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Why global emissions must peak by 2020

Filed under: — stefan @ 2 June 2017

(by Stefan Rahmstorf and Anders Levermann)

In the landmark Paris Climate Agreement, the world’s nations have committed to “holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels”. This goal is deemed necessary to avoid incalculable risks to humanity, and it is feasible – but realistically only if global emissions peak by the year 2020 at the latest.

Let us first address the importance of remaining well below 2°C of global warming, and as close to 1.5°C as possible. The World Meteorological Organization climate report[i] for the past year has highlighted that global temperature and sea levels keep rising, reaching record highs once again in 2016. Global sea ice cover reached a record low, and mountain glaciers and the huge ice sheets in Greenland and Antarctica are on a trajectory of accelerating mass loss. More and more people are suffering from increasing and often unprecedented extreme weather events[ii], both in terms of casualties and financial losses. This is the situation after about 1°C global warming since the late 19th Century.

Not only will these impacts get progressively worse as warming continues, but our planet also runs a growing risk of crossing critical tipping points where major and largely irreversible changes to the Earthsystem are triggered (see Fig. 1).

Fig. 1 Tipping elements in the Earth system, in relation to past global temperature evolution since the last Ice Age 20,000 years ago as well as future warming scenarios[iii]. The Paris range of 1.5 – 2 °C warming is shown in grey; the bars show increasing risk of crossing tipping points from yellow to red.

The West Antarctic Ice Sheet (WAIS in Fig. 1) has likely already been destabilised, committing the world to at least three meters of global sea-level rise in coming centuries[iv] – an outcome that scientists have warned about since the 1970s[v]. The Greenland Ice Sheet – holding enough ice to eventually raise global sea levels by seven meters – may likewise be destabilised below 2°C[vi]. Coral reefs have suffered pan-tropical mass bleaching in 2016 and are doing so again in 2017 as a result of warming oceans, and only if global temperature stays well below 2°C some remnants of the world’s coral reefs can be saved[vii]. The Gulf Stream system (THC in Fig. 1) appears to be already slowing[viii] and recent research indicates it is far more unstable than previously thought.

Because overall global temperature rise depends on cumulative global CO2 emissions, the Paris temperature range can be translated, with some uncertainty, into a budget of CO2emissions that are still permissible. This is the overall budget for the century and it lies within the range of 150 to 1050 Gt of CO2, based on updated numbers from IPCC[ix]. At the current global emission level of 39 GtCO2 per year, the lower limit of this range would be crossed in less than four years and is thus already unachievable without massive application of largely unproven and speculative carbon dioxide removal technologies. Even the CO2 budget corresponding to the mid-point of this uncertainty range, 600 GtCO2, is equivalent to only 15 years of current emissions. Fig. 2 illustrates three scenarios with this budget and different peaking years for global emissions. It makes clear that even if we peak in 2020 reducing emissions to zero within twenty years will be required. By assuming a more optimistic budget of 800 Gt this can be stretched to thirty years, but at a significant risk of exceeding 2°C warming.

It is still possible therefore to meet the Paris temperature goals if emissions peak by 2020 at the latest, and there are signs to show we are moving in that direction as global CO2 emissions have not increased for the past three years. We will need an enormous amount of action and scaled up ambition to harness the current momentum in order to travel down the decarbonisation curve at the necessary pace; the window to do that is still open[x].

In summary, declining carbon emissions after 2020 is a necessity for meeting the Paris temperature limit of “well below 2 degrees”.

Fig. 2 Three illustrative scenarios for spending the same budget of 600 Gt CO2, with emissions peaking in 2016 (green), 2020 (blue) and 2025 (red), and an alternative with 800 Gt (dashed).

Note: This article first appeared in the report 2020 The Climate Turning Point


[i] World Meteorological Organisation. WMO Statement on the State of the Global Climate in 2016 (WMO, Geneva, 2017).

[ii] World Meteorological Organisation. Weather extremes in a changing climate: hindsight on foresight (WMO, Geneva, 2011).

[iii] Schellnhuber, H. J., Rahmstorf, S. & Winkelmann, R. Why the right climate target was agreed in Paris. Nature Climate Change 6, 649-653 (2016). doi:10.1038/nclimate3013

[iv] Feldmann, J. & Levermann, A. Collapse of the West Antarctic Ice Sheet after local destabilization of the Amundsen Basin. Proc Natl Acad Sci U S A 112, 14191-6 (2015). doi:10.1073/pnas.1512482112

[v] Mercer, J. West Antarctic ice sheet and CO2 greenhouse effect: a threat of disaster. Nature 271, 321-325 (1978).

[vi] Robinson, A., Calov, R. & Ganopolski, A. Multistability and critical thresholds of the Greenland ice sheet. Nature Climate Change 2, 429-432 (2012). doi:10.1038/nclimate1449

[vii] Frieler, K. et al. Limiting global warming to 2 degrees C is unlikely to save most coral reefs. Nature Climate Change 3, 165-170 (2013). doi:Doi 10.1038/Nclimate1674

[viii] Rahmstorf, S. et al. Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation. Nature Climate Change 5, 475-480 (2015). doi:10.1038/nclimate2554

[ix] Peters, G. How much carbon dioxide can we emit?  (2017)

[x] A Roadmap for Rapid Decarbonization. Science, March 24, 2017: Johan Rockström, Owen Gaffney, Joeri Rogelj, Malte Meinshausen, Neboja Nakicenovic, Hans Joachim Schellnhuber

210 Responses to “Why global emissions must peak by 2020”

  1. 51
    Thomas says:

    re 48 Russell — Wilhelm Reich asked, “Why do the masses allow themselves to be politically swindled?”

    Great question hey? The answers are already out there. Across cognitive science know-how and modern 21st century psychology.

    A key point to note imo. The article ends up yet again only talking about Trump. It totally ignores the collective cultural norms and social framing and entrenched beliefs of Americans in general … the soil from which Trump and everyone else grows up in …. and fails to compare these norms with elsewhere, such as Europe or China or India.

    The US is a psychological gold fish bowl in which the bulk of the rest of the world does not swim. Trump’s but a minor symptom – he is not the disease.

  2. 52
    Soccer Dad says:

    Sorry to post this here, I couldn’t find how to contact you.

    Here are two blog posts from a climate denier (not the blog’s main purpose). I have not the knowledge to counter them. Is he right or not? And why?

  3. 53
    Marco says:

    Arun @49: who told you that myth? Not that Ray Ladbury is much on the money. We know very few facts about suicide among farmers in India, and you can find the answer you want to hear by shopping among the many different potential sources.

    Scientific studies at best suggest that “cash crops” are a main factor (i.e., growing crops to make money, not to feed oneself), combined with many farmers in India being “marginal”. That is, they have too little land to actually make sufficient money to survive bad years, and can’t even use “modern” farming techniques.

  4. 54
    Richard says:

    The work of Friedrich et al. late last year gives good evidence that ECS is NOT going to be the +3C which best describes the past few million years. ECS may be constant when only CO2 and water vapor are considered, but not when non-GHG indirect forcings are includes, like loss of Arctic ice. It makes perfect sense that ECS will be higher in the new regime. Given the fact that CO2 will continue to rise even as we taper off our own emissions, then 560ppm looks quite likely, and if ECS =4.9C as Friedrich et al 2016 say, then it sounds like forced into dramatic GeoEngineering immediately, I don’t mean in 30 years perfecting artificial trees, I mean immediately – like as in stratospheric aerosol continual injection, just to halt further melt while we struggle to pull ourselves together.

  5. 55

    tegiri nenashi-san wa bakayaro des’ 44: The opposition to dirt cheap energy here is strong

    BPL: Not at all. We just don’t think it’s realistic to assume fusion energy will come along in quantity just when we need it. The problem is more that your opposition to accepting reality is strong.

  6. 56
    tegiri nenashi says:

    #50 Dennis,

    Yes, faith is the right word. My faith, though, is in collective creativeness of humanity, not just single narrow field. If fusion were still delayed, there would be plenty of other developments. Sure you can criticize this vague intuition, but obvious history lesson is that civilization progress is exponential. Any futuristic predictions of a process which embeds exponential factor in it is futile.

    Now, this phenomenon of “emerging artifacts” is interesting by itself, and it appears that there, is no compelling science explaining it. Biology of a cell is a prime example: it is incredible how fine tuned and elaborate organism development is. One can trace the steps of this machinery, but can’t avoid feeling that there is great mystery that still waits to be revealed.

    The fundamentals of opposite process — degradation, destruction, death — is much better understood. It is the law of increasing entropy. Therefore, you vision of doom and gloom is on much better scientific footing — I can concede this point.

    However, science is not a foundation of American society. Faith is. A faithful (not to confuse with religious) person is somebody with positive attitude. That american smile might look like a fake, but if you pretend something for long, you might end up acquiring that trait. Returning back to climate debate (yes there is still one) — to sell your stuff to american public you have to make it positive.

  7. 57
    Donald Condliffe says:

    I find it surprising that eminent scientists would think that it is even remotely feasible to have CO2 emissions peak by 2020 and sharply decline thereafter. The idea does not square with reasonable projections of oil, natural gas and coal production. In particular the US EIA has historically produced reasonably accurate estimates of future energy production and consumption. The emission curves shown in Fig 2 above contrast sharply with US EIA production estimates found in Table A2. World total energy consumption by region and fuel, Reference case, 2011–40 The US EIA estimated future consumption of liquids and natural gas give annual rates of increase of 1.1 and 1.9 percent through 2040 and coal production also increases, albeit more slowly at 0.6 percent per year. The idea that emissions will drop as they say must happen looks like wishful thinking.

  8. 58
  9. 59

    baka 56: Returning back to climate debate (yes there is still one)

    BPL: Not among competent people, there isn’t.

  10. 60
    Mal Adapted says:

    Lee Leeman:

    We already know how to do contraception, so … what’s the problem?

    The problem is that during the past 50 years, the global average number of births per woman declined from 5.1 to 2.4 while atmospheric CO2 rose from 320ppm to 405ppm.

  11. 61
    Mal Adapted says:


    Scientific studies at best suggest that “cash crops” are a main factor (i.e., growing crops to make money, not to feed oneself), combined with many farmers in India being “marginal”. That is, they have too little land to actually make sufficient money to survive bad years, and can’t even use “modern” farming techniques.

    Yes, and the first farmers to be forced out by AGW are the “marginal” ones; they have too little margin to withstand ‘bad years’ because their land is already at the margins of productivity determined by previously-stable climatic norms. The farmers who are a few decades from the margin moving toward them under AGW, OTOH, already have more resources to buy their way north.

  12. 62
    Mal Adapted says:

    Never Mind:

    to sell your stuff to american public you have to make it positive.

    I think I see your problem. There may be some of us here trying to ‘sell stuff’ to [definite article?] american public, but then there’s physics, which the rest of us are here to talk (mostly) about; physics doesn’t go away if you stop being positive.

    How about you? What are you trying to sell here, and to whom?

  13. 63
    Dan H, says:

    Soccer Dad,

    All the data posted is real.

    Realclimate did a nice job on the Marcott data a few years ago.

    The Liu modelled temperature data is presented in this paper, comparing it to the Marcott paper.

    The Monnin CO2 data can be seen here:

    I do not have the Kobashi paper handy, but it looks reasonable. I have not seen that analysis of the Paris agreement, but it is not too surprising.

  14. 64
    t marvell says:

    It is irrelevant that CO2 emissions might be leveling off. The CO2 levels in the atmosphere are continuing to increase at the same pace.
    The emissions data are uncertain; better to look at CO2 levels.
    A key issue here is the lag between CO2 increases and temperature increases. I keep on asking how long this is, without an answer. I can find nothing in the literature. Eyeballing CO2 trends and temperature trends suggests that the lag is about 20 years. I did some crude regression analysis and got about that time lag. It takes a long time for CO2 and temperature to reach an equilibrium – CO2 emissions versus CO2 sinks.
    If the lag is 20 years, then it is probably impossible to limit the temperature increase to 2 degrees.
    The Paris accord looks like a fig leaf.

  15. 65
    Russ Doty says:

    Thanks for lending urgency to seeking action. We are again attempting to get an 80% by 2050 initiative on Montana’s 2018 ballot. We realize it is not enough, but we’re in coal country and we have to move the needle as far as we can above the current 15% non-hydro renewables, given the need to educate and draw votes statewide. See Any help you can give will be appreciated.

  16. 66
    Aksel says:

    Rahmstorf’s graphs are far too passive to the population. Instead of understanding the bloody seriousness of the problem, the population is lulled asleep in a false belief that science says that the climate can be saved and then continues with business as usual.

    The graphs do not show the enormous extent of the problem. What we need is an operationalization, a plan, that shows the scary prospects and consequences of such a drastic reduction. Fortunately, the population has become more aware of the climate, but unfortunately, they still believe the problem is solved by marginal efforts.

  17. 67
    Soccer Dad says:

    Dan H,
    Thanks a lot!

  18. 68

    « The West Antarctic Ice Sheet has likely already been destabilised, committing the world to at least three meters of global sea-level rise in coming centuries – an outcome that scientists have warned about since the 1970s. »
    Some scientists warned. But most of them kept playing the risk down. And here we have the authors falling in the same trap again: They succumb to the temptation of avoiding the blame that comes over the conveyor of bad news. Instead of delivering the real climate message, which is: «Emissions must decline sharply now and go to zero in nearly no time at all!», there comes the much more comforting: «We can wait another couple of years or so, before emissions peak.»
    In the same field: Its been known for ages that emissions will eventually have to be zero. Yet it’s taken the IPCC forever to make that clear. Why? Same psychological trap.

  19. 69
    Will Denayer says:

    I’m not a climate scientist, but I understand a couple of things about macroeconomics and I can tell you this and with absolute certitude, although some of you will not want to hear it and won’t listen anyway: if you believe that carbon pricing and carbon markets are a solution, you are flatly wrong. It suffices to look at the complete and utter failure of the European Trading System (ETS) to see this. Carbon pricing might well work in the fantasy world of neoclassical economics, but it does not work and it will never work in the real work. The sooner we destroy this illusion the better. See for example here:

  20. 70
    Charlie says:

    At the moment the planet is on track for 3-4°C warming. The Paris commitments of every single country =>

  21. 71
    jai mitchell says:

    We are already witnessing (and reported in the peer review by the way) shifts toward collapse of the boreal forest, amazon rainforest and rapid permafrost destabilization. In addition, the recent link between SE Asian aerosol reductions and shifts to a +IPO show that the ENSO is also past a trigger point (this is also supported in the current peer review).

    Therefore you should have not relied on your rosy, self-censoring paris-paper graphic to pretend that these things are not already happening. you are suffering from a decidely poor lack of imagination of what is humanly possible. Please do not mince words and self-censor anymore. We are in a global climate emergency RIGHT NOW. and we need our best scientists to say so, even if they don’t yet understand what forces can be mobilized to transform our economic system once the climate emergency is realized.

  22. 72
    jai mitchell says:

    Follow up, the temperature models in the graphic also assume summer arctic sea ice lasting through 2050 without the impacts of decreased albedo and subsequent warming (and further impact to boreal forests and permafrost) that this regional warming will incur.

  23. 73
    Russell says:

    It isn’t just Trump Thoms — Copenhagen set the global stage for his rejecting the Paris gonfaloonery

  24. 74

    After we get rid of the current [president], we can start on a concentrated program of…getting rid of all the other anti-science folks in Congress.

    Well, there’s really no reason to wait. We could well see a climate-friendly House after the 2018 midterms even as is, and if “we”–a goodly number of “wes” anyway–get off our butts and work, that chance can be raised significantly.

  25. 75

    #45, TN–

    For the record, there is nothing there powered by wind and solar.

    Well, other than the water filling the dam, of course.

  26. 76

    Several folks have asked, essentially, “Why would anyone think we can get to net zero in such a time frame?”

    Well, I sure don’t think it’s going to be easy, or even that it will necessarily happen. But I do think it’s possible–mostly because the inability to deal with non-linear change which has so often led to underestimates of the rates of clinmate change effects also leads to underestimates of potential rates of social/technological change.

    IOW, tipping points happen, but not all of them are bad.

    I think one that is now pretty much a given is the triumph of renewables. Calling them ‘wimpy’ is pretty silly now; it will look a good deal more so long before Mr. Trump leaves office.

    I’ve previously posted the first ReThinkX paper, which anticipates a quick non-linear disruption of transportation, which would lead to a gutting the petroleum industry in pretty short order, and a precipitous drop of transportation-related emissions. I’m not trying to “sell” this as a certainty, nor am I an acolyte of this concept. But nor has anyone so far provided me with a reasoned analysis of why it can’t or won’t happen. Here’s the link:

    Some here have argued that changes to agricultural practice can have a hugely disproportionate effect in reducing emissions. The numbers I’ve seen seem to indicate that this is a possibility–although I must say that I’m skeptical about how fast such changes could scale. Instruction isn’t cheap or quick, in general, not when the student body is radically dispersed across the planet. Still, with widespread connectivity–now a reality–effective practices can ‘go viral’. So maybe you can’t rule this one out.

    Again, not saying I think a happy ending is at all a given. But I think change can come–and may come–a lot faster than many would believe.

  27. 77
    Tony Mac says:

    I have watching this problem, mainly through the British weekly “New Scientist” since it was first mentioned 40 + years ago.
    It always has been underestimated, it always turns out to be much worse than predicted. I do blame scientists, for leaving out vital trigger points etc. from their models, for being too careful and afraid to man-up and tell it as they really see it for fear of rejection by their peers.
    Not the few, Hansen, Man et al but the many.

  28. 78

    WD 69: if you believe that carbon pricing and carbon markets are a solution, you are flatly wrong.

    BPL: So something taxed is NOT produced in smaller quantity? You can produce the same amount even if your cost of production goes up and demand stays the same? Wowsers!

  29. 79
    Digby Scorgie says:

    t marvell @64

    There is an article at about the lag between CO2 level and temperature. The author estimates 30 years, but as you’ll see from the comments, there’s a lot of argument about this. Also, I remember reading some years ago that James Hansen puts the lag at 25 to 50 years.

    The problem, of course, is that the CO2 level doesn’t stabilize at some value, followed later by the temperature stabilizing at a corresponding value — the CO2 level just carries on rising. Damn!

  30. 80
    Phil Scadden says:

    Will – lots of reasons ETS not working in Europe. Hardly a model scheme and not even remotely equivalent to a pigovian tax. What measure would you suggest to get emissions down? Anything that uses the market as a driver or do you advocate direct regulation?

  31. 81
    nigelj says:

    Soccer Dad @52, regarding your first link showing conflicts between CO2, temperature expectations and temperature realities in the holocene, refer below

    This paper suggests the reconstructed temperatures may be wrong. It’s very difficult accurately reconstructing temperatures so far back over medium scale time scales. Marcott is short to medium term in terms of geological time scales.

    If you look at the really large picture going back very, very long term there is a correlation between CO2 and temperature. This is the main thing to be aware of.

    Basically climate sceptics zero in on some discrepancy over some particular period, and say “climate science is a fraud” as opposed to asking why there may be a discrepancy. There’s no point trying to counter this type of rubbish, you are talking to irrational, emotive anti climate science zealots with all sorts of agendas. If you want to respond, it will need to be for the benefit of other people reading who have more open minds.

    The sharp up-tick in both CO2 and temperature post 2000 is so striking and obvious this correlation is different, and simply screams out for attention. Of course we have causation as well.

  32. 82
    Mal Adapted says:

    Will Denayer (srsly?):

    I understand a couple of things about macroeconomics and I can tell you this and with absolute certitude

    If you understood as much about macroeconomics as you thought you did, you wouldn’t tell anyone anything with absolute certitude.

  33. 83
    nigelj says:

    Will deneyer @69, just remember carbon pricing and carbon markets are different things.

    I agree carbon markets as in cap and trade or emissions trading all looks dubious, and I agree it has a poor track record in Europe. There are many reasons, partly so many exemptions have been made to industries, that it becomes a weak scheme. Some of this has been out of fear that those industries would be disadvantaged by competitors in Europe or elsewhere. Carbon markets are also very complicated and complexity brings its own problems. I agree its a fantasy of neoclassical or neoliberal economics. However such schemes are better than nothing.

    However carbon pricing has validity obviously, as it is just a calculated and agreed value on carbon, and can form part of carbon tax schemes. Such schemes seem more workable to me than cap and trade, and are being tried in various countries, just do a google search. Tax schemes can also be designed to reduce impact on industries relating to the competition problem.

  34. 84
    Thomas says:

    Another bug-bear of mine.

    But scientists are defining “pre-industrial” or “natural” climate in different ways. Some work from the beginning of global temperature records in the late 19th century, while others use climate model simulations that exclude human influences over a more recent period.

    One recent study suggested that the best baseline might be 1720-1800.

    These different definitions make it harder to synthesise the results from individual studies, which is vital to informing decision-making.

    When confusion reigns supreme, nothing happens because no one can decide as unnecessary debates ensue over what is or isn’t.

    Added to this general confusion of what is or isn’t “pre-industrial” is the way every nation uses different methodologies and starting years for their GHG reductions as their Paris Goals.

    That too is intentional for when everyone can compare apples with apples and the original box they come is the same box then everyone can see the truth more clearly.

    Which is the last thing the G20 and 40 OECD nations want because their national self-interest is paramount over everything else – how to sell their ‘grandiose’ plans for action and still get reelected next time round.

  35. 85
    Thomas says:

    78 BPL:
    Stick to astrophysics.

    82 Mal Adapted: Yes. Economics is not science and definitely not Physics.

    Noting of course that the man was not claiming any certitude about macroeconomics. His certitude was specifically about one thing:

    “Carbon pricing might well work in the fantasy world of (Neoliberal) Neoclassical Economics, but it does not work and it will never work in the real world. The sooner we destroy this illusion the better.”

    His certitude about the illusion ( I prefer Self-Delusion ) is justified on the data, the evidence, the math, intelligent analysis and a science based reality.

    Beware the straw man. He burns away to nothing really fast. :-)

  36. 86
    Thomas says:

    77 Tony Mac says:

    “I do blame scientists, for leaving out vital trigger points etc. from their models, for being too careful and afraid to man-up and tell it as they really see it for fear of rejection by their peers (masters, benefactors, political blow back, and public/media attacks).”

    I’m in general agreement there.

  37. 87
    Will Denayer says:

    Well, let’s not assume my fundamental ignorance, this brings us nowhere, read Boehm’s article instead – he gives ten reasons why carbon markets cannot work and some more can be easily found (the most important one has already been mentioned in the comments). The failure of the ETS is not due to its complexity but to the fact that parts of it have been written up – literally – by the cement and the steel industry and other lobbies which united in some bigger lobby with the sole intention of turning the ETS into a subsidy scheme for their industries. As people tend to say – why trust me, indeed? – Google it.
    Carbon pricing is indeed different, but it is complex and the point is that much better, much less inefficient policies are possible – and absolutely necessary – if we are ever dreaming about making a difference, but these policies require changing and re-scaling the macroeconomic architecture and it cannot be done without “government,” it is to say without satan according to the neo-classicists. It is for the full 100% a political question. It has always been.

  38. 88

    Th 85: Stick to astrophysics.

    BPL: Bite me. I was a philosophy minor at Pitt and have designed formal logic tutorials. I don’t need lessons in logic from someone who is as hazy on the subject as you are.

  39. 89

    It is time to move on. The hockey sticky controversy, “The Inconvenient Truth” and polar bears floating on ice bergs are old news. Finally, rational thinking and climate science facts are overshadowing the thirty-year false narrative of climate change alarmists. Developments over the last two years have significantly changed the climate science narrative.

    1. U.S. House Committee on Science, Space & Technology, February 2,2016: John Christy, Distinguished Professor of Atmospheric Science and Director of the Earth System Science Center at the University of Alabama in Huntsville, testified that out of 102 simulations of global temperature from 32 climate models, only the Russian model was close to actual temperatures but still too high. All other models greatly overestimated temperatures. The Russian model included the influence of predicted global cooling related to reduced sunspot activity but was still too high. Numerical analyses of actual data clearly indicate a decreasing rate of increase of the trend line of the global mean surface temperature that could become negative in the next decade. http:\\ atmospheric/people/faculty/tom-bjorklund/

    2. Nature website, February 24, 2016: “There is this mismatch between what the climate models are producing and what the observations are showing,” says lead author John Fyfe, a climate modeller at the Canadian Centre for Climate Modelling and, Analysis in Victoria, British Columbia. “We can’t ignore it.”

    3. Caltech: The next 125 years, November 2016: President Rosenbaum at Caltech posited that nature cannot be modeled with classical physics but theoretically might be modeled with quantum physics ( Climate models are entirely driven by classical physics. Quantum physics modeling technology is not yet developed and may never be developed adequately to model earth processes.

    4. Cerncourier website, November 11, 2016: “Early this year, CLOUD reported in Nature the discovery that aerosol particles can form in the atmosphere purely from organic vapours produced naturally by the biosphere). In a separate modelling paper published recently in PNAS, CLOUD shows that such pure biogenic nucleation was the dominant source of particles in the pristine pre-industrial atmosphere. By raising the baseline aerosol state, this process significantly reduces the estimated aerosol radiative forcing from anthropogenic activities and, in turn, reduces modelled climate sensitivities. This is a huge step for atmospheric science,” says lead-author Ken Carslaw of the University of Leeds, UK. “It’s vital that we build climate models on experimental measurements and sound understanding, otherwise we cannot rely on them to predict the future. Eventually, when these processes get implemented in climate models, we will have much more confidence in aerosol effects on climate. Already, results from CLOUD suggest that estimates of high climate sensitivity may have to be revised downwards.” (CERN is the European Organization for Nuclear Research.)

    5. On a much shorter time frame, my analysis of the HadCRUT4 time-temperature data supports the long-term predictions from the CERN studies. The data indicate a high likelihood of the beginning of a decline in the global mean surface temperature trend line within the next decade. The first derivative of the temperature trend line has been positive for the past 20 years but has decreased in value each month for the past 20 years. The derivative is likely to become negative in the mid-2020s and increase in negative slope well into the 2030s, i.e., the mean global surface temperature will decline.

    The implications from these recent developments are that CO2 does not play a significant role in global warming, climate models used by the United Nations Intergovernmental Panel on Climate Change (IPCC) to estimate future temperatures are too high, and the models should be redone.

    Climate science is far from settled. Solving the climate change conundrum before the world wastes 100 trillion dollars running in the wrong direction is the major problem for climate science. Ill-advised environmental regulations must be rolled back before they destroy the U.S. economy. A rational environmental protection program and a vibrant economy can co-exist. The Paris Climate Agreement is nothing more than a millstone on the world’s economy and windfall profits for connected politicians and alternative energy ventures that are not ready for prime time. It is time for the U.S. to get out of the Paris Agreement.


    On June 1,2017, the American Geophysical Union published an editorial on their website,, regarding the U.S. withdrawal from the Paris Climate Agreement and its implications and solicited comments. The message of the editorial is that “Policies may change, but the science does not” and Trump’s withdrawal from the Paris Treaty was a huge mistake. The authors assert that the AGU continues to standby its 2003 position statement “Human-Induced Climate Change Requires Urgent Action.” The premise is “that basic science shows that climate change has already occurred, is human-induced, due to the buildup of greenhouse gases in the atmosphere, and is well understood.” The editorial ends with an appeal for honest and open communication of scientific evidence to the public and policy makers.

    I disagreed with the AGU premise and submitted a comment that included some of the references to recent climate science advancements discussed above, which was published. Brent Lofgren, NOAA Physical Scientist, disagreed with me on one issue and replied with a well-considered analysis. I submitted a follow-up response, and the AGU editor of the website rejected the comment and banned me from the website. With the hope of creating a teachable moment, Lofgren’s comment and a draft of my rejected comment are reproduced below.

    Brent Lofgren’s (NOAA, Physical Scientist) reply to Tom Bjorklund’s comment: Spectroscopy of atoms and molecules has its theoretical underpinnings in quantum mechanics, and this forms the basis for the definition of greenhouse gases. Although the QM is not explicitly modeled (doing this at the level of a climate model would be absurdly expensive) (emphasis added), it is parameterized in the routines for radiative transfer, emission, and absorption, which lie at the root cause of not only GHG-caused climate change, but also the natural state of climate. To say that climate models are based only on Newtonian physics is false.

    Tom Bjorklund’s (Research Scientist, University of Houston) draft reply to Brent Lofgren: Thank you for your comments on parameterizing aspects of quantum mechanics in GCMs, but I did not write that climate models are based only on Newtonian physics. I stated that the framework for the Paris Treaty has been constructed from the results of Newtonian physics, which is a true statement. The fundamental unanswered questions can be simply stated. (1) Do the GCMs parameterize aerosol production based on the CERN CLOUD study, and (2) are GCM predictions still widely divergent?

    My reply to Lofgren was not accepted by the EOS website editor. I am banned from further commenting on the website. I requested an explanation for the ban from the editor of the website but have not yet received a response. Is this reaction from a special interest group an exception, or is it a practice that is endemic to the mass media?

  40. 90
    Thomas says:

    Oooh aaah, I was a Philosophy Minor at Pitt. Well bully for you. You want a medal? :-) Barton Paul Levenson where you obtain your needed lessons in logic is of no concern to me. Just get them.

    A few months studying these papers couldn’t hurt either.

  41. 91

    Tom Bjorklund, #89–Points 3-5 are pretty worthless, IMO, since #5 is essentially pure assertion (and pretty vague to boot); #4 is a relatively marginal question hyped as pivotal; while #3 is just hopelessly off topic.

    #1 has already been granted a whole post here, and does not need to be relitigated.

    Which leaves #2. To that, I only have to add the sentence immediately following those quoted by Tom:

    “There is this mismatch between what the climate models are producing and what the observations are showing,” says lead author John Fyfe, a climate modeller at the Canadian Centre for Climate Modelling and Analysis in Victoria, British Columbia. “We can’t ignore it.”

    Fyfe uses the term “slowdown” rather than “hiatus” and stresses that it does not in any way undermine global-warming theory.

    Yet here Tom is, trying to use the result to undermine global-warming theory.

  42. 92

    Th 90: Oooh aaah, I was a Philosophy Minor at Pitt. Well bully for you. You want a medal? :-) Barton Paul Levenson where you obtain your needed lessons in logic is of no concern to me. Just get them.

    BPL: You can’t read, can you?

  43. 93
    Mal Adapted says:

    Will Denayer:

    Carbon pricing is indeed different, but it is complex and the point is that much better, much less inefficient policies are possible – and absolutely necessary – if we are ever dreaming about making a difference, but these policies require changing and re-scaling the macroeconomic architecture and it cannot be done without “government,” it is to say without satan according to the neo-classicists.

    It sounds like you’re linking “government” with “satan”. That suggests a profound hatred of government, Mr. Denayer.

    Setting that aside, though: if you know even a few things about macroeconomics, you’ve heard of the Tragedy of the Commons. The executive summary is that AGW is a predictable output of a market economy that allows everyone to enjoy the benefit of “cheap” energy by externalizing their marginal climate-change costs. The tragedy is that the sound economic choices we make as individuals add up to an immense diseconomy in aggregate; namely, degradation of the global climate commons, which we will all pay for one way or another, although some will pay disproportionately more than others.

    Since AGW is the product of a “free” market’s failure to price fossil energy honestly, it requires collective (i.e. government, practically speaking) intervention in the energy market, to internalize some of the marginal AGW cost of fossil fuels in the price. The preferred intervention is a revenue-neutral carbon tax on production at the source, in the expectation that with the correct carbon price signal, market forces will drive the buildout of carbon-neutral energy supplies and infrastructure with optimum efficiency.

    Did you get that, Mr. Denayer? Yes, a revenue-neutral carbon fee and dividend with border adjustment can’t be put in place without government; it’s not “changing and re-scaling the macroeconomic architecture” however, it’s just a tax. You pay taxes, don’t you? And it’s revenue-neutral, meaning you (on average) won’t pay any more in total taxes with CF&D than without it.

    You surely know, don’t you, that your “changing and re-scaling the macroeconomic architecture” makes you sound like a “CMAGW” (catastrophic mitigation of AGW) alarmist. As for “satan”: if he’s anywhere to be found, it’s in every buyer and seller in the energy market.

  44. 94
    tw2017 says:

    I’m afraid that the basic argument made in this post has proven unpersuasive to Zeke Hausfather:

    “Strongly doubt any of the scenarios are remotely feasible”

    I’m not the only one who is sure that the alarmists made the tactical mistake of placing the 2°C target goal posts way too close, but so is warmist Zeke Hausfather.

    Here’s his reaction to the two German alarmist authors over at Twitter:

    I hate to be the bearer of bad news, but I strongly doubt that any of these scenarios are remotely feasible. 1/2

    — Zeke Hausfather (@hausfath) June 6, 2017

    – See more at:

  45. 95
    Michael says:

    Is the following correct?

    THC = thermohaline circulation
    ENSO = El Niño Southern Oscillation
    Sahel = desertification of a large swath across Africa

    And does loss of coral reefs provide accelerating feedback to overall global warming? All the other tipping points seem to do this, so the inclusion of coral loss stands out and doesn’t seem to fit, at least at first glance.


  46. 96
    Thomas says:

    89 Tom Bjorklund, I find incompetent commentary by ‘scientists’ like yourself as objectionable and insidious the extreme. If you have competent evidence based ideas about GCMs, climate change drivers, ECS, atmospheric physics, cloud formation etc. then a genuine objective scientist would be submitting a detail analysis of their “hypothesis” to a science journal for publication which included detailed references to prior papers you wish to use to support your ideas – rather than crying about being “barred from AGU” and behaving instead like a biased troll on an internet forum.

    Tom Bjorklund: Areas of Expertise: Active Tectonics, Petroleum Geology
    How do you sleep at night and why do you imagine that everyone else on this planet are gullible fools? Your scientific expertise in the area of Climate Change Science is as great as mine is – zero!

    Tom Bjorklund, Write and Submit a Review Paper …. or STFU~?

    It has been known by simple human observations since at least the 1800s that the removal of forests affects cloud formation and rainfall and regional climates. This is not new except that modern day scientific rigour has been now able to pinpoint the chemical and psychical processes involved – as to WHY this is so.

    As such, yet again there is this OBSESSIVE focus on GHG emissions as being the ONLY thing worth talking about when hat is not the case. Human activity includes ALL such activity (especially land use changes globally up to the present day) that has been progressively impacting Climate norms for more than 200 years and in fact cumulatively for thousands of years.

    RE “4. Cerncourier website, November 11, 2016: Ken Carslaw of the University of Leeds, UK” — Cherry-picking and Misdirection writ large. Is it too challenging to provide direct refs to the Papers concerned? Apparently yes!

    To assist others here tear your false beliefs and assertions to pieces:
    Large contribution of natural aerosols to uncertainty in indirect forcing, K. S. Carslaw et al

    Occurrence of pristine aerosol environments on a polluted planet (w Carlaw)
    New approaches to quantifying aerosol influence on the cloud radiative effect (w Carlaw)

    (Ref’d) Ion-induced nucleation of pure biogenic particles — Jasper Kirkby et al

    The role of low-volatility organic compounds in initial particle growth in the atmosphere — Jasmin Tröstl, et al — Subject terms: Atmospheric chemistry, Thermodynamics
    “We present a particle growth model that quantitatively reproduces our measurements. Furthermore, we implement a parameterization of the first steps of growth in a global aerosol model and find that concentrations of atmospheric cloud concentration nuclei can change substantially in response, that is, by up to 50 per cent in comparison with previously assumed growth rate parameterizations.
    Two measurement campaigns at the CERN CLOUD (Cosmics Leaving OUtdoor Droplets) chamber (Methods)

    PLUS in no particular order:
    ref’d CERN article pages 7/8 — CLOUD experiment sharpens climate predictions
    ” The results also show [MAY INDICATE PERHAPS POSSIBLY] that ionisation of the atmosphere by cosmic rays accounts for nearly one-third of all particles formed, although small changes in cosmic rays over the solar cycle do not affect aerosols enough to influence today’s polluted climate significantly.”

    First results from the CLOUD (Cosmics Leaving Outdoor Droplets) experiment show that trace vapours in the atmosphere, which until now had been thought to account for all aerosol formation, actually only explain a minute proportion of atmospheric aerosol production.

    “Interaction between vegetation and the atmosphere in cloud and rain formation in the Amazon: A review” — João Paulo Nardin Tavares Conclusion – In several of the articles read, the authors stated that “Unfortunately, little information is available that would allow a reliable estimate of the contribution of primary biogenic particles to the organic aerosol burden in tropical regions” (Andreae & Crutzen, 1997);[…] The authors therefore recognize that there is insufficient data to state that the forest emits VOCs enough to act as CCNs.

    Atmospheric science: Unexpected player in particle formation

    Present-day measurements yield insights into clouds of the past

    Evidence for climate change in the satellite cloud record Joel R. Norris,

    Clouds get high on climate change – Changes in cloud patterns match predictions from climate simulations of a warming world. Alexandra Witze 11 July 2016

    Climate change: Save last cloud forests in western Andes

    On the roles of sulphuric acid and low-volatility organic vapours in the initial steps of atmospheric new particle formation — P. Paasonen et al.

    Here’s some total bullshit from a bullshit site ref’d by Tom Bjorklund aka MY MODELLING is better than YOUR MODELLING logical fallacy
    Warnings that CO2 was not the controlling climate change factor have been presented for years—and ignored by climate modelers, the media, and the public.

    The equivalent of living inside Disney’s Fantasy Land Castle … imho!

  47. 97
    nigelj says:

    Tom Bjorklund @89

    So essentially John Christie testifies (claims) that there has been “less warming” than climate models predicted.

    I think he is wrong, and we have some huge issues with this guys claims:

    Firstly he relies on just the satellite data and this data has known problems and does not measure the surface. Anyone with any sense and no particular agenda would at the very least take an average of all main data sets.

    Secondly his claims are based on global temperatures that exclude 2016 at the very least. Those temperatures bring surface temperatures in line with the middle range model estimates so his testimony appears out of date. So I wonder why you would even bother to quote them.

    Thirdly he ignores the fact that global temperatures are not expected to increase as a ruler straight line, but have been and will be uneven. He also fails to understand that most heat also goes into the oceans, and this can lead to slow periods of warming over land, but that this is a temporary or cyclical phenomenon.

    Fourthly he is a known sceptic at total odds with the opinion of the majority of his peers. While this does not mean he is automatically wrong by definition, it does mean that his views need scrutiny, and need to be very compelling, and they are manifestly not compelling, as I have shown in points 1 – 3 above.

    So for these reasons his testimony is entirely without meaning, accuracy or value.

  48. 98
    freetoken says:

    This thread comment section… wherein Tom Bjorklund illustrates so well that which biologists have had to deal with over the past century from creationists.

  49. 99

    That Figure 2 is absurd. You lunatics imagine CO2 emissions going to zero between 2035 and 2050.

    Reality will be a little different. CO2 emissions will rise at an accelerating rate thanks to the BRIC countries regardless of what the rest of the world does,

    By 2060 emissions will be at least double compared to 1990. Will the temperature rise by 2 Kelvin or more? It might but given that CO2 is at best a weak driver of temperature a cooling of 2 K is just as likely.

  50. 100
    Hank Roberts says:

    Would someone please build a website for Thomas, since
    he hasn’t managed to build one for himself? He needs
    his own space where people can read him who want to.