Decadal forecast 2013

Forecast issued in January 2014. The forecast will be updated in January 2015. Further discussion and background information can be found in a related Decadal forecast 2014-2018.

Decadal forecasts, also called 'near-term' climate predictions, range up to a decade ahead. Predictions account for natural variability and climate change as these are expected to be of similar size in many parts of the world. Forecasts are experimental, so at this early stage of development expert advice is needed to assess the reliability of regional predictions.

Important

• Long-range forecasts are unlike weather forecasts for the next few days
• Forecasts show the likelihood of a range of possible outcomes
• The most likely outcome in the forecast will not always happen
• Forecasts are for average conditions over a wide region and time period
• For more details on interpretation, see How to use our long-range predictions

Summary

• Averaged over the five-year period 2014-2018, forecast patterns suggest enhanced warming over land, and at high northern latitudes. There is some indication of continued cool conditions in the Southern Ocean, and of a developing cooling in the north Atlantic sub-polar gyre. The latter is potentially important for climate impacts over Europe, America and Africa.
• Averaged over the five-year period 2014-2018, global average temperature is expected to remain high and is likely to be between 0.17°C and 0.43°C above the long-term (1981-2010) average. This compares with an anomaly of +0.26°C observed in 2010, the warmest year on record.
• For this forecast the baseline period has been updated to be 1981-2010 (compared to 1971-2000 used previously). This provides a more recent context and is consistent with our seasonal forecasts.

Introduction

Decadal forecasts are designed to predict fluctuations in the climate system over the next few years. They take into account natural variability as well as human influences. This is achieved by initialising climate models with observations of the current climate state, in addition to specifying changes in radiative forcing due to greenhouse gases, aerosols (both volcanic and man-made), and solar variability. Further details can be found in a Met Office Decadal Forecasting - What is it and what does it tell us? .

The latest Met Office decadal forecast presented here was started from the observed sea surface temperature pattern shown in Figure 1, along with similar observations of temperature and salinity below the ocean surface, and atmospheric winds, temperatures and surface pressure. The temperatures in Figure 1 show a weak La Niña pattern in the tropical Pacific, relatively cool conditions in the Southern Ocean, and warm conditions in the North Atlantic.

Forecast

The following maps (Figure 2) show the difference between the predicted geographical distribution of temperatures over the period November 2013-October 2018 and 1981-2010 averages. Diagram A is the most likely forecast outcome. Diagrams B and C indicate the range of forecast temperatures, such that we expect only a 10% chance of temperatures at a particular location being less than those in B, and only a 10% chance of temperatures higher than in C. Note that these ranges are for each individual location. The chances of these limits being met everywhere are very small, so the complete patterns shown in diagrams B and C are very unlikely to be realised.

 

Spatial patterns suggest more warming over land than ocean, and at high northern latitudes. There is some indication of continued cool conditions in the Southern Ocean, and of a developing cooling in the north Atlantic sub-polar gyre. Uncertainties in the forecast are considerable: for the period 2014-2018 most regions are expected to be warmer than the average of 1981 to 2010, but regional cooling is possible over much of the Pacific, North Atlantic and Southern Oceans, and over some land regions. The updated forecast (Figure 2 A-C) is very similar to the forecast issued a year ago (Figure 2 D-F).

Averaged over the five-year period 2014-2018, global average temperature is expected to remain between 0.17°C and 0.43°C (90% confidence range) above the long-term (1981-2010) mean (see blue shading in Figure 3 below).

The warmest individual year in the 160-year Met Office Hadley Centre global temperature record is 2010, with a temperature of 0.26°C above the 1981-2010 mean. The forecast of continued global warming is largely driven by continued high levels of greenhouse gases. However, the forecast initially remains towards the lower end of the range simulated by CMIP5 models that have not been initialised with observations (green shading), consistent with the recent pause in surface temperature warming. Changes in the exchange of heat between the upper and deep ocean appear to have caused at least part of the pause in surface warming, and observations suggest that the Pacific Ocean may play a key role. For further discussion on the surface warming pause see the Met Office The recent pause in warming.

 

Verification

Retrospective forecasts have been made from numerous dates in the past. Some of these are shown in the top global annual temperature forecast figure (red shading from 1960, 1965, ... 2005). Generally, the forecasts predict rises in temperatures similar to those observed (black curves). Many facets of the variability, such as the record warming caused by the large 1997-1998 El Niño and the cooling caused by the 2008 La Niña, are largely within the range of the predictions (red shading).

The following maps (Figure 4) compare observed (A) and forecast (B) surface temperatures (°C) for November 2008 to October 2013 relative to the 1981-2010 long-term average. Forecasts were made starting from November 2008. Stippling shows regions where the observed temperatures do not lie within the predicted range (5-95%) of the forecast. The forecast correctly predicted enhanced warming over high northern latitudes, and in most regions the observations lie within the predicted range. However, the predicted temperatures are too warm in the tropical Pacific Ocean and over parts of China, and too cold over the southern Atlantic and Indian oceans.