Context
In 2015, 196 parties adopted The Paris Agreement, a legally binding international treaty on climate change, which aims to limit the temperature increase to 1.5°C above pre-industrial levels. This agreement is based on long-term warming, thus a single year or several years over 1.5°C would not breach the agreement, however multiple decades would. It is believed that above this temperature threshold, we are at risk to far more severe and potentially irreversible climate change impacts. In the paper by Dunstone et al. (2024), the likelihood of 2024 exceeding 1.5°C is assessed.
Alongside human-induced climate change, there is also natural climate variability, which can influence global temperatures. Natural climate cycles, such as the El Niño-Southern Oscillation in the tropical pacific, can temporarily raise or lower global temperatures by fractions of a degree. Understanding these natural cycles, along with human-induced climate patterns is important for improving our ability to predict, adapt and mitigate our future climate.
Key findings
- This paper predicts that 2024 will likely be a new record year in terms of global temperature, with a 1-in-3 chance of exceeding 1.5°C above pre-industrial.
- The main drivers of this forecast are the long-term warming trend of +0.2°C per decade due to human-induced climate change, and the lagged effect of a strong El Niño event in the tropical Pacific.
- The paper highlights that 2023 was a significantly warmer year than that predicted by a Met Office forecast issued in late 2022. The cause of this additional observed warming in 2023, particularly in the southern hemisphere, still requires further understanding.
- The coming years will be key to understanding if the extreme 2023 temperature was primarily the result of extreme internal variability or whether changes in external forcings (e.g. reductions in regional anthropogenic aerosol emissions), and/or climate feedbacks, need to be better simulated.
Implications
The forecast presented in this study highlights the urgency of taking action to reduce greenhouse gas emissions and limit global warming. While a single year exceeding 1.5°C would not mean a breach of the Paris Agreement target, it does indicate how close we are to crossing this critical threshold. This forecast can help to educate policy makers on the gravity of the issue, and motivate them to enhance their national and international commitments to cut emissions. Additionally, this forecast illustrates the current state and future prospects of the global climate to the public, encouraging them to reduce their contribution to greenhouse gas emissions, while also illustrating the increasing need to adapt and prepare for our changing climate.
Reference
Dunstone N. J., Smith, D. M., Atkinson, C., et al. (2024). Will 2024 be the first year that global temperature exceeds 1.5°C? Atmospheric Science Letters, e1254. https://doi.org/10.1002/asl.1254
Keywords: atmospheric and climate dynamics; climate variability, change and impacts; global scale; weather and climate prediction; weather/climate extremes.
