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The Earth's climate evolves because of both internal variability and external forcings. Using Coupled Model Intercomparison Project Phase 5 (CMIP5) models, here we quantify the ratio of externally forced variance to total variance on interannual and longer time scales for regional surface air temperature (SAT) and sea level, which depends on the relative strength of externally forced signal compared to internal variability. The highest ratios are found in tropical areas for SAT but at high latitudes for sea level over the historical period when ocean dynamics and global mean thermosteric contributions are considered. Averaged globally, the ratios over a fixed time interval (e.g., 30 years) are projected to increase during the 21st century under the business-as-usual scenario (RCP8.5). In contrast, under two mitigation scenarios (RCP2.6 and RCP4.5), the ratio declines sharply by the end of the 21st century for SAT, but only declines slightly or stabilizes for sea level, indicating a slower response of sea level to climate mitigation.

Item Type:	Refereed Article
Keywords:	climate model, external forcing, internal variability, sea level, surface air temperature
Research Division:	Earth Sciences
Research Group:	Climate change science
Research Field:	Climate change processes
Objective Division:	Environmental Policy, Climate Change and Natural Hazards
Objective Group:	Understanding climate change
Objective Field:	Climate change models
UTAS Author:	Zhang, X (Dr Xuebin Zhang)
ID Code:	118715
Year Published:	2015
Web of Science® Times Cited:	16
Deposited By:	Zoology
Deposited On:	2017-07-18
Last Modified:	2017-08-29
Downloads:	118 View Download Statistics