Narrowing pathways to a sustainable future

At the United Nations Framework Convention on Climate Change (UNFCCC) Conference of the Parties in Copenhagen in 2009, the Alliance of Small Island States, supported by African countries, called for a temperature target of 1.5°C above the preindustrial level, as opposed to the more broadly accepted 2°C limit, as the basis for a global multilateral climate agreement. A subsequent UNFCCC-established review concluded that 2°C of warming cannot be considered safe and that less warming would be preferable (1). The Paris Agreement, adopted in December 2015, formally recognized this notion in its stated aims to hold the increase to well below 2°C and to pursue efforts to limit it to 1.5°C above preindustrial levels (2). On page 791 of this issue, Warren et al. (3) provide a detailed analysis of the avoided risk to species’ geographic ranges if a 1.5°C rather than a 2°C target is attained.

By Guy Midgley

May 16th, 2018

The projected effect on insects, vertebrates, and plants of limiting global warming to 1.5°C rather than 2°C

In the Paris Agreement on Climate Change, the United Nations is pursuing efforts to limit global warming to 1.5°C, whereas earlier aspirations focused on a 2°C limit. With current pledges, corresponding to ~3.2°C warming, climatically determined geographic range losses of >50% are projected in ~49% of insects, 44% of plants, and 26% of vertebrates. At 2°C, this falls to 18% of insects, 16% of plants, and 8% of vertebrates and at 1.5°C, to 6% of insects, 8% of plants, and 4% of vertebrates. When warming is limited to 1.5°C as compared with 2°C, numbers of species projected to lose >50% of their range are reduced by ~66% in insects and by ~50% in plants and vertebrates.

By R. Warren, et al.

May 16th, 2018