RIYADH (BLOOMBERG) - At first glance, a 200-page treatise on energy efficiency might not resemble a glitzy Hollywood musical fantasy. But it depends on the audience.

The International Energy Agency (IEA) stirred some passionate debate last month when it urged an end to new oil and gas investments to avert disastrous climate change.

The adviser to major economies detailed the step and many others in its "road map" for reaching net-zero carbon emissions by 2050.

A less reverential verdict arrived on Tuesday (June 1) from the world's biggest oil exporter, Saudi Arabia. The IEA's energy blueprint, the kingdom said, is a sequel to La La Land - the whimsical 2016 romantic comedy movie whose lead characters break out into song-and-dance numbers.

"Why should I take it seriously?" Prince Abdulaziz bin Salman, the Saudi Energy Minister, said when asked about the report at a press conference by the Organisation of Petroleum Exporting Countries.

IEA executive director Fatih Birol, speaking earlier on Bloomberg Television, gave a more down-to-earth description of his agency's work.

The 2050 outlook merely "translates" the policy aspirations of many governments to limit greenhouse gases into practical measures, he said.

Climate activist Greta Thunberg said on Twitter that the dismissive response from the oil-exporting titan was actually a sign of alarm.

"Wow. We're clearly witnessing the beginning of the end of the fossil fuel era," Ms Thunberg said. "They're starting to panic. Let's speed up the process."