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Decadal prediction skill in a multi-model ensemble
- Source :
- Climate Dynamics, Climate Dynamics 38 (2012) 7-8, Climate Dynamics, 38(7-8), 1263-1280
- Publication Year :
- 2012
-
Abstract
- Decadal climate predictions may have skill due to predictable components in boundary conditions (mainly greenhouse gas concentrations but also tropospheric and stratospheric aerosol distributions) and initial conditions (mainly the ocean state). We investigate the skill of temperature and precipitation hindcasts from a multi-model ensemble of four climate forecast systems based on coupled ocean-atmosphere models. Regional variations in skill with and without trend are compared with similarly analysed uninitialised experiments to separate the trend due to monotonically increasing forcings from fluctuations around the trend due to the ocean initial state and aerosol forcings. In temperature most of the skill in both multi-model ensembles comes from the externally forced trends. The rise of the global mean temperature is represented well in the initialised hindcasts, but variations around the trend show little skill beyond the first year due to the absence of volcanic aerosols in the hindcasts and the unpredictability of ENSO. The models have non-trivial skill in hindcasts of North Atlantic sea surface temperature beyond the trend. This skill is highest in the northern North Atlantic in initialised experiments and in the subtropical North Atlantic in uninitialised simulations. A similar result is found in the Pacific Ocean, although the signal is less clear. The uninitialised simulations have good skill beyond the trend in the western North Pacific. The initialised experiments show some skill in the decadal ENSO region in the eastern Pacific, in agreement with previous studies. However, the results in this study are not statistically significant (p ˜ 0.1) by themselves. The initialised models also show some skill in forecasting 4-year mean Sahel rainfall at lead times of 1 and 5 years, in agreement with the observed teleconnection from the Atlantic Ocean. Again, the skill is not statistically significant (p ˜ 0.2). Furthermore, uninitialised simulations that include volcanic aerosols have similar skill. It is therefore still an open question whether initialisation improves predictions of Sahel rainfall. We conclude that the main source of skill in forecasting temperature is the trend forced by rising greenhouse gas concentrations. The ocean initial state contributes to skill in some regions, but variations in boundary forcings such as aerosols are as important in decadal forecasting.
- Subjects :
- Meteorologie en Luchtkwaliteit
Atmospheric Science
010504 meteorology & atmospheric sciences
Meteorology and Air Quality
time-scales
Forecast skill
Climate change
010502 geochemistry & geophysics
Atmospheric sciences
01 natural sciences
predictability
Atlantic multidecadal oscillation
pacific
el-nino
north-atlantic
Predictability
0105 earth and related environmental sciences
WIMEK
precipitation trends
variability
coupled climate models
Forecast verification
ocean
Sea surface temperature
surface-temperature
13. Climate action
Climatology
Environmental science
Climate model
Teleconnection
Subjects
Details
- Language :
- English
- ISSN :
- 09307575 and 12631280
- Volume :
- 38
- Issue :
- 7-8
- Database :
- OpenAIRE
- Journal :
- Climate Dynamics
- Accession number :
- edsair.doi.dedup.....0680f461f7dcb888b03b81ab22fce9f2