International efforts to avoid dangerous climate change have historically focused on reducing energy-related CO2 emissions from countries with either the largest economies (e.g., the EU and the U.S.) and/or the largest populations (e.g., China and India). However, in recent years, emissions have surged among a different, much less-examined group of countries, raising concerns that a next generation of high-emitting economies will obviate current mitigation targets. Compounding the limited analyses of these emerging emitters, the long-term effects of the COVID-19 pandemic on economic activity and energy systems remain unclear. Here, we analyze the trends and drivers of emissions in each of the 59 countries where emissions 2010-2018 grew faster than the global average (excluding China and India), and then project their emissions under a range of pandemic recovery and longer-term energy scenarios. Although future emissions diverge considerably depending on responses to COVID and subsequent pathways, we find that emissions from these countries combined nonetheless reach 5.4 to 6.6 Gt CO2 by 2040 in all our scenarios—substantially in excess of emissions from these regions in published scenarios that successfully limit global warming to 2°C. Our results highlight the critical importance of ramping up mitigation efforts in countries that to this point have been largely ignored. Given the accompanying challenge of economic development and poverty reduction, this will require support from historically high-emitting countries to decelerate emissions growth, including through considerable economic support and appropriate transfer of technologies that are required for transition to low carbon growth.