Explicit calculation of indirect global warming potentials for halons using atmospheric models


Youn Daeok, Kenneth O Patten, Jin-Tai Lin, and Donald J. Wuebbles. 2009. “Explicit calculation of indirect global warming potentials for halons using atmospheric models.” Atmospheric Chemistry and Physics, 9, 22, Pp. 8719-8733. Publisher's Version


The concept of Global Warming Potentials
(GWPs) has been extensively used in policy consideration
as a relative index for comparing the climate impact of an
emitted greenhouse gas (GHG), relative to carbon dioxide
with equal mass emissions. Ozone depletion due to emission
of chlorinated or brominated halocarbons leads to cooling
of the climate system in the opposite direction to the direct
warming contribution by halocarbons as GHGs. This
cooling is a key indirect effect of the halocarbons on climatic
radiative forcing, which is accounted for by indirect GWPs.
With respect to climate, it is critical to understand net influences
considering direct warming and indirect cooling effects
especially for Halons due to the greater ozone-depleting efficiency
of bromine over chlorine. Until now, the indirect
GWPs have been calculated using a parameterized approach
based on the concept of Equivalent Effective Stratospheric
Chlorine (EESC) and the observed ozone depletion over the
last few decades. As a step towards obtaining indirect GWPs
through a more robust approach, we use atmospheric models
to explicitly calculate the indirect GWPs of Halon-1211
and Halon-1301 for a 100-year time horizon. State-of-theart
global chemistry-transport models (CTMs) were used as
the computational tools to derive more realistic ozone depletion
changes caused by an added pulse emission of the
two major Halons at the surface. The radiative forcings on
climate from the ozone changes have been calculated for indirect
GWPs using an atmospheric radiative transfer model
(RTM). The simulated temporal variations of global average
total column Halons after a pulse perturbation follow an exponential
decay with an e-folding time which is consistent
with the expected chemical lifetimes of the Halons. Our cal-
culated indirect GWPs for the two Halons are much smaller
than those from past studies but are within a single standard
deviation of WMO (2007) values and the direct GWP values
derived agree with the published values. Our model-based
assessment of the Halon indirect GWPs thus confirms the
significant importance of indirect effects on climate.
Last updated on 07/31/2019