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| Titel |
On the influence of volcanic eruptions on decadal predictions |
| VerfasserIn |
Jonas Bhend, Dáithí Stone |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092750
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| Publikation (Nr.) |
 EGU/EGU2014-7109.pdf |
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| Zusammenfassung |
| Short-term climate predictions are an active topic of research. Predictability at decadal scales
arises from the climate response to predictable changes in boundary conditions (e.g.future
greenhouse gas emissions), from the adjustment to previous changes in external forcing, and
– through the initialization – from long timescale internal variability. Unpredictable future
changes in external forcing such as major volcanic eruptions or changes in solar irradiance,
on the other hand, limit predictability at decadal scales and thus may prevent decadal
predictions from being useful. Here we analyze the effect of volcanic eruptions on decadal
predictability.
To study this effect, we analyze hindcast simulations with global climate models for the
past 1000 years. We define a forecast score from the temperature variability in the forecast
period and contrast the distribution of scores with eruptions in the forecast period with those
without eruptions. Furthermore, we test the sensitivity to volcanic eruptions for different
levels of forecast skill, defined as the predicted fraction of variance in the forecast period.
Preliminary results suggest that for global mean temperature, the effect of volcanic eruptions
is a fairly homogeneous shift of the forecast scores to larger values (i.e.to more
unpredicted variability in the forecast period). Also, the effect of eruptions is stronger for
predictions with more skill. Without much predictive skill, the risk of a very bad global
average temperature prediction is 2-5 times as large when an unforeseen eruption
occurs and up to 20 times as large for skillful predictions. For smaller scale regions,
however, the signal-to-noise ratio of the volcanic response is generally lower and the
deteriorating effect of volcanic eruptions on decadal-scale predictions is reduced. |
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