Limiting global temperature rise to 1.5C has long been the goal of developing countries and those most at risk from climate change. Since becoming enshrined in the Paris Agreement last December, the 1.5C goal has come under increased scrutiny and examination.
How do climate impacts at 1.5C and 2C compare? How fast would the global economy need to decarbonise? Is the amount of “negative emissions” required for either limit feasible? Expectation is heavy that a special report by the Intergovernmental Panel on Climate Change (IPCC), due in 2018 at the behest of the United Nations, will answer all these questions.
So is the scientific community rising to the challenge or feeling the pressure?
Ahead of a major conference in Oxford this week, Carbon Brief has been talking to climate scientists, economists and public health experts about how the spotlight on 1.5C has changed the way they work.
Degrees of separation
Back in August, the chair of the IPCC, Dr Hoesung Lee, told scientists at a meeting in Geneva that they bore a “great responsibility” in making sure the special report on 1.5C meets the expectations of the international climate community.
Dr Rachel James, a research fellow at the University of Oxford’s Environmental Change Institute, explains how this has been interpreted by scientists. She tells Carbon Brief:
The comparison with 2C is not technically what the Paris Agreement called for, even though that’s how it has been perceived, says Prof Myles Allen, professor of geosystem science at the Environmental Change Institute and a convenor of this week’s conference. He tells Carbon Brief:
Comparing impacts for crop production, extreme weather and sea level rise, for example, at different global temperatures means flipping on their head the way climate projections are traditionally constructed. Picking a “tolerable” temperature limit first and investigating impacts and pathways later isn’t how scientists have always done things, says Prof Jonathan Gregory, professor of meteorology in the National Centre for Atmospheric Science at the University of Reading. He tells Carbon Brief:
Understanding the effect of half a degree extra warming presents a specific challenge, says Allen. He tells Carbon Brief:
With their group at Oxford University, Allen and James are working on a new project dedicated to tackling these new questions. The HAPPI project (Half a degree Additional warming, Prognosis and Projected Impacts) is an international effort, listing more than 35 different institutions worldwide as collaborators. James tells Carbon Brief:
Another shift within the climate change research community is that, until recently, most work has been looking at impacts at higher levels of warming. James tells Carbon Brief:
Understanding the risk of half a degree of extra warming brings other scientific challenges, including the need to narrow the uncertainty over how much warming a given amount of carbon produces, known as the climate sensitivity, and the role of short-lived gases, such as methane.
Such questions are putting greater pressure on scientists to produce numbers, rather than to refine understanding, says Prof Ted Shepherd, Grantham professor of climate science at the University of Reading. He tells Carbon Brief:
A good example of this is the need to pin down the “threshold” for the Greenland ice sheet, says Gregory, who, as well as being a professor of meteorology at the University of Reading, is an expert in ice sheets and sea-level change. He tells Carbon Brief:
Once global temperature change exceeds a certain point, the Greenland ice sheet would disappear, taking centuries, but, ultimately, raising global mean sea level by seven metres. The problem is that we don’t know where the threshold is exactly, Gregory tells Carbon Brief:
A big question surrounding the IPCC’s special report on 1.5C is how much of the new wave of research will be ready in time? Any scientist wishing their research to be included will need to submit it to a peer-reviewed journal by October 2017, and have it accepted for publication by April 2018.
Such a short timescale is not unusual for very small questions, but this special report request is a different, says Dr Daniel Mitchell, a researcher in the University of Oxford’s Environmental Change Institute and the coordinator of the HAPPI project. He tells Carbon Brief:
The urgency has caused some problems, not only with publication times, but also with getting the funding to do the work, Mitchell adds:
Another option is to apply for new funding, but that, too, takes time. Shepherd tells Carbon Brief:
Though the wish list for potential topics to include in the special report is long, what gets discussed depends on what is published between now and the publication deadline, says Allen. This date is, he says, “frighteningly soon” from the point of view of an academic.
On that front, this week’s 1.5C conference in Oxford has a very clear objective, Allen tells Carbon Brief:
Academic research does not normally operate on a timescale, says Allen. But it’s not unwelcome.
The spotlight on 1.5C seems to have given the climate policy community a renewed vigour, as well as climate scientists, says Ajay Gambhir, a senior policy fellow in climate change mitigation at the Grantham Institute for Climate Change, Imperial College London. He tells Carbon Brief:
The need to remove carbon from the air using negative emissions technologies is a topic receiving quite a bit of attention since the shift to more ambitious climate targets. Gambhir explains:
While the need for negative emissions has got more airtime since Paris, some scientists have been talking about the largely theoretical technologies for a long time, says Allen. They have always been necessary if we wish to stabilise global temperature at any level, he notes.
Is the 1.5C goal feasible, given the amount of negative emissions required? Yes, says Allen, but it comes with a long list of boxes that need ticking all at the same time. He tells Carbon Brief:
With such a huge caveat, is this a useful definition of “feasible”? Gambhir’s work involves coming up with various different metrics for expressing “feasibility”. He tells Carbon Brief:
Carbon Brief analysis suggests there are about five years’ worth of current emissions left before the budget for 1.5C is blown, meaning that never crossing the 1.5C threshold is now nigh-on impossible. But this isn’t a reason not to try, thinks Mitchell says. He tells Carbon Brief:
As well as technical constraints, there are, of course, social and political aspects of feasibility, too. Gambhir says:
The question of how fast a transition society could tolerate is important in public health, too, says Nick Watts , executive director of the Lancet Countdown: Tracking Progress on Health and Climate Change. The focus on 1.5C has prompted mixed reactions in the medical community, he tells Carbon Brief:
While past studies show the benefits for public health of climate mitigation, they haven’t necessarily looked at the difference of an extra 0.5C. He tells Carbon Brief:
With so much to do and a short timeline to do it in, is there a risk the IPCC’s special report will be incomplete? That’s not a risk, it’s a certainty, say Allen. He tells Carbon Brief:
The challenge for scientists is to answer the question as best they can in the time frame they have been given. But it will be important to be upfront about what’s left unanswered, says Mitchell. He is hoping the level of “quality control” doesn’t drop in the haste to get more papers submitted. He tells Carbon Brief:
In other words, scientists are mindful of the careful balance between being fast in order to be policy-relevant and not compromising their scientific integrity. But whatever the eventual scope of the IPCC special report, the future of the 1.5C goal won’t be decided on the strength of it alone, says Shepherd. Past lessons teach us that much, he tells Carbon Brief:
Any research that doesn’t make it in time for the special report will be hoovered up by the IPCC’s next big assessment report, due in 2021. As with other reports and other topics, this will essentially update and refine the last instalment with new knowledge. So while the 1.5C special report is undoubtedly important and science is bending as best it can to meet its demands, simple logistics mean it’s unlikely to tick all the boxes.
Carbon Brief journalists will be covering the 1.5C conference in Oxford this week. Follow us on Twitter for updates, or email us via firstname.lastname@example.org if you have any questions you would like us to put to the attendees.