Contribution to a World Meteorological Organization (WMO) report

This document describes several projects being conducted at Lawrence Livermore National Laboratory. The projects described include the following: (1)Coupled Oceanic-Atmospheric General Circulation Modeling; (2)Coupled Atmospheric River Flow Simulation System; (3) Carbon-cycle Modeling; (4) Ocean Circulation Modeling; and (5) Analyzing Climate Model Variability with an Ensemble of AMIP Simulations

Engineering strategies to boost crop productivity by cutting respiratory carbon loss

Roughly half the carbon that crop plants fix by photosynthesis is subsequently lost by respiration. Nonessential respiratory activity leading to unnecessary CO₂ release is unlikely to have been minimized by natural selection or crop breeding, and cutting this large loss could complement and reinforce the currently dominant yield-enhancement strategy of increasing carbon fixation. Until now, however, respiratory carbon losses have generally been overlooked by metabolic engineers and synthetic biologists because specific target genes have been elusive. We argue that recent advances are at last pinpointing individual enzyme and transporter genes that can be engineered to (1) slow unnecessary protein turnover, (2) replace, relocate, or reschedule metabolic activities, (3) suppress futile cycles, and (4) make ion transport more efficient, all of which can reduce respiratory costs. We identify a set of engineering strategies to reduce respiratory carbon loss that are now feasible and model how implementing these strategies singly or in tandem could lead to substantial gains in crop productivity.Jeffrey S. Amthor, Arren Bar-Even, Andrew D. Hanson, A. Harvey Millar, Mark Stitt, Lee J. Sweetlove, and Stephen D. Tyerma

Crop response to elevated CO2 and world food supply. A comment on "Food for Thought..." by Long et al

Recent conclusions that new free-air carbon dioxide enrichment (FACE) data show a much lower crop yield response to elevated CO2 than thought previously - casting serious doubts on estimates of world food supply in the 21st century - are found to be incorrect, being based in part on technical inconsistencies and lacking statistical significance. First, we show that the magnitude of crop response to elevated CO2 is rather similar across FACE and non-FACE data-sets, as already indicated by several previous comprehensive experimental and modeling analyses, with some differences related to which "ambient" CO2 concentration is used for comparisons. Second, we find that results from most crop model simulations are consistent with the values from FACE experiments. Third, we argue that lower crop responses to elevated CO2 of the magnitudes in question would not significantly alter projections of world food supply. We conclude by highlighting the importance of a better understanding of crop response to elevated CO2 under a variety of experimental and modeling settings, and suggest steps necessary to avoid confusion in future meta-analyses and comparisons of experimental and model data

Seasonal variation in the temperature response of leaf respiration in Quercus rubra: foliage respiration and leaf properties

Leaf respiratory temperature responses and general leaf properties of Quercus rubra were measured throughout the 2003 growing season in a deciduous forest in the northeastern USA. Measurements were made in the upper and lower portions of the canopy at two sites with different soil water availability. Correlations among respiration and various leaf properties were examined. At a set temperature (10 and 20°C), area-based leaf respiration rates were higher in both the early and late growing season than in the mid-growing season (0•50 vs 0•33µmol CO2 m2 s-1at 10°C, on average). Upper-canopy leaves generally had higher respiration rates than lower-canopy leaves (0•53 vs 0•30 µmol CO2 m-2 s-1 at 10°C, on average). At the drier site a more significant seasonal pattern in respiration was observed, while at the more mesic site a stronger canopy-position effect was detected. E0, a model variable related to the overall energy of activation of respiration, varied only slightly (52±5 kJ mol-1K-1), and was not influenced by season, site or canopy position. Leaf properties (specific leaf area, nitrogen, soluble sugars) also varied with season, site and canopy position. Leaf N and reducing monose were positively correlated with leaf respiration rates. After isolating single factors (season, site, canopy position), reducing monose could partially explain the seasonality in respiration (32- 79%), and leaf N (Narea) was well correlated with the canopy-position effect. Our results suggest that the temporal and spatial heterogeneities of respiration need to be considered in ecosystem models, but significant simplifications may be made in Q. rubra by assuming a constant temperature coefficient (E0, 52•5 kJ mol-1in this study) or predicting the base respiration rate (R0) from well understood leaf properties