Max Planck Institute Director: “Low Probability” CO2 Reductions Will Have Impact On Climate Next 20 Years!

Jochem Marotzke, Director of Germany’s Max Planck Institute for Meteorology (MPIM), says we would have to wait 20 years before seeing any impact on climate from CO2 reductions, based on model simulations. Climate variability prevails…

Reduction of CO2 emissions possibly would have no effect on climate over the coming 20 years

(German text translated/edited by P Gosselin)

Jochem Marotzke, director of Germany’s Max Planck Institute for Meteorology (MPIM), wondered whether CO2 savings could really have a direct influence on the temperature in the near future. In a new paper (Marotzke 2018), the Hamburg-based climate researcher simulates the temperature profile of the 2030s predicted by climate models and uses once again a conventional emission profile (Scenario RCP 4.5), and once a politically reduced emission scenario.

Conclusion: Most likely, there would probably be no difference as natural climate variability prevails over these time scales. The paper was published in WIRE’s Climate Change and can be downloaded free of charge as a pdf:

Quantifying the irreducible uncertainty in near‐term climate projections
If the Paris agreement at the Conference of Parties 21 is implemented very effectively, greenhouse‐gas emissions might decrease after year 2020. Whether this would lead to identifiable near‐term responses in “iconic” climate quantities of wide scientific and public interest is unclear, because the climate response would be obscured by quasi‐random internal variability. I define the climate response as an increase or decrease in a linear climate trend over the period 2021–2035, compared to 2006–2020, and establish the probability of such a trend change being caused by an assumed policy shift toward emissions reductions after 2020. I quantify the irreducible uncertainty in projecting such a trend change through very large (100‐member) ensembles of the state‐of‐the‐art climate model MPI‐ESM‐LR. Trends in global‐mean surface temperature (GMST) are higher over the period 2021–2035 than over 2006–2020 in one‐third of all realizations in the mitigation scenario RCP2.6, interpreted as implementing the Paris agreement, compared to around one‐half in the no‐mitigation scenario RCP4.5. Mitigation is sufficient to cause a GMST trend reduction with a probability of 0.40 and necessary with a probability of 0.33. Trend increases in Arctic September sea‐ice area and the Atlantic meridional overturning circulation are caused by the emissions reductions with a probability of only around 0.1. By contrast, emissions reductions are necessary for a trend decrease in upper‐ocean heat content with a probability of over one‐half. Some iconic climate quantities might thus by year 2035 exhibit an identifiable response to a successful Paris agreement but sometimes with low probability, creating a substantial communication challenge.”

In the conclusion, there are some even clearer statements. Marotzke warns that even painful efforts to reduce CO2 in the next two decades could have little impact on the climate:

My thought experiment demonstrates that it is crucial to have realistic expectations of the efficacy of climate policy in the near‐term: Even if greenhouse‐gas emissions begin to decline after year 2020, the probability is substantial that the response of iconic climate quantities to this decline will not have emerged by year 2035.”

Science communication challenge

With 90% probability, the Arctic Sea Ice (SIA) and the Gulf Stream (AMOC) will not respond to changes in CO2 emissions in the 2030s. Marotzke already sees a great communication challenge for the scientists, similar to the unexpected hiatus of recent years.

The major advance brought about by my analysis lies in the ability to quantify the degree of irreducible uncertainty about whether the assumed emissions reduction will cause the desired climate response over a given timescale. The probability of this response occurring depends on the quantity in question but also on the type of causation; for the time horizon out to 2035 the probability lies here in the range between a bit under 0.1 for causation both sufficient and necessary for SIA and AMOC and a bit above one‐half for necessary causation for ocean heat content.

Communicating these probabilities will be nontrivial but will be aided by the precise definitions and meanings underlying them (Hannart et al., 2016; Pearl, 2000). The communication challenge (Deser et al., 2012) furthermore supports the notion that the recent hiatus was not a distraction to the scientific community (Lewandowsky, Risbey, & Oreskes, 2016) but instead provided an opportunity to communicate the role of internal variability (Fyfe et al., 2016) to an audience that might otherwise be disinclined to engage in this discourse.”

The climate sciences continue to navigate in difficult waters. The natural variability causes them huge problems because it has been neglected in the models.

Alarmist dreams

Marotzke still dreams that nature only produces noise (“quasi-random internal variability”). However, the day will surely come when he will also acknowledge the systematic effect of natural climate factors such as ocean cycles and solar activity fluctuations. Perhaps he should start to take an interest in paleoclimatology, which is leaving him in the dust…

18 responses to “Max Planck Institute Director: “Low Probability” CO2 Reductions Will Have Impact On Climate Next 20 Years!”

  1. Reasonable Skeptic

    Climate is based on a 30 year period of average weather. It is hard to change the climate by doing anything in 20 years.

    We could stop all CO2 emissions from humanity and it would be hard to notice a difference. Humanity represents under 10% of all CO2 emissions of course.

  2. Bitter&twisted

    Another admission that CO2 is far from being a driver of climate😁👍

  3. SebastianH

    Came back just to make sure my favorite skeptics haven’t changed a bit. You do not disappoint 😉

    P.S.: do you expect the car to stop instantly once you took your foot of the accelerator?

    1. Robert Folkerts

      It would be silly of us to expect any kind of change from you, wouldn’t it Seb ?

      1. Yonason


        Pay no attention to the malicious troll. Everything he/she/it/whatever supports is evil. Listen to this assessment of Dr. Lindzen from the beginning to 36:38

        There can be no doubt whatever that anyone siding with the Left against humanity is at best confused, at worst one of the most horrible beings on the planet.

        The whole video is worth watching.

    2. Kurt in Switzerland

      There is scant chance of a detectable change in the long-term slope of the Keelung Curve as a result of UN initiatives, let alone a measurable effect on climate. But ‘Climate Guilt’ money will flow to the UN and be deftly distributed to the open palms of ‘Climate Victims’ (until the citizens of W Democracies decide to put a stop to the charade).

      So what’s your benefit as a practitioner of this Malthusian scam, Seb?

    3. Robert Folkerts

      Does Seb think co2 has inertia as in his car/accelerator analogy?

  4. Skeptik

    I suspect that most climate scientists would actually agree with Jochem Marotzke that stopping human CO2 emissions would not have much effect on our current climate for very many years. What they probably would claim is that such a cessation would stop any FURTHER changes.

    1. Yonason

      Making no attempt to alter CO2 emissions should also have no measurable effect, at all, ever.

      There will be no “FURTHER” changes, because there cannot be.

      CO2 is completely innocent.

  5. J. Seifert

    As I understand, reducing global CO2 emissions will have the same temperature increase trend as not reducing global CO2 emissions…for the next 20 years. What is then the temperature trend for the next 20 years? Envisioned, since AR3, was a temp increase of 0.2 C per decade, thus 0.4 C higher for the two decades 2000-2020, using the best computer models.

  6. Don from OZ

    Your quite right about one thing Seb H we haven’t changed our minds. Why would we? when all the literature and evidence proves us right. It’s past time for you to man up and accept fair reason. You will be accepted if you do.

  7. Walter Schneider

    Even if CO2’s influences on changes in temperature trends could be measured accurately enough that it can be determined that reductions in atmospheric CO2 content are responsible for falling temperatures or for reductions in the rates of temperature increases, why would anyone expect that the reporting of the consequences of the reductions accurately reflects what will be measured? After all, the reporting of falling trends is hardly visible in the trends that are being reported now. Why would the reporting be any less biased in the future?

    See “Evaluating The Integrity Of Official Climate Records”
    By Tony Heller, DDP, July 9, 2016

  8. John F. Hultquist

    Was he paid for this?

    Say all carbon-based fuel was abandoned January 1st. Earth’s systems will continue to use about 2 ppm per year. If we are now at, say 412, in 20 years (2039) we would be down to 372. The atmosphere would not notice.
    Pay me.

  9. Yonason


    Dr. Lindzen on the “narrative” of “global warming.”

    The first point is made from there until time = 6:54. And it only gets better from there.

    A masterpiece of debunking. Many gems scattered throughout, just free for the taking.

  10. Reasonable Skeptic

    “P.S.: do you expect the car to stop instantly once you took your foot of the accelerator?”

    I quite agree. That is why I am not worried about climate change.

    Climate is like a glacier. It changes very slowly. Observations show no change yet in anything out side of a bit of additional warming.

  11. tom0mason

    Getting some perspective …

    As temperature effects of CO2 on the atmosphere can not be adequately quantified (unless you know CO2’s climate sensitivity), so ignoring any supposed temperature effects of CO2 –try this thought experiment.

    List all the ‘pros’ and ‘cons’ about today’s temperature rising by 2°C and CO2 levels at 700ppm.
    List all the ‘pros’ and ‘cons’ about today’s temperature falling by 2°C and CO2 levels up 700ppm.
    List all the ‘pros’ and ‘cons’ about today’s temperature rising by 2°C and CO2 levels at 350ppm.
    List all the ‘pros’ and ‘cons’ about today’s temperature falling by 2°C and CO2 levels at 350ppm.

    Rational people would conclude that even if the temperatures are hotter or cooler than now, CO2 levels higher than now would always be beneficial to us and nature.

  12. Weekly Climate and Energy News Roundup #341 | Watts Up With That?
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