In its latest "Emissions Gap" report issued ahead of an important climate conference in Germany next week, the program takes aim at coal-fired electricity plants being built in developing economies and says investment in renewable energies will pay for itself — and even make money — over the long term.
Tuesday's report comes as U.N. officials are making a renewed push to maintain momentum generated by the Paris climate accord of 2015. It aims to cap global temperature increases to 2 degrees Celsius by the year 2100 compared to average world temperatures at the start of the industrial era.
But that agreement has come under threat after Donald Trump suggested he might opt to pull out of it. The new report doesn't include any impact from the US withdrawing, and if it did then the picture would become "even bleaker", the UN said.
"The Paris agreement boosted climate action, but momentum is clearly faltering," said Edgar Gutierrez-Espeleta, Costa Rica's environment minister who heads the 2017 UN Environment Assembly. "We face a stark choice: up our ambition, or suffer the consequences."
The report does find some causes for hope. It notes that there is "rapidly expanding mitigation action" being done by governments, and finds that carbon dioxide emissions seem to have stopped rising since 2014. But it noted that other dangerous greenhouses gases like methane continue to rise.
The report also highlights the positive effects of investment in solar and wind energy and efficient appliances and cars, and efforts to preserve forests.
But it warns that both private companies and governments could reverse those gains by failing to do enough to counteract current levels of emissions.
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