CE 107: Climate-Change Mitigation
Lecture #1: Overture
24 August 2012
Bill Nazaroff
CEE Dept.
UC Berkeley
California, USA
Cartoon: Tokoro Yukiyoshi

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Issues
•
•
•
•

Is anthropogenic climate change happening?
What can we expect for the future under BAU*?
What can we do about it?
What are we doing about it?

*BAU = “business as usual”

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Atmosphere affects Earth’s energy balance

Source: IPCC, Climate Change 2007: The Physical Science Basis, Ch 1.

3


Atmosphere naturally warms the earth
Global average
surface temperature
is increased by 35 K
because
atmospheric gases
absorb in the
infrared and are
transparent in the
visible.

4


Atmospheric CO2 levels are rising

CD Keeling (1928-2005)

source: mlo145e_thrudc04.pdf

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Fossil-fuel use: A major cause for rising CO2

1 GtC = 1 billion tonnes of carbon


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Consequences: Increased radiative forcing

Source: IPCC (2007) — Summary for Policymakers

7


What will happen as a result?

WS Broecker (1931-), Columbia University

Broecker (2000) has likened our release of greenhouse gases to the
atmosphere to poking an angry beast with a stick! We’re not sure what
will happen, but chances are it won’t be good!
Source: WS Broecker, Annual Review of Energy and the Environment 25, 1-19, 2000.

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Where are we headed under BAU? (IPCC)

Source: IPCC, Climate Change 2007 — The Physical Science Basis

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Global warming in time and space (IPCC)

Source: IPCC, Climate Change 2007 — The Physical Science Basis

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Anticipate diverse & escalating disturbances
Partial list:
• Water — Hundreds of millions of people exposed to
increased water stress
• Ecosystems — Significant extinctions around the globe
• Food — Complex, localized impacts on small holders,
subsistence farmers and fishers
• Coasts — Increased damage from floods and storms
• Health — Increased burden from malnutrition, diarrheal,
cardiorespiratory, and infectious diseases
Source: IPCC, Climate Change 2007 — Climate Change Impacts, Adaptation and Vulnerability

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Projected climate-change impacts: California
• Public health — Degraded air quality; more heat stress
• Water — Strained water supplies; diminished hydropower
production; loss of winter recreation
• Agriculture — Expanding ranges of weeds; increased threats
from pests and pathogens
• Forests & landscapes — Increasing wildfires; shifting
vegetation; declining forest productivity

• Rising sea level — Increased coastal flooding; shrinking
beaches
Source: Our Changing Climate — Assessing the Risks to California ()

12


Mitigation? Stabilize atmospheric CO2 levels
Atmospheric CO2 levels:
preindustrial ~ 280 ppm
today ~ 390 ppm
Emission rates:
today ~ 6 GtC/y
2100, BAU ~ 20 GtC/y
2100, WRE450 ~ 3 GtC/y
Need 7x decrease from BAU

• Aggressive measures required to stabilize at 450 ppm CO2.
• Still may not suffice to prevent serious environmental damage.
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Per-capita fossil-C emission targets

Notes:

(1) Lines labeled with atmospheric CO2 stabilization levels (ppm);
(2) Population projection peaks at 9 billion in 2070.

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Pause: Comic relief
The picture’s pretty bleak
… The world’s climates
are changing, the
mammals are taking over,
and we all have a brain
about the size of a walnut.
- Gary Larson
The Far Side
copyright 1985
Universal Press Syndicate.
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What to do? A supply-side proposition…
Space-based power systems

Mega-scale renewables

“Primary power consumption today is ~ 12 TW,
of which 85% is fossil-fueled. Stabilization at
550, 450, and 350 ppm CO2 … require
emission-free power by mid-century of 15, 25,
and > 30 TW, respectively.”
Source: MI Hoffert et al., Science, 298, 981-987, 2002.

Nuclear fusion


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Alternative prescription: Stabilization triangle

Source: />
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Stabilization wedges: Portfolio approach
•
•
•
•

Referenced to “business as usual.”
Grow from 0 today to 1 GtC/y by 2055
Saves 25 GtC during 2005-2055
Need 7 wedges to avoid
l
a
u
CO2 rise to 550 ppm
s
u
s
a
s
• 7 wedges = 175 GtC
es

in
s
bu

stabilization trajectory (550 ppm)
Source: S Pacala and R Socolow, Science, 305, 968-972, 2004.

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Wedges — End use, supply, C mgmt
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•
•
•
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Energy efficiency & conservation (4 options)
Renewable electricity & fuels (4)
Fuel shift (1)
Nuclear fission (1)
CO2 capture and storage (3)
Forests & agricultural soils (2)

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Stabilization wedges: Good news/Bad news
• Good: 15 candidate wedges identified; only 7 needed

• Good: Technology already exists for each wedge:
only scale-up required
• Bad: Each wedge will require substantial societal effort
• Bad: Stabilization at 550 ppm will not prevent damage
• Bad: Need to save 350 GtC vs. BAU during 2050-2100

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Mitigation: What else might be considered?
• Behavioral changes affecting consumption:
A conservation ethic — “sufficiency”
• Climate geoengineering

John Muir (1838-1914)

Edward Teller (1908-2003)

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Conservation ethic: Who advocates for it?
“We don't need bigger cars or fancier
clothes. We need self-respect, identity,
community, love, variety, beauty,
challenge, and a purpose in living that is
greater than material accumulation. The
ads tell us that bigger cars and fancier
clothes will bring us those nonmaterial
benefits, but of course the ads lie. By

selling us things that promise to fill our
inner emptiness but ultimately don't, they
set us up to want more, and more, and
more. You can never get enough of what
you don't really need.”

Donella (Dana) Meadows (1941-2001)

Source: D Meadows, “What does sustainability mean? ( 23 April 1992.

22


Climate geoengineering: Some concepts

Injection of sulfate particles into the stratosphere
Space-based solar “parasol”
sources: UCRL-JC-128715, LLNL, Livermore, California, August 1997; Science, 298, 981-987, 2002.

23


Climate geoengineering: Two views
“Humanity may inevitably grow into active planetary
management, yet we would be wise to begin with a renewed
commitment to reduce our interference in natural systems
rather than to act by balancing one interference with another.”
— D Keith, Ann. Rev. Energy Environ. 25, 245, 2000.

“Given the grossly disappointing international political

response to the required greenhouse gas emissions …
research on the feasibility and environmental consequences
of climate geoengineering … should not be tabooed.”
— PJ Crutzen, Climatic Change 77, 211-219, 2006.
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What are we doing about CCM? (California)
• Executive order S-3-05: Reduce emissions
–
–
–
–

By 2010 to 2000 levels
By 2020 to 1990 levels (*)
By 2050 to 80% below 1990 levels (*)
Despite major population growth (to 50-70 million by 2050)

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(*) Not yet clear that the goals will be achieved

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