Figure 12.3 | Conceptual illustration of representative climatic impact-driver thresholds showing how graduating thresholds affect successive sectoral assets and lead to potentially more acute hazards as conditions become more extreme (exact values are not shown as these must be tailored to reflect diverse vulnerabilities of regional assets). Representative threshold definitions (T = instantaneous temperature; T= mean temperature): Cities and Infrastructures: Ttrans= temperature at which energy transmission lines efficiency reduced; Taircraft = temperature at which aircraft become weight-restricted for takeoff; Thotroads= temperature above which roads begin to warp; Tstream= temperature at which streams are not capable of adequately cooling thermal plants; CDDmin= minimum temperature for calculating cooling degree days; HDDmax= maximum temperature for calculating heating degree days; Tice= temperature at which ice threatens transportation; Tpermafrost = mean seasonal temperature above which permafrost thaws at critical depths; Tcoldroads= temperature below which road asphalt performance suffers. Health: Tdeadly= temperature above which prolonged exposure may be deadly (often combined with humidity for heat indices); Tsevere= temperature above which prolonged exposure may cause elevated morbidity; Tblooms= mean temperature for harmful algal or cyanobacteria blooms; Tdanger= level of dangerous cold temperatures (often combined with wind for chill indices); Toverwinter= temperature below which disease vector species cannot survive winter. Ecosystems(CID indices for air and ocean temperature): Thotlim and Tcoldlim= limiting hot and cold temperatures for a given species range; Tfrost = frost threshold; Tmax and Tmin= maximum and minimum suitable annual mean temperatures for a given species; Tcrit = critical temperature above which a given species is stressed. Agriculture: Thotlim= temperature above which a crop or livestock species dies; Thotpest = maximum (or ‘lethal’) temperature above which an agricultural pest/disease/weed cannot survive; Tcrit = temperature at which productivity for a given crop is depressed; Topt = optimal mean temperature for a given plant’s productivity; GDDmin= threshold temperature for growing degree days determining plant development; Tchill= temperature below which chilling units are accumulated; Tfrost = temperature below which frost occurs; Thfrost = temperature below which a hard frost threatens crops or livestock; Tcoldpest = minimum winter temperature below which a given agricultural pest cannot survive; Tcoldlim= minimum temperature below which a given crop cannot survive.