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| Titel |
Time of emergence of trends in ocean biogeochemistry |
| VerfasserIn |
K. M. Keller, F. Joos, C. C. Raible |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 13 ; Nr. 11, no. 13 (2014-07-09), S.3647-3659 |
| Datensatznummer |
250117508
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| Publikation (Nr.) |
 copernicus.org/bg-11-3647-2014.pdf |
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| Zusammenfassung |
| For the detection of climate change, not only the magnitude of a trend signal
is of significance. An essential issue is the time period required by the
trend to be detectable in the first place. An illustrative measure for this
is time of emergence (ToE), that is, the point in time when a signal finally
emerges from the background noise of natural variability. We investigate the
ToE of trend signals in different biogeochemical and physical surface
variables utilizing a multi-model ensemble comprising simulations of 17 Earth
system models (ESMs). We find that signals in ocean biogeochemical variables
emerge on much shorter timescales than the physical variable sea surface
temperature (SST). The ToE patterns of pCO2 and pH are spatially
very similar to DIC (dissolved inorganic carbon), yet the trends emerge much
faster – after roughly 12 yr for the majority of the global ocean area,
compared to between 10 and 30 yr for DIC. ToE of 45–90 yr are even larger
for SST. In general, the background noise is of higher importance in
determining ToE than the strength of the trend signal. In areas with high
natural variability, even strong trends both in the physical climate and
carbon cycle system are masked by variability over decadal timescales. In
contrast to the trend, natural variability is affected by the seasonal cycle.
This has important implications for observations, since it implies that
intra-annual variability could question the representativeness of irregularly
sampled seasonal measurements for the entire year and, thus, the
interpretation of observed trends. |
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