For this RFC, the transition from undetectable to moderate risk to global aggregate impacts is assessed with medium confidence to occur between 1.0°℃  and 1.5℃  with a median judgement of transition at 1.3ºC, based on evidence of a combination of economic consequences, widespread impacts to climate- sensitive livelihoods, changes in biomes, and loss of terrestrial and marine biodiversity. The start of the transition from undetectable to moderate risk is located at recent temperatures based on observed impacts to biodiversity . Experts noted aggregate impacts on biodiversity are detectable, with damages that have had global significance . Consistent with the start of this transition at 1ºC, a similar elicitation conducted in Chapter 2 assessed that risks to biodiversity globally have already transitioned to a moderate level with 1°℃ warming, while risks of widespread tree mortality are already moderate with 0.9℃ warming and moderate risks of ecosystem structure change began with warming of 0.5ºC . Human-induced warming has slowed growth of agricultural productivity over the past 50 years in mid- and low latitudes . Although there is not yet strong evidence of attributable loss of life and livelihoods at the global level , experts found that regional evidence of such observed impacts was still relevant to defining the beginning of the transition . Informing the median value and upper bound of the transition to moderate risk, empirical studies and scenario analyses have found that regions with high dependence on climate-sensitive livelihoods like agriculture, fisheries and forestry would be severely impacted even at low levels of warming under conditions of low adaptation .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report