Towards a green economy 1 Introduction This chapter describes the modelling exercise
conducted for the entire Green Economy Report (GER) and presents its results. The modelling was to test the hypothesis – which gave rise to this report – that investing in the environment delivers positive macroeconomic results, in addition to improving the environment. The modelling tool used is the Threshold 21 World model (T21-World), which comprises several sectoral models integrated into a global model. The sectoral models are at the core of the modelling exercise supporting the analysis carried out by the authors of the GER. The modelling traces the effects of investing various amounts of GDP in green – as opposed to business-as-usual (BAU) – economic activities in terms of stimulating the economy, improving resource efficiency, lowering carbon intensity, and creating jobs.
The next section describes the key issues that need to be addressed by a modelling framework that tries to quantify the challenges of moving towards a green economy. The third section describes key features of the modelling structure. This is followed by a section describing the assumptions underlying the various scenarios: a BAU scenario with no additional
investment, two BAU scenarios with increased levels of investment, but no change in energy and environmental policies (BAU1 and BAU2), and two green scenarios which combine the higher levels of investment
with improved environmental polices
(G1 and G2). After that, a fifth section describes the results of the various scenarios. This is followed by a short concluding section. Additional technical details are provided in an Annex as well as in the separate Technical Background Material.
It should be noted that all sector chapters in this report have, to a varying extent, made use of the results from the modelling exercise presented here. Although the modelling includes a number of scenarios, the sector chapters generally compare only one green scenario, G2, with the corresponding BAU2 scenario, in addition to describing relevant aspects of the baseline BAU scenario. The G2 scenario is more relevant as it explicitly aims to reduce CO2
emissions sufficiently to achieve an
atmospheric concentration of 450 ppm, as well as a number of other policy targets in the areas of nutrition, fisheries management, reducing deforestation, water availability and waste management.