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Volume 3 Number 1:  1 January 2000

Editorial
Questions, Questions, Questions: Is Climate Science Good Enough to Predict the Future with Any Confidence?: Does anybody believe that all we have left to do in the realm of climate modeling is "dot the 'i's and cross the 't's"?  Or maybe carry out some model calculation to one more significant digit?  In listening to the chorus of voices lamenting the dismal prognosis for our planet if we do not act now to reduce CO2 emissions, one could get the impression that climatology is one of the world's more exact sciences, and that its practitioners can forecast the future with great skill.  Nothing, however, could be further from the truth, especially with respect to the question of rising atmospheric CO2 levels and their potential to induce significant climate change.

Journal Reviews
Solar Influences on Holocene Climate: A review of what is known about the potential climatic effects of solar variability and observed climate variability throughout the Holocene suggests that the former may have been responsible for the latter, and that solar variability may have played a greater role in the warming of the past century than the Intergovernmental Panel on Climate Change would like people to believe.

Jet Aircraft Contrails Reduce the Diurnal Amplitude of Earth's Surface Air Temperature: A model study of the climatic effects of jet aircraft contrails suggests that they tend to cool the earth's surface during the day and warm it at night.

Ship Emissions Perturb Radiation Balance Over the Sea: A data-plus-model approach to evaluating the climatic consequences of ship emissions suggests that they have a modest cooling effect on the planet.

Solar Forcing of Climate Change: In reviewing what is known about relationships between the abundance of cosmogenic isotopes (14C and 10Be) and Holocene and preceding glacial climates, the authors make a well-reasoned case for linking millennial-scale climate oscillations to solar activity.

A Role for CO2 in Western Juniper Density and Cover Expansion?: A study of three different land-use sites in central Oregon seems to point to the ongoing rise in the air's CO2 concentration as a significant factor in increasing the cover and density of western juniper there between 1951 and 1994.

Arctic Sea Ice: In Retreat?  Due to Global Warming?  Caused by CO2?: A comparison of several observational histories of Arctic sea ice extent with climate model predictions of CO2-induced, global-warming-induced, melting of Arctic sea ice is touted as demonstrating, to a probability of greater than 99.9%, that reductions observed between 1953 and 1998 are due to something other than natural climate variability.  To this claim we say Hogwash!

Arctic Sea Ice: Is It Being "Transformed"?: In what we believe to be a misinterpretation of their own data, the authors of this paper suggest that Arctic sea ice cover is "in transition" and that it is experiencing an ongoing "transformation" (a gradual and consistent reduction in area and thickness), which, if continued, could lead to a markedly different ice regime in the Arctic, so different, in fact, that Science staff writer Richard Kerr asks, in the title of a related News of the Week story, "Will the Arctic Ocean lose all its ice?"

Effects of Elevated CO2 on a Parasitic Plant and its Host: After 75 days of differential CO2 exposure, there were no significant differences in the dry weights of Trifolium repens not infected with the weedy parasite Orobanche minor.  However, at ambient CO2 concentration, infected plants only contained about half the biomass exhibited by uninfected control plants.  In contrast, at elevated CO2 concentration, infected plants contained about 80% of the biomass displayed by their respective controls.  Thus, the rising CO2 content of the air will likely alleviate biomass reductions in leguminous species presently caused by this parasitic plant.

Effects of Elevated CO2 on Two C3 Parasitic Plants and a Common C4 Host: After two months of differential CO2 exposure, sorghum plants not infected by parasitic C3 weedy species exhibited 36% more biomass when grown at elevated CO2 than they did at ambient CO2 concentrations.  When infected by Striga hermonthica and Striga asiatica, the absolute biomass of sorghum significantly decreased at both CO2 concentrations, but was less for CO2-enriched plants infected with S. hermonthica than it was for ambiently-grown plants infected with the same parasite.  However, regardless of parasite species, elevated CO2 significantly enhanced the percentage growth of infected host plants, suggesting that the rising atmospheric CO2 concentration will help crop plants better deal with parasitic infections.  In addition, elevated CO2 reduced the growth of both parasitic species, thus suggesting that they may pose less of a problem to agricultural production in the future.

Effects of Elevated CO2 and Nutrients on a Parasitic Plant and its Hosts: After two months of elevated CO2 exposure, the parasitic plant Rhinanthus alectorolophus displayed greater biomass production in high, rather than in low, fertility soils, in a host species-dependent manner.  In addition, elevated CO2 did not significantly influence the effects of the parasite on it hosts, nor the competitive interactions among two host plants directly or indirectly via the parasite.