Have projected 2040 carbon dioxide emissions been revised downward by 40% in the past decade?

Emissions projections for 2040 have dropped, but not by 40%.

The 2024 International Energy Agency forecast for yearly global CO2 emissions in 2040 was 31 gigatonnes, 18% lower than the 38 Gt predicted in 2014. This reflected scenarios that considered current and announced short-term policies (at the respective times). Global carbon emissions were 37.8 Gt in 2024.

In 2024, a scenario assuming that all long-term climate pledges were carried out forecasted 19 Gt of emissions in 2040.

In the 2024 report, the IEA calculates a 2.4-degree Celsius temperature rise by 2100 given current policies and short-term proposals, versus a 1.7-degree Celsius increase if long-term pledges are implemented.

The IEA also calculates a “Net Zero Emissions by 2050 Scenario,” which limits global warming to 1.5-degree Celsius by 2100. However, the UN ruled in November 2025 that this is no longer possible to prevent an overshoot of this in the short-term.