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  October 4, 2017

New Study Says Extreme Climate Change Preventable


Oxford University climate scientist Richard Millar says right-wing climate deniers have misrepresented his research, and that the 1.5-degree Celsius warming limit is not yet a geophysical impossibility
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biography

Richard Millar is a climate physicist by training and is interested in how the insights from the latest climate science can be successfully embedded in effective climate policy. His research spans the physical and economic consequences of climate policy and aims to investigate pathways for achieving global climate goals.


transcript

D. LASCARIS: This is Dimitri Lascaris for the Real News Network. The stated goal of the Paris Climate Agreement is to keep the global temperature rise this century well below two degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius. But more and more climate scientists have been saying that the 1.5-degree Celsius goal is now unrealistic. A new study, however, published in Nature Geoscience, concludes that the 1.5-degree Celsius warming limit is not yet a geophysical impossibility. That study is entitled, 'Emission Budgets and Pathways Consistent with Limiting Warming to 1.5 Degrees.' As the Real News has documented in our feature-length documentary, 'Trump, the Koch Brothers and Their War on Climate Science,' the climate change denial machine is a well-oiled multimillion dollar operation designed to prop up the fossil fuel industry by sowing doubts about climate science. Not surprisingly, the denialists have seized on the Nature Geoscience study to sow doubts about climate change. But the two scientists who authored the study are fighting back and one of them is joining us today to discuss the misuse of their study.

Dr. Richard Millar is a climate physicist and an Oxford Martin fellow at the University of Oxford. Dr. Miller and his co-author, Miles Allen, recently penned an op-ed in the Guardian in which they denounced the misuse of their study. The Guardian op-ed was entitled, 'When Media Skeptics Misrepresent Our Climate Research, We Must Speak Out.' Dr. Millar joins us today from Oxford in the United Kingdom. Thank you for joining us today, Dr. Millar.

RICHARD MILLAR: Thanks, no problem.

D. LASCARIS: First I'd like you to discuss your study. What did you conclude about the feasibility about keeping the global temperature increase to less 1.5 degrees Celsius above pre-industrial levels?

RICHARD MILLAR: What our study did was to look at what we call the carbon budget for 1.5 degrees, which is essentially how much CO2 emissions the globe could emit between now any time in the future and still have a good chance of keeping warming below the 1.5-degree threshold. These numbers that have been used in many analyses for what the remaining budget might be to have a good chance of keeping below 1.5 degrees have been very, very small. As maybe as small as a few years of emissions at present day emissions rates. What our study does is look again at this question of exactly how big is this carbon budget? Or how big might it be to limit warming beneath 1.5 degrees? What we find is that it might be a little bit bigger than some of these previous budgets. Maybe as much as 20 years at current emissions rates which is the total amount of carbon as if the globe reduced its emissions from where we are today to net zero across the whole globe in about 40 years or so.

While we find that 1.5 degrees is not yet impossible, geophysically impossible, it's still a really large challenge in order for the global economy to be completely decarbonized, to have net zero emissions into the atmosphere on these kind of time scales. It's a real challenge now to the policy makers if they're serious about achieving this goal that they set for themselves in Paris then there's substantial actions that would need to be implemented by policy makers around the world for this 1.5 degrees to actually still to keep remaining a geophysical possibility into the future.

D. LASCARIS: You said your study examined what we need to do to have a good chance, those were the words you used, to remain within that limit. How do you quantify a good chance? What does that mean exactly?

RICHARD MILLAR: That's a good question. What we've used in the paper, which is a number that's often used in analyses of climate policy is have a two-thirds chance of staying below 1.5 degrees. That's a value judgment, maybe we're individuals saying, no, that's not a good enough threshold to be sure that we stay below 1.5 degrees, maybe we want a higher threshold which would be a lower carbon budget that what we report or maybe alternatively people say, maybe a 50/50 chance of 1.5 is sufficient for me. Our numbers are centered around this two-thirds below probability of staying below 1.5 but that's inherently a value choice.

D. LASCARIS: Please tell us a little bit about the methodology of your study. What did you do that was different from past studies and that led to this somewhat different conclusion that you've reached.

RICHARD MILLAR: What we've done is to look carefully at this ensemble of computer models of the climate system that we have for thinking about these questions. These are called earth system models and they simulate the responses of the fundamental physics of the atmosphere and the ocean and the carbon cycle to changes in CO2 concentrations to try and understand things about present, past and future climate. What we find is that when we're thinking about warming thresholds that are really close to today's levels, for instance the 1.5-degree threshold, we're about, around two-thirds of the way there 'cause we're about one degree or so of human created warming to date. When we think about thresholds that are so close to today that we have to really think about how we can better use this modeling ensemble to tell us about what pathways might be compatible with this goal.

What we found is that if we correct for a few small bias in terms of how these very complex computer models simulate warming for a given amount of CO2 to better capture exactly where we might be today, we find that taking account of these small bias does actually matter a little bit for thresholds so close to where we are today in terms of the amount of carbon that might be left. That was one avenue that we used in the paper to examine this question, we also used a couple of different avenues, we used a simple climate model which is just a couple of equations that represent the overriding physics of the climate and carbon cycle system and with that we're able to sample quite important parameters determines how much warming might be expected for a certain amount of CO2. What is the exact contribution of methane forced into the climate change we see today and into the future. To sample those uncertainties. Using that procedure, we come up with a roughly similar answer to using the complex climate models that's an additional avenue of evidence that we investigated in the paper.

D. LASCARIS: In your Guardian op-ed, you and your study co-author wrote, "Our climate paper underlined that strong action towards the 1.5-degree Celsius Paris goal is perhaps more valid than ever. But reading some of the media coverage you might think the opposite was true." How is your study being misquoted and misused and who are the principle culprits in the misuse of your study?

RICHARD MILLAR: What we see going on is that a lot of the issues that are discussed in this paper, it's actually quite a technical paper and talk about warming per ton of cumulative CO2 emissions and now the way these earth systems models actually work is that emissions are actually an output of the model. We run the models with telling it how much carbon dioxide was in the atmosphere in a given year and the models calculate what warming that gives you and what cumulative emissions that might be compatible with that. Because those are two outputs and because these are really complex models, we expect there to be a certain amount of discrepancies between the real world and these models.

As I said, for 1.5 degrees these small effects that are totally expected in constructing a computer model that's complex enough to capture the whole earth system, these are expected but we need to account for them. The way that this has been taken in some spheres is to say that what our paper was saying was that these models are predicting the wrong amount of warming for a given amount of carbon dioxide in the air. That's not what our paper was about which is quite a subtle difference but it's an important one for talking about predictions of global warming into the future and our fundamental, the magnitude of how much CO2 emissions affect the climate system from today onwards within our modeling and within our study it's perfectly consistent with the evidence that's been presented through the intergovernmental panel on climate change and through many other studies in the literature in the past.

D. LASCARIS: I understand there has been some push back from the scientific community, those who continue to be of the view that we can't realistically meet the 1.5-degree Celsius goal given the amount of greenhouse gases that have already been emitted. What is the essence of their critique of your study and how do you respond to that critique?

RICHARD MILLAR: There's a couple of things being discussed like science is a continuing conversation these things always start interesting discussions and I'm sure they'll be further discussions in the literature coming out of these but they centered around a couple of different things. One is, what is the exact right level of human induced warming in the climate system today? It sounds like a simple question to say, well what is the present-day temperature? Do we know it? Well can't we just measure it? Yes, we can, but we don't have a complete measurement record absolutely everywhere in the world and so there are interesting questions about well something like the Paris agreement. Should we use just observational temperatures and add them up and get a global temperature from just where we actually have real measurements of the data? Or should we try and use clever statistical techniques to infill in some of the gaps in where we can measure temperatures in particularly there are gaps over the Arctic?

Our paper makes a certain choice in that we use data sets that were available at the time of the Paris agreement. Data sets that directly informed the negotiators in terms of when they were deciding, these are the present-day planet impacts for this amount of warming and to make a decision about what impacts might be at 1.5 degrees, at two degrees and whether that's something that they want to commit themselves to. Maybe a different definition will be used in the negotiations in the future but at the moment that's not clear and it really falls to the climate negotiators to define what in the metrics they're going to use to measure their progress through this agreement.

The other main area that discussion is taking place around is whether there is locked in warming, essentially. Locked in warming that we don't see today but we're committed to from past emissions. Now, actually in fact, the amount of warming that we're committed to from past CO2 emissions, from past carbon dioxide emissions, is actually very small. In the completely hypothetical scenario, if we could stop emitting tomorrow, CO2 induced warming would not change much from what it is today. Temperatures would stay roughly flat for centuries following. CO2 induced warming is very permanent but it's very much, our future emissions that control future warming.

D. LASCARIS: But there is some additional warming locked in. What do you quantify that to be?

RICHARD MILLAR: There's not really much. Our best estimates are that probably it is quite small. It's potentially even negative because CO2 induced warming if we were to bring our emissions to zero, we'd expect based on the scientific literature that's out there, that we would actually wouldn't see much more warming once we stopped emissions. Now there are other things affecting the climate system. There's methane, there's particles, aerosol particles that come from burning coal that actually have a cooling effect. Whether we stopped emitting, whether we get any more warming at all would be in some level determined a little bit by the balance between how much aerosols are cooling us versus how much methane is warming us. The latest estimates indicate that would be about equal. We probably expect if they were both reduced toward zero at the same rate then there to be again, little committed warming going into the future.

D. LASCARIS: Is there disagreement to, significant disagreement in the scientific community about how much additional warming is locked in?

RICHARD MILLAR: I wouldn't say so, no. It's very clearly summarized in the last assessment court of the IPCC that CO2 induced warming is very small. There's obviously uncertainties about aerosol rates enforcing and if the aerosol, the amount of cooling potential of aerosols is actually quite large then there could be some unmasking of warming that we might see. But our best estimates of rates enforcing at the moment indicate that that's probably balanced by the methane warming. As both of those change into the future exactly what happens is going to depend on the precise balance of methane warming and aerosol cooling. A lot of scenarios actually show that those two effects canceling out about today but also continuing to cancel into the future. Our best estimates are probably that there's little committed warming if we stopped emissions today.

Of that doesn't mean there's not a locked in emission from the energy sector. We're not going to just stop emitting straight away tomorrow. In reality, there are power plants built and people aren't going to want to turn off those power plants instantaneously tomorrow. That probably wouldn't be desirable for us to just shut everything down instantaneously. There's an economic lock in of emissions but therefore a lock in at warming if we do run those power plants to the end of their lifetimes but a physical lock in is actually quite small.

D. LASCARIS: Recently a study called, 'Importance of the Pre-Industrial Baseline for Likelihood of Exceeding Paris Goals,' that study examined the implications of different choices of the pre-industrial baseline on the likelihood of exceeding the two temperature thresholds in the Paris Accord and the study seemed to suggest that our carbon budget is smaller than generally believed. Can the results of your study be reconciled with those of the study co-authored by Michael Mann?

RICHARD MILLAR: Yes, absolutely if there were different choices for what the pre-industrial baseline is then that will affect remaining budgets as was pointed out in that paper. As I mentioned earlier, it's also important to acknowledge the context of the Paris Agreement was made in. The governments and the negotiators had information about warming today, impacts today and impacts at 1.5 degrees and two degrees. These were set against a specific baseline which pretty much was the baseline used in the IPCC fifth assessment report. Which was an 1850 to 1900 baseline. While this is an interesting academic discussion, I'm not 100% sure how directly relevant it is to the Paris Agreement process because in some ways this decision has already been made by the agreement in terms of the information that it was using in terms of impact assessments of 1.5 degrees and two degrees relative to this 1850 to 1900 baseline and that's an important thing that we have to bear in mind that this is not just a scientific project this is also it's a political and international policy project. That baseline was actually very much more consistent with the one we used in our study.

D. LASCARIS: Lastly, let's talk about the political commitments that have emerged from the Paris Accord and in light of your new study the signatories to the Paris Accord which included all the major emitters, agreed to make certain commitments regarding emission reductions. In light of your study, are the current emission reduction commitments of the major emitter adequate to achieve the goals of the Paris Accord? And how much warming can we anticipate if those commitments fulfilled but not exceeded?

RICHARD MILLAR: That's an interesting question and it comes down to one recognizing that the commitments in themselves don't actually get us any amount of warming because what we do understand from the science is that warming only stops when CO2 emissions stops. The pledges from the Paris Accord were to reduce emissions a bit from baseline but in order to stop warming, whether that's at 1.5 degrees, two degrees, three degrees or any other threshold, we still need to get emissions to zero. At the moment the pathways that we discussed in our paper coming out of where we are today in trying to meet these 1.5 degrees, even the pathways that have the smallest emissions reductions in the near term and therefore the most steep ones in the medium to long term because they all need to get to zero by the time these budgets are used, even those pathways would still require a strengthening of the Paris budgets by at least 10% and for us to actually to have a plan to eliminate net emissions of carbon dioxide into the atmosphere from the global economy.

We actually discussed in the paper how in order to offset some of the risks that rates of reduction might prove to be socially, technologically, economically and politically infeasible that actually increased ambition in terms of how much we can reduce our emissions in the near term, what's pledged for 2030 as part of the Paris process, would really help offset some of these risks of requiring infeasibly rapid reductions in emissions after 2030 if we still were to meet this 1.5 degree carbon budget. I research is very clear that increasing near term ambition would help address many of these feasibility dimensions of actually sticking to this still pretty tight carbon budget.

D. LASCARIS: This has been Dimitri Lascaris speaking to Dr. Richard Millar of Oxford University, regarding a new study examining the feasibility of the 1.5-degree Celsius target under the Paris Climate Accord. Thank you for joining us today, Dr. Millar.

RICHARD MILLAR: Thank you very much.

D. LASCARIS: And this is Dimitri Lascaris for The Real News.



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