Social and environmental impacts of climate change: In the absence of mitigation, will we be able to adapt?

peer reviewedWarming of the climate system is unequivocal, as it is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level. Observational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases. Other effects of regional climate changes on natural and human environments are emerging, although many are difficult to discern due to adaptation and non-climatic drivers. Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gases concentrations. In this framework, sea level rise is virtually certain and increasing frequency of heat waves and heavy precipitation events is very likely during the 21st century. This will impact ecosystems, food security, coastal areas, human health, water availability, and economies. Since current (2000-2010) CO2 emissions are near the worst Intergovernmental Panel on Climate Change (IPCC) scenario (A1F1) projecting a global average surface warming of 2.4 to 6.4°C and a sea level rise of 26 to 59 cm (excluding any future rapid dynamical change in ice flow) at 2090-2099 relative to 1990-1999. And since it is very likely that the international response will be very weak in the near future (as it has been in the past), giving no chance to a second phase to the Kyoto Protocol that expires in 2012. We thus have to accept that climate change mitigation is behind us and that only adaptation to global warming is the response to reduce vulnerability of natural and human systems to climate change effects. However, we know that in the absence of climate change effects, the vulnerability of natural and human systems is extremely high, especially due to the mismanagement of natural resources, the lack of land use planning and the nonexistence of policies focused on natural hazard management