NaturalResource Impacts of Climate Change: What Do We Know

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Natural-Resource Impacts of Climate Change
What Do We Know?

• John P. Holdren
• Director, The Woods Hole Research Center
• Teresa John Heinz Professor of Environmental
  Policy, Harvard University
• President, American Association for the
  Advancement of Science
• Contribution to Opening Panel, National
  Leadership
  Summit on Natural Resources and
  Climate Change
• Wingspread, WI 4-6 December
  2006

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What we know in a nutshell

• THE REALITY, PACE, IMPACTS OF ANTHROPOGENIC
• CLIMATE CHANGE
• The human influence on climate is more certain,
  growing more rapidly, and already doing more
  damage than was thought just a few years ago.
• Avoiding dangerous anthropogenic interference
  (as called for by the UNFCCC) is no longer
  possible, because our interference is already
  dangerous
• as manifested in increased floods, droughts,
  heat waves, wildfires more powerful storms
  accelerated sea-level rise species migrations
  extinctions (see Bierbaum, to come)
• The only question now is whether it is still
  possible to avoid catastrophic anthropogenic
  interference.

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What we know (continued)

• WHERE ARE WE HEADED UNDER BAU?
• Atmospheric CO2, at 380 ppmv in 2006, reaches
  550 ppmv by 2060 and over 700 ppmv by 2100.
  Post-2100 concentration likely to reach 1100 ppmv
  (4x pre-industrial).
• If other human influences continued to cancel out
  (optimistic), the corresponding equilibrium
  increases in global average surface T would be
  2-4C for 550 ppmv and 4-8C for 1100 ppmv 2-3
  times higher mid-continents and higher still in
  far North.
• At ?Tavg 2C the Earth will be hotter than at
  any time in the last million years at ?Tavg
  3C hotter than at any time in the last 25
  million.
• Such changes risk tipping points into
  drastically different climatic regimes, with huge
  impacts on human well-being.

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What we know (continued)

• SOCIETYS CHOICES
• Facing these dangers, we have 3 options
• Mitigation, meaning measures to reduce the pace
  magnitude of the changes in global climate being
  caused by human activities.
• Adaptation, meaning measures to reduce the
  adverse impacts on human well-being resulting
  from the changes in climate that do occur.
• Suffering the adverse impacts that are not
  avoided by either mitigation or adaptation.

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What we know (continued)

• MITIGATION AND ADAPTATION ARE BOTH ESSENTIAL
• Human-caused climate change is already occurring
  and already dangerous.
• Adaptation efforts are already taking place and
  must be expanded.
• But adaptation becomes costlier and less
  effective as the magnitude of climate changes
  grows.
• The greater the amount of mitigation that can be
  achieved at affordable cost, the smaller the
  burdens placed on adaptation and the smaller the
  suffering.

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What we know (continued)

• WHATS A PRUDENT TARGET FOR MITIGATION?
• New understandings of impacts potential for
  tipping points mean that 550 ppmv CO2-equivalent
  (CO2e) once thought to be a prudent and
  attainable target for stabilization of human
  influences on the atmosphere is not prudent at
  all.
• 450 ppmv CO2e would be significantly more
  prudent, but it is not attainable unless society
  begins a major transformation of both the energy
  system and land-use practices essentially
  immediately.

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What we know (continued)

• GOOD NEWS BAD NEWS ABOUT THE PROSPECTS
• Good There are numerous win-win (or no
  regrets) approaches that can deliver significant
  climate-change mitigation together with
  co-benefits in, e.g., energy savings, air-quality
  improvement, the water-management
  biodiversity-preservation functions of intact
  forests, and creation of sustainable jobs.
• Bad Some approaches to mitigation -- notably
  carbon sequestration in forests and substitution
  of biofuels for fossil fuels -- will exacerbate
  the looming problem of competing human uses of
  the worlds land, soils, and water for food,
  fiber, biofuels, chemical feedstocks, and
  ecosystem function (which is already being
  exacerbated by climate change itself).

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What we know (continued)

• TECHNICAL OPTIONS 1
• There is no silver bullet all mitigation
  options are burdened with costs, uncertainties,
  risks, and (usually) eventual diminishing returns
  to scale that will limit their contributions.
• A broad portfolio provides the best prospects for
  minimizing costs risks and hedging bets.
  (Socolow-Pacala wedges are a helpful way to
  think about this.)

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What I think I know

• TECHNICAL OPTIONS 2
• The portfolio must include large contributions
  from
• increased energy end-use efficiency in transport,
  buildings, industry
• CO2 capture sequestration from centralized
  fossil-fuel facilities, such as coal-burning
  power plants
• renewable energy sources, including biofuels,
  wind, photovoltaics
• afforestation, reforestation, and avoided
  deforestation
• The portfolio might or might not end up including
• a significant contribution from nuclear energy
• mitigation via geo-technical engineering

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What I think I know

• POLICY
• Policy measures must be powerful enough to force
  not only the win-win measures but costlier
  measures such as CO2 capture sequestration.
• This means either economic incentives strong
  enough to motivate capture/sequestration
  probably 100/tC (27/tCO2) or more as a carbon
  tax or emission-permit price in a cap-and-trade
  approach or regulations that flatly prescribe
  the needed behavior.
• And we must get there quickly, not least because
  of the long operating lifetime of coal-burning
  power plants currently being designed and
  deployed without provision for retrofit to
  capture CO2.

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What I think I know

• ECONOMICS
• The costs of prudent mitigation will not be
  small, but neither will they be catastrophic.
• Current global CO2 emission rate from fossil
  fuels deforestation is 9-10 billion tonnes of C
  per year. If we were paying 100/tC to avoid
  half of it, that would be 500 billion/year (and
  this would be a transfer, not money down a black
  hole). 100/tC on all of it would be 1
  trillion/year, about 2 of the Global World
  Product.
• More sophisticated analyses of mitigation costs
  for stabilizing at 550 ppmv CO2e come out in the
  range of 0.5 to 2 of GWP in 2100.
• Value of averted damages is probably far larger.

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Supplementary Material
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Reality, pace, and impacts
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Is current climate change unusual?
1000 years of proxy surface temperatures, 100
from thermometers
National Research Council, 2006
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Thermometers global T has risen 0.8C in 125 yrs
C
Green bars show 95 confidence intervals
Upward trend continues 2005 was a new record
were at 0.8C above 1880-1900 average
0.5C since 1970.
J. Hansen et al., PNAS 103 14288-293 (26 Sept
2006)
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Coastal glaciers are retreating
Muir Glacier, Alaska, 1941-2004
August 1941
August 2004
NSIDC/WDC for Glaciology, Boulder, compiler.
2002, updated 2006. Online glacier photograph
database. Boulder, CO National Snow and Ice
Data Center.
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Shrinking mountain glaciers The famous snows of
Kilimanjaro have been shrinking rapidly in recent
decades and are nearly gone. This is
particularly significant because high-elevation
ice and snow near the equator does not vary much
except when climate is changing globally. The
decline between 1912 and 2000 was 81
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Sea ice is shrinking
Extent of Arctic summer ice in 1979 (top
satellite image) and in 2003 (lower satellite
image). North Polar ice cap is sea ice -- its
floating and so does not change sea level when it
melts. But the reduced reflectivity when the ice
is replaced by water amplifies the warming effect
of greenhouse gases.
NASA photograph
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Greenland ice Melting 1992, 2002, and 2005
Greenland summer surface melting, 1992-2005
1992
2002
2005
In 1992 scientists measured this amount of
melting in Greenland as indicated by red areas on
the map
Ten years later, in 2002, the melting was much
worse
And in 2005, it accelerated dramatically yet again
Source ACIA, 2004 and CIRES, 2005
20
Sea-level rise has been faster than predicted
Global Sea-level rise as recorded by satellite
measurements (upper line with linear trend), with
IPCC projections (2001a) and range of
uncertainty. Source Cazenave and Nerem, 2004
21
The main cause of the CO2 build-up in the last
250 years has been emissions from fossil fuels
deforestation
Fossil-fuel contribution is confirmed by reduced
C-14 content of atmospheric CO2. Fossil fuels
provide 80 of civilizations energy today.
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(A) Forcings used to drive climate simu-
lations.
(B) Simulated and observed surface temperature
change.
Source Hansen et al., Earth's energy imbalance
Confirmation and implications. Science 308, 1431,
2005.
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Where were headed under BAU
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Where are we headed? The
next 100 years compared to the last 1000
Projections of global average surface temperature
show were heading for a climatic state far
outside the range of variation of the last 1000
years. Indeed, were on our way to making the
world hotter in the 21st century than its been
in the last million years, possibly hotter than
in the last 30 million years.
IPCC 2001scenarios to 2100 ----------------?
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CO2 doubling is not the end of BAU The two globes
summarize computer simulations performed by the
Princeton Geophysical Fluid Dynamics Lab to
compare the warming expected under a doubling of
CO2 from the pre-industrial level with the
warming expected from a quadrupling. Note that
N hemisphere mid-continent average warming in the
4xCO2 world is 15-25F! This is a roasted
world.
T changes for 2x CO2
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Mitigation options prospects
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Future BAU emissions path compared to paths for
stabilizing CO2 concentration to limit ?Taverage
BAU (gt6C)
(3C)
(2C)
The path to avoid ?Tavg gt2C (gold) requires much
earlier, more drastic action than path to avoid
gt3C (green).
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Stabilizing at 450-500 ppmv would be possible if
emissions were flat for 50 years, then declined.
28
Emissions proportional to economic growth
The green stabilization triangle represents the
emissions that should could be avoided by new
policies (a depiction due to Socolow Pacala).
Reduced carbon intensity of the baseline economy
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GtC/yr
Virtual Triangle
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Currently projected path
Stabilization Triangle
Historical emissions
7
Flat path
1.9
0
2055
2005
1955
The virtual triangle results more from structural
shifts in the economy (toward services) and less
from the carbon-saving activity required to fill
the stabilization triangle.
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The triangle can be filled by a portfolio of 7
wedges
Each wedge accounts for 1 GtC/yr in 2055
Methane Management
Energy Efficiency
Forests Soils
14 GtC/y
Fuel Displacement by Low-Carbon Electricity
Stabilization
Decarbonized Electricity
Triangle
7 GtC/y
2055
2005
2005
2004
2054
Decarbonized Fuels
This particular set of wedges is only
illustra-tive, not prescriptive.
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There are more than 7 wedges to choose from
Here are 15 candidates.
31
Emission paths for stabilization at 550 ppmv
CO2-equiv (Stern Review, 2006)