The Rate Debate Slowing
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- Co2 root cause of decreasing crop yields Cao et al 12
- Elevated CO2 increases photosynthesis Albert et al.
Warming Bad - "Even If"Framing issue – warming kills yeilds of crops produced by CO2 increase – prefer our comparative evidence EPA 11 (Enviormental Protection Agency, US government program to preserve the enviorment, Agriculture and Food Supply Impacts & Adaptation, http://www.epa.gov/climatechange/impacts-adaptation/agriculture.html) Crops grown in the United States are critical for the food supply here and around the world. U.S. exports supply more than 30% of all wheat, corn, and rice on the global market. [2] Changes in temperature, amount of carbon dioxide (CO2), and the frequency and intensity of extreme weather could have significant impacts on crop yields. Warmer temperatures may make many crops grow more quickly, but warmer temperatures could also reduce yields. Crops tend to grow faster in warmer conditions. However, for some crops (such as grains), faster growth reduces the amount of time that seeds have to grow and mature. [1] This can reduce yields (i.e., the amount of crop produced from a given amount of land). For any particular crop, the effect of increased temperature will depend on the crop's optimal temperature for growth and reproduction. [1] In some areas, warming may benefit the types of crops that are typically planted there. However, if warming exceeds a crop's optimum temperature, yields can decline. Higher CO2 levels can increase yields. The yields for some crops, like wheat and soybeans, could increase by 30% or more under a doubling of CO2 concentrations. The yields for other crops, such as corn, exhibit a much smaller response (less than 10% increase). [3] However, some factors may counteract these potential increases in yield. For example, if temperature exceeds a crop's optimal level or if sufficient water and nutrients are not available, yield increases may be reduced or reversed. More extreme temperature and precipitation can prevent crops from growing. Extreme events, especially floods and droughts, can harm crops and reduce yields. For example, in 2008, the Mississippi River flooded just before the harvest period for many crops, causing an estimated loss of $8 billion for farmers. [1] Dealing with drought could become a challenge in areas where summer temperatures are projected to increase and precipitation is projected to decrease. As water supplies are reduced, it may be more difficult to meet water demands. Many weeds, pests and fungi thrive under warmer temperatures, wetter climates, and increased CO2 levels. Currently, farmers spend more than $11 billion per year to fight weeds in the United States. [1] The ranges of weeds and pests are likely to expand northward. This would cause new problems for farmers' crops previously unexposed to these species. Moreover, increased use of pesticides and fungicides may negatively affect human health. [1] Co2 root cause of decreasing crop yields Cao et al 12 (Pongratz, J., Lobell, D. B., Cao L. and Caldeira, K. (2012), Stanford University. Crop yields in a geoengineered climate. Nature Climate Change. DOI: 10.1038/NCLIMATE1373, http://ec.europa.eu/environment/integration/research/newsalert/pdf/279na3.pdf) Unless emissions of CO2 from human activities are reduced, climate change will affect crop yields, particularly through changes in rainfall and temperature. The impact will vary across regions and there is the risk that food supply, particularly in already vulnerable areas, could be threatened. One short-term measure proposed in the fight against climate change is to reflect back some of the sun’s radiation before it reaches the Earth, thereby counteracting global warming. An example of such an approach, called solar radiation management (SRM), is to deflect sunlight off sulphate particles that have been injected into the stratosphere (upper atmosphere). However, there are concerns that such ‘sunshade’ geoengineering schemes could reduce crop yields and lower the global production of food by causing changes in precipitation. This study compared large-scale changes in crop yields under two future climate scenarios. Changes in global temperatures and precipitation relative to today were modelled first for: a) a doubling of the atmospheric concentration of CO2 compared with current levels (‘2 x CO2 scenario’) and b) a doubling of the atmospheric concentration of CO2, but with a climate modified by SRM to maintain average global temperatures at current levels (‘SRM scenario’). These two climate change scenarios were then used to estimate changes in the yields and production of three major crops: wheat, maize and rice. In addition to the effects of temperature and precipitation on crop yields, the impact of elevated levels of CO2 on crop productivity was included in the analysis, as previous studies have found that higher levels of atmospheric CO2 act like a fertiliser and can increase yields. For the 2 x CO2 scenario, overall small changes in global yields of the three crops were found. There was a slight fall in yield for maize and a slight increase for wheat and rice. These were caused by the combined negative effects of climate change and the positive impact of increased fertilisation by CO2. Higher temperatures, rather than changes in precipitation, were responsible for most of the reduction in crop yields. Under the SRM scenario, the yields of all three crops increased at all latitudes, mainly through the beneficial influence of higher CO2 levels, compared with current conditions, but lower temperatures compared with the 2 x CO2 scenario. Nevertheless, changes in yields and production are not uniform across all regions and it is likely that the current pattern of food production and global food markets will be altered. Although on a large regional scale SRM is simulated to increase yields compared to the 2xCO2 scenario, individual small regions may exhibit losses in yields due to local climate change. In particular when these regions are areas of subsistence farming, this may cause local food insecurity. In addition, the researchers point out that SRM does not modify other harmful effects of higher CO2 levels, such as ocean acidification, which could also affect marine food supplies. Given the anticipated and unknown consequences of modifying the climate by SRM, the researchers point out that the reduction of CO2 emissions is the most certain way to reduce risks of dangerous climate change impacts. Elevated CO2 increases photosynthesis Albert et al. (K. R. ALBERT1, H. RO-POULSEN2, T. N. MIKKELSEN1, A. MICHELSEN2, L. VAN DER LINDEN1 & C. BEIER, 1Biosystems Division, Risø DTU, Frederiksborgvej 399, 4000 Roskilde and 2Terrestrial Ecology, Department of Biology, University of Copenhagen, Øster Farigmagsgade 2D, 1353 Copenhagen K, Denmark) 2011 (K.R., “Effects of elevated CO2, warming and drought episodes on plant carbon uptake in a temperate heath ecosystem are controlled by soil water status ,” Plant, Cell and Environment (2011) 34, 1207–1222 Pages 10-11) //CL Elevated CO2 increased photosynthesis and WUE during most of the growing season. The increased photosynthesis was associated with, or driven by, increased intercellular CO2 concentration (Fig. 5) generating higher substrate availability for Rubisco, in line with, for example Ainsworth & Long (2005) and Ainsworth & Rogers (2007), and thus stimulation of photosynthesis also led to increased leaf C/N ratios. Surprisingly, no general reduc- tion in stomatal conductance was seen in elevated CO2, although this is often reported (e.g. Ainsworth & Long 2005; Ainsworth & Rogers 2007). This suggests that the improved WUE observed in our elevated CO2 plots was caused by increased photosynthesis. The soil water savings observed under elevated CO2 were not clearly coupled to reductions in stomatal conductance, which, together with LAI adjustments, have been the primary water-saving mechanisms in other elevated CO2 studies (Niklaus, Spinnler & Körner 1998; Morgan et al. 2004; Leuzinger & Körner 2007). However, the conserva- tion of soil water in our study may have been associated with reduced stomatal conductance, as shown by the marginally significant effects seen in August and October. The robust detection of these responses may have been hindered by the lesser statistical power provided by the monthly measurements of leaf gas exchange, compared to the greater statistical power provided by the half-hourly measurements of SWC. Further, heterogeneous structural conditions may prevail within the Calluna canopy, and we cannot exclude that shoots, other than the uppermost shoots selected for measurement, may have responded to the elevated CO2 by reducing stomatal conductance. This demonstrates that more frequent measurements of leaf gas exchange may be necessary to fully monitor changes in stomatal conductance through periods of water scarcity, but also that Calluna seems to take advantage of the soil water savings occurring to sustain photosynthesis in elevated CO2 during dry periods. Because rewetting clearly increased photosynthesis, leaf-to-shoot ratio and the C/N ratio in elevated CO2 plots, it seems that the photosynthetic stimu- lation is closely dependent on water availability, with low photosynthesis stimulation during dry periods and high photosynthesis stimulation when water availability is high. Interestingly, soil water savings were not detected over the upper 0–20 cm, but only over 0–60 cm. This suggests that intensive competition for water in the upper 0–20cm occurred and that the species with the largest capacity for water uptake in the 20–60 cm compartment, for example via a deeper and more extensive roots system, are likely to be the primary species causing the water saving. Reduced water consumption, via stomatal conductance or biomass reduction in the co-occuring grass Deschampsia flexuosa, could potentially also influence the SWC. In Calluna, the rooting systems may extend down to 84 cm (Gimingham 1960), while the co-occuring Deschampsia extends down to 58 cm (Scurfield 1954). On the CLIMAITE field site, total root biomass in 0–15 cm was reported not to differ between species, but fine root biomass were magnitudes higher in Deschampsia (Andresen et al. 2009). This may indicate larger capacity for water uptake in Calluna in the deeper soil layers, but more information taking into account both above- and below-ground biomass distributions, as well as stomatal conductance, are needed to investigate these issues. Directory: files files -> Answer True False 2 points Question 2 files -> Integer programming and game theory files -> 4 Integer Programming files -> Bpa vehicle Window Repair Scenario #1 task: Procure vehicle window relacement. 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