Emerging Modules for ESMs:Atmospheric chemistry / Aerosols

For presentation at the Arctic System Model Workshop III

David Plummer

Chemistry effects on climate system

• Unlike LLGHGs, ozone and aerosols can have important regional forcings

Antarctic ozone depletion

• trends over 1969-98 for temperature and geopotential height from radiosonde stations in Antarctica– from Thompson and Solomon, Science, 2002

Antarctic ozone depletion

• trends in polar cap temperature (70S to pole) from 2001 to 2050– Figure 1 from Son et al., Science, 2008

Antarctic ozone depletion

• difference in ocean zonal wind stress between runs with and without a prescribed Antarctic ozone depletion– From Lenton et al., GRL,

2009

• decreased uptake of CO2 by 2.3 Pg-C between 1987-2004

Arctic projections

• no ozone hole formation• interaction of ozone with NH

atmospheric circulation much more complex

• active area of research– prescribed, monthly mean vs.

prognostic

• 21st century temperature trends predicted by a suite of different CCMs– From Butchart et al.

(submitted to J. Clim)

Arctic RF

• pre-industrial to present day O3 RF at the tropopause– from Mickley et al. 1999

• black carbon– affects on surface

albedo

Interaction with other ESM components

• experimental evidence for O3 damage to plants– decreased productivity

• Sitch et al. 2007

– low and high sensitivity to O3

• reactive nitrogen (NOx) emitted and oxidized to HNO3

– NO3- deposition = important nutrient

• OH, H2O2, O3 are powerful oxidants– DMS, SO2, VOCs

Likely situation for GCMs in AR5

• several of the large centres have plans to run transient, coupled runs with interactive chemistry– most likely simplified tropospheric chemistry

– prescribed or constrained stratospheric O3

• more consistency in approach to specifying Antarctic ozone trends