Future CO₂ emissions: Representative Concentration Pathways

Representative Concentration
Pathways (RCPs) are future
emissions pathways used in
the Intergovernmental Panel
on Climate Change’s Fifth
Assessment Report. Many
scenarios could lead to a
particular pathway. The highest
RCP (8.5 Wm^-2 radiative forcing)
represents high (business as
usual) emissions. It results in
mean global warming by 2100
of about 4.3°C (likely range,
3.2°–5.4°C) above preindustrial
temperatures. The lowest RCP
(2.6 Wm^-2 radiative forcing)
requires significant mitigation and
emissions reductions resulting
in a global average temperature
rise of about 1.6°C (likely range,
0.9°–2.3°C) above preindustrial
levels.

Global marine consequences

By 2100, business-as-usual
emissions (RCP 8.5) would result
in ocean acidification leading
to the loss of 100% of tropical
surface waters with conditions
favourable for coral reef growth.
Significant reductions (RCP 2.6)
would result in less than half of
this loss (personal communication,
Joos and Steinacher).

By 2100, 60% of Southern Ocean surface waters (on average) could become corrosive to the shells of organisms made with the aragonite form of calcium carbonate if emissions continue along a business-as-usual trajectory (RCP 8.5). With strong mitigation (RCP 2.6), corrosive conditions in most of the Southern Ocean can be avoided (personal communication, Joos and Steinacher).

[This text is from the Ocean Acidification Summary for Policy Makers, 2013, and is available online as a PDF with full references.]