PowerPointPrsentation

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Past, present and future anthropogenic aerosols
emissions their impact on climate Céline
Déandreis?, Yves Balkanski, Michael
Schulz LSCE/IPSL, Laboratoire des Sciences du
Climat et de l'Environnement, CEA-CNRS-UVSQ
lOrme-des-Merisiers, 91191 Gif-sur-Yvette
FRANCE ?Contact celine.deandreis_at_cea.fr

• Introduction
• The emissions of greenhouse gasses and aerosols
  by human activities since the industrial
  revolution have modified the composition of the
  atmosphere. This perturbation affects the climate
  system by changing the radiative balance of the
  atmosphere. Aerosols that have a cooling effect
  partly cancel the increase in temperature from
  GHGs. However, the relative impact of GHGs and
  aerosols on climate may vary in the future as a
  function of their relative abundances. In this
  study, we analyzed the impact of a stabilization
  or a reduction in anthropogenic aerosol emissions
  in the future.

We performed snap shot simulations of 2 years
with the GCM of the Laboratoire de Météorologie
Dynamique (LMD-Z), coupled to the
chemistry-aerosol model INCA (Interactive
Chemistry and Aerosols). We estimate a global
aerosol radiative forcing of -0.59 W/m² for 2000,
-0.75 W/m² for 2030 and -0.76 W/m² for 2050.
However, aerosol forcing is spatially
heterogeneous and can reach values as low as -10
W/m² locally.

• Emissions for 1750, 2000, 2030 and 2050

• Evolution of emissions

• Natural Emissions
• Based on the AEROCOM aerosol model
  inter-comparison experiment inventory (Dentener
  et al 2006).

We keep natural aerosol emissions unchanged for
each time period. Exception volcanic emissions
for 2030 and 2050 ? 0.

• Anthropogenic emissions
• Pre-industrial present-day
• Based on the AEROCOM aerosol model
  inter-comparison experiment inventory (Dentener
• et al 2006).
• Future time period
• We follow A2 IPCC SRES scenario.
• We use inventories that take into account policy
  measures and legislation, as well as emissions
• control technologies contrary to the IPCC
  inventory.
• carbonaceous aerosols
• based on Speciated Particulate Emissions Wizard
  (Spew inventory of Streets et al, 2004).
• precursors of sulphate, SO2
• based on the NIES emission inventory (T.Nozawa
  pers communication) and
• SO2 AEROCOM 2000 emissions.

• IPCC comparison of future anthropogenic
  emissions

2. Burdens and radiative effect

• Change in optical depth (100)

• Regional direct forcing

Sulphate concentration increases from 2000 to
2030 and subsequently declines. It results in a
negative radiative effect, which is followed by a
positive effect.
The reduction in the abundance of POM results in
a positive radiative effect.
?- 0.20 W/m2
The decrease in BC concentrations results in a
negative radiative effect.
Globally, this results in a negative direct
effect that increases in the future.
There is a good correlation between emissions,
optical depth and direct radiative forcing.

• Analysis of the impact of sulphate

• Global forcing

Observation A reduction in the indirect effect
is balanced by an increase in the direct
effect. Consequence Cooling due to anthropogenic
aerosols will increase in 2030 and 2050.