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Carbon dioxide’s effect on global warming ‘understimated’

The sensitivity of the Earth system to a doubling of atmospheric carbon dioxide may be twice as great as scientists had thought

(Pic: Flickr/Karindalziel)

(Pic: Flickr/Karindalziel)

By Alex Kirby

You may think the prospect of climate change is alarming, a call to action to slow down our emissions of carbon dioxide and other greenhouse gases.

You’re almost certainly right. But some scientists are now suggesting you should be much more concerned than you are, because they think we may be seriously underestimating the problem.

The Geological Society of London (GSL) says the sensitivity of the Earth’s climate to CO2 could be double earlier estimates.

The Society has published an addition to a report by a GSL working party in 2010, which was entitled Climate change: Evidence from the Geological Record.

The addition says many climate models typically look at short term, rapid factors when calculating the Earth’s climate sensitivity, which is defined as the average global temperature increase brought about by a doubling of CO2  in the atmosphere.

Scientists agree that a doubling of atmospheric CO2 levels could result in temperature increases of between 1.5 and 4.5°C, caused by rapid changes such as snow and ice melt, and the behaviour of clouds and water vapour.

But what the GSL now says is that geological evidence from palaeoclimatology (studies of past climate change) suggests that if longer-term factors are taken into account, such as the decay of large ice sheets, the Earth’s sensitivity to a doubling of CO2 could itself be double that predicted by most climate models.

CO2′s significance

Dr Colin Summerhayes, who led the statement’s working group, says: “The climate sensitivity suggested by modern climate models may be fine for the short term, but does not encompass the full range of change expected in the long term…”

But he cautions that there are really two “sensitivities” involved: “Climate sensitivity is what happens in the short term in response to a doubling of CO2. But the Earth system sensitivity is what happens in the longer time frame as ice sheets slowly melt, and as sea level slowly rises.

“…The IPCC focuses on… the climate sensitivity – what will happen in the next 100 years. Earth system sensitivity tells you what happens in the next couple of hundred years after that.”

The GSL’s addition also reports new data showing that temperature and CO2 levels recorded in Antarctic ice cores increase at the same time. This, says Summerhayes, “makes the role of CO2 in changing Ice Age climate highly significant.”

Atmospheric carbon levels are currently just below 400 parts per million (ppm) – a figure last seen  between 5.3 and 2.6 million years ago. Global temperatures were then 2-3°C higher than today, and sea levels were several metres higher, due to partial melting of the Antarctic ice sheet.

If the current rate of increase (2 ppm per year) continues, CO2 levels could reach 600 ppm by the end of this century; levels which, says Summerhayes, “have not been seen for 24 million years”.

Models match palaeoclimate

The new GSL statement outlines evidence that a relatively modest rise in atmospheric CO2 levels and temperature leads to significant sea level rise, with oceans more acidic and less oxygenated. Previous such events caused marine crises and extinctions, with the Earth system taking around 100,000 years to recover.

Dr Summerhayes said: “We now have even more confidence from the geological record that the only plausible explanation for current warming is the unprecedented exponential rise in CO2 and other greenhouse gases.

“Recent compilations of past climate data, along with astronomical calculations, show that changes in the Earth’s orbit and axis cooled the world over the past 10,000 years. This cooling would normally be expected to continue for at least another 1,000 years.

“And yet Arctic palaeoclimate records show that the period 1950-2000 was the warmest 50 year interval for 2,000 years. We should be cool, but we’re not.”

He told Climate News Network: “The main implication from my perspective is that the geological record tells us that increasing CO2 increases temperature, melts ice, and raises sea level. This we know independently of any fancy numerical model run by climate scientists.

“However, those climate scientists’ models happen to come up with about the same answer as we get from the geological record, which suggests that the modellers  are likely to be on the right track.”

This article was produced by the Climate News Network

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  • Joe F

    nice spelling! LMAO

  • timg56

    It continues to amaze me that such intelligent, well educated individuals can go on about water vapor when they haven’t a clue about clouds.
    Basic physics allows us to calculate the expected impact of a doubling of CO2 in isolation from all other factors of our dynamic climate system. ~1.1 C. To reach the higher numbers of 3 – 4.5 C, GCM’s (climate models) add a x 3 factor from water vapor. They just plug the number in, without really knowing how water vapor acts. The clearest example of that are clouds, which are ….? (Water vapor is the answer we are looking for.) Clouds effect the climate system in a number of ways, providing both positive and negative feedback. Climate scientists cannot tell you whether or not the cumulative effect is positive or negative – i.e. do they act in a way that causes an exceleration of an input (positive feedback) or do they have a damping effect (negative feedback). The models assume it is positive. Which perhaps may explain why their output and real temperature data are diverging.

  • mjonesx

    Thank you, this is an important study

  • GeraldWilhite

    As an upfront disclaimer, let me say that I am not a scientist and I have no financial interest at all in fossil fuels. I’m just an ordinary citizen with a very keen life long interest in science.

    You say “We should be cool, but we’re not.” — I submit this critique because I think you may be very, very wrong. I see the 17 year pause (which you totally ignore) as a probable temperature plateau signaling the start of a cooling period.

    My layman’s understanding is that over 17 years without surface global warming has high statistical significance that is so high that another two years of it will unquestionably falsify the AGW theory I see AGW as very narrow and antiquated theory. When UN’s WMO imposed it the IPCC twenty years ago, it severely crippled the investment payback we should have received from two decades of multi-billion dollar investment in IPCC driven climate science. (By the way, I am totally perplexed by your opinion that IPCC modelers are on the right track.)

    I’m even more perplexed by your failure to recognize or even mention the 17 year pause, which I mentioned before. The pause could very well be the end the warming trend we’ve been enjoying since about 1650 at the depths of the Little Ice Age. IMHO, the current period of low solar activity is the strongest suspect for the cause of the 17 year pause. My speculation stems from the opinions I read about from solar scientists. They seem to be very persuaded that pause is start of a long cooling trend, perhaps even the start of Little Ice Age II.

    Hopefully their expected cooling period won’t last long. Despite the ups and downs of the Holocene climate, the general warming trend of this interglacial period has the root of our prosperity. Even so, I fear that humanity will take a severe beating from a long cooling spell.

    I’m sorry that the link to the paper didn’t work for me. I have to ask if your work considers the concepts behind recent work of Professor Murray. It has been widely discussed because of pre-publication informal lectures on his concepts on the internet. I didn’t see any recognition of it in the article. His ideas and logic seem to be very persuasive to many climate scientists, perhaps game-changers that cannot be ignored. We’ll soon see. His full paper will be published in a few weeks. .

    Also, I didn’t see any reflection in your article of the mind-blowing work of the Netherland’s Henrik Svensmark, It is now generally agreed that cloud formation is the key regulator of global surface temperatures. Svensmark theorizes that much cloud development is the result of higher quantities of interstellar cosmic rays penetrating Earth’s weaker magnetic shielding as the Sun’s emissions grow weaker. In his thinking, as I understand it, CO2′s influence plays a minor supporting role relative to H2O and aerosols.

    Finally I don’t see recognition paid to the well established evidence that CO2 kept rising steadily during the 17 year period of the global warming pause. To me this suggests that Salby and Svensmark are right in their conclusion that temperature drives CO2, not the other way around,

    Isn’t that what the geologic record and the ice cores evidence indicates?

    • MorinMoss

      “My layman’s understanding is that over 17 years without surface global warming has high statistical significance”

      Your understanding is wrong for several reasons.

      It has NOT been “17 years without surface global warming” – see link below. The correct thing to say is that’s the amount of warming seen in that time – and there has been some – is not statistically significant at the 95% confidence level.

      This is typical for a short trend.

      Check this from someone who does understand statistics very well.


      As you can see, “no warming” is more than just a stretch of the truth.

      There’s more – one of the problems with that “17 years, no surface warming” is that temperature monitoring coverage of the Arctic is quite poor. Yet, in that time, we have seen some of the most dramatic declines in sea ice extent, area & volume in more than a century.

      It takes a shocking amount of heat to melt ice – in fact, the amount required to just melt a given quantity of ice into 0°C water would raise that quantity of water from room temp to just below boiling!!

      All that energy is essentially missing from surface temp measurements and there has been a dramatic decline in global ice coverage.

      Furthermore, the ENSO cycle has been trending in favor of La Nina events for quite some time yet have had only a minimal impact on the global temp average.

      This was not the case prior to the mid-70s.


      The only year prior to the 21st century that’s in the top 10 hottest globally is 1998, due to the strongest El Nino in over a hundred years.

      That standout year, a mere decade later, is our new normal.

      And Svensmark? While clouds are an important and not fully understood mechanism, the “cosmic ray” speculation is just that – speculation.


  • Will

    This is wrong I don’t get it

  • libtard science

    Gosh, which is it RTCC? IPCC’s last report admitted that man-made CO2 is not the driver of global warming they’ve been saying it was. Poor wingnuts just can’t make up their minds.. or could it be that they want to have it both ways.

  • MorinMoss

    From what I’ve read, most of the soot that ends up in the Arctic does NOT originate from China but I’m sure their coal-burning plays a role in glacier melt in other regions.

    That said, the enormous amount of aerosols from all that coal (they burn as much each year as the entire world, incl themselves, did 25 years ago) is also having a significant cooling effect.

    If China adheres to the plan to have ALL coal plants conform to emission standards that are as stringent as America’s by Fall 2014, we could have another record warm year, even without an El Nino, very soon.

  • MorinMoss

    “Global sea ice area recovered from the end of 2012 until now to be back to what it was in mid 1980′s”

    Global? Got a citation?

    The ARCTIC is undergoing a dramatic decline in ice coverage while the ANTarctic is seen some increase ( as was predicted).

    This does not “balance” out the Arctic loss as some would think and then there’s the increasing loss of land ice from Greenland.

    “And your typical subterfuge about hottest ~decade.. WHO said it was not?”

    Quite a few deniers including one very popular bug-eyed British peer.

    “Game OVER – you LOST!”
    Last time I heard that was from a 5 yr old.
    He grew up; you should too.

    • Danceswithdachshunds

      I posted the link to the “Global Sea Ice Area 1979 – Present” from the Arctic Climate Research at the University of Illinois but — RTCC is holding it for moderation so …

      Google: global sea ice area cryosphere today

      Click on link for “Polar Sea Ice Cap and Snow – Cryosphere Today”

      Search that page for the word global then click on the thumbnail. It’s been over a YEAR sitting at about the average sea ice extent from 1979 to ~now.

      Obviously decreasing CO2 cannot explain the rapid NATURAL rebound of 2 to 3 million km^2 of sea ice area that has occurred at any other time on that chart, (like beginning at the end of 2007, end of 2008 and end of 2010) but, unlike those, this most recent one beginning late in 2012 has endured for over a year and counting.

      As for your lame assertion “This does not “balance” out the Arctic loss” – yes it does; sea ice is sea ice and it does NOT form in warm water.

      It has to be a game to people like you because you refuse to believe
      the data. There is simply NO “catastrophic warming” going on with our
      climate and this chart disproves your assertion that earth is losing polar sea ice.

      The current melt rate of Greenland will have it ice free in about 15,000 years – let’s talk then okay?

    • Danceswithdachshunds

      Everything I try to to type to refute you is being censored by RTCC, the only way they can keep the hoax going

      • RealOldOne2

        “Everything I try to type to refute you [MorinMoss] is being censored by RTCC”
        Mine too. I linked the global sea ice chart from Cryosphere today also. It was censored.

        I also quoted from James Hansen back in the 1980s to expose MorinMoss’s erroneous claim that they predicted that Antarctic sea ice would increase. That was censored too.

        Every comment is held in moderation. It’s pathetic how they censor factual comments.

    • Danceswithdachshunds


    • RealOldOne2

      Danceswithdaschshunds already pointed you to CryosphereToday global sea ice chart, so I won’t repeat that link that got censored.

      But I will re-post the evidence that rebuts your erroneous statement about Antarctic ice, that “ANTarctic is seen some increase (as was predicted)”.

      In the 1980s, the global warming alarmists predicted that both poles would warm an sea ice would decrease:
      “The maximum warming during West Antarctica is associated with the largest reduction in sea ice cover there.” – Hansen, Lacis, Rind, Russell in ‘Climate Sensitivity to Increasing Greenhouse Gases’.

      Since my comment with the link got censored, just google the title to see the evidence yourself.

  • Danceswithdachshunds

    Why am I being denied the chance to post a reply to MorinMoss ??

  • Science Officer

    The Vikings raised crops in Greenland, the Romans cultivated vineyards in Britain. Conditions which would suggest warmer climates have existed within historical times than we are observing today. All with lower CO2 concentrations and without widespread sea level flooding caused by melting ice caps. Our ancestors must have been a lot smarter than we give them credit for. They some how managed to thrive under conditions we think are going to cause the end of civilization.

  • Steve Morton

    Still waiting for a study about causation not just corrolation. Thought this might be one, but still just theories.