GEOCARB III: A Revised Model of Atmospheric CO2 over Phanerozoic Time
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               World Data Center for Paleoclimatology, Boulder
                                  and
                     NOAA Paleoclimatology Program
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NOTE: PLEASE CITE CONTRIBUTORS WHEN USING THIS DATA!!!!!

NAME OF DATA SET: GEOCARB III: A Revised Model of Atmospheric CO2 over Phanerozoic Time
LAST UPDATE: 8/2002 (Original Receipt by WDC Paleo)

CONTRIBUTOR: Robert A. Berner, Yale University

IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2002-051

SUGGESTED DATA CITATION: Berner, R.A. and Z. Kothavala, 2001.  
GEOCARB III: A Revised Model of Atmospheric CO2 over Phanerozoic Time,
IGBP PAGES/World Data Center for Paleoclimatology 
Data Contribution Series # 2002-051.
NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

ORIGINAL REFERENCE: 
Berner, R.A. and Z. Kothavala, 2001.  
GEOCARB III: A Revised Model of Atmospheric CO2 over Phanerozoic Time,
American Journal of Science, v.301, pp.182-204, February 2001.

GEOGRAPHIC REGION: Global

PERIOD OF RECORD: Phanerozoic, 570 MMYrBP-present

DESCRIPTION: 
Berner and Kothavala 2001 GEOCARB III revised model of Phanerozoic atmospheric CO2.

Calculated paleolevels of atmospheric CO2 from the GEOCARB III model, which 
models the carbon cycle on long time scales (here a 30 million year resolution). 
The long term carbon cycle is primarily geochemical, a result of the exchange of 
carbon between the atmosphere and rocks.  The third revision includes improvements 
in the modeling of factors affecting CO2 uptake by continental weathering.  


ABSTRACT:
Revision of the GEOCARB model (Berner, 1991, 1994) for paleolevels of 
atmospheric CO2, has been made with emphasis on factors affecting CO2 uptake 
by continental weathering. This includes: (1) new GCM (general circulation model)
results for the dependence of global mean surface temperature and runoff on CO2, 
for both glaciated and non-glaciated periods, coupled with new results for the
temperature response to changes in solar radiation; (2) demonstration that values for
the weathering-uplift factor fR (t) based on Sr isotopes as was done in GEOCARB II 
are in general agreement with independent values calculated from the abundance of
terrigenous sediments as a measure of global physical erosion rate over Phanerozoic
time; (3) more accurate estimates of the timing and the quantitative effects on Ca-Mg
silicate weathering of the rise of large vascular plants on the continents during the
Devonian; (4) inclusion of the effects of changes in paleogeography alone (constant
CO2 and solar radiation) on global mean land surface temperature as it affects the rate
of weathering; (5) consideration of the effects of volcanic weathering, both in
subduction zones and on the seafloor; (6) use of new data on the d 13 C values for
Phanerozoic limestones and organic matter; (7) consideration of the relative weathering
enhancement by gymnosperms versus angiosperms; (8) revision of paleo land area
based on more recent data and use of this data, along with GCM-based paleo-runoff
results, to calculate global water discharge from the continents over time.
Results show a similar overall pattern to those for GEOCARB II: very high CO2
values during the early Paleozoic, a large drop during the Devonian and Carboniferous,
high values during the early Mesozoic, and a gradual decrease from about 170 Ma
to low values during the Cenozoic. However, the new results exhibit considerably
higher CO2 values during the Mesozoic, and their downward trend with time agrees
with the independent estimates of Ekart and others (1999). Sensitivity analysis shows
that results for paleo-CO2 are especially sensitive to: the effects of CO2 fertilization
and temperature on the acceleration of plant-mediated chemical weathering; the
quantitative effects of plants on mineral dissolution rate for constant temperature and
CO2; the relative roles of angiosperms and gymnosperms in accelerating rock weathering;
and the response of paleo-temperature to the global climate model used. This
emphasizes the need for further study of the role of plants in chemical weathering and
the application of GCMs to study of paleo-CO2 and the long term carbon cycle.


DATA:

Time(Ma)  RCO2

-570    11.70362
-560    16.26684
-550    17.95147
-540    17.19382
-530    25.52706
-520    26.18222
-510    22.39725
-500    18.89189
-490    17.29675
-480    17.28357
-470    17.72622
-460    15.46943
-450    15.85446
-440    16.68599
-430    16.99756
-420    13.90174
-410    11.0387
-400    11.32285
-390    13.45455
-380    15.30221
-370    8.040017
-360    6.137963
-350    4.337569
-340    2.704967
-330    1.671433
-320    1.338068
-310    1.254083
-300    1.249976
-290    1.326288
-280    1.255351
-270    1.440589
-260    1.872322
-250    6.081883
-240    7.104142
-230    5.197366
-220    5.831312
-210    4.912341
-200    5.442125
-190    4.441496
-180    4.843969
-170    8.573481
-160    9.123775
-150    7.599305
-140    8.198544
-130    6.605868
-120    6.096954
-110    5.88872
-100    5.30103
-90     4.317839
-80     4.185097
-70     3.200051
-60     2.802144
-50     3.176976
-40     2.066398
-30     1.417627
-20     1.156633
-10     0.990113
0       0.9879701