The carbon cycle and the Anthropocene Michael Raupach 1,2 1 Centre for Atmospheric, Weather and Climate Research, CSIRO Marine and Atmospheric Research, Canberra, Australia 2 ESSP Global Carbon Project Thanks: Pep Canadell, Philippe Ciais, Ian Enting, John Finnigan, Pierre Friedlingstein, Corinne Le Quéré, David Newth, Glen Peters, Peter Rayner, Cathy Trudinger, and many more GCP and CSIRO colleagues "Earth System Science 2010: Global Change, Climate and People", May 2010, Edinburgh, UK

Outline u The carbon cycle as a progenitor of the Anthropcene u The contemporary carbon cycle CO 2 emissions trajectories Partitioning anthropogenic CO 2 to air, land and ocean u Stabilising the carbon-climate-human system sharing a cumulative global quota on CO 2 emissions

The carbon cycle as a progenitor of the Anthropocene u The biosphere A complex adaptive system based on carbon Evolving for 3.5 billion years u The anthroposphere One species finds a new evolutionary trick: use of exosomatic energy Easiest energy source: detrital carbon from the biosphere Evolving for tens of thousands of years Biologically based, with extra technological, social, cultural levels

A phase transition in human ecology u Since 1800, global per-capita wealth and resource use have doubled every 45 years u Growth rates ( ) Population: 1.3 %/y GWP: 2.8 %/y GWP/Pop: 1.5 %/y u This exponential growth is the dominant instability in the earth system Angus Maddison ( Population (million) GWP (billion Y2000 $US / y) doubling time = 45 y GWP per capita (Y2000 $US / person / y) AD

Outline u The carbon cycle as a progenitor of the Anthropcene u The contemporary carbon cycle CO 2 emissions trajectories Partitioning anthropogenic CO 2 to air, land and ocean u Stabilising the carbon-climate-human system sharing a cumulative global quota on CO 2 emissions

The carbon cycle since 1850 Le Quere et al. (2007) Nature Geoscience

u Fossil fuels: 2007 emission 8.5 PgC 2008 emission 8.7 PgC growth:3.4 % y 1 u Land use change: 2007 emission~1.5 PgC growth:~0 % y 1 u Without extra change in C intensity, GFC will "save" about 0.25 ppm CO 2 increase Global CO 2 emissions Graphs: Raupach et al. (2007) PNAS, with updated data: CDIAC to 2007, IEA to 2006

Raupach and Canadell (2010) COSUST Emissions growth rates: SRES and observations SRES scenarios dashed = marker solid = family average

Drivers of global emissions Raupach et al. (2007) PNAS Updated with IEA data to 2006 u Kaya Identity Fossil-fuel CO 2 emission Population Per-capita GDP Carbon intensity of GDP

Outline u The carbon cycle as a progenitor of the Anthropcene u The contemporary carbon cycle CO 2 emissions trajectories Partitioning anthropogenic CO 2 to air, land and ocean u Stabilising the carbon-climate-human system sharing a cumulative global quota on CO 2 emissions

Cumulative CO 2 emissions as a measure of climate forcing Allen et al. (2009, Nature) Past FF reserves Unconventional >3000? Peak warming from preindustrial (degC) A1FIA2 A1T A1B B2 B Q = cumulative CO2 emissions from preindustrial (PgC)

Trajectories of CO 2 and T u Plot against time u Peaks in emissions, CO 2 and temperature occur progressively later CO 2 [ppm] ΔT [degK] Time [years] Total emissions quota Q() [PgC] Emissions CO 2 Temperature

Trajectories of CO 2 and T u Plot against Q(t) = cumulative emissions to time t) u Peak T is a nearly linear function of Q to time of peak u "Committed warming" becomes the warming between times of peak emissions and peak temperature Cumulative emission Q(t) [PgC] CO 2 [ppm] ΔT [degK] Total emissions quota Q() [PgC] NOW

Cumulative emission targets and climate risk Cumulative emissions (billion tonnes C) Peak warming above preindustrial ( o C) Probability of avoiding peak warming Past emissionsConventional fossil C reserves Unconventional reserves After Allen et al. (2009, Nature)

The tragedy of the commons and beyond u Hardin (1968) - parable and lack of technical fix u Pretty (2003): social capital as a prerequisite for collective resource management 5 kinds of capital: natural, physical, financial, human, social u Dietz, Ostrom and Stern (2003): Adaptive governance in complex systems Emerges if there are ways to: Provide information Deal with conflict Induce rule compliance Provide infrastructure Be ready for change Hardin G (1968) The tragedy of the commons. Science 162, Dietz T, Ostrom E, Stern PC (2003) The struggle to govern the commons. Science 302. Pretty J (2003) Social capital and the collective mangement of resources. Science 302. Reprinted in Kennedy D et al. (2006) Science Magazine's State of the Planet Island Press, Washington DC. x x x x

Trajectories for capped CO 2 emissions u Emissions trajectory is specified by long-term exponential decay at specified mitigation rate m u OR specified cap on all-time cumulative emissions Q : u There is a 1:1 mapping between m and Q 530 PgC to 2008 (FF+LUC) Total emissions quota Q [PgC] Emission [PgC/y] LUC FF m Q

Summary u The carbon cycle as a progenitor of the Anthropcene A key enabler of the Anthropocene is the use of exosomatic energy The primary energy source was, and remains, detrital biotic carbon u The contemporary carbon cycle Fossil-fuel CO 2 emissions have accelerated Partition fractions of anthropogenic CO 2 to air, land and ocean have been nearly constant, because emissions have grown nearly exponentially and the C cycle has been nearly linear The total CO 2 sink rate is decreasing, mainly through the ocean sink u Stabilising the carbon-climate-human system The task is to share a cumulative global quota on CO 2 emissions Full equity (population sharing) is not possible Attribution of historic emissions is not possible The most achievable sharing rule common to all major nations goes about 70% towards full equity