NESSC-researchers, together with international climate scientists, have published a new paper on climate sensitivity. The article Lessons on climate sensitivity from past climate changes was just published in the new journal Current Climate Change Reports.

The review paper highlights a number of routes how to make progress in our understanding of currently on-going climate change by combining evidence from the past with theoretical approaches – which is a main topic for research done at NESSC. The new publication is also a concrete result of the NESSC workshop “Mathematical approaches to (palaeo-)climate sensitivity”, which was held last year November.

First author of the article, NESSC-researcher Anna von der Heydt: “Climate sensitivity is a key number to quantify the effect of greenhouse gas emissions on climate. It is often defined as the long-term global mean temperature change that follows from doubling the atmospheric CO₂ content. Palaeoclimate studies have frequently measured natural climate changes to calculate climate sensitivity, but a lack of consistent methodologies produced a wide range of estimates as to the exact value of climate sensitivity.”

Climate changes in the past
Understanding how the earth’s climate changed in the past can help scientists in estimating the response of the climate system to changes in greenhouse gas concentrations. A few years ago, a more consistent definition of climate sensitivity in prehistoric times was suggested by the PALAEOSENS project, to help improve comparison with estimates of long-term climate projections developed by the Intergovernmental Panel on Climate Change (IPCC).

However, debate around climate sensitivity derived from palaeo-records continues. Several problems are widely discussed in the scientific community: How can the large uncertainty of this number be reduced? How can theoretical approaches and observations or reconstructions of past climates be combined to this purpose? Do we need a different definition of climate sensitivity to make progress?

Workshop
The NESSC-workshop last year brought together researchers, postdocs and PhD-students, both from within and outside NESSC, to address and discuss these fundamental questions, which ultimately culminated in the new publication. Particular focus in the paper also lies on the background state-dependence of feedback processes and on the impact of tipping points in the climate system.

Publication:
‘Lessons on climate sensitivity from past climate changes’
Current Climate Change Reports. http://dx.doi.org/10.1007/s40641-016-0049-3