Page 217 - Materials Chemistry, Second Edition

10 Life Cycle Impact Assessment 203

Fig. 10.6 “The big loop” takes 1500 years to circumnavigate the globe (NASA/JPL 2010, public
domain, http://www.jpl.nasa.gov/news/news.php?release=2010-101)

• Mobilisation and release of oceanic methane hydrate (water ice containing large
amounts of methane in its crystal structure) present in deep ocean sediments and
permafrost, could lead to further global warming and significantly affect the
atmospheric oxygen content. There is large uncertainty regarding the amounts
and size of reserves found under sediments on the ocean floors, but a relatively
sudden release of large amounts of methane hydrate deposits is believed to be a
main factor in the global warming of 6 °C during the end-Permian extinction
event (Benton and Twitchet 2003) when 96% of all marine species became
extinct 251 million years ago.
• Effects on Earth’s primary “lung”: phytoplankton which produces 80% of ter-
restrial oxygen and absorbs a significant share of CO 2 .
• In addition to the environmental effects discussed above, the human population
is likely to be affected by further severe consequences should other adaptation
strategies prove inefficient: disease, malnutrition and starvation, dehydration,
environmental refugees, wars and ultimately death.
• Nonlinearity of cause–effect chains, feedback and irreversible tipping points:
Although, in LCIA models, linearity of cause–effect chains is assumed, the
above discussed effects present several examples of mechanisms that are unli-
kely to depend linearly on the temperature increase, i.e. they will not change
proportionally in frequency and/or intensity per degree of change in global
temperature. Furthermore, they are likely to directly or indirectly influence each
other, causing feedback reactions adding further nonlinearity. Additionally,
some of these effects will be irreversible, changing the climate from one stable
state to another. This phenomenon is referred to as tipping points, and the
above-mentioned release of methane from methane hydrates and the alteration
of the Gulf stream are examples. Lenton et al. (2008) discuss a number of
additional potential tipping points.