The idea of a climate club to complement the international regime of the United Nations Framework Convention on Climate Change (UNFCCC) has been discussed in economics for over a decade. In 2015, Nobel economics laureate William Nordhaus proposed that members of such a club should coordinate their emissions trading systems or CO2 taxes among themselves. In addition, they should jointly levy external tariffs on emissions-intensive products from countries that do not use CO2 pricing instruments in order to compensate for any competitive disadvantages for domestic industry.