Advancing national climate change risk assessment to deliver national adaptation plans

A wide range of climate vulnerability and risk assessments have been implemented using different approaches at different scales, some with a broad multi-sectoral scope and others focused on single risks or sectors. This paper describes the novel approach to vulnerability and risk assessment which was designed and put into practice in the United Kingdom's Second Climate Change Risk Assessment (CCRA2) so as to build upon its earlier assessment (CCRA1). First, we summarize and critique the CCRA1 approach, and second describe the steps taken in the CCRA2 approach in detail, providing examples of how each was applied in practice. Novel elements of the approach include assessment of both present day and future vulnerability, a focus on the urgency of adaptation action, and a structure focused around systems of receptors rather than conventional sectors. Both stakeholders and reviewers generally regarded the approach as successful in providing advice on current risks and future opportunities to the UK from climate change, and the fulfilment of statutory duty. The need for a well-supported and open suite of impact indicators going forward is highlighted

Supplementary Material from The impact of Earth system feedbacks on carbon budgets and climate response

A number of studies have examined the size of the allowable global cumulative carbon budget compatible with limiting twenty-first century global average temperature rise to below 2°C and below 1.5°C relative to pre-industrial levels. These estimates of cumulative emissions have a number of uncertainties including those associated with the climate sensitivity and the global carbon cycle. Although the IPCC fifth assessment report contained information on a range of Earth system feedbacks, such as carbon released by thawing of permafrost or methane production by wetlands as a result of climate change, the impact of many of these Earth system processes on the allowable carbon budgets remains to be quantified. Here, we make initial estimates to show that the combined impact from typically unrepresented Earth system processes may be important for the achievability of limiting warming to 1.5°C or 2°C above pre-industrial levels. The size of the effects range up to around a 350 GtCO₂ budget reduction for a 1.5°C warming limit and around a 500 GtCO₂ reduction for achieving a warming limit of 2°C. Median estimates for the extra Earth system forcing lead to around 100 GtCO₂ and 150 GtCO₂, respectively, for the two warming limits. Our estimates are equivalent to several years of anthropogenic carbon dioxide emissions at present rates. In addition to the likely reduction of the allowable global carbon budgets, the extra feedbacks also bring forward the date at which a given warming threshold is likely to be exceeded for a particular emission pathway.This article is part of the theme issue ‘The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels’

ESM_RW2 from Advancing national climate change risk assessment to deliver national adaptation plans

Supplementary Material: Worked example and information about UKCP0