From a risk perspective the most important in the new IPCC reports are numbers that are not included, i.e > 4 °C (Paper)
/Role: author
Summary
GCF welcomes the new AR5 summary for policy makers (SPM) from WGII on Impacts, Adaptation, and vulnerability, and from WGIII on Mitigation as scientifically indisputable and therefore incredibly robust reports that clearly show how serious the impacts for humanity would be already at 2 °C warming, and the devastating impacts at a 4 °C warming. They furthermore clearly show the urgency for global concerted collaboration in order to ensure a world transition to a low-carbon world economy by 2050, only 36 years away.
GCF in particular welcomes that WGII and WGIII emphasise that “assessment of the widest possible range of potential impacts, including low-probability outcomes with large consequences, is central to understanding the benefits and tradeoffs of alternative risk management actions”1, and that “risks associated with the full range of outcomes are relevant to the assessment of mitigation” 2.
While WGII clearly state the need to assess low-probability high-impact outcomes there is no information included about impacts beyond a 4 °C warming. This is unfortunate as the WGI report showed that already 450 ppm concentration can result in more than a 4 °C warming. Similarly, WGIII emphasizes the necessity to consider risks associated with extreme climate change and in particular low probability high impact “tipping points” that could trigger new climate regimes