Cassandra has moved. Ugo Bardi publishes now on a new site called "The Seneca Effect."

Friday, February 2, 2018

How Big a Disaster Can Climate Change Be?

Above, you can see an image from the paper by Marsicek et al., just appeared on Nature. It shows a reconstruction from pollen records of the temperatures of the past 10,000 year or so, the "Holocene," for North America and Europe. Note the black squares, showing how fast temperatures have been growing during the past 50 years or so.

As all reconstructions of the past, this one has to be taken with some caution, but it fits well with the various "hockey sticks" that research continues to produce despite the attempts to discredit both the science and the scientists who work in this field. So, we can assume these results to be reasonably reliable. Then, we can note a few interesting things.

1. What we call "civilization" arose and continued to exist during a period of relatively constant temperatures, that is, during the past 5000 years or so. During this period, the oscillations in the graph are never more than about half a degree. That's probably not a coincidence. Agriculture and civilization come together and it is unlikely that agriculture could have been developed for wildly oscillating temperatures and rapidly varying climates

2. Civilizations seem to grow and collapse because of internal factors - the fall of empires doesn't seem to be correlated to climate change. For instance, you can look in the graph for the data corresponding to the fall of the Roman Empire, between 2000 and 1500 years ago. Temperatures are flat, at most cooling a little. It is a point that I already made on the basis of another set of data specific for the region occupied by the Roman Empire. These more detailed data show a cooling period in Europe, but after the fall of the Empire. 

3. Some relatively intense oscillations in the curve appear at about 3000 years bp, which corresponds to the collapse of the Late Bronze Age civilization. This might support the interpretation by Eric Cline who sees climate as a concause of the collapse. Maybe, but can a whole civilization collapse abruptly as the result of a temperature change of just a couple of tenths of degrees? Personally, I tend to think the opposite. That is, the modest temperature change of the Late Bronze Age has been triggered by the collapse of the Mediterranean civilization of that time. 

4. Note how some much touted events of the past - for instance the "Medieval Warm Period" - appear as just minor perturbations in the curve. Overall, it seems that the effect of human activity on climate has been marginal until the age of fossil fuels.

5. According to Ruddiman, the relative stability of the past 8000 years or so is the result of the release of greenhouse gases produced by human agriculture. This is the phenomenon which prevented the earth system to return to a new ice age. It is possible, but it seems to me at least unlikely that a system can be stabilized by two opposite strong perturbations (the other one is the effect of the Milankovitch oscillations)

6. There is no obvious correlation of this long term trend with what we know of the Sun's output. There has been a lot of speculation that the past temperature oscillations have been related to variations of the Sun's output -- the "Maunder Minimum" is an example of that. But if these variations have an effect, it is truly minimal. It can only be within the oscillations of the curve which don't exceed a few tenths of degree.

7. The increase in temperatures during the past 50 years or so has been simply stunning. In a sense, these sudden temperature changes are not unusual in the earth's history (the problem for biological species is to survive them). But, in this case, it is so fast that it has probably no equals in the whole geological history of the planet. It is a disaster ongoing. Will civilization survive? Will humankind survive? Will anything alive today survive? Who can say?

But don't worry: we all know that this paper is part of the great conspiracy of the 97% of the world's climate scientists. Fortunately, they have been debunked by a group of brave internet trolls, helped by friendly fossil fuel lobbyists. 

The paper cited here is behind a paywall. If you have no access to it, write to me (ugo.bardi(twiggyingthing) and I'll send you a copy.


  1. "Will civilization survive? Will humankind survive? Will anything alive survive? Who can say?"

    I may be misreading you, but I seem to have "triggered" you by my casual attitude towards climate change. You may post this or not as you wish, if you do not I will consider myself unwelcome and depart.

    Assuming one case of climate change (perhaps the worst), that a release of methane clathrates causes the ice caps to melt, humanity's survival will still depend on how human beings react to the challenge. I've a pretty good background in geology and the geologic record tells us that there has been one hell of a lot of CO2 in the atmosphere in the past and there is a hell of a lot more stored in the earth than is in fossil fuels. Survival will depend on our reaction, not the environment.

    Short version: I do not expect the population level to be sustained in this century without a major hit that will solve the climate change problem.

    I've no doubt that climate change will be a stressor in the future, but, IMO, hardly the greatest that we face. If I am wrong and it indeed is to becomes the major stressor in the near future, the problem will still be how we react to it. But climate change had better hurry as other problems are hurtling towards us with a shorter arrival time.

    another fred

    1. No disagreement, here. Humankind may well survive the climate challenge. Just as it survived the transition from Pleistocene to Holocene. But it will emerge out in a form which will be completely different than what we call "humankind today"

    2. But, as a further note, the stressor generated by the fossil fuel pulse may be as large, or even much larger, than some of the worst cases of the past. Think of the end-Permian extinction - the earth seriously risked sterilization. And think that the sun is brighter today than it was then.....

    3. "I've no doubt that climate change will be a stressor in the future"

      another fred , can you not see climate change as a stressor presently?

      "Short version: I do not expect the population level to be sustained in this century without a major hit that will solve the climate change problem."

      another fred, a 'major hit ' to population may be immaterial as a solution to global warming - the energy imbalance is not directly related to population.

      "If I am wrong and it indeed is to becomes the major stressor in the near future, the problem will still be how we react to it. "

      another fred , have you considered that long term equilibrium is a very long way off and by the time you form the view that earth's energy imbalance is generating a major stressor, it is almost certainly too late to react in any meaningful way and that stratospheric suffering is about as likely to be as effective as any other path..

      "But climate change had better hurry as other problems are hurtling towards us with a shorter arrival time."

      another fred , I find this a very strange sentiment.

      In my view, decimating our ghg footprint is the appropriate and proportional reaction we would have wisely embarked upon at least 10 years ago with a view to completing that phase within this decade. I recognize you disagree. I was calling for a global ban on fossil fuel exploration 10 years ago. Apparently Ireland may be heading for this now.

      "You may post this or not as you wish, if you do not I will consider myself unwelcome and depart."
      My response is not intended to convey that you are unwelcome. (not that I have any say in this)

    4. Another Fred,

      While I disagree with you on several aspects of your comment, I would argue that Ugo was targeting the other anonymous user on the prior post who ranted and raved about heading to an ice age in 13 years or something.

    5. Crybaby, I'm not in opposition to much of what you say, but it is true that other problems are hurtling towards us. It is a race to the death, if you will pardon my choice of words.

      Climate change is the big lumbering slow bake menace. Several other equally deadly and seemingly faster moving issues are strong contenders. Just take the central driver of all these issues, unmanaged human population growth. No matter how much or how little CO2 we release we are rushing towards a probable die-off due to eventual limitations with food. Famines are often massive things because of the width and breadth of how food is produced, distributed and consumed. We have had multiple mega famines over the last few hundred years that killed 10 million to 45 million people each. This at a time when human population was a fraction of what it is today, and there was no global warming to speak of.

      Project this into the future a bit, with eight times the population. Without needing to enlist the help of global warming you have numbers in the 80 million to 360 million range per event. So far that dwarfs any climate change numbers I've seen for the coming decades by orders of magnitude.

      There are a few reasons we stopped seeing such big famines. For example modern transportation. If you can't ship it, they can't eat it. Next of course is fertiliser and pesticides. If anything, anything at all reduces the availability or distribution of those factors and several others, famines come right back.

    6. Yvan, lots to say about population. Short version:

      1. A small subset of population has been entirely responsible for the extreme end of earth energy imbalance.

      2. Much the same subset has had the knowledge and increasingly the means to substantially ameliorate this part of the GW spectrum over the last 30 years.

      4. Because they explicitly decided not to do so, repeatedly and in most of the countries involved, GW is an extreme and imminent threat.

      5. Population per se, did not generate the GW threat and overpopulation has little to do with it .

      So I don't see population as the central driver of GW and the probable die off you refer to is most likely to come from a food limitation related to GW.

      There was a paper released last year (can't find a reference) which assessed the likelihood of a 50% failure of world annual food calories to be a 1 in 10 year event due to GW and climate instability. Historically it was far far less likely.

  2. Ugo, you're getting as cynical as the rest of us :-)

    1. Come on! I am not cynical. As I said before, I think someone will survive.

  3. Trouble is, its a self replicating AI hybrid organism.

  4. I don't think it matters at all whether we see Gore Warming or Global Cooling. Too much time is wasted between the two groups ( "The Seven Sisters pay you to lie" "You're a communist and want One World Government" ). Overpopulation meeting any reduction in food production caused by any abnormal weather means we go over the cliff. No need to speculate on any of that, it has already started and many countries are already being triaged. I wouldn't bother trying to save the rest of humanity by hoping human nature changes ( by somehow nor being selfish )-save you and yours. Food is already in danger ( yes, indeed, we all heard the Chicken Little's in the 70's-but now we're running out of the fuel that is our food ).

  5. Anonymous, where I disagreed with you before, I tend to agree with you here.

    Look everyone, the climate-change train has left the station.

    All the treaties and all the research are the people who are riding in the passenger cars on the train examining the headlong rush toward the canyon.

    "Short version: I do not expect the population level to be sustained in this century without a major hit that will solve the climate change problem."

    I cannot disagree with you here. I have been reading Ehrlich and his ilk for years. Hell, I still have a dog-eared first edition of "The Limits of Growth". No matter where I look, a stable population figure for human population in an environmentally "friendly" civilization appears to be in the 1.5-2.0 billion range for us human critters.

    Right now, the current world population is 7.45 billion.

    Climate change and the corresponding famines and dislocations and wars and epidemics (those pesky damn horseman) will drive us toward the 1.5-2.0 billion mark. The question is "what will be the rate of decay"?

    I don't like it, but Ugo is right about the "Seneca Cliff". The big question to me is the sign of M.

    1. Perhaps I misread your comment - but a major hit on population will not solve the climate change problem. Too many climate-related dominoes now toppling over for population to be considered a "fix". Yeah, we need to rapidly dwindle our numbers anyway - but that's another topic.

  6. Ugo
    Nice to have models that can do past climates accurately but future feedback reactions to the exceptional heat pulse are not going to be easy to model.

    Did I understand correctly by using the reciprocal of the legend on the graph that 2016 was warmer than 99.4% of all years in the last 11000 years in the model simulation?


  7. Due to the lag in effect of Co2 in the atmosphere most of the extreme climate we are experiencing now, and I am not going to list them as they are too many but seemed to have run up a total price tag last year of close to $400 billion, is from Co2 release that occurred prior to "Gore". We have released as much Co2 post "Gore" than all emissions pre "Gore" and the climate extremes are increasing non-linearly. Not to mention all of the detrimental effects on the ocean and its ability to absorb Co2 and still produce food for billions.

    It is almost certain that human habitat will begin to degrade to the point where population net growth reverses in a matter of years and not in a good way.

  8. The massive amounts of mercury just discovered in the melting permafrost may very well affect the survival of humanity in extremely negative ways (and the entire surviving ecosystem) -

    ~Survival Acres~



Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)