scholarly journals Implication of methodological uncertainties for mid-Holocene sea surface temperature reconstructions

2014 ◽  
Vol 10 (6) ◽  
pp. 2237-2252 ◽  
Author(s):  
I. Hessler ◽  
S. P. Harrison ◽  
M. Kucera ◽  
C. Waelbroeck ◽  
M.-T. Chen ◽  
...  
Keyword(s):  
Climate Model ◽  
Time Window ◽  
Planktonic Foraminifera ◽  
Regional Scale ◽  
Time Frame ◽  
Sea Surface ◽  
Model Simulations ◽  
Climate Model Simulations ◽  
Analytical Approaches ◽  
Baseline Climate

Abstract. We present and examine a multi-sensor global compilation of mid-Holocene (MH) sea surface temperatures (SST), based on Mg/Ca and alkenone palaeothermometry and reconstructions obtained using planktonic foraminifera and organic-walled dinoflagellate cyst census counts. We assess the uncertainties originating from using different methodologies and evaluate the potential of MH SST reconstructions as a benchmark for climate-model simulations. The comparison between different analytical approaches (time frame, baseline climate) shows the choice of time window for the MH has a negligible effect on the reconstructed SST pattern, but the choice of baseline climate affects both the magnitude and spatial pattern of the reconstructed SSTs. Comparison of the SST reconstructions made using different sensors shows significant discrepancies at a regional scale, with uncertainties often exceeding the reconstructed SST anomaly. Apparent patterns in SST may largely be a reflection of the use of different sensors in different regions. Overall, the uncertainties associated with the SST reconstructions are generally larger than the MH anomalies. Thus, the SST data currently available cannot serve as a target for benchmarking model simulations. Further evaluations of potential subsurface and/or seasonal artifacts that may contribute to obscure the MH SST reconstructions are urgently needed to provide reliable benchmarks for model evaluations.

scholarly journals Implication of methodological uncertainties for Mid-Holocene sea surface temperature reconstructions

2014 ◽  
Vol 10 (2) ◽  
pp. 1747-1782 ◽  
Author(s):  
I. Hessler ◽  
S. P. Harrison ◽  
M. Kucera ◽  
C. Waelbroeck ◽  
M.-T. Chen ◽  
...  
Keyword(s):  
Climate Model ◽  
Time Window ◽  
Planktonic Foraminifera ◽  
Regional Scale ◽  
Time Frame ◽  
Sea Surface ◽  
Model Simulations ◽  
Climate Model Simulations ◽  
Analytical Approaches ◽  
Baseline Climate

Abstract. We present and examine a~multi-sensor global compilation of Mid-Holocene (MH) sea surface temperatures (SSTs), based on Mg/Ca and alkenone palaeothermometry and reconstructions obtained using planktonic foraminifera and organic-walled dinoflagellate cyst census counts. We assess the uncertainties originating from using different methodologies and evaluate the potential of MH SST reconstructions as a benchmark for climate-model simulations. The comparison between different analytical approaches (time frame, baseline climate) shows the choice of time window for the MH has a negligible effect on the reconstructed SST pattern, but the choice of baseline climate affects both the magnitude and spatial pattern of the reconstructed SSTs. Comparison of the SST reconstructions made using different sensors shows significant discrepancies at a regional scale, with uncertainties often exceeding the reconstructed SST anomaly. Apparent patterns in SST may largely be a reflection of the use of different sensors in different regions. Overall, the uncertainties associated with the SST reconstructions are generally larger than the MH anomalies. Thus, the SST data currently available cannot serve as a target for benchmarking model simulations.

Recent past and future patterns of the Etesian winds based on regional scale climate model simulations

2013 ◽  
Vol 42 (7-8) ◽  
pp. 1819-1836 ◽  
Author(s):  
Christina Anagnostopoulou ◽  
Prodromos Zanis ◽  
Eleni Katragkou ◽  
Ioannis Tegoulias ◽  
Konstantia Tolika
Keyword(s):  
Climate Model ◽  
Regional Scale ◽  
Recent Past ◽  
Model Simulations ◽  
Etesian Winds ◽  
Climate Model Simulations

Evolution of Water Vapor Concentrations and Stratospheric Age of Air in Coupled Chemistry-Climate Model Simulations

2007 ◽  
Vol 64 (3) ◽  
pp. 905-921 ◽  
Author(s):  
John Austin ◽  
John Wilson ◽  
Feng Li ◽  
Holger Vömel
Keyword(s):  
Water Vapor ◽  
Greenhouse Gas ◽  
Climate Model ◽  
Sea Surface ◽  
Time Slice ◽  
Sea Surface Temperatures ◽  
Model Simulations ◽  
Stratospheric Water Vapor ◽  
Surface Temperatures ◽  
Climate Model Simulations

Abstract Stratospheric water vapor concentrations and age of air are investigated in an ensemble of coupled chemistry-climate model simulations covering the period from 1960 to 2005. Observed greenhouse gas concentrations, halogen concentrations, aerosol amounts, and sea surface temperatures are all specified in the model as time-varying fields. The results are compared with two experiments (time-slice runs) with constant forcings for the years 1960 and 2000, in which the sea surface temperatures are set to the same climatological values, aerosol concentrations are fixed at background levels, while greenhouse gas and halogen concentrations are set to the values for the relevant years. The time-slice runs indicate an increase in stratospheric water vapor from 1960 to 2000 due primarily to methane oxidation. The age of air is found to be significantly less in the year 2000 run than the 1960 run. The transient runs from 1960 to 2005 indicate broadly similar results: an increase in water vapor and a decrease in age of air. However, the results do not change gradually. The age of air decreases significantly only after about 1975, corresponding to the period of ozone reduction. The age of air is related to tropical upwelling, which determines the transport of methane into the stratosphere. Oxidation of increased methane from enhanced tropical upwelling results in higher water vapor amounts. In the model simulations, the rate of increase of stratospheric water vapor during the period of enhanced upwelling is up to twice the long-term mean. The concentration of stratospheric water vapor also increases following volcanic eruptions during the simulations.

scholarly journals Anthropogenic forcing and response yield observed positive trend in Earth’s energy imbalance

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shiv Priyam Raghuraman ◽  
David Paynter ◽  
V. Ramaswamy
Keyword(s):  
Radiative Forcing ◽  
Climate Model ◽  
Solar Spectrum ◽  
Internal Variability ◽  
Satellite Observations ◽  
Positive Trend ◽  
Energy Imbalance ◽  
Model Simulations ◽  
Heat Uptake ◽  
Climate Model Simulations

AbstractThe observed trend in Earth’s energy imbalance (TEEI), a measure of the acceleration of heat uptake by the planet, is a fundamental indicator of perturbations to climate. Satellite observations (2001–2020) reveal a significant positive globally-averaged TEEI of 0.38 ± 0.24 Wm−2decade−1, but the contributing drivers have yet to be understood. Using climate model simulations, we show that it is exceptionally unlikely (<1% probability) that this trend can be explained by internal variability. Instead, TEEI is achieved only upon accounting for the increase in anthropogenic radiative forcing and the associated climate response. TEEI is driven by a large decrease in reflected solar radiation and a small increase in emitted infrared radiation. This is because recent changes in forcing and feedbacks are additive in the solar spectrum, while being nearly offset by each other in the infrared. We conclude that the satellite record provides clear evidence of a human-influenced climate system.

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