Billion tons CO2 = how many °C?

I’m sick of all these claims that we should, or even can, limit the world’s warming to 2 °C.

Here’s a challenge: name a scientist prepared to make this assertion and describe the evidence for it.

It appears to be no more “settled science” than an unsubstantiated urban myth. At the very least, there’s so much uncertainty about the climate sensitivity to warming that we don’t know the effect on temperature of, say, 5 billion tonnes of CO2.

Ignoring for a moment the obvious question of what’s so wrong with two degrees, how do “scientists” reason their way from 2 degrees of warming to (as it says below) 44 billion tons of CO2 in 2020?

If that reasoning can be falsified, it means the claim we can limit warming is good only to justify reducing our emissions.

The latest story to trigger my annoyance about this is a report from Reuters covering a report from the UN Environment Programme (UNEP). I’ve highlighted the parts which refer to (unspecified) scientific authority.

Greenhouse gas emissions in 2020 could rise more than forecast to between 6 billion and 11 billion tons above what is needed to limit global warming to 2 degrees Celsius, a UNEP report showed on Wednesday.

The gap between countries’ emissions cut pledges and what is needed to remain under what scientists say is the limit to avoid devastating effects of global warming has widened since its 2010 estimate of 5-9 billion tons as new data emerged, UNEP said.

Extreme weather is likely to worsen across the globe this century as the Earth’s climate warms, U.N. scientists warned last week, but global carbon emissions rose to a record level last year.

To stay within the 2 degree limit, global emissions will have to peak soon (and) total greenhouse gas emissions in 2050 must be about 46 percent lower than their 1990 level, or about 53 percent lower than their 2005 level,” the report said.

Countries agreed last year in Cancun, Mexico, that deep emissions cuts were needed to hold an increase in global average temperature below 2 degrees Celsius above pre-industrial levels.

Delegates from nearly 200 countries will meet in South Africa next week for a U.N. summit but only modest steps toward a broader climate deal are seen likely.

A 2 degrees C limit is only possible if emission levels are kept to around 44 billion tons of carbon dioxide equivalent in 2020. If nothing is done to limit emissions, they could rise to around 56 billion tons in 2020, UNEP said.

We already have the strongest indication that there is no good scientific reasoning between the two degrees and the 44 billion tons of CO2: the obvious fact that, although global CO2 emissions increased by 45% between 1990 and 2010, the global temperature anomaly in June 1990 was identical to the anomaly in June 2011.

In 20 years, the extra carbon dioxide hasn’t made the temperature rise. That’s evidence.

12 Thoughts on “Billion tons CO2 = how many °C?

  1. Australis on November 25, 2011 at 10:39 am said:

    The degree of correlation between emission tonnages and atmospheric concentration, along with correlation between the latter and the global average temperature anomaly, were expressed in an algorithm by Christopher Monckton during 2009.

    The subject is discussed broadly in Lord Monckton’s recent paper “Empirical Determination of Climate Sensitivity” at

    Specifically, in his January 2010 letter to Australian PM Kevin Rudd, Monckton described the formula:

    “We derive the necessary implicit function from the IPCC’s statement to the effect that equilibrium surface warming delta-T at CO2 doubling will be (3.26 ± ln 2) C°. Since the IPCC, in compliance with Beer’s Law, defines the radiative forcing effect of CO2 as logarithmic rather than linear, our implicit function can be derived at once. The coefficient is the predicted warming at CO2 doubling divided by the logarithm of 2, and the term (C/C0) is the proportionate increase in CO2 concentration.”

    He obtains much lower consequential warming figures than “some scientists”.

  2. Australis on November 25, 2011 at 11:20 am said:

    This thread turns out to be very timely. “The Australian” today reports on a new peer-reviewed paper in “Science” Journal, which finds that the carbon sensitivity figures used by the IPCC are seriously over-stated.

    “Professor Schmittner said taking his results literally, the IPCC’s average or “expected” value of a 3C average temperature increase for a doubling of CO2 ought to be regarded as an upper limit.”

    So, the worst case is a temperature of 3C above 1750 levels if and when atmospheric CO2 reaches 560ppm. We’ve already experienced about 1C, so the apocalypse version is that future warming could possibly get twice as bad as we experienced during the last few decades.

    I could live with that.

  3. Richard C (NZ) on November 25, 2011 at 11:27 am said:

    Re “what scientists say”, the UNEP report obviously predates this latest development:-

    Climate forecasts ‘exaggerated’: Science journal

    In 2007, the UN’s peak climate body, the Intergovernmental Panel on Climate Change, warned that a doubling of CO2 from pre-industrial levels would warm the Earth’s surface by an average of 2C to 4.5C, although some studies have claimed the impact could be 10C or higher.

    Professor Schmittner said it had been very difficult to rule out these extreme “high-sensitivity” scenarios, which were very important for understanding risks associated with climate change.

    The study found high-sensitivity models led to a “runaway effect” under which the Earth would have been covered in ice during the last glacial maximum, about 20,000 years ago, when CO2 levels were much lower.

    “Clearly that didn’t happen, and that’s why we are pretty confident that these high climate sensitivities can be ruled out,” he said.

    Professor Schmittner said taking his results literally, the IPCC’s average or “expected” value of a 3C average temperature increase for a doubling of CO2 ought to be regarded as an upper limit.

    Oops, just seen Australis was already on this ball

  4. Richard Treadgold, see how quickly the conversation degenerates when you try to focus someone’s attention on critical data, particularly on the subject of CO2 climate sensitivity? The very first commenter, Australis, simply ignored your point, given in your last two sentences, and gives you back a quite irrelevant homage to Christopher Monckton, which doesn’t even reflect Monckton’s actual belief in the value to be given the CO2 climate sensitivity–he is a “lukewarmist”, and believes the true value to be about 1°C per doubling of CO2, not 3°C per doubling. And he is wrong at that–there is NO greenhouse effect at all:

    By the way, I have been trying for months to get people’s attention of the fact that the 2011 global and sea surface temperature (SST) anomalies are closely tracking the 1991 anomalies, basically the same point you are making here (although my observation covers rather a whole year, 1991, not just one month, and both global mean and SST anomalies). Your article here is the first indication I have seen that anyone else has noticed we are back to the temperatures of 20 years ago (and that should be “20 years” in your last sentence, of course).

    People’s beliefs are all over the map, too often due to who they take for their hero or “expert” (Australis obviously believes in Monckton). Respect is hard to come by, and those who get it now are, generally, not those most deserving of it.

  5. Mike Jowsey on November 25, 2011 at 12:58 pm said:

    I don’t see a degeneration of the conversation – rather, an augmentation. Australis was building upon the point given in the last few sentences. No need to get on your high horse mate.

    As for your second paragraph – thanks, good point on the 20 year thing.

    Then you get back on your horse in para 3. Stop huffing Mr Huffman.

  6. Thanks. People who keep track of references, as you do, are worth much.

  7. You could live with that? So could I.

  8. I find it hard to credit that high sensitivity might lead to colder temperatures. Talk about anti-intuitive!

  9. bulaman on November 25, 2011 at 2:46 pm said:

    And now we follow the Euro carbon market into the toilet.. how low will it go next week??!!

  10. Yes, well, Mike has already waded in dependably in defence of Australis, but let me add that you push too hard one way in interpreting his comments — he doesn’t mean to contradict me on this occasion, just to augment it, as Mike suggests.

    I hadn’t noticed the SST anomalies, thanks (and for the typo tip, too!). Do you have any indication of cycles that might be coinciding to cause this? Or is it more likely to be some random effect of natural variation?

  11. Harry Dale Huffman’s thesis is that there is no greenhouse effect at all.
    I can’t see how we can dismiss this unless there has been an unambiguous rebuttal.

    Mr (Dr?) Huffman bases his theory by comparing the atmosphere of Venus with that of Earth. We should note that James Hansen studied the atmosphere of Venus during his PhD thesis.

    I am fascinated that two educated men can study the same objects and come to completely different conclusions.

  12. Clarence on November 26, 2011 at 2:31 pm said:

    H D Huffman raises a very interesting suggestion – that 2011 is tracking the GATA of 1991.

    If we are now at the same levels as 20 years ago (and SREX suggests little change for the next 30 years) how can it be argued that there is any URGENCY in this whole climate change debate?

    Where may these comparisons be seen? Do they apply to HadCRUT land measures or to the satellite readings at UAH?

Leave a Reply

Your email address will not be published. Required fields are marked *

Post Navigation