The Earth Will Warm by 1.5°C by 2029 at Current Fossil Fuel Burning Rates

In just over five years, around the beginning of 2029, the world is likely to exceed the internationally agreed-upon temperature limit for global warming if it continues to burn fossil fuels at the current rates, according to a new study.

The study brings forward by three years the date when the world is projected to reach the critical climate threshold of a 1.5-degree Celsius (2.7-degree Fahrenheit) increase from pre-industrial times.

In addition to this temperature rise, the risks of catastrophes will increase, as the world is likely to lose a significant portion of its coral reefs, key ice sheets may start irreversibly melting, and water shortages, heatwaves, and mortality from extreme weather events will sharply rise, according to earlier reports from the UN.

The achievement of this threshold will happen sooner than initially anticipated due to the world's progress in reducing another type of air pollution—tiny smoke particles known as aerosols. According to the lead author of the study, aerosols slightly cool the planet and mask the consequences of burning coal, oil, and natural gas. In other words, while cleaning up aerosol pollution is beneficial, its success means a slightly faster increase in temperature.

The study, published on Monday in the journal Nature Climate Change, calculates the remaining "carbon budget," which is how much fossil fuel the world can burn while still having a 50% chance of limiting warming to 1.5 degrees Celsius from pre-industrial times. This threshold was set by the 2015 Paris Agreement.

The past decade has already been on average 1.14 degrees Celsius (2.05 degrees Fahrenheit) warmer than in the 19th century. According to scientists, last year was 1.26 degrees Celsius (2.27 degrees Fahrenheit) warmer, and this year is likely to surpass that figure.

The new study establishes a carbon balance of 250 billion metric tons. The world currently burns slightly over 40 billion metric tons per year (and the rate continues to rise), leaving six years left. However, these six years began in January 2023, as stated in the study, so there are only five years and a few months left.

"It's not that the fight against climate change will be lost in six years, but I think that, probably, if we are not already on a trajectory of substantial reductions, it will be too late to fight for that 1.5-degree limit," said Robin Lamboll, the lead author of the study and a climate scientist at Imperial College London.

According to Lamboll, the UN Intergovernmental Panel on Climate Change (IPCC) report for 2021 set the fixation of the 1.5-degree temperature at around mid-2032, which aligns with his team's findings. The updated version prepared by many of the IPCC authors in June of this year maintains the same carbon budget as Lamboll's team but incorporates more detailed analysis, according to Valérie Masson-Delmotte, co-chair of the IPCC report.

The most significant change from the 2021 report compared to this year's research is that the new studies show a more substantial reduction in aerosol emissions, which result from forest fires, sea salt spray, volcanoes, and fossil fuel burning and contribute to the formation of soot in the air, which slightly cools the planet, countering the greenhouse effect. Lamboll says that as the world reduces carbon dioxide emissions, it is simultaneously reducing cooling aerosols, and this is more accounted for in the study, as is the evolution in computer modeling.

Although the carbon budget appears to be depleted by early 2029, it does not mean the world will instantaneously become 1.5 degrees warmer than pre-industrial times. The actual temperature change may occur slightly earlier or even a decade or two later, but it will happen once the budget is exhausted, according to Lamboll.