AT: Drought CO2 fertilization increases in stress conditions—IPCC reports agree Weiner 1997 (JONATHAN BAERT WIENER, William R. and Thomas L. Perkins Professor of Law Professor of Environmental Policy at Duke University School of Law, “Protecting the Global Environment,” in John D. Graham and Jonathan Baert Wiener, Risk vs. Risk: Tradeoffs in Protecting Health and the Environment. Cambridge, MA: Harvard U P, 1997: pp. 193-225) Rather than fading under stressed growing conditions, the¶ positive effects of elevated CO2 appear to be comparatively¶ larger in the face of stresses-limited nutrients or water, salinity,¶ cool temperatures, or pollution-than in already optimal¶ conditions Increasing CO2 concentrations¶ spurs plants (IPCC 1990b, p. 2.5). to close their stomata and thereby to reduce transpiration (small openings in¶ leaf tissues) (water loss to¶ the air through per unit of photosynthesis, increasing¶ their water use efficiency and their resistance to¶ the stomata) drought by about 30 percent CO2 fertilization could therefore be (Rosenberg 1990, 1991; IPCC¶ 1990b, pp. 2.4-2.5). especially¶ valuable in arid areas and areas that might lose precipitation¶ under global warming. And doubling CO2 concentrations¶ actually raises the optimum temperature for¶ photosynthesis by in C3 plants about 4 to 6 degrees so¶ global warming itself is not likely to inhibit the carbon fertilization¶ effect C, (IPCC 1990b, pp. 2.4-2.5). As for weed competition,¶ the IPCC noted that fourteen of the world's seventeen¶ worst weeds are C4 plants amid C3 crops, so that CO2 enrichment¶ might in fact help crops outperform these weeds (IPCC¶ 1990b, p. 2.5).
AT: Drought CO2 fertilization increases in stress conditions—IPCC reports agree Weiner 1997 (JONATHAN BAERT WIENER, William R. and Thomas L. Perkins Professor of Law Professor of Environmental Policy at Duke University School of Law, “Protecting the Global Environment,” in John D. Graham and Jonathan Baert Wiener, Risk vs. Risk: Tradeoffs in Protecting Health and the Environment. Cambridge, MA: Harvard U P, 1997: pp. 193-225) Rather than fading under stressed growing conditions, the¶ positive effects of elevated CO2 appear to be comparatively¶ larger in the face of stresses-limited nutrients or water, salinity,¶ cool temperatures, or pollution-than in already optimal¶ conditions (IPCC 1990b, p. 2.5). Increasing CO2 concentrations¶ spurs plants to close their stomata (small openings in¶ leaf tissues) and thereby to reduce transpiration (water loss to¶ the air through the stomata) per unit of photosynthesis, increasing¶ their water use efficiency and their resistance to¶ drought by about 30 percent (Rosenberg 1990, 1991; IPCC¶ 1990b, pp. 2.4-2.5). CO2 fertilization could therefore be especially¶ valuable in arid areas and areas that might lose precipitation¶ under global warming. And doubling CO2 concentrations¶ actually raises the optimum temperature for¶ photosynthesis in C3 plants by about 4 to 6 degrees C, so¶ global warming itself is not likely to inhibit the carbon fertilization¶ effect (IPCC 1990b, pp. 2.4-2.5). As for weed competition,¶ the IPCC noted that fourteen of the world's seventeen¶ worst weeds are C4 plants amid C3 crops, so that CO2 enrichment¶ might in fact help crops outperform these weeds (IPCC¶ 1990b, p. 2.5).
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