Recent predictions show that the 1.5°C warming threshold could be reached in 2024

ASPECT research contributes to decadal predictions released by BSC and Met Office, showing that 2024 is likely to be the warmest year on record globally, which could exceed 1.5°C.

Average global temperatures have increased since preindustrial times and are a key measure of how our climate is changing. Last year 2023 was recently confirmed to be the hottest on record, and temperatures are expected to continue to rise globally in 2024. As well as monitoring the climate with observations, climate scientists are using computer models to predict the temperatures we can expect to experience in the coming years, known as decadal predictions.

Recently announced forecasts for the expected change of the global annual surface temperature in 2024, published by ASPECT partners Barcelona Supercomputing Center and the Met Office, show that the global annual average temperature could reach 1.5°C for the first time, which would make 2024 the warmest year on record. While research on decadal predictions is ongoing at these research centres, significant contributions have been made as part of the ASPECT project.

The forecasts released by both research centres are in agreement in that the temperatures are expected to continue to increase this year, with the BSC predicting that 2024 will be between 1.43-1.63°C warmer than pre-industrial levels, and the Met Office forecasting between 1.34-1.58°C. These ranges show there is a significant chance that annual mean temperatures will exceed the 1.5°C threshold for the first time, which would be a landmark event. However, it should be noted that a temporary one-year exceedance of 1.5°C would not mean a breach of the Paris agreement, as this is defined over a longer 20 year average and therefore a long-term target of limiting warming below 1.5°C might still be feasible with rapid and urgent action.

Predicting future changes to the Earth’s climate system is a complex challenge. The increase in temperature is mainly driven by human emissions of greenhouse gases, which are causing a steady rise in global temperatures of approximately 0.2 °C per decade. In addition to changes exerted by human emissions, there are natural variations in the climate from events, such as El Niño in the tropical Pacific Ocean, which happen every few years and which our climate prediction models take into account. In the past, our hottest years on record have followed strong El Niño events, and as we are now at the peak of a strong El Niño event, this is expected to boost global temperatures in 2024.

ASPECT is working to develop and improve the existing climate prediction systems, and advances from ASPECT research have contributed to the 2024 temperature forecasts. ASPECT research was used to considerably increase the number of model runs used to generate the BSC annual global mean surface temperatures forecast for 2024. Incorporating an increased number of model runs (or ensemble members) increases the reliability of the forecast, illustrating a valuable application of ASPECT research.