The Case for a Climate Goal Other Than Two Degrees Celsius

Scientists and climate negotiators have largely agreed that limiting global warming to no more than 2 degrees Celsius is an important goal. But political scientist David Victor disagrees, arguing that the benchmark is too simplistic and should be abandoned in favor of other indicators.

When international delegates meet in Paris next year to negotiate a new global climate agreement, they’ll be aiming to keep global average surface temperatures from rising more than 2 degrees Celsius beyond pre-industrial levels. That threshold, which had long been discussed and debated , was formally agreed to during the 2009 talks in Copenhagen, and it is seen by many as the best way to avoid the very worst impacts of climate change.

David Victor

But that goal, David G. Victor says, is both scientifically and politically misguided. In a recent commentary in the journal Nature that has sparked controversy, Victor, a professor of international relations at University of California San Diego and a lead author with the Intergovernmental Panel on Climate Change (IPCC), maintains that not only is the 2-degree goal now unattainable, the focus on it has “almost unwittingly played into the hands of the so-called climate denialists.”

In an interview with Yale Environment 360 contributor Diane Toomey, Victor lays out his criticisms of the 2-degree threshold, contending it has failed to position policy makers to take serious action on mitigating global warming, and he discusses the “basket of indicators” that he and his co-author, Charles Kennel, director emeritus at the Scripps Institution of Oceanography, are suggesting be used instead.

Yale Environment 360: When did your reservations about the 2-degree Celsius benchmark first emerge?

David G. Victor: I’ve been nervous about using a single indicator of planetary health for a long time. In the 2000s, we had tremendous growth in emissions, not much in the way of policy efforts to control those emissions, and so when we got to the last IPCC report we were asked by the diplomats to study the feasibility and cost of meeting widely discussed goals, not just 2 degrees — also 1.5 degrees. And so we looked at the scientific literature in that area. And I think the literature is pretty clear that under highly idealized circumstances — like all countries begin cooperating pretty much immediately even though they haven’t done that so far, all technologies are available globally pretty much immediately, markets work perfectly efficiently — under those kinds of assumptions it still might be possible to cut emissions and stop warming at 2 degrees.

But what’s interesting in the scientific literature in that last few years is that there has been much more attention to imperfections in those assumptions. So the idea that some technologies might not become available when you need them, some technologies might be limited, like nuclear power or renewables. And when you start to put those constraints on the models, what they show pretty clearly is that the cost of controlling emissions, making deep cuts in emissions, and stopping warming at 2 degrees is much higher. And in fact many of the models, when you add realistic assumptions to them, can no longer compute in a way that cuts emissions globally and stops warming at 2 degrees.

e360: So the 2-degree goal may not be achievable, but you and your and co-author, Charles Kennel, have other criticisms of it. What are those?

Victor: We have two main concerns about the 2-degree goal. One is about the feasibility of meeting it, which we just discussed. And the other one is whether the 2-degree goal is the right way to measure human stress on the climate system. Our argument is that it’s not a great measure. And that’s because globally averaged surface temperature responds to a lot of different factors. And in some sense I think the scientific community and the diplomatic community have almost unwittingly played into the hands of the so-called climate denialists by focusing so much on global average surface temperatures when there are all kinds of factors that affect it. …

My concern as a political scientist is that what governments need are goals that have some plausible and immediate — or at least reasonable — connection to things that they actually do, and if the goals are so far removed from things that they can actually do and actually will do, then the goal really serves no useful strategic purpose. And that, at the end of the day, is the real crux of the debate here: How do you set goals that are useful strategically for getting governments to coordinate their national policies?

e360: You suggest that the atmospheric concentration of carbon dioxide is a better benchmark to pay attention to. But since there’s uncertainty regarding the sensitivity of the climate to those concentrations, wouldn’t this be problematic as well?

Victor: I think it actually works [in] exactly the opposite direction, precisely because we don’t know with precision the level of climate sensitivity. If you set goals in terms of global average temperature, then you need to feed that through the uncertainty of climate sensitivity to get the concentration of greenhouse gases — not just carbon dioxide, but the whole range of greenhouse gases. And from there you work backwards and you get radiative forcing which is the measure of how much heat imbalance is caused by these greenhouse gases and then from there you get actual policies.

“I think it’s … important for all of us to recognize that we do not know what the right basket of vital indicators is.”

And in fact when you look at the scientific literature, it’s an interesting disconnect because the modelers who study emissions and how to control those emissions are generally much more comfortable setting goals in terms of carbon dioxide and other greenhouse gas concentrations because that comes more or less directly out of their models and is much more proximate or more closely connected to what humans actually do to screw up the climate in the first place, which is emit these greenhouse gases.

e360: What other indicators would you want climate negotiators to focus on?

Victor: We suggest in the article that there are some other indicators that look much more promising. One of them is ocean heat content. There have been advances in the last decade or so in measuring ocean heat content. And you see the human fingerprint on that much more clearly. So it is a better measure of human stress. We suggest that concentrations of greenhouse gases, as we’ve just discussed, is another indicator. We talk about temperatures in high latitude areas, like the Arctic, because, as a general rule, high latitude areas are much more sensitive to human stress than the global average. So what you really want is a good canary in the coal mine and the high latitude areas are canaries, whereas the global average hides real stress.

And then we also say that we should be developing indicators of extreme impacts and extreme events. There have been a couple of studies in this area which are really interesting and promising, in that we can start to measure the number of extreme events and hazards from those extreme events. The reason we care about that is because that’s ultimately what causes some of the largest impacts on humans and nature and so it’s what people care about and what people are therefore willing to spend money on to try to avoid.

But I think it’s important for all of us to recognize that we do not know what the right basket of vital indicators is. There’ve been some efforts over the years. If we work hard on this problem right now, we are not going to have a better basket ready to go by late next year when the big meeting in Paris on climate change happens. And so one of our policy recommendations is that in addition to looking beyond 2 degrees, the diplomats should include in their discussions leading up to Paris a clear agreement to come back to the scientific community in a technical conference and ask [them] for new indicators.

e360: What does that say about what can be accomplished in Paris?

Victor: Well most of what Paris is about doesn’t really depend on indicators. There’s been this view that the climate problem is so severe that we all need to buckle down, get everything done right now, and if we don’t get it done between now and whatever the next big meeting is that there will be a catastrophe. And I am one of many who wish that governments would do a lot more in this area.

But the reality is it’s a very long-term process. And so what happens in each of these two, three-year cycles between giant conferences is that governments chip away at the problem. I am actually much more optimistic about the prospects for this round of negotiations than I have been for a long time, partly because the negotiations are organized in a way that is better connected to reality. They are organized around flexibility, around engaging as many countries as possible, especially the big emitters from developing and developed countries alike, and they are organized around what might be called a bottom-up process in which individual countries make pledges and they reveal what they are willing and able to do on their own. And that’s going to be slow and messy. It’s not going to be enough to stop warming at 2 degrees. But it’s better reflective on how you get real things done in international diplomacy.

e360: Some critics have said that you’re being too optimistic about what sort of indicators the public — and even climate negotiators — can really apprehend and turn into policy. How do you respond to that?

Victor: I think that view is totally crazy and totally disconnected from any reality on this planet. Policy makers and, in fact, [much of] the public are used to dealing with complex material. Heads of state get briefings all the time about threats of terrorism that include huge amounts of technical information. We coordinate economic policy. We coordinate trade policy. These are fantastically complex areas of policy coordination that involve indicators that are much more complex than what we are talking about in this article. That’s a sign of getting serious about the problem.

“Climate is one of the most difficult, if not the most difficult major problem the world has faced.”

e360: On the 2-degree Celsius goal, you wrote: “It has allowed some governments to pretend that they are taking serious action to mitigate global warming, when in reality they have achieved almost nothing. ” Elaborate on that if you will.

Victor: When you look closely at what’s actually happened in terms of emissions controls, it’s shocking how little has actually been accomplished worldwide. And right now there is a huge imbalance between the actual level of emissions, and actions that are likely in the next 10, 20, 30 years. …

There’s no question some governments have tried to do a lot. But when you look at the big impact on emissions so far, they are mostly out of luck and accident as opposed to policy. Look at the case in the United States, for example, where we’ve had a big reduction of emissions thanks to the shale gas boom. And some of it is clever accounting, so the industrialized countries are benefiting from the ability to import products from emerging economies, principally but not exclusively, and our current systems of emissions statistics don’t count the emissions from those products. So that has a huge offsetting effect on the actual reduction of emissions that we’ve achieved here.

Climate is one of the most difficult, if not the most difficult, major problems the world has faced, because the costs of action are apparent and they affect interests groups that exist today, [and] the benefits are distant and seem to be uncertain. … We as humans, and especially at the international level, aren’t very good at dealing with problems like this. And I’m worried that if governments keep saying what they’re doing is organized at stopping warming at 2-degrees, then the people who are actually on the front lines of climate change — coastal cities, farmers and so on — are going to think about preparing for a world that’s 2 degrees warmer, when in reality the evidence seem to suggest they should be preparing for a world that [has warmed] a lot more than 2 degrees.

e360: But wouldn’t using other indicators allow for the same pitfalls?

Victor: Absolutely. But that’s why at the same time that you set indicators that are better connected to the actual human stress on the climate system, you also have to set indicators that are more realistic for what we’re actually going to do, because that will then send signals across the rest of the economy and the rest of the world as to what people need to prepare for.