“The vulnerability of many carbon cycle processes and pools depends
on the magnitude of future climate change. The magnitude of future
climate change, in turn, depends on the vulnerability of the carbon
cycle.” (Gruber et al. 2004: 52)
OCEANIC
It is difficult to assess the overall impact of climate change on by 9% as a consequence of climate change impacts (through
oceanic carbon uptake capacity. Warming temperatures will reduction of wind-borne iron supply to the ocean, resulting
certainly affect the uptake of inorganic carbon, because carbon in a decrease in productivity) (Ridgwell et al. 2002). For the
dioxide dissolves less readily in warm water than in cold. In- Southern Ocean, a weakening of the carbon sink has been
creasing temperatures may also lead to increased stratification observed during the last two decades and whether this trend
of sea waters and a slowing down of turnover between surface may continue or reverse is uncertain (Le Quéré et al. 2007; Le
and deep waters, leading to less transfer of dissolved inorganic Quéré et al. 2008).
carbon to the ocean bottom. One study predicted that the ability
of the oceans to absorb inorganic carbon could peak at around The ecological consequences of ocean acidification caused by
5 Gt per year, and that this peak could be reached by the end of increased uptake of inorganic carbon are largely unknown.
the 21st century (Cox et al. 2000). However, progressive acidification is expected to reduce car-
bonate accretion of the shells, bones and skeletons most ma-
Increased presence of dissolved inorganic carbon in sea-wa- rine organisms possess, having impact on marine food chains
ter can have a fertilising effect so that the biomass of pho- from carbonate based plankton up to higher trophic levels (The
tosynthetic groups such as brown algae and seagrasses in- Royal Society 2005; Nellemann et al. 2008).
creases when CO
2
does (Guinotte and Fabry 2008). In situ
studies recently undertaken at a natural CO
2
vent area in Overall, while there is agreement between most climate mod-
Ischia, Italy, have shown that seagrass communities flourish els that both the land and ocean carbon cycles will be affected
in increased carbon dioxide environments (Hall-Spencer et by future climate change, there is still large uncertainty on
al. 2008). the magnitude of these impacts (Friedlingstein et al. 2006).
There is major uncertainty about the response of South
Cermeno et al. (2009) predict that global warming will lead American and African tropical rainforests to continuing cli-
to an additional decreased efficiency of the so-called biologi- mate change, largely depending on the severity of changes
cal pump in sequestering carbon due to thermal stratification in precipitation (Schaphoff et al. 2006). Large-scale field ex-
and a resulting reduction in nutrient supply to the deeper periments, such as FLUXNET, could significantly contribute
ocean layers. Carbon models have shown that the rate of or- to improving existing carbon and climate models (Running
ganic uptake of carbon dioxide by the ocean may be reduced 2008; Baldocchi 2008).
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