W. STERK, H.-J. LUHMANN, F. MERSMANN| HOW MUCH IS 100 BILLION US DOLLARS reduce investment risks. However, here again it is far from trivial to quantify the achieved reduction in returns and the value that accrues to developing countries. 2.2 Potential Revenues from Individual Sources on a Gross and Net Basis Most of the sources are directly or indirectly related to the carbon market. The AGF used three price scenarios as basis for its estimates of the revenue potential: (i) a low-carbon price scenario at US$10-15/t CO 2 -eq; (ii) a medium-carbon price scenario at US$20-25/t CO 2 ­eq; and (iii) a high-carbon price scenario at US$50/t CO 2 -eq. The low and medium price scenarios reflect prices that can be expected from implementation of the emission reduction pledges made under the Copenhagen Accord and the Cancún Agreements. The high scenario reflects prices that could be expected in 2020 if the pledges were strengthened to be consistent with the 2° C target. In addition to assumptions on the carbon price, assump­tions have to be made on what share of total revenue could be made available for international climate fi­nance. If revenues are collected by national rather than international institutions – for example, auctioning of allowances in a national ETS – one may assume that fi­nance ministers and parliaments will want to retain the major share of the revenue for their national budgets. Tables 1 and 2 summarise the AGF estimates for each source of finance, as well as some of the key assump­tions. As noted above, the AGF estimated all public sour­ces on a net basis, while the other sources were estima­ted on both a gross and a net basis. In summary, the AGF concluded that mobilising 100 bil­lion US dollars is»challenging but feasible«. However, most of the assumptions made by the AGF are fairly conservative. First, the AGF focuses its analysis on the medium-price scenario; the high-price scenario is indica­ted only»for illustrative purposes«. However, as the AGF itself notes, only the high-price scenario is consistent with the 2° C target. Table 1: AGF Calculation of Public Sources Public sources Net(billion US dollars) Auctioning of allowances(2-10 % of estimated auction revenues dedicated to international climate finance) Levies on offsets(levy of 2-10 % on offset transactions) International maritime transport(no net incidence on developing countries, 25-50 % dedicated to international climate finance) International aviation(no net incidence on developing countries, 25-50 % dedicated to international climate finance) Carbon tax(international tax, 100 % for international climate finance) Low CO 2 price Medium CO 2 price High CO 2 price 2-8 8-38 14-70 0-1 1-5 3-15 2-6 4-9 8-19 1-2 2-3 3-6 10 Wires charge(100 % for international climate finance) 5 Removal of fossil fuel subsidies(100 % for international climate finance) Redirection of fossil fuel royalties(100 % for international climate finance) Financial transaction taxes(no net incidence on developing countries, 25-50 % dedicated to international climate finance) Direct budget contributions(proposal by G77 to dedicate 0.5-1 % of Annex I GDP) 3-8 10 2-27 200-400 5