The challenge of simulating the warmth of the mid-Miocene climatic optimum in CESM1
The mid-Miocene climatic optimum (MMCO) is an intriguing climatic period due to its above-modern temperatures in mid-to-high latitudes in the presence of close-to-modern CO<sub>2</sub> concentrations. We use the recently released Community Earth System Model (CESM1.0) with a slab ocean t...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-03-01
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| Series: | Climate of the Past |
| Online Access: | http://www.clim-past.net/10/523/2014/cp-10-523-2014.pdf |
| _version_ | 1818545509339496448 |
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| author | A. Goldner N. Herold M. Huber |
| author_facet | A. Goldner N. Herold M. Huber |
| author_sort | A. Goldner |
| collection | DOAJ |
| description | The mid-Miocene climatic optimum (MMCO) is an intriguing climatic period due
to its above-modern temperatures in mid-to-high latitudes in the presence of
close-to-modern CO<sub>2</sub> concentrations. We use the recently released Community
Earth System Model (CESM1.0) with a slab ocean to simulate this warm period,
incorporating recent Miocene CO<sub>2</sub> reconstructions of 400 ppm (parts per million). We simulate a
global mean annual temperature (MAT) of 18 °C, ~4 °C
above the preindustrial value, but 4 °C colder than the global
Miocene MAT we calculate from climate proxies. Sensitivity tests reveal that
the inclusion of a reduced Antarctic ice sheet, an equatorial Pacific temperature gradient
characteristic of a permanent El Niño, increased CO<sub>2</sub> to 560 ppm, and variations in
obliquity only marginally improve model–data agreement. All MMCO simulations
have an Equator to pole temperature gradient that is at least
~10 °C larger than that reconstructed from proxies. The MMCO
simulation most comparable to the proxy records requires a CO<sub>2</sub>
concentration of 800 ppm. Our results illustrate that MMCO warmth is not
reproducible using the CESM1.0 forced with CO<sub>2</sub> concentrations
reconstructed for the Miocene or including various proposed Earth system
feedbacks; the remaining discrepancy in the MAT is comparable to that
introduced by a CO<sub>2</sub> doubling. The model's tendency to underestimate proxy
derived global MAT and overestimate the Equator to pole temperature gradient
suggests a major climate problem in the MMCO akin to those in the Eocene. Our
results imply that this latest model, as with previous generations of climate
models, is either not sensitive enough or additional forcings remain missing
that explain half of the anomalous warmth and pronounced polar amplification
of the MMCO. |
| first_indexed | 2024-12-12T07:41:06Z |
| format | Article |
| id | doaj.art-293f8dd82dbc43e3ac98ec9b9c329560 |
| institution | Directory Open Access Journal |
| issn | 1814-9324 1814-9332 |
| language | English |
| last_indexed | 2024-12-12T07:41:06Z |
| publishDate | 2014-03-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Climate of the Past |
| spelling | doaj.art-293f8dd82dbc43e3ac98ec9b9c3295602022-12-22T00:32:47ZengCopernicus PublicationsClimate of the Past1814-93241814-93322014-03-0110252353610.5194/cp-10-523-2014The challenge of simulating the warmth of the mid-Miocene climatic optimum in CESM1A. Goldner0N. Herold1M. Huber2Earth, Atmospheric, and Planetary Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907, USAEarth Systems Research Center, Institute for Earth, Ocean and Space Sciences, University of New Hampshire, Durham, NH 03824, USADepartment of Earth Sciences, The University of New Hampshire, Durham, NH 03824, USAThe mid-Miocene climatic optimum (MMCO) is an intriguing climatic period due to its above-modern temperatures in mid-to-high latitudes in the presence of close-to-modern CO<sub>2</sub> concentrations. We use the recently released Community Earth System Model (CESM1.0) with a slab ocean to simulate this warm period, incorporating recent Miocene CO<sub>2</sub> reconstructions of 400 ppm (parts per million). We simulate a global mean annual temperature (MAT) of 18 °C, ~4 °C above the preindustrial value, but 4 °C colder than the global Miocene MAT we calculate from climate proxies. Sensitivity tests reveal that the inclusion of a reduced Antarctic ice sheet, an equatorial Pacific temperature gradient characteristic of a permanent El Niño, increased CO<sub>2</sub> to 560 ppm, and variations in obliquity only marginally improve model–data agreement. All MMCO simulations have an Equator to pole temperature gradient that is at least ~10 °C larger than that reconstructed from proxies. The MMCO simulation most comparable to the proxy records requires a CO<sub>2</sub> concentration of 800 ppm. Our results illustrate that MMCO warmth is not reproducible using the CESM1.0 forced with CO<sub>2</sub> concentrations reconstructed for the Miocene or including various proposed Earth system feedbacks; the remaining discrepancy in the MAT is comparable to that introduced by a CO<sub>2</sub> doubling. The model's tendency to underestimate proxy derived global MAT and overestimate the Equator to pole temperature gradient suggests a major climate problem in the MMCO akin to those in the Eocene. Our results imply that this latest model, as with previous generations of climate models, is either not sensitive enough or additional forcings remain missing that explain half of the anomalous warmth and pronounced polar amplification of the MMCO.http://www.clim-past.net/10/523/2014/cp-10-523-2014.pdf |
| spellingShingle | A. Goldner N. Herold M. Huber The challenge of simulating the warmth of the mid-Miocene climatic optimum in CESM1 Climate of the Past |
| title | The challenge of simulating the warmth of the mid-Miocene climatic optimum in CESM1 |
| title_full | The challenge of simulating the warmth of the mid-Miocene climatic optimum in CESM1 |
| title_fullStr | The challenge of simulating the warmth of the mid-Miocene climatic optimum in CESM1 |
| title_full_unstemmed | The challenge of simulating the warmth of the mid-Miocene climatic optimum in CESM1 |
| title_short | The challenge of simulating the warmth of the mid-Miocene climatic optimum in CESM1 |
| title_sort | challenge of simulating the warmth of the mid miocene climatic optimum in cesm1 |
| url | http://www.clim-past.net/10/523/2014/cp-10-523-2014.pdf |
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