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.
The US is the world’s second largest emitter of greenhouse gases.
And last year’s spike comes despite a decline in coal-fired power plants; a record number were retired last year, according to the report.
The researchers note that 2019 will probably not repeat such an increase, but the findings underscore the country’s challenges in reducing greenhouse gas output.
In the 2015 climate accord, then President Barack Obama committed to reducing US emissions to at least 26% under 2005 levels by 2025.
Now, that means the US will need to drop “energy-related carbon missions by 2.6% on average over the next seven years” – and possibly even faster – to meet that goal.
“It is certainly feasible, but will likely require a fairly significant change in policy in the very near future and/or extremely favourable market and technological conditions. “
What has changed in the US?
The last time the US saw such an increase in emissions was in 2010, as the country recovered from its longest recession in decades.
Part of last year’s spike is also the result of economic growth, but new policies have exacerbated the effects of increased industry production.
As a part of undoing what he called a “war on coal”, in 2017, Mr Trump rescinded the Clean Power Plan, which required states to slash carbon emissions to meet US commitments under the Paris accord.
What contributed the most?
Transportation remains the nation’s number one source of CO2 emissions for the third year in a row.
But the largest emissions growth came from two sectors “often ignored in clean energy and climate policymaking: buildings and industry”.
And without significant changes, industrial emissions will become bigger contributors to US CO2 and greenhouse gas emissions.
“We expect it to overtake power as the second leading source of emissions in California by 2020 and to become the leading source of emissions in Texas by 2022.”