FEATURE NEWS The climate chairman

Getting hundreds of experts to agree is never easy. Ottmar Edenhofer takes a firm, philosophical approach to the task.

by Quirin Schiermeier

ttmar Edenhofer knows that he some- times has trouble keeping his compo- sure. So when he takes the front seat as Ochairman at international climate meet- ings, he attaches an index card to his desk and glances at it whenever the discussions turn testy. The sign warns: “Don’t lose your temper!” He has needed that reminder often dur- ing his five years as one of the leaders of the Intergovernmental Panel on Climate Change (IPCC), where science frequently comes into conflict with powerful political interests as nations debate how climate is changing and what we can do about it. Those tensions nearly boiled over in 2011, when Edenhofer presided t en Fu h/Lai f / R edux/ E yevine over a session in Abu Dhabi at which delegates

Thors from some 200 nations fought over almost News Feature

THE CARBON AGE arch-conservative part of Bavaria in south Ger- The amount of carbon dioxide that humans have pumped into the atmosphere so far pales in many, he shocked his parents — and prompted comparison to the volume that would be produced if all remaining reserves were burned. the local book seller to declare him crazy —

when he spent his savings at the age of 14 on SOUR C E : I PCC GAS OIL COAL the three volumes of Das Kapital by . 5,000 Reading the German philosopher’s critique of

e the capitalist mode of production didn’t turn

) him into an ardent Marxist, but did spark his 2 2,500 interest in political economics. A couple of years later, the writings of German sociolo-

he atmosp r gist prompted him to ponder the t n I value of science and the difficult relationship 0 between values and facts — problems that are

un d right at the core of any serious debate on the o

stocks (gigatonnes C O role of the IPCC. e g r

h 2,500

t In the mid-1980s, Edenhofer studied eco- n I Carbo n nomics at the University of Munich, Germany, but his academic career soon took an unusual 5,000 detour. In 1987, he joined the Jesuit order in Past and near-future emissions Munich to immerse himself in Western phi- Projected use 2005–2100 losophy and, later, in theology. Soaking up the Cumulative historical use works of Weber, and John 7,500 Fossil-fuel reserves Dewey, he learned to embrace different lines of Identi ed reasoning. In 1991, he also became involved in Estimated undiscovered setting up a Jesuit Refugee Service in Bosnia 10,000 and Croatia during the Yugoslav Wars, and later earned a PhD in economics at the Technical every single sentence in the summary of a The results will inform the political process University of Darmstadt, Germany. report on renewable energies. through a round of global climate negotiations His roots in philosophy are still palpable “It’s an emotional roller coaster,” says Eden- intended to culminate in a treaty in 2015. And in the way that he approaches the climate hofer, chief economist at the Potsdam Insti- as nations continue to disagree over the archi- conundrum.“There is a whole space of mor- tute for Climate Impact Research in Germany. tecture and ambitions of that pact, the IPCC’s ally legitimate standpoints with a view to cli- “Things can get pretty nasty when delegations take on mitigation will come under heavy mate change,” he says one day in May, while play their little games of power, and the chairs scrutiny. The IPCC is charged only with lay- sipping coffee between sessions of a workshop must be prepared to parry attacks. My little ing out the science — and, in the past, critics on climate agreements in Berlin. His boyish reminder to always stay cool and polite has have accused the group’s leaders of overstep- face, framed by round spectacles, grows ani- saved me from fits more than once.” ping the boundary between analysing research mated as he lays out the various perspectives. His temper will be tested again during the and advocating for action. “One might legitimately argue that the fight coming months as he guides his committee — Well aware of that risk, Edenhofer has against global warming is as morally impera- the IPCC’s Working Group III, which looks strived to keep his group focused on a strictly tive as abolishing child labour or slavery. One at ways to mitigate climate change — towards scholarly agenda — and, in so doing, he has might argue — just as legitimately — that pov- the end of its five-year reporting process. A won over some of the IPCC’s past critics. erty and diseases in many parts of the world week-long meeting in late June and early July are more imminent problems that should be in Addis Ababa turned into a marathon for addressed first.” the 232 lead authors of the report, who were “Things can get pretty However, he adds, some perspectives can- faced with addressing more than 16,000 com- not be tolerated. “Denying out-and-out that ments submitted by expert reviewers and gov- nasty when delegations climate change is a problem to humanity, as ernments in response to an early draft. Next some cynics do, is an unethical, unacceptable month, Edenhofer’s committee must send a play their little position.” revised version to governments to prepare for The upcoming Working Group III report April 2014, when lead authors and government games of power.” that Edenhofer is presiding over is a massive, representatives will meet in Berlin to hammer complex tome. A compendium of hundreds out the final report. of scientific papers, it analyses how societies “Ottmar has amazing skills,” says Robert can slow down climate change and reduce its Blueprints for a Green future Stavins, an environmental economist at Har- effects by altering all sectors of the economy, Edenhofer will need to marshall a unique vard University in Cambridge, Massachusetts, from electricity production to transportation to blend of skills, honed during a stint as a Jesuit who did not work on the last IPCC report out building design. The importance of his group’s philosophy scholar and through research on of concerns that it had grown too political. “I work has grown as the greenhouse problem game-theory, as he completes the most sweep- can’t think of anybody better fitted for the job.” has worsened with no political solution in ing compendium yet of technology and policy Philosophy was Edenhofer’s intel- sight. Since the 2007 IPCC report, emissions options that might spare humanity from the lectual refuge early on. Hailing from an of heat-trapping gases have continued to grow worst of climate change in the coming decades. despite a global economic recession. In 2012, The report will lay out a range of scenarios annual emissions of such gases were equivalent — and the costs and risks of each — for trans- OUTLOOK FOR EARTH to more than 50 billion tonnes of carbon diox- forming societies to stabilize greenhouse-gas A Nature special issue on the IPCC ide and reached an all-time high. And, in May nature.com/ipcc203 concentrations at reasonably safe levels. 2013, the concentration of atmospheric CO2

304 | NATURE | VOL 501 | 19 September 2013 FEATURE NEWS crossed the ominous threshold of 400 parts per hammer out an international treaty over the reliability of economic models used to forecast million (p.p.m.) for the first time since human next year. the future. They rely on macroeconomic equa- beings appeared on Earth. When the last round of IPCC Assessment tions and assumptions that are often thwarted The report will provide a range of scenarios, Reports came out in 2007, the body came under by real-world developments. Economists and cost estimates, for stabilizing atmospheric fire for including a few claims that lacked strong are well aware that although the models can CO2 concentrations at 450 or 550 p.p.m.. It will scientific support; in one high-profile gaffe, anticipate broad trends, they have no ability make it clear that all realistic stabilization sce- Working Group II uncritically repeated a base- to forecast disruptions such as major financial narios are decidedly at odds with current emis- less assertion that Himalayan glaciers would or political crises. sions trends. In fact, if one factors in methane, disappear by 2035. Edenhofer has pushed his And great uncertainty remains over how nitrous oxide and other warming gases that are own working group to thoroughly overhaul its nations will tackle climate change. How much governed by the 1997 Kyoto Protocol climate procedures for evaluating scholarship to avoid will countries cooperate? To what degree will treaty, the combined concentration has already such embarrassing blunders in his report. In they rely on nuclear power? How quickly will surpassed the equivalent of 450 p.p.m. of CO2. particular, he has reduced the use of ‘grey’ be deployed and at what As a result, stabilization plans must allow literature — information not subjected to peer price? Beyond those near-term concerns, for nations to temporarily overshoot a target review, such as reports from environmental researchers must also grapple with more dis- before concentrations might start to subside. groups, governments and companies — to a tant potential mitigation strategies such as The report will also make clear that the minimum. capturing and storing carbon on a massive problem will only grow worse without action. scale, or large geoengineering projects aimed Known hydrocarbon reserves still buried in at rapidly staving off warming. the ground may contain up to four times as “Science cannot, As Working Group III tackles such uncer- much carbon as has been released into the tainties, it will also wade into an increasingly atmosphere since the onset of the Industrial and can’t be expected contentious debate about the benefits of cre- Revolution (see ‘The carbon age’). ating biofuels from plants and bacteria. Since But in line with the IPCC’s mandate — to, provide simple the IPCC’s 2007 report, a fast-growing body which requires the group to be policy-neutral of literature has split over whether the indirect — the assessment of Working Group III will yes or no answers.” effects of growing crops for fuels do more harm avoid promoting certain mitigation options than good to the climate. over others. Maintaining that distance will be And, perhaps drawing on his background Fears that excessive bioenergy production a crucial test of Edenhofer’s leadership. as a philosopher and theologian, Edenhofer might cause food shortages make the debate “The IPCC is a scientific body whose task is has also broadened the scope of the IPCC’s even fiercer. “Clearly,” says Edenhofer, “this is to compare and review the relevant literature,” mitigation working group to give ethical con- one of the most controversial issues we’re deal- says Stavins. “Unfortunately, in my view, the siderations greater weight. For the first time, ing with. By now, debate over bioenergy has IPCC has in the past overstretched its man- professional philosophers have been invited to outstripped controversy over nuclear energy.” date. It has become too political — and that contribute to the report’s opening chapters on The IPCC, he says, will summarize the pros hasn’t done it and the field any good.” Stavins equality, risks and sustainability issues, which and cons as authoritatively as scientific knowl- feels, for example, that prominent IPCC mem- set the scene for more technical sections. edge allows. bers transgressed by lobbying for green poli- But even as it details the various options cies such as emission cuts and carbon taxes. that nations might take, the report will not Teary Finale Edenhofer is keen to steer clear of such ter- take sides, he stresses — because that involves Edenhofer is convinced that the IPCC is bet- ritory: he often compares the task of the IPCC decisions based on values and priorities that ter placed than any other group to address to that of map-makers rather than to that of fall to elected officials. “Science cannot, and such thorny issues, because the final reports political advisers. But he also knows that the can’t be expected to, provide simple yes or no are vetted not only by scientists but also by report, by necessity, will weigh in on politically answers,” he says. political appointees from member nations. charged issues such as nuclear power, biofuels To tread that neutral line, Edenhofer will No purely science-led exercise could possibly and geoengineering. When the report’s sum- have to control his own strong opinions, have equal weight, he says. Although some mary for policy-makers — its most-read and formed during his years as an economist and scientists have started to question the utility of most-disputed section — goes up for debate climate-policy expert. He favours cap-and- the IPCC, especially its drawn-out procedures, in April, the fighting among diplomats and trade schemes, for example, over a direct Edenhofer says the process should continue. scientists will be even tougher than it was in as the most effective way to cut The “miracle” of the IPCC, as he puts it, is that past sessions. Together with his Cuban and emissions and promote climate-friendly it forces governments to deal seriously with Malian co-chairs, Edenhofer will have to see, as innovation. And he is adamant that the global science. patiently as his nature allows, that the haggling transformation to a low-carbon economy can- “To be able to engage and criticize our work, over the tiniest words proceeds in a civilized not be achieved — no matter what goals key governments do need to carefully read our and productive manner. emitters might commit themselves to — with- reports,” he says. “Here’s a unique mechanism He faces the date — his last as an IPCC offi- out substantially increasing the use of renew- for bringing science to the very level of govern- cial — with a mixture of anxiety and gladiato- able energy in all sectors of the economy. ment leaders.” rial anticipation. “Where I grew up, the boys In spite of his own opinions, he has focused As he steers his group through that process, were always ready for a fight,” he says. “I’m not on delivering an unassailable product. “Ottmar he will make frequent use of his desktop index like that — but trust me, I do know when it’s is keen to get the best science for the next IPCC card. But he has faith in the process. “When time to thump on the table.” report, which he wants to lift to a new level of everything is said and done, and when even The stakes are mounting on his group’s quality,” says Massimo Tavoni, deputy coordi- the most hard-boiled negotiators have tears in report. With its analyses of low-carbon energy nator of climate-change programmes at the Eni their eyes, it is the cause of science — and not options and different policy paths towards Enrico Mattei Foundation in Milan, Italy. power interests — that has the last word.” ■ stabilizing greenhouse-gas concentrations, Edenhofer is also ready to acknowledge the report will be an important contributor to the limits of knowledge in his field. The most Quirin Schiermeier is a reporter for Nature the upcoming negotiations as nations try to important uncertainty, he says, concerns the in Munich, Germany.

19 September 2013 | VOL 501 | NATURE | 305