Tom Ackerman
Professor, Department of Atmospheric Sciences
Planet Earth has warmed over the
last 100 years
Data analyzed by Hadley Research Centre, United Kingdom
Probable Cause
Increase in greenhouse gas
concentrations
Antarctic Ice Core Data
390
370
CO2 Concentration, ppm
Mauna Loa Data
350
330
310
Pre-industrial level
290
270
250
1000
1100
1200
1300
1400
1500
Year
1600
1700
1800
1900
2000
Atmosphere Carbon balance
Fossil fuel emission
6.1 GTon / year
Deforestation
1.5 GTon /year
Total
~7.5 GT / year
Increasing CO2 in atmosphere
3 GT / year
Uptake in mixed layer
2.5 GT / year
Reforestation in NA
0.5 GT / year
Total
~ 6 GT / year
The Facts
Surface temperature is increasing
 Increase is unprecedented in last 1000
years (and probably more)
 CO2 is on the rise – up about 35%
 About 20% of the CO2 emission cannot be
accounted for at present!
 Increasing CO2 causes increasing surface
temperature

Okay, so the question is:
What’s going to happen to global
climate over the next 10 to 50 years?
Corollary:
How would we know?
Let’s build a CLIMATE model!
What do we need in our climate model?
Atmosphere
H2O vapor and Clouds
Absorbing gases – CO2
Aerosol
Ice
Sea ice
Ice sheets (glaciers)
Biota
Surface vegetation
Ocean
Complete 4D model
Coordinates:
Latitude
Longitude
Height
Time
Constructing a climate model



Decide on the variables – what do we want to
predict?
T, wind speed (3D), water vapor concentration
Write down time-dependent equations
Temp (time = t + t) = Temp (time = t)
+ (all the things that change the temperature)

Can’t solve these equations exactly
How big is big?
300 km x 300 km
Typical values for current
ATMOSPHERE ONLY climate
models
5 variables (minimum)
8190 boxes
26 vertical levels
30 minute time step (48/day)
51.1 million equations / day
18.6 billion equations / year
Climate modeling challenges the biggest
computers
CRAY
Japanese Earth Simulator
IBM Blue Sky (NCAR)
Let’s RUN our climate model!
How to run a climate model
Prescribed forcing
(Sun, CO2, etc.)
Initial
condition
s
Coupled Global
Climate Model
Atmosphere
Run forward in time for at
least 10 to 30 years
Ocean
Compare averaged model
results with averaged
climate results
Major questions

Can we simulate climate change over the
past 100 years?

Is it possible that the current increase in
temperature is a result of natural variability
in the climate system?
Simulating the last 150 years

Input natural forcing into climate model
Volcanic aerosol
 Solar activity


Input anthropogenic forcing
CO2 and other greenhouse gases
 Sulfate aerosol


Input both
IPCC Conclusion
In the light of new evidence and taking into
account the remaining uncertainties, most
of the observed warming over the last 50
years is likely to be due to the increases in
greenhouse gas concentrations.
Predicting the future
Intergovernmental Panel on Climate Change
(IPCC) – est. 1988
IPCC is an assessment activity –
it does not sponsor research or
monitor climate
Information chain leading to a climate projection
Projecting the future: Scenarios

Estimate future emissions of greenhouse
gases and pollutants
CO2
 Other greenhouse gases
 Aerosol (sulfate, carbon)

Year
[CO2]
ppmv
1973
330
1983
343
1993
357
2004
377
Rate of increase in CO2 due to emissions:
73 – 03
1.5 ppmv / year
93 – 03
1.8 ppmv / year
Assumption: we can tolerate a climate
change corresponding to 600 ppmv
Question:
1. How many years will it take to reach 600 ppmv at an emission rate
of 1.5 ppmv / year?
Currently (2004) at 377 ppmv
 Amount of extra CO2:
600 – 377 = 223 ppmv
 Length of time to accumulate
= amount / rate
= 223 ppmv / (1.5 ppmv / year)
= 149 years

Year
[CO2]
ppmv
1973
330
1983
343
1993
357
2004
377
Rate of increase in CO2 due to emissions:
73 – 03
1.5 ppmv / year
93 – 03
1.8 ppmv / year
Assumption: we can tolerate a climate
change corresponding to 600 ppmv
Questions:
1. How many years will it take to reach 600 ppmv at an emission rate
of 1.5 ppmv / year? = 149 years
2. At an emission rate of 1.8 ppmv / year? = 124 years
3. So what are we worried about?
IPCC Scenarios
A1: A world of rapid economic growth and
rapid introductions of new and more efficient
technologies
A2: A very heterogenous world with an
emphasis on familiy values and local
traditions
B1: A world of „dematerialization“ and
introduction of clean technologies
B2: A world with an emphasis on local
solutions to economic and environmental
sustainability
IS92a „business as usual“ scenario (1992)
Emissions scale with population
Population increases exponentially (not linearly)
Emissions increase exponentially (not linearly)
Summary: Scenarios
CO2 concentrations in this century vary
widely depending on assumptions about
technology use and energy mix
 By 2100, we could have CO2
concentrations exceeding 900 ppmv; hard
to see how we would have less than ~ 500
ppmv

So now let’s put those CO2
estimates into our climate model
(“force” our model with CO2)
Start of Lecture 2
Where we are …
“Built” a climate model
 Used the climate model to simulate last
150 years – did a pretty good job
 Developed scenarios for the future –
based on projected energy use
 Started to look at climate change over this
during this century

IPCC Scenarios
A1: A world of rapid economic growth and
rapid introductions of new and more efficient
technologies
A2: A very heterogenous world with an
emphasis on familiy values and local
traditions
B1: A world of „dematerialization“ and
introduction of clean technologies
B2: A world with an emphasis on local
solutions to economic and environmental
sustainability
IS92a „business as usual“ scenario (1992)
Updated: 13 Feb 2007
Figure SPM-5
Figure SPM-6
Sea level rise
“Commitment”
Even if we stopped emitting CO2 today,
we are committed to more warming and
more sea level rise because we have to
wait for the climate system to come into
equilibrium with the current atmospheric
concentration of CO2
Summary of effects (very certain)

The globally averaged surface temperature is projected
to increase by 1.4 to 5.8°C by 2100.


The projected rate of warming is much larger than the observed
changes during the 20th century and is very likely to be without
precedent during at least the last 10,000 years.
Global mean sea level is projected to rise by 0.1 to 0.9
meters between 1990 and 2100.


Global mean surface temperature increases and rising sea
level from thermal expansion of the ocean are projected to
continue for hundreds of years after stabilisation of greenhouse
gas concentrations (even at present levels)
Could be more if ice sheets experience catastrophic failure
Figure SPM-7
Summary of effects (probable)
We expect
 Greater year-to-year variability in precipitation
 More intense precipitation events
 Higher frequency of hot to very-hot days
 Increased risk of summer drought over continental
interiors
 Decrease in NH snow cover and sea ice extent
 Continued shrinking of glaciers and ice caps
 Antarctic ice sheet will increase in mass (increased
precipitation), while Greenland ice sheet will decrease
So what does this mean for us?



From an article in the February 20, 2004
issue of Science
Changes in regional
hydrology – more rain
with less snow pack
Reduced stream flow in
summer – impacts on
fisheries and irrigation
Increased storm surge
and coastal erosion
So what do we do about this?
1992 United Nations Framework
Convention on Climate Change
GOAL: “…stabilization of greenhouse
gas concentrations in the atmosphere
at a level that would prevent dangerous
anthropogenic interference with the
climate system.” (Article 2)
P.S. Our country is a signatory!
Four types of policy responses
1. Emissions mitigation (reduce
CO2 output)
2. Adaptation (design to meet
expected changes)
3. Improvement in scientific
understanding
4. Technology development
If we are going to stabilize climate,
we have to stabilize atmosphere CO2,
which means,
we have to drive anthropogenic CO2
emissions to 0!
THIS IS SCARY!
Implicit assumption of major technological
change over the next century
50.0
This improvement presumes
fully developed:
Solar
Nuclear
Efficient Fossil Electric
Advanced Transportation
End Use Efficiency
45.0
40.0
IS92a(1990 technology)
35.0
PgC/yr
30.0
IS92a
550 Ceiling
25.0
20.0
15.0
10.0
5.0
0.0
1990
2010
2030
2050
2070
2090
Stabilization requires
additional policies and
technology developments
that can compete
economically because
carbon has a ‘value’
What are some of the key “new”
technologies?

Carbon capture and disposal


Renewable resources (physical and chemical)


The removal of carbon from a fossil fuel process stream and the
disposal of it in a place well-isolated from the atmosphere.
Wind, solar, ocean tides
Hydrogen
Theuse
current
energy supply
(fossil fuel)
is NOT
freespoken
market.of as
The
of hydrogen
as an energy
carrier,
usually
It isfuel cells with many applications, most notably transportation
• cartel owned
 ‘Modern’
biomass
• The
internationally
a handful
of large

emergencedominated
of energy by
crops
as a source
of corporations
hydrocarbons
from regulated,
the fast part
of the carbon
cycle
• derived
government
subsidized
and taxed

 These
technologies are not cheap and will not be
competitive with fossil fuels unless we subsidize them
Current US Policy

Rejected Kyoto accord -- 2001
Kyoto plan called for reductions in absolute GHG
Basically
business countries,
as usual! but no
emissions for
industrialized
For the last 25 years (dating from the first oil crisis in the late 70’s),
reductions
forofdeveloping
this rate
reduction hascountries
been about 1.6%!


Announced plan to reduce GHG emissions as a
function of GDP (Gross Domestic Product) –
business
as usual!
2002 at rateBasically
of 1.8%
per year
Simply replaced the US Global Change Research Program

Implemented Climate Change Science Program
(CCSP) -- 2002
What about improved
understanding?

Research effort driven by federal budget
Budget numbers in Millions of $US
3,000,000
2,500,000
1998
1999
2000
2001
2002
2003
2004
2005
2,000,000
1,500,000
1,000,000
500,000
0
Total US Budget
Defense Dept.
Climate research
Budget numbers in Millions of $US
1400
$1480 / year for every
person in the US
Does not include supplementary
appropriation for Iraq war
1200
1000
$2.70 / year for every
person in the US
800
600
400
200
0
Defense Dept (By day)
Climate research
1998
1999
2000
2001
2002
2003
2004
2005
US Policy Response

Emissions mitigation

Business as usual

Adaptation

No plans

Improved understanding


Technology development
No new research focus;
static funding for a
decade
Limited and poorly
focused (freedom car)

Policy Summary

We (the US) are the largest part of the problem but
have NO COHERENT STRATEGY to address it
(I could say that our current “policy” has moved from
benign neglect to active opposition.)
The Global Greenhouse Problem
We can mitigate the problem but we must
begin to act NOW!
 CO2 molecules have a long lifetime – the
molecule you emit today will still be in the
atmosphere in 100 years
 The molecule you don’t emit is one less
“commitment” to global warming

A technological
strategy
Stabilization Wedges:
Solving the Climate
Problem
for the Next 50 Years with
Current Technologies
S. Pacala and R. Socolow
(Science, 2004)
Nuclear power
Hybrid cars
Not all wedges are equal – some have more effect early in the process,
others take much longer; some are easier than others; some will fail!
Types of Wedges

Conservation and efficiency





Efficient cars (hybrid, H2)
Reduce dependence on cars
Improved building efficiency
Shift to more efficient fuels
Agriculture
Types of Wedges

Conservation and efficiency






Renewables






Efficient cars (hybrid, H2)
Reduce dependence on cars
Improved building efficiency
Shift to more efficient fuels
Agriculture
Solar
Wind
Biomass
Nuclear
CO2 sequestration
Increase standing biomass (reforestation)
In summary
The Global Greenhouse Problem




Is REAL -- we will continue to add CO2 to the atmosphere
and the climate will warm.
Is LONG TERM -- a problem for decades, not years =>
YOUR PROBLEM!
Has IMPLICATIONS FOR SOCIETY -- global warming will
impact water resources, agriculture, energy usage, severe
weather damage, sea level, etc., on a regional basis.
We (the US) are the largest part of the problem but have
NO COHERENT STRATEGY to address it
The Global Greenhouse Problem


PRESENTS DIFFICULT ETHICAL AND MORAL
CHOICES -- in any plausible forecast of the future,
there will be losers; there may be some winners.
The biggest losers will most likely not be those who are
most responsible for the change in climate.
 Who pays for their losses?
 With what currency?
 On what time scale?