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Beyond two degrees celsius: sulphur won’t save us for long

The Earth energy balance – the difference between energy/heat absorbed by the Earth from solar radiation and the energy/heat emitted back to space – is currently offset by the cooling effect of sulphur…

Believe it or not, sulphur emissions are keeping us cooler. lillicomanche/flickr

The Earth energy balance – the difference between energy/heat absorbed by the Earth from solar radiation and the energy/heat emitted back to space – is currently offset by the cooling effect of sulphur aerosols.

These aerosols are emitted by fossil fuels and industry, and effectively act as a global geo-engineering process.

Had it not been for this short-lived cooling effect the internationally agreed maximum temperature target of 2°C would already be transcended.

According to the Intergovernmental Panel on Climate Change, mean global temperature has risen by 0.8°C since 1880, which translates to more than 4°C in the polar region of northern Canada, Greenland and Siberia.

This triggered ice melting that accelerated between 2002 and 2010, and a related sea level rise at a rate of up to 3.2 mm per year between 1993 and 2010.

The melting of Arctic ice leads to increased evaporation and can result in the advance of cold fronts into the north Atlantic.

Prior to the Copenhagen conference in 2009, the European Union obtained the agreement of relevant partners, including China, India, Russia, and the United States, to commit to an upper two-degree ceiling on further rise in mean global temperature in order to avoid the risk of dangerous climate change.

But a rise beyond two degrees may lead to tipping points in the atmosphere and ocean system.

Global temperatures in 1880 …

… compared to today. Source: NASA/GISS

As stated by the NASA climate science group:

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. The largest uncertainty in the target arises from possible changes of non-CO2 forcings. An initial 350 ppm CO₂ target may be achievable by phasing out coal use except where CO₂is captured and adopting agricultural and forestry practices that sequester carbon. If the present overshoot of this target CO₂is not brief, there is a possibility of seeding irreversible catastrophic effects.

With current CO₂ levels rising to around 28,000 million tonnes by 2010, the NASA study [1] implies global warming committed to reach 2.3 degrees once the aerosol effect dissipates.

This effective, though unintended, geoengineering measure, acting as a shield from a near-doubling of global warming, also lowers ocean pH on top of CO₂ sequestration.

Had the proposed Australian reduction of 5% in the rate of carbon emissions by 2020 been a figure adopted world-wide, global emissions would be reduced by an amount hardly causing a dent in the current trajectory toward levels at which the polar ice sheets are further destabilised.

It is not clear whether deep reductions in carbon emissions will be sufficient to stem the amplifying feedbacks associated with greenhouse gas warming and ice/water interactions.

Barring an indefinite maintenance of sulphur aerosol emissions, deep emission cuts need to be accompanied by atmospheric CO₂ draw-down by means of fast-track tree planting, application of biochar methods and chemical CO₂ sequestration.

As shown by the intensifying spate of extreme weather events around the globe the alternative bears no contemplation.

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31 Comments sorted by

  1. James Szabadics

    BSc

    Andrew appears to be perhaps unaware of peer reviewed research on sea ice loss when he claims that accelerated arctic only sea ice melt (Antarctic sea ice has increased in the same period) was due purely to GHG driven air temperature changes. Read peer reviewed science on this subject here which explains that wind patterns drive rapid arctic sea ice loss:
    http://www.the-cryosphere-discuss.net/5/1311/2011/tcd-5-1311-2011.html

    Andrew also appears to be perhaps unaware of peer reviewed research on…

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  2. Marc Hendrickx

    Geologist

    Andrew is hanging his hat on a forcing whose level of scientific understanding is described by the IPCC as "Low to medium". The direct affect of aerosols is estimated by the IPCC to be -0.5 W.m-2 +/- 0.4 W.m-2 (that's +/- 80%!).

    I'm afraid it's back to the precautionary principle for you Andrew.

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  3. John McLean

    logged in via email @connexus.net.au

    This statement by Glikson lacks any credible supporting evidence that CO2 causes warming that is significant and dangerous enough to warrant any action whatsoever.

    Further, investigations using the well-recognised MODTRANS modelling tool indicate that a doubling of CO2 will cause just under 1 degree of warming without constraint on the relative humidity and about 0.1 degrees if relative humidity is constrained.

    The absence of warming (or negiligible warming, depending who one speaks to) over the last 10 years is easily explained, as was the absence from 1945 to 1977 - the ENSO was well towards El Nino conditions for most of that time. The Southern Oscillation Index tracks very well with temperatures 7 months ahead, as it has done for the last 50 years except when volcanic activity caused cooling.

    The ENSO hypothesis has been validated by observations; the CO2-driven temperature hypothesis has not.

    I'm puzzled why Glikson persists with a hypothesis that has proved false.

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  4. Andrew Glikson

    Earth and paleo-climate scientist at Australian National University

    Response to comments:

    The 3 comments above do not appear to be based on the peer review literature nor on recent reports by NOAA, NASA, NSIDC, Hadley-Met, Tyndall, Potsdam Climate Impacts, CSIRO, BOM, the world’s academies of Science, IPCC -, the list goes on.

    An up-to-date report by NOAA "State of the Climate in 2010"
    http://www.ncdc.noaa.gov/bams-state-of-the-climate/2010.php
    presents comprehensive global and regional accounts of global and regional climate states and trends, providing answers…

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    1. Marc Hendrickx

      Geologist

      In reply to Andrew Glikson

      Andrew you totally miss the point and misrepresent the IPCC in the process. You rely heavily on the cooling effect of aerosols to help explain the poor performance of climate models to account for the lack of warming. The IPCC state the following in regard to the level of scientific understanding for aerosols. The level of scientific understanding of the direct effect is considered "medium to low" and for the indirect effect the level of scientific understanding is considered to be "LOW".

      Your continued denial and misrepresentation of the facts regarding the level of scientific understanding of important aspects of climate science makes a mockery of the scientific method and the aims of this website.

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    2. Nathan Stewart

      Mr

      In reply to Andrew Glikson

      Thankyou Andrew. Ive yet to see an agurment from deniers or doubters that havent been robustly put down which continues to make my confidence in AGW theory grow, which is sad because i wish it werent so.

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    3. Marc Hendrickx

      Geologist

      In reply to Nathan Stewart

      Andrew bases his argument on a climate forcing with an error of 80% and your confidence grows. I don't whether to laugh or cry.

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    4. Nathan Stewart

      Mr

      In reply to Marc Hendrickx

      where exactly in AR4 does it say that? I know enough now to be sceptical of any sceptic's statements.

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    5. Nathan Stewart

      Mr

      In reply to Marc Hendrickx

      Ok, not going to tango with you on this one. Im not a geologist (although i am beginning to find geology immensely interesting).

      I certainly wont claim to be unbiased, so from my lay person pov - my response to you would be to say that 4 years is a long time in science, and that we now have a better understanding of aerosol radiative forcing as Andrew's links suggest. We certainly wouldnt have any less of an understanding of it.

      In any regard, there is no doubt that sulphur has some effect on global cooling, we can cross our fingers that it is on the lower side rather than the higher side, but that is not what recent research is suggesting according to the new Hansen et al study.

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    6. Marc Hendrickx

      Geologist

      In reply to Nathan Stewart

      Gavin, If you read Hansen's paper you'll find there has been no improvement in understanding aerosols since the IPCC AR4 report.This is one area deserving of further research. It is wrong on Andrew's part to mislead in this manner.

      eg...
      "But the large uncertainty in the aerosol forcing implies that the net forcing is very uncertain, so uncertain that either value suggested by Hansen's grandchildren for the net forcing could be correct."

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    7. James Szabadics

      BSc

      In reply to Andrew Glikson

      Andrew, Maue work is peer reviewed.

      Maue, R. (2011),
      Recent historically low global tropical cyclone activity,
      Geophys. Res. Lett., doi:10.1029/2011GL047711, in press.
      [PDF] (accepted 7 June 2011)

      http://www.agu.org/contents/journals/ViewPapersInPress.do?journalCode=GL

      Also my apologies, I had the wrong end of the stick with sea ice when you were talking about accelerated ice loss. I would contend that 3.2mm/yr is not "accelerated" sea level rise however compared to the long term trend. See long term trend here with decellerating sea level rise in the tail of the graph at the 2005 to 2011 end:

      http://sealevel.colorado.edu/files/current/sl_ib_global.jpg

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    8. James Szabadics

      BSc

      In reply to Marc Hendrickx

      What i dont fully understand is what has changed with man made Aerosols around 2000? Has the ratio of aerosols to CO2 changed? Why would man made aerosols have little effect prior to 1998 and a dramatic effect afterwards?

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  5. Andrew Glikson

    Earth and paleo-climate scientist at Australian National University

    Regarding the comment above "You rely heavily on the cooling effect of aerosols to help explain the poor performance of climate models to account for the lack no warming."

    Lack of warming?

    The figure in my article shows warming of the polar regions to above 4 degrees C , which is what drives melting of the continental ice sheets reported from satellite gravity measurements (Rignot and Velicogna 2011).

    Regarding the aerosol effect, the IPCC AR4 2007 indicates the following in figure SPM2:
    CO2…

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    1. Marc Hendrickx

      Geologist

      In reply to Nathan Stewart

      You'll note Gavin that Andrew in his approach to science avoids the issue of uncertainty. I wouldn't be hanging our future on a "guess". If you take the time to compare model predictions made by Hansen in the 1980s with what has eventuated you will see that we are currently tracking at or below the lowest range of Hansen's predictions. Andrew relies on a select few articles to make the case for urgent action without providing all the necessary detail. If you are interested in more detail I recommend Judy Curry's site, http://judithcurry.com/, you won't get the full story from Andrew Glikson.

      As Feynman said "If you thought that science was certain - well, that is just an error on your part."

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    2. Nathan Stewart

      Mr

      In reply to Marc Hendrickx

      If you are trying to suggest there is nothing urgent about global warming than there is not much point me continuing this conversation. Im sure you'll note the the Level of scientific understanding of the radiative forcing of long lived greenhouse gasses is high.

      Judith Curry doesnt impress me much. Seems like a bit of attention seeking to me. People can doubt science all they like, but anyone who thinks that any bit of uncertainty in their own mind is reason enough not to do anything about global warming and ocean acidification is just plain wrong.

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    3. James Szabadics

      BSc

      In reply to Andrew Glikson

      Andrew, could you please explain what is meant by "near term" and "acceleration" in this context?

      Do you mean that over the next 10 years sea level rise will be > 3.1mm/yr long term trend? If the proponents of GCR aerosols are right we should expect deceleration of sea level rise, and if similar cooling occurs as in the Maunder and Dalton minimums perhaps even european glacial advancement.... This will be something we get to observe which is quite exciting.

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  6. Andrew Glikson

    Earth and paleo-climate scientist at Australian National University

    No one expects the "all the necessary detail" to appear in an internet article or on a thread - the best that can be done for those who are interested in what the peer-reviewed science says is to point out the latest comprehensive reports and reviews, including the lists of references they contain.

    In this case, the latest report, based on the most up to date peer reviewed literature, is Professor Will Steffen's report "The Critical Decade" and the references therein.
    http://climatecommission.gov.au/topics/the-critical-decade/

    I will be pleased to clarify technical points in this report if required.

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  7. Andrew Glikson

    Earth and paleo-climate scientist at Australian National University

    James,

    You write: "Andrew, could you please explain what is meant by "near term" and "acceleration" in this context? Do you mean that over the next 10 years sea level rise will be > 3.1mm/yr long term trend? If the proponents of GCR aerosols are right we should expect deceleration of sea level rise, and if similar cooling occurs as in the Maunder and Dalton minimums perhaps even european glacial advancement.... This will be something we get to observe which is quite exciting.

    Response:

    1. Sea…

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    1. Nathan Stewart

      Mr

      In reply to Andrew Glikson

      Thanks again Andrew, i find your responses and those of other respected scientists who have taken the time to write these articles and answer questions highly informative. Ive gone from thinking that the scientists are probably right because they are smart and almost all saying the same thing, to being as sure as i could ever be as all the arguments seem very solidly based on real science and stand up to all the sceptical comments that are getting thrown at them.

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    2. James Szabadics

      BSc

      In reply to Andrew Glikson

      Andrew,

      Thanks for the response.

      RE 1) its pretty clear that year to year sea level fluctuates. You cite one year (2006) to claim 3.5mm/yr sea level rise. Now it is 2011 - are you aware of what sea level has done since 2006? Overall you would be brave to claim that sea level rise has deviated from 3.1mm/yr trend in the modern record. In the last 5 years it appears to be decellerating to around 2.5mm/yr but its only a 5 year run so we wait and see. It is not accelerating beyond the trend…

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    3. James Szabadics

      BSc

      In reply to James Szabadics

      Further to above for those interested in investigating for themselves - the sea level data is here:

      http://sealevel.colorado.edu/files/current/sl_ib_ns_global.txt

      Plot trends for yourself...

      Slope of first data point in 2002 to last data point in 2010 (the main article specifically references these dates) shows rate of chage of 2.31mm/yr. In the main article the claim is that this shows accelerated ice melt compared to the 3.1mm/yr trend when in fact it shows decelleration.

      From 1993 to 2002 the rate of change shown in the data is 3.336 mm/yr, from 2002 to 2010 the rate slows to 2.31mm/yr. Perhaps Andrew would like to ammend the article to say that the overall rate of ice loss from Greenland and antarctica and all combined glaciers has decellerated?

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    4. James Szabadics

      BSc

      In reply to Andrew Glikson

      I also think regarding aerosols if you could explain what happened to the rate of human aerosol production from 1975 to the late 90s, surely we made a lot less aerosols but more CO2 for the steep temperature climb, then we started making more aerosols per unit CO2 again since 2000 perhaps? What is the aerosol story vs CO2 emissions because it seems to change balance if you are correct?

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    5. James Szabadics

      BSc

      In reply to James Szabadics

      For a slightly longer term view of sea level variation for the interested scientist I suggest reviewing the data here:

      http://www.psmsl.org/products/reconstructions/gslJC2006.txt

      This is the data covering from the Dalton Solar minimum to the early 21st century.

      You can see in this reconstruction a number of periods of 20 years+ (for example from 1928 to 1952) where we saw similar rates of change to the late 20th century. You can also see multiple decellerations.

      It would appear that sea level…

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  8. Marc Hendrickx

    Geologist

    Here's Judy Curry's take on the sulphur claims following publication of a PNAS paper that recognizes there has been NO warming since 1998.

    The paper is "Reconciling anthropogenic climate change with observed temperature 1998-2008."

    The first line of the Abstract reads..."Given the widely noted increase in the warming effects of rising greenhouse gas concentrations, it has been unclear why global surface temperatures did not rise between 1998 and 2008."

    Judy Curry comments...
    "This paper points…

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    1. Felix MacNeill

      Environmental Manager

      In reply to Marc Hendrickx

      Yet again, the only voices raised against the evidence are a tiny, but indefatigable band of inderscribables who believe that the plural of nonsense is evidence.
      Andrew deserves some kind of award for sheer patience but, sadly, it's completely pointless as nobody ever actually responds to the evidence he provides.
      As with all the other recent material published here, the obsessive, empty repetitions of Douglas Cotton, John MacLean, Marc Hendrickx and James Szabadics have provifed the most compelling evidence I've ever seen of the utter emptiness of the arguments against the science.
      Keep digging guys - the most enthusiastic example of digging one's own grave that I've ever witnessed.

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    2. James Szabadics

      BSc

      In reply to Felix MacNeill

      Felix,

      I appreciate your immense contribution to the growth of readers understanding and scientific knowledge with this comment. Sadly, with it you show where the debate sometimes heads away from interesting science and the search for better understanding to simple emotion. I dont mind if you or Andrew point out errors in my thinking or comments or question my conclusions, I'm OK with admitting when I get it wrong. We are all human!

      Don't be afraid to ask questions is what I always tell people and if you make a mistake put your hand up and admit it. I hope you can also read my responses to Andrew's comments and think about what it means. I have asked Andrew questions to better understand some of the claims and also challenged some of his claims on the basis of available data and provided you with the links to that data so you can challenge me too. This is healthy debate.

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