“Unequivocal”: New IPCC Report Released

August 9, 2021

In the past, about the strongest statement that Intergovernmental Panel on Climate Change updates would make is that the planet had “unequivocally” warmed.
Now that is the word they are using to link human influence to the warming.

Summary for Policy Makers here.


Observed increases in well-mixed greenhouse gas (GHG) concentrations since around 1750 are unequivocally caused by human activities.

The likely range of total human-caused global surface temperature increase from 1850–1900 to 2010–201911 is 0.8°C to 1.3°C, with a best estimate of 1.07°C.

Globally averaged precipitation over land has likely increased since 1950, with a faster rate of increase since the 1980s (medium confidence).

Human influence is very likely the main driver of the global retreat of glaciers since the 1990s and the decrease in Arctic sea ice area between 1979–1988 and 2010–2019 (about 40% in September and about 10% in March). There has been no significant trend in Antarctic sea ice area from 1979 to 2020 due to regionally opposing trends and large internal variability.

It is virtually certain that the global upper ocean (0–700 m) has warmed since the 1970s and extremely likely that human influence is the main driver. It is virtually certain that human-caused CO2 emissions are the main driver of current global acidification of the surface open ocean. There is high confidence that oxygen levels have dropped in many upper ocean regions since the mid-20th century, and medium confidence that human influence contributed to this drop.

Global mean sea level increased by 0.20 [0.15 to 0.25] m between 1901 and 2018. The average rate of sea level rise was 1.3 [0.6 to 2.1] mm yr–1 between 1901 and 1971, increasing to 1.9 [0.8 to 2.9] mm yr–1 between 1971 and 2006, and further increasing to 3.7 [3.2 to 4.2] mm yr–1 between 2006 and 2018 (high confidence). Human influence was very likely the main driver of these increases since at least 1971.

31 Responses to ““Unequivocal”: New IPCC Report Released”

  1. jimbills Says:

    Still looking over the news coverage, and frankly I probably won’t read the entire report, but I’m getting the sneaking feeling the IPCC is minimizing tipping points and positive feedbacks again, and is therefore conservative once more on future predictions of temperature and climate change effects.

    An overall message of this report seems to be, though, that more action towards mitigation is much better then less action, or that serious attempts to lower emissions no matter where we are is always worthwhile – and I’d definitely agree with that.

    • dumboldguy Says:

      I too got the feeling that they were minimizing things again. I guess we won’t hear definitive statements until the impacts are in nearly EVERYONE’S backyard.

      A new acronym possibility there? INEBY?

      • jimbills Says:

        That’s pretty much what will happen. One could say, it’s INEBYtable. It’s happening now – we have had a recent spate of wildfires, flooding, etc., and this new report is going to the causes of it.

        In their defense, scientists are extremely shy about making anything close to a definitive statement until they are 100% positive about it. It’s part of the process. It’s a shame, though, because the public takes lukewarm statements as excuses to delay action.

    • jimbills Says:

      For the record, I don’t make grammar/spelling error notes to my posts unless the error changes the actual meaning of the post. I send half my comments from a phone, which auto-corrects often incorrectly, and I don’t always catch the mistakes. It is annoying, though.

  2. Roger Walker Says:


    “But the policymakers, or at least their aides, should make the effort to read the whole report. Incredibly, the stark summary is still a relatively conservative assessment of the consequences we might face if global warming does exceed 1.5C.The report is a comprehensive review of the published evidence painstakingly compiled by hundreds of authors and reviewers over the past two and a half years. The summary of the report was approved line by line by governments, including the US, Australia and Saudi Arabia, during long and intensive discussions last week in South Korea. It is written in matter-of-fact language, but it omits some of the biggest risks of climate change, which are described in the full text. For instance, the summary indicates that warming of 2C would have very damaging impacts on many parts of the world. But it does not mention the potential for human populations to migrate and be displaced as a result, leading to the possibility of war.This is a risk that many governments around the world have already recognised, with climate change often highlighted in national security assessments as a “threat multiplier”, which could increase the chances of political instability and conflict.”

    I’m struck by the fact that that everyone seems to be missing the point. Likely future temperatures will not be caused by future emissions but by the 400ppm of CO2e already present in the atmosphere. That’s what is behind the serious climate disruption we’re already seeing: drought, floods, wild fires and extraordinarily high temperatures – large swathes of the planet are on the way to becoming literally unliveable. All that from a mere 1.1°C. And we ain’t seen nothing yet. The full effect of that level of atmospheric CO2 is still working its way through the system. The monstrous flywheel that is System Earth is still accelerating. We could cease all CO2 emissions tomorrow and that would still be true. I cannot believe that “they” haven’t twigged that, so I have to conclude that there is a tacit agreement not to mention the fucking elephant in the room.

    • grindupbaker Says:

      When I heard Mike Mann say it and later read Stefan Rahmstorf write it on RealClimate Web Log I inferred they must mean that the ocean will maintain its duty and drop CO2 at ~1.6 ppmv / year from the 417 ppmv or wherever Chinese + Yanks + others decide to stop it, because there’s no other possible reason to think that there isn’t another +1.23 degrees to play out over 100 years or so (global heater + human pollution all gone) with CO2 = 417 ppmv, so pretending it’s only +0.3 degrees rather than the +1.23 degrees that it is with CO2 = 417 ppmv would be just daft. The scientists must be thinking that ocean uptake will save much Life & disaster on Earth over the coming couple centuries.

    • rhymeswithgoalie Says:

      But the policymakers, or at least their aides, should make the effort to read the whole report.

      They’re more likely to read their poll numbers. If their stance doesn’t matter to their electorate, it’s no big deal.

      Remember that this information has really been out there a long time.

    • Gingerbaker Says:

      “Likely future temperatures will not be caused by future emissions but by the 400ppm of CO2e already present in the atmosphere. … We could cease all CO2 emissions tomorrow and that would still be true. ”

      It’s not quite that bad. The Earth’s carbon sinks remove about 21.7 billion tons of CO2 from the atmosphere every year. If we could cut our total emissions merely in half, atmospheric CO2 would be decreasing every year.

      • ecoquant Says:

        The Earth’s carbon sinks remove about 21.7 billion tons of CO2 from the atmosphere every year.

        Actually, no. That is incorrect and a misunderstanding, confusing gas in equilibrium with sequestration.

        Yes, 60% of our CO2 emissions go into oceans and soils, leaving 40% in atmosphere long term. In oceans they become carbonic acid and dissolved carbonates, increasing ocean acidity.

        However, this storage is temporary, and this was kindly pointed out to me by Dr Glen Peters when I was working through CO2 drawdown costs. In particular, say you want to take out 1 ppm of CO2 from atmosphere by some means, whether Direct Air Capture or reforestation. So you do, and you find that you managed to take out 0.4 ppm, but 0.6 ppm showed up in atmosphere. Where from? From the soils and oceans which are in gaseous equilibrium with atmosphere. So, in order to actually draw down atmosphere by a full 1 ppm, you actually need to withdraw 2.5 ppm, in other words, the other 60% (or 1.5 ppm) that went into soils and oceans plus the 1 ppm that was in atmosphere.

        Now this process is a little laggy. A burst of CO2 takes a while to fully get into soils and oceans, on the order of a decade. Similarly, if 2.5 ppm were drawn down from atmosphere it would take a while for the CO2 to come out of soils and oceans (easier from soils), but in a decade or two it’s all accounted for.

        This is why emitting CO2 in any form (e.g., CH4 which degrades into CO2) is such a bad idea.

        If we were to suddenly stop emitting everything, what would happen is that after four centuries or so, half of the extra CO2 in atmosphere we’ve put there since the 19th would indeed come out and be sequestered by chemistry, but the other half would remain for thousands of years.

        Solomon, Susan, Gian-Kasper Plattner, Reto Knutti, and Pierre Friedlingstein. “Irreversible climate change due to carbon dioxide emissions.” Proceedings of the national academy of sciences 106, no. 6 (2009): 1704-1709.

        Matthews, H. Damon, and Susan Solomon. “Irreversible does not mean unavoidable.” Science 340, no. 6131 (2013): 438-439.

        Archer, David, Michael Eby, Victor Brovkin, Andy Ridgwell, Long Cao, Uwe Mikolajewicz, Ken Caldeira et al. “Atmospheric lifetime of fossil fuel carbon dioxide.” Annual review of earth and planetary sciences 37 (2009): 117-134.

        There’s another wrinkle to all this. Suppose we do draw down CO2 after ceasing all emissions. We’ll stop things from getting worse. But planet won’t cool. Why? Thermal inertia of oceans, with water being a huge thermal sink. Most of the heating we are experiencing is something like 10%-15% of the total. The rest is going into the oceans. Like gases, thermal energy is in equilibrium, too. So if you cool off atmosphere, more thermal energy comes out of oceans.


        Eby, M., K. Zickfeld, A. Montenegro, D. Archer, K. J. Meissner, and A. J. Weaver. “Lifetime of anthropogenic climate change: millennial time scales of potential CO2 and surface temperature perturbations.” Journal of climate 22, no. 10 (2009): 2501-2511.

        The message is if people don’t want to experience this warming trap, don’t put the CO2 in atmosphere in the first place.

        • Gingerbaker Says:

          So, you are saying this graphic from the EPA is incorrect?:


          • ecoquant Says:

            No it’s not incorrect, it just needs a proper interpretation. That is a Sankey diagram of where the flows go. It implies nothing about their being bound up in the places they go. Indeed, if the interface between atmosphere and another reservoir is examined, whether soils or oceans, there’s a constant exchange of, say, CO2 back and forth across it.

            One needs to read and understand the accompanying legend:

            Figure 2. Schematic representation of the overall perturbation of the global carbon cycle caused by anthropogenic activities, averaged globally for the decade 2010–2019. See legends for the corresponding arrows and units. The uncertainty in the atmospheric CO2 growth rate is very small (±0.02 GtC yr−1) and is neglected for the figure. The anthropogenic perturbation occurs on top of an active carbon cycle, with fluxes and stocks represented in the background and taken from Ciais et al. (2013) for all numbers, with the ocean gross fluxes updated to 90 GtC yr−1 to account for the increase in atmospheric CO2 since publication, and except for the carbon stocks in coasts which is from a literature review of coastal marine sediments (Price and Warren, 2016). Cement carbonation sink of 0.2 GtC yr−1 is included in EFOS.

            Fluxes are not the same as stocks. The latter are bound up. The former are volatile.

            Eventually, after about 10,000 years, CO2 as HCO3 or other formers can get trapped as carbonates in the sea floor and buried. But it is very slow. it cannot keep up with the rate of human emissions. And that’s why it’s like pouring water into a bathtub faster than the drain can handle it. Same thing with trees and soils. (Rhetorical) question: Why does the Keeling curve have a sawtooth profile on top of an ever increasing trend? That’s because the downslope is the northern temperate forest Spring, where forests grow leaves and bloom. They peak, and then as Autumn arrives they give back all that Carbon to the atmosphere.

            It turns out forests can sequester Carbon in soils for long periods, with the aid of mychorhyzzial fungi. (The Carbon in wood, as it turns out, except for very long-lived big trees, is stored there temporarily.) But it takes a long time and the forests that do it well are old a century and a half. Young forests may temporarily store Carbon as wood, but most young trees die and fall over, and give it back through decay. We, as a population, actively discourage creation of old forests with big trees by inhibiting them burning near where our houses are. Wildfires occur when too much young dead trees accumulate, and something sparks them. The natural mode is more frequent and smaller fires.

            In principle we can extract CO2 directly, but we really don’t know how to do the engineering yet and because CO2 is so hard to grab onto and there’s relatively so little of it in atmosphere, it’s very expensive to do. Current costs are estimated as north of US$500 per tonne CO2. They hope to improve this to US$80 or US$100 per tonne. But the price tag for making a dent — assuming emissions have stopped — is a hundred trillion dollars at those cheaper rates, assuming we know how to build this. I’d say you really can’t go home again. It’s foolish to entertain these options without being honest with people about the price tag.

          • ecoquant Says:

            BTW, that legend came from the Figure 2 of the Friedlingstein, et al article that was cited as the source.

          • Gingerbaker Says:

            Thank you for the excellent reply. I stand corrected and chastened. 🙂

          • ecoquant Says:

            You are welcome. No need to be “chastened”, however.

        • rhymeswithgoalie Says:

          Humans suck at understanding lag times and buffering and chemical equilibrium. FF disinformation specialists know to take advantage of that.

        • Gingerbaker Says:

          And thanks for the detailed reply! 🙂

      • jimbills Says:

        Under all the updated scenarios in AR6, the global temp rises to at least 1.5 C above pre-industrial by 2050. That’s even with the immediate, massive action scenario (which won’t happen, realistically – we don’t have the political will for it), because of the in-built warning from prior emissions. The difference between the scenarios in the report is what happens after that – how much do we emit and for how long.

        The old worst case scenario in AR5 was discarded in this recent report – it isn’t going to happen – even the limited responses we’re doing now would prevent that high of a man-made carbon release.

  3. indy222 Says:

    Well, congratulations to the IPCC; if they’re now saying “unequivocal” to human causation, they’ve advanced themselves to 1988 and James Hansen’s actual climate science. Hooray. Or HooHah. Just 33 more years to go, and the worst science is in the past 8 years of publications.
    We’ll be in a “Book of Eli” situation by the time the IPCC is dragged kicking and screaming to the point of admitting we’re in a situation we really need to deal with immediately.

    • rhymeswithgoalie Says:

      I often point out that it’s the Intergovernmental Panel on Climate Change. Scientists are conservative enough. Throw in panel members chosen by politicians and it’s slower still.

  4. jimbills Says:

    Here’s a very long review of the report, and the best I’ve seen so far, on the recent report:

    It’ll take me a while to read it all.

    It should be noted that this is the last comprehensive IPCC report we’re likely to see until the end of this decade.

  5. pendantry Says:

    Typo alert:
    Your first and second bullet points are identical. I’m beginning to think you need to replace your proofreader.

  6. ecoquant Says:

    The news coverage from the financial media, with the possible exception of The Financial Times, is putting this report like in 8th place.

    While we await WG2 and WG3 reported, the media could be doing everyone a service and emphasizing that solutions to all these problems are in hand, and the obstacles are vested interests and people’s collective fussiness about changing how they live their lives.

    • pendantry Says:

      solutions to all these problems are in hand

      I must be missing something here. That is most definitely not a message that we need to be telling anyone at this point.

      • ecoquant Says:

        Sorry @pendantry, that’s too politically manipulative for me. I’m not out to try to nudge people into “doing the right thing” by scaring them.

        I want to set out the choices. There are ways to fix it. Not clear what it means if people don’t opt for them but, then, they are making their own beds. Is it that they don’t understand? Probably not.

        Per Botkin’s book Discordant Harmonies people collectively have some deep assumptions about how “Nature” works and the human relationships with It, many of them wrong. That we are collectively disrupting the cozy world we’ve lived in for 5000+ years through our own actions seems to be too much for many people to accept. Trouble is, we’re disrupting it quickly, so there’s not a lot of time for people to get used to the idea, even if it’s been shouted at them for 50 years. I think scientists thought people and politicians were more rational than they are.

        BTW, Botkin’s book is pretty good, and I’m going to write a review of it in the next month or two at Goodreads. It have some strong disagreements with it. These derive, I fear, from Botkin and others failing to fully understand the maths behind the theoretical models they criticize, namely, the Lotka-Volterra systems. He doesn’t exhibit a basic understanding of differential equations. That said, many of his other observations are quite good.

        • pendantry Says:

          … too politically manipulative…

          No political manipulation intended. I’m just stating a plain fact. Anyone who is claiming at this late stage of the game that ‘there are solutions in hand’ is the one being ‘politically manipulative’.

        • indy222 Says:

          I think this, while having some truth, misses the key and fatal point…. All such amplifying feedback complex dynamical systems ultimate collapse. We are on that path as well, in the very short term. Techno-optimism is another addiction. The very nature of the success of the human species is exactly why we will very likely fail. The relentless urge for growth is how we came to dominate the planet; it’s been bred into our DNA and psychological motivations. But when you’re as clever and successful and relentless as H. Sapiens, that is fatal. We go at the speed of light – and then hit the wall. The wall of a finite planet and total disregard for the ecosystems which support us physically, emotionally, spiritually, and motivationally when it comes down to the end. We’re the economic-addicted rats hitting the dopamine bar over and over until exhaustion. We won’t solve our problems within the Economic paradigm we’ve thrown our souls into. We’re the bacteria in the Petri dish who refuse to see the glass wall ahead, falsely believing that innovation after innovation will save us. But it won’t. Study the discoveries of why the biological scaling laws apply also to cities, civilization in general, and where it leads. Each have finite-time singularities built in, and only put off and amplify the ultimate “final” price we will all pay. We climb higher and higher into the trees for the high hanging fruit, more and more complex networks of support, patting ourselves on the back for our cleverness and “We’re #!!” to all the other species – conveniently ignoring where the ultimate eon for decades – look at the progress of CO2 in the atmosphere for 30 years of IPCC reports. It’s an unbroken string of broken delusional promises. While technology is necessary in any imagined solution, it’s pointless and only makes the final payment worse when it is not wedded to a deep fundamental change in the very genetic makeup of humans. I see no prospect for that, aside from some sort of CRISPr miracle, and even that is likely to be grabbed onto by the political powers to turn H. Sapiens into good little workers who don’t complain, instead of making us actually evolved to stop growth and live on a finite planet.

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