10 – The Future of Coral Reefs in a Rapidly Changing World
97
past 100 years. An early question in the study of anthropogenic climate change was whether these increases in
temperature were ‘unnatural’ or whether they were
part of a natural cycle? The answer has come from analysis of long term records of temperatures deduced from
isotopic ratios. In chemical reactions, isotopes of any
chemical (e.g.
16
O v.
18
O, or
12
C v.
13
C) participate in
chemical reactions in the defined isotopic ratios that are
determined by temperature. In coral skeletons, the date
when the chemical reaction that produced a particular
growth ring of calcium carbonate can also be precisely
determined, by either counting the number of growth
bands back from the living surface or by dating using
other isotope methods. Consequently, the isotopic ratio
of oxygen in any particular growth ring can be converted into a measure of the sea temperature at a particular time. As some corals, such as Porites, may live for
hundreds of years, with their fossil skeletons persisting
for many thousands of years, we have an enormously
valuable archive of past sea temperatures. Similar
BOX 10.1 THE INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE
(IPCC)
The United Nations triggered the formation of the Intergovernmental Panel on Climate
Change (IPCC) in 1988 as a response to debate over the evidence for the enhanced greenhouse effect and its influence on the Earth’s climate, biology and human societies. Since
its formation, the IPCC has produced four assessment reports (1992, 1996, 2001, 2007)
that represent the global consensus of over 2500 experts in matters pertaining to the
greenhouse issue. There are three main working groups. The first is focused on reviewing the physical evidence and climate projections (Working Group 1: The Physical Science Basis) while the second is focused on the impacts and how human systems and
society might adapt to climate change impacts (Working Group 2: Climate Change Impacts, Adaptation and Vulnerability). Working Group 3 concentrates on reviewing the
ways that humans might reduce the rate at which greenhouse gases are building up in
the atmosphere (‘mitigation’). These working groups are formed in the years prior to
each report through the nomination of the most credible and leading scientists in each
area. The scale of the collaboration and consensus associated with the IPCC reporting
mechanism is unparalleled in history, given that in addition to seeking the agreement of
the thousands of scientists, the document is available for review by the public, governments, non-government agencies and industries. Generally, the consensus leads to a
more conservative assessment of the scientific issues. Despite this, the fourth assessment
report, which was released in the first half of 2007: 3, stated ‘the understanding of anthropogenic warming and cooling influences on climate has improved since the Third
Assessment Report (TAR), leading to very high confidence that the globally averaged
net effect of human activities since 1750 has been one of warming’. The consensus concludes that there is no longer any doubt that humans have changed the climate through
the burning of fossil fuels. The IPCC also reviews the projections for the future (Fig. 10.2)
and has concluded that doubling the atmospheric concentrations of carbon dioxide over
preindustrial values (i.e. taking it from 280 to 550 ppm) is likely to result in increased
mean surface temperatures in the range of 2°C to 4.5°C over today. (Note: Likely is defined by the IPCC as ‘something happening with a 66% probability’.) For more information on climate change and the IPCC, we recommend that you go to the IPCC web site
available at http://www.ipcc.ch [Verified 19 Feb 2008].
97
past 100 years. An early question in the study of anthropogenic climate change was whether these increases in
temperature were ‘unnatural’ or whether they were
part of a natural cycle? The answer has come from analysis of long term records of temperatures deduced from
isotopic ratios. In chemical reactions, isotopes of any
chemical (e.g.
16
O v.
18
O, or
12
C v.
13
C) participate in
chemical reactions in the defined isotopic ratios that are
determined by temperature. In coral skeletons, the date
when the chemical reaction that produced a particular
growth ring of calcium carbonate can also be precisely
determined, by either counting the number of growth
bands back from the living surface or by dating using
other isotope methods. Consequently, the isotopic ratio
of oxygen in any particular growth ring can be converted into a measure of the sea temperature at a particular time. As some corals, such as Porites, may live for
hundreds of years, with their fossil skeletons persisting
for many thousands of years, we have an enormously
valuable archive of past sea temperatures. Similar
BOX 10.1 THE INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE
(IPCC)
The United Nations triggered the formation of the Intergovernmental Panel on Climate
Change (IPCC) in 1988 as a response to debate over the evidence for the enhanced greenhouse effect and its influence on the Earth’s climate, biology and human societies. Since
its formation, the IPCC has produced four assessment reports (1992, 1996, 2001, 2007)
that represent the global consensus of over 2500 experts in matters pertaining to the
greenhouse issue. There are three main working groups. The first is focused on reviewing the physical evidence and climate projections (Working Group 1: The Physical Science Basis) while the second is focused on the impacts and how human systems and
society might adapt to climate change impacts (Working Group 2: Climate Change Impacts, Adaptation and Vulnerability). Working Group 3 concentrates on reviewing the
ways that humans might reduce the rate at which greenhouse gases are building up in
the atmosphere (‘mitigation’). These working groups are formed in the years prior to
each report through the nomination of the most credible and leading scientists in each
area. The scale of the collaboration and consensus associated with the IPCC reporting
mechanism is unparalleled in history, given that in addition to seeking the agreement of
the thousands of scientists, the document is available for review by the public, governments, non-government agencies and industries. Generally, the consensus leads to a
more conservative assessment of the scientific issues. Despite this, the fourth assessment
report, which was released in the first half of 2007: 3, stated ‘the understanding of anthropogenic warming and cooling influences on climate has improved since the Third
Assessment Report (TAR), leading to very high confidence that the globally averaged
net effect of human activities since 1750 has been one of warming’. The consensus concludes that there is no longer any doubt that humans have changed the climate through
the burning of fossil fuels. The IPCC also reviews the projections for the future (Fig. 10.2)
and has concluded that doubling the atmospheric concentrations of carbon dioxide over
preindustrial values (i.e. taking it from 280 to 550 ppm) is likely to result in increased
mean surface temperatures in the range of 2°C to 4.5°C over today. (Note: Likely is defined by the IPCC as ‘something happening with a 66% probability’.) For more information on climate change and the IPCC, we recommend that you go to the IPCC web site
available at http://www.ipcc.ch [Verified 19 Feb 2008].