Climate risks: why each half-degree matters

Human activities are estimated to have caused approximately 1°C of global warming above pre-industrial levels and the effects on natural and human systems are already visible. At the current pace of increase of 0.2°C per decade, global warming is expected to reach 1.5°C between 2030 and 2050. The only way to stabilise global warming over multi-decade timescales is to reach and sustain net zero global anthropogenic carbon dioxide emissions and to rapidly reduce emissions of other greenhouse gases such as methane. The Intergovernmental Panel on Climate Change Special Report on global warming of 1.5°C, published in October 2018, assesses current knowledge of the climate-induced impacts and risks for natural and human systems, especially those caused by global warming of 1.5°C and 2°C above pre-industrial levels. The report concludes that the risks are higher than at present for global warming of 1.5°C, but lower than for warming of 2°C. They also depend on the magnitude and rate of warming, the geographical region, levels of development and vulnerability, and on the choices and implementation of adaptation and mitigation options.