Accelerated global warming and implications of the IPCC Special Report on 1.5°C

Abstract

In 2018, an IPCC special report on Global Warming of 1.5 ºC is published. This report describes the impacts of global warming of 1.5 °C above pre-industrial levels and related global greenhouse gas emission pathways in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty. Human activities are estimated to have caused approximately 1.0°C of global warming above pre-industrial levels, and global warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate. Climate-related risks for natural and human systems are higher for global warming of 1.5°C than at present, but lower than at 2°C. By 2100, global mean sea level rise is projected to be around 0.1 metre lower with global warming of 1.5°C compared to 2°C and a slower rate of sea level rise enables greater opportunities for adaptation in the human and ecological systems of small islands, low-lying coastal areas and deltas. The probability of a sea-ice-free Arctic Ocean during summer is projected as one per century, while this likelihood is increased to at least one per decade with 2°C global warming. Pathways limiting global warming to 1.5°C with no or limited overshoot would require rapid and far-reaching transitions in energy, land, urban and infrastructure, and industrial systems, which are unprecedented in terms of scale. In model pathways with no or limited overshoot of 1.5°C, global net anthropogenic CO2 emissions decline by about 45% from 2010 levels by 2030, reaching net zero around 2050. All pathways that limit global warming to 1.5°C with limited or no overshoot project the use of carbon dioxide removal (CDR) on the order of 1001000 GtCO2 over the 21st century. However, most current and potential CDR measures could have significant impacts on land, energy, water, or nutrients if deployed at large scale.