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Earth's energy imbalance since 1960 in observations and CMIP5 models.

Smith DM, Allan RP, Coward AC, Eade R, Hyder P, Liu C, Loeb NG, Palmer MD, Roberts CD, Scaife AA - Geophys Res Lett (2015)

Bottom Line: Observational analyses of running 5 year ocean heat content trends (H t) and net downward top of atmosphere radiation (N) are significantly correlated (r ∼ 0.6) from 1960 to 1999, but a spike in H t in the early 2000s is likely spurious since it is inconsistent with estimates of N from both satellite observations and climate model simulations.Variations in N between 1960 and 2000 were dominated by volcanic eruptions and are well simulated by the ensemble mean of coupled models from the Fifth Coupled Model Intercomparison Project (CMIP5).We find an observation-based reduction in N of - 0.31 ± 0.21 W m(-2) between 1999 and 2005 that potentially contributed to the recent warming slowdown, but the relative roles of external forcing and internal variability remain unclear.

View Article: PubMed Central - PubMed

Affiliation: Met Office Hadley Centre Exeter, UK.

ABSTRACT

: Observational analyses of running 5 year ocean heat content trends (H t) and net downward top of atmosphere radiation (N) are significantly correlated (r ∼ 0.6) from 1960 to 1999, but a spike in H t in the early 2000s is likely spurious since it is inconsistent with estimates of N from both satellite observations and climate model simulations. Variations in N between 1960 and 2000 were dominated by volcanic eruptions and are well simulated by the ensemble mean of coupled models from the Fifth Coupled Model Intercomparison Project (CMIP5). We find an observation-based reduction in N of - 0.31 ± 0.21 W m(-2) between 1999 and 2005 that potentially contributed to the recent warming slowdown, but the relative roles of external forcing and internal variability remain unclear. While present-day anomalies of N in the CMIP5 ensemble mean and observations agree, this may be due to a cancelation of errors in outgoing longwave and absorbed solar radiation.

Key points: Observed maximum in ocean heat content trend in early 2000s is likely spuriousNet incoming radiation (N) reduced by 0.31 ± 0.21 W m(-2) during the warming pausePresent-day estimates of N may contain opposing errors in radiative components.

No MeSH data available.


Related in: MedlinePlus

Components of radiative fluxes. Time series of 5 year running mean anomalies (relative to 1960 to 2011) of TOA-absorbed shortwave radiation (ASR, red), outgoing longwave radiation (OLR, green), and net radiation (N = ASR-OLR, blue) in No (dashed) and the CMIP5 models (solid, with thick line showing the ensemble mean).
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fig04: Components of radiative fluxes. Time series of 5 year running mean anomalies (relative to 1960 to 2011) of TOA-absorbed shortwave radiation (ASR, red), outgoing longwave radiation (OLR, green), and net radiation (N = ASR-OLR, blue) in No (dashed) and the CMIP5 models (solid, with thick line showing the ensemble mean).

Mentions: In general, there is good agreement between the CMIP5 ensemble mean and observation-based anomalies of N (r = 0.82 for 5 year running means) and its components, absorbed shortwave (ASR, r = 0.87) and outgoing longwave (OLR, r = 0.80) radiation (Figure4). The CMIP5 ensemble mean therefore appears to simulate a realistic magnitude of variability associated with volcanic eruptions. The largest discrepancy between models and observations occurs during the 1970s (Figure4). The mid-1970s shift in the Pacific Decadal Oscillation [Mantua et al., 1997; Power et al., 1999] may have contributed to No. However, an increase in N is also apparent in the CMIP5 ensemble mean in the late 1970s (especially in ASR; red curves in Figure4), suggesting that external forcing may have played a role. Further work is therefore needed to understand these apparent differences between models and observations.


Earth's energy imbalance since 1960 in observations and CMIP5 models.

Smith DM, Allan RP, Coward AC, Eade R, Hyder P, Liu C, Loeb NG, Palmer MD, Roberts CD, Scaife AA - Geophys Res Lett (2015)

Components of radiative fluxes. Time series of 5 year running mean anomalies (relative to 1960 to 2011) of TOA-absorbed shortwave radiation (ASR, red), outgoing longwave radiation (OLR, green), and net radiation (N = ASR-OLR, blue) in No (dashed) and the CMIP5 models (solid, with thick line showing the ensemble mean).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4459179&req=5

fig04: Components of radiative fluxes. Time series of 5 year running mean anomalies (relative to 1960 to 2011) of TOA-absorbed shortwave radiation (ASR, red), outgoing longwave radiation (OLR, green), and net radiation (N = ASR-OLR, blue) in No (dashed) and the CMIP5 models (solid, with thick line showing the ensemble mean).
Mentions: In general, there is good agreement between the CMIP5 ensemble mean and observation-based anomalies of N (r = 0.82 for 5 year running means) and its components, absorbed shortwave (ASR, r = 0.87) and outgoing longwave (OLR, r = 0.80) radiation (Figure4). The CMIP5 ensemble mean therefore appears to simulate a realistic magnitude of variability associated with volcanic eruptions. The largest discrepancy between models and observations occurs during the 1970s (Figure4). The mid-1970s shift in the Pacific Decadal Oscillation [Mantua et al., 1997; Power et al., 1999] may have contributed to No. However, an increase in N is also apparent in the CMIP5 ensemble mean in the late 1970s (especially in ASR; red curves in Figure4), suggesting that external forcing may have played a role. Further work is therefore needed to understand these apparent differences between models and observations.

Bottom Line: Observational analyses of running 5 year ocean heat content trends (H t) and net downward top of atmosphere radiation (N) are significantly correlated (r ∼ 0.6) from 1960 to 1999, but a spike in H t in the early 2000s is likely spurious since it is inconsistent with estimates of N from both satellite observations and climate model simulations.Variations in N between 1960 and 2000 were dominated by volcanic eruptions and are well simulated by the ensemble mean of coupled models from the Fifth Coupled Model Intercomparison Project (CMIP5).We find an observation-based reduction in N of - 0.31 ± 0.21 W m(-2) between 1999 and 2005 that potentially contributed to the recent warming slowdown, but the relative roles of external forcing and internal variability remain unclear.

View Article: PubMed Central - PubMed

Affiliation: Met Office Hadley Centre Exeter, UK.

ABSTRACT

: Observational analyses of running 5 year ocean heat content trends (H t) and net downward top of atmosphere radiation (N) are significantly correlated (r ∼ 0.6) from 1960 to 1999, but a spike in H t in the early 2000s is likely spurious since it is inconsistent with estimates of N from both satellite observations and climate model simulations. Variations in N between 1960 and 2000 were dominated by volcanic eruptions and are well simulated by the ensemble mean of coupled models from the Fifth Coupled Model Intercomparison Project (CMIP5). We find an observation-based reduction in N of - 0.31 ± 0.21 W m(-2) between 1999 and 2005 that potentially contributed to the recent warming slowdown, but the relative roles of external forcing and internal variability remain unclear. While present-day anomalies of N in the CMIP5 ensemble mean and observations agree, this may be due to a cancelation of errors in outgoing longwave and absorbed solar radiation.

Key points: Observed maximum in ocean heat content trend in early 2000s is likely spuriousNet incoming radiation (N) reduced by 0.31 ± 0.21 W m(-2) during the warming pausePresent-day estimates of N may contain opposing errors in radiative components.

No MeSH data available.


Related in: MedlinePlus