Climate Change

The term climate change refers to increases in global mean surface temperatures brought about by human activity. It is considered an issue of global importance because the rise in temperature and the environmental consequences this might engender are transboundary—they do not respect the boundaries demarcated by the nation-state. It is a complex governance issue, especially because the nature and extent of the problem are contested.

Global warming is a natural phenomenon. Atmospheric gases—carbon dioxide, methane, and nitrous oxide, primarily—absorb infrared radiation, which is reflected from the Earth's surface as heat. This process is often labeled the greenhouse effect. The sources of greenhouse gases (GHGs) are varied. Carbon dioxide emissions arise primarily from the burning of fossil fuels. Methane is produced by agricultural processes, particularly rice cultivation and livestock. Nitrous oxides come from biomass burning, fertilizer use, and fossil fuel combustion. Without the greenhouse effect, average global temperatures would be considerably cooler than they are now. Concern arises when the effect is enhanced by increased concentrations of GHGs.

The atmospheric concentrations of carbon dioxide have increased by thirty-one percent since preindustrial times (the mid-1700s). About three-quarters of the increase is from fossil fuel burning, the rest from changes in land use, especially deforestation. These changes are linked to abnormal increases in global temperatures. Average surface temperatures could increase by as much as 1 degree Celsius (1.8 degrees Fahrenheit) by 2030 and by anything between 1.4 degrees Celsius (2.5 degrees Fahrenheit) and 5.8 degrees Celsius (10.4 degrees Fahrenheit) by 2100 (against a 1990 baseline). However, some scientists question whether the current temperature peaks merely represent the Earth's natural cycle of temperature peaks and troughs. Others rejoin that it is the rate and degree of contemporary change that is cause for concern.

The foreseen impact of climate change is disputed. Predicted impacts include rises in sea levels, due to [Page 98]the melting of glaciers, and an increase in the frequency and intensity of extreme weather conditions. Coastal areas could be inundated, possibly displacing up to one billion people and affecting up to one-third of the world's croplands. However, predictions vary and scientists remain uncertain about how to precisely model the relative contribution of gases, how to identify the threshold level for concentrations, and whether, when that threshold level is reached, the inherent resilience of the climate system will be overwhelmed. Nonetheless, there is a high degree of consensus in the climatological community that climate change is happening and will have environmental implications, even if the extent of such implications remains contested.