16 September 2017

Spatial and Temporal Agreement in Climate Model Simulations of the Interdecadal Pacific Oscillationterdecadal Pacific Oscillation

Science

Accelerated warming and hiatus periods in the long-term rise of Global Mean Surface Temperature (GMST) have, in recent decades, been associated with positive and negative phases the Interdecadal Pacific Oscillation (IPO), respectively. Critically, initialized decadal simulations rely on the skill of state-of-the-art earth system models to reliably represent these low-frequency earth system variations.  A systematic evaluation of the simulation of the IPO in the suite of Coupled Model Intercomparison Project 5 (CMIP5) models shows that the basin-wide spatial pattern of positive and negative phases of the IPO are simulated reasonably well, with spatial pattern correlation coefficients between observations and models spanning the range 0.4–0.8. Deficiencies are mainly in the extratropical Pacific. Models that better capture the spatial pattern of the IPO also tend to more realistically simulate the ratio of decadal to total variance. This is evidence that current earth system models can simulate the processes that produce the IPO, and this builds confidence in initialized decadal climate simulations that include the IPO.

Impact

Accelerated warming and hiatus periods in the long-term rise of Global Mean Surface Temperature (GMST) have, in recent decades, been associated with positive and negative phases the Interdecadal Pacific Oscillation (IPO), respectively. Critically, initialized decadal simulations rely on the skill of state-of-the-art earth system models to reliably represent these low-frequency earth system variations.  A systematic evaluation of the simulation of the IPO in the suite of Coupled Model Intercomparison Project 5 (CMIP5) models shows that the basin-wide spatial pattern of positive and negative phases of the IPO are simulated reasonably well, with spatial pattern correlation coefficients between observations and models spanning the range 0.4–0.8. Deficiencies are mainly in the extratropical Pacific. Models that better capture the spatial pattern of the IPO also tend to more realistically simulate the ratio of decadal to total variance. This is evidence that current earth system models can simulate the processes that produce the IPO, and this builds confidence in initialized decadal climate simulations that include the IPO.

Summary

Accelerated warming and hiatus periods in the long-term rise of Global Mean Surface Temperature (GMST) have, in recent decades, been associated with positive and negative phases the Interdecadal Pacific Oscillation (IPO), respectively. Critically, initialized decadal simulations rely on the skill of state-of-the-art earth system models to reliably represent these low-frequency earth system variations.  A systematic evaluation of the simulation of the IPO in the suite of Coupled Model Intercomparison Project 5 (CMIP5) models shows that the basin-wide spatial pattern of positive and negative phases of the IPO are simulated reasonably well, with spatial pattern correlation coefficients between observations and models spanning the range 0.4–0.8. Deficiencies are mainly in the extratropical Pacific. Models that better capture the spatial pattern of the IPO also tend to more realistically simulate the ratio of decadal to total variance. This is evidence that current earth system models can simulate the processes that produce the IPO, and this builds confidence in initialized decadal climate simulations that include the IPO.

Contact
Gerald Meehl
National Center for Atmospheric Research (NCAR)
Publications
Folland, C. "Spatial and Temporal Agreement in Climate Model Simulations of the Interdecadal Pacific Oscillationterdecadal Pacific Oscillation." Environmental Research Letters 12, 044011 (2017). [10.1088/1748-9326/aa5cc8].