[Vision2020] 2009 Proceedings of the National Academy of Sciences: "Dangerous Anthropogenic Interference"

[Ted Moffett]

Reducing abrupt climate change risk using the Montreal Protocol and other
regulatory actions to complement cuts in CO2 emissions

http://www.pnas.org/content/106/49/20616.full

August 31, 2009

A few quotes from this very important and well researched article focusing
on means to address anthropogenic climate change other than lowering CO2
emissions:

"Current emissions of anthropogenic greenhouse gases (GHGs) have already
committed the planet to an increase in average surface temperature by the
end of the century that may be above the critical threshold for tipping
elements of the climate system into abrupt change with potentially
irreversible and unmanageable consequences. This would mean that the climate
system is close to entering if not already within the zone of “dangerous
anthropogenic interference” (DAI). Scientific and policy literature refers
to the need for “early,” “urgent,” “rapid,” and “fast-action” mitigation to
help avoid DAI and abrupt climate changes. We define “fast-action” to
include regulatory measures that can begin within 2–3 years, be
substantially implemented in 5–10 years, and produce a climate response
within decades."
------------------

"Fig. 1  http://www.pnas.org/content/106/49/20616/F1.large.jpg  presents
their results for various policy-relevant tipping elements
(9<http://www.pnas.org/content/106/49/20616.full#ref-9>),
most of which Lenton et al.
(8<http://www.pnas.org/content/106/49/20616.full#ref-8>)
include in their analysis; for elimination of Arctic summer sea ice and
melting of the Himalayan-Tibetan glaciers and the Greenland Ice Sheet, the
probability that the committed warming exceeds the tipping point temperature
is estimated to be larger than 50%, and it is estimated to be >10% for
dieback of the Amazon Rainforest, more persistent and higher amplitude El
Niño conditions, reorganization of the North Atlantic Thermohaline
Circulation, and melting of the West Antarctic Ice Sheet."
------------------

"Even when CO2 emissions stop, climate change is largely irreversible for
1,000 years (15
<http://www.pnas.org/content/106/49/20616.full#ref-15>,
16<http://www.pnas.org/content/106/49/20616.full#ref-16>).
Efforts to limit CO2 emissions alone may not be sufficient to avoid or
reduce the risk of DAI on a decadal time scale, including the risk of abrupt
climate change from committed warming
(8<http://www.pnas.org/content/106/49/20616.full#ref-8>,
9 <http://www.pnas.org/content/106/49/20616.full#ref-9>)."
------------------

"We discuss four of the available fast-action regulatory strategies that can
begin within 2–3 years and be substantially implemented within 5–10 years,
with the goal of producing desired climate response within decades. The
first is to phase down the production and consumption of HFCs with high
global warming potential (GWP), accelerate the phase-out of
hydrochlorofluorocarbons (HCFCs), and recover and destroy stratospheric
ozone-depleting GHGs in discarded products and equipment. The second is to
reduce emissions of BC, giving priority to emissions that affect regions of
snow and ice, including the Arctic, Greenland, and the Himalayan-Tibetan
glaciers. The third is to reduce pollutant gases that lead to formation of
tropospheric (lower atmosphere) ozone, a significant GHG. The fourth is to
expand biosequestration through improved forest protection and biochar
production."
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Vision2020 Post: Ted Moffett
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