Transcript Himalaya climate change

Saving the planet: Emissions scenarios, stabilization
issues, and uncertainties
“NCAR Summer Colloquium on Climate and Health”
NCAR, Boulder, CO.
19 July, 2006
Tom Wigley,
National Center for Atmospheric Research, Boulder, CO.
Introduction
The climate change problem is essentially an energy problem that
requires moving away from the use of fossil fuels as our primary
energy source.
This will almost certainly require the development of new “carbon-free”
(or “carbon neutral”) energy technologies.
To determine the magnitude of this technological challenge we need to
know what will happen in the absence of policies to limit climate
change, and what a safe level may be for future climate change.
Summary
Climate changes observed over the 20th century
Future climate change: the no-policy case
Future climate change: stabilization policies
Future changes in energy production
Carbon-free energy requirements for stabilization
Technology options
The ‘wedge’ concept
Geoengineering
PAST CLIMATE CHANGE
Observed temperature changes
5 of the 6 warmest
years have
occurred this
decade.
1998 was unusually
warm due to a large
El Niño that
occurred in 1997/8.
FUTURE CLIMATE CHANGE
(in the absence of policies to reduce climate change)
The SRES ‘no-policy’ emissions scenarios
• The Intergovernmental Panel on Climate Change (IPCC) has
sponsored production of a set of 40 ‘no-climate-policy’ emissions
scenarios for GHGs, sulfur dioxide, and other gases
• These scenarios are based on a range of assumptions for future
population and economic growth, technological change, etc., grouped
into four families or ‘storylines’ (A1, A2, B1, B2)
• The scenarios are published in a Special Report on Emissions
Scenarios – hence the acronym SRES
• Six of these scenarios have been used for detailed climate
calculations (A1B, A1FI, A1T, A2, B1, B2)
“Special Report on Emissions Scenarios”, Eds. N. Nakicenovic & R. Swart, C.U.P. (2000)
SRES scenarios: Family characteristics
A
1
2
B
DRIVING THEMES
Economics
Environmentalism
Globalism
Market forces
Sustainable development
Economic and
technological
convergence
Economic and technological
convergence
Market forces
Sustainable development
Slower economic
growth
Slower economic growth
Regionalization
SRES population projections
Economic growth: per capita GDP
SRES fossil CO2 emissions
Remember, the
‘B’ scenarios
focus on
sustainable
development.
SRES CO2 concentration projections
NOTE: Increasing CO2
is not only a climate
problem.
Increasing CO2 makes
the ocean more acidic,
eventually making it
impossible for carbonate
shell-producing animals
to produce shells.
Extinction of these
animals will upset the
ocean food chain and
could lead to much
larger scale extinctions
RELATIVE IMPORTANCE OF CO2
2000–2100 radiative forcing breakdown
Factor
A1B
A1FI
A1T
A2
B1
B2
CO2
3.59
(73%)
5.35
(67%)
2.45
(63%)
4.60
(66%)
2.07
(71%)
2.83
(63%)
CH4
0.08
0.64
0.15
0.63
–0.08
0.41
N2O
0.17
0.43
0.12
0.39
0.18
0.14
Trop. Ozone
0.14
0.88
0.10
0.86
–0.16
0.42
Aerosols
0.62
0.57
0.79
0.17
0.79
0.43
Montreal
gases
–0.23
–0.23
–0.23
–0.23
–0.23
–0.23
Other halos
0.30
0.30
0.31
0.30
0.14
0.28
Strat.
Ozone
0.20
0.20
0.20
0.20
0.20
0.20
TOTAL
4.89
8.03
3.89
6.92
2.92
4.49
(% of total
forcing)
NOTE: Dominant role of CO2
Global-mean temperature projections
Future warming compared with the past
THE POLICY CASE: CONCENTRATION
STABILIZATION
Article 2 of the UNFCCC
Article 2 provides the basis for climate policy. Its
objective is …
“stabilization of greenhouse gas concentrations …..
at a level that would prevent dangerous anthropogenic
interference with the climate system ….. within a timeframe sufficient to allow ecosystems to adapt naturally to
climate change, to ensure that food production is not
threatened and to enable economic development to
proceed in a sustainable manner”.
CO2 stabilization pathways
POINTS TO NOTE
1.
Stabilization of CO2 concentration
requires, eventually, very large
reductions in CO2 emissions. The
arrow shows the reduction in 2050
if we wish to stabilize at 450ppm
2.
Since most CO2 comes from
energy usage, stabilizing CO2
requires that we need to obtain a
large fraction of future energy from
carbon-free sources.
3.
A key issue is, what should the
stabilization level be in order to
avoid “dangerous interference with
the climate system”?
FUTURE ENERGY PRODUCTION IN THE
NO-CLIMATE POLICY CASE (SRES
SCENARIOS)
PRIMARY ENERGY BREAKDOWN
NOTE: Even in the absence
of climate policies, large
increases are projected
for carbon-free energy
HOW MUCH ADDITIONAL CARBON-FREE
ENERGY IS REQUIRED FOR CO2
CONCENTRATION STABILIZATION?
The answer depends on the assumed no-policy baseline scenario (35
possibilities in the SRES scenario set) – and on the chosen
concentration stabilization level (also a wide range of possibilities).
This implies a wide uncertainty range.
Carbon-free energy requirements
EXAMPLE:
The blue lines show how much
carbon-free energy is already
built into the baseline scenarios
In the B1 case, the vertical arrow
shows the additional carbon-free
energy required to move from the
no-policy B1 scenario to the
WRE450 stabilization pathway.
Note that B1 is a very optimistic
scenario – other baseline
scenarios require much greater
amounts of additional carbonfree energy.
Extra carbon-free energy needed in 2050 (TW)
STAB
BASE
Carbonfree in
BASE*
WRE350 WRE450 WRE550
WRE650
WRE750
A1B
15.3
24.6
18.5
10.8
6.7
4.4
A1FI
8.7
34.1
28.4
21.3
17.4
15.3
A1T
16.5
19.1
12.7
4.6
0.3
--
A2
5.5
22.8
17.3
10.4
6.7
4.7
B1
7.8
15.5
10.0
3.1
--
--
B2
8.2
16.6
10.4
2.7
--
--
* Current carbon-free energy  2TW
Extra carbon-free energy needed in 2050 (TW)
STAB
BASE
Carbon-free
WRE350
WRE450
WRE550
WRE650
WRE750
in BASE*
A1B
15.3
24.6
18.5
10.8
6.7
4.4
A1FI
8.7
34.1
28.4
21.3
17.4
15.3
A1T
16.5
19.1
12.7
4.6
0.3
--
A2
5.5
22.8
17.3
10.4
6.7
4.7
B1
7.8
15.5
10.0
3.1
--
--
B2
8.2
16.6
10.4
2.7
--
--
* Current carbon-free energy  2TW
POINTS TO NOTE
(1) The baseline scenarios show large increases in carbon-free
energy even in the absence of climate policies. This limits the
options for additional carbon-free energy.
(2) The large amounts of carbon-free energy required for
stabilization levels of 450ppm or less will almost certainly
require the development of new technologies.
TECHNOLOGY OPTIONS
CO2 emissions reduction opportunities
TYPE
METHOD
Transport
More efficient vehicles
Electricity
PROBLEMS
Renewable fuels
Energy for production, land availability
Fuel shifting (coal to oil to gas)
Limited oil reserves
Coal gasification
Efficiency limit
Once-through and breeder reactors Limited uranium, cost, public opinion
CCS
Fusion
Could be 50+ years away
Terrestrial solar
Land availability, storage, transmission
Space solar
Launch costs
Wind
Land availability, storage, transmission
CO2 Capture* and Storage
Storage reservoirs, leakage
* Includes direct capture from the atmosphere
TECHNOLOGY “WEDGES”
Pacala & Socolow wedges
A ‘wedge’ is a single
existing technology
that can be scaled up
to reduce CO2
emissions by 1GyC/yr
in 2055; or reduce
cumulative emissions
over 2005–2055 by
25GtC.
Pacala and Socolow
claim that a 500 ppm
stabilization pathway can
be followed, at least to
2055, using existing
technology. This is
incorrect.
S. Pacala & R.Socolow: Science 305, 968–972 (2004)
Baseline wedges
The flaw in Pacala and
Socolow is that they fail
to account for wedges
already built into the
baseline scenario.
SRES baselines all
contain a large amount
of carbon-free energy
growth (red arrow) that
arises spontaneously, in
the absence of climate
policy.
Wedges required for stabilization
(through to 2055)
STAB
WRE350 WRE450 WRE550 WRE650 WRE750
BASE
A1B : 38
15
11
6
4
2
A1FI: 25
23
19
15
12
11
A1T : 45
11
7
2
--
--
A2
: 8
17
13
8
5
4
B1
: 29
10
6
2
--
--
B2
: 18
11
7
2
--
--
Wedges already built into no-policy baseline:
neglected by Pacala and Socolow.
Wedges required for stabilization
(through to 2055)
STAB
WRE350
WRE450
WRE550
WRE650
WRE750
BASE
15
11
6
4
2
A1FI: 25
23
19
15
12
11
A1T : 45
11
7
2
--
--
A1B :
38
A2
:
8
17
13
8
5
4
B1
: 29
10
6
2
--
--
B2
: 18
11
7
2
--
--
Wedges already built into no-policy baseline
POINTS TO NOTE
(1)
Pacala and Socolow identify 15 existing technology
wedges, each of which could be scaled up to reduce
emissions in 2055 by 1GtC/yr
(2)
However, the total number of wedges required to follow
WRE450 to 2055 is between 21 and 49
(3)
We therefore need to develop new carbon-free energy
technologies – probably requiring a massive investment
in research, demonstration and dissemination.
OTHER TECHNOLOGY OPTIONS:
GEOENGINEERING
Geoengineering (1)
• Reducing CO2 emissions (“mitigation” -- i.e., moving from the use of
fossil fuels as our primary energy source to the use of carbon-free
energy technologies) is the standard “solution” to the climate
problem. Geoengineering is an alternative approach.
• Geoengineering aims to offset CO2-induced climate change by
deliberately altering the climate system.
• The earliest suggestion was to inject aerosol-producing substances
into the stratosphere to provide a cooling shield – i.e., to produce a
human volcano.
Geoengineering (2)
• The problem with geoengineering as a single solution is that our use
of fossil fuels creates two problems, climate change and increasing
CO2.
• Increasing CO2 makes the oceans more acidic and could lead to the
extinction of all carbonate shell producing animals in the ocean.
• As these animals are at the bottom of the food chain, their extinction
could lead to the extinction of all life in the ocean.
• Geoengineering cannot replace mitigation (i.e., the reduction in fossil
fuel use), but it may make mitigation easier.
Effect of multiple volcanic eruptions
MULTIPLE PINATUBOS
As an analogy, we consider
a case where we know the
effects of a known injection
of SO2 into the stratosphere,
the eruption of Mt Pinatubo
(June, 1991)
Pinatubo released 10TgS of
SO2 into the stratosphere.
This is 15-20% of the current
amount of SO2 that we
release each year into the
troposphere. The eruption
cooled the planet by 0.5 –
0.7oC.
Alternative geoengineering scenarios
Scenarios like these
produce immediate
cooling, offsetting the
short-term effects of
increasing CO2.
This means that, with
geoengineering, we would
not have to reduce CO2
concentrations or
emissions so rapidly.
-3W/m2 is equivalent to Pinatubo every two years (5TgS/yr)
This gives us more time to
develop alternative, costeffective carbon-free
energy sources.
Concentrations and implied emissions
Overshoot is the case that
includes geoengineering.
Note how this gives us much
more time (around 20 years)
to begin the required rapid
reduction in CO2 emissions –
i.e., more time to phase out
existing energy systems and
develop alternative
technologies.
Geoengineering effects on climate
The important
comparison here is
between WRE450
(mitigation alone) and
LOW, MID or HIGH
GEO (geoengineering
combined with slower
mitigation, but with the
same CO2 stabilization
level).
CONCLUSIONS
1.
Global warming is primarily an energy problem.
2.
The problem, however, is two-fold – involving both climate change and the
effects of increasing CO2 on ocean acidity.
3.
Solving both problems requires satisfying very large future energy demands
with, primarily, carbon-free energy sources.
4.
Projected carbon-free energy requirements are extremely large. They cannot
be satisfied with current technology.
5.
Large investments are required to develop these new technologies.
6.
Moderate intervention using geoengineering could give us time to develop and
implement these new technologies.
Thankyou