Forceringsdata

Forceringsdata, or forcing data, are quantified contributions to the Earth's energy balance caused by external drivers of climate. They are typically expressed as time series of the global mean net radiative forcing at the top of the atmosphere, in watts per square meter (W/m^2), relative to a pre-industrial baseline. Forcing data distinguish anthropogenic drivers from natural variability and are used to diagnose past climate change and to drive climate projections.

The main components include well-mixed greenhouse gases (CO2, CH4, N2O, and fluorinated gases), aerosols and their indirect effects (sulfates, black carbon, organic aerosols), tropospheric and stratospheric ozone changes, changes in land use, solar irradiance variations, and volcanic aerosols. Some definitions also separate instantaneous radiative forcing from effective radiative forcing, which accounts for rapid atmospheric adjustments.

Data sources and methods: forcing time series are produced from a combination of direct atmospheric observations (gas concentrations, aerosol properties), radiative transfer calculations, and climate-model output. They are compiled and standardized in datasets used by IPCC assessment reports, CMIP/ESGF archives, and national agencies. Historical forcings cover the industrial era to present; future forcings come from scenario runs and policy projections.

Applications and interpretation: forcing data are used in energy balance models, attribution studies, and to interpret and compare CMIP simulations. They help separate drivers of warming, quantify sensitivity, and explore scenarios.

Limitations: uncertainties remain large for aerosol forcing and indirect effects, and there are differences between instantaneous forcing and effective forcing. Volcanic and solar drivers introduce short-term variability and regional differences that complicate attribution.