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| Titel |
El Niño Southern Oscillation (ENSO) and global warming |
| VerfasserIn |
B. Nyenzi, P. F. Lefale |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7340
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| Digitales Dokument |
URL |
| Erschienen |
In: 1st Alexander von Humboldt International Conference ; Nr. 6 (2006-01-09), S.95-101 |
| Datensatznummer |
250003244
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| Publikation (Nr.) |
 copernicus.org/adgeo-6-95-2006.pdf |
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| Zusammenfassung |
| It is widely accepted by the international
scientific community that human activities have increased atmospheric
concentrations of
greenhouse gases (GHG) and aerosols since the pre-industrial era. This
increase has contributed to most of the warming (0.6±0.2°C)
observed over the 20th century, land areas warming more than the
oceans, with the 1990s very likely to be the warmest decade of the 20th
century (IPCC, 2001). How this warming influences the occurrence, severity
and frequency of ENSO episodes remains highly uncertain. The IPCC (2001)
assessment of the scientific literature found insufficient evidence to
suggest any direct attribution between increase in ENSO events that occurred
in the last 20 to 30 years of the 20th century and global warming
(IPCC, 2001). However, assessments carried out since then (e.g. IPCC Fourth
Assessment Report (AR4), in preparations) suggest El Niño events have
become more frequent, persistent and intense during the last 20 to 30 years
compared to the previous 100 years. Attribution to global warming, however,
remains highly uncertain. Efforts to simulate and model past, present and
future behaviour of ENSO under a warming world due to enhanced GHG
concentrations produce conflicting results. Since substantial
internally-generated variability of ENSO behaviour on multi-decadal to
century timescales occurs in long, unforced atmospheric-oceanic general
circulation model (AOGCM) simulations, the attribution of past and future
changes in ENSO amplitude and frequency to external forcing like GHG
concentrations cannot be made with certainty. Such attribution would require
extensive use of ensemble climate experiments or long experiments with
stabilised GHG forcing. Although there are now better ENSO simulations in
AOGCM, further model improvements are needed to simulate a more realistic
Pacific climatology and seasonal cycle of the key modes influencing the
climate of the region, as well as more realistic ENSO variability. More
research is needed to further enhance scientific understanding of possible
teleconnections between ENSO and global warming. It is worth noting the IPCC
AR4 due to be release in September 2007, would provide a more detailed
assessment of ENSO and global warming than what is being covered in this
paper. |
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