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CO2 equivalents

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There was a minor kerfuffle in recent days over claims by Tim Flannery (author of “The Weather Makers”) that new information from the upcoming IPCC synthesis report will show that we have reached 455 ppmv CO2_equivalent 10 years ahead of schedule, with predictable implications. This is confused and incorrect, but the definitions of CO2_e, why one would use it and what the relevant level is, are all highly uncertain in many peoples’ minds. So here is a quick rundown.

Definition: The CO2_equivalent level is the amount of CO2 that would be required to give the same global mean radiative forcing as the sum of a basket of other forcings. This is a way to include the effects of CH4 and N2O etc. in a simple way, particularly for people doing future impacts or cost-benefit analysis. The equivalent amount is calculated using the IPCC formula for CO2 forcing:

Total Forcing = 5.35 log(CO2_e/CO2_orig)

where CO2_orig is the 1750 concentration (278 ppmv).

Usage: There are two main ways it is used. Firstly, it is often used to group together all the forcings from the Kyoto greenhouse gases (CO2, CH4, N2O and CFCs), and secondly to group together all forcings (including ozone, sulphate aerosols, black carbon etc.). The first is simply a convenience, but the second is what matters to the planet. Many stabilisation scenarios, such as are being discussed in UNFCCC negotiations are based on stabilising total CO2_e at 450, 550 or 750 ppmv.

Magnitude The values of CO2_e (Kyoto) and CO2_e (Total) can be calculated from Figure 2.21 and Table 2.12 in the IPCC WG1 Chapter 2. The forcing for CO2, CH4 (including indirect effects), N2O and CFCs is 1.66+0.48+0.07+0.16+0.34=2.71 W/m2 (with around 0.3 W/m2 uncertainty). Using the formula above, that gives CO2_e (Kyoto) = 460 ppmv. However, including all the forcings (some of which are negative), you get a net forcing of around 1.6 W/m2, and a CO2_e (Total) of 375 ppmv with quite a wide error bar. This is, coincidently, close to the actual CO2 level.

Implications The important number is CO2_e (Total) which is around 375 ppmv. Stabilisation scenarios of 450 ppmv or 550 ppmv are therefore still within reach. Claims that we have passed the first target are simply incorrect, however, that is not to say they are easily achievable. It is even more of a stretch to state that we have all of a sudden gone past the ‘dangerous’ level. It is still not clear what that level is, but if you take a conventional 450 ppmv CO2_e value (which will lead to a net equilibrium warming of ~ 2 deg C above pre-industrial levels), we are still a number of years from that, and we have (probably) not yet committed ourselves to reaching it.

Finally, the IPCC synthesis report is simply a concise summary of the three separate reports that have already come out. It therefore can’t be significantly different from what is already available. But this is another example where people are quoting from draft reports that they have neither properly read nor understood and for which better informed opinion is not immediately available. I wish journalists and editors would resist the temptation to jump on leaks like this (though I know it’s hard). The situation is confusing enough without adding to it unintentionally.

Oregon Institute of Science and Malarkey

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A large number of US scientists (to our direct knowledge: engineers, biologists, computer scientists and geologists) received a package in the mail this week. The package consists of a colour preprint of a ‘new’ article by Robinson, Robinson and Soon and an exhortation to sign a petition demanding that the US not sign the Kyoto Protocol. If you get a feeling of deja vu, it is because this comes from our old friends, the Oregon Institute of Science and Medicine and is an attempt to re-invigorate the highly criticised 1999 “Oregon Petition“.

The article itself is just an update of the original article, minus an author (Baliunas), with a switch of Robinson children (Zachary’s out, Noah is in), but with a large number of similar errors and language. As in previous case, this paper too, is not peer reviewed.

Since this is a rehash of the previous paper plus a few more cherry-picked statistics of dubious relevance, instead of tediously going through the whole thing ourselves, we are going to try something new – an open source debunking.
[Read more…] about Oregon Institute of Science and Malarkey

My model, used for deception

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Well, not my model exactly. I developed and host a web interface to the modtran model of atmospheric infrared radiation, an early example of a line-by-line code which I downloaded and use to teach and as part of a textbook. Now David C. Archibald from Summa Development Limited, Perth, WA, Australia claims that my “University of Chicago modtran facility” proves that global warming won’t happen. [Read more…] about My model, used for deception

Cosmic rays don’t die so easily

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Cover picture of Solar Activity and Earth's Climate Last week, a Norwegian official-looking – and in my view – climatesceptic website praised Eigil Friis-Christensen from the Danish space center (featuring in the Great Global Warming Swindle) and hailed him for having given the best speech ever in the annual Birkeland seminar organized by Norwegian Academy of Science and Letters (NASL). There were rumours of controversy behind the scene before the seminar, as the NASL is regarded as a prestigious body in Norway.

Furthermore, Svensmark and Friis-Christensen have written a response (title ‘Reply to Lockwood and Fröhlich – The persistent role of the Sun in climate forcing’; DNSC Scientific Report Series 3/2007) to a recent paper by Lockwood and Frohlich (LF2007). In this response, they state ’… [LF2007] argue that this historical link between the Sun and climate came to an end about 20 years ago‘. Another quote from their response is ‘Here we rebut their argument comprehensively’. So the cosmic ray theory isn’t quite dead after all?

[Read more…] about Cosmic rays don’t die so easily

Uncertainty in polar ozone depletion?

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Guest commentary by Drew Shindell

The unique chemistry that causes dramatic ozone depletion in the polar springtime lower stratosphere has been studied intensely for the past 2-3 decades and much that was speculated about 30 years ago when the problem first emerged has been verified and made more coherent. However, a new report concerning laboratory measurements of a key molecule involved in this chemistry have raised questions about current understanding. The results (Pope et al., J. Phys. Chem., 2007) suggest a reduced ability for sunlight to break apart the chlorine monoxide dimer (Cl2O2) and have already led to a great deal of debate about their implications. I’ll try here to help assess what these new measurements really mean.
[Read more…] about Uncertainty in polar ozone depletion?

Perspectives from China

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I spent the last three weeks in China partly for a conference, partly for a vacation, and partly for a rest. In catching up over the last couple of days, I notice that the break has given me a slightly different perspective on a couple of issues that are relevant here.

First off, the conference I attended was on paleoceanography and there were was a lot of great new science presented, particularly concerning the Paleocene-Eocene Thermal Maximum (around 55 million years ago), and on past changes to tropical rainfall patterns (see this week’s Nature) – two issues where there is a lot of relevance for climate change and its impacts today. I’ll discuss the new data in separate posts over the next few weeks, but for now I’ll just mention a topic that came up repeatedly in conversations over the week – that was how to improve the flow of information from the paleo community to the wider climate community, as represented by the IPCC for instance.

There was a palpable sense that insights from paleo-climate (in this case referring mainly to the ocean sediment record rather than ice cores or records from the last millennium) were not being given their due, and in fact were frequently being misused. In a panel discussion (hosted by Stefan), people lamented the lack of ‘synthesis’ that would be useful for the outside community, while others stressed (correctly) that synthesis is hard and frankly not well regarded within the community or their funders. I think this is a general problem; many of the incentives for success within an academic field – the push for novel techniques, the ownership of specific slices of data, the desire to emulate the paths to success of the previous generation – actually discourage work across the field that pulls together disparate sources of information.

In the paleo-oceanography case, this exhibits itself in the overwhelming focus on downcore records (the patterns of change at a single point through time) and the relative lack of integrated products that either show spatial patterns of change at a single time, or that try to extract common elements from multiple events in the past. There are of course numerous exceptions – the MARGO project that compiled records from the peak of the last ice age, or the work of PMIP for the mid-Holocene – but their visibility makes their uniqueness all the more obvious. There were no ideas presented that would fix this overnight, but the discussions showed that the community realises that there is a problem – even if the solutions are elusive.

My second thought on China came from travelling through some of the most polluted cites in the world. Aerosol haze that appeared continuous from Beijing to Hong Kong is such an obvious sign of human industrial activity that it simply takes your breath away (literally). In places, even on a clear day, you cannot see the sun – even if there is no cloud in the sky. Only in the mountains or in deeply rural parts of the country was blue sky in evidence. This is clearly an unsustainable situation (even if you are only thinking about the human health impacts) and it points the way, I think, to how China can be engaged on the climate change front. If reducing aerosol emissions can be done at the same time that greenhouse gases can be cut, the Chinese will likely jump at the chance. As an aside, I noticed that Compact Florescent Light bulbs were being used almost everywhere you looked, and that the majority of Shanghai’s motorbikes and scooters were electric rather than gasoline powered. These efforts clearly help, but they are just as clearly not sufficient on their own.

Finally, the limited access to the Internet that one gets in China (through a combination of having better things to do with one’s time and the sometimes capricious nature of what gets through the Great Firewall) allowed me to take a bit of break from the constant back and forth on the climate blogs. In getting back into it, one appreciates just how much time is wasted dealing with the most ridiculous of issues (Hansen’s imagined endorsement of a paper he didn’t write thirty six years ago, the debunking of papers that even E&E won’t publish, and the non-impact of the current fad for amateur photography) at the expense of anything substantive. In effect, if possibly not in intention, this wastes a huge amount of people’s time and diverts attention from more significant issues (at least in the various sections of the blogosphere). Serious climate bloggers might all benefit from not getting too caught up in it, and keeping an closer eye on the bigger picture. We will continue to try and do so here.

Worth a Look

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We’re pleased to report that, after a rough start, Nature’s blog ‘Climate Feedback’ seems to have gotten back on track. We’re happy to endorse it as a useful resource for those interested in relatively informal discussions of issues at the leading edge of current climate research.

A good place to start are two excellent recent entries by Kevin Trenberth of NCAR. The first of these provides an update on where the scientific debate over the influence of global warming on hurricanes currently stands. The second responds to the latest attempt by the Wall Street Journal editorial page to foist fallacies about climate change upon its readers.

Climate Insensitivity

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Guest post by Tamino

In a paper, “Heat Capacity, Time Constant, and Sensitivity of Earth’s Climate System” soon to be published in the Journal of Geophysical Research (and discussed briefly at RealClimate a few weeks back), Stephen Schwartz of Brookhaven National Laboratory estimates climate sensitivity using observed 20th-century data on ocean heat content and global surface temperature. He arrives at the estimate 1.1±0.5 deg C for a doubling of CO2 concentration (0.3 deg C for every 1 W/m^2 of climate forcing), a figure far lower than most estimates, which fall generally in the range 2 to 4.5 deg C for doubling CO2. This paper has been heralded by global-warming denialists as the death-knell for global warming theory (as most such papers are).

[Read more…] about Climate Insensitivity

Friday roundup

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Schwartz in the news again:
Stephen Schwartz of Brookhaven National Laboratory makes our weekly roundup again this week. This time, its for a comment/reply in the latest issue of Nature concerning a previously published Nature piece “Quantifying climate change — too rosy a picture?” by Schwartz et al. In the original piece, Schwartz and co-authors argue that the IPCC Fourth Assessment Report (AR4) presents an overly confident assessment of climate sensitivity and potential future climate change. In the response by Forster et al, a number of IPCC lead authors point out that the Schwartz et al critique ignores or misinterprets several key IPCC findings.

update: if you don’t have a subscription, the original Schwartz et al Nature article is available here and the recent comment/reply is available here

update #2: It has been pointed out to us that the commentary by Stephen Schwartz and co-authors was published on the Nature Reports Climate Change website, rather than in the print journal Nature.