WP6: Atmosphere-cryosphere-societal interactions
WP-leader: Ilona Riipinen, email: ilona.riipinen (at) itm.su.se
Co-WP-leader: Øystein Hov, email: oystein.hov (at) met.no
Co-WP-leader: Hans-Christen Hansson, email: hc (at) itm.su.se
Co-WP-leader: Trond Iversen, email: trond.iversen (at) met.no
We use NorESM to address the topic of geo-engineering (i.e. feedback loop 3) by analysing a historic “geo-engineering experiment” that inadvertently has taken place, and how it may have affected Arctic climate, including its sea ice prevalence. This historic “geo-engineering experiment” is the change in European SO2 emissions from ca. 20MtS in 1900 to a maximum of ca. 80MtS in 1980 with most of the rise after 1950 and down to a level of ca. 25MtS today.
We propose a priority list of 4 experiments, that assume that basic NorESM simulations exist for the pre-industrial, multi-century control climate, and for the time-evolving climate from 1850 through 2010.
The first experiments employ on-line aerosols with prescribed sea-surface temperatures (SST). Only the atmosphere and upper land-surface thus give rise to feedback. A pair of runs can be made with (1a) time-varying and (1b) constant emissions of aerosols and precursors (as of 1980).
The next experiments are for further quantifying climate response to the emissions in (1a) and (1b), including the feedbacks between the relevant atmospheric composition and climate. The experiments are time-dependent climate response runs with deep-ocean calculations and on-line aerosols, and with: (2a) time-varying and (2b) constant emissions of aerosols and precursors (as of 1980). The relevance for the climate change – atmospheric composition coupling problem of a full climate response calculation with an interactive deep-ocean arises from the hypotheses that the slow climate fluctuations governed by the deep ocean variability control the systematic changes in the synoptic weather pattern over important aerosol source regions. Eventually, these factors can cause significant spatial and temporal variability in the abundance of air pollutants even if pollutant emissions stay constant.
In a third experiment, the time-dependent climate response to 2-3 scenarios for future emissions with the fully coupled model is calculated.
The last experiment is related to feedbacks caused by society responses to new opportunities when Arctic climate change (feedback loop 2). Using scenarios for emissions from increased ship-traffic and off-shore oil- and gas-exploitation when Arctic sea-ice is drastically reduced, a pair of experiments (4a) without and (4b) with the possible new Arctic emissions for the next few decades can be made. Important question is the relative importance of the intrinsic Arctic emissions for Arctic climate change, and if the emissions serve to enhance or damp the climate change signal.