arctic and ice sheet changes, examples of rapid paleoclimate change, and other criteria cited above all drive us to consider scenarios that bring CO₂ more rapidly back to 350 ppm or less."
  # On page 16 they wrote: "We suggest an initial objective of reducing atmospheric CO₂ to 350 ppm, with the target to be adjusted as scientific understanding and empirical evidence of climate effects accumulate.".
  # On page 16 they wrote: "a case already could be made that the eventual target probably needs to be lower"
• In supplementary notes to the Target CO₂ paper using a Q&A format Hansen said:  "1. Less than 350 ppm: Are you saying that the optimum level of atmospheric CO₂, for humanity and nature, is 350 ppm? No. In the long run, the level that we need to aim for is probably less than 350 ppm.".

So the Hansen et al. target was never meant to be the last word on the subject, was almost certainly too high.

This temporary transitional target was then picked up uncritically by a community campaigner who, after the shock of the 2007 Arctic sea ice melt, was looking for the lowest credible CO₂ target to promote publicly that carried the cachet of a well known and respected scientist - and the target was then promoted, with all the caveats and qualification removed, as if it indicated the absolute final destination for the climate system.

Why did James Hansen et al. propose the specific number of 350 ppm to be the initial target?

Remarkably, given the significance that the 350.org campaign now attaches to the 350 number, the Target CO₂ paper doesn't say why 350 was chosen! Nowhere in the paper is any argument presented to justify the precise magnitude of the proposed initial target.  It is simply asserted and no scientific, or logical or numerical reasoning is offered to justify the specific number.

James Hansen is deservedly a world respected scientist so, even if he and his co-authors omitted to explain in the Target CO₂ paper where the 350 initial target came from, he undoubtedly would have had a private rationale for the number.  Shortly after the Target CO₂ paper came out, Philip Sutton, co-author of Climate Code Red decided to find out what the rationale was.

Sutton's first step was to very carefully read the Target CO₂ paper to see if a possible rationale could be inferred, by reading between the scientific lines.

A major focus of the paper was a review of the palaeo-climate data, going back millions of years, leading to a conclusion that the flip point for losing all the ice on the planet (ie. including all of the Antarctic ice) was probably somewhere in the range 450 ppm ± 100 pm (that is between 350 ppm and 550 ppm.). So somewhere in this range we could lose all of the ice on the planet with a long run consequence being a 70 metre sea rise.  And to have, effectively, a zero chance of causing such a catastrophe, the world would have to keep the CO₂ level to below the bottom end of the uncertainty range - ie below 350 ppm.  So perhaps this is where the 350 target came from - being the atmospheric CO₂ cap that would need to be adopted if we wanted to guarantee we didn't suffer 70 metres of sea rise over the coming centuries or millennia?

But to set the target for the level of CO₂ in the air to a level that was only low enough to avoid a 70 metre sea rise makes little sense from a here-and-now policy perspective.  It would take many hundreds, possibly several thousands of years for the whole of the Antarctic ice sheet to melt. Well before even a small fraction of that ice sheet melted, human society would have been able to change its economy to restore safe conditions (even after taking into account the difficulties that humans have in making such big changes).  However as discussed above the world faces a very immediate threat of triggering the melting of the Arctic permafrost - with catastrophic near-term consequences.  And the environmental conditions required to prevent this problem are much more stringent in terms of both the size of the reduction of CO₂ levels in the air and the urgency of the required action.  So one would think that the atmospheric CO₂ target should be set by the more immediate and more demanding threat.

Philip Sutton made contact with both James Hansen and Pushker Kharecha, one of Hansen's co-authors of the Target CO₂ paper by email and phone. Kharecha confirmed that Hansen's concern with the 350 ppm target was to avoid the complete loss of all ice on the planet.

James Hansen answered the question more indirectly by making the following points:

• his objective in setting the 350 ppm initial target was to get governments to stop aiming for targets in the 450 ppm and above range
• he thought it was not possible to have a safe climate if there was a permanent loss of the summer Arctic sea ice
• to work out the what the ultimate (not initial) target should be for the CO₂ level in the air, Hansen advised people to use the detail of the Target CO₂ paper
• Hansen had got a huge amount of flack from some other scientists for putting forward even the 350 ppm goal because they said it was 'impossible' to achieve.

So we now know that the 350 target was not aimed at making the immediate restoration of the Arctic sea ice possible but was aimed instead at preventing the very long term risk of losing all the ice from Antarctica.  We also know that Hansen is sticking to this goal for the present for two essentially pragmatic reasons: ie. that pursuing a 350 target will get change in what he sees as a useful direction and that going beyond 350 ppm at this stage seems too hard.

Why is it a bad idea to promote a 350 ppm target?

If our goal is simply to shift governments from goals of 450 ppm or 550 ppm then of course promoting a 350 ppm goal is useful.  But our real goal has to be a safe climate:

• And a safe climate is not possible if the massive carbon stores in the Arctic and sub-Arctic are being mobilised into the atmosphere.
• And to stop the mobilisation of the Arctic/ sub-Arctic carbon stores we must restore the Arctic sea ice and refreeze the permafrost areas. 
• And we need to get this result fast before the flow of methane and CO₂ from the Arctic/sub-Arctic is so strong that it makes it impossibly difficult to cool the earth in time to stop the positive feedback process.

So to promote a 350 ppm goal is simply to promote the wrong goal.  The most important core goal right now is to refreeze the Arctic (to stop the albedo flip and to stop the mobilisation of the carbon stores). Once we focus on refreezing the Arctic, we can relatively easily work out what the compatible atmospheric level of CO₂ would be.  James Hansen and his co-authors in the Target CO₂ paper argued that to restore the Arctic sea ice to its area of 25 years ago an the atmospheric CO₂ level might have to be somewhere in the range of ~300-325 ppm.  If we want zero risk of failure we must aim for the bottom end of this range, so we can say that the atmospheric CO₂ target needs to be 300 ppm or possibly less - note the tilde on the ~300 above (it means "approximately 300"). It can be assumed that if we get the Arctic sea ice back to its full extent then the sub-Arctic permafrost will be refrozen too.  But this assumption needs to be tested scientifically.

To understand the significance of aiming for 300 ppm CO₂ in the air we need to trace the causative chain. To refreeze the Arctic, the earth has to be cooler, on average by about 0.3ºC as estimated by Spratt and Sutton in the book Climate Code Red (Reference: Refreezing the Arctic).

To keep promoting a 350 ppm target is to miseducate the public and governments and businesses about what is actually needed.  It also means that not enough promotional effort is being put into the real goal which is to refreeze the Arctic, and also it obscures the urgency of the required action.

And once people know that the real goal is to refreeze the Arctic, how can anyone keep arguing for an atmospheric CO₂ level that would block the refreezing effort?

Recent 350 campaign successes

There's no doubt that the promotion of the 350 target has been very successful.  At the the Poznan Conference in Poland (December 2008) the 350 target was adopted by the International Youth Climate Network, the 49 least developed countries and by Al Gore (see Gore's address at Poznan).  (Reference: Successes of the 350 campaign).

Perhaps we should just accept the contradiction between a 350 ppm target and the goal of refreezing the Arctic and keep riding the 350 pm bandwagon to help give it more momentum?

But there is another way to read the success of the 350.org campaign.  It demonstrates that if campaigners take what they believe is the right goal out to the public and build a massive enough campaign then what was once seen as an impossible ask can be made into something that is politically feasible.  The very success of the 350.org campaign suggests that if a 300 ppm target had been advanced by Hansen in the first place, and this had been picked up by Bill McKibben, then by now we would be celebrating the adoption of a 300 ppm target by many of the participants in the Poznan Conference!

What should we do now?

We need to:

• focus our efforts on refreezing the Arctic. And we need to make sure that this is done fast enough to avoid a cascade of damaging effects from the continuation of the earth's 'fever'.
• enter into a dialogue with climate scientists to work out the best way to refreeze the Arctic and to work out how fast it needs to be done.
• help the 350.org campaign find a way to transition their efforts to support the refreezing of the Arctic, and to rename their campaign
• we need to encourage other activist groups to promote the refreezing of the Arctic and to promote an atmospheric CO₂ level that will make that possible. On the basis of current knowledge it looks like under 300 ppm is the best target if we want a negligible risk of failure.. 

We should take heart from the fact that other senior climate scientists are now contemplating what even Jim Hansen thought was too hard politically.  For example, Professor John Schellnhuber, director of the Potsdam Institute for Climate Impact Research in Germany and one of the leading climate scientists in Europe, told the Guardian in September 2008 that only a return to pre-industrial levels of CO₂ would be enough to guarantee a safe future for the planet.  He said even a small increase in temperature could trigger one of several climatic tipping points, such as methane released from melting permafrost, and bring much more severe global warming.  

"It is a very sweeping argument, but nobody can say for sure that 330ppm is safe," he said. "Perhaps it will not matter whether we have 270ppm or 320ppm, but operating well outside the [historic] realm of carbon dioxide concentrations is risky as long as we have not fully understood the relevant feedback mechanisms".
(Reference: Safe climate target: Adam 2008)

As the authors of the ClimateSafety report say:

"Any proposal for a target higher than 300ppmv would imply confidence that it is safe to leave the Arctic sea ice melted, and an assumption that this would not bring about the train of consequences just described. This is, implicitly, the view of all the major nations and organisations involved in setting climate policy. Accordingly, they must be challenged to provide a reasoned argument as to why leaving the Arctic Ocean free of ice in summer is safe. If they cannot, the only acceptable course of action is clear." (Reference: General references: Hawkins et al. 2008)

References

General references:

Spratt, D. & Sutton, P.  (2008).  Climate Code Red: The case for emergency action.  Scribe: Melbourne, Australia.
http://climatecodered.net/
http://www.scribepublications.com.au/book/climatecodered/

Hawkins, R., Hunt, C., Holmes, T. & Helweg-Larsen, T.  (2008).  Climate Safety: In case of emergency...  PIRC: Machynlleth, Wales, UK
http://climatesafety.org/

Illustrations for this pages:

Unless indicated otherwise the illustrations are taken from the PIRC report "Climate Safety", cited above.

Arctic sea ice loss:

Young, K., "Canada’s Inuit facing ‘cultural genocide,’ says Arctic expert", Canada.com,
23 November 2007. Available online at: http://www.canada.com/cityguides/winnipeg/info/story.html?id=886e1d36-01c8-4ef6-8d60-a9460b815f62&k=34394

Connor, S., "Scientists warn Arctic sea ice is melting at its fastest rate since records began", Independent, 15 August 2007. Available online at: http://www.independent.co.uk/news/science/ scientists-warn-arctic-sea-ice-is-melting-at-its-fastest-rate-since-records-began-461632.html

Revkin, A. C., "Retreating Ice: A blue Arctic Ocean in summers by 2013?", International Herald Tribune, 1 October 2007. Available online at: http://www.iht.com/articles/2007/10/01/ sports/arcticweb.php

Maslowski, W. (2006) “Causes of changes in Arctic sea ice”, AMS ESSS Seminar, 3 May 2006

Maslowski, W., J. Clement, et al. (2006) “On oceanic forcing of Arctic climate change”, Geophysical Research Abstracts 8: 05892.

Serreze, M. "Arctic Sea Ice Decline May Trigger Climate Change Cascade, According To New CU-Boulder Study", University of Colorado at Boulder, March 15, 2007.
http://www.colorado.edu/news/releases/2007/109.html

Permafrost melting:

Lawrence, D. M. et al., “Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss”, Geophysical Research Letters, Vol. 35, L11506, 2008, doi:10.1029/2008GL033985.

Edward A. G. Schuur et al., “Vulnerability of permafrost carbon to climate change: implications for the global carbon cycle”, Bioscience, Vol. 58, No. 8, September 2008, doi:10.1641/B580807, pp. 701-714.

Shakhova, N. et al., “Anomalies of methane in the atmosphere over the East Siberian shelf: Is there any sign of methane leakage from shallow shelf hydrates?”, Geophysical Research Abstracts, Vol. 10, EGU2008-A-01526, 2008, SRef-ID: 1607-7962/gra/EGU2008-A-01526
Available online at: http://www.cosis.net/abstracts/EGU2008/01526/EGU2008-A-01526.pdf?PHPSESSID=c0ae24c54d

Atmospheric warming and masking processes:

Ramanathan, V. & Y. Feng, “On avoiding dangerous anthropogenic interference with the climate system: Formidable challenges ahead”, Proceedings of the National Academy of Sciences, vol. 105, 23 September 2008, pp. 14245-14250.

Ocean acidification:

Nogrady, B., "Southern Ocean close to acid tipping point", ABC Science Online, 11 November 2008.  Available online at: http://www.abc.net.au/news/stories/2008/11/11/2416190.htm

Greenland ice sheet:

Gregory, J. M. et al., “Climatology: Threatened loss of the Greenland ice-sheet”, Nature, vol. 426, 8 April 2004, p. 616, doi:10.1038/428616a.

Hansen and the Target CO₂ paper:

Hansen, J., Mki. Sato, P. Kharecha, D. Beerling, R. Berner, V. Masson-Delmotte, M. Pagani, M. Raymo, D.L. Royer, and J.C. Zachos, 2008: Target atmospheric CO₂: Where should humanity aim? Open Atmos. Sci. J., 2, 217-231, doi:10.2174/1874282300802010217.
http://pubs.giss.nasa.gov/abstracts/2008/Hansen_etal.html

Commentary by Hansen on the "Target atmospheric CO2" paper:
http://www.columbia.edu/~jeh1/mailings/20081030_Target.pdf

http://pubs.giss.nasa.gov/authors/jhansen.html 
http://www.columbia.edu/~jeh1/

Historic atmospheric CO₂ levels:

"Atmospheric CO₂ values (ppmv) derived from in situ air samples collected at Mauna Loa, Hawaii, USA" (1958-2007)
http://cdiac.esd.ornl.gov/ftp/trends/co2/maunaloa.co2

.Origin of the 350.org target:

http://350.org/understanding-350#6
http://350.org/en/about/science

Refreezing the Arctic

Spratt, D. & Sutton, P.  (2008).  Climate Code Red: The case for emergency action.  Scribe: Melbourne.

Successes of the 350 campaign:

49 least developed countries endorse a 350 ppm target and the International Youth Climate Network also endorsed a 350 target. at Poznan, December 2008.
http://www.350.org/en/about/blogs/changing-climate-targets-poland

Al Gore urges Poznan delegates to adopt a 350 ppm target, rather than 450 ppm or higher.
http://350.org/en/about/blogs/gore-speaks-and-he-speaks-350

Safe climate target:

Adam, D., "Roll back time to safeguard climate, expert warns", Guradian.co.uk,
15 September 2008. Available online at: http://www.guardian.co.uk/environment/2008/sep/15/climatechange.carbonemissions

 

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300 ppm CO2 or below is the stabilisation target for a safe climate.
Lets restore the Arctic sea ice.