Article 2 of the UNFCCC specifies that the aim of the convention is the “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system”. Limiting global mean warming below 2°C increase above pre-industrial levels has been widely accepted as a global goal in this context. However, many vulnerable countries, particularly Small Island Developing States and Least Developed Countries, have questioned whether this limit is sufficient to protect their interests, and as a consequence there is an international process underway to evaluate risks and damages at different levels of warming, including 1.5°C and 2°C.
Studies of current and expected future impacts of climate change suggest that significant negative impacts, relevant to Article 2 of the
UNFCCC may be felt at lower levels of warming than 2°C. Within the UNFCCC there is a formal process reviewing the 2° limit, and examining the possibility of changing it towards 1.5°C.
At present there is a gap in the scientific literature and methods to rigorously and qualitatively assess differential impacts at these levels of warming. Here we present a framework that allows for a differentiation of regional changes in climate impacts at different levels of global mean temperature (GMT) increase, focusing on the differences between 1.5°C and 2°C. Based on data from the CMIP5 archive as well as output from the ISIMIP project, we assess the climate impact projections for the 26 world regions used in the IPCC SREX report. We show results for several extreme event indices as well as projections of water availability and agricultural yields.
Furthermore, we are able to test for statistical significance of changes in climate impact projections between the different warming levels across the model ensemble.
As climate impacts are not necessarily linear, it is important to understand whether a significant shift in the magnitude of impacts may occur between the different temperature levels and little attention has been given to such a shift at lower levels of warming. Furthermore, the consequences of average global temperature increase are not linearly distributed across regions. A differentiation of the spatial manifestation of change is therefore of high relevance for regional planning, in order to develop suitable coping strategies and adaptation options, as well as to inform decisions about the appropriate long-term global temperature goal.
Our Common Future under Climate Change is the largest conference of the scientific community ahead of the climate summit COP21 in Paris in December. 2000 scientists will meet to address key issues concerning climate change in the broader context of global change and to discuss solutions for both mitigation and adaptation issues.