On Tuesday, the Intergovernmental Panel on Climate Change (IPCC) released the third part of its Assessment Report on the current state of knowledge concerning climate change. Professor Hermann Held, Chair of the Research Unit “Sustainability and Global Change” (FNU) and Principal Investigator at the Cluster of Excellence CliSAP, was on of the report’s Lead Authors. We spoke with the physicist and economist about the economic aspects of climate change, important innovations in the latest report, and on how different disciplines can be combined with regard to our climate.
CliSAP: Mr. Held, several hundred researchers worked for several years on preparing the recently published third part of the Assessment Report, without pay and on top of their normal duties. The result was a work over two thousand pages long. Was it worth it?
Held: The Intergovernmental Panel on Climate Change, or IPCC, determines the difference between what we concretely know about climate change and what remains controversial. That’s enormously important, because it’s the only way to escape the unfortunate situation of talk-show formats: one expert claims one thing, the other claims just the opposite. What gets ignored in the process is that some theories have almost no backing whatsoever in the scientific community. Though the Assessment Reports don’t tell people what to think, they do provide clarity on which statements are sound and reliable and which aren’t.
CliSAP: The first part from September of last year focused on the scientific basis of climate change – for example, on how much atmospheric temperatures rise at specific levels of CO2 emissions. The second part deals more with the consequences for human beings and nature, and with potential ways of adapting. What’s the latest part all about?
Held: In Working Group III we point out ways of reducing man-made climate change: what do we need to do if we want to limit global warming to two degrees over the preindustrial level? And what do we need to do if our goals are less ambitious? Here, too, the IPCC doesn’t dictate terms; we simply offer different alternatives. After all, the two-degree goal is ultimately a political one, not something the IPCC came up with.
“It’s also important to get disciplines on board that haven’t yet addressed climate questions”
CliSAP: So it’s about technology and estimating its impacts?
Held: The technological aspect is important, but it’s certainly not the only focus. The big question is how business and politics can address the climate problem, and what impacts that approach will have for society.
Take cities for example. If we kept using the technologies we do today, by 2050 the expansion of infrastructure alone would pump an additional 470 gigatons of CO2 into the atmosphere, which would make achieving the two-degree goal practically impossible. At the same time, cities offer considerable potential for reductions, for instance by using more compact buildings in connection with a high concentration of jobs in one place. These aspects pose challenges for architects and urban planners, but also for political and social scientists, who research urbanization processes and help to more accurately assess societal developments.
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