Some impacts of warming by 1.5 and 2C

Something I’ve always struggled with when it comes to climate change is understanding the actual impacts of anthropogenic global warming. I think I understand the big picture quite well. If we continue to add greenhouse gases to the atmosphere, we will sustain a planetary energy imbalance, which will cause the climate to warm. This will also intensify the hydrological cycle; there will be more evaporation and precipitation and, in particular, we will see an increase in the frequency and intensity of extreme precipitation events. We will also probably see an increase in the frequency and intensity of some extreme weather events, although these events can have complex causes and so the outcome here can be less certain.

However, what I understand less is the actual impact of these changes. There is, however, a recent paper by Richard Betts and colleagues that looks at this, specifically in the context of the Paris targets. The paper is called Changes in climate extremes, fresh water availability and vulnerability to food insecurity projected at 1.5°C and 2°C global warming with a higher-resolution global climate model and has already been discussed by John Abraham in The Guardian. What they did in this study was quite interesting. They used a high resolution land and atmosphere only simulation, with sea surface temperatures and sea ice concentrations as inputs. The latter came from a subset of the CMIP5 simulations. The idea being that this provide be a representation of the range of potential internal variability.

The results, however, seem reasonably obvious. For example, the

simulations project consistent increases in temperature-related extremes, with larger changes at 2°C compared to 1.5°C and local changes being larger than the global annual mean.


changes relating to the water cycle are complex, both in their geographical pattern and in the variation between different models. The length of flooding events generally increases across world in all models, but maximum rainfall can either increase or decrease depending on locations. ….. Worldwide, most impacts broadly tend to increase with global warming in most areas.

Vulnerability to food insecurity

increases more at 2°C global warming than 1.5°C in approximately three-quarters of countries assessed. The vulnerability increase can arise from increases in either flooding or drought.

So, there is a tendency for there to be an increase in temperature-related extremes, that is larger at 2oC than at 1.5oC. However, it can be complex, and there is regional variability. We would expect these changes to lead to an increase in vunerability to food insecurity in many regions, but not all, and for this increase to be greater at 2oC, than at 1.5oC.

However, I’m not really sure what to make of this, other than it being roughly what one would expect. Of course, if we do not keep warming below the Paris target levels, then it would be important to understand where to focus our activities. However, there are still impacts that this study does not include, such as sea level rise and ocean acidification, so we can’t really conclude that this is all that we would face.

Does it suggest that we should focus less on mitigation? No, I don’t think so. Keeping warming below 2oC is going to be extremely difficult, and keeping it below 1.5oC may well be virtually impossible. This study is consistent with the impacts becoming more severe with increasing warming. If we would like to avoid the even more severe impacts that would likely occur if we warm much beyond 2oC, then we really should be thinking of ways to reduce our emissions, and should probably be aiming to start sooner, rather than later. At the same time, some of the impacts are probably unavoidable, and so we should also be thinking of how to respond to what we will almost certainly face, which is why these kind of studies can be important.

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58 Responses to Some impacts of warming by 1.5 and 2C

  1. nickreality65 says:



    And just why is that?





    “There is no spoon.”







  2. nick,
    I don’t quite know what you’re suggesting. Are you disputing the greenhouse effect (or, the standard explanation for it)?

  3. Marco says:

    He is, ATTP, he is.

  4. The disruptions in food supplies, drought impact, extreme weather events etc will create more Syria-like conditions around the globe and will send waves of climate refugees on the global walk to find a safe place to exist. First world nations will be plagued by rising sea level and extreme weather impacts pushing infrastructure and economics to a breaking point. “Safe” regions will be fighting to stop climate refugees from making it into a “safe” zone unless the climate refugees exhibit close to zero cultural variation from the safe zone residents. Xenophobia and ultra-nationalism will contribute to global tensions and limit our species’ ability to respond in a sensible and intellgent way to the challenges.

    Some nation states will engage in ad hoc climate engineering projects as the nation states reel under the pressure of climate change and global inhabitants will have to rely on the strength and efficiency of the United Nations to negotiate outcomes or the climate change pressures will ramp up nation state conflicts.

    As long as democracy continues to expand throughout the world leading to the election of thoughtful national leaders, we should be fine.

    Daily CO2 level
    April 6, 2018: 409.03 ppm
    April 6, 2017: 406.92 ppm
    Weekly CO2 level
    March 18 – 24, 2018 409.30 ppm
    March 18 – 24, 2017 406.58 ppm

    Any questions?


  5. Nick’s reality show is entertaining and informative to a certain slice of the population that does not include folks who feel constrained by hard science.

  6. Dave_Geologist says:

    nick, I think you need to do some homework.


    If you understood the GHE, you’d realise that none of those three assertions applies. The rest of your argument therefore falls apart. And that’s before we get to the real world, which is, really, warming.

  7. BBD says:

    From John Abraham’s Guardian article (linked in OP; emphasis mine):



    That’s actually pretty terrifying.

    I’ll try and post the image but it may not work:

  8. BBD,
    Thanks, I had thought of highlighting that aspect of the study, but the post was long enough as it is. I had also thought of including that figure, but one has to be a bit careful, because that isn’t (as far as I’m aware) relative to the baseline. Some areas are already vulnerable to food insecurity. The more relevant figure, I think, is this one

    [Edit: This is, AFAIA, relative to the 1981-2010 baseline.]

  9. Dave_Geologist says:

    ‘twould be more than a little bit disconcerting to discover that RGHE/GHG loop/CAGW are all based on a handful of improperly configured IR instruments.

    Just as well it’s not then. In fact, what is the GHG loop? Or the the RGHE? First I ever heard of them. Does your word salad always come with a free side order of letter salad?

    CAGW, on the other hand, is a standard denier straw man, which instantly condemns your “arguments” to the trash heap.

    Happy to be of assistance.

  10. Eli Rabett says:

    Nick and a bunch of others have not figured out that the energy content of a system can exceed the energy entering and leaving even when the latter two are in balance.

    Perhaps this example could get through to him. Imagine, that instead of sitting in his mom’s basement nick in reality had a job and earned $1000 per week. He deposited the money in his stock trading account, and paid $1000 of it out each week for his comics books, rent, pizza and stock trading expenses, whatever. Now the account is quite large, having been left to him by his late dad, and nick liked to trade stocks and he was constantly churning his account so that $100,000 each week was moved between one stock and another, even into cash. Still, as long as nick held his appetite for comic books, rent pizza, whatever down so that his total expenses did not exceed $1000, the amount of money in his account was in balance.

  11. Everett F Sargent says:

    Is “change in vulnerability to food insecurity” the same as “change in invulnerability to food security” as I would have used “change in food security” where a negative number means worse off (less security) and a positive number means better off (greater security, just flip the color bar so that the x-axis still goes from SOP negative to positive).

    Double negatives have their uses, but this isn’t one of those uses IMHO.

    Also good to see that Greenland and Antarctica will not suffer from a negative change in food security.

    That giant pile of sand known as Saudi Arabia and there vast farmlands and farmers would appear to be worst off though, someone should tell them and their vast farming infrastructures.
    Agriculture in Saudi Arabia

  12. Everett F Sargent says:


    That is because it IS the baseline. “Figure 1. Hunger and Climate Vulnerability Index for 1981–2010 climate (ensemble mean across the bias-corrected HadGEM3 ensemble).”

    And the other figure reads “Figure 18.
    Hunger and Climate Vulnerability Index at 1.5°C global warming (ensemble mean).”

    Unless you are blind, both of these figures are the EXACT same thing (vulnerability in food security is shifted from right-to-lrft a little bit)!

    Also the Abraham article, shows the EXACT same figure as the two above, but his caption reads ” Hunger and Climate Vulnerability Index for 2°C global warming. Illustration: Betts et al. (2018), Philosophical Transactions of the Royal Society A” but there is no “2°C global warming” figure in that paper AFAIK!

    I’m rather SPEECHLESS! Calling Richard Betts.

  13. Everett F Sargent says:

    Same goes for the PDF file! 😦 😦 😦

  14. BBD says:

    Yes, I’m confused too. In the Guardian article, it sez:


    Then shows Betts et al. Fig 1:

    Figure 1.


  15. BBD says:

    My, and possibly the Graun’s, confusion aside, I think ATTP posted the relevant figure.

  16. BBD says:

    Figure 7.

    Hunger and Climate Vulnerability Index calculated for simulated climate states at 2°C global warming for five individual HadGEM3 simulations driven by SSTs and SICs from different members of the CMIP5 ensemble, and the ensemble mean.

    Betts et al:

    The HCVI calculated for 2°C global warming showed very large geographical variability (figure 7) which relates largely to differences in socio-economic factors [22]. Differences in the climate change simulated in different ensemble members leads to some variation in the HCVI at 2°C, although the geographical variation is still dominated by the non-climatic factors (figure 7). Therefore, the ensemble-mean change is a reasonable guide to the results.

    Still pretty terrifying.

  17. Everett F Sargent says:

    Reference 22 has the current index (I’m biased, a bunch of 1st world western Europeans academics, no WMO/UN mind you, versus actual 3rd world POV (2/3, Kirsty Lewis is the common denominator between these two papers) …

    Click to access krishnamurthy_et_al_gec_2014.pdf

    If you want the 3rd world to take notice, then you are much better off by including representatives of the 3rd world in all of your publications IMHO.

    Lock at those plots again, all the white or lighter colors are mostly where white people line. Tony Hayward of BP/DB/TP sez … We’re sorry …

  18. jacksmith4tx says:

    I know it seems a bit off topic but it is my opinion that our species future is directly tied to our technology. The entire biosphere is being altered so it’s impossible for our minds to recognize how interconnected everything is and how fast it is changing. Even the people inventing our future are concerned (check out the controversy about Google employees signing a petition against their own company’s involvement in doing AI research for the defense department).
    After you watch this documentary about AI it could change your priorities.


    Question to the readers… Will our technology save us?

  19. Here’s a comment from citizenschallenge, who had trouble posting

    That’s a valuable post, thanks for the link to Abraham’s article.
    Next time you write about the contentious arguments that continue swirling about establishing an exact climate sensitivity #, as though having that number were a holy grail – you might include a link to this article in order to demonstrate how speciousness laser focusing on the hypothetic ‘climate sensitivity question,’ rather than Earth bound knowable observations.

    The past half century is the best guide we have to what’s in store.
    Though it does require some intellectual honesty and knowledge of our natural world and our “environment” to grasp the trends unfolding before our eyes. To appreciate time, and trends, and math, accumulating sums and such. To have a little understanding of the flow of seasons from a forests’ to pastures’ to riparian zones’ to wild or domesticated lands’ perspective.

    The real tragedy and failure is that such a huge portion of our society don’t have any direct experience with our natural world or its rhythms – city streets and crowding (of the nice to ugly variety) are all they know. Their heads seem filled with a Hollywood/Consumerist mindset – No curiosity, too little interest in understanding how our Earth evolved to this fantastic plateau of the past millennia, or how all that came before led to its present state – and will lead to future realities. They rather dream of heaven after life, or here and now with gluttonous consumption of stuff and complete disregard for the future beyond now.

    How can anything change, so long as so many have no conception of what our planet is all about? What’s sad is there are so many, good documentaries, some fantastic visualization based on data that could only be dreamed of a couple decades ago, with great informative dialogue, doing wonderful jobs of conveying the reality of how Earth and her many children and myriad of interwoven processes function. (But, like they say around these parts, you can lead a horse to water, but you can’t make it drink.) {I kid you not, a posse of easily 50 turkeys just walked past our cabin, being on the edge of a Pleistocene river valley, overlooking the pasture below and current “river” on the other side of that, they are regulars in this area and we have a ringside seat. This is my reality that informs my perspective when I read about the weather reports from across the planet.}

    Guess the question I’d like to propose to your regulars is, how do we take the message of science beyond clubhouse debates? (Particularly the USA folks in light of the coming election and a need for a strong re-awakening of a grassroots effort passionately resolved to demanding honesty and an acknowledgement of fundamental geophysical facts. .)

  20. angech says:

    “If the world has warmed 1 C from 1850, and if our agricultural production has gone up 10 times with that temperature rise then surely we will get another 10 times more production with even another 1 C rise, let alone what good a 2 C rise could do!”
    John Lennon?

  21. Thanks. It’s good to see Betts, et al and others taking the science where it can go for forecasting outcomes.

    Perhaps a bit behind the scenes and, clearly, not something which can readily be trotted out in public view, especially given the temperament of present public discourse, is the creepy feeling we collectively do not understand the nonlinearities in these systems to be making nice, linear extrapolations. In fact, if there is any sensible course, it is that the field of climate science and supporting fields, including atmospheric geophysics, ice sheet geology and cryophysics, tundra social science, and oceanography, especially marine biology, all deserve a national-security-level increase in their levels of support in order to make forecasting of these processes more robust. Given the level of possible risk, I don’t think there is anyone who wouldn’t agree that we need to learn and know more.

    And, to the possibly denialist lurkers out there who might consider this just another example of money-grabbing scientists, frankly, this is just a principle from corporate management. If a business is at risk, it pays to invest in the accountants and others needed to appraise what the level and timing of the risk is. In science, there’s an underlying principle, somewhat substantiated by maths, that the places you want to explore, that is, invest in the most are the places where your information gain is likely to be the biggest. (See fast marching methods and the companion article from Wikipedia. See also level set methods.) These places are a combination of spots where you know the least, and where there are concrete ways of placing observational and experimental assets to maximize learning.

    Without such deep understanding, what’s the most worrying thing is that we are stepping out onto climate terrain we have not ever experienced, and that we really do not understand. We don’t really know how bad or okay it might be. At some point, for example, our experiences and methods for weather forecasting might be obsolesced, simply because they were calibrated in eras where energy transfers were not as rapid or big as they are now, with energy transfer being interpreted in its broadest sense, including energy transfer by water.

    I think, too, turbulent eddies are lacking sufficient scientific attention. They are of interest in oceanography, because, at large scale, they are stable, slow, and persistent, and you can mount a campaign on them to learn. But eddies also store energy, and they are relatively compact. Is it possible a lot of excess energy is bound up in eddies and so not available to wreak havoc on the rest of the climate system? Or are eddies just another means of energy transfer? And what happens if a locale is unlucky enough to have one of these eddies near it?

  22. Everett F Sargent says:

    I smell a rat.

    This paper only mentions RCP 8.5 forcings yet looks at only 1.5C or 2.0C. They should have used RCP 2.6 or the new RCP 1.9 as those will purportedly peak at either 1.5C or 2.0C later this century (with perhaps some finite time overshoot and negative emissions). RCP 8.5 will see 4-6C increase over PI by 2100. RCP 8.5 would/might reach 1.5C/2,0C by ~2050.

    CMIP6 …
    RCP 1.9 2.6 3.4 4.5 6.0 7.0 8.5 (as rows) SSP1 SSP2 SSP3 SSP4 SSP5 (as columns)

    Click to access gmd-9-3461-2016.pdf

    Figure 2. SSP-RCP scenario matrix illustrating ScenarioMIP simulations. (p. 3470)

  23. Dave_Geologist says:



    AFAICS they’re not using linear extrapolations. The models are wound up and set off to run using their built-in physics. If the results look linear it’s a feature of the output, not the input. Enhanced by the splitting of the output into bins, so subtle non-linearities are only apparent if they move a country from one bin to the next. Obviously there’s a separate question, does the model physics adequately capture potential non-linearities. Some things like a catastrophic ice cap collapse, hydrate dissociation are probably ignored. But do we expect them to happen by 2°C? Especially as they’ve focused on the situation as we reach 2°C, not that after we’ve equilibrated for hundreds of years at 2°C.

  24. Dave_Geologist says:


    all the white or lighter colors are mostly where white people line

    Well, actually in terms of the metric employed it’s where the rich, (relatively) well governed, low-population-growth, securely employed people live. Which happens to be where most of the white people live, Which is not to deny that part of that division is down to past bad behaviour by those same white people (or their ancestors).

    But pretending that the DRC is well governed, because it’s all King Leopold’s fault and they could have been better governed had they been left to develop themselves, is not doing the people of the DRC a favour. We are where we are, and need to know where the impacts will be in the real world, not in some counter-factual world.

  25. Dave_Geologist says:


    A relative of mine recently had a fall in snow and by the time he was in hospital he was half-way to being hypothermic. They got him back up to 37°C and now he’s fine. I’m pretty sure that at no point did a doctor say “look how well he’s doing at 37°C, let’s warm him up to 40°C – he’ll do even better.”

  26. Dave_Geologist says:



    Negligible. Unless I’ve done the maths wrong, a kilogram of water moving at 1m/sec has 0.5J of kinetic energy. It takes 4186J to raise the temperature of that same kilogram by 1°C. So the thermal energy is five orders of magnitude more than the kinetic. Even if you say it took 100 years to gain that heat, it’s still three orders of magnitude. And where did the energy come from to make the eddy? The heat in the ocean/atmosphere. So on balance, neutral energy-wise although perhaps not short-term-SST-wise.

    If anything, it probably promotes a bit of cooling (energy, not temperature). Satellite photos I’ve seen of eddies show them as bright due to plankton blooms promoted by upwelling nutrients. Which increases albedo, plus the critters probably give off DMS which promotes aerosol formation.

    Thanks for the link BTW. There is a cautionary element in the paper, in that the eddies may mobilise seabed carbon to shallow waters, reducing their capacity to absorb atmospheric CO2.

  27. JCH says:


    Who said this?

  28. Dave_Geologist says:

    Who said this?

    Probably no-one 😉

    I did a quick Internet skim and it wouldn’t surprise me if it was true of production, as opposed to productivity. World population has grown six-fold since 1850, so six-fold increase is required to feed everyone on a BAU basis. Obviously we are eating “better”, if you define that as more food per head (obesity epidemic) and moving up the food chain (more meat). That has been supported by some combination of more farmland and more productive agriculture.

    So if angech meant that global warming has enabled ten times more food to be grown, that doesn’t mean global warming was the cause. More cropland certainly played a part, better breeds, irrigation, fertiliser, mechanisation, transportation so surpluses don’t just rot, etc. It’s perfectly possible that those factors contributed more than ten times, and the impact of global warming was negative. Or was positive for a while and has now turned negative.

  29. BBD says:

    Who said this?

    Someone unfamiliar with the combined effect of advances in agricultural technology (especially mechanisation and fertilisers) and that other driver of productivity – increased demand as global population grew. Trying to peg agricultural productivity growth from 1850 on temperature is daft.

  30. BBD says:

    Well, Dave G and I posted very similar comments – at exactly the same time – 2:17. Sorry for the repetition.

  31. JCH says:

    It was called the green revolution long before CO2 fertilization was something farmers ever thought about. I’ve seen grown men pray for rain. I never saw one pray for more CO2. It’s just an utterly ignorant comment.

  32. @Dave_Geologist,

    Sure, but it’s not like even the latest models are all running ab initio physics. To save computation time, there are often lookup tables inserted which are calibrated off of observations and, from what I understand, weighted by performance on hindcasts.

    Also, susceptibility of forecasts to nonlinear effects is limited by grid resolution, coarse, again, to reduce computation time. That really matters. For example, in viscoelastic modeling of ice sheets, some qualitative macroscale phenomena which were completely missed when 1 km^3 resolution was replaced by blocks tens of meters on the side.

  33. On the slight chance that this goes through, regarding your OP–most serious discussion of our response to climate change acknowledges that we will need to spend time and money (quite a lot of both) on both adaptation and mitigation, something that the lukewarmers I know would certainly agree with, although Steve Mosher may pop his head in at any moment to disagree.

    It seems quite likely that the proportion of resources dedicated to each strategy will change over time, as it is clear that enough resources for both won’t be available, for a variety of reasons.

    We actually know how to compute a sliding scale commitment if we can agree on certain assumptions. Among those for me is the idea of hardening defences against current weather as a first step, but including a margin to ‘future proof’ those defences against IPCC projections of sea level rise, storm surge, increasing precipitation, etc. We not only know how to compute optimal spending flows to achieve the least-bad result, there is software out there that will do so on our behalf and provide differing solutions to choose from.

    Those applications used to have a name.

  34. BBD says:

    How do we future proof global agricultural productivity Tom? And marine ecosystems – in fact all that ecology stuff that we depend on everywhere, all the time that is adapted to Holocene norms?

    Lotta future proofing needed.

  35. Everett F Sargent says:

    I am the squirrel and I have some nuts to pick (in no particular order).

    “it is recognized that precipitation data alone may not always be adequate for representing flood and drought events, so the current method is regarded as preliminary.”

    Preliminary? You can say that again.

    “In the current version of the HCVI, climate-change impacts on other quantities such as crop yield are not considered.”

    But, I think we are modelling the FUTURE, not the present.

    “We ran the model using only its atmosphere and land components, with time-varying sea-surface temperatures (SSTs) and sea-ice concentrations (SICs) prescribed as input quantities.”

    So, CMIP5 ocean SST’s/SIC’s (modelled, calibration period ends with 2005 observational data).

    “Land cover was fixed in this simulation—there was no dynamic vegetation nor any time-dependent anthropogenic land use change.”

    Mkay. (insert bug eyed emoticon here)

    “This inconsistency would have consequences if these results were applied to time-dependent impacts and adaptation assessments, but that is not the case here so this concern does not apply.”

    Note that these models are the very definition of time dependent determinism. (insert bug eyed emoticon here)

    “This iteration of the HCVI only considers in-country production of food and does not account for food trade.”

    Mkay. (insert bug eyed emoticon here)

    “For this reason, the HCVI is only calculated for 122 developing and least-developed countries (defined here as countries not in the OECD or EU which can be resolved by the scale of the climate model; i.e. larger than 500 km2).”

    The white people excuse (coupled with the previous food trade excuse, no food trade between the USA and others, because USA crops fail? Yes or No. Not addressed.). (insert bug eyed emoticon here)

    “Both questions require an appropriate assessment of uncertainty.”

    IMHO, this is not that paper. 😦

    “Table 4. Time of reaching GWLs of 1.5°C and 2°C in each bias-corrected output from the HadGEM3 climate simulations, driven by different sets of CMIP5 sea-surface temperatures. The dates are the centre year of a 20 year period for which the climate data is applied to the HCVI calculation and JULES simulations.”

    So, “the centre year of a 20 year period” mkay.

    Model driving SSTs, Year to 1.5°C, Year to 2.0°C and °C/century (my add dy=0.5°C)

    Year to 1.5°C (min=2019,max=2036,median=2023.5, mean=2024.7,sigma=6.1)
    Year to 2.0°C (min=2032,max=2051,median=2035.5, mean=2037.8,sigma=7.0)
    Rate (°C/century from 1.5°C to 2.0°C) (min=3.3,max=4.5,median=3.7, mean=3.8,sigma=0.4)

    So essentially, no time for mitigation and no time for adaptation. (insert bug eyed emoticon here)

    “Socio-economic factors affecting sensitivity and adaptive capacity are fixed at present-day conditions.”

    No future population growth modelling (which occurs mostly in SE Asia (including China thru to India/Pakistan, then in Africa after 2050). This paper reads like a litany of excuses, hmm, err, assumptions. (insert bug eyed emoticon here)

    Results? Dark people get effed’ at 1.5°C. Dark people get effed’ at 2.0°C.

    Conclusion? Dark people get effed’! Who knew? Of course, we already knew this, since about 1492 even. I’ve already used the Tony Hayward graphic, damn it.

  36. But oceanic direct primary productivity has increased:

    as has land:

    There is no reason to expect this will continue unimpeded, however, particularly with acidification affecting the former. And, of course, this is not at all the same as agricultural productivity.

  37. Everett F Sargent says:


    Not sure who you are referencing your comment to, but a link (or two) would be of some utility (I’ll assume for the moment) with respect to your graphics (inverse Google image search did not work). TIA

    But as an aside, I walk away from this paper thinking that, this paper tells me that 1.5°C is too much, let alone 2.0°C.

    “We projected changes in weather extremes, hydrological impacts and vulnerability to food insecurity at global warming of 1.5°C and 2°C relative to pre-industrial, … ”

    So, I am only interested in the ‘so called’ money shots, the food security graphics, Figure 1 (existing or baseline), Figure 7 (HCVI for 2°C), Figure 8 (Change in HCVI for 2°C relative to baseline), Figure 18 (HCVI at 1.5°C) and Figure 19 (Change in HCVI from 1.5°C to 2.0°C.

    So, I’d expect a tabulation for the 122 countries considered in the form of an amended SOM/SI as follows:

    (1) Baseline or existing (with associated delta temperature from whatever their definition of PI temperature was).
    (2) HCVI for 1.5°C future (either as relative or absolute change)
    (3) HCVI for 2.0°C future (either as relative or absolute change)

    Seems simple enough, three tables of HCVI, 122 countries, Baseline delta T from PI, 1.5°C and 2.0°C. They all have these in graphical format (with some rather obvious errors) and I want to see the tabulated numbers, they have not presented those tabulated results. 😦

  38. @Everett F Sargent,

    The reply wasn’t specifically to you, but to the general discussion. There are increases in productivity, as I noted. References:

    (1) R. Lindsey, R. Simmon, 5 June 2003, “Global garden gets greener”, NASA Earth Observatory.
    (2) R. R. Nemani, C. D. Keeling, H. Hashimoto, W. M. Jolly, S. C. Piper, C. J. Tucker, R. B. Myneni, S. W. Running, “Climate-driven increases in global terrestrial net primary production from 1982 to 1999”, 6 June 2003, 300, Science, 1560-1563.
    (3) F. P. Chavez, M. Messié, J. T. Pennington, ”Marine Primary Production in relation to climate variability and change”, Annual Review of Marine Science, 2011, 3, 227-260.

  39. Dave_Geologist says:

    We kinda knew that though, didn’t we? Or at least the IPCC did, which is why increased biosphere uptake is part of the carbon accounting, and most of the biosphere is green. But from that same accounting we know that it’s not increasing enough to offset our emissions. And it may not be increasing in an agriculturally useful way. More woody stems, less nutrition, for example. And phytoplankton blooms are not necessarily welcome. Just ask the Olympic divers. And if you grow bigger wheat stalks, but they get beaten flat by rain before harvest, that’s a plus for NPP but a minus from the Betts et al. perspective. Plus I’d like see what’s happened now that the faux pause is over.

  40. Mitch says:

    Hyper–You should look at the caption of the top figure you attached, from Chavez et al: “…Sediment core record from the continental slope off Callao, Peru…”
    This is a record from the Peru upwelling system, not a global signal.

  41. Francis says:

    I think that all of the following are true:

    1. Americans waste an enormous number of calories — more than 30% by some estimates.
    2. American farmers have the capacity to innovate. Rising prices for a crop, due to crop failures, will provide strong signals for them to do so.
    3. Nevertheless, unless we go to a zero-carbon worldwide economy, we will continue to discover that our infrastructure — everything from farms to skyscrapers — has been tuned to our 20th century climate in surprising and expensive ways. Even the most detailed ex ante analysis will miss something that comes back to bite us.

  42. angech says:

    model ”
    Yet BBD says “Trying to peg agricultural productivity growth from 1850 on temperature is daft.”
    So the paper is daft as well.
    OK to predict warming effects into the future but not OK to consider the effect of past warming?
    Did we or did we not rise by 1C from 1850?
    Do we not have greater food security now?
    Did the rise in temperature have some positive consequences ?

  43. Dave_Geologist says:

    angech, I would rephrase it as “Trying to peg agricultural productivity growth from 1850 on temperature alone is daft. As is equating production growth with productivity growth, without first accounting for increased farmland, mechanisation, fertilisers, irrigation, better breeds etc. etc. etc.”

    There are previous papers which have looked at projected productivity changes by observing how productivity of major crops varies across their growing range. Unsurprisingly, they have “Goldilocks” zones and perform poorer where it’s hotter, colder, wetter or drier. Unsurprising, because we’ve spent thousands of years selectively breeding them for those conditions in their pre-21st Century distribution.

    For example Assessing agricultural risks of climate change in the 21st century in a global gridded crop model intercomparison. All models are flat or negative after 2020 except for the one which assumes an infinite supply of nutrients. So maybe the world could be positive, but it would take something like the West building huge fertiliser plants and agricultural infrastructure in countries that can’t afford to do it themselves. For free. Which I seem to recall was one of the Paris sticking points. A more realistic approach is to only allow the extra nutrients where the wealth, infrastructure, governance and land/job security allow it. Which of course is what Betts et al. did. Which is why the USA gets off lightly.

    When I hear lukewarmers saying “I support the idea of the historic polluters spending trillions of dollars to mitigate the impact of climate change on poor countries, a long way off with different skin colours and religions, some of whom hate us already and will be grudging recipients”, then I’ll take them seriously about global adaptation.

  44. John Hartz says:

    I suspect that the contents of the following article are relevant to this discussion…

    Analysis: How much ‘carbon budget’ is left to limit global warming to 1.5C? by Zeke Hausfather, Carbon Brief, Apr 9, 2018

  45. John Hartz says:

    The introducory paragraphs of Hausfather’s Carbon Brief article that I citied above…

    In 2015, by signing up to the Paris Agreement on climate change, nearly every country pledged to keep global temperatures “well below” 2C above pre-industrial levels and to “pursue efforts to limit the temperature increase even further to 1.5C”.


    While calculations based on Earth System Models (ESMs, see below) used in the last Intergovernmental Panel on Climate Change (IPCC) report suggest that we have only a few years left at our current rate of emissions before we blow the 1.5C carbon budget, some recent studies have suggested that the remaining carbon budget is much larger.

    In this article, Carbon Brief assesses nine new carbon budget estimates released by different groups over the past two years. Most show larger allowable emissions than were featured in the last IPCC report. A number of studies suggest that carbon budgets estimates based on ESMs may be on the low side as a result of limitations with how some models represent the carbon cycle.

    However, there is still a wide range of variation in these new carbon budgets, arising from differences in approaches, timeframes, estimates of warming to-date and other factors. Recent studies suggest the remaining carbon budget to limit warming to “well below” 1.5C might have already been exceeded by emissions to-date, or might be as large as 15 more years of emissions at our current rate.

  46. angech says:

    Thanks Dave.
    Either you accept the idea that rising temperatures can only generally cause harm and argue it effectively or you are trying to say we were too cold 167 years ago and the warming was needed but like Dave’s example some warming is good but too much is not.
    Either way if you are going to consider a1.5 to 2.0C in the near future it is relevant, not daft, to consider the past rise as a guide to future behaviour.


    I doubt it will take trillions, but if it does, it does. What odds will you give me that I’m not the only lukewarmer who would sign up to this? (I have been advocating same/similar propositions for… oh… a decade.)

  48. Dave_Geologist says:

    A long post but my excuse is it’s back on topic 😉

    The past rise as a guide to future behaviour tells me that cold wet summers are bad for wheat production, as are hot dry summers. Because people plant wheat where wheat grows well in normal summers. Not where rice or potatoes grow well.

    I chose wheat because there is an existing study on wheat Rising temperatures reduce global wheat production, which finds that wheat is already being adversely affected and “Global wheat production is estimated to fall by 6% for each °C further temperature increase and become more variable over space and time. Days-to-maturity and grain yield fall – more haste less s(p)eed 😉 . The experiments are well represented by the ensemble of models used for projection. To put that 6% in perspective, it equals a quarter of global wheat trade. Which implies that three quarters of the world’s wheat is consumed in its country of origin, and only a quarter is traded internationally. Which is why a crop failure in a single exporter causes prices to skyrocket.

    “The global temperature impact simulations were carried out for region-specific cultivars, including spring and winter wheat cultivars”. IOW these simulations assume farmers keep growing the same kind of wheat. So could perhaps be mitigated if they switched to a different type of wheat (e.g. IIRC, winter wheat needs frost to trigger germination), changed their planting time or grew something else like millet or rye. Of course to do that they’d need to believe it was a new normal and not God’s punishment for legalising gay marriage, solvable with prayer or by electing right-wing legislatures. Which unfortunately, is probably what your average US, Canadian or Australian wheat-belt farmer thinks. And also requires the more heat-tolerant wheat to have the right water amount and seasonality requirements.

    Some of those things can be mitigated (e.g. more fertiliser or irrigation). As per the infinite-nutrient-supply simulations I mentioned up-thread, but subject to economic and governance constraints as per Bett et al. Not a lot you can do about thunderstorm dumping on your harvest though. And in areas seeing more drought, you’ll be competing with city-folks for water. And maybe rich countries can buy their way out of trouble. But with only a quarter exported, that will not be cheap and there just may not be enough to satisfy demand.

    Interestingly, their Fig. 2a for 1981-2010 does indeed show that some test sites in Arizona, near the US/Canada border, in Ukraine and Kazakhstan and China, showed improved yields. Some are towards the northern limit, others probably irrigation-dependent so a reflection of the infinite-nutrient scenario. So yes, some warming to date has been of some benefit to some wheat-growing areas. But they’re vastly outweighed by negative sites in Mexico, Brazil, Argentina, Western Europe, Egypt, Sudan, Iran, Pakistan, India, Bangladesh, elsewhere in China and Australia. Hmmm, looks like a long list of countries with large populations, many with food poverty, poor governance and a history of violence, plus a few key exporters and a key importer. What could possibly go wrong? There’s no data from Russia: they probably consider it a state secret after their 2010 crisis.

    Is the past the key to the future? Well in this case the past shows more losers than winners (since 1981; maybe there are more winners since 1850 but that’s a long way back in the rear-view mirror). Figure 2b shows the results at 2°C. By then literally everyone is a loser. And they had to expand the scale. From +3% to -5%, to 0 to -56%. Sudan’s wheat productivity is predicted to halve. Northern Europe and the US/Canada border region are the only ones to lose less than 8%. So back to the topic of the the thread. On this metric, 2°C is not good news. Unsurprising, since 1°C is already bad news globally and good news only locally.

    4°C? Just let’s not go there. Northern China is the place to be – only one with less than 10% decline. Not big enough to feed the world though. Much of the tropics lose half their productivity. Mexico, Brazil, Egypt, Sudan, India, Pakistan and Bangladesh get hammered. Think that might trigger a flood of refugees? From states with big armies, some with nuclear weapons, who won’t take no for an answer? Read Christoper’s Priest’s Fugue for a Darkening Island. It’s hard going, in part because all the characters are nasty, brutal, selfish and racist. It’s not meant to have heroes – it”s a dystopia. And it’s from the 1960s so probably has some trigger-words which wouldn’t get published nowadays (confession: it’s so depressing I only read it once, a long time ago).

  49. Dave_Geologist says:


    I wouldn’t take the bet Tom. Because I’m sure you’re not the only one, and I will take you and others like you seriously about global adaptation. Just in the minority. And I apologise if I appeared to be painting all lukewarmers or deniers as racist. Even just a little bit (as in “I’ve got nothing against people not like me and wish them no harm, I just think I should only help people like me”… which also goes to things like “I don’t want to pay taxes to help the poor, but I’ll pay charity to my Church because I trust them to distribute it to the sort of people I want to benefit”… which is a broader in-group out-group thing than just race or colour). But at least in the UK, the newspapers that deny climate change and want to cut foreign aid also get worked up about immigrants, particular groups of terrorists and not others, and being woken up by the Call to Prayer, but object to church bells being silenced. So the editors must think there’s a market out there.

    I’ll weasel-word my way to saying that I’ll take lukewarmers as a class seriously when i see the majority saying “and don’t worry about the Third World, we’ll be happy to pay taxes to rescue them if ECS turns out not to be at the bottom of the range”.

    BTW by lukewarmers I meant people who accept AGW, and maybe even the IPCC range, but who don’t want to do or spend any more than is absolutely required by the minimum plausible ECS, and ramp up spending and effort only when ECS is incontrovertibly higher than that. IOW who apply the precautionary principle to spending money and changing lifestyles (don’t do it until we absolutely have to) and not to future damages. I don’t include people who are in denial, or who in-private accept the IPCC range but jump onto the minimum because their real motive is political or economic, not a disagreement over the science or how to apply the precautionary principle.

    I’m afraid I disagree about the trillion dollar costs. Wheat costs about $200/ton, and world production is about 750M tons. So that’s a $150B/year crop. You’ll see in my other post that wheat is expected to take a 6% per °C productivity hit globally. So that’s about a $10B/yr/°C hit on one crop alone. So a trillion dollars per century at 1°C, or per 25 years at 4°C. Factor in other crops, heat stress making places unlivable without 24/7 a/c, storm-surge proofing New York, abandoning and moving Miami because the porous bedrock means dykes and levees won’t work, and it will be trillions. Are you still up for it? People can do remarkable things when they put their minds to it. According to Wiki, at the peak of WWII, US government spending represented 79% of GDP (but obviously of an enlarged GDP because military spending was included), and 20% of the population was employed by the armed forces. That sort of effort doesn’t just need you and me, it needs a national and international consensus.

  50. BBD says:


    Just read what I wrote again. And everything Dave G has – very patiently – written since.

  51. Francis says:

    Found at PZ Myers, a warming Minnesota is apparently resulting in an increased number of frozen septic tanks. The lack of insulating snow is driving the freezing line deeper.

    So, which study of the costs of global warming included the costs of damages to septic tanks and increased road wear due to traffic attributable to septic tank pumpers?


    This a good factoid to keep at our fingertrips because the struggle to respond appropriately to AGW is like the struggle against fascism in the last great war, it can only be managed by collective effort and sacrifice on the scale that consumes a large fraction of GDP. Individual effort and sacrifice are lovely and graceful in principle, but if we total up the balance sheet on individual effort we will see only a tiny fraction of GDP.

  53. Dave_Geologist says:



    It’s not just the warming, it’s the variability and unpredictability. Which some of the impact studies take into account. In the wheat case, for example, the shorter growing season with warming should give farmers more flexibility in when they plant, which may help in mitigation. especially under irrigation, where rainfall timing is not to important. But not if year-on-year variability increases and you don’t know within a month or two when to plant.

    Back to frozen ground, the recent cold snap in England was caused by unusual weather conditions, which I suspect was due to jetstream changes (wavy and slow), although it’s too early for formal attribution. There was a period when cold continental air extended over the UK causing unaccustomed freezing in SE England, leading to a spate of burst pipes,18,000 homes without water, some for more than a week, and factories shut down to conserve supplies for households and essential services. That was followed by heavy snow in SW England, then a sharp thaw by 10°C as Atlantic air won our. Rinse and repeat a couple of times as the air masses battled, with a suggestion we may get one more this season. The unpredictability caused more trouble than one weather or another.

    That was the first hard frost in SE England for years, probably decades, so there may have been a mix of complacency (pipes too shallow or poorly lagged) or just a backlog of corroded pipes and weak joints which hadn’t been frost-challenged for decades. Scotland had a little bit of leakage, but much less. I’m tempted to make political capital and say that’s because Scottish Water is an arms-length government agency whereas the English water companies are privatised. But it’s more likely that Scottish Water is better prepared for a hard frost because it experiences it every year.

    If we get a change in weather patterns from mostly Atlantic to flip-flopping every couple of weeks, that will be incredibly hard to deal with. Much more disruptive than a degree or two of temperature rise. You can adapt to a new normal, but what if there is no normal?

  54. angech says:

    Put this up at Tallbloke’s.
    Happy with my rationalization so thought I might share it here as well. Older blog post and out of the way. ATTP might appreciate it as some thoughts on Solar system evolution, or not.
    “Planet surface temperature is dependent on pressure and solar distance.
    The third component * is the actual physical makeup of the planet and its atmosphere in in question.
    This seems to be partly ignored by N and Z which PM is quite right to question.
    Both views are mostly right and actually support each other.
    E.M.Smith rightly asks about using the earth as a laboratory. “We have a natural lab here, use it.”

    We are stuck with a 14 billion year old universe in which a 4.2 billion year old solar system has recently evolved.
    It is highly likely that solar system accretions throughout our known galaxies are of varying ages from just forming to perhaps 8 billion years old ending when the sun blows up.
    Accretions have inbuilt heat without suns, they are not cold dead lumps of rock. Jupiter for instance would still have a reasonable temperature at the surface without the sun, as would the earth at depth.
    As EM Smith implied we do have a laboratory. It is a gigantic centrifuge whose spun components have temperatures depending not only on solar, pressure and internal heating [*composition] but also on the other component of physical makeup, what materials are in the planet and it’s atmosphere*. This is determined by the age and origins of the solar system accretions.

    So we have the old earth, pre stromatolites with? a CO2/N atmosphere changing to an O2/N atmosphere for instance. Did the old earth have the same temperatures as the new earth?
    We have the molten earth cooling down theory. Was the earth surface 4.2 Billion years ago the same as it is now? This is the nub of the question for Tallbloke et al. Do they believe in one temp for one planet same gravity, same insolation for ever or do they agree that the evolution/age/composition of the planet can affect these figures?

    Once, if we admit that composition plays a part we could go on to the admittedly small but relevant role of GHG, both water and CO2 and elsewhere others .Which exist in wildly varying amounts on different planets. I am quite happy with the concept of gravity, mass, friction and normally more temperature at depth. We have the confounding effects of Oceans being colder at depths, not hotter due to the difficult nature of defining a surface. Very easy for gas/solids only. This makes temperature determination on the earth even more difficult.
    Due to the variability in the main GHG, water vapour and its role in albedo control* [a third component not considered there is room for temperature variation due to GHG including and amplified by CO2 which could theoretically move the expected temperature a few degrees away from N and Z reasonable average estimate.

    The two theories complement each other. If you take the Solar, add in the Gravity and then look at the actual physical composition of the accretion [if it has a surface in the first place -definition please]. It’s own internal temperature [and how it gets out to the surface], the makeup of the planet surface [All white chalk for instance compared to black or red ferrous compounds], and the albedo and GHG effects of the gases in or not in the atmosphere [and no oceans of whatever substance please] will all modify the expected result.
    PM right.
    N and Z right.
    In parts.”

  55. Dave_Geologist says:

    Re CO2, we could go with Wiki Less than 1% through the Phanerozoic so too small to matter, other than for its GHG effect. Which of course explains why Paleozoic glaciations were relatively rare, despite the weak young sun.

    Estimates of atmospheric CO2 in the Neoarchean–Paleoproterozoic from paleosols. Enough to make a difference but the colder, younger Sun means that liquid-water temperatures are perfectly explicable by conventional GHG theory. So perhaps an argument against a wacky gas-pressure theory – surely such large CO2 levels would have perturbed the climate well away from what conventional theory predicts? How did the Earth manage to stay habitable? Gaia? Perhaps, but a rather cruel and heartless Gaia. The global glaciations of the time coincided with oxygenation spikes and CO2 drawdown. One interpretation is that evolution made several attempts at establishing photosynthetic life, but the first few killed themselves off by drawing down CO2 to the point where the planet froze. Photosynthetic life couldn’t properly establish itself until the Sun got hot enough to maintain liquid water with lower atmospheric CO2, That control knob again. It’s CO2 all the way down 🙂

    Under the constrained local temperatures, the P CO 2 levels were calculated to be 85–510 times the present day atmospheric level (PAL) at 2.77 Ga, 78–2500 PAL at 2.75 Ga, 160–490 PAL at 2.46 Ga, 30–190 PAL at 2.15 Ga, 20–620 PAL at 2.08 Ga and 23–210 PAL at 1.85 Ga. The estimated P CO 2 levels are higher than those to maintain the average global surface temperature of the Earth above the freezing point of water only by CO 2 itself. The newly estimated P CO 2 levels probably imply that atmospheric CO 2 decreased gradually in long term in the Neoarchean–Paleoproterozoic and that the glaciations at 2.9 and 2.4–2.2 Ga were differently triggered.

  56. Dave_Geologist says:

    Oops, last para should have been blockquote from palaeosol paper.

    Some snippets:


    More-or-less but we don’t know in detail because the surface was remelted and the record wiped clean by the Late Heavy Bombardment 4.1 – 3.8 Ga ago. But geochemical evidence shows it was already differentiated into Core, Mantle and Crust long before the LHB. E.g. zircons of granitic origin from 4.375 Ga. There is evidence of water-worn zircons dating to around 100 Ma after the LHB, so there was liquid water by then.


    Meaning unclear. Do you mean, if those things stay the same, then no change? Then I presume yes. Are you asking did those things stay the same? I presume yes for gravity and planetary composition, no for the others. But nothing to do with the composition of the (solid) planet, just insolation and atmospheric composition.

    admittedly small but relevant role of GHG

    Wrong, massive, biggest control knob by far after gradual increase in Sun’s output. See my previous post.

    Due to the variability in the main GHG, water vapour etc.

    Cart before horse. CO2 is the driver because it can increase or decrease essentially without bounds and is long-lived. H2O, on a planet 2/3 covered with water, must remain more-or-less in equilibrium with the ocean surface, so is a feedback dependent on atmospheric temperature. No matter how much water vapour you pump into the atmosphere, it will rain out once it gets much above 100% relative humidity.

    Last para: just no. Period. Stop and think for a moment angech. Has the mass of the earth changed in the last century? Has the internal distribution of mass and composition (remember, the earth is 8000 miles in diameter and the stuff moves at inches per year). Has crustal heat flow? You do know we measure it, and people go down mines. Pretty sure we’d have noticed. Has the earth’s atmosphere changed? By the several percent which would be required by the “complementary model”? Albedo? Yes, but we know about that and why. What has changed? Oh look, CO2. By just the right amount to explain the warming, once water vapour and albedo feedbacks are taken into account. As was predicted a century ago from basic physics. Occam’s Razor. Or, if it walks like a duck and quacks like a duck…

  57. angech says:

    Thanks DG

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