The prospect of limiting global temperature increases to 2 degrees Celsius this century is quickly diminishing, a new U.N. report warned Tuesday, ahead of annual climate talks next week. Global greenhouse-gas emissions will be 8 to 12 billion tons higher than target levels in 2020, even if surveyed countries adhere to existing emission-reduction agreements, the U.N. Environment Program (UNEP) report said. Scientists say avoiding the upper threshold of 2 degrees Celsius (3.6 degrees Fahrenheit) would avert the worst effects of climate change, but the UNEP report said that likely would require a reduction of emissions by 14 percent in 2020. "The window of opportunity of trying to meet this 2-degree target threshold is … becoming ever more elusive," UNEP chief Achim Steiner said as he presented the report at a news conference in Berlin. The annual UNEP report projected 2020 emissions of so-called "carbon-dioxide equivalents" would be about 59 billion tons, 1 billion tons higher than the estimate in last year's report.