Below is a potted cut and paste job, I recommend going to: http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1602.html for the full (and not long) paper
The combined effect of the initiatives can be quite substantial: a reduction of roughly 10 Gt CO2e below business as usual by 2020, plus the effect of enhanced reductions in air-pollutant emissions. This can be compared to the gap of around 12 Gt CO2e between business as usual and what would be necessary for the 2 °C limit.
Action by an individual citizen, a municipality or even a large multinational company may be considered 'a drop in the ocean'. Even individual actions by large companies or big cities will rarely have an impact of more than a few megatonnes of carbon dioxide equivalent. However, being part of a larger coalition that has the potential to completely bridge the entire emissions gap will make it much more attractive to participate in and take action. To this end, it is necessary that globally leading organizations in the world of business, governments and non-governmental organizations (NGOs) participate. They need to be part of a coalition that together provides leadership in bridging the gap. Therefore, the key to the success of the wedging-the-gap approach is forming and sustaining this coalition.
The successes of the coalition of initiatives have to be fed back into the UNFCCC process and have to have an impact on national government pledges. Otherwise national governments may feel released from the pressure to implement and strengthen their pledge, as they could rely on the success of action elsewhere.
Top 1,000 companies' emission reductions. An association such as the World Business Council for Sustainable Development could lead 30% of the top 1,000 companies to reduce energy-related emissions 10% below business as usual by 2020 and all companies to reduce their non-carbon dioxide greenhouse-gas emissions by 50%. Impact in 2020: up to 0.7 Gt CO2e.
Supply-chain emission reductions. An organization such as the Consumer Goods Forum could stimulate 30% of companies to require their supply chains to reduce emissions 10% below business as usual by 2020. Impact in 2020: up to 0.2 Gt CO2e.
Green financial institutions. finance initiative of the United Nations Environment Programme (UNEP-FI). could lead the 20 largest banks to reduce the carbon footprint of 10% of their assets by 80%. Impact in 2020: up to 0.4 Gt CO2e.
Voluntary-offset companies. A coalition between an organization with convening power, for example, UNEP, and offset providers could motivate 20% of the companies in the light industry and commercial sector to calculate their greenhouse-gas emissions, apply emission-reduction measures and offset the remaining emissions (retiring the purchased credits). It is ensured that offset projects really reduce emissions by using the 'gold standard' for offset projects or another comparable mechanism. Governments could provide incentives by giving tax credits for offsetting, similar to those commonly given for charitable donations. Impact by 2020: up to 2.0 Gt CO2e.
Voluntary-offset consumers. Environmental NGOs could motivate 10% of the 20% of richest individuals to offset their personal emissions from electricity use, heating and transport at cost to them of around US$200 per year. Impact in 2020: up to 1.6 Gt CO2e.
Major cities initiative. Groups such as the C40 or ICLEI — Local Governments for Sustainability could lead the 40 cities in C40 or an equivalent sample to reduce emissions 20% below business as usual by 2020, building on the thousands of emission-reduction activities already implemented by the C40 cities. Impact in 2020: up to 0.7 Gt CO2e.
Subnational governments. Following the example set by states such as California, these ambitious US states and Canadian provinces could accept an emission-reduction target of 15–20% below business as usual by 2020, as some states already have. Impact in 2020: up to 0.6 Gt CO2e.
Building heating and cooling. The UN Secretary General's Sustainable Energy for All Initiative could bring together the relevant players to realize 30% of the full reduction potential for 2020. Impact in 2020: up to 0.6 Gt CO2e.
Ban of incandescent lamps. target to globally ban incandescent lamps by 2016. Impact in 2020: up to 0.2 Gt CO2e.
Electric appliances. international labelling schemes and standards could drive use of the most energy-efficient appliances on the market. Impact in 2020: up to 0.6 Gt CO2e.
Cars and trucks. agree to save one additional litre per 100 km globally by 2020 for cars, and equivalent reductions for trucks. Impact in 2020: up to 0.7 Gt CO2e.
Boost solar photovoltaic energy. A coalition of progressive governments and producers could remove barriers by introducing good grid access and net metering rules, paving the way to add another 1,600 GW by 2020 (growth consistent with recent years). Impact in 2020: up to 1.4 Gt CO2e.
Wind energy. The Global Wind Energy Council could foster the global introduction of arrangements that lead to risk reduction for investments in wind energy, with, for example, grid access and guarantees. This could lead to an installation of 1,070 GW by 2020, which is 650 GW over a reference scenario. Impact in 2020: up to 1.2 Gt CO2e.
Access to energy through low-emission options. The UN Secretary General's Sustainable Energy for All Initiative could ensure that all people without access to electricity get access through low-emission options. Impact in 2020: up to 0.4 Gt CO2e.
Phasing-out subsidies for fossil fuels. phase-out half of all fossil-fuel subsidies. Impact in 2020: up to 0.9 Gt CO2e.
International aviation and maritime transport. capture half of the technical mitigation potential. Impact in 2020: up to 0.2 Gt CO2e.
Fluorinated gases (hydrofluorocarbons, perflourocarbons, SF6). meeting half of the technical mitigation potential. Impact in 2020: up to 0.3 Gt CO2e.
Reduce deforestation. halving global deforestation by 2020. Impact in 2020: up to 1.8 Gt CO2e.
Agriculture. The International Federation of Agricultural Producers could help to realize 30% of the technical mitigation potential. Impact in 2020: up to 0.8 Gt CO2e.
Enhanced reduction of air pollutants. Reduction of classic air pollutants including black carbon has been pursued for years owing to positive impacts on health and local air quality. UNEP's Climate and Clean Air Coalition To Reduce Short-Lived Climate Pollutants already has significant political momentum and could realize half of the technical mitigation potential. Impact in 2020: a reduction in radiative forcing impact equivalent to an emission reduction of greenhouse gases in the order of 1 Gt CO2e, but outside of the definition of the gap.
Efficient cook-stoves. Cooking in rural areas is a source of carbon dioxide emissions. Furthermore, there are emissions of black carbon, which also leads to global warming. Replacing these cook-stoves would also significantly increase local air quality and reduce pressure on forests from fuel-wood demand. A global development organization such as the UN Development Programme could take the lead in scaling-up the many already existing programmes to eventually replace half of the existing cook-stoves. Impact in 2020: a reduction in radiative forcing impact equivalent to an emission reduction of greenhouse gases of up to 0.6 Gt CO2e, included in the effect of the above initiative and outside of the definition of the gap.