IEA's Fatih Birol told a conference in Paris that data for the first nine months of the years was already pointing to a record increase in carbon emissions.
A United Nations report last week said society would have to make changes to how it consumes energy, travels and builds, to meet a lower global warming target.
"Sorry, I have very bad news. My numbers are giving me some despair," Birol told the conference at the Polish embassy in Paris.
Poland will host United Nations COP24 talks in December, which will lay out a "rule book" to implement a historic accord reached in Paris in 2015. That agreement set goals to phase out fossil fuel use this century, shift towards cleaner energies and help limit a rise in temperatures.
"Looking at data for the first nine months of this year, emissions this year will increase once again ... global emissions will reach a record historical high," Birol said.
"Therefore the chances of reaching such ambitious targets in my view, are becoming weaker and weaker every year, every month," he said.
