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Volume 2 Number 10:  15 May 1999

Editorial
"Human Contribution to Climate Change Remains Questionable": We discuss a few principles about the search for truth in science, especially climate science.

Journal Reviews
A 300-Year Examination of "Persistent" ENSO Events: An analysis of ENSO 300-year ENSO data suggests that long and persistent El Niņos are a regularly occurring feature of earth's climate.

A 1400-Year Record of ENSO Variability: Analyses of Nile river data for the last 14 centuries indicate that the El Niņo events of the past two decades are not without historical precedent.

Century-Scale Drought: Analysis of a 2100-year record of drought in the northern Great Plains reveals a possible solar-inducing mechanism with periodicities of approximately 100, 130, 200 and 400 years.

Interannual and Interdecadal Climate Variations: The authors studied precipitation and temperature trends over several regions of the conterminous United States, finding various linkages to ENSO events.

Millennial Temperature Change in Alaska: Tree-ring analyses indicate temperatures both warmer and colder than present in southern Alaska over the last 1100 years.

A 245-Year Temperature Record in Europe: A long-term analysis of temperature records in Europe since 1751 reveals that Europe has not warmed to the degree predicted by numerical climate models.

Effects of Elevated CO2 and Water Stress on Red Oak: Red oak seedlings grown for 8 to 11 weeks in controlled environment chambers with 700 ppm atmospheric CO2 displayed decreased sink strength in shoots and increased sink strength in roots, especially when water-stressed, thus allowing greater root development to occur.  This phenomenon contributed to enhanced drought tolerance in CO2-enriched seedlings and led to the complete amelioration of water stress in seedlings grown at 700 ppm CO2, which had total biomass values similar to those of well-watered plants grown at 400 ppm CO2.

Effects of Elevated CO2 and Drought on Mesquite Seedlings: Mesquite seedlings of different genotypes that were exposed to elevated CO2 during an 82-day water stress treatment displayed greater biomass and maintained more favorable water relations than plants grown at ambient CO2.  In addition, atmospheric CO2 enrichment more than doubled seedling survivorship to drought, regardless of genotype.  Thus, the increasing CO2 content of the air will positively impact seedling growth, water relations, and drought survivorship without decreasing genetic diversity in this species.

Interactive Effects of CO2 and Ozone on Soybeans: In an open-top chamber study of soybeans, it was found that elevated CO2 enhanced rates of photosynthesis in the presence or absence of ozone and typically ameliorated the negative effects of ozone on carbon assimilation, suggesting that the reduced stomatal apertures caused by atmospheric CO2 enrichment may provide protection against other aerial pollutants as well.

Interactive Effects of Elevated CO2 and Ozone on Scots Pine: In an open-top chamber study of 20-year old Scots pine, it was determined that elevated CO2 did not significantly affect starch accumulation in needles until the third year of treatment exposure, at which time it was significantly increased.  In addition, neither elevated CO2 or O3 had any effects on secondary metabolite production throughout the 3-year study.

Effects of Lifetime Exposure to Elevated CO2 on Antioxidative Enzymes in Mature Oak Trees: Mature holm and white oak trees growing near natural CO2 springs in central Italy for 30 to 50 years displayed significantly lower activities of antioxidative enzymes than similar trees growing away from the CO2 springs.  This finding indicates that simple changes in leaf physiology can persist for decades in trees as they grow and mature.  In addition, it shows that growth in elevated CO2 causes less intrinsic oxidative stress, which reduces the need for antioxidative enzymes.