Risks from global climate change and the Paris agreement

Abstract

The objectives of the Paris Agreement (PA) include limiting the increase in the global average temperature to well below 2 °C ("the 2 °C goal") and pursuing efforts to limit the increase to 1.5 °C ("the 1.5 °C goal"). The purpose of this chapter is to provide an overview of the relevant scientific knowledge on the risks from climate change corresponding to different levels of mitigation efforts, including the two longterm goals in the PA, as well as the expected consequences of extending the Intended Nationally Determined Contributions (INDCs) without strengthening them. According to figures summarizing risks from climate change in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC-AR5), if the global temperature increase could be limited to below 1.5 °C above the preindustrial level, this would reduce the risks from climate change as evaluated from several perspectives. However, some of the risks (such as the effects on unique and threatened systems and the risks from extreme events) would still be considerable even at 1-2 °C above the preindustrial level. Even with a similar degree of climate change, the levels of risk could differ under different degrees of exposure and/or vulnerability. To increase the accuracy of assessments of global climate risks for different temperature increases, explicit consideration of future changes in exposure and vulnerability will be necessary. Internationally coordinated development of new socioeconomic scenarios (Shared Socioeconomic Pathways, SSPs) is expected to promote such studies for the next round of the IPCC report.