Reproduced from CO2Science.org

20th-Century ENSO Events

Mendelssohn, R., Bograd, S.J., Schwing, F.B. and Palacios, D.M.  2005.  Teaching old indices new tricks: A state-space analysis of El Niņo related climate indices.  Geophysical Research Letters 32: L07709, doi:10.1029/2005GL022350.

What was Done
Climate-alarmists often claim that global warming will increase both the frequency and intensity of ENSO events; and they use this claim in an attempt to convince the general public that continued burning of fossil fuels, which they claim is the major cause of the past century's rise in temperature, will lead to disastrous climatic consequences.  In the present study, Mendelssohn et al. investigate these claims by performing a statistical analysis known as state-space decomposition on three El Niņo-related indices (Southern Oscillation Index, its component sea level pressure series, and the NIŅO3 index) during the 20th century.

What was learned
The stochastic cycles produced by the state-space models were all relatively stationary, which, in the words of the investigative scientists, does "not support the idea that El Niņos have become more frequent."  With respect to the magnitude of ENSO events, they say there were some "outlier events" in the later portion of the record, which may suggest that ENSO magnitudes have increased in recent years, but they conclude that "it is premature to tell."

What it means
In contrast to long-standing climate-alarmist claims, ENSO events do not appear to have become more frequent over the 20th century.  With respect to their magnitudes, however, the situation is less clear, and we will probably have to wait several more cycles before a definitive answer can be obtained from statistical state-space decomposition analysis.  In the mean time, we invite you to examine the many other studies we have reviewed on this topic in our Subject Index (see ENSO - Relationship to Global Warming), which clearly suggest there is nothing unique or unprecedented about ENSO events of the past century.
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A Climate History of the Northwestern Mediterranean Region


Pla, S. and Catalan, J.  2005.  Chrysophyte cysts from lake sediments reveal the submillennial winter/spring climate variability in the northwestern Mediterranean region throughout the Holocene.  Climate Dynamics 24: 263-278.

What was done Chrysophytes are a diverse group of primarily freshwater algae with over 1,000 known species that dominate phytoplankton assemblages of temperate and cold oligotrophic lakes. A key feature of chrysophytes is their production of resting siliceous cysts, which preserve a record of the dynamics of lake algal populations that can be further analyzed for paleoclimate signals.  In the present study, the authors analyzed chrysophyte cyst data collected from 105 lakes in the Central and Eastern Pyrenees of northeast Spain to produce a history of winter/spring temperatures in this region throughout the Holocene.

What was learned
A significant oscillation was evident in the winter/spring temperature reconstruction in which the region's climate alternated between warm and cold phases over the past several thousand years.  Of particular note were the Little Ice Age, Medieval Warm Period, Dark Ages Cold Period and Roman Warm Period, the warmest of which intervals was the Medieval Warm Period, which started around 900 AD and was about 0.25°C warmer than it is currently.  Following the Medieval Warm Period, temperatures fell to their lowest values of the entire record (about 1.0°C below present), whereupon they began to warm, but remained below present-day values until the early 19th and 20th centuries, with one exception.  A significant warming was observed between 1350 and 1400, when temperatures rose a full degree Celsius to a value about 0.15°C warmer than the present, during what we refer to as the http://www.co2science.org/scripts/Template/MainPage.jsp?Page=subject/l/littlemwpLittle Medieval Warm Period.

Further examination of the authors' data reveals that the Modern Warm Period is not yet (and may never be) as warm as the Medieval Warm Period, for modern temperatures peaked in the 1970s-80s and declined throughout the 1990s.

What it means
In a regional contradiction of the strident claims of the world's climate alarmists, the results of this study suggest that winter and spring temperatures around the northwestern Mediterranean during the past two decades were no where near being unprecedented over the past two thousand years.

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Primary Production in the Adriatic Sea


Marasovic, I., Nincevic, Z., Kuspilic, G., Marinovic, S. and Marinov, S.  2005.  Long-term changes of basic biological and chemical parameters at two stations in the middle Adriatic.  Journal of Sea Research 54: 3-14.

Climate alarmists contend that CO2-induced global warming will wreck havoc with earth's biosphere, both on land and at sea; and in light of the global warming of the 20th century, which they claim was unprecedented over the past two millennia and produced temperatures that were likewise unprecedented, one would think there would be many signs of the predicted negative impacts. The study of Marasovic et al. provides a prime opportunity to search for such consequences in primary productivity data from the central sector of the Adriatic Sea.

What was done
Since the early 1960s, regular monthly observations of basic hydrographic, chemical and biological parameters, including primary production, have been made at two middle Adriatic oceanographic stations, one near the coast (Kastela Bay, Station 25) and one in the open part of the sea (Station 09). The authors analyze these data and present their interpretation of them.

What was learned
Mean annual primary production in Kastela Bay was determined to be about 430 mg C m-2 d-1 over the period 1962-72, exceeded 600 mg C m-2 d-1 over the period 1972-82, and rose to over 700 mg C m-2 d-1 over the period 1982-96, accompanied by a similar upward trend in percent oxygen saturation of the surface water layer. The initial value of primary production in the open sea was much less (approximately 150 mg C m-2 d-1), but it began to follow the upward trend of the Kastela Bay data after about one decade.

What it means
The authors state that "even though all the relevant data indicate that the changes in Kastela Bay are closely related to an increase of anthropogenic nutrient loading, similar changes in the open sea suggest that primary production in the Bay might, at least partly, be due to global climatic changes."  These changes, in their words, are "occurring in the Mediterranean and Adriatic Sea open waters" and may be directly related to "global warming of air and ocean," since "higher temperature positively affects photosynthetic processes."

Reviewed 27 July 2005

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