As a result of evidence that human-induced global climate change is already occurring and will continue to affect society over the coming decades, a surge in interest in impact-oriented action is discernable since the beginning of the century, in contrast to efforts centred on prevention (Burton et al., 2002). Frustration over the lack of progress and effectiveness of policy to reduce greenhouse gas emissions has contributed to this shift. Adapting to the changes has consequently emerged as a solution to address the impacts of climate change that are already evident in some regions. However, this course of action has not always been considered relevant within science and policy (Schipper, 2006a; Klein, 2003). Adaptation responds directly to the impacts of the increased concentrations of greenhouse gases in both precautionary and reactive ways, rather than through the preventative approach of limiting the source of the gases (this is known as ‘mitigation’). This avoids the enormous political obstacles facing initiatives to curtail the burning of fossil fuels by factories, transport and other sectors. Adaptation to climate change is considered especially relevant for developing countries, where societies are already struggling to meet the challenges posed by existing climate variability (Yamin et al. 2005; Adger et al., 2003; Handmer, 2003; Kates, 2000; Watson and Ackerman, 2000), and are therefore expected to be the most adversely affected by climate change (McCarthyet al., 2001). The recent Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report makes clear that “adaptation will be necessary to address impacts resulting from the warming which is already unavoidable due to past emissions” (IPCC,complimentary response strategy to mitigation.
The severity of damaging human-induced climate change depends not only on the magnitude of the change but also on the potential for irreversibility. This paper shows that the climate change that takes place due to increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop. Following cessation of emissions, removal of atmospheric carbon dioxide decreases radiative forcing, but is largely compensated by slower loss of heat to the ocean, so that atmospheric temperatures do notdrop significantly for at least 1,000 years. Among illustrative irreversible impacts that should be expected if atmospheric carbon dioxide concentrations increase from current levels near 385 parts per million by volume (ppmv) to a peak of 450–600 ppmv over thecoming century are irreversible dry-season rainfall reductions in several regions comparable to those of the ‘‘dust bowl’’ era and inexorable sea level rise. Thermal expansion of the warming ocean provides a conservative lower limit to irreversible global average sea level rise of at least 0.4 1.0 m if 21st century CO2 concentrations exceed 600 ppmv and 0.6 –1.9 m for peak CO2 concentrations exceeding _1,000 ppmv. Additional contributions from glaciers and ice sheet contributions to future sea level rise are uncertain but may equal or exceed several meters over the next millennium or longer.
Climate change is a serious and urgent issue. There is now an overwhelming body of scientific evidence that human activity is causing global warming, with the main sources of greenhouse gases, in order of global importance, being electricity generation, land-use changes (particularly deforestation), agriculture and transport; the fastest growing sources are transport and electricity.