Explain again why we should panic? Study: 'No quick fix for global warming'

From ETH Zurich No quick fix for global warming

When fossil fuels are burned, other climate-forcing gases are produced in addition to long-lasting carbon dioxide. Diesel combustion in vehicles or coal in power plants creates soot particles, which also contribute to global warming, albeit only briefly as they disappear quickly from the atmosphere. Short-lived climate pollutants (also known as Short Lived Climate Forcers or SLCF) caused by human activities include methane and sulphur dioxide, and to a lesser extent fluorocarbons. They all have a measurable impact on the climate.

Politicians and industry have been considering the possibility of slowing down climate change by eliminating these SLCF without the need to immediately reduce CO2 emissions. The idea is that by eliminating short-lived climate pollutants, the international community buys time before it has to introduce CO2-cutting measures.

Doubtful climate benefit

A new argument against the unilateral reduction of SLCF emissions has now been put forth in a study just published in the scientific journal PNAS. An interdisciplinary team of researchers led by ETH climate scientist Joeri Rogelj used several models to calculate how the climatic effects of CO2 and SLCF break down and how they relate to each other.

In scenarios in which the average global temperature rises less than 2 degrees above pre-industrial levels, short-term measures to reduce SLCF had only a minor effect on the long-term rise in temperature. Even in the short term, SLCF reductions had a significantly lower effect in 2-degree scenarios.

The researchers were also not able to calculate a genuine long-term ‘climate benefit’ from the early restriction of emissions such as methane or fluorocarbons. These two SLCF species can affect temperatures in the short term, but the long-term benefits of short-term reduction measures for these two gases are no greater than if measures were taken only later.

CO2 and SLCF related

Even when additional reduction measures are implemented against black carbon, or soot, which is released when fossil fuels are burned, they do little to slow down global warming in a 2 degrees scenario. This is because if the global temperature rise is limited to 2 degrees, CO2 reduction measures would have to be taken, which would in turn cut the most important soot emissions.

In their study, the researchers show that the both the formation and the elimination of SLFC and CO2 must be considered as intrinsically linked. We can not look at one part in isolation because both emissions often come from the same source, namely fossil fuels, say the researchers.

For instance, a diesel engine emits both soot and CO2. If soot were limited by installation of a particle filter, for example, then at least one emission that warms the atmosphere would be reduced (and improve air quality ). But air pollution from soot stays in the atmosphere only briefly and therefore has an effect for only a very short period of time. Despite the filter, CO2 would still continue to be emitted and this is an extremely long-lasting greenhouse gas. Once released through combustion, it remains in the atmosphere for hundreds, even thousands, of years and continues its job as a driver of global warming over a long period of time.

No time to lose

“It is a fallacy to believe that we can win time or stabilise global warming by eliminating SLCF,” says Rogelj. Measures to reduce short-lived climate gases should instead be seen as a complement to CO2 reduction measures, not as a replacement. SLCF have an impact for only as long as they are being generated; once their supply fails, their warming effect soon disappears. The largest contributor to global warming is carbon dioxide and as it remains in the atmosphere for a long time, it works cumulatively. “If we were to stop all man-made emissions immediately, SLCF concentrations in the atmosphere would decrease quite rapidly to zero, but not so for CO2 concentrations.”

The study is based on three models: one for projecting transformations in the global energy system, an air pollution model and a climate model. The researchers reached their findings through a combination of all three.

The climate scientists calculated various scenarios with the models, including a very high-warming scenario in which no measures were taken to reduce CO2 emissions, so that CO2 concentrations in the atmosphere rise unabated to 2100. In other scenarios, CO2 emissions were curbed significantly to the extent that the target of limiting warming to below 2 degrees by 2100 is achieved.



Rogelj J et al.: Disentangling the effects of CO2 and short-lived climate forcer mitigation. PNAS, published online 3rd Nov 2014. DOI: 10.1073/pnas.1415631111


Climate change is one of the greatest challenges of our times. Human activities, like fossil-fuel burning, result in emissions of radiation-modifying substances that have a detectable, either warming or cooling, influence on our climate. Some, like soot (black carbon), are very short lived, whereas others, like carbon dioxide (CO2), are very persistent and remain in the atmosphere for centuries to millennia. Importantly, these substances are often emitted by common sources. As climate policy is looking at options to limit emissions of all these substances, understanding their linkages becomes extremely important. Our study disentangles these linkages and therewith helps to avoid crucial misconceptions: Measures reducing short-lived climate forcers are complementary to CO2 mitigation, but neglecting linkages leads to overestimating their climate benefits.


Anthropogenic global warming is driven by emissions of a wide variety of radiative forcers ranging from very short-lived climate forcers (SLCFs), like black carbon, to very long-lived, like CO2. These species are often released from common sources and are therefore intricately linked. However, for reasons of simplification, this CO2–SLCF linkage was often disregarded in long-term projections of earlier studies. Here we explicitly account for CO2–SLCF linkages and show that the short- and long-term climate effects of many SLCF measures consistently become smaller in scenarios that keep warming to below 2 °C relative to preindustrial levels. Although long-term mitigation of methane and hydrofluorocarbons are integral parts of 2 °C scenarios, early action on these species mainly influences near-term temperatures and brings small benefits for limiting maximum warming relative to comparable reductions taking place later. Furthermore, we find that maximum 21st-century warming in 2 °C-consistent scenarios is largely unaffected by additional black-carbon-related measures because key emission sources are already phased-out through CO2 mitigation. Our study demonstrates the importance of coherently considering CO2–SLCF coevolutions. Failing to do so leads to strongly and consistently overestimating the effect of SLCF measures in climate stabilization scenarios. Our results reinforce that SLCF measures are to be considered complementary rather than a substitute for early and stringent CO2 mitigation. Near-term SLCF measures do not allow for more time for CO2 mitigation. We disentangle and resolve the distinct benefits across different species and therewith facilitate an integrated strategy for mitigating both short and long-term climate change.

45 thoughts on “Explain again why we should panic? Study: 'No quick fix for global warming'

      • As applied to the earth’s atmosphere, no I don’t. A greenhouse is an enclosed space. Market gardeners the world over benefit from the ‘greenhouse effect’ by pumping in more CO² to boost crop yields by both nourishing them and marginally warming the air (the glass explains the bulk of the warmer indoors temp). Added CO² is great for crops in the open air too but the multiplier effect is less as CO² escapes into outer space. The earth is not a greenhouse, therefore the earth cannot be warmed by the greenhouse effect.

      • Of course greenhouse effect exists, there is no doubt about that. But I think, keeping the mass transfer limited to a glass enclosure, almost air tight, with elevated percentage of CO2; versus the huge exchange in the atmosphere and trace amounts of CO2…. well I might not be a great scientist…

      • The “greenhouse” effect in the atmosphere does not exist. At all.
        A greenhouse works by stopping convection (nothing to do with IR blocking… this has been tested.) In free air convection works just fine, thank you very much. Convection and the water cycle dominate the troposphere.
        In the stratosphere, gases like CO2 (that are most accurately called IR Radiative Gases) act as cooling agents.
        No greenhouse, and no warming from CO2.

      • Yes the GHE is vastly dominated by water vapor. Water vapor and the oceans that provides it keep our climate uneffected by small perturbations like volcanoes and trace gas IR energy absorption.
        CO2 is but a trace gas and Earth’s climate is a STABLE system.

  1. Many of the scientists studying the “climate” etc. do so from the “pristine” continent of Antarctica. That is the whole reason the NSF and governments around the world keep bases on the continent. I really don’t think the entire scientific community that uses the continent are quite willing to give up studying there although the only way to get to the study areas require enormous amounts of fossil fuel and once there the only way to stay alive is to burn even more.
    The irony of the National Science Foundation logo painted on top of a fuel tank containing hundreds of thousands of gallons of hydrocarbons is almost overwhelming.
    Switch to the Observation Hill camera and look at what is in the lower left corner.
    I spent 8 seasons there, in contact with many of the researchers and from my conversations, many use the “climate change” card just to get the research grants not because they actually believe the words they put on their grant application.

    • Yep … this could take a while. In the mean time I would appreciate a little compensation; a little something for the cause.

  2. If they can get a policy going where global emissions are seriously cut, they would immediately move to a win win situation. If warming continues – we are not cutting enough, if cooling starts – halelujah we saved the world. Please, please dont let that happen – the IPCC would be the start of a Global climate police

  3. I am a little disappointed by the article. I had been searching high and low for somewhere to purchase my SLCF credits. Now I am told that mitigating for SLCF’s is just a fools errand. Well, I guess I can just purchase some regular ol’ carbon credits instead … I feel less foolish already.

  4. Well, this is a report waiting to be used in an excerpt for the new K-12 Next Generation Science Standards.
    What will happen?
    What would you do if you could go back 5 years and prevent this?
    How do you imagine the world 10 years from now?
    What will you do to prevent that from happening?
    Create a powerpoint to get other students involved.
    Draw a picture of the world if we do not stop this catastrophe?
    Etc. Etc. Etc. as the king said in the King and I.

  5. alarmed at alarmists, but then turns alarmist if u read it all:
    3 Nov: UK Telegraph: Emily Gosden: ‘Alarmist’ green groups made ‘exaggerated’ claims about global warming, UN climate change scientist says
    Prof Myles Allen criticises ‘unhelpful’ alarmism by some NGOs as UN report says science is clear that drastic action is now needed to tackle climate change
    Green groups have been unhelpfully “alarmist” in making the case for tackling global warming – but the world now needs to take urgent and radical action if it wants to prevent dangerous climate change, leading UN scientists have said.
    Some claims that non-governmental organisations have made about climate change “have undoubtedly been exaggerated”, Professor Myles Allen, one of the lead authors of a major new report from the UN’s Intergovernmental Panel on Climate Change (IPCC) said.
    “NGOs have at times been alarmist over climate change… but the IPCC has been very clear and measured throughout. I think alarmism on any issue is unhelpful.”
    He suggested the alarmism had resulted in the general public getting the wrong impression about what climate change entailed.
    ***“People think climate change is just all about melting icecaps and the Arctic, the reality is climate change is about the weather changing in many parts of the world including where many people live,” he said…

  6. Annually, CO2 increases and decreases. The decrease is about 7 ppm over four months. That’s a rate of 21 ppm per year. If there were no increases, the atmosphere would be depleted of CO2 in about 20 years.
    I realize that the above is probably defective but, given the rapid decreases in CO2 during part of the year, I also refuse to believe that CO2 is particularly long lived (which Rogelj assumes).

  7. ” Despite the filter, CO2 would still continue to be emitted and this is an extremely long-lasting greenhouse gas. Once released through combustion, it remains in the atmosphere for hundreds, even thousands, of years and continues its job as a driver of global warming over a long period of time.”
    At this point my B.S. detector was destroyed.
    ETH has come a long way since One Stone was a student there. These days he could probably pass the entry exams without a problem.

  8. CO2 is a radiative gas just as is water vapor. During the day, CO2 and water vapor absorb and emit IR radiation such that it is a wash, and have no effect on the atmosphere or the Earth’s surface. The cooler atmosphere simply cannot warm the warmer surface.
    It is during the night that these gases, no longer pumped constantly by solar radiation, actively convert heat energy to IR radiation which is then lost to space. This is why the atmosphere cools so rapidly after sundown and why breezes pick up quite quickly on partly cloudy days as the air in shadow rapidly cools via these radiative gases.
    Nope, these are not greenhouse gases, they are radiative gases that serve to cool the planet, doing a job that is not included in the many climate computer models that DO NOT INCLUDE NIGHT-TIME!

  9. “Diesel combustion in vehicles or coal in power plants creates soot particles, which also contribute to global warming…”
    So, the soot that comes from diesel and coal combustion causes warming. But haven’t they also claimed that particulates and aerosols, especially from volcanoes, cause cooling and are the reason for the current pause in global warming? I guess it could be a difference between light and dark colored particles, but don’t volcanoes put out dark particles too? Or is it how high up the particles are in the atmosphere that makes the difference? Or is it just who you ask?

    • Soot causes warming. Volcanoes cause cooling because their emissions aren´t soot, and the cooling effect only takes place if the material reaches very high in the atmosphere.
      I suspect these studies are intended to downplay the effectiveness of measures other than the CO2 reductions because the political agenda is focused on fossil fuels (hell, maybe the real reason is their desire not to have developed nations depend on energy supplies from OPEC nations and Russia?).
      I would support soot reductions because this makes the air a lot more breathable and reduces lung disease. Methane emission reductions are also a low cost way to reduce greenhouse gas concentrations. And of course do want to reduce CFCs to repair the ozone hole.
      The problem I see is the way the science seems to be slanted in such a strange way, the extreme focus on CO2 tells me there´s something behind this beyond the global warming issue. This has to be driven by something else.

  10. To find the TVNZ story go to the web page and do a search on Bryan Leyland. Remember to spell the name correctly. It will give you the full interview.

  11. “… CO2 would still continue to be emitted and this is an extremely long-lasting greenhouse gas. Once released through combustion, it remains in the atmosphere for hundreds, even thousands, of years and continues its job as a driver of global warming over a long period of time.” [from the text]
    This sounds like “residence time” but must mean something else. A quick search suggests a value between 5 and 20 years. This is not to argue there haven’t been zombie CO2 molecules in the atmosphere for thousands of years.
    Probably what is meant is that the CO2 moves in many processes and some of those processes cause CO2 to reenter the atmosphere prior to long term burial. Trees grow – firewood burns. Thus, there may be a longer perturbation to the atmosphere than, say 5 to 7 years. If no new CO2 goes in to the atmosphere those processes would start to remove what is there. Some evidence suggests that 2 ppm is being taken out yearly (while we have emissions). Remove those emissions and the take out would continue. In about 50 years the concentration would drop by 100 ppm. As the concentration drops, the processes alluded to above, say plant growth, would respond by slowing. The tail of this would be long.

  12. Utter rubbish! Useless assumptions based on dodgy ‘science’. Everybody in the climate model or research game needs to be fired so we can use their salaries to do something useful. Like pay people to remove plastic from the ocean, for example. You know, actually DO something rather than getting paid to lie for a living!

  13. There they go again, conflating real pollution like soot and other aeorosols with the fake pollution, CO2. The irony is that the completely idiotic and useless effort to control fake pollution has the effect in developing countries of increasing real pollution. The kicker is that the effects of aeorosols on climate are unclear. In any case, aerosols are just another Warm herring. The climate couldn’t care less about them, and the only reason we should is due to air quality.

  14. “They all have a measurable impact on the climate.”
    So you can provide us with that measure? No? Anyone? Buehler?

  15. “It is a fallacy to believe that we can win time or stabilise global warming by eliminating SLCF,” says Rogelj.

    There is a more basic fallacy that makes that fallacy moot. The more basic fallacy is the belief that there are corroborated and multiply reinforcing observations that support the statement in the paper “like fossil-fuel burning, result in emissions of radiation-modifying substances [like CO2] that have a detectable influence on our climate”
    Rogeli et al is suspended in midair without support of observations showing significant climate change from CO2 by burning fossil fuels.

  16. Well, fine, those other gases are short-lived and not really a problem like that long-lived carbon dioxide is. Or so the author thinks. Apparently it is the greenhouse effect of carbon dioxide that is warming up the world that we have to fear. Evidently he has a misunderstanding about it because observations show that addition of carbon dioxide to the atmosphere is incapable of producing the greenhouse effect. First, no one has actually observed greenhouse effect in action. James Hansen attempted to do this in 1988 when he appeared in front of the U.S. Senate. His proof was 100 years of warming that could only be caused by the greenhouse effect. Checking out his temperature curve showed however that he was cheating because a third of this curve belonged to non-greenhouse warming and cooling. And that invalidates his original claim. This means that attribution of greenhouse warming to atmospheric carbon dioxide rests entirely upon greenhouse theory, not direct observation of the greenhouse effect. Presence of greenhouse gases is not the same as direct observation of greenhouse warming in action. This becomes very obvious when we consider the fact that for the last 18 years atmospheric carbon dioxide has been increasing without causing any warming whatsoever. The applicable greenhouse theory of Arrhenius has been known since 1896 and unequivocally predicts that this added carbon dioxide must cause greenhouse warming. Except that it does’nt. What is going on? you should ask. If you are a scientist and your theory predicts warming but nothing happens for 18 years it is clear that the theory is invalid. It belongs in the waste basket of history, same place where Phlogiston went. Since the Arrhenius greenhouse theory does not work we need one that does. It turns out that the only greenhouse theory that correctly describes our climate is the Miskolczi greenhouse theory, MGT. When Arrhenius predicts false warming MGT predicts what we see: addition of carbon dioxide to the atmosphere does not warm the air. According to MGT, the two most important greenhouse gases, water vapor and carbon dioxide, jointly form an optimum absorption window in the infrared whose optical thickness is 1.87 according to Miskolczi. If you now add carbon dioxide to the atmosphere it will start to absorb IR just as Arrhenius predicts. But this will increase the optical thickness. And as soon as this happens water vapor will begin to diminish, rain out, and the original optical thickness is restored. The added carbon dioxide will of course keep absorbing but the removal of carbon dioxide keeps total absorption constant and no warming is possible. This explains why there has been no warming for the last 18 years despite constant addition of carbon dioxide to air. This absence of greenhouse warming has important effects on climate science. First, it makes the enhanced greenhouse effect impossible. It also makes runaqway greenhouse effect that Hansen has talked about impossible. It so happens that according to IPCC it is that enhannced greenhouse effect that is the cause of the anthropogenic global warming or AGW. Since the enhanced greenhouse effect does not exist according to MGT follows that AGW likewise does not exist. It is nothing more than a pseudo-scientific fantasy of some over-eager climate scientist wishing to support the greenhouse hypothesis.

Comments are closed.