Abstract

The various CO2 concentration stabilization profiles used in Intergovernmental Panel on Climate Change (IPCC) analyses are described, and their methods of construction explained. Padé approximant coefficients are given to allow readers to recalculate the profiles precisely. Forward and inverse initialization strategies are discussed, and industrial emissions requirements for the “S” and “WRE” profiles are compared and evaluated. Details of the post-1990 carbon budget breakdown for the specific case of WRE550 are given. Uncertainties in the industrial emissions required for stabilization following any given profile are quantified. Uncertainties considered are those resulting from the effects of: CO2 fertilization formulation (logarithmic versus rectangular hyperbolic); the prescribed future “history” of net deforestation; terrestrial sink specification and the IPCC restriction of this sink to CO2 fertilization only; and ocean flux uncertainties. Sink specification is the greatest source of uncertainty, leading to potential errors in implied emissions of up to ±2 Gt C/yr for WRE550. Errors of this magnitude are equivalent to a misspecification of the stabilization level of approximately ±50 ppmv.

Introduction

The stabilization of future atmospheric CO2 concentration is one of the primary aims of the United Nations Framework Convention on Climate Change (UNFCCC). Article 2 of this convention gives the following objective: “To achieve stabilization of greenhouse gas concentrations … at a level that would prevent dangerous anthropogenic interference with the climate system….”