Transcript Hubbert’s Peak and Climate Change

Hubbert’s Peak, The Question of Coal,
and Climate Change
Dave Rutledge
Chair, Division of Engineering and Applied Science
Caltech
“There is something fascinating about science.
One gets such wholesale returns of conjecture
out of such a trifling investment of fact.”
Mark Twain
Life on the Mississippi
slides (.ppt) and spreadsheets (.xls) at http://rutledge.caltech.edu/
1
The UN Panel on Climate Change
• The UN Intergovernmental Panel on
Climate Change publishes assessment
reports that reflect the consensus on
climate change
• The 4th report is being released this year
– Over one thousand authors
– Over one thousand reviewers
• Updated measurements show that the
temperature is rising 0.013C per year
(1956-2005)
2
IPCC Climate-Change Predictions
• Report discusses climate simulations for
fossil-fuel carbon-emission scenarios
• There are 40 scenarios, each
considered to be equally valid, with story
lines and different government policies,
population projections, and economic
models
3
Annual Fossil-Fuel Carbon Emissions, Gt
The 40 UN IPCC Scenarios
40
A1C AIM
30
20
10
B1T Message
0
1980
2000
2020
2040
2060
2080
2100
Carbon Emitted
A1 AIM
A1 ASF
A1 Image
A1 Message
A1 Minicam
A1 Maria
A1C AIM
A1C Message
A1C Minicam
A1G AIM
A1G Message
A1G Minicam
A1V1 Minicam
A1V2 Minicam
A1T AIM
A1T Message
A1T Maria
A2 ASF
A2 AIM
A2G Image
A2 Message
A2 Minicam
A2-A1 Minicam
B1 Image
B1 AIM
B1 ASF
B1 Message
B1 Maria
B1 Minicam
B1T Message
B1High Message
B1High Minicam
B2 Message
B2 AIM
B2 ASF
B2 Image
B2 Maria
B2 Minicam
B2High Minicam
B2C Maria
•
•
•
•
Data from the EIA (open symbols, 1980 to 2004)
Emissions have increased 18% since the Kyoto Agreement was negotiated in 1997
Large differences in emissions among scenarios
Oil production in 17 of the scenarios is greater in 2100 than in 2005
4
The Wall Street Journal  April 5  Collapse of
the World’s Second-Highest Producing Oil Field
5
World crude-oil production fell in 2006 by roughly the amount of this drop
Outline
• The 4th UN IPCC Assessment Report
• Hubbert’s peak
–
–
–
–
The history of US oil production
How much oil do the Saudis have?
The future of world hydrocarbons
The Canadian oil sands
• The coal question
–
–
–
–
British coal, a nearly complete history
Chinese coal
American coal
The future of world coal, by regions
• Climate change
– Simulations of future temperature and sea level
– Carbon capture
– Wind and sun
• Concluding thoughts
6
King Hubbert
• Geophysicist at the Shell
lab in Houston
• In 1956, he presented a
paper “Nuclear Energy and
Fossil Fuels” at a meeting
of the American Petroleum
Institute in San Antonio
• He made predictions of the
peak year of US oil
production based on two
estimates of the ultimate
production
7
Hubbert’s Peak
•
•
•
From his 1956 paper
Hubbert drew these by hand, and integrated by counting squares
For the larger estimate, Hubbert predicted a peak in 1970
8
Annual Crude-Oil Production, billions of barrels.
What Actually Happened?
1970 Hubbert’s Peak
Alaskan oil
3
2
1
0
1900
•
•
1920
1940
1960
1980
2000
Data from the DOE’s Energy Information Administration (EIA)
Production has dropped 15 years in a row
9
Cumulative Production, billions of barrels.
US Crude-Oil Production
200
29Gb remaining
100
0
1900
•
•
•
1950
2000
2050
2100
EIA data (1859-2006)
Cumulative normal (lms fit for ultimate of 225Gb, mean of 1975, and sd of 28 years)
Hubbert’s larger ultimate was 200 billion barrels (the Alaska trend is 19 billion barrels)
10
The Largest US Oil Field
Prudhoe Bay, Alaska
Discovered 1968
11
Annual Production, millions of barrels .
Prudhoe Bay Oil Production
600
400
200
Trend for ultimate
is 12 billion barrels
0
0
5
10
Cumulative Production, billions of barrels
•
•
FY1977-2006 data from the Alaska Department of Revenue, Tax Division
Initially considered as 8 billion barrels of reserves
12
Estimating Remaining Production
from Reserves is Challenging
• Reserves refer to fossil fuels that are appropriate to
produce, taking the price into account
• Reserves may be listed conservatively, as for
Prudhoe Bay
• Coal reserves have been too high, and they are often
not properly distinguished from resources, which are
volume estimates for coal seams of a minimum
thickness and a maximum depth
• Often reserves are not adjusted for production
• New discoveries are important for oil and natural gas
• In most countries, the details of oil reserves are
secret, and this means that the published reserves
are political statements
13
OPEC Reserves Go Up
When the Price Goes Down!
Iran
20
Iraq
50
Kuwait
UAE
10
Price
0
1975
•
•
30
100
1980
1985
1990
1995
2000
Price, dollars per barrel .
Reserves, billions of barrels .
40
0
2005
Data from the 2006 BP Statistical Review
269Gb rise in reserves, no adjustment for 65Gb produced since 1986
14
Reserves, billions of barrels .
Saudi Reserves
Saudi control
264Gb reserves
200
Nehring RAND study
176Gb reserves
100
0
1975
•
•
1980
1985
1990
1995
2000
2005
Data from the 2006 BP Statistical Review
95Gb rise in reserves, no adjustment for 53Gb of production since 1988
15
Estimating Remaining
Production from a Graph
•
In plots of annual production vs cumulative production
– We can estimate the remaining production from a trend line
– Advantage is that we can identify points on the trend line
– Disadvantage is that we cannot make an estimate until the
production drops
•
Alternative is to plot the growth rate of the cumulative production
(annual production over cumulative production) instead of the
annual production
– First applied to Daphnia populations in biology in 1963
– King Hubbert introduced this approach for estimating remaining oil
production in 1982
– Advantage is that we can make an estimate before the peak
– Disadvantage is that we need to know the cumulative production
16
Growth-Rate Plot for US Crude Oil
Growth Rate for Cumulative .
10%
Trend line is for normal fit
(225 billion barrels)
5%
0%
0
100
200
Cumulative Production, billions of barrels
•
EIA data (cumulative from 1859, open symbols 1900-1930, closed symbols 1931-2006)
17
Growth Rate for Cumulative.
How Much Oil do the Saudis Have?
10%
Trend line is for 1978 RAND
study (90Gb remaining)
Official Saudi reserves are
264 billion barrels
5%
0%
0
50
100
150
200
Cumulative Production, billions of barrels
•
•
EIA data (open 1975-1990, closed 1991-2006), 1975 cumulative from Richard Nehring
Matt Simmons was the first to call attention to this anomalous situation in his book,
Twilight in the Desert
18
Growth Rate for Cumulative .
Growth-Rate Plot for World Hydrocarbons
6%
Trend line for
3Tboe remaining
4%
2%
0%
0
1
2
3
Cumulative Production, trillion barrels of oil equivalent
•
•
•
Oil + natural gas + natural gas liquids like propane and butane
Data 1965, 1972, 1981, 2006 BP Statistical Review (open 1960-1982, closed 1983-2005)
The German resources agency BGR gives hydrocarbon reserves as 2.7Tboe
–
–
Expectation of future discoveries and future OPEC oil reserve reductions
Includes 500Gboe for non-conventional sources like Canadian oil sands
19
Cumulative Production,Tboe.
World Hydrocarbon Production
4
3
2
0
1960
•
•
3Tboe remaining
1
1980
2000
2020
2040
2060
2080
2100
Cumulative normal (ultimate 4.6Tboe, lms fit for mean 2018, sd 35 years)
IPCC scenarios assume that 11 to 15Tboe is available
20
Fort McMurray, Alberta
Oil Sands
21
Canadian Oil Sands
• 1.0 Mb per day in 2005, increasing 8% per year
• 35Gb reserves for mining (comparable to one year of
world oil production)
• 140Gb reserves for wells
– Production with a steam process
– Production and upgrading to synthetic crude oil use 25% of the oil
energy equivalent in natural gas
– Canadian gas reserves are 10Gboe (end of 2005)
– Annual gas production is 12% of reserves per year
– Challenges in meeting obligations under the Kyoto agreement
• The Uppsala Hydrocarbon Depletion Group were the first
to call attention to these limitations
22
Outline
• The 4th UN IPCC Assessment Report
• Hubbert’s peak
–
–
–
–
The history of US oil production
How much oil do the Saudis have?
The future of world hydrocarbons
The Canadian oil sands
• The coal question
–
–
–
–
British coal, a nearly complete history
Chinese coal
American coal
The future of world coal, by regions
• Climate change
– Simulations of future temperature and sea level
– Carbon capture
– Wind and sun
• Concluding thoughts
23
British Coal
24
British Coal Production
Annual Production, Mt .
300
200
100
0
1850
•
•
1900
1950
2000
Data from the US National Bureau of Economic Research (1854-1876),
the Durham Coal Mining Museum (1877-1956), and the British
Department of Trade and Industry (1957-2006)
In the peak production year, 1913, there were 3,024 mines
25
Growth Rate for Cumulative .
Growth-Rate Plot for British Coal
4%
2%
0%
0
5
10
15
20
25
Cumulative Production, Gt
•
•
1854-2006, 1853 cumulative from William Jevons, The Coal Question
Already near the trend line in 1854
26
Growth Rate for Cumulative .
Remaining Production for British Coal
0.2%
10% per year
Trend line for
200Mt remaining
0.1%
0.0%
26.2
26.4
26.6
Cumulative Production, Gt
•
•
•
Data from the UK Department of Trade and Industry (1993-2006)
6 producing underground mines  several with less than ten years of coal
35 strip mines are producing, but there are difficulties in getting permits for new mines
27
Cumulative Production, Gt.
Cumulative British Coal Production
Pre-war fit
20
Post-war fit
10
0
1850
•
•
1900
1950
2000
Pre-war lms fit (1854-1945, ultimate 25.6Gt, mean 1920, sd 41 years)
Post-war lms fit (1946-2006, ultimate 27.2Gt, mean 1927, sd 39 years)
28
Reserves-to-Production Ratio for UK Coal
R/P ratio, years
900
600
300
0
0
50
100
Years since Edward Hull's
Reserve Survey in 1864
•
•
•
1864 reserves from Edward Hull of the Geological Survey
Other data from the World Energy Council Surveys
Current R/P ratio is 7 years
29
Reserves vs Remaining Production
1000
Resources + Reserves
Hull
100
Gt .
Reserves
10
Remaining
Production
1
0
1850
•
•
•
1900
1950
2000
1864 reserves from Edward Hull of the Geological Survey
Other data from the World Energy Council Surveys of Energy Resources
Resources include seams of 2ft or more at depths of 4000ft or less
30
% of Reserves Eventually Produced .
Fraction of Reserves Eventually Produced
•
•
•
40%
Hull
Hull
20%
0%
1850
1900
1950
2000
1864 reserves from Edward Hull of the Geological Survey
Other data from the World Energy Council Surveys of Energy Resources
Will use trends if they exist, reserves otherwise
31
Why Are Coal Reserves Too High?
•
•
•
It seems likely that
there are many
social, environmental,
and technical
hindrances that are
not fully taken into
account in the
reserve estimates
The German Energy
Watch Group was
early in pointing out
that there is a
problem with
reserves worldwide
Here are some
technical restrictions
from the USGS 2000
National Coal
Assessment for the
Illinois basin
32
Production and Reserves
China
USA
India
Australia
Russia
South Africa
World
•
•
Production, Gt
2.38
1.05
Reserves, Gt
189
247
0.45
0.37
0.31
0.26
92
79
157
29
6.20
963
2005 Production numbers from the BP 2006 Statistical Review
Reserves from the World Energy Council surveys of resources (2006/2007
South Africa Yearbook for South Africa, and the Chinese Ministry of Land
and Resources 2001 by way of Sandro Schmidt at the BGR)
33
Chinese
Coal
34
Growth-Rate Plot for China
Growth Rate for Cumulative.
15%
10%
Trend line for 70Gt remaining
Reserves are 189Gt
5%
0%
0
10
20
30
40
50
Cumulative Production, Gt
•
•
Data from Tim Wright, D.W. Dwyer, and BP 2006 Statistical Review (cumulative from
1896, open symbols 1918-1961, closed symbols 1962-2005), corrections by Jianjun Tu
Reserves from the Chinese Ministry of Land and Resources 2001 by way of Sandro
35
Schmidt at the BGR
Cumulative Production for China
Cumulative Production, Gt.
100
50
0
1950
•
2000
2050
2100
Cumulative normal (ultimate 111Gt, lms fit for mean 2015 and sd 27 years)
36
American Coal
37
US Coal Production
Annual Production, Mt.
1,000
Total
500
West of the
Mississippi
0
1850
•
•
1900
1950
2000
Data from the USGS (Robert Milici)
Will consider the East and the West separately
38
Anthracite in Pennsylvania
Annual Production, Mt.
80
60
40
20
0
1850
•
•
1900
1950
Data from the USGS (Robert Milici)
Anthracite is a grade of coal used for home heating that burns with little smoke
39
Growth-Rate Plot for PA Anthracite
Growth Rate for Cumulative
6%
4%
2%
0%
0
1
2
3
4
5
Cumulative Production, Gt
•
•
Data from the USGS (Robert Milici) cumulative from 1800, symbols 1875-1995
16% of the 1913 reserves have been produced
40
Cumulative PA Anthracite Production
Cumulative Production, Gt.
5
4
3
2
1
0
1850
•
1900
1950
2000
Normal lms fit for ultimate 5.00Gt, mean 1916, and sd 27 years
41
Bituminous Coal in Virginia
Annual Production, Mt.
40
20
0
1900
•
•
1950
2000
Data from the USGS (Robert Milici) and the EIA
Virginia has coal with high energy content, and much of it is used for metallurgy
42
Growth-Rate Plot for VA Bituminous
Growth Rate for Cumulative.
10%
8%
Pre-war Trend
6%
WWII
Trend is for 800Mt remaining
Reserves are 2.8Gt
4%
2%
0%
0
1
2
3
Cumulative Production, Gt
•
•
Data from the USGS (Robert Milici) cumulative from 1800, closed 1900-1940,
open 1941-1945, closed 1946-2006, reserves from the EIA
Trend is for 16% of the 1924 reserves to eventually be produced
43
Cumulative VA Bituminous Production
Cumulative Production, Gt.
3
Post-war fit
2
1
Pre-war fit
0
1900
•
•
1950
2000
2050
Pre-war normal (ultimate 0.40Gt, lms fit for mean 1926 and sd 16 years)
Post-war normal (ultimate 3.03Gt, lms fit for mean 1984 and sd 34 years)
44
Coal East of the Mississippi
Growth Rate for Cumulative .
8%
6%
Pre-war Trend
4%
WWII
Trend is for 40Gt remaining
Reserves are 96Gt
2%
0%
0
20
40
60
Cumulative Production, Gt
•
•
Does not include Pennsylvania anthracite
Data from the USGS (Robert Milici) cumulative from 1800, closed 19001940, open 1941-1948, closed 1949-2005, reserves from the EIA
45
Cumulative Production for the East
Cumulative Production, Gt.
Post-war fit
40
20
Pre-war fit
0
1850
•
•
•
1900
1950
2000
Does not include Pennsylvania anthracite
Pre-war normal (ultimate 20Gt, lms fit for mean 1924 and sd 20 years)
Post-war normal (ultimate 86Gt, lms fit for mean 1999 and sd 67 years)
46
Western Coal
47
Coal West of the Mississippi
Growth Rate for Cumulative.
10%
5%
Trend is for 25Gt remaining
Reserves are 79Gt without Montana
Pre-70’s trend
0%
0
5
10
15
Cumulative Production, Gt
•
•
•
Data from the USGS (Robert Milici) closed 1800-1970, open 1971-1978, closed 1979-2005
Reserves from the EIA
48
Montana is the state with the largest reserves, 68Gt, but annual production is only 36Mt
Cumulative Production for the West
15
Cumulative Production, Gt.
Post-70’s fit
10
5
Pre-70’s fit
0
1900
•
•
1950
2000
Pre-70’s normal (ultimate 1.6Gt, lms fit for mean 1929 and sd 23 years)
Post-70’s normal (ultimate 38Gt, lms fit for mean 2016 and sd 25 years)
49
Growth Rate for Cumulative .
Growth-Rate Plot for Australia and New Zealand
6%
Trend line for 50Gt remaining
Reserves are 79Gt
5%
4%
3%
3
10
Cumulative Production, Gt
•
•
•
Data (1981-2005) from the 2006 BP Statistical Review
1990 Australia cumulative from the History of Coal Mining in Australia, A.J. Hargraves
Reserves from the 2004 World Energy Council survey
50
Growth Rate for Cumulative.
Growth-Rate Plot for Europe
2%
1%
Trend line for 23Gt remaining
Reserves are 55Gt
0%
50
75
100
Cumulative Production, Gt
•
•
•
Data (1981-2005) from the 2006 BP Statistical Review
2005 cumulative from the 2005 BGR Energy Resources Report
Reserves from the 2004 World Energy Council survey, down from
171Gt in 1990
51
Growth-Rate Plot for Africa
Growth Rate for Cumulative..
8%
6%
4%
Trend line for 10Gt remaining
Reserves are 30Gt
2%
0%
0
5
10
Cumulative Production, Gt
•
•
•
Data (open 1981-1990, closed 1991-2005) from the 2006 BP Statistical Review
2005 cumulative from the 2005 BGR Energy Resources Report
South African reserves were recently reduced by 20Gt (2006/2007 South Africa
Yearbook)
52
Growth Rate for Cumulative. .
Former Soviet Union
4%
Trend line for 18Gt remaining
1996 reserves are 157Gt
2%
0%
15
25
35
Cumulative Production, Gt
•
•
•
•
Data from BP (closed 1981-1988, open 1989-2005)
2005 cumulative from the 2005 BGR Energy Resources Report
Drop that started in 1989 is from the collapse of the Soviet Union
Reserves from World Energy Council surveys, unchanged since the
collapse of the Soviet Union
53
Growth-Rate Plot for South Asia
Growth Rate for Cumulative.
10%
Exponential Growth
Reserves are 111Gt
5%
0%
0
5
10
15
Cumulative Production, Gt
•
•
•
Data (1965-2005) from the 2006 BP Statistical Review
Earlier production from World Energy Council Surveys
Reserves from the 2004 World Energy Council survey
54
Growth-Rate Plot for Central and South America
Growth Rate for Cumulative.
10%
5%
Exponential Growth
Reserves are 20Gt
0%
0.0
0.5
1.0
1.5
Cumulative Production, Gt
•
•
•
Data (1981-2005) from the 2006 BP Statistical Review
2005 Cumulative from the BGR Resources Report
Reserves from the 2004 World Energy Council survey
55
Reserves vs Trends for Remaining Production
Region
Reserves Gt
Trends Gt
North America
255
135
East Asia
190
70
Australia and New Zealand
79
50
Europe
55
23
Africa
30
10
223
18
Former Soviet Union
•
•
South Asia
111
Central and South America
20
World (at 3.6boe/t)
963 (3.5Tboe) 437 (1.6Tboe)
North America includes trends for the East (40Gt), the West (25Gt), reserves for
Montana (68Gt), and trends for Canada and Mexico (2Gt)
IPCC scenarios assume 18Tboe is available for production
56
Cumulative Production, Tboe.
Future Fossil-Fuels Production
4
3
2
1
0
1960
•
•
•
•
3.0Tboe
hydrocarbons
remaining
1.6Tboe coal
remaining
1980
2000
2020
2040
2060
2080
2100
Hydrocarbons cumulative normal (ultimate 4.6Tboe, lms fit for mean 2018, sd 35 years)
2005 coal cumulative from the 2005 BGR Energy Resources Report (USGS for US)
Coal cumulative normal (ultimate 2.6Tboe, lms fit for mean 2024, sd 48 years)
The standard deviations of 35 and 48 years can be compared to time constants for
57
temperature and sea level
Outline
• The 4th UN IPCC Assessment Report
• Hubbert’s peak
–
–
–
–
The history of US oil production
How much oil do the Saudis have?
The future of world hydrocarbons
The Canadian oil sands
• The coal question
–
–
–
–
British coal, a nearly complete history
Chinese coal
American coal
The future of world coal, by regions
• Climate change
– Simulations of future temperature and sea level
– Carbon capture
– Wind and sun
• Concluding thoughts
58
Fossil-Fuel Carbon Emissions
Cumulative Carbon Emissions, Gt.
800
600
•
Super-Kyoto
Profile
400
520Gt
remaining
200
0
1960
•
•
Producer-Limited
Profile
1980
2000
2020
2040
2060
2080
2100
Total fossil-fuel carbon is an input for climate-change models
Carbon coefficients from the EIA: oil (110kg/boe), gas (79kg/boe), coal (141kg/boe),
and future hydrocarbons weighted by BGR reserves (98kg/boe)
The Super-Kyoto Profile is a 50% stretch-out in time with the same ultimate production
59
Cumulative Future Fossil-Fuel Carbon Emissions, Gt.
Comparing with the IPCC Scenarios
•
•
2,000
1,000
Producer-Limited Profile
0
2000
2050
2100
Our Producer-Limited profile has lower emissions than any of the 40 IPCC scenarios
60
Jean Laherrere was the first to point out this anomalous situation
Simulated CO2 Levels
Fossil-Fuel Carbon, Gt
430
380
5
Producer Limited Carbon
Super Kyoto Carbon
Producer Limited CO2
330
Super Kyoto CO2
0
2000
2100
2200
2300
Carbon-Dioxide Concentration, ppm.
10
280
2400
Year
•
•
•
Predictions using the program MAGICC from Tom Wigley at the National Center
for Atmospheric Research in Boulder with a modified WRE profile
The Producer-Limited Profile gives a peak CO2 concentration of 460ppm in 2070
The Super-Kyoto Profile gives a 440ppm peak
61
Temperature Rises Associated
with Future Fossil-Fuel Use
Associated Temperature Rise, °C.
0.8
0.4
0.0
2000
2100
2200
2300
2400
Year
•
•
•
•
•
Predictions from Tom Wigley’s MAGICC (no mechanical ice model)
The temperature rise is a maximum of 0.8C in 2100
The Super-Kyoto Profile (dashed lines) reduces the maxima by 0.04C
Time constant is of the order of a thousand years (an integrator)
Sensitivity to errors is 0.0012C/Gt carbon
62
CO2 Capture and Storage
for Coal Power Plants
• MIT has just completed an outstanding study, The
Future of Coal, that gives a cost of $150/t of
carbon avoided
• To reduce the temperature in 2100 by 0.001C, the
cost would be 100 billion dollars
• Additional cost for transportation and burial
– A distribution system is needed that is comparable to our
present natural gas pipeline system
– Cannot have leaks on the time scale of a thousand years
63
Wind and Sun
•
•
The time constants of around 50 years for fossil-fuel exhaustion imply that
a transition to renewable sources of energy is likely
Wind is the fastest growing renewable
– Current world capacity is 74GW, increasing at 25% per year
– 19% of new US capacity last year
– Advantage is a production learning curve
•
Solar photovoltaics for the home and business
– World production in 2006 was 2.2GW, up 33% from 2005
– Advantage is that there is no need for new transmission lines
– Caltech is installing a 230-kW plant on top of a parking structure
•
Concentrating solar
– Current capacity is 350MW, built in the 80s in the Mojave Desert
– New Nevada Solar One with 64MW near Las Vegas
– Advantages are that it uses the direct sunlight available in the Southwest, and
the possibility of thermal storage
– The major California utilities, Southern California Edison, San Diego Gas and
Electric, and Pacific Gas and Electric, are each planning to spend a billion
dollars on concentrating solar plants
64
Kramer
Junction,
California
65

•
•
From Schott Glass
Area in red circle in California
could supply sufficient energy
66
to replace the entire US grid
Nevada Solar One
June 2, 2007
67
Concluding Thoughts
•
Results
– Estimate for future hydrocarbon production (3Tboe) is consistent with
reserves
– Estimate for future coal production (1.6Tboe) is about half of reserves
– The time constants for fossil-fuel exhaustion are of the order of 50 years
– The time constant for temperature is of the order of 1,000 years
•
Implications
– Since estimate for future fossil-fuel production is less than all 40 UN IPCC
scenarios, producer limitations could provide useful constraints in climate
modeling
– A transition to renewable sources of energy is likely
– To lessen the effects of climate change associated with future fossil-fuel
use, reducing ultimate production is more important than slowing it down
•
Opportunities
– One-third of US fossil-fuel reserves are on federal lands, so ultimate
production could be reduced substantially by limits on new leases for
mining and drilling
– The US has an outstanding resource in its direct sunlight
68
Thanks for Advice, Criticism,
Discussion, and Slides
•
•
•
•
•
•
•
Tom Wigley and Steve Smith at the National Center for
Atmospheric Research in Boulder
Bill Bridges, Dave Goodstein, Melany Hunt, John Ledyard, Ken
Pickar, Tapio Schneider, John Seinfeld, and Tom Tombrello at
Caltech
Dimitri Antsos at the Jet Propulsion Laboratory
John Rutledge at Freese and Nichols, Inc. in Fort Worth
Charlie Kennel at the University of California at San Diego
Sandro Schmidt at the BGR
Juha Karhu at the University of Helsinki
Special thanks to Sandy Garstang in the Caltech Library and Dale Yee in the
Caltech Engineering Division for their ingenuity in locating mining records
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