Increasing atmospheric CO₂ concentrations lowers oceanic pH and carbonate ion concentrations, thereby decreasing the level of saturation of calcium carbonate [Feely et al., 2004]. This acidification will eventually lead to undersaturation and dissolution of calcium carbonate in parts of the surface ocean. Besides affecting the global carbon cycle, these changes threaten marine organisms that form their exoskeletons out of CaCO₃, which are essential components of the marine food web [Orr et al., 2005]. We investigate magnitude and pattern of ocean acidification due to increasing atmospheric CO₂ concentrations and global warming, both for the recent past and the near future, using the reduced complexity, Bern 2.5-D physical-biogeochemical climate model and a series of CO₂ emission scenarios and CO₂ stabilization profiles provided by the Intergovernmental Panel on Climate Change (IPCC). The focus of the study is on the impact of global warming and induced ocean circulation changes on the projected oceanic pH and carbonate ion reductions.

Anthropogenic CO₂ uptake by the ocean will decrease both the pH and the aragonite saturation state (Ω_arag) of seawater. However, the factors controlling future changes in pH and Ω_arag are independent and will respond differently to oceanic climate change feedbacks such as ocean warming, circulation and biological changes. We examine the sensitivity of these CO₂-related parameters to climate change feedbacks within a coupled atmosphere-ocean model. Although surface pH is projected to decrease relatively uniformly by ~0.25 by the year 2100, we find pH to be insensitive to climate change feedbacks, whereas Ω_arag is buffered by ~15%. The independent climate change response between pH and Ω_arag is attributed solely to the opposing effects associated with ocean warming, which increases Ω_arag but lowers pH. Our result implies that future climate change projections for surface ocean pH can be adequately simulated using ocean-only models, however for Ω_arag more complex coupled atmosphere-ocean models are required.

We applied the Bayesian probability inversion and a Markov Chain Monte Carlo (MCMC) technique to a terrestrial ecosystem model and analyzed uncertainties of estimated carbon transfer coefficients and simulated carbon pool sizes. The study used six data sets of soil respiration, woody biomass, foliage biomass, litterfall, carbon content in the litter layers, carbon content in mineral soil measured under both ambient CO₂ (350 ppm) and elevated CO₂ (550 ppm) plots from 1996 to 2000 at the Duke Forest Free-Air CO₂ Experiment (FACE) site.

CO₂ and O₃ are accumulating in the atmosphere and are potent modifiers of forest growth, causing changes that could alter composition and functioning of forest ecosystems. We have examined the effects of elevated CO₂ ( +CO₂; 560ppm), elevated O₃ (+O₃; 1.5X ambient), and their combination (+CO₂+O₃), on the growth and productivity of model aspen (Populus tremuloides Michx.) and aspen-birch (Betula papyrifera Marsh.) forest ecosystems growing in an open free-air exposure (FACE) system in northern Wisconsin USA. After eight years of fumigation, +CO₂ increased aspen tree and stand volume growth by 39 + 9% and 38 + 10%, respectively, whereas +O₃ decreased them by 27 + 6% and 34 + 4%, respectively. +CO₂+O₃ resulted in a net canceling of the effects of the single gases on aspen growth. Forest growth responses to +CO₂ and +O₃ interacted strongly with present-day interannual variability in climatic conditions. The amount and timing of photosynthetically active radiation and temperature coinciding with growth phenology explained 33-61% of the annual variation in growth responses of aspen trees, and explained 20-63% of annual variation in growth responses of aspen tree stands.

We examined the photosynthetic and growth traits of two woody species (birch) that are dominant in northern Japan under elevated CO₂ concentration ([CO₂]), using a free air CO₂ enrichment (FACE) system. Our results suggest that it is necessary to consider not only leaf-level photosynthesis but also the entire plant physiology when using photosynthesis to evaluate the growth response of two birch saplings under elevated [CO₂].

The Forest-Atmosphere Carbon Transfer and Storage (FACTS-II) Project in northern Wisconsin is examining the interacting effects of elevated carbon dioxide (CO₂) and ozone (O₃) concentrations on the productivity, sustainability, and competitive interactions in a regenerating northern hardwood ecosystem. A key component of this project involves an examination of the micrometeorological feedback mechanisms that can alter atmospheric environments within and above vegetation layers exposed to elevated CO₂ and O₃ concentrations. This paper provides a brief summary of some of the observed forest micrometeorological responses to elevated CO₂ and O₃ concentrations at the FACTS-II study site over the 1999-2004 period.

The three cereal crops rice, maize and wheat cover over 75% of the total food production of Nepal. All the three crops rice, maize and wheat showed increased yield with doubling the CO₂ level but also followed a declined tendency at the elevated temperature. Among the three crops, maize was the most affected by the rise in temperature although increased CO₂ level could increase the crop yield. The Terai plains and the hills of Nepal were more affected. The mountains, on the other hand, showed a favorable tendency.