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Climate change:
evolving evidence and implications
Michael Raupach1,2
1Centre
for Australian Weather and Climate Research,
CSIRO Marine and Atmospheric Research, Canberra, Australia
2ESSP
Global Carbon Project
Thanks:
Pep Canadell, Corinne Le Quéré, many other GCP colleagues
Vanessa Haverd, Peter Briggs, many other CSIRO colleagues
Colleagues in PMSEIC “Energy-water-carbon intersections”
Colleagues in “Negotiating our future: Living Scenarios for Australia to 2050”
Fenner Conference “Population, resources and climate change: implications for Australia’s future” (AAS, Canberra, 10-11 October 2013)
Outline
Context
• The climate system is a touchy beast
• We are poking it with a stick
IPCC Fifth Assessment (AR5)
• What the evidence says (past century, coming century)
• The false debate
The “carbon budget” for avoiding dangerous climate change
• How and why it works
• Implications for mitigation rates
Since 1800, global
per-capita wealth and
resource use have doubled
every 45 years
Population (million), GDP (Intl $billion)
The Anthropocene:
an epoch of growth
100000
10000
1000
Population
GDP
100
Growth rates (1860-2010)
• Population: 1.3 %/y
• GWP:
2.8 %/y
• GWP/Pop: 1.5 %/y
Per capita GDP (Intl $ per person)
10000 0
500
1000
1500
2000
1000
Per capita GDP
100
0
Angus Maddison
(http://www.ggdc.net/maddison/)
500
1000
Year AD
1500
2000
We believe that western technological society has ignored two vital facts:
• The resources of planet earth are finite.
• The capacity of the environment to renew resources that are used up and to
repair the damage caused by the exploitation of these resources is limited and
decreasing.
– The Australian, May 21 1971
Global temperature
(land + ocean, HadCRUT3)
(PgC/y)
Total CO2 emissions
Approximately
exponential forcing
8
6
4
2
0
1850
400
380
1890
1930
1970
2010
1970
2010
Response 1: atmospheric
GHG concentrations
360
340
320
300
280
1850
1890
0.8
Response 2:
1930
climate change
0.6
(deg C)
CO2 concentrations
(composite record)
10
Atmospheric CO2
(ppm)
CO2 emissions
(fossil fuels + land use change)
12
Global temperature
Earth system:
forcing and responses
0.4
0.2
0
-0.2
-0.4
-0.6
1850
1890
1930
1970
2010
The climate system
Volcanoes
Aerosols
Biosphere
Solar
radiation
Orbital
variations
GHGs
(CO2, …)
Human
activities
Climate
(temperature)
Heat
radiation
Adapted from: Australian Academy of Science (2010)
The science of climate change: questions and answers
Water
vapour,
clouds
Oceans
Ice
sheets
Climate in the distant past (800,000 years)
Present CO2
Hansen et al. (2008)
Target atmospheric CO2
Climate
1850-present
Air temperature
(land)
Measures of
changing global
climate from
1850 to present
10 quantities
Air temperature (ocean)
All available
datasets are
shown
Sea level
IPCC AR5 FOD TS Fig TS.1
Arctic seaice extent
IPCC AR5 FOD TS Fig TS.7
Climate models: testing with data
Pinatubo
El Chicon
Agung
Santa Maria
Krakatoa
Models (natural + anthropogenic forcings)
Climate models: future global warming and precipitation
Warming
More warming in high latitudes (polar
amplification) – already observed
Change in precipitation
Increase in global precipitation
(and global evaporation)
Changes are highly non-uniform:
predicted drying in mid-latitudes
Diffenbaugh and Field (2013) Science 341, 486-492
Climate models:
future warming
4 scenarios (RCPs) for
future human impact on
climate system, from low to
high
Climate model runs by
many teams for each
scenario:
• ~30 to 2100
• ~10 to 2300
Warming (1850-2100):
•
•
mean (5, 95) %
Low: 1.7 (0.7, 2.8) oC
High: 4.7 (3.6, 5.9) oC
IPCC AR5 FOD TS Fig. TS.13
Updated from Canadell et al. (2007) and Le Quéré et al. (2009)
Data: http://www.globalcarbonproject.org/carbonbudget/index.htm
Atmospheric CO2 budget (1850-2011)
Fluxes in
2011
[PgC/y]
Flux [PgC/y]
9.5
0.9
2.6
4.1
3.6
Global warming and the cumulative-emission clock
Reinforcing feedbacks:
• Ice-albedo
• Carbon cycle
• Ecosystem collapse
Non-CO2 gases
Aerosols
CO2 only
Stabilising feedbacks:
• Heat loss (Planck)
• CO2 removal by carbon sinks
• Logarithmic response to CO2
Raupach et al. (2011), revised in Raupach (2012)
The carbon budget
To stay below 2 degrees of warming (above preindustrial):
Allowed cumulative CO2 emissions (1750 to far future) are
• 1000 GtC => 1 in 2 chance of success
• 800 GtC => 2 in 3 chance of success
Cumulative CO2 emissions from 1750 to present: 550 GtC
Factored into budget:
• Likely emissions of non-CO2 gases, aerosols
• Climate feedbacks in present models (including uncertainties)
Not factored in:
• Carbon cycle feedbacks – especially release of Arctic C stores
Sharing the cumulative emissions pie
Inertia:
share byw=0.0
current or
historic emissions
Developing
Equity:
share
w=1.0by
population
Compromise:
share by
mixture of
w=0.5
emissions and population
USA
USA
Europe
Japan
D1
FSU
China
India
D2
D3
Qi  Q
Fi
F
USA
Europe
Japan
D1
FSU
China
India
D2
D3
USA
Europe
Japan
D1
FSU
China
India
D2
D3
F
P

Qi  Q  1  w  i  w i 
F
P

Qi  Q
weight w (0 to 1) is an "equity index"
w=0
w=1
Pi
P
Sharing the
mitigation task
Mitigation rate
characterises
mitigation challenge
Carbon budget:
1000 GtC total
Equity
As equity increases
in emissions sharing,
mitigation rates pivot
around the required
world mitigation rate
Middle
A little equity goes a
long way towards a
sharing of the
emissions quota that
is both achievable
and fair
Inertia
Narratives
Definition: Narratives = stories that guide and empower actions
• Narratives are very powerful, and fundamental to being human
• Narratives are independent of truth
• Two broad narrative families for the 21st century: “growth” and “sustenance”
Hypothesis: Narratives are meme sequences that evolve
• Diversification, selection, adaptation
• Evolution can be understood, influenced, but not controlled
•
Examples: the Enlightenment, decline of violence,
Implications:
• In shaping our shared future, the evolutionary contest between growth and
sustenance narratives is just as important as the dynamics of the natural world
• Need to guide evolution of resilient narratives that empower transition to a
society that is simultaneously sustainable and improves global human wellbeing
Raupach, M.R. (2013). The evolutionary nature of narratives about expansion and sustenance. In: Negotiating Our Future: Livi ng scenarios for Australia to 2050, Vol. 2. (eds. Raupach, M.R., McMichael, A.J., Finnigan, J.J., Manderson, L., Walker, B.H.). (Australian Academy
of Science), 201-213. (http://www.science.org.au/policy/australia-2050/)
Summary
Climate change as one of a set of pressures on the Earth System
Can humankind avoid dangerous climate change?
• Objective science
• emissions -> concentrations -> climate -> impacts
• Thresholds, tipping points in the climate system
• Some changes are happening faster than predicted
• The dose-response relationship
• Subjective values
• Two great narratives: expansion versus sustenance
• Human actions
• Thresholds, tipping points in human behaviour
Whole-system perspective
• The goal: coupled environmental sustainability and social equity
• Enablers: resilience, innovation, connectivity, strange alliances
Each point represents one year from 1971 to 2011
IEA (2012)
2011
1971
Per capita GDP
Per capita emissions (tC/year/person)
Per capita energy use (GJ/year/person)
The resulting wiggly line is a “development trajectory” showing how
energy and CO2 emissions are coupled with affluence (per capita GDP)
Per capita
resource use
Development trajectories: coupled growth
in economy, energy and emissions
Per capita GDP (k$/year/person)
Per capita GDP (k$/year/person)
Emissions per unit energy
(carbon intensity of energy)
Emissions / Energy (tC/TJ)
Development trajectories: coupled growth
in population, economy, energy and emissions
Where we need to be
Per capita GDP (k$/year/person)
IEA (2012)
Challenges at
energy-water-carbon intersections
E
C
W
Principles
Technologies
Resilience
Innovation
PMSEIC (2010). Challenges at Energy-Water-Carbon Intersections. (Expert Working Group: Michael Raupach (Chair), Kurt Lambeck (Deputy Chair), Matthew
England, Kate Fairley-Grenot, John Finnigan, Evelyn Krull, John Langford, Keith Lovegrove, John Wright, Mike Young). Prime Minister’s Science, Engineering and
Innovation Council, Canberra, Australia. http://www.chiefscientist.gov.au/wp-content/uploads/FINAL_EnergyWaterCarbon_for_WEB.pdf
Abstract
The science of climate change receives intense public scrutiny, making it difficult to
distinguish signal from noise. A crucial example is the recent slowdown in the rate
of warming in the global atmosphere. Does this mean that the scientific consensus
on climate change has overstated its threat?
In short, no. Two main factors have contributed to the slowdown: heat being drawn
down into the deep oceans, and indirect cooling from atmospheric aerosol (partly
from coal combustion). Evolving observations of the energy balance of Earth, deep
ocean heat content, sea level rise, polar and glacial ice extents, greenhouse gas
concentrations and emissions (and more) continue to show that climate change is
ongoing and that its broad policy implications have been correctly articulated by the
climate science community.
The primary implication is that, to avoid dangerous climate change, there is a cap
on the amount of fossil fuel that can be burned. As estimates of this cap are
refined, the following broad directions remain soundly based: to change the mix of
energy resources away from fossil fuels, to limit population growth and wasteful
resource consumption, and to keep a large proportion of fossil fuel reserves in the
ground.