BSC predicts global-mean temperature could reach 1.5ºC warming target within 5 years

13 March 2023

The BSC decadal forecast system anticipates that global mean surface temperatures will continue to rise in the coming years due to increasing greenhouse gas concentrations and will likely make 2023 one of the five warmest years on record because of hotter conditions in the tropical Pacific.

Decadal climate predictions describe variations in climate development for the next few years up to a decade, closing the gap between shorter-term weather and seasonal climate forecasts and longer-term climate change projections.

The BSC is a renowned centre for decadal prediction worldwide and produces a climate prediction for the next decade every year.

Predicting the variations in climate over the near future is considered one of the most challenging problems the climate forecasting community faces. Until recently, seasonal predictions (for the next months) and climate projections (for the next 100 years) were the only sources of future climate information available to interested users. However, newly developed decadal climate prediction systems can foresee variations from a year to a decade. Within this timescale, the evolution of the Earth system is impacted by both natural variability and external forcings (such as rising greenhouse gas concentrations in the atmosphere). Decadal predictions attempt to fill the gap between seasonal predictions and climate projections, offering the potential to inform current adaptation and, thus, increase resilience.

The Barcelona Supercomputing Center - Centro Nacional de Supercomputación (BSC-CNS) is one of the five “Global Producing Center of Near-Term Climate Prediction” endorsed by the World Meteorological Organization (WMO) that produces operational decadal climate predictions every year. The Climate Variability and Change group at the Earth Sciences Department develops the BSC decadal forecast system, which predicts changes in average climate conditions (such as temperature or precipitation, among many other variables) and the frequency and intensity of extreme climate events (such as floods and droughts) over the next decade.

The service combines observational data and climate models, a mathematical representation of the Earth’s climate typically covering the atmosphere, ocean, sea ice and land, to provide the best estimate of the climate system at a specific time. In addition, the BSC also conducts research to enhance decadal predictions and exchange knowledge with interested users since predicting the variations in climate for the upcoming 1-10 years offers multiple opportunities for adaptation to a changing climate in the near future and is crucial to support the development of a more resilient society.

The 2023-2032 prediction

The BSC decadal forecast system predicts that the global mean surface temperature will continue to rise in the coming years due to increasing greenhouse gas concentrations. In the next five years (2023-2027), the global mean surface temperature is predicted to be between 1.44-1.55ºC warmer than preindustrial levels (defined as the average from 1850 to 1900), with a central estimate of 1.49ºC. Hence, there is a significant chance of exceeding 1.5°C above preindustrial levels within the next five years, indicating that the world is rapidly approaching the Paris Agreement target.

This year, 2023, is expected to be one of the warmest years on record. The BSC forecast system predicts the end of three consecutive years with La Niña conditions and transitions to warmer conditions in the tropical Pacific. La Niña conditions are characterised by lower-than-average sea surface temperatures over the Tropical Pacific, which have a cooling effect on global average temperature. Therefore, the shift to a warmer Tropical Pacific will likely lead to higher global mean surface temperatures in 2023 with respect to previous years.

How the decadal predictions are made

Decadal predictions are typically produced using a technique similar to that used for seasonal forecasts, i.e. by initialising a climate model with the observed state and integrating it forward in time. These climate models are a mathematical representation of the Earth’s climate (i.e. atmosphere, ocean, and sea ice) and are built using the fundamental laws of classical physics and thermodynamics. The most common source of initial conditions is observation-based data reconstructions. External factors (both natural and anthropogenic) influencing the Earth system are also introduced in the model, such as volcanic aerosols and rising greenhouse gas concentrations. The model produces an ensemble of 10-year simulations to finally obtain the decadal forecast. New decadal predictions for the coming 1-10 years are typically produced at the end of each year.