Reduced interdecadal variability of Atlantic Meridional Overturning Circulation under global warming

Cheng, Jun; Liu, Zhengyu; Zhang, Shaoqing; Liu, Wei; Liu, Dong; Liu, Peng; Liu, Hongli

doi:10.1073/pnas.1519827113

Cited by 43 publications

(45 citation statements)

References 49 publications

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“…CMIP5 projections suggest that under global warming, the internal variability of the AMOC will decrease (Cheng et al, ). The CMIP5 projections were completed by comparing the period 2100–2300 in each future forcing scenario to the preindustrial control.…”

Section: The Power Of Mpi‐gementioning

confidence: 99%

The Max Planck Institute Grand Ensemble: Enabling the Exploration of Climate System Variability

Maher

Milinski

Suárez-Gutiérrez

et al. 2019

J Adv Model Earth Syst

379

390

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The Max Planck Institute Grand Ensemble (MPI-GE) is the largest ensemble of a single comprehensive climate model currently available, with 100 members for the historical simulations and four forcing scenarios. It is currently the only large ensemble available that includes scenario representative concentration pathway (RCP) 2.6 and a 1% CO 2 scenario. These advantages make MPI-GE a powerful tool. We present an overview of MPI-GE, its components, and detail the experiments completed. We demonstrate how to separate the forced response from internal variability in a large ensemble. This separation allows the quantification of both the forced signal under climate change and the internal variability to unprecedented precision. We then demonstrate multiple ways to evaluate MPI-GE and put observations in the context of a large ensemble, including a novel approach for comparing model internal variability with estimated observed variability. Finally, we present four novel analyses, which can only be completed using a large ensemble. First, we address whether temperature and precipitation have a pathway dependence using the forcing scenarios. Second, the forced signal of the highly noisy atmospheric circulation is computed, and different drivers are identified to be important for the North Pacific and North Atlantic regions. Third, we use the ensemble dimension to investigate the time dependency of Atlantic Meridional Overturning Circulation variability changes under global warming. Last, sea level pressure is used as an example to demonstrate how MPI-GE can be utilized to estimate the ensemble size needed for a given scientific problem and provide insights for future ensemble projects.Large-ensemble projects of comprehensive coupled climate models are gaining traction as methods to robustly estimate internal variability in transient simulations and to quantify the forced signal (e.g., Kay

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Section: The Power Of Mpi‐gementioning

confidence: 99%

The Max Planck Institute Grand Ensemble: Enabling the Exploration of Climate System Variability

Maher

Milinski

Suárez-Gutiérrez

et al. 2019

J Adv Model Earth Syst

379

390

View full text Add to dashboard Cite

show abstract

“…7, recent satellite and in situ observations, coupled with tide gauge data, suggest an oscillatory behavior of the AMOC over the last 150 y more than an accelerating reduction of strength with oscillations becoming more and more frequent as claimed in ref. 1.…”

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confidence: 99%

Atlantic Meridional Overturning Circulation is stable under global warming

Parker

2016

Proc. Natl. Acad. Sci. U.S.A.

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Many new studies have been published supporting the hypothesis that the Atlantic Meridional Overturning Circulation (AMOC) is experiencing a slowdown. These studies are based on proxies, climate model predictions, or a combination of both. The latest work (1) is only based on predictions. The AMOC is allegedly slowing down at an increased rate because of the Arctic ice melting as predicted by climate models. Recent satellite information for the Arctic shows a shrinking sea ice and warming temperatures since 1978. Scattered prior information dating back to the mid-1800s shows the shrinking of Arctic sea ice possibly started in the mid-1800s with superimposed strong interannual and multidecadal oscillations, consistent with the Arctic temperature pattern (2-4). The recent shrinking of sea ice and warming for the Arctic should therefore be separated from the long-term shrinking and warming and the natural multidecadal oscillations.Natural variability is globally well known (5, 6), and it should not be a novelty to have this variability also in the Arctic, as in the many interconnected climate patterns of atmosphere and oceans, and the AMOC. As better explained in ref. 7, recent satellite and in situ observations, coupled with tide gauge data, suggest an oscillatory behavior of the AMOC over the last 150 y more than an accelerating reduction of strength with oscillations becoming more and more frequent as claimed in ref. 1.Direct estimations of the AMOC demonstrate no critical slowdown over the past two decades (7-10). The three time series of Fig. 1 are the AMOC S-A (satellite sea surface height plus ARGO), based on satellite sea surface height and ARGO temperature, salinity, and velocity from profiling buoys; the AMOC SSH (satellite sea surface height only) only, based on satellite sea surface height; and the AMOC MSL (tide gauge mean sea level), based on the detrended time series of mean sea level measured by tide gauges of The Battery (New York, NY) and Brest. Data from 1856 to present show that the AMOC MSL has marginally reduced. However, since 1910 in the same dataset, the AMOC MSL has marginally increased. Since 1993, the AMOC SSH has increased. Since 2002, the AMOC S-A, the AMOC MSL, and the AMOC SSH have reduced. Significant variability is affecting the AMOC. As there is no sign of increasing weakening of the AMOC during the last few decades, but only overall stability with substantial seasonal, interannual, and multidecadal variability, the climate model predictions in ref. 1 appear unrealistic.As direct measurements are available for the strength of the AMOC as well as the many other climate parameters describing states of the atmosphere or the oceans, often strongly interconnected, climate models should be built through validation vs. those measurements and include all of the relevant natural forcings in addition to the anthropogenic carbon dioxide emission. Not accounting for natural variability and neglecting validation vs. direct measurements, the climate models fail to represent the recent past clim...

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“…We believe his comment does not disprove our results. As pointed out in our study (1), the response of AMOC-IV to warming is only significant under intense warming scenarios, such as Representative Concentration Pathway (RCP) 60/85. In the weak warming scenarios of RCP26/45, even for the period of full warming in, say, the 22nd and 23rd centuries, there is no robust cross-model response of AMOC-IV.…”

mentioning

confidence: 59%

“…Actually, reliable observations of AMOC are limited for the validation of the simulation ability of AMOC in coupled climate models, especially for its long-term variability (10). In fact, the simulated AMOC-IVs in the five models used in our study (1) are different in their dominant timescales and magnitudes, due to the different model details. However, their responses to global warming are almost consistent, especially for strong warming scenarios.…”

mentioning

confidence: 96%

Reply to Parker: Robust response of AMOC interdecadal variability to future intense warming

Cheng

Liu

Zhang

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Reduced interdecadal variability of Atlantic Meridional Overturning Circulation under global warming

Cited by 43 publications

References 49 publications

The Max Planck Institute Grand Ensemble: Enabling the Exploration of Climate System Variability

The Max Planck Institute Grand Ensemble: Enabling the Exploration of Climate System Variability

Atlantic Meridional Overturning Circulation is stable under global warming

Reply to Parker: Robust response of AMOC interdecadal variability to future intense warming

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