Re: [asa] Bacterial Gene May Affect Climate And Weather

From: PvM <>
Date: Sat Feb 17 2007 - 19:58:21 EST

Since Janice raised the issue that according to her, climate models
fail to take into account significant or potentially significant
contributions to the global temperature I decided to do some research.

Global circulation models of the atmosphere are coupled to global
ocean circulation models, contrary to what was suggested. In fact, the
two have been quite well integrated although in earlier days, the
coupling was less robust as it is in present days. Such is science

dimethyl sulfide or DMS is part of the ICPP model already or has been
modeled to determine the impact on global warming

But not just DMS but also aerosols

<quote>what aerosols and are indirect effects modeled? Three modes of
sulfates aerosols (Aitken, accumulation and dissolved in cloud
droplets) with explicit parameterizations of transfers between the
different modes. SO2 and DMS are injected at appropriate levels. The
direct radiative effect from scattering and absorption is taken into
account. The indirect effect was implemented by prescribing cloud
changes calculated by offline models (see Johns et al., 2003, Appendix
A for more details)</quote>

See also, titled
The sensitivity of dimethyl sulfide production to simulated climate
change in the Eastern Antarctic Southern Ocean

AR4 mentions

Bopp et al. (2004) were the first to estimate the feedback of DMS on
cloud albedo by using a coupled atmosphere-ocean-biogeochemical
climate model that includes phytoplankton species in the ocean and a
sulfur cycle in the atmospheric climate model. They obtained an
increase in the sea-air DMS flux of 3% for 2xCO2 conditions, with
large spatial heterogeneities (15% to +30%). The mechanisms affecting
those fluxes are marine biology, relative abundance of phytoplankton
types, and wind intensity. The simulated increase in fluxes causes an
increase in sulphate aerosols and, hence, cloud droplets resulting in
a radiative pertubation on cloud albedo of 0.05 W m2, which
represents a small negative climate feedback on global warming.


<quote>Although a quantitative estimate of the climate feedback of DMS
is beyond the scope
of this study, the results here suggest that a global warming leads to
a reduction of the
overall biological production in the ocean and therefore to a decrease
in the DMS sea sur-
face concentration, contradicting the negative feedback proposed in
the CLAW hypothesis
[Charlson et al., 1987]. In the CLAW hypothesis a key factor for a
negative feedback is
an increase in the DMS sea surface concentration in a warmer climate.
However, our sim-
ulation shows the opposite, i.e. decreasing DMS sea surface
concentrations in a warmer
climate, for the global mean and most of the ocean surface.

Response of dimethylsulfide (DMS) in the ocean and atmosphere to
global warming
S. Kloster et al

Now remember that AR4 documents the errors and variations in the GCM
models and these have been used to forecast the future global warming
trends. Yes, we all know that these models are not perfect but science
is not only studying the effect of these imperfections but also is
adding missing details to better and more accurately model the global
temperatures in forecast. While models quite adequately capture the
natural and anthropogenic components to the global increase in
temperatures, and thus indicate that they are quite satisfactory,
there will always remain, ever decreasing, uncertainties about missed

To unsubscribe, send a message to with
"unsubscribe asa" (no quotes) as the body of the message.
Received on Sat Feb 17 19:58:45 2007

This archive was generated by hypermail 2.1.8 : Sat Feb 17 2007 - 19:58:45 EST