Two degrees of warming

Now that it looks as if some sort of agreement may come out of Copenhagen, its natural to ask what sort of agreement we need. The current targets being proposed suggest that warming should be limited to 2 degrees over the next century. That implies stabilising atmospheric C2 concentrations at 450 ppm, and an agreement to cut developed country emissions by 20-25 per cent by 2020, with convergence to a level 90 per cent below current developed country levels by 2050 would be adequate (note that this part of the post is based on my reading of Garnaut, Stern & IIPCC, not my own expertise).

At least some discussion in Australia suggests that these targets are hopelessly weak and by implication that it would be better to oppose any action than to lock ourselves into an agreement of this kind. I disagree, and I will try to spell out why.

First up, as in other debates about climate change, it is important to pay attention to the science, rather than to rely on prejudice or on supposed authorities who are either unqualified or whose qualifications aren:t relevant. Thats why I have refused to debate climate science delusionists here, instead pointing them to the results of scientific research, summarised by the IPCC and other bodies.

But the case here is a bit different. The big impacts of climate change will be on agricultural production and natural environments and the relevant experts are ag scientists/economists and ecologists. The views of climate scientists like James Hansen, while very important in projecting the climatic effects of CO2 emissions, have no particular standing when it comes to assessing the damage associated with any particular climatic change.

As regards the ag economics, I am an expert, and am therefore happy to explain my position and discuss it with readers. I will add some links later, but for the moment Ill ask you to take statements of fact on trust that Ive done the work to verify them

What matters for agriculture is not so much the ultimate change in average temperature and rainfall, but the pace of change. Agriculture is undertaken in a wide range of climates, so there are very few places where an extra couple of degrees will make farming impossible. What changes in temperature and even more changes in rainfall will do is change the kind of crops that can be grown in any given location. Some areas will be more productive, and some less so, but, in the long run these effects will mostly cancel out. For a change of more than 2 degrees, the negatives predominate and they become overwhelming after about 4 degrees.

As regards the pace of change, 2 degrees warming over a century implies 0.2 degrees per decade on average which is like shifting the climate about 100 km closer to the equator each decade. That involves some costs, but they are probably manageable.

If agriculture can handle 2 degrees of warming, it seems likely that most human activities will do so. So, as far as human activity is concerned, it makes sense to target 2 degrees of warming as a reasonably conservative choice.

If you want to justify a target lower than 2 degrees, it has to rely on concerns about ecological damage and loss of biodiversity. There is no doubt that 2 degrees of warming will do a lot of damage, for example to coral reefs. But quite a few of the ecologists I talk to are at least as concerned about the immediate threats to biodiversity (in the case of coral reefs, these include overfishing, destructive fishing methods and nutrient runoff) as about the current rate of climate change. As the IPCC shows, business as usual would be disastrous. But the difference between 1 and 2 degrees of warming is probably less than the difference between sustainable and unsustainable choices in industries like fishing and forestry, and we could make a lot of progress on the latter issues at very modest costs.

Obviously, you can always push for a more ambitious target at higher cost. But the costs accelerate pretty quickly once you aim below 450 ppm. So, people advocating more ambitious targets ought to say how much they would be willing to pay and what they would give up.

54 thoughts on “Two degrees of warming

  1. I understand that Michael but our maximum production is increasing, NOT decreasing.

    People talk as if global warming is a future event yet it’s been with us since the 40s, possibly earlier – there’s no empirical evidence that an increase in warming is detrimental to our agriculture and I haven’t observed the wheat belt heading 400km north over the past 4 decades.

  2. Janama, whilst Australia’s wheat belt areas has increased fourfold since the 1940s, changing circumstances means Australia needs to keep abreast of the world by introducing new and innovative sustainable farming practices inline with the CPSR.

  3. Semi dwarf wheat varieties almost doubled production and made it worth while to fertilise adding further productivity. Australia also moved to more irrigated wheat, often as a second or rotation crop in rice and cotton enterprises.

    So, increased production by breeding, cultural practice and irrigation has so far kept ahead of global warming.

  4. It is worth stressing that people seem to be assuming linear and time reversible effects of warming. I’m not confident that assumption holds.

  5. Donald made some important points on population growth which also tie into JQ’s mention of short term threats to the Barrier Reef of over fishing and nutrient pollution.

    Sustainable Population Australia, SPA, is making a submission to Copenhagen on the role of population growth in GHG emissions. The ONLY submission on population growth.

    I realize population growth is an ‘out there’ subject to most people but, boiled down, it really is only the same old issue of sustainability vs unrestrained consumption, quality vs quantity, good stewardship or bad. It is high time we all grabbed a big handfull of ‘population growth’ consequences and rubbed it in the faces of our ‘growth’ captured polititians. I have been. They don’t reply. That tells me it is hitting a nerve because I have sent supporting emails on many other subjects and they usually reply to them.

  6. Protein matters have dropped in some cereal crops where experimentally carbon dioxide was present in a greater volume per measured cubic area.I don’t however think that will be a real problem,unless it becomes a defining moment in soil sequestration attempts.The growing of benign fungi in paddocks where cereal is grown,for many reasons including holding moisture or water seems to be worthy study that needs locational research.Some of this research has been taken over by the GMO friendly scientists ,and frankly some of these people have been wrong all their lives,but where there is money,there is a potential for lofty qualifications and farmer dependency.Friable soils with humus and gation qualities are not going to be the breeding grounds for failed cropping when the water profile is substantially low.Mobile Fog or Atmospheric sheeting moving like irrigation technologies,and probably compatible with existing irrigation technologies is only requiring some people to see if they can increase soil moisture profile from the atmosphere in this manner.Powering of the mobile Fog sheets needs some thought.Look up FogQuest,I think its called, where some successful pulling down of atmospheric moisture has worked..Wether this will still be useful in those locations in use,in the future needs some analysis.Back up with the Hilsch Vortex Tube technologies.As I have related before,there maybe a possibility of engineering into certain harvesters a capability of drawing atmospheric moisture down to ground well.

  7. I think there is a need to directly address the “why 350?” argument?

    Specifically, Hansen’s “Target Atmospheric CO2” paper.

    Without convincingly addressing all points in Hansen’s paper (including all feedbacks), I don’t see how a higher target can be justified.

  8. An article in the Age (2009-08-30) notes how the latest “drought” might be a more permanent change…

    Basically the SE Australia chunk including Vic and a bit of SA are exposed to lower rainfall patterns as the new normal. The scientist groups mentioned in the article used state of the art US numerical modesls to test what happens in SE Aus if there is no global warming trend, and then what happens when GHGs, aerosols and other human impacts are added. In the first case the conclusion was that SE Aus would have the usual climatic conditions with historical rainfall statistics. The second case shows an increase in the intensity of the subtropical ridge which pushes the rain bearing lows away from the southern part of Australia. I’ll caution here that the models provide statistical support for the hypothesis that the global warming trend from temperature data has an effect upon rainfall patterns – reducing rain – in SE Aus. However, the state of the art climate models are capturing numerous regional effects now; it means that climate models are lifting in capability and reliability.

    No doubt this will be written off in some parallel blog as government scientists conspiring to provide the government with another reason for an ETS, blah, blah, blah. Maybe, just maybe, there is something to the AGW theory afterall.

  9. My own view on the 35oppmv target is the same as my view on Code Red’s 300 target or some notional group’s proposal for 240ppmv.

    Who in his or her right mind wouldn’t want the lowest possible target?

    Dreaming up targets doesn’t get us there though and until someone can show how we can get enopugh people to do enough to stop us getting to 450ppmv the talk seems idle.

  10. lowest possible?

    0ppm wouldn’t be a good idea.

    Hansen has made a clear case for 350ppm in his “Target Atmospheric CO2” paper.

    Anyone who advocates a higher target needs to address all issues raised in the Hansen paper – especially feedbacks.

    Without convincingly addressing all points in Hansen’s paper, I don’t see how a higher target can be justified.

  11. I’d say that in practice 0 ppmv simply isn’t possible. The lowest possible given the cost constraints, the number of humans, the persistence of biota etc is probably about 240ppmv … and since there would be no marginal benefit going blow that the rest is moot.

  12. @Fran Barlow
    In practice 0ppm is definitely not desirable, as well as being totally impossible. At 0ppm, all plant life on Earth would be dead within months due to an inability to do photosynthesis from lack of CO2, followed by all animal life some months later. Fungi and some insects might survive a while longer but within a few years the planet would be ruled by the bacteria again.

    The thing to understand about targets is the inertia of the climate system. Although AGW is currently only about 0.8C (in the lower atmosphere where we live) to date, more warming is already locked into the system. The oceans haven’t warmed to the same degree and when they catch up then another 0.6C rise is expected AT CURRENT CO2 LEVELS. Aerosols (air pollution) in Asia are believed to be masking another 0.5C warming, so if the Asian economies clean up their air quality that would be added as well. So even if we magically stabilised CO2 levels at todays level we would still hit 2C. Other parts of the ecosystem will continue drawing some CO2 out of the atmosphere so this would remove a part of our future emissions but unless we can cut our emission levels rapidly, we are already at the point of seriously overshooting now. We will then need massive sequestration efforts to claw the levels back down again to avoid utterly catastrophic consequences for the world. And not just the Coal Industries wet dream of Carbon Capture & Storage. That is before we factor in other major ‘climate tipping points’ that could escalate the situation in decades to come. To those of you posting here, have you been paying any attention to reports of what is happening in the Arctic? Not melting Glaciers and problems for Polar Bears. Rather Methane release from melting permafrost and release from sub-sea Methane Clathrates. Early warning signs so far, nothing definite. But there seems to be a background noise in all the reports. The ticking of a timebomb.

    Humanity is caught in a very sharp cleft stick. Either we take radical steps to utterly cut CO2 emissions quickly, with real economic and social harm and, for some people in the world, misery and death as a consequence. Or we do less, not enough and too slowly, as is currently the likely outcome, and take the very real risk that Climate change, population growth and a looming world water crisis in agriculure combine to devastate our societies over this century. The consequences of the latter would be every bit as terible as a major Nuclear War, but one played out in slow motion over a 100 year period.

    Our grandchildren may come to pay an appalling price for the nearly 20 years wasted since the Rio climate summit of 1992.

  13. The problem with the stabilisation targets above 350ppm GHGs is that on the current evidence, we may well hit the target without any hint of stabilisation capability by that time.

    Those of us living in the driest state on the driest continent, especially those in the Murray Bridge/Mypolonga region, have just had August temperatures 0.9 degrees (Celcius) above the long term average for maximum day temp, and 2 degrees above the LTA for minimum night temperature. Rainfall was 34mm, which was below the LTA of 38mm. I suspect we’ve just had our hottest August on record. Until 2010, of course.

    All of which makes me feel like responding fairly pugnaciously whenever a local farmer says “when the drought breaks…”. If it is a drought we are in, then a lot of this year’s year 8 students have not known anything else but drought.

  14. @Glenn Tamblyn

    I wouldn’t take issue with anything you’ve propsed Glen …


    … and since there would be no marginal benefit going blow that [i.e. 240ppmv] the rest is moot

    @Peter Wood re: preindustrial CO2 concentration

    In the thousand years prior to 1850 it varied between about 240 and 280 ppmv. With hindsight, we know that 280 was the tipping point, so 240 is probably our margin for error.

    In practice, even if we were to reduce anthropogenic emissions to zero today it’s likely that the atmosphere would equilibrate with the ocean, with the ocean releasing some of its CO2 (and taking up less) slowing the decline in atmospheric concentrations. Of course, we’re not going to do anything of the sort.

  15. @Glenn Tamblyn
    the only thing I’d take issue with is the notion that moving strongly to do what is needed will of necessity cause widespread harm (social/economic). That is only the case if vast sums of money are wasted on stupid expenditure, as is the case now. Of course not wasting the world’s production requires an even greater change than responding sensibly to climate chagne.

  16. Nanks, I’m not sure what you are implying but the problems with ie the ozone within the Sydney Basin is due to bad urban design and outdated technologies. The quicker Australia moves to a cleaner and greener way of life the better.

  17. 1 degree or 2? I know that when things are desperate nothing will stop people putting agriculture ahead of natural ecosystems. We’ll be lucky to stop the rate of increase of emissions going up before we see 450ppm! Actual reductions? Not from Australia. Not any time soon. We are capable of better but not when leaders of government and industry still doubt climate change even exists or that there’s any urgency.
    The ETS may be a start but one that protects the industries it’s supposed to be penalising and that doesn’t impact fossil fuel exports at all? Our mainstream pollies and business leaders don’t get it yet or they’d know the best place for coal is in the ground – and be serious about policies that get that result.

  18. nanks

    My reasons for thinking that the scale and importantly the pace of the changes needed to keep the risks from the combined impacts of AGW, further population pressures and the looming hydrological crisis’s impact on food production is that they cannot be done in economically or socially neutral ways. The flow on benefits in latter decades more than make them worthwhile, but the short term pain will be real. The only way that real and mortal harm to some people in the world could be avoided is if every country in the world and every human being shared the burdens of this change equally.

    Consider the following:

    A recent study released early this year identified that to avoid dangerous warming, the world could only afford to release 500 Billion tonnes more CO2. This is equal to everything we have released since the start of the industrial revolution. However, at expected emission rates now we would reach this volume in just 40 years.

    Compare this with the following fron the International Energy Agency. Their Energy Technology Perspectives 2008 Executive Summary.

    On page 5 graph ES.2 is their projection for what can be achieved with new initiatives under their ‘Blue Map’ scenario, the more agressive of their options. It looks at energy changes using a variety of technologies that they feel may require Carbon Trading cost for CO2 of $200 – $500 USD per tonne. Current Carbon trading schemes are only talking of carbon prices of 10’s of $USD per tonne.

    Look at the area under the graph from 2010 to 2050 even with the measures they discuss. This is over 900 Billion tonnes and at the end of that time we are still emitting 14 Billion tonnes a year. This does not include non energy emissions of CO2 – agriculture, cement making, land clearance, etc. This does not factor in the possibility of various ‘Tipping points’ – Methane from the Arctic, forest dieback, the oceans reducing their absorbtion of CO2.

    The scale of change needed to ensure ‘adequate safety’ from what could be potential End of Civilisation consequences requires us to achieve changes 2 to 4 times greater than this. Such as..

    All fossil fuel power plants worldwide are shut down by 2020.
    Only carbon neutral vehicles are allowed on the roads by 2020
    We have totally replaced the use of Cement by 2020

    and many more changes within 10 – 20 years.

    Consider the capital losses from 10’s of thousands of power plants being shut down before the end of their working lives – Trillions of dollars.
    Consider how long it will take to build 1000’s of Integral Fast Reactors as suggested by TerjeP, can we do it in 10 years? Similarly the deployment of renewable technologies on this planetary scale in that time frame, let alone the massive problems of energy storage needed to complement Wind, Solar etc

    So our only alternative if we went down the path of radical emission reductions to stay within safe CO2 levels would mean things such as the equivalent of war time energy rationing, the end to economic development in the third world and economic catastrophy; The world going onto a war footing for a couple of decades. The chances of the worlds leaders taking us down this path are remote but if they did, do you really see the governments and people of the world acting in a rational and civilised way to share the burdens of this equally?

    Changes of this magnitude discussed by many people in this forum and in many other places are certainly achievable in a 30-40 year time frame and if managed properly would have few negative impacts. But to do it in 10 years would mean taking a wrecking ball to the world and people will get hurt.

    But to take until the middle of the century to make this change means IMHO theat the risks of catastrophy for our grandchildren are simply too high.

    Houston, we have a problem.

    Those years wasted since 1992 may prove very very costly

    So to all of you, when you consider ideas for action, filter them through the basic test of ‘What scale does this need to be done at, what pace, what cost?’

    Quantitave thinking needs to be at the very heart of our response to this problem because in many ways, the lack of quantitative thinking, our preference for looking at the world and our lives in predominantly qualitative ways is at the very heart of how we got into this mess. To anthropomorphise a little; Mother Nature is the Goddess of Numbers. She keeps count of everything, even when we don’t.

    As someone said on another blog ‘May our great great grandchildren forgive us!’

  19. @Ken
    Ken, unfortunately the policies required for us to stop contrubuting to climate change involve those very policies in situ across the world that support globalisation. It wont happen in my lifetime but it needs to happen that countries need to turn inward and no doubt Ill unlease the hounds of hell for saying it…but as Keynes said, the best you can do for the world economy is to look after your own economy and Ill take that as looking after it sustainably..

    As I said I have no hope the seeds of change (at a political and economic level and policy level) will happen in my lifetime…it requires a whole fundamental shift of mindset and perhaps that wont happen until the disaster of climate change is already upon us.

    I dont think, as Fran suggests, it should involve more quantitative reasoning….it becomes apparent to me that with the sophistication of quantitatove methods and pre prgrammed models, numbers can be turned this way and that and there are already too many being trained to accept others assumptions in models and statistical programs without question.

    It needs something more. It needs great normative views and judgements unhindered Im afraid.

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