On summing the components of radiative forcing of climate change

Radiative forcing is a useful concept in determining the potential influence of a particular mechanism of climate change. However, due to the increased number of forcing agents identified over the past decade, the total radiative forcing is difficult to assess. By assigning a range of probability distribution functions to the individual radiative forcings and using a Monte-Carlo approach, we estimate the total radiative forcing since pre-industrial times including all quantitative radiative forcing estimates to date. The resulting total radiative forcing has a 75-97% probability of being positive (or similarly a 3-25% probability of being negative), with mean radiative forcing ranging from + 0.68 to + 1.34 W m(-2), and median radiative forcing ranging from + 0.94 to + 1.39 W m(-2).