Human influences and uncertainty

Objective: Explain anthropogenic forcing and natural forcing, distinguish their meanings, and apply them to a described case.

Anthropogenic forcing: Human activities alter climate drivers, including greenhouse gases, aerosols, and land use. Natural forcing: Volcanic activity and solar variation can influence climate without human initiation. Attribution compares observations with physically expected responses to possible drivers. Human influences include greenhouse gases, aerosols, and land-use change, while natural influences include volcanism and solar variation. Different drivers can leave different patterns over space, altitude, and time. Climate models test these relationships and explore futures under specified assumptions. Uncertainty about a regional detail does not imply equal uncertainty about every part of the climate system. Application: Fossil-fuel combustion increases atmospheric carbon dioxide. This most directly illustrates anthropogenic forcing. A major eruption temporarily changes atmospheric aerosol loading. This most directly illustrates natural forcing.

Objective: Explain attribution and climate model, distinguish their meanings, and apply them to a described case.

Attribution: Attribution evaluates contributions of different causes to observed climate changes. Climate model: A climate model represents physical processes to investigate system behavior and possible changes. Attribution compares observations with physically expected responses to possible drivers. Human influences include greenhouse gases, aerosols, and land-use change, while natural influences include volcanism and solar variation. Different drivers can leave different patterns over space, altitude, and time. Climate models test these relationships and explore futures under specified assumptions. Uncertainty about a regional detail does not imply equal uncertainty about every part of the climate system. Application: Observed patterns are compared with simulations including different forcings. This most directly illustrates attribution. A simulation calculates interactions among air, ocean, and land. This most directly illustrates climate model.

Objective: Explain scenario versus prediction and risk and uncertainty, distinguish their meanings, and apply them to a described case.

Scenario versus prediction: A scenario explores outcomes under specified assumptions rather than guaranteeing one future pathway. Risk and uncertainty: Uncertainty ranges inform climate risk assessment rather than proving an absence of risk. Attribution compares observations with physically expected responses to possible drivers. Human influences include greenhouse gases, aerosols, and land-use change, while natural influences include volcanism and solar variation. Different drivers can leave different patterns over space, altitude, and time. Climate models test these relationships and explore futures under specified assumptions. Uncertainty about a regional detail does not imply equal uncertainty about every part of the climate system. Application: Different emissions assumptions produce different projected warming ranges. This most directly illustrates scenario versus prediction. A planner considers a range of possible coastal flood levels. This most directly illustrates risk and uncertainty.