WMO Global Annual to Decadal Climate Update FAQs

 

1. What is the WMO Annual to Decadal forecast? 

The WMO Global Annual to Decadal Climate Update provides a synthesis of global annual and multi-year computer model predictions (forecasts) covering the next five years. The forecast includes current natural climate variations – such as fluctuations in sea-surface temperatures – and human-induced climate change – such as that caused by the increase of atmospheric greenhouse gas concentrations.
The forecast is presented as maps which show how next year - and an average of the next five years - compares to conditions from the recent past. These are also known as anomaly maps, with the past represented by the average of the three-decade period from 1991-2020. This enables users to appreciate the differences between recent climate and predicted near-term climate. There are also indices of important climate variables.

2. Who is involved in producing the WMO Annual to Decadal forecast and how often are they released?

The Annual to Decadal forecast is produced annually for the World Meteorological Organization by a consortium led by the Met Office. The Global Producing Centres are based in the UK, Spain, Canada, and Germany. Other Contributing Centres also send forecasts, but the institutes involved change from year to year.

3. What climate information is provided in the forecast?

Observations and predictions are given for temperature, precipitation, sea-level pressure and sea-ice extent. Global mean temperature, ENSO, and Atlantic Multidecadal Variability are also included. The appendix covers predictions for patterns of climate variability including the Atlantic Meridional Overturning Circulation (AMOC), Pacific Decadal Variability (PDV), Antarctic Oscillation (AAO) / Southern Annular Mode (SAM).

4. What are reference periods and how are they used in the forecast?

Two reference periods are used throughout the Annual to Decadal forecast. The first is the reference period 1991-2020. This period is the most recent 30-year climate period as is determined by the World Meteorological Organization. This is used to highlight anomalies from the recent climate period. This makes the data less ‘noisy’ and helps to highlight anomalies from longer-term climate. The second period is 1850-1900. This is a proxy for the pre-industrial period and is used to compare the degree of climate change due to human activities, for example in terms of global warming. Currently the global warming level is around 1.3°C above the 1850-1900 averaging reference period.

Forecast data is shown as an anomaly compared to these reference periods to minimize the uncertainty associated with absolute temperature or precipitation data; a standard practice in weather and climate prediction. Using two reference periods also allows for comparisons between both an unaltered pre-industrial climate, and a more recent climate that forecast users might be more familiar with.

5. How can the Annual to Decadal forecast be used?

The Annual to Decadal update was developed to bridge the gap between weather forecasts and longer-term climate change projections. The Annual to Decadal forecast starts from the current state of the Earth system, including components from the atmosphere, oceans and land. Computer models take this starting point and predict how the future climate evolves over the forecast period using the laws of physics. This means the forecast is potentially useful to users interested in being able to identify fluctuations in regional climate over the next few years to highlight areas of potential social-environmental risk, such as whether a region is expected to be wetter or drier than average. The forecast can also inform users of the likely temperature ranges, levels of storminess in the Atlantic and expected phase of the El Niño Southern Oscillation. Such information is helpful for experts to understand areas of vulnerability including the potential need for early action and preparedness.

6. Can it tell me the weather forecast in four years’ time?

No. The Global Annual to Decadal Climate Update is not able to provide weather forecasts for specific future dates. Instead, the update predicts global climate for the coming year and the next five-year period. The computer models represent predictable components of the Earth’s climate, including human-induced climate change. For example, the report cannot make a prediction about rain on specific days in Timbuktu in future years, but it can provide a vital insight into the likely increase in rainfall in the drought-prone Sahel region of sub-Saharan Africa over one year or the next five years.

7. What role does artificial intelligence (AI) play in producing the Global Annual to Decadal Climate Update?

Currently, the Global Annual to Decadal Climate Update is based on harnessing several physics-based computer models. These models are run many times – with slightly different starting conditions – producing a series of ensemble members providing the basis for the range of predictions within the Annual to Decadal report. Artificial intelligence and machine learning techniques are rapidly influencing the science and operation of weather forecasting. In the near future, these developments are expected to be useful, aiding aspects of climate prediction. However, the current models are constrained by the laws of physics which is important as the climate is currently changing fast and it is still unclear just how competently machine learning will predict events that have not yet been seen in the observational record.

8. How can I access the Annual to Decadal forecast data?

To access the forecast data, send your request to [email protected]. This is raw data provided for research purposes for someone who has experience working with climate data.

The above information has been produced as part of the Met Office Hadley Centre Climate Programme 2024-27.