Аннотация:Correct use of scientific assessment results in decision-makingprocesses requires information about their uncertainties. The evolution ofapproaches for assessing the uncertainty of statements (findings, conclusions) ofIntergovernmental Panel on Climate Change (IPCC) reports is considered.Recommendations of the IPCC guidance notes of 2000 and 2010 on characterizingthe uncertainties are presented. Two approaches for improving uncertaintytreatment are proposed. The first pertains to analyzing independence of quantitativedata used in the estimation of uncertainty in results of their synthesis. The secondpertains to objective assessment of the degree of certainty of qualitative statements.