Source Data and Analysis Script:
Why a slowdown of the AMOC does not enhance global surface warming
by Caesar, L., Rahmstorf, S. and Feulner, G.
The names in brackets are the names of the files when loaded into the Python script.
HadCRUT4.6 Global Mean Temperature Anomaly (HadCRUT4_Global_Mean.txt)
Time series of the historical forcing (historical_forcing_sum.txt)
AMOC index as definded in Caesar et al.2018 (sg_index_with_time.txt)
AMOC indices provided by Chen and Tung (2018) (AMOC_indices.xlsx)
Ocean heat content data provided by Chen and Tung (2018) (OHC.xlsx)
Ocean heat content data provided by Cheng et al. (2016) (OHC_Cheng.xlsx)
Download all data
Python Analysis script (Python version 2.7).
Fig.1: Temporal evolution of the multidecadal variability of the AMOC compared to the global mean temperature
adjusted by the historical forcing. Proxies for the AMOC are the salinity proxies EN4 and ISHII+Scripps as
used in1 and the temperature based AMOC Index as defined in6. The global mean temperature deviation
ΔT'=ΔT-1/λ ΔQ_{rad} is based on HadCRUT4.6 data4 adjusted by the historical forcing used for CMIP5.
The default value for the feedback parameter is λ=2.3±0.7 W K-1 m-2, the numbers in brackets give the range
of correlation coefficients resulting from other values for λ (see Methods). Thin lines are annual values;
thick lines are 10-year LOWESS smoothed values. The correlation coefficients r were calculated with the smoothed
time series. (To remove any correlations due to common trends the time series were linearly detrended.)
Fig.2: Relationship between ocean heat uptake rate and AMOC strength for the decade 2005-2014. Shown is the temporal evolution of the ocean heat uptake rate, derived from the ISHII and Scripps datasets with a linear increase of 0.088 ZJ/year, compared to the AMOC strength as measured by the RAPID array with a linear decrease of 0.35 Sv/year. The two time series have opposing trends over the time period for which both data exist, i.e. 2005-2014.
Fig.3: Changes in ocean heat content distribution between two recent periods of different AMOC strength (as analysed by Chen and Tung [2018]). Shown is the division of the global ocean increase in heat storage (0-2000m) between the Atlantic (30°S-65°N) and the Southern Ocean (70°S-30°S) in the periods 2000-2004 and 2005-2014. A hypothetical division for 2005-2014 for the case that the AMOC did not slow down between the two periods is shown in lighter shading. Here we added the calculated shift of 9.5 ZJ in the heat transport due to the weaker AMOC in the later period to the Atlantic Ocean heat content.
Web page created by L. Caesar