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The Effects of Global Warming
Over the past century and a halfor so, the earth has seen a significant rise in average global temperatures (see Figure 1). Studies show that average surface temperatures have risen at the rate of approximately 0.1°C/decade, which is significant when compared to estimates of historical values (IPCC, 2001). Regardless of whether this temperature increase is primarily a result anthropogenic causes, such as as emission of greenhouse gases, or natural fluctuations, global warming will have a profound effect upon the oceans and should therefore be of great concern to anyone in charge of managing global fisheries. It is also very likely that global warming will accelerate in the near future due to positive feedback mechanisms, including the lowering of the Earth's albedo due to melting of polar caps (IPCC, 2001). Climate change is quite difficult to monitor, and even more difficult to predict accurately (see Figure 2). Despite this, research on current systems as well as research into past global warming events provides a general idea of what can be expected in future years. Knowledge of these general trends will allow us to better understand the effects and, consequently, better manage fisheries.
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It is also likely that climate change will have severe, direct effects on humans. the human aspects of many fisheries. Sea level rise may threaten many coastal areas. Thermal expansion of seawater alone is expected to cause a rise of between of 0.09 and to 0.37 meters m over the next century (IPCC, 2001). This modest sounding rise is nevertheless enough to threaten many may threaten coastal cities, and infrastructure of the fishing industry in some cases entire island nationsareas. It is also predicted that storms , such as monsoons and hurricanes, may hurricane my increase in number and intensity as a result of global warming (IPCC, 2001). Global warming can affect land-based Flooding and storm surges could also result in damages to fishing infrastructure in locations prone to these disasters. Terrestrial effects of global warming could effect agriculture in certain areas by changing patterns of precipitation. For example, desertification is a major threat in areas such as the southwestern United States, while excessive flooding is the threat in other regions (IPCC 2001). Increased carbon dioxide levels will also alter the changes in timing and intensity of droughts and flooding, as well as the effect of increased carbon dioxide on the growth rates of crops and weeds. In certain environments, changes in the productivity of traditional, land agriculture could lead to a changes in fish demandThere are also likely to be effects on agriculture by sustained changes in temperature and precipitation, such as the desertification of the southwestern United States (IPCC, 2001). A decrease in agricultural yield could increase the demand for fish.
One possible method of reacting to a specific negative effect of climate change - decreasing natural phytoplankton levels and debasing the ocean food chain - is "ocean fertilization" with finely powerdered. This allows high levels of phytoplankton growth in areas deficient in this nutrient (Jones & Young, 1997). There are significant technical problems related to this approach. Also, the large-scale effectiveness of iron fertilization is extremely speculative (Chisholm, Falkowsi, & Cullen, 2002). Hence, we do not advise this method until significantly more research has been conducted.
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