IPCC AR5 2013-2014 Danger and Risk
Danger as in the 1992 UN climate convention ‘dangerous climate interference’ is quantified by risk.
Though AR5 goes further than past assessments in indicating what dangerous climate interference (DAI) would be, it makes a point not to conclude or recommend what DAI would be in terms of the goal of and defined by the 1992 UN Framework Convention on Climate Change.
The IPCC since the 3rd 2001 assessment has said (incorrectly) that science cannot determine what DAI is. The 2001 assessment said danger is a ‘value judgment’ that science cannot make. The IPCC (incorrectly) says this can only be determined by policy makers.
Though the AR5 on risk is useful information, what AR5 calls risks are in fact probabilities at various degrees of warming. They do not account for the magnitude of the impacts, though IPCC has recognized the standard precautionary risk formula of risk is the product of probability times magnitude.
For example risks of such tipping points become moderate between 0 to 1° C (0 to 1.6C) due to early warning signs that both coral reef and Arctic Systems are already experiencing irreversible regime shifts. This is an extreme risk – not moderate. Probability is moderate. Magnitude is extreme making risk of irreversible loss of coral reefs and Arctic systems extreme at 1.6C, to which we are absolutely committed.
AR5 WG 1 TS 12.5.4.1 Background
The concept of stabilization is strongly linked to the ultimate objective of the UNFCCC, which is “to achieve […] stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.” Recent policy discussions focused on a global temperature increase, rather than on greenhouse gas concentrations. The most prominent target currently discussed is the 2°C temperature target, i.e., to limit global temperature increase relative to preindustrial times to below 2°C. The 2°C target has been used first by the European Union as a policy target in 1996 but can be traced further back (Jaeger and Jaeger, 2010; Randalls, 2010). Climate impacts however are geographically diverse (Joshi et al., 2011) and sector specific, and no objective threshold defines when dangerous interference is reached. Some changes may be delayed or irreversible, and some impacts are likely to be beneficial. It is thus not possible to define a single critical threshold without value judgments and without assumptions on how to aggregate current and future costs and benefits. Targets other than 2°C have been proposed (e.g., 1.5°C global warming relative to preindustrial), or targets based on CO2 concentration levels, e.g., 350 ppm in (Hansen et al., 2008). The rate of change may also be important (e.g., for adaptation).
This section does not advocate or defend any threshold, nor does it judge the economic or political feasibility of such goals, but simply assesses the implications of different illustrative climate targets on allowed carbon emissions, based on our current understanding of climate and carbon cycle feedbacks.
Key risks across sectors and regions.
Box SPM 4
Human interference with the climate system
Human interference with the climate system is occurring, yet determining whether this interference is dangerous as are relevant to Article 2 of the UNFCCC involves both risk assessment and value judgments. This report assesses risks across context and through time providing a basis for value judgments about the level of climate change at which a risks become dangerous.
Five integrated Reasons For Concern (RFCs) provide a framework for summarising key risks across sectors and regions. First identified in the IPCC third assessment report the reasons for concern illustrate the implications of warming and adaptation limits for people economies and ecosystems. They provide one starting point for evaluating dangerous anthropogenic interference with the climate system. An updated assessment of risks for each reason for concern is presented below and inbox SPM for figure 1. All temperature changes are given relative to 1986 to 2005 (recent)
Warming from 1850 is 0.6°C higher and added in brackets- also the range is added next to the RFC.
1. Unique and threatened systems(>1.6C- severe 2.6C).Some unique and threatened systems, including ecosystems and cultures, are at risk from climate change at recent temperatures. The number of such systems at risk of severe consequences increases at a warming of 1.0° C (1.6C). Many species and systems with limited adaptive capacity are subject to very high risks at a warming of 2° C (2.6C), particularly Arctic sea ice systems and coral reefs.
2. Extreme weather events(moderate 0.8C - high1.6C). Climate change related risks from extreme events such as heat waves extreme precipitation and coastal flooding are moderateat a recent temperatures and high at 1° C (1.6C) warming.
3. Distribution of impacts(moderate 0.8- high 2.6C). Risks for disproportionately affected people and communities are generally greatest in low latitude less-developed areas and are moderate at recent temperatures because of regionally differentiated climate change impacts on food production. Developed countries also have highly vulnerable populations. Based on risks for regional crop production in water resources in some countries risks become high for warming above 2° C (2.6C).
4. Global aggregate impact(moderate 1.6C –high 3.6C). Risks to the overall global economy and earth biodiversity become moderate for warming between 1 to 2° C (1.6C to 2.6C)and high around 3° C (3.6C) reflecting warming dependent increases in risks of economic impacts and extensive biodiversity loss with concomitant loss of ecosystem services
5. Large scale singular event (moderate 0.8C – high 1.6C). With increasing warming some physical systems or ecosystems may be at risk of abrupt and drastic changes. Risks of such tipping pointsbecome moderate between 0 to 1° C (0 to 1.6C)due to early warning signs that both coral reef and Arctic Systems are already experiencing irreversible regime shifts. Risks become high between 1 to 4° C (1.6C to 4.6C) with a disproportionate increase in risks as temperature increases between 1 to 2° C (1.6C to 2.6C)due to the potential for, commitment to a large and irreversible sea level rise from ice sheet loss.
Key risks that spanned sectors and regions include the following each of which contributes to one or more reasons for concern
1. Risk of death injury and disrupted livelihoods in low-lying coastal zones and small island developing states due to sea level rise coastal flooding and storm surges (RFC 1-2)
2. Risk of food insecurity linked to warming drought and precipitation variability particularly for poorer populations(RFC 2-4).
3. Risk of severe harm for large urban populations due to inland flooding.(RFC 2 and4)
4. Risk of loss of a rural rural livelihoods and income due to insufficient access to drinking and irrigation water and reduced agricultural productivity particularly for farmers and pastoralists with minimal capital in semi arid regions. (RFC 2 and 3)
5. Systemic risks due to extreme events leading to a breakdown of infrastructure networks and critical services. (RFC 2-4)
6. Risk of loss of Marine ecosystems and the services they provide full coastal livelihoods especially for fishing communities in the tropics and the Arctic. (RFC 1-5) 7 risk of loss of terrestrial ecosystems and the services they provide for terrestrial livelihoods. (RFC 1,2, and 3) 8. Risk of mortality and morbidity and other harms during periods of extreme heat particularly for vulnerable urban populations