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- ATMOSPHERIC COMPOSITION 2.1 Carbon Dioxide 2.1.1 Atmospheric Composition
7.2.4 Geoengineering In the past, the science community has, in general, considered geoengineering apporaches for offsetting the effects of an enhanced greenhouse gas effect as being too risky to be seriously considered as policy options. Recent publications in respected scientific journals indicate that that is no longer the case. Discouraged by the lack of progress in international efforts to develop serious action plans to reduce the risks of climate change, several prominent research scientists have now suggested that it is time to properly investigate the feasibility and implications of such options in case an emergency escape mechanism is needed in the future to stave off global disaster. One such hypothesis involves the installation of large mirrors in the upper atmosphere to reflect incoming sunlight to help cool the planet. Model studies suggest that, while such cooling would also affect other aspects of the climate system, these impacts would be much less significant than that expected due to enhanced greenhouse gas warming. Another proposal is to inject large quantities of sulphates into the stratosphere annually in order to sustain a reflective aerosol layer in the upper atmosphere and thus also shade the Earth’s surface from incoming shortwave solar radiation. The effect would, in theory, be much like that of regular large volcanic eruptions that are known to cause significant surface cooling for several years after they occur. About 5.3 Mt of sulphur would need to be injected into the stratosphere annually (or less than 10% of current human emissions of sulphur into the troposphere) to offset the projected greenhouse gas forcing of 4 W/m2 expected by 2100. Proponents do not recommend such programs be implemented, but argue that we should undertake related research now to ensure we are prepared in the case such emergency measures are really needed in the future1007-1009. Related studies have already raised a number of important concerns about the broader environmental implications of such initiatives. For example, a sustained layer of sulphates in the stratosphere would change the vertical heating structure of the atmosphere and change stratospheric circulation, impacting surface weather in ways that are very difficult to predict. Because of the geographical variation of global surface albedo, reduced surface solar irradiation would also change the pattern of surface heating and thus cause regional changes in climate that could be large. Tropics would likely cool while high latitudes would warm, ENSO variability would likely weaken while Atlantic overturning would become stronger. Injecting sulphate aerosols into the stratosphere would also delay the recovery of its ozone layer. It would also cause an increase in stratospheric ion concentrations, affecting the atmosphere’s electrical properties. Climate data following the Pinatubo eruption also support the argument that reduced shortwave radiation at the surface would reduce surface evaporation, global precipitation and river runoff. Sensitivity studies suggest changes in short wave radiation forcing would change precipitation by about 2.4% per degree of temperature change, while response for greenhouse gas forcing is only 1.5%/°C. Furthermore, sulphate offsets would do nothing to mitigate ocean acidification due to continuing high atmospheric CO2 levels. Finally, related international agreements to permit such injections would be much more difficult to negotiate than greenhouse emission reduction themselves. Not surprisingly, many scientists have expressed dismay that the current failure to seriously deal with the risks of climate change has indeed necessitated an engineering proposal such as this. They argue strongly against considering sulphate aerosol injections as an option for serious consideration in policy fora at this time. However, they acknowledge that the background research into the feasibility and implications must be done1010-1021. Another significant geoengineering debate has centered on the feasibility and environmental implications of ocean fertilization to enhance biological production in surface waters. Such production would likely increase the export of detritus into deep ocean waters for long-term storage as a carbon sink. While past experiments in the North Pacific have not been promising, recent results from iron fertilization experiments in the Southern Ocean have been much more positive. However, there are many unknowns with respect to the broader effects of such manipulation, if conducted on much larger scales, on ocean chemistry and the food chain. Much more research is also required here before ocean fertilization should be seriously considered as a policy options1022. Deliberate enhancement of the Earth’s surface albedo has also been suggested as a means of reducing radiative forcing by about 0.76 W/m2. Again, related climate feedbacks and socio-economic implications have not been explored1023. 7.3 Adaptation Numerous recent studies have drawn attention to the need to ensure that development of strategies to adapt to climate change should be integrated into, or at least undertaken as a complement to local, national and international agendas aimed at mitigating the risks of climate change. Furthermore, both should be an inherent component of broader sustainable development policies. This integration of effort encourages a country or community to seek maximum co-benefits for initiatives undertaken, and to avoid initiatives that address one area of concern at the expense of another. It would also help ensure that policy makers engage in all areas of concern, rather than focusing on one at the expense of the others. Such integration requires a good understanding of the linkages, tradeoffs and synergies between climate change mitigation, adaptation and sustainable development. Some important challenges in doing so include the large differences in the geopolitical scale on which adaptation and mitigation are often undertaken and the varying capacity to implement effective policies from one community to the next. Stakeholder and broader community involvement in developing these strategies, plus the use of tools such as transition theory and vulnerability assessments, are important mechanisms for promoting such integration of effort and in enhancing the success of implementation. Actions should focus on improved resource management, disaster preparedness and sustainability in the face of multiple stressors, one of which is climate change1024-1031. One of the key areas of resource management is that of food supply. Although world trade could help satisfy future demand for food in most regions, even under warmer climate scenarios, some regions will experience shortages that trade alone cannot address. For example, various studies show a negative impact of climate change on crop production in Africa. With the help of traditional knowledge, farmers there have proven themselves very adaptable to past changes in climate. However, they need access to relevant knowledge to respond to future changes in variability that may be much larger than those of the past. Furthermore, in subsistence regions such as that of the sub-Sahara, the adaptive capacity of farmers is undermined by poor health, rural unemployment and inadequate community structure. Hence, enhancing adaptive capacity in these regions will also require addressing underlying issues of health and poverty. One common response to resource scarcity is human migration to regions that are perceived to be less stressed. As noted above, governments will need to put into place the institutional and economic infrastructure to engage the stakeholders and people most impacted and facilitate adaptation strategies that consider climate change impacts within the context of other stressors and the framework of local and regional sustainable development1032-1035. Another key management concern is that of natural resources. There are many potential adaptive measures that can be considered, but much more research needs to be undertaken to understand their feasibility or effectiveness. For example, one recent study found that, as expected, fertilizing white spruce stands in the Yukon with nitrogen increased growth rates – but that this enhanced growth stopped as soon as fertilization stopped. Investigators are unsure whether this was due to the inability of soils to retain the nitrogen or due to a concurrent stress due to insect infestations. Surveys also indicate that forest managers in the region, while relatively well informed about risks of climate change, do not as yet explicitly factor those risks into their management strategies. Researchers also caution that Canada’s policies on water management are based on the perception of plentiful supplies, but that both paleo records of past climates and future projections suggest that this is not a sound assumption. Greater effort will be needed to develop portfolios of adaptive strategies for natural resource management that engage both policy makers involved in the planning stages of resource management and the practitioners who implement the operational plans that emerge from such plans. One example of such collaborative effort is the successful dialogue between resource managers and stakeholders in developing a portfolio of adaptive options to address the impacts of climate change on both water supply and demand within the Okanagan region of British Columbia. However, some experts have lamented that, while stakeholders generally look to local, provincial and federal government for help in developing such adaptation strategies, governments do not always share the same desire to consult with stakeholders1036-1041. It is also important to develop adaptive strategies for dealing with the economic impacts of climate extremes and to help capitalize on new opportunities that warmer climates will bring. In permafrost regions, for example, engineering of structures need to both cope with the risk of decaying ground ice and reduce the direct effect that such structures may have on the rate of permafrost decay. In Quebec, agricultural management strategies are needed to ensure optimum selection and/or development of appropriate crop varieties that will help cope with the stress of high temperature events and earlier maturation, and also take advantage of the longer growing seasons associated with warmer climates. Meanwhile, irrigation can help address concerns about increased drought stress. However, surveys of farmers in eastern Ontario indicate that, while many already have in place measures to cope with current weather variability and extremes, these measures are likely to be inadequate for the severity of future climate extremes. Farmers involved in the survey appear to be unaware or unconcerned about these risks. The ski industry in eastern Canada is another example of an economic sub-sector that has already learned to adapt to current challenges of weather variability and extremes, although in an uncoordinated and reactive manner. Related studies that do not consider the large range of additional adaptive options available to the ski industry may have significantly exaggerated the negative imacts924,1042-1045. More fundamental, however, is the concern about the socio-economic well being of communities, particularly those dependent on natural resources. These communities need to deal with the stresses associated with climate change in its various manifestations in conjunction with those arising from other environmental and socio-economic pressures. For example, enhanced UV radiation caused by stratospheric ozone depletion will also have profound impacts on freshwater fish in the Arctic and on the local communities that rely on these. Likewise, communities in British Columbia dependent on forest resources are vulnerable to the consequences of the mountain pine beetle outbreak in addition to a myriad of other factors that affect their local economy. Adaptation strategies need to address the climate change impacts in conjunction with other local factors, some of which add stresses and others which can help mitigate them. In northern and other natural resource dependent communities, the effective use of vulnerability indexes, traditional knowledge and existing social networks are important tools that help to do so. Dialogue with the people is essential. One challenge is the loss of traditional knowledge within the culture of northern people, which is slowly eroding their capacity to adapt796,902,1034,1046-1051. Finally, the projected spread of infectious diseases is also a concern that affects communities on a global scale, but particularly those in northern and developing regions. A key factor in developing adaptive capacity to deal with this is better international cooperation in monitoring the spread of viruses and transport vectors of these diseases. This, in turn, requires effective collaboration between health experts and ecologists1052. REFERENCES Abbreviations for references: BAMS=Bulletin of the American Meteorological Society; CC=Climatic Change; GBC= Global Biogeochemical Cycles; GCB=Global Change Biology; Geophys. Res. Letts. = Geophysical Research Letters; JGR=Journal of Geophysical research; PNAS =Proceedings of the National Academies of Sciences.
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