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Impacts of Climate Change – Part 2 of the new IPCC Report has been approved

Filed under: — stefan @ 4 April 2014

The second part of the new IPCC Report has been approved – as usual after lengthy debates – by government delegations in Yokohama (Japan) and is now public. Perhaps the biggest news is this: the situation is no less serious than it was at the time of the previous report 2007. Nonetheless there is progress in many areas, such as a better understanding of observed impacts worldwide and of the specific situation of many developing countries. There is also a new assessment of “smart” options for adaptation to climate change. The report clearly shows that adaptation is an option only if efforts to mitigate greenhouse gas emissions are strengthened substantially. Without mitigation, the impacts of climate change will be devastating.




Guest post by Wolfgang Cramer



On all continents and across the oceans

Impacts of anthropogenic climatic change are observed worldwide and have been linked to observed climate using rigorous methods. Such impacts have occurred in many ecosystems on land and in the ocean, in glaciers and rivers, and they concern food production and the livelihoods of people in developing countries. Many changes occur in combination with other environmental problems (such as urbanization, air pollution, biodiversity loss), but the role of climate change for them emerges more clearly than before.


Fig. 1 Observed impacts of climate change during the period since publication of the IPCC Fourth Assessment Report 2007


During the presentation for approval of this map in Yokohama many delegates asked why there are not many more impacts on it. This is because authors only listed those cases where solid scientific analysis allowed attribution. An important implication of this is that absence of icons from the map may well be due to lacking data (such as in parts of Africa) – and certainly does not imply an absence of impacts in reality. Compared to the earlier report in 2007, a new element of these documented findings is that impacts on crop yields are now clearly identified in many regions, also in Europe. Improved irrigation and other technological advances have so far helped to avoid shrinking yields in many cases – but the increase normally expected from technological improvements is leveling off rapidly.


A future of increasing risks

More than previous IPCC reports, the new report deals with future risks. Among other things, it seeks to identify those situations where adaptation could become unfeasible and damages therefore become inevitable. A general finding is that “high” scenarios of climate change (those where global mean temperature reaches four degrees C or more above preindustrial conditions – a situation that is not at all unlikely according to part one of the report) will likely result in catastrophic impacts on most aspects of human life on the planet.


Fig. 2 Risks for various systems with high (blue) or low (red) efforts in climate change mitigation


These risks concern entire ecosystems, notably those of the Arctic and the corals of warm waters around the world (the latter being a crucial resource for fisheries in many developing countries), the global loss of biodiversity, but also the working conditions for many people in agriculture (the report offers many details from various regions). Limiting global warming to 1.5-2.0 degrees C through aggressive emission reductions would not avoid all of these damages, but the risks would be significantly lower (a similar chart has been shown in earlier reports, but the assessment of risks is now, based on the additional scientific knowledge available, more alarming than before, a point that is expressed most prominently by the deep red color in the first bar).


Food security increasingly at risk

In the short term, warming may improve agricultural yields in some cooler regions, but significant reductions are highly likely to dominate in later decades of the present century, particularly for wheat, rice and maize. The illustration is an example of the assessment of numerous studies in the scientific literature, showing that, from 2030 onwards, significant losses are to be expected. This should be seen in the context of already existing malnutrition in many regions, a growing problem also in the absence of climate change, due to growing populations, increasing economic disparities and the continuing shift of diet towards animal protein.


Fig. 3 Studies indicating increased crop yields (blue) or reduced crop yields (brown), accounting for various scenarios of climate change and technical adaptation


The situation for global fisheries is comparably bleak. While some regions, such as the North Atlantic, might allow larger catches, there is a loss of marine productivity to be expected in nearly all tropical waters, caused by warming and acidification. This affects poor countries in South-East Asia and the Pacific in particular. Many of these countries will also be affected disproportionately by the consequences of sea-level rise for coastal mega-cities.


Fig. 4 Change in maximum fish catch potential 2051-2060 compared to 2001-2010 for the climate change scenario SRES A1B


Urban areas in developing countries particularly affected

Nearly all developing countries experience significant growth in their mega-cities – but it is here that higher temperatures and limited potential for technical adaptation have the largest effect on people. Improved urban planning, focusing on the resilience of residential areas and transport systems of the poor, can deliver important contributions to adaptation. This would also have to include better preparation for the regionally rising risks from typhoons, heat waves and floods.


Conflicts in a warmer climate

It has been pointed out that no direct evidence is available to connect the occurrence of violent conflict to observed climate change. But recent research has shown that it is likely that dry and hot periods may have been contributing factors. Studies also show that the use of violence increases with high temperatures in some countries. The IPCC therefore concludes that enhanced global warming may significantly increase risks of future violent conflict.


Climate change and the economy

Studies estimate the impact of future climate change as around few percent of global income, but these numbers are considered hugely uncertain. More importantly, any economic losses will be most tangible for countries, regions and social groups already disadvantaged compared to others. It is therefore to be expected that economic impacts of climate change will push large additional numbers of people into poverty and the risk of malnutrition, due to various factors including increase in food prices.


Options for adaptation to the impacts of climate change

The report underlines that there is no globally acceptable “one-fits-all” concept for adaptation. Instead, one must seek context-specific solutions. Smart solutions can provide opportunities to enhance the quality of life and local economic development in many regions – this would then also reduce vulnerabilities to climate change. It is important that such measures account for cultural diversity and the interests of indigenous people. It also becomes increasingly clear that policies that reduce emissions of greenhouse gases (e.g., by the application of more sustainable agriculture techniques or the avoidance of deforestation) need not be in conflict with adaptation to climate change. Both can improve significantly the livelihoods of people in developing countries, as well as their resilience to climate change.

It is beyond doubt that unabated climate change will exhaust the potential for adaptation in many regions – particularly for the coastal regions in developing countries where sea-level rise and ocean acidification cause major risks.

The summary of the report is found here. Also the entire report with all underlying chapters is online. Further there is a nicely crafted background video.

Wolfgang Cramer is scientific director of the Institut Méditerranéen de Biodiversité et d’Ecologie marine et continentale (IMBE) in Aix-en-Provence one of the authors of the IPCC  working group 2 report.

This article was translated from the German original at RC’s sister blog KlimaLounge.



Here is our summary of part 1 of the IPCC report.

177 Responses to “Impacts of Climate Change – Part 2 of the new IPCC Report has been approved”

  1. 51
    Walter says:

    For Chris D et al.

    The presidents actions amount to almost nothing regarding reducing CO2e emissions. The only real action was setting tougher standards (via the EPA) on vehicle engine emissions that come into affect in the future.

    What EPA is Doing about Climate Change?

    Almost nothing, as there is no genuine enforceable National emissions targets nor power to do anything about them bar engine emissions. This is what the EPA does today:

    – Greenhouse Gas Endangerment Findings = Good DECISION but with a NIL EFFECT to date.
    – EPA collects various types of greenhouse gas emissions data, via the “Inventory of U.S. Greenhouse Gas Emissions and Sinks” and the “Greenhouse Gas Reporting Program” = NIL ACTIONS

    – On September 20, 2013, the U.S. Environmental Protection Agency announced its first steps under President Obama’s Climate Action Plan to reduce carbon pollution from power plants. EPA is PROPOSING carbon pollution standards for new power plants built in the future = NIL ACTION TO DATE

    – On April 18, 2012, EPA finalized cost effective regulations to reduce harmful air pollution from the oil and natural gas industry, while allowing continued, responsible growth in U.S. oil and natural gas production. = NIL ACTION (because the EPA has grossly understated fugitive Gas emissions by accepting Industry advice, already proven wrong by multiple science studies that cam eout last year and this year)

    – Geologic sequestration is the process of injecting carbon dioxide (CO2) from a source, such as a coal-fired electric generating power plant, into a well thousands of feet underground and sequestering the CO2 underground indefinitely. = NIL ACTION

    – On May 13, 2010, EPA set greenhouse gas emissions thresholds to define when permits under the New Source Review Prevention of Significant Deterioration (PSD) and Title V Operating Permit programs are required for new and existing industrial facilities. = minor ACTION, small effect.

    – EPA is also responsible for developing and implementing regulations to ensure that transportation fuel sold in the United States contains a minimum volume of renewable fuel. = Minor ACTION, minimal effect

    – EPA and the National Highway Traffic Safety Administration (NHTSA) are taking coordinated steps to enable the production of a new generation of clean vehicles = NIL ACTION, still at a “proposed stage” for any future changes.

    FACTS: The US Clean Air Act is NOT effecting Carbon Emissions Cuts in the USA. The EPA is NOT responsible for driving down Carbon Emissions except in some very narrowly framed constraints. The EPA is NOT responsible for meeting NATIONAL Carbon Emissions targets in the USA.

    FACT: THIS IS A NEW PROPOSAL NOT A SET IN STONE POLICY OF THE US GOVT “The US policy is to cut emissions by 17% by 2020 from 2005 emissions and continue cutting to reach a goal of 83% cut by 2050.”

    It is merely a Hope on a Wing and a Prayer … it is hypothetical and an “ambition” of Obama’s White House .. it is NOT a Fact, yet.

  2. 52
    Fred Magyar says:

    Hank Roberts @30,

    “But if you want good economic advice, ask the ecologists. They don’t fool themselves.”

    It might be of some interest to note that both the words economy and ecology have the the Greek word ‘eco’, οἶκος as a root, Greek word οἰκονόμος (i.e. “household management”), a composite word derived from οἶκος (“house, home or place of habitation”) and νέμω (“manage; distribute”) by way of οἰκονομία (“household management”). In other words ‘economy’ is the management of the the place of habitation through the application of man made rules or laws.

    While neo classical economists like to say that their field of study is a true science, unfortunately it seems they are stretching the definition of what science really is all about…

    The word Ecology on the other hand is derived from the Greek as follows : ‘οἶκος’, “house”; -λογία, “study of. And most modern day ecologists try to apply the fundamental rules of the scientific method in the study of our home.

    IMHO, every current economics course should be based on biophysical principles and should start with a Review of Ecosystem Thermodynamics 101

  3. 53
    Rob Nicholls says:

    Going back to the post on Impacts of climate change, I think the post is excellent. I have so far found WG2’s SPM quite difficult to get my head around and I believe there is a need for articles like this which summarise WG2’s findings and make clear the kinds of futures the science says we might be facing if we don’t start cutting GHG emissions v soon.

    Chris Dudley (#41), thanks for your response to my comment. China is increasing its fossil fuel use but I think that USA’s per capita GHG emissions are still way above China’s (although the latest figures I have found so far are for 2010). I don’t believe that the US will be in any position to preach to China about China’s GHG emissions until the US’s per capita emissions are lower than China’s (and even then I think that historical emissions have to be taken into account). I agree that China has to tackle its rising emissions (and quickly if we want to have a chance of meeting RCP 2.6) but the US, UK and other very affluent nations with very high per capita GHG emissions have to get their own houses in order before they start trying to take the moral high ground on this issue.

  4. 54
  5. 55
    flxible says:

    Chris Dudley, please take the Sinophobic politics elsewhere, China does NOT have a goal or policy of increasing pollution or emissions. Like every country, they have a goal of increasing the ‘prosperity’ of their populace. The “developed” world is currently the enabler of that.

    The only priority everywhere is to turn the global energy economy – if you want tariffs, put export tariffs on the dirty energy being sent to China by the developed nations [particularly the US, Australia and Canada] who are pursuing their own prosperity by supplying the coal, oil, gas and tar sands to China, which is the “enabler”.

  6. 56
    DIOGENES says:

    Chris Dudley #18,

    “The science says that it is future emissions, not past emissions that are responsible for future warming.”

    Actually, the science says that it is past AND future emissions that are responsible for future warming. If we cease all CO2 emissions today, the aerosols essentially precipitate out immediately, while the CO2 remains for many decades. There is roughly a ten-twenty year period for the atmosphere to adjust to the increased heating from the reduced Albedo, and the temperature reaches a peak somewhere between 1.2-2 C. After the peak, there would be a steady decline (in theory), but the decline would be reduced by the carbon feedbacks we have already triggered (e.g., from thawing Permafrost).

    However, the magnitude of the peak is of major concern, and it was a strong component of Hansen’s recent Plos One paper. If the temperature were to peak near 2 C, which is certainly possible given present uncertainties about climate sensitivity, aerosol forcing, and other critical parameters, then substantial carbon feedbacks could be triggered that would obliterate the peak and drive the temperature further on an upward trajectory. As far as I have seen, none of the published studies on immediate CO2 cessation take major carbon feedbacks into account when computing temperature trajectories. This is the main reason that Spratt, Salter, Wadhams et al believe that some type of geo-engineering to replace the aerosols would be necessary.

    In a sense, the developed countries, with the USA in the lead, have created a ‘time-bomb’ with their past copious use of fossil fuels. Additional copious future use of fossil fuels only adds to the problem.

  7. 57
    SecularAnimist says:

    Chris Dudley wrote: “Bottom line in what you are saying, China is increasing fossil fuel use.”

    Sure, that’s the bottom line in what I’m saying — IF you ignore everything I actually wrote.

    The “bottom line” is that your proposal for the USA to impose “fines” on China for China’s fossil fuel use is absolutely hypocritical and nonsensical given that the USA is actively aiding and abetting and encouraging and enabling China’s fossil fuel use by exporting record amounts of coal and petroleum coke to China.

    If you want the USA to do something effective to reduce China’s fossil fuel use, then call for a complete ban on US fossil fuel exports to China — and to any other country, for that matter.

    If, on the other hand, you want to engage in hypocritical and nonsensical China-bashing, carry on as you were.

  8. 58
    Pete Dunkelberg says:

    wili: “Apparently most models discount major carbon feedbacks. Why? I don’t know.

    From the third source from your link at #9:

    “these models have typically neglected the permafrost carbon pool, which has the potential to introduce an additional terrestrial source of carbon to the atmosphere.””

    Focus on the word “potential.”

  9. 59
    DIOGENES says:

    To the Moderators,

    An interesting climate science issue has arisen on this thread: what would happen to atmospheric temperature and other variables if fossil fuel use were to be terminated immediately? The posted projections have ranged from immediately declining temperatures to flat temperatures to some peak temperature to decades-long increasing temperatures. Since the moderators are first-class climate scientists, it would be useful if they would weigh in on this topic. What are the physical phenomena involved under such conditions, what temperature profiles would be expected and what are the associated uncertainties, and do the moderators agree with the concerns expressed in #56?

    [Response: It’s been discussed many time before: here and here. – gavin]

  10. 60
    Mal Adapted says:

    Secular Animist:

    If you want the USA to do something effective to reduce China’s fossil fuel use, then call for a complete ban on US fossil fuel exports to China — and to any other country, for that matter.

    What I want the U.S. to do is impose an effective tax on fossil fuels at the source (mine or well-head if domestic, port-of-entry if imported) based on carbon content, and a Border Adjustment on imported goods at the same time:

    Border Adjustments, also known as Border Tax Adjustments or Border Tax Assessments, are import fees levied by carbon-taxing countries on goods manufactured in non-carbon-taxing countries.

    The impetus behind border adjustments is the desire to ensure a level playing field in international trade while internalizing the costs of climate damage into prices of goods and services.

    It would have to be adjudicated, but there’s apparently reason to think this is permitted under WTO law:

    [former WTO appellate officer Jennifer] Hillman concludes that “…provided that policymakers carefully design a [carbon] tax, keeping in mind the basic requirements of the WTO not to discriminate in favor of domestic producers or to favor imports from certain countries over others… the treat of WTO challenges should not present a barrier to policymakers wishing to adopt a carbon tax system now.”

    I may be behind the times, but I think the U.S. still has sufficient global economic leverage that even China would have to pay attention to something like this. I’m talking it up, and hoping for an outbreak of common sense in our leaders.

  11. 61
    Chris Dudley says:

    Walter (#51),

    Perhaps you’ve never heard of wedges. So, again, US policy: 17% cut from 2005 level by 2020. We’re expected to get there based on EPA efforts already in the works. 83% cut by 2050. Still figuring that one out but it’s the goal. Amory Lovins has outline a number of detailed scenarios, and the goal looks quite feasible.

    So, you’ve found many things that are being done and you claim all of the are small. Yet we have been cutting, so something is definitely working. I would say that one reason you are not catching on very well is that you don’t seem to have looked CAFE standards.

    Get yourself educated. I got Lovin’s book from the library. It’s pretty easy to follow.

  12. 62
    Chris Dudley says:

    Mal Adapted (#60),

    Exactly. So long as a country is addressing and environmental issue domestically, it can impose duties, tariffs, border adjustment taxes, what ever you want to call it under the GATT. The WTO is the body that enforces the GATT.

    In the US, regulation under the Clean Air Act, not a carbon tax, is what is cutting emissions, but that is not important. What is important is that we are taking action to cut emissions. That gives us standing.

  13. 63
    Chris Dudley says:

    Kevin (#46),

    Actually, the 17% cut is US policy. It has been presented as such in world forums. That makes it extend beyond administrations.

    Unlike Canada, in this area, we attempt to keep our commitments.

    I would point to this: “I don’t understand why you are harping on China and India, Chris; emissions cuts on their part are necessary but not at all sufficient.” and say you’ve got it. Necessary is the operative word. Most others are headed in the right direction and are looking for ways to do more. But, China and India are not. They must be turn round, not just nudged further in the right direction.

    Regarding EIA analysis of the US emissions prospects, you need to read more carefully. They are specifically avoiding including anticipated policy. It gives a baseline against which thing like stationary source regulation can be measured.

    That also makes your quote from the analyst interesting as well. If coal merely stabilizes, what happens to gas and oil? Transportation seems to have been neglected and yet the market for cars in China is huge. Leaving that out seems a little shortsighted if one is making projections.

  14. 64
    Chris Dudley says:

    Rob (#53),

    It is not really about taking some moral high ground, it is about how GATT is written. We’re cutting emissions. We can and should put tariffs on nations that are increasing emissions.

    And, regarding per capita emission, so long as China has per capita emissions above our goal, they should be cutting, not growing on stabilizing emissions. They have badly overshot while other developing nations are pursuing clean development paths.

    China is the blockade to achieving RCP2.6. Tariffs may unblock that path.

  15. 65
    Chris Dudley says:

    SA (#57),

    I don’t care much about petroleum coke exports, but mountain tops in Appalachia and US coal miners’ lives should not be sacrificed for coal exports. The US needs to commit to end mountain top removal and coal mining fatalities, and then do it before coal is exported at all.

    Other than that, I don’t care where China gets coal or petroleum coke so long as they are burning less next year and less after that and so on. Keep cutting until we are on RCP2.6 and staying there.

  16. 66
    Chris Dudley says:

    Hank (#42),

    Feedbacks that are not runaway are driven. End the driver and the feedback ends as well. So, that would be one motivation to not account for them. They would not be active. There is a paper in a list you put up that claims that permafrost may already be a runaway feedback. If so, the RCP2.6 will have to involve much more biochar and other such efforts to shift the permafrost carbon into temperate soils.

  17. 67
    Chris Dudley says:

    Walter (#47 and #48),

    Ignoring these. Too counter factual.

  18. 68
    Walter says:

    US Falling Emissions a Mirage: Offshoring and Fracking 02 April 2014
    Bruce Melton is a professional engineer, environmental researcher, filmmaker, and author in Austin, Texas.

    Stanford Report, February 13, 2014 The first thorough comparison of evidence for natural gas system leaks confirms that organizations including the Environmental Protection Agency (EPA) have underestimated U.S. methane emissions generally, as well as those from the natural gas industry specifically.

    Scientific papers and academic reports on CSG and Shale Gas Mining
    Item 1 The first ever ‘Science Paper’ on the GHG Footprint of Unconventional Gas extraction was not published until March, 2011.

    IPCC AR5
    “Further near-term warming from past emissions is unavoidable due to thermal inertia of the oceans. This warming will be increased by ongoing emissions of GHGs over the near term, and the climate observed in the near term will also be strongly influenced by the internally generated variability of the climate system. Previous IPCC Assessments only described climate-change projections wherein the externally forced component of future climate was included but no attempt was made to initialize the internally generated climate variability. Decadal climate predictions, on the other hand, are intended to predict both the externally forced component of future climate change, and the internally generated component.” […]
    “The loss of carbon from frozen soils constitutes a positive radiative feedback that is missing in current coupled ESM projections.” […]

    IEA world energy outlook 2013
    “Fossil Fuel Subsidies in 2011 were equivalent to an incentive of $110/tonne of CO2.” [ slide 11/17 ]
    (IEA .. fossil-fuel subsidies, which we estimate rose to $544 billion worldwide in 2012. )

  19. 69
    wili says:

    CD at #66 wrote: “There is a paper in a list you put up that claims that permafrost may already be a runaway feedback. If so, the RCP2.6 will have to involve much more biochar and other such efforts to shift the permafrost carbon into temperate soils.”

    Good idea…if biochar was actually a proven reliable readily mass-producible technology.

    But it isn’t, unfortunately.

  20. 70
    Chris Dudley says:

    flxible (#55),

    GATT seems ambiguous on oil, gas and coal exports. And, gas exports have been restricted by Russia in the past while OPEC is an export restricting cartel.

    So, your proposal might have some benefit. But it does seem kind of like pushing on a string. Import duties on Chinese manufactured goods actually cut emissions by reducing Chinese energy consumption. They can be carried out unilaterally by countries that are cutting emissions. Restricting exports would merely give another seller a larger slice of the export market. So, you would need a cartel like OPEC to have any effect. The US would definitely not participate in such a cartel for oil I think. For coal, Australia would need to be a member and Australia has had difficulty meeting its Kyoto obligations. Thus, Australia’s environmental laws may not be strong enough to give it standing to impose restrictions if that is the grounds for doing that sort of thing. Indonesian membership would also be needed.

    So, I don’t think your proposal would get itself together to be useful on a timescale relevant to getting on RCP2.6.

    One export restriction that the US could do that would make some sense is to declare natural gas to be a climate strategic resource and only export it to replace coal. An exception may be needed for Japan owing to their nuclear difficulties, but a time limit on the exception might be useful. LNG has some climate problems but probably still helps as a coal replacement if taken from deep or conventional gas deposits. Fracking seems like it has too much leakage. I doubt the restriction would have much effect, but it might be usefully symbolic.

    I’ve said elsewhere that US coal miners’ lives and Appalachian mountain tops are not worth sacrificing for coal exports. We should have an export moratorium until coal mining fatalities have held at zero for a few years and mountain top removal mining has been banned.

  21. 71
    Killian says:

    Most earlier research leaves out carbon feedbacks from permafrost and other sources. Just adding (some) of the carbon feedback from permafrost to the equation at least offsets the uptake by oceans and by non-permafrost land sinks.

    Check out the third source there, MacDougal et al. Including just this one carbon feedback, warming continues even with immediate cessation of all further CO2 emissions.

    Comment by wili — 5 Apr 2014 @ 5:47 PM

    This is why talk of adaptation may be interesting, but for all intents and purposes is suicidal. We know the Arctic is losing carbon more rapidly than is safe. Yet another study, recently published, shows the Arctic is emitting twice the carbon previously thought. Why, pray tell, is this always the case? Because it’s a crumbling system with chaotic and non-linear features. Look at a graph of bifurcations sometime. My estimate is that we are into the fourth or fifth bifurcation for the Arctic already. If true, we’re in deep sheep poop. Even if I’m wrong (this is based on a simple analysis of phase changes in ASI since 1900), we’re still past the first one, or the ice wouldn’t be melting. I think most would accept at least one more tipping point was hit in the 2005 – present time frame. That’s two. So, in the absolute simplest terms we now have a system that had one singular path that now, in very lay terms, has four.

    How can anyone feel comfortable about that? Add to this Hansen et al.’s finding a couple years ago that there was some evidence for an ice-free Greenland even at 400 ppm. Other recent findings are that overall sensitivity is closer to 4.5 than 3. (Another I told you so: I said it had to be at the high end, between 4.5 and 6, a long time ago.) If all of this is true, then the risk associated with adaptation vs. mitigation is still an existential, ELE-level event. How does one justify that?

    There is only one choice that flows from the simple logic determined not by the models, but by direct observation. Add in the modeling, and it’s a no-brainer: expecting the planet to stop once we’ve pushed it past several tipping points is no different than Russian Roullette. There’s at least one chamber filled, and death comes if you play long enough.

    Surely you are all aware the same process that is causing dipole anomalies and breakdown of the Arctic circumpolar winds and freezing the mid-latitudes is creating a high pressure ridge that pushed the storm track up into Alaska all winter? How long can that go on before the place gets downright soggy and pours CH4/CO2 into the atmosphere in a feedback we can’t stop?

    There is only one solution: Cool the planet. And there is only one safe way to do that: Sequester carbon naturally. And the only way for that to be effective in a time frame that *might* be safe so we can put the acidification and CH4 genies back in their bottles, is to reduce consumption to 10% or so of current consumption in OECD countries.

    So sayeth Kevin Anderson, which shocked the poo out of me.

  22. 72
    Chris Dudley says:

    DIOGENES (#56),

    I have included a “modulo aerosols” caveat in places.

    But, what you are describing places even greater responsibility on China for dangerous climate change. Countries, like the US, that have been cutting emissions have also be scrubbing their smoke stacks and using low sulfur coal and oil to cut those aerosols. If there is a warming as you describe, it will be the fault of China burning coal inefficiently and without scrubbing. Associated adaptation costs should be paid by China.

  23. 73
    Killian says:

    Killian (#34),

    You’ve allowed yourself to be bamboozled by “energy intensity.” Just imagine Dick Cheney sitting on your shoulder whispering sweet nothings in your ear. That is China’s energy policy: increase emissions with a slight nod to efficiency.

    No, I haven’t. I concern myself with what is sustainable. That means paying attention to net energy and systems. I don’t care what anyone says, I care about what they do, and my requirements are stringent wrt climate policy, resources and sustainability. The Chinese gov’t acknowledged the dangers of climate change years ago and started planning to that end at the same time. As I said, they have some wacky things they have to deal with, and they have to, like we do, phase out some stupid policies that obviously had to be part of planning before they fully acknowledged climate.

    Regardless, you can’t have a climate policy at all when one party, the TeaPublicans, is holding the nation hostage. Regardless of all the other problems China faces, and they are massive, they don’t have that one to deal with. This makes it likely they will turn their oil tanker into a windmill before we will.

    My previous comments stand.

    I would say also that you have misunderstood lag in the climate.

    Based on what? That I know they kick in about 30 years after? You out your mind, son?

    Further, feedbacks, if they are not runaway, need to be driven, so ending the driver ends the feedback.

    Comment by Chris Dudley — 5 Apr 2014 @ 8:40 PM

    And? Kinda why I’ve been calling for <300 ppm. Or are you saying if we stop at 480 or so, all will be well? That's a prediction. That's a bad idea. Try a scenario. And the scenario I choose is the worst case because that is where the existential threat lies, and the odds of it are non-zero, so must be planned to. That means back to 300ppm, not 350. The ice started melting at 300 – 315. Just stopping is too dangerous to accept. We must mitigate and turn back the dial.

    I trust the science will support this in the end, just as it has everything else I've said since 2007.

  24. 74
    Killian says:

    Walter (#51),

    Perhaps you’ve never heard of wedges. So, again, US policy: 17% cut from 2005 level by 2020. We’re expected to get there based on EPA efforts already in the works. 83% cut by 2050. Still figuring that one out but it’s the goal. Amory Lovins has outline a number of detailed scenarios, and the goal looks quite feasible.

    Comment by Chris Dudley — 6 Apr 2014 @ 4:47 PM

    Actually, we can get to negative emissions with a combination of simplifying and natural sequestration. Technically possible to get to <300 ppm within 20 or so years. Politically, probably more like 100. But simple, doable, and necessary. Lovins, btw, currently is not on the right track. He still thinks innovation and efficiency can get us to a sustainable world with gadgets and doodads. Simple logic says this isn't remotely possible.

    Even Hansen understands the major role sequestration will play, but his numbers are low because he's not counting the vast spread of home gardens/farms in addition to public gardens, turning current FF-based farming into natural farming, reclaiming marginal lands/deserts, things like bio-char and changes to how we use animals on the land.

    We can so simply return to pre-industrial levels… but too many still want your cars and phones and whatnots. Lovins among them. He's a bright fellow. He'll figure it out.

  25. 75
    Walter Pearce says:

    Chris @ 61…OK, fine, I see you can’t or won’t grasp the concept of cumulative emissions, and what that says about the the job ahead. Btw I read Lovins and as for getting educated on this topic, you would do well to read Hank’s links above with as much as an open mind as you can muster.

  26. 76
    DIOGENES says:

    Hank Roberts #8/Gavin #59,

    I find this interchange strange in the extreme. Hank Roberts, in post #8, quoted from a Letter on the immediate CO2 cessation problem, to the effect that “And subsequent temperatures (depending slightly on the model you are using) would either be flat or slightly decreasing.” In response to my request (#56) for moderator input on this issue, Gavin stated in #59: “[Response: It’s been discussed many time before: here and here. – gavin]”

    I went back to the two threads recommended by Gavin. The first thread accepts the temperature decline statements in the Letter as given, and the usual voluminous posts follow. The second thread admits that the aerosol precipitation (and other quantities) were omitted in the Letter (and in the Article on the first thread), and shows graphs of the temperature increasing to a peak and declining afterwards, as I stated in #27 and #56. Comment #13 in the second thread was by none other than Hank Roberts. So, this raises two questions.

    First, why did Hank Roberts quote from the Letter in the present thread that temperature would be flat or slightly decreasing after immediate CO2 cessation when he was aware that aerosol precipitation would lead to a brief temperature increase? Second, why wasn’t that point made by the moderators on Hank Robert’s post #8; it would have saved much erroneous discussion?

  27. 77
    Fred Magyar says:

    Chris Dudley @ 41,

    “That is China’s energy policy: increase emissions with a slight nod to efficiency. The US policy is to cut emissions by 17% by 2020 from 2005 emissions and continue cutting to reach a goal of 83% cut by 2050. China’s policy is to increase emissions out to 2040 and beyond.”

    Popycock! Actions speak louder than words! The US is merely exporting its emissions to other parts of the world. last year Americans imported roughly $450 billion worth of goods from China alone…

    In 2013, the US bought US$2.33 trillion worth of imported products. That total is up by 45.5% since 2009.

    Yeah, bad bad China, burning all that oil and coal to produce cheap goods for Americans who continue to buy and use gas guzzling cars and trucks, fly around in planes, and waste lots of fossil fuel produced electricity. Let’s not forget our industrial agricultural processes either!

    When US policy is to start seriously restricting all of the above and begins to impose large carbon taxes on imported goods produced abroad I might have a little more sympathy for your flag waving and holier than thou attitude with respect to the rest of the world.

  28. 78
    Chris Dudley says:

    Gavin in (#59),

    It might be worth a post to look at MacDougall et al. Journal of Climate Dec2013, Vol. 26 Issue 23, p9563-9576. 14p.
    in the context of David’s maximum available 1000 GtC from permafrost melting estimate here:

    Are the two views consistent?

  29. 79
    Hank Roberts says:

    CD, your opinion, you’ve made it clear, isn’t going to change.

    The two topics at RC on climate change commitment, with cites to the science, address uncertainties you don’t want to.;

    Could you blog your opinion, so discussion of the science including the uncertainties can proceed here?

    E.g., from the second of the two links Gavin provided above:

  30. 80
    Chris Dudley says:

    Regarding MacDougall et al. Journal of Climate Dec 2013, Vol. 26 Issue 23, p9563-9576. 14p. A preprint version uses available soil carbon of up to about 2000 Gt (emitted out to 2300) and requires that we do nothing about non-carbon dioxide greenhouse gases to get an effect of rising carbon dioxide concentration after cessation of carbon dioxide emissions. Since non-greenhouse gas emissions seem to be quite a focus of diplomatic efforts, such a scenario seems unlikely: we are unlikely to cut carbon dioxide only.

  31. 81
    Chris Dudley says:


    The MacDougall et al. soil carbon pool is up to 570 GtC. The 2000 GtC (1920 Gt C) is fossil fuel emissions. And, for RCP2.6:

    “Note that even the most optimistic estimate
    for future non-CO2 greenhouse gas forcing is consistent with
    approximately balancing the ocean uptake of carbon with emissions
    from the terrestrial biosphere in the present simulations.”

    Here are their policy recommendations:

    “The results presented here indicate that sharp reductions
    in the concentration of non-CO2 greenhouse gases
    may be required to prevent CO2 from continuing to
    build up in the atmosphere (albeit slowly). That said,
    stabilizing atmospheric greenhouse gas concentrations
    may not be sufficient to prevent ‘‘dangerous anthropogenic
    interference with the climate system.’’ Achieving
    that goal may require the removal of greenhouse gases
    from the atmosphere (e.g., Hansen et al. 2008). It is
    possible that enhanced natural sources of biogenic methane,
    irreversible damage to the caping formations of
    geological methane, and/or slow destabilization of methane
    clathrates could replace the current anthropogenic
    sources of methane (O’Connor et al. 2010). This could
    keep non-CO2 greenhouse gas concentrations above the
    quantity needed to stabilize atmospheric CO2, even if
    anthropogenic sources of these gases are eliminated.”

    So, in my comment to Hank (#66), this should not be considered a runaway but rather driven feedback. The driver is non-carbon dioxide greenhouse gas emissions post carbon dioxide emissions.

  32. 82
    Hank Roberts says:

    CD, “end the driver and the feedbacks _eventually_ end” would be closer to correct, though far too vague.
    — a driver can have several feedbacks, with varying lag times.

    Long Cao et al 2014 Environ. Res. Lett. 9 024012 doi:10.1088/1748-9326/9/2/024012
    Response of ocean acidification to a gradual increase and decrease of atmospheric CO2

    There’s interesting science to learn here (and few other places to hear from the scientists). Please.

  33. 83
    Jim Larsen says:

    18 Chris D said, “We don’t pay China to be good because we share the blame, we fine China for being bad because the blame in entirely theirs. ”

    um, China produces something like 1/5th the emissions per capita as the USA, so under your scenario China should be able to fine the USA. Remember, past emissions “don’t count”, so the USA doesn’t get to grandfather in past bad behaviour.

  34. 84
    Chris Dudley says:

    Hank (#76),

    “Please” Wouldn’t “Thank you” be better. You asked a question, I answered it. We obviously were not discussing acidification. So, I am a scientist. I’m an astrophysicist with graduate training in atmospheric and planetary science. I have a basis for knowing what is bogus and what isn’t. I cite you politely and you jump all over me. What’s the problem really?

  35. 85
    Chris Dudley says:

    Walter (#68),

    Regarding offshoring emissions, about the only thing you can do about that is to invoke the environmental language in the GATT to impose tariffs on those products that had their emissions offshored. And the only countries that have standing to do that are the ones that are themselves cutting emissions domestically, like the US. Your position really seems to have some contradictions in it.

  36. 86
    Hank Roberts says:

    > We obviously were not discussing acidification.

    Not obviously, and I’m responding to your claims, which are broad.

    As I read you, you’ve been saying that
    — all the fossil fuel burned to date doesn’t count as a problem
    — anyone burning fossil fuel after this point is responsible for the consequences, and
    — feedbacks stop as soon as forcings stop.

    Ocean pH will change in response to the past century’s fossil fuel use for a long time to come, and not in good ways.

    Melting Greenland is another such cost, externalized for the past century or more into our future, happening sooner than expected.

    If you mean to narrow your claim solely to air temperature, why bother? The world isn’t that simple.

    Mistakes were made.

  37. 87
    Walter says:

    CD #85 re “Your position really seems to have some contradictions in it.”

    That seems to be because, despite being an ‘astrophysicist’ and University Graduate, you are too nationalistically arrogant and far too stupid to work it out by yourself. Even when it is laid out for you like a feast on the Kings banquet table. *PLONK*

  38. 88
    Chris Dudley says:

    Walter (#87),

    I’ll try one more time. Fred (#77) I think you did not see my #85 but this is also relevant to your post.

    Understand that while we where increasing emissions, we had no choice but to accept imports from China without restriction owing to international law. Now we are cutting emissions and we are doing that under an endangerment finding by the EPA as part of its function in enforcing the Clean Air Act. We have a domestic law that is addressing an environmental issue. And, we have a trading partner that has no such law and its actions are affecting our environment in that particular issue. Under this condition, we can restrict imports from China where we absolutely could not before.

    You can really only use the phrase “outsourced emissions” or that kind of thing if you have a choice about where to buy things. We did not until the endangerment finding. Now we do, and we should do something about it.

    Once China starts cutting emissions, we’ll be back to regular old free trade and we will be back to no (collective) choice on where things come from (other than the choice to abide by WTO disciplines).

    And Walter, I graduated from a college that is particular about calling itself a college. I took my doctorate at a university.

  39. 89
    Chris Dudley says:

    Hank (#86),

    You write:

    “Not obviously, and I’m responding to your claims, which are broad.

    As I read you, you’ve been saying that
    – all the fossil fuel burned to date doesn’t count as a problem
    – anyone burning fossil fuel after this point is responsible for the consequences, and
    – feedbacks stop as soon as forcings stop.”

    I would say that I’ve been trying to make careful narrow statements which you are reading broadly.

    So, here is what I’ve said, which if you look carefully is not what you have perceived.

    Until climate change became dangerous, emissions were not a problem for legal liability for the damage that climate is now causing. It’s nearly a tautology so I don’t see why you’d have a problem with that.

    I’ve also said the science says that if you stop greenhouse gas emissions, the warming stops, so past greenhouse gas emissions are not the reason for future greenhouse warming, future greenhouse gas emissions are. Non-greenhouse aerosol emissions that are associated with greenhouse gas emissions can put a wrinkle in this. This should be a statement you can agree with. And, it also refines the legal issue above. In that statement, you can’t have liability without damage. We can refine it to say that emissions prior to known damage were innocent if we were surprised by the onset of of dangerous climate change, which we were. They may be a cause, but they are an accidental cause (no intent to harm) and it is only a slight fraction of historical emissions that could be a cause. Ending emissions in 2004 would likely have left us going round and round about attribution even though there had been some deadly heatwaves by then. (OK so that last bit is not something I’ve said before but it is interesting and illustrative.)

    Now, after dangerous climate change has arrived and is recognized, there is safe harbor from liability: cut emissions. The US EPA had found greenhouse gas emissions to be dangerous and is regulating them so that we cut emissions. No one can put tariffs on our exports because we are emitting. We are cutting emissions in recognition of the danger. Nations that are not cutting emissions don’t have that safe harbor. They have liability, and under GATT, tariffs may be placed on their exports by nations that are cutting emissions. Perhaps to use the word “responsible” in a way Kevin might approve, some nations are taking responsibility by cutting emissions, and others should have responsibility thrust upon them. Rather obviously, you can spend climate tariffs anyway you like, once you can extract them, but spending them on climate damage such as excess crop insurance payouts would be an appropriate use.

    On your last reading, I’ve been trying to use the word driver for a feedback. Warming is the driver for increased soil carbon respiration, for example. Ending the driver ends the feedback if it does not drive itself (runaway). If warming stops with the reduced forcing, then the driver for the feedback stops too. If you are thinking of forcing and warming as interchangeable then that may be why you are writing that, but that is not how I am thinking about it, or writing about it I hope, since it does not really distinguish what feedbacks are. You did ask a question about greenhouse gas feedbacks which I answered. My answer does not appear to be flawed in the manner you suggest.

  40. 90
    Chris Dudley says:

    Jim (#83),

    That figure is likely out of date. In 2011, China’s per capita emissions were 40% of the US per capita emission and typical of Europe.

    However emissions in China are growing and emissions in the US are falling. Some estimate that per capita emissions will be the same in 2017.

  41. 91

    Chris D.–OK, I’ll give you the point that the intended 17% reduction of US emissions has been presented as ‘national policy.’ Nonetheless, that does not mean that it will “extend beyond administrations.” Had Romney won, it would have been history by now, and American policy would essentially have been “Drill, baby, drill,” since the legislative and administrative branches would have been united in opposition to any controls whatever.

    On the question of the EIA projection, I must ask, if the 17% is US policy, then why was it not included in the projection? It would seem to me that you really can’t have it both ways: if the EIA projections are solid, then the policy isn’t–and vice versa. One might also be inclined to ask, what Chinese policies are excluded from consideration in the EIA work? My own (perhaps tediously oft-expressed) perception is that the EIA analysts are systematically biassed toward BAU (I mean that in a technical, non-pejorative sense: they have a consistent history of underestimating adoption rates of renewables.) Out to 2040, that certainly undermines the value of their projections.

    But fundamentally, the problem I’m having with your comments is that the main result of the US adopting your point of view would be the complete failure of any comprehensive multilateral climate treaty process for the foreseeable future. Developing nations need to come on board, as we’ve known all along, and as the case of China drastically illustrates; but denying any historical responsibility on the part nations that ‘came first’ in terms of using up the carbon budget is not the way to accomplish that. The steps that brought us close to the brink are not properly understood as ‘harmless.’

    Adopting your pose of ‘harmlessness’ would be a massive repudiation of basically everything done toward a climate change agreement so far. Total collapse of the Framework Convention would probably be unavoidable. Being firm with emitting nations is one thing: being ridiculously cavalier about one’s own actions and their consequences is quite another–particularly when the claims to emissions ‘virtue’ are still so flimsy.

    And it is hypocritical. As pointed out above, China is investing more money in the transformation of her economy toward a more sustainable than anyone else (and has a smaller economy than the US, to boot.) We agree that Chinese emissions need to reverse course. But just what level of commitment do you think reasonable in that regard? And if only the ‘bottom line’ matters, not the cost to China in terms of development and poverty, then given that the good accrues to everybody (should emissions actually drop), then why should only China be liable for the costs?

    If she is, then why should not the same logic apply to Canada? Or any other country for which emissions are not being controlled–like, say, Mexico? (See the EIA projections for Mexican emissions to see a drastic increase.)

  42. 92
    Walter Pearce says:

    “Until climate change became dangerous, emissions were not a problem for legal liability for the damage that climate is now causing. It’s nearly a tautology so I don’t see why you’d have a problem with that.”

    We know you don’t (or won’t) see. As long as you refuse to come to grips with the cumulative nature of the problem, you’ll be confused about everything from impacts to liability.

  43. 93
    Chris Dudley says:

    Walter (#92),

    Read that again. It says if you don’t get into an auto accident, there is nothing to sue about. Prior to any climate damage, there is no case. The statement is concerning the way law works. You are misreading it.

  44. 94
    Hank Roberts says:

    CD, you’ve taken over the topic to promote a legal argument that assumes your belief. Please, get a blog to argue with what’s known. Paste your own belief into a search engine, at least, e.g.

    Your argument assumes nature’s capacity to absorb excess CO2 has been rather precisely claimed and used (with no overshoot) so there’s no responsibility for the early owners, nothing left for latecomers, therefore anything latecomers try to take hurts everyone.

    Recognize that argument? That’s Malthus:

    A man who is born into a world already possessed … has no claim of right to the smallest portion …. At nature’s mighty feast there is no vacant cover for him.

    The opening post of this topic warns about the consequences of what’s actually been done here. We’ve used up the world’s capacity to handle climate change, and overshot by half:

    About half of the emissions from these anthropogenic activities have remained in the atmosphere ….

    and, while total emissions are increasing, the proportion absorbed by photosynthesis and stored on land and in the oceans is declining (Le Quere et al., 2009)

    Your assumptions are wrong. Do like this guy, get a blog to proclaim your ideas. Filling this topic just blocks discussion we need to have about the science.

    Grumble. Also you damn kids get offa my, er, xeriscape. No further argument on politics here from me, I’ll just read about the science.

  45. 95
    Chris Dudley says:

    Kevin (#91),

    Nice post. First, the EPA endangerment finding was a result of a court order owing to a law suit brought by some states, cities, a territory and some NGOs. It does not really matter who is President, the EPA has to bring about cuts. A nation of laws, etc….

    The EIA method can seem frustrating. They do market analysis and don’t include non-promulgated regulations. It is actually helpful since when the regulations are promulgated, you can figure out how effective they are. They are also a bit clueless about cost curves for renewables and get adoption rates wrong pretty often. They know oil and gas very well however. If there is low cost fracking potential in China, they are all over that.

    Non-participation of the US and China in Kyoto has been a problem for the Framework Convention for a while but there has been pretty good attainment from that protocol for participating nations. Canada is rogue and Australia is in an embarrassing situation, but the compliance period worked for quite a lot of Annex I countries. Bilateral efforts such as between the US and China may be beneficial to the Convention. In my view, Kyoto was an attempt to do Montreal without skin cancers having actually risen. If the US Senate had been successful in its attempt to get China involved, we’d be much farther along. But, now we can hold China harmful, and use other leverage beyond the Framework Convention owing to our emissions cuts.

    And, I don’t recall developed nations ever crying mea culpa at COPs. They have said the problem is large and some undeveloped nation may need help with clean development. Undeveloped nations have taken that line, but it is not the basis of the Convention. It’s been about “common but differentiated responsibilities” rather than liability. AR5 may make introduction of liability inevitable but I doubt RCP2.6 can wait for working that out. GATT is available however to use now. In terms of carbon budget, we’ve got a cushion of 270 GtC left under RCP2.6. AR5 seems to make any budget above that tied to high adaptation costs. So, that is about all the budget there is and growing Chinese emissions can’t fit within it. They have to shrink.

    Regarding what China buys in the renewable market, they are growing their energy sector by leaps and bounds. It is unsurprising that they would be a big purchaser. But they are not growing their energy sector in a way that cuts emissions, which they certainly could just as we are replacing our energy sector in a way that cuts emissions. Our expense is necessarily larger since we have to pay twice for our energy sector and they could avoid that extra expense. I don’t see the grounds for a claim of hypocrisy. We are cutting emissions, they are not.

    I see RCP2.6 as reasonable in that it fairly consistent with the goals of . I think that under the Framework Convention alone, the best we might hope for would be RCP4.5 which looks very expensive on the adaptation/morbidity/mortality front in light of AR5 and causes too much species extinction. Because of this, I think we need other tools to turn China around and soon. And, as noted, some get renewable cost curves wrong, and China is very definitely mistaken that it must slavishly follow our development history. Clean development is very likely much more prosperous for China than its current trajectory. Under GATT, as soon as China cuts emissions, we would have no basis for tariffs and might have to fund Framework Convention clean development assistance in some other way. Making the World Bank Presidency rotating with Chinese participation might be an interesting approach. Did you know Jim Yong Kim was born in South Korea? He is highly competent, but might his appointment not also be a kind of hint towards China?

    Owing to NAFTA, I don’t think the US can impose tariffs on Canadian goods. I think a number of European nations could and the EU as a whole might be able to as well. Same goes for Mexico. That situation turns out to be slightly anti-Monroe Doctrine though tariffs don’t really count in that.

  46. 96
    DIOGENES says:

    Chris Dudley #89,

    “I’ve also said the science says that if you stop greenhouse gas emissions, the warming stops, so past greenhouse gas emissions are not the reason for future greenhouse warming, future greenhouse gas emissions are.”

    I know you have made that statement, but as I’ve pointed out on more than one occasion, it’s not correct. And, if you’ve read any of my past postings, you know I have a short fuse for misinformation/disinformation. You are starting your argument with misinformation; how can it possibly result in anything but an erroneous conclusion? The problem we have today is if we stop greenhouse gas emissions from fossil fuel use today, the warming increases. If we’re lucky, the temperature will rise to a modest peak, and then start a slow decline. If we’re not lucky, the increasing temperature will trigger more carbon feedbacks, and the temperature could continue to increase to????? Most of the emissions cessation studies don’t include these major carbon feedbacks, so we don’t know what will happen during this short interim period. Read Hansen’s Plos One article for the concerns. Additionally, if we stop fossil fuel use today, even if there were no pulse, we have initiated carbon emissions from the Permafrost and other sources, and they would continue until ?????

    This issue of the heritage of past emissions is major, and constrains us strongly if we were to make a serious global effort to solve the problem. That’s why a number of responsible scientists have suggested the possibility of geo-engineering, in addition to other climate change amelioration measures. Not that most of them like geo-engineering, but there may be no practical alternative if we wanted to reduce emissions on a short-time scale, and were concerned about the short temperature pulse going beyond any recommended limit.

    Yes, it would be wonderful if China and all nations reduced their future emissions rapidly. But, we are first among nations responsible for the CO2 ‘time-bomb’ that exists in the atmosphere today, and we are responsible for taking the lead role to de-fuse it IF POSSIBLE. We committed the initial misdemeanor; we are obligated to pay the penalty, as in any other misdemeanor.

  47. 97

    Chris Dudley wrote in 89:

    I’ve also said the science says that if you stop greenhouse gas emissions, the warming stops, so past greenhouse gas emissions are not the reason for future greenhouse warming, future greenhouse gas emissions are.

    It has been estimated that if we were to put 5,000 Gigatons of carbon into the atmosphere in this century perhaps as much as 30% will still be left in 10,000 years, resulting in the world being more than 3°C warmer than it would otherwise be at that time — even if our emissions fell to and remained at 0 for next 99 centuries.

    Please see:

    Archer, David, and Victor Brovkin. “The millennial atmospheric lifetime of anthropogenic CO2.” Climatic Change 90.3 (2008): 283-297.
    Open Access:

    As such, over any period of time that might normally be of interest to us, what matters isn’t the rate of emissions but total cumulative emissions.

    Please see:

    Zickfeld, Kirsten, et al. “Setting cumulative emissions targets to reduce the risk of dangerous climate change.” Proceedings of the National Academy of Sciences 106.38 (2009): 16129-16134.
    Open Access:

    Zickfeld (2009) states, “We show that to stabilize global mean temperature increase at 2 °C above preindustrial levels with a probability of at least 0.66, cumulative CO2 emissions from 2000 to 2500 must not exceed a median estimate of 590 petagrams of carbon (PgC) (range, 200 to 950 PgC)… Furthermore, these estimates of cumulative CO2 emissions, compatible with a specified temperature stabilization target, are independent of the path taken to stabilization.”

    With regard to future temperatures, past and future emissions carry equal weight.

  48. 98
    Chris Dudley says:

    DIOGENES (#96),

    Fortunately, I’m patient with people who are confused on this issue. So, Gavin gave you two links. I think perhaps if you understood that I am speaking of stopping emissions all at once, just as Gavin’s links explore, you would understand my statement better. It is a statement about the way the climate responds to a step function elimination of greenhouse gas emissions. That leads to cooling and the end of feedbacks. It is not a technically feasible scenario (except that we have still not destroyed remaining smallpox strains) but it does tell us something important about how the climate works: inertia is a misleading concept. Future warming is owing to emissions that have not yet occurred. The new Hansen paper does not address this, and probably could not reliably do so owing to the Green’s Function approach used there. You’d end up assuming your result.
    You can find a representative concentration profile there though in fig. 4 B. Also, by comparing figs. 8 B and 9 B, you can see that temperature tracks forcing quite tightly in time. So, lingering warming is not a big aspect of that model.

    If you read a recent study that did include permafrost by MacDougal et al. you’ll see that that feedback needs to be driven by ongoing greenhouse gas emissions. That has consequences for RCP2.6 but not for just cutting to zero all at once.

    Hope that clears it up.

  49. 99
    Chris Dudley says:

    Timothy (#97),

    That final warming depends on cumulative emissions is well know. It is a result of equilibration between the oceans and atmospheric carbon dioxide levels. But we can certainly construct emissions profiles that get warmer than the final temperature and then cool to it, or we can construct profiles that asymptotically approach the final temperature from below.

    If we cut off emissions today, we would have the former kind of profile and would cool to the final temperature. We would need more emission to get more warming. And, there are some intermediate profiles that would produce cooling some from the present warmth. That is the aim of So, what I wrote is correct. The atmosphere is presently well out of equilibrium with the oceans so our choices about future emissions can produce cooling or warming from the present temperature.

    Your statement as it pertains to the final temperature that [“w]ith regard to future temperatures, past and future emissions carry equal weight,” can only be true if past emissions equal future emission. Since we are at a choice point, I hope we don’t choose that.

  50. 100

    Chris Dudley (98) responds to Diogenes (96):

    So, Gavin gave you two links. I think perhaps if you understood that I am speaking of stopping emissions all at once, just as Gavin’s links explore, you would understand my statement better.

    I assume you are referring to:

    2.3 Geophysical commitment

    A warming commitment can be defined from a purely geophysical perspective, as the warming that would result from a complete cessation of anthropogenic emissions. Such a thought experiment has value in terms of showing the timescales of the climate system without implicit entanglements with socio-economic assumptions.

    Hare, Bill, and Malte Meinshausen. “How much warming are we committed to and how much can be avoided?.” Climatic Change 75.1-2 (2006): 111-149.

    In the caption to figure 1 they state that in their model the “zero emissions” assumes that the emissions immediately falls to zero in 2005. They also state that the temperatures initially rise due to “ceased cooling by aerosols.” To simplify matters, earlier you assumed that we could leave aerosols out of the picture, in which case, according to their analysis, temperatures would immediately begin to fall with concentrations.

    But how realistic is this result of theirs? They state that their 2006 analysis uses a “simple climate model” by the name of MAGICC 4.1.

    Now, setting aside the effects of aerosols as you would have us do, what would happen if we were to immediately cease greenhouse gas emissions according to a more realistic climate model?

    I did a little digging and found the following:

    We used version 2.8 of the UVic ESCM, an intermediate complexity coupled climate-carbon model with spatial resolution of 1.8 degrees latitude by 3.6 degrees longitude. The ocean is a 19-layer general circulation model, driven by specified wind stress at the surface and coupled to a dynamic-thermodynamic sea-ice model.

    Matthews, H. Damon, and Ken Caldeira. “Stabilizing climate requires near‐zero emissions.” Geophysical research letters 35.4 (2008).

    In their “3. Results and Discussion” they state:

    The results shown here differ importantly from previous zero-emissions commitment analyses [e.g. Friedlingstein and Solomon, 2005], which have neglected the heat capacity of the deep ocean, and have therefore concluded that after emissions are stopped, global temperatures would decrease in response to declining atmospheric CO2 concentrations…

    … our results suggest that if emissions were eliminated entirely, radiative forcing from atmospheric CO2 would decrease at a rate closely matched by declining ocean heat uptake, with the result that while future warming commitment may be negligible, atmospheric temperatures may not decrease appreciably for at least 500 years.


    Thus as they state in their introduction, “… fossil fuel CO2 emissions may produce climate change that is effectively irreversible on human time scales.”

    These are essentially the same results as what I found in:

    Archer, David, and Victor Brovkin. “The millennial atmospheric lifetime of anthropogenic CO2.” Climatic Change 90.3 (2008): 283-297.
    Open Access:

    The results of Matthews and Caldeira (2008) are made use of by:

    Solomon, Susan, et al. “Irreversible climate change due to carbon dioxide emissions.” Proceedings of the national academy of sciences 106.6 (2009): 1704-1709.
    Open Access:

    … and the paper I previously referred to:

    Zickfeld, Kirsten, et al. “Setting cumulative emissions targets to reduce the risk of dangerous climate change.” Proceedings of the National Academy of Sciences 106.38 (2009): 16129-16134.
    Open Access:

    Now in response to my comment 97 where I brought up Archer (2008) and Zickfeld (2009), you respond (99):

    That final warming depends on cumulative emissions is well known. It is a result of equilibration between the oceans and atmospheric carbon dioxide levels.

    … then immediately backtrack with:

    But we can certainly construct emissions profiles that get warmer than the final temperature and then cool to it…

    This is contradicted by:

    Matthews, H. Damon, and Ken Caldeira. “Stabilizing climate requires near‐zero emissions.” Geophysical research letters 35.4 (2008).

    Archer, David, and Victor Brovkin. “The millennial atmospheric lifetime of anthropogenic CO2.” Climatic Change 90.3 (2008): 283-297.

    Zickfeld, Kirsten, et al. “Setting cumulative emissions targets to reduce the risk of dangerous climate change.” Proceedings of the National Academy of Sciences 106.38 (2009): 16129-16134.

    Solomon, Susan, et al. “Irreversible climate change due to carbon dioxide emissions.” Proceedings of the national academy of sciences 106.6 (2009): 1704-1709.

    Even if emissions immediately fall to zero, barring attempts to artificially increase the rate at which CO2 is removed from the atmosphere (e.g.,, the warming that has taken place is essentially irreversible on human time scales. As such, with regard to future temperatures, equal units of past and future emissions carry equal weight. Effectively (per Matthews and Caldeira), even when the rate of emissions go to zero, what determines future temperatures for the foreseeable future are total cumulative emissions, and as such, a kilogram of CO2 emitted a century ago contributes to future warming just as much as a kilogram of CO2 emitted today or five decades from now.