That's fun, jetzt muss ich mir glatt selbst antworten. Aus dem IPCC-SREX zum Risikomanagement und den Extremevents (Seite 8/9) [ipcc-wg2.gov]:


"Climate Extremes and Impacts

There is evidence from observations gathered since 1950 of change in some extremes. Confidence in observed changes in extremes depends on the quality and quantity of data and the availability of studies analyzing these data, which vary across regions and for different extremes. Assigning "low confidence" in observed changes in a specific extreme on regional or global scales neither implies nor excludes the possibility of changes in this extreme. Extreme events are rare, which means there are few data available to make assessments regarding changes in their frequency or intensity. The more rare the event the more difficult it is to identify long-term changes. Global-scale trends in a specific extreme may be either more reliable (e.g., for temperature extremes) or less reliable (e.g., for droughts) than some regional-scale trends, depending on the geographical uniformity of the trends in the specific extreme. The following paragraphs provide further details for specific climate extremes from observations since 1950. [3.1.5, 3.1.6, 3.2.1]

It is very likely that there has been an overall decrease in the number of cold days and nights, and an overall increase in the number of warm days and nights, at the global scale, that is, for most land areas with sufficient data. It is likely that these changes have also occurred at the continental scale in North America, Europe, and Australia. There is medium confidence in a warming trend in daily temperature extremes in much of Asia. Confidence in observed trends in daily temperature extremes in Africa and South America generally varies from low to medium depending on the region. In many (but not all) regions over the globe with sufficient data, there is medium confidence that the length or number of warm spells or heat waves has increased. [3.3.1, Table 3-2]

There have been statistically significant trends in the number of heavy precipitation events in some regions. It is likely that more of these regions have experienced increases than decreases, although there are strong regional and subregional variations in these trends. [3.3.2]

There is low confidence in any observed long-term (i.e., 40 years or more) increases in tropical cyclone activity (i.e., intensity, frequency, duration), after accounting for past changes in observing capabilities. It is likely that there has been a poleward shift in the main Northern and Southern Hemisphere extratropical storm tracks. There is low confidence in observed trends in small spatial-scale phenomena such as tornadoes and hail because of data inhomogeneities and inadequacies in monitoring systems. [3.3.2, 3.3.3, 3.4.4, 3.4.5]

There is medium confidence that some regions of the world have experienced more intense and longer droughts, in particular in southern Europe and West Africa, but in some regions droughts have become less frequent, less intense, or shorter, for example, in central North America and northwestern Australia. [3.5.1]

There is limited to medium evidence available to assess climate-driven observed changes in the magnitude and frequency of floods at regional scales because the available instrumental records of floods at gauge stations are limited in space and time, and because of confounding effects of changes in land use and engineering. Furthermore, there is low agreement in this evidence, and thus overall low confidence at the global scale regarding even the sign of these changes. [3.5.2]

It is likely that there has been an increase in extreme coastal high water related to increases in mean sea level. [3.5.3]

There is evidence that some extremes have changed as a result of anthropogenic influences, including increases in atmospheric concentrations of greenhouse gases. It is likely that anthropogenic influences have led to warming of extreme daily minimum and maximum temperatures at the global scale. There is medium confidence that anthropogenic influences have contributed to intensification of extreme precipitation at the global scale. It is likely that there has been an anthropogenic influence on increasing extreme coastal high water due to an increase in mean sea level. The uncertainties in the historical tropical cyclone records, the incomplete understanding of the physical mechanisms linking tropical cyclone metrics to climate change, and the degree of tropical cyclone variability provide only low confidence for the attribution of any detectable changes in tropical cyclone activity to anthropogenic influences. Attribution of single extreme events to anthropogenic climate change is challenging. [3.2.2, 3.3.1, 3.3.2, 3.4.4, 3.5.3, Table 3-1]"

Der rot markierte Teil entspricht dem, was ich vorhin (ebenfalls rot hervorgehoben) ungefaehr gleichlautend von mir gegeben hatte:


K.a.r.S.t.e.N schrieb:
-------------------------------------------------------
> Volle Zustimmung! Siehe auch mein Edit im Posting
> oben. Was die Varianz angeht, haben wir das
> Problem, dass die Anzahl der Faelle viiiiieeeel zu
> gering ist. Da wirst Du vielleicht nach 100 Jahren
> Klimawandel einen Trend sehen (und somit eine
> verlaessliche Aussage machen koennen), aber
> derzeit ist da nichts zu holen. Weder global, und
> erst recht nicht regional. Da muessten schon fuenf
> 2003er-Events innerhalb einer Dekade vorkommen, um
> hier wirklich was "in der Hand" zu haben. Insofern
> kann man derzeit nur das Offensichtliche
> ausfuehren: Waermerekorde nehmen zu und
> Kaelterekorde nehmen ab.



Das war jetzt derbe Selbstbeweihraeucherung, oder? I'm sorry ;-). Soll nicht wieder vorkommen ...


@fabile: Keine Frage, selbst 2-3 Zehntel Grad machen auf diesem Temperaturlevel nen entscheidenden Unterschied. Ob die Haeufung ab ca. 2000 Zufall ist, who knows 4 sure. Dass sie sich wahrscheinlich gehaeuft haben, kann man im orange markierten Teil aus dem SREX nachlesen: Medium confidence* fuer erhoehte Anzahl an Hitzewellen. Dass diese Haeufung wahrscheinlich kein Zufall ist, dass wissen wir aus den Klimaprojektionen, die genau das vorhersagen (siehe auch S.11-15 im Report).

Cheers KarSteN



* Was Medium confidence meint, kann man auf S. 21 im SREX nachlesen.

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