A standard baseline scenario 2,3 that assumes no policy intervention to limit greenhouse-gas emissions has 10 TW (10 ؋ 10 12 watts) of carbon-emission-free power being produced by the year 2050, equivalent to the power provided by all today's energy sources combined. Here we employ a carbon-cycle/energy model to ¶ Present address: Boeing, Saal Beach, California 90740-7644, USA.

No abstract

Systematic evidence relating to the performance of carbon pricingcarbon taxes and greenhouse gas (GHG) emissions trading systems (ETSs)is sparse. In 2015, 17 ETSs were operational in 55 jurisdictions while 18 jurisdictions collected a carbon tax. The papers in this special thematic section review the performance of many of these instruments over the 2005-2015 period. The performance of existing carbon taxes and GHG ETSs can help policy makers make informed choices about whether to introduce these instruments and to improve their design. The purpose of carbon pricing instruments is to reduce GHG emissions cost effectively. Assessing their performance is difficult because emissions are also affected by other policies and exogenous factors such as economic conditions. Carbon taxes in Europe prior to 2008 and in British Columbia reduced emissions from business-as-usual but actual emissions continued to rise. Since 2008 emissions subject to European carbon taxes have declined, but in most countries, other mitigation policies have probably contributed more to the reductions than the carbon taxes. Emissions subject to ETSs, with the exception of four systems without emissions caps, have declined. The ETSs contributed to the emissions reductions, but their share of the overall reduction is not known. Most tax rates are low relative to levels thought to be needed to achieve climate change objectives. Few jurisdictions regularly adjust their tax rates. All ETSs have accumulated surplus allowances and implemented measures to reduce these surpluses. The largest ETSs now specify annual reductions in their emissions cap several years into the future. Emissions trading system allowance prices are generally lower than the tax rates.Key policy insights . Theoretical discussions usually portray carbon taxes and GHG ETSs as alternatives.In practice, a jurisdiction often implements both instruments to address emissions by different sources. . Designs of ETSs have evolved based on experience shared bilaterally and via dedicated institutions. . Carbon tax designs, in contrast, have hardly evolved and there are no institutions dedicated to sharing experience. . Every jurisdiction with an ETS and/or carbon tax also has other policies that affect its GHG emissions. ARTICLE HISTORYCarbon pricing can be implemented using either of two instrumentsa carbon tax or a GHG emissions trading system (ETS). With a tax, the government sets the tax rate and specifies the sources subject to the tax. The emission reduction achieved depends upon the response of the affected sources to the imposition of the tax. With an ETS the government sets a limit on GHG emissions by specified sources and distributes allowances approximately equal to the limit. 2 Allowances are tradable. Each source must surrender allowances equal to its actual emissions to the government. Emissions cannot exceed the limit, but the compliance cost depends on the market price of allowances.There is an extensive literature on the relative merits of these two instruments (e.g. Partnersh...

No abstract

Agnolucci, P. (2007). The effect of fi nancial constraints, technological progress and long-term contracts on tradable green certifi cates. Energy Policy, 35(6), pp.