Sections

Services

Information

UK United Kingdom

IPCC climate trends: blueprints for tipping points in Earth’s climate

The Intergovernmental Panel on Climate Change Fifth Assessment Report, authored by 209 lead authors, 50 review editors from 39 countries, and by more than 600 contributing authors from 32 countries, with…

The IPCC reports are the most authoritative source of climate information we have. EPA/BERTIL ENEVAG ERICSON / TT SWEDEN OUT

The Intergovernmental Panel on Climate Change Fifth Assessment Report, authored by 209 lead authors, 50 review editors from 39 countries, and by more than 600 contributing authors from 32 countries, with feedback from many hundreds of reviewers, is an authoritative summary of the scientific peer reviewed literature relating to climate science, global warming and future trends in the atmosphere-ocean system.

It is a document humanity can only ignore at its own peril.

Mean global warming of the atmosphere since 1850 reached about 0.9C (above pre-industrial). This translates to mean warming over the continents of about 1.5C and during 1986-2005 over 3C in polar regions. Once the masking effect of sulphur aerosols is discounted, the mean global climate has already exceeded 2C (see Figure 2).

Warming of the ocean accounts for more than 90% of the extra energy absorbed by Earth during 1971-2010. The warming is directly related to the rise in radiative forcing/energy of the Earth system (see Figures 1 and 2). Temperature increases in ocean depths above 700m and below 700m are shown in Figure 3.

Figure 1: past and future climate trends (a) mean global temperature; (b) Northern Hemisphere sea ice extent; © ocean pH. IPCC - http://www.climatechange2013.org/images/uploads/WGIAR5-SPM_Approved27Sep2013.pdf

The AR5 report exposes the myth global warming has halted over the last 20 years or so. A combination of rising sulphur aerosol emissions from around 2001, a decline in sunspot activity and La-Nina events resulted in a relative lull in warming, while peak temperatures were reached in 2005 and 2010 and warming of the oceans continued (see Figure 3)1.

Figure 2: global mean positive and negative radiative forcings since 1750. Global average radiative forcing estimates and ranges for anthropogenic carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and other important agents and mechanisms. The net anthropogenic radiative forcing and its range are also shown. source

AR5 future climate projections may convey an impression future temperature rise can be expressed by smooth or gradual trajectories, as in Figure 1. Such a gradual rise might allow sufficient time to mitigate further warming. But the role of sulphur dioxide emissions in mitigating future temperature rise depends on industrial practices and thus remains unclear. Reduction in sulphur emissions associated with clean air policies resulted in temperature spikes about 1975, which could happen again.

The extreme rates of global warming experienced since about 1975 result in feedback effects from warming oceans, drying land sectors, release of methane from permafrost and Arctic lakes and release of CO2 from fires. A continuation of these processes is bound to bring on a synergy of warming processes and potential irreversible tipping points in the climate system.

Figure 3: ocean temperatures and heat contents: a) 0–100 m depth mean temperature anomaly; b) 0–700 m depth global ocean heat content. zoomable= http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/index3.html

The rate at which climate forcing (change in energy/heat) in the atmosphere/ocean/cryosphere system rose between 1850-2005 (about 0.01 Watt/m2/year) is more than an order of magnitude faster than during the last glacial termination 17,000 – 10,000 years ago (about 0.00045 Watt/m2/year).

The lesson from the history of the atmosphere/ocean system is that abrupt climate changes at rates such as at present resulted in mass extinction of species. According to Kevin Trenberth, chief scientist of the National Center for Atmospheric Research in Boulder, Colorado:

Some of the human-induced changes are occurring 100 times faster than they occur in nature … And this is one of the things that worries me more than climate change itself. It’s actually the rate of change that’s most worrying… Ecosystems are not prepared for this jolt … And neither are many human endeavors, built around assumptions about how hot it’s going to be, how much it’s going to rain on our croplands, and how high the seas will rise.

The AR5 report says CO2 or CH4 release from thawing permafrost to 2010 are in the range of 33–400 gigatonnes. But not enough focus is drawn to this factor. David Wasdell, Director of the Meridian Institute, made this point earlier, stating:

The Feedback Crisis in Climate Change highlights the all-too-real possibility of runaway climate change, driven by the naturally occurring positive feedback loops of the biosphere. It raises issues of the most fundamental and urgent nature for the world community and calls in question the effectiveness of current strategic responses to global warming.”

The role of fire as a major feedback to global warming has not received enough focus in the AR5 report. According to Professor of Environmental Change Biology, David Bowman, natural and anthropogenic forest and bushfires release 2 to 4 gigatonnes of carbon per year.

He says, “Currently all sources of fire (landscape biomass) cause CO2 emissions equal to 50% of those stemming from fossil-fuel combustion (2 to 4 PgC year−1 versus 7.2 PgC year−1)”. With rising temperatures, a distinction between “natural” and “anthropogenic” fires is obscured. The AR5’s absence of focus on fire as a major feedback remains inexplicable.

Climate change in the 20th and 21st centuries constitutes an unprecedented event horizon - a shift of state in the terrestrial atmosphere. In a new paper Hansen et al state “Burning all fossil fuels, we conclude, would make most of the planet uninhabitable by humans, thus calling into question strategies that emphasize adaptation to climate change.”

No amount of media and internet spin can alter the essential evidence for runaway climate change presented by the AR5 report, nor the consequences for future generations and nature. Even before publication of the AR5 a loud chorus of critics emerged all over the media, none of whom are raising any valid scientific points.

As pointed out by Andy Pitman, those who deny the science will not indicate which evidence will convince them climate science and the IPCC are essentially correct. But for the rest of us, ignoring the evidence of AR5 would be imprudent in the extreme.

Good planets are hard to come by.

1 The negative radiative forcing of sulphur aerosols as shown in Figure 3 is in the range of -0.23 to -0.77 Watt/m2 for direct aerosol effects and -0.55 Watt/m2 for cloud aerosol effects. When combined the forcings are in the range of -0.78 to -1.32 Watt/m2.

According to the accepted mean climate sensitivity of 3C per doubling of CO2, then ¾ of the radiative forcing translates to temperatures in degrees C, the negative temperature effect of aerosols (combined direct and aerosol cloud effects = -0.78 to -1.32 Watt/m2) correlates with -0.58 degrees C to -0.99 degrees C

When this is added to the continental warming of +1.5 degrees C the mean global continental temperature anomaly exceeds 2C. The reference for climate sensitivity is to Hansen et al. 2013

Join the conversation

60 Comments sorted by

  1. Michael Sheehan

    Geographer at Analyst

    "But the role of sulphur dioxide emissions in mitigating future temperature rise depends on industrial practices and thus remains unclear."
    Alternatively we could just shoot bombs of sulphur into the atmosphere.

    report
    1. Mulga Mumblebrain

      Rocket surgeon

      In reply to Michael Sheehan

      Why not a thermonuclear war? The way that the rotting Yankee Reich is going about threatening all and sundry, it's pretty likely that they will provoke a showdown with Russia, which will not tolerate another round of US-organised territorial fragmentation.

      report
    2. Michael Sheehan

      Geographer at Analyst

      In reply to David Arthur

      Yeah, I was just raising the fact that we are not necessarily beholden to uncertain future industrial practices.

      report
    3. David Arthur

      resistance gnome

      In reply to Michael Sheehan

      "we are not necessarily beholden to uncertain future industrial practices":

      I see what you mean: we could go flat out as various commentators and Cabinet Ministers exhort, and make damned sure of the job on ourselves.

      report
    4. Michael Sheehan

      Geographer at Analyst

      In reply to David Arthur

      Well, my example had somewhat more modest aims than that. I was speaking from a purely logical perspective.

      report
    5. David Arthur

      resistance gnome

      In reply to Michael Sheehan

      Modest aims? Read up about geoengineering, eg Rasch et al, "An overview of geoengineering of climate using stratospheric sulphate aerosols" Phil. Trans. R. Soc. A 13 November 2008 vol. 366 no. 1882 4007-4037 doi: 10.1098/rsta.2008.0131 http://rsta.royalsocietypublishing.org/content/366/1882/4007.full

      Pure logic tells us that ozone depletion isn't really a bright idea.

      My own preference is for more limited imposed solar radiation reductions, concentrating on putting fairly inert (ie not highly reactive) particles in the Arctic stratosphere during their summer months (ref MacCracken et al, "Climate response to imposed solar radiation reductions in high latitudes", arth Syst. Dynam., 4, 301–315, 2013 www.earth-syst-dynam.net/4/301/2013/ doi:10.5194/esd-4-301-2013).

      report
  2. Philip Dowling

    IT teacher

    "209 lead authors, 50 review editors from 39 countries, and by more than 600 contributing authors from 32 countries, with feedback from many hundreds of reviewers"
    This seems to quite a "committee" to me, in fact, quite an industry in itself.
    I always cringe a little when I read the term "the science".
    Kepler's laws.
    Newtonian mechanics.
    Einstein's Theory of Relativity.
    Heisenberg Uncertainty Principle.
    Not a committee in sight. However they did rely on other people's work of course…

    Read more
    1. Mulga Mumblebrain

      Rocket surgeon

      In reply to Philip Dowling

      Garbage from stem to stern. The IPCC process does nothing but collate the work of real scientists working according to time-honoured scientific principles, which summation is then vetted by countries like Saudi Arabia, hence becomes dumbed-down, then is misrepresented, lied about and abused by denialist trolls. You forgot to mention that peer review is a Communist scam by water-melon gate-keepers. Watch out, or your services might be dispensed with, in favour of the next generation of fanatics.

      report
    2. David Arthur

      resistance gnome

      In reply to Philip Dowling

      Your rebuttal is irrelevant, just wait for the next El Nino. It might even be on its way already, which is why there's so much dry bush.

      Much bush up there Turramurra way?

      report
    3. Peter Redshaw

      Retired

      In reply to Philip Dowling

      Phillip, if you went and read up on your history on each of these Theories you would find that science has debated them extensively at the time as well as up to the present day. You would have found that there have been committees who have assessed and reassessed each of those theories at the time and since as new knowledge and theories are developed. That is the nature of science and the scientific processes. Knowledge does not sit in isolation.

      report
    4. Philip Dowling

      IT teacher

      In reply to David Arthur

      The bush along the Comennarra Parkway has never been as thick since the 1994 bushfires, when the sun was red for a week as fires burned at both end of Turramurra. Got to within 100 m of my house.

      report
    5. Philip Dowling

      IT teacher

      In reply to Peter Redshaw

      Yes, but sometimes these committees have been wrong. I have no problem with committees vetting work, but in deciding whose work to vet.
      There are an enormous number of papers that would seem to provide insights into various issues but their value is diminished by dragging in climate change almost as an afterthought.

      report
    6. David Arthur

      resistance gnome

      In reply to Philip Dowling

      Don't worry. I don't think Sydney is projected to have long term rainfall declines, but seasonality (ie lots of pleasant warm wet weather followed by pronounced seasons of hot dry weather).

      Sooner or later, bushfires will get your place - unless they clear all the bushland for environmental refugee detention camps.

      report
    7. Philip Dowling

      IT teacher

      In reply to David Arthur

      But David, I read on the Department of Climate Change website that rainfall in south-eastern Australia was in long-term decline. At least that was what was there until all the floods arrived and they changed it.

      report
    8. Andrew Vincent

      Marketing . Communications . Multimedia

      In reply to Philip Dowling

      Well I suppose you get away with saying what you like if you stick to sweeping generalisations. What's an example of a paper that you think has been unfairly excluded?

      report
    9. David Arthur

      resistance gnome

      In reply to Philip Dowling

      Err, Turramurra is ~20 km from the Tasman Sea, South-East Australia extends a couple of thousand km further away from the coast than that. The floods were largely on the East Coast.

      My observation of Sydney residents that many of them can't tell the difference between Sydney and NSW, or even between Sydney and Australia.

      report
    10. Philip Dowling

      IT teacher

      In reply to David Arthur

      The floods filled the Wyangala and Burrinjuck and Hume dams. Incidentally I have lived in Victoria, South Australia and Queensland as well as the other side of the sandstone curtain.

      report
    11. Chris O'Neill

      Victim of Tony Abbotts Great Big New Tax

      In reply to Philip Dowling

      "There are an enormous number of papers that would seem to provide insights into various issues but their value is diminished by dragging in climate change almost as an afterthought."

      Papers on what?

      report
    12. David Arthur

      resistance gnome

      In reply to Philip Dowling

      Fair comment Mr Dowling. That's for now.

      If you go to http://www.longpaddock.qld.gov.au/queenslanddroughtmonitor/queenslanddroughtreport/index.php, you can click on "Latest coloured drought situation map - opens in new window (GIF, 230kB, last updated 09:36 18 Sep 2013)".

      You'll also see that relative monthly topsoil moisture isn't looking too flash apart from the Southern and Central highlands (http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0011/475697/NSW-Seasonal-Conditions-Summary-September-2013.pdf)

      report
    13. Philip Dowling

      IT teacher

      In reply to David Arthur

      David, May I presume that you have read "Kings In Grass castles"?

      report
    14. Peter Redshaw

      Retired

      In reply to Philip Dowling

      Phillip, you seem to demonstrate a complete lack of understanding of the way scientific knowledge/research/theories are debated and debated and debated and rehashed and rehashed and rehashed within the scientific community. Climate change dragged in almost as an afterthought. Where do you get that from?

      Scientific knowledge does not operate in isolation from itself. If science is operating properly, as new primary research becomes available, it is always assessed against existing knowledge across a whole range of disciplines. Sometimes research within one disciplinary field will be unexpectedly found to have implications within a completely different discipline than that necessarily associated with that discipline. This is where we get the saying of something coming completely out of left field and is often how completely new knowledge and industries are developed.

      report
    15. Philip Dowling

      IT teacher

      In reply to Peter Redshaw

      I have read a number of papers where the results have no connection with climate change but the discussion is all about climate change.
      It is obvious to anyone who has read numerous scientific studies where the logical is replaced with the ideological.

      report
  3. Mulga Mumblebrain

    Rocket surgeon

    What we really know, from looking at the scene of the greatest disruption so far, the Arctic north, is that some very troubling tipping-points may already have been passed, and all this carnival of lies, misrepresentation, idiocy, ignorance and unadulterated Rightwing nastiness has been successful. If, as experts on Arctic marine conditions, and the possibility of large emissions from submarine clathrates of methane believe is possible, and, indeed, highly possible, large amounts of methane are vented…

    Read more
  4. Mark McGuire

    climate consensus rebel

    Quote Prof. Glikson: "As pointed out by Andy Pitman, those who deny the science will not indicate which evidence will convince them climate science and the IPCC are essentially correct." Sir, with the greatest respect, I responded with a link to an academic site and will do so again - 1. Temperatures 5 to 10 degrees Fahrenheit higher than today. 2. Sea level 75 to 120 feet higher than today. 3. No permanent arctic sea ice cap. 4. Very little ice on Antarctica. 5. Very little ice on Greenland. Also included a link to current carbon(sic) levels. As that description of our earth is nothing like today, despite carbon(sic) levels at same levels, a convincing scientific explanation would be a start.
    http://www.sciencedaily.com/releases/2009/10/091008152242.htm http://climate.nasa.gov/400ppmquotes/

    report
    1. Gary Murphy

      Independent Thinker

      In reply to Mark McGuire

      Scary huh? Is that where we will be when the earth's energy budget again balances? I wonder how long it will take.

      report
    2. John Vacey

      Sciolist

      In reply to Mike Hansen

      Thanks for that Mke. I was wondering (with no respect whatsoever) what the hell that MM's waffle had to do with his chosen Andrew Glikson quote.

      report
    3. Andrew Glikson

      Earth and paleo-climate scientist

      In reply to Mark McGuire

      This comment was responded to earlier by Andy Pittman, who wrote:

      "but that is like saying "I'll only believe an aeroplane can crash" after the event. Its too late then."

      report
    4. Peter Turner
      Peter Turner is a Friend of The Conversation.

      Thinker

      In reply to Mark McGuire

      Sir (Mark), with the greatest respect, I will purchase Home insurance when:
      (1)I have been burgled twice,
      (2)the fan heater catches fire and burns out the lounge,
      (3)the big gum in the garden falls onto the roof and squashes my uncle fred flat (his widow WILL sue!)
      (4) The semi heading straight for the front door with no brakes gets within 5 metres.
      Absolute certainty is only granted with the benefit of hindsight - if this what will convince, how come there is good money in Insurance?

      report
    5. John Newton

      Author Journalist

      In reply to Mike Hansen

      Mike et al - ignore them. If they want to publish they can submit to the editors. but these endless and mindless denialist posts do nothing for the site.

      report
    6. Chris O'Neill

      Victim of Tony Abbotts Great Big New Tax

      In reply to Mark McGuire

      So you'll be convinced that the predictions are true when they actually happen.

      Obviously that means we have nothing to worry about.

      report
  5. Gil Hardwick

    anthropologist, historian, novelist, editor and publisher at eBooks West

    I continue to wonder, Andrew, that you climate scientists persist in your apparent refusal to log human population growth data against your planetary human impact data. Surely it's a straightforward thing to do, intuitively sensible, especially being so commonly and irrefutably available.

    Human population did not reach 1 billion until 1804. In 1850 (using your timeline), it was still less than 1.2 billion; not reaching 2 billion until 1926, and three billion until around 1960, 4 billion in 1974…

    Read more
    1. Gil Hardwick

      anthropologist, historian, novelist, editor and publisher at eBooks West

      In reply to David Arthur

      That's not a fair comment, David. This is no longer the albeit short-lived "age of the specialist" it is the age of broad interdisciplinary collaboration.

      Universities today are not only working flat out to ensure that undergraduates receive a broadly based education before they specialise, they actively assess students on their willingness and ability to collaborate across disciplinary thresholds, and further fund research through collaborative research centres.

      And yes, we have to be looking…

      Read more
    2. David Arthur

      resistance gnome

      In reply to Gil Hardwick

      I think it is pretty fair, regarding the bucketing climate science receives in the anti-science press.

      Climate science is of itself an interdisciplinary activity, perhaps exemplified by James Hansen (http://www.columbia.edu/~jeh1/). I recommend his "Dreams of My Grandchildren" - plenty of interdisciplinary stuff there.

      Meanwhile, for a considered appraisal of population issues, this morning's Ockham's Razor is worthwhile (Gregory OAtes, "Preparing for population growth", http://www.abc.net.au/radionational/programs/ockhamsrazor/preparing-for-population-growth/4980342).

      I see you've got oodles to say, not all of which directly pertains to climate. Perhaps you could contribute to the discussion?

      report
    3. Gil Hardwick

      anthropologist, historian, novelist, editor and publisher at eBooks West

      In reply to David Arthur

      The discussion, David, is on climate change and its effects. Yes, I checked, the title explicitly reads, "IPCC climate trends: blueprints for tipping points in Earth’s climate."

      I don't know who is bucketing climate science, or who the "anti-science press" might happen to be beyond a few cheap tabloids and sectional interest groups. They give us a bucketing too, but I don't see anyone whinging and moaning about that. We just have to cop it sweet and get on with the job.

      Who writes tabloid drivel…

      Read more
    4. Andrew Glikson

      Earth and paleo-climate scientist

      In reply to Gil Hardwick

      Gil

      There is no doubt the exponential growth of human populations, with major effects on land and marine resources, pollution and a myriad other consequences, is a central issue. However, the shift in state of the atmosphere is now following its own laws, based on physics and chemistry, independent of the population issue.

      Perhaps rather than pointing the finger in this regard toward climate scientists it would be more suitable to question proponents of open-ended growth at all costs, including economists, vested interests and their mouthpieces.

      report
    5. Gil Hardwick

      anthropologist, historian, novelist, editor and publisher at eBooks West

      In reply to Andrew Glikson

      I don't know who is pointing the finger at climate scientists, I'm not.

      My point, which apparently needs to be made explicit, is that on a per capita basis anthropogenic impacts are diminishing.

      Doesn't that indicate to anybody yet, that management regimes we have been putting in place for the past 30 years are working?

      Doesn't it make far more sense to stop quibbling, and audit the programs that are known to work by which I mean bring positive benefits in natural resource, catchment and…

      Read more
    6. David Arthur

      resistance gnome

      In reply to Gil Hardwick

      All the stuff you propose, Gil, ARE being done, and it's being done by other people.

      It is the job of climate scientists, Gil, to study climate. That's wht they do.

      It's the job of anthropologists to take the climate results, and log it on a per capita basis.

      report
    7. Trevor S

      Jack of all Trades

      In reply to Gil Hardwick

      "How is all that to be delivered without further impacts on the planet? Can it?"

      No but the damage is being done by the 1 Billion in the West not the other 6 Billion.

      I read somewhere that from 1900 to about now, population has increased 5x and yet consumption of resources has increased 40x. Population is an environmental issue, no doubt but CO2e is THE issue and we in the West are the 'cause.

      To achieve the cuts necessary in time with some sort of equity, we need a 90% (or so) reduction…

      Read more
    8. Jenny Goldie

      president at Sustainable Population Australia

      In reply to Gil Hardwick

      Gil

      I think you're being a little hard on climate scientists. I know quite a few who do make the population connection. Nevertheless, the nexus between climate and population does need to be addressed more thoroughly and to that end Sustainable Population Australia is organising this year's Fenner Conference in Canberra on October 10 and 11, the title of which is "Population, Resources and Climate Change: implications for Australia's future". There are still a few seats available and you can book…

      Read more
    9. Donald Runcie

      retired

      In reply to Gil Hardwick

      comment on gill hardwick's post: increase in population will lead to more innovation (Shennan- University College London) perhaps more chance of a solution or solutions

      report
    10. Alice Kelly
      Alice Kelly is a Friend of The Conversation.

      sole parent

      In reply to Gil Hardwick

      "you climate scientists persist in apparent refusal to log human growth data against your planetary human impact data." That's not their job. Their "dreaming" is the human impact on climate and climate data as it stands. Stick to your own "dreaming" Gil

      report
    11. Michael Sheehan

      Geographer at Analyst

      In reply to Trevor S

      Trevor, so basically you plan is for everyone to stop living. OK, that will sell well. Not.

      report
  6. Rene Oldenburger

    Haven't got one

    Some scientists claim that animal agriculture produces more than 100 million tonnes of methane is a major contributor.

    So if we all become vegetarians and stop eating the meat especially from cows, what sort of difference would that make?

    report
    1. Gil Hardwick

      anthropologist, historian, novelist, editor and publisher at eBooks West

      In reply to Rene Oldenburger

      It would make things worse, Rene, wouldn't you think?

      If we stop slaughtering so many animals and eating them they would be in even greater plague proportions, and causing even worse bio-methane production.

      As things stand, right now there are over 110 million sheep and 28 million cattle in Australia, to 23 million humans.

      The solution to the particular dilemma you raise, already being trialled by scientists [HELLO], is low-methane producing native forage and pasture plants.

      report
    2. Peter Turner
      Peter Turner is a Friend of The Conversation.

      Thinker

      In reply to Rene Oldenburger

      It's complex, I think. Would have to compare the carbon footprints of each process (eg. large scale veggies may require lots of diesel for machinery) but worth looking at - also, as is being done with pigs, a lot of methane is captured and used as replacement fuel for piggeries- less CO2 than electricity from coal.

      report
    3. Chris O'Neill

      Victim of Tony Abbotts Great Big New Tax

      In reply to Gil Hardwick

      "If we stop slaughtering so many animals and eating them they would be in even greater plague proportions, and causing even worse bio-methane production."

      Err, so it never occurred to you that humans are in control of the reproduction of farm animals?

      report
  7. Andrew Glikson

    Earth and paleo-climate scientist

    CORRECTION

    The statement at the end note "The negative radiative forcing of sulphur aerosols as shown in Figure 3 is in the range of -0.23 to -0.77 Watt/m2 for direct " should read:

    "The negative radiative forcing of sulphur aerosols as shown in Figure 2 is in the range of -0.23 to -0.77 Watt/m2 for direct"

    report
    1. Alice Kelly
      Alice Kelly is a Friend of The Conversation.

      sole parent

      In reply to Andrew Glikson

      Andrew, 400 ppm and still rapidly rising. Is there any conclusion after this last summer in the arctic, about the potential total amount, and impact of new CO2 and methane releases, on the atmospheric total, and when? Do we have to wait, or are there currently any ideas which are becoming apparent ? There is an idea that the amounts could be huge.

      report
  8. Andrew Glikson

    Earth and paleo-climate scientist

    Alice

    Last time the atmosphere had a CO2 level of 400 ppm was in the Late Pliocene about 3 million year ago. During the ice ages of the last 800,000 years levels varied between 180 ppm (glacial periods) and 280 ppm (interglacial periods). Views vary regarding the upper stability threshold of the Antarctic ice sheet - in most views it is approximately 500 ppm CO2, according to other it is higher. The rate of ice melt depends on both temperature level and the rate of temperature rise. Current CO2 rise rates exceed 2 ppm/year, faster than recorded since 55 Ma.

    report
    1. Alice Kelly
      Alice Kelly is a Friend of The Conversation.

      sole parent

      In reply to Andrew Glikson

      Yeah, thanks for your article and answer, ignoring the noise above this is sobering and begs the question about 'getting on with it'.

      report
    2. Chris O'Neill

      Victim of Tony Abbotts Great Big New Tax

      In reply to Andrew Glikson

      "the upper stability threshold of the Antarctic ice sheet - in most views it is approximately 500 ppm CO2"

      which is less than 50 years away even at the current rate.

      report
    3. Alice Kelly
      Alice Kelly is a Friend of The Conversation.

      sole parent

      In reply to Chris O'Neill

      You'd have to think that much of West Antarctica which sits on a bed of granite under sea level will start to disintegrate at a faster rate. It's already happening from underneath because of extra heat in the ocean. Chris, did you see this one?
      http://www.youtube.com/watch?v=usDzh7l5HZw
      There's another one of Greenland which shows a gigantic valley down the centre. As it melts the earths crust is rising, and sinking elsewhere, i.e.. the Torres Straight.

      report
    4. Chris O'Neill

      Victim of Tony Abbotts Great Big New Tax

      In reply to Alice Kelly

      "You'd have to think that much of West Antarctica which sits on a bed of granite under sea level will start to disintegrate at a faster rate."

      Of course, but for people who think East Antarctica is relatively stable, well ....

      report