A new report has found that US carbon dioxide emissions rose by 3.4% in 2018 after three years of decline.
The spike is the largest in eight years, according to Rhodium Group, an independent economic research firm.
The data shows the US is unlikely to meet its pledge to reduce emissions by 2025 under the Paris climate agreement.
Under President Donald Trump, the US is set to leave the Paris accord in 2020 while his administration has ended many existing environmental protections.
While the Rhodium report notes these figures – pulled from US Energy Information Administration data and other sources – are estimates, The Global Carbon Project, another research group, also reported a similar increase in US emissions for 2018.