The potential of seasonal-to-decadal-scale inter-regional linkages to advance climate predictions (InterDec)

Globally averaged surface air temperature (SAT) during the 20th and 21st centuries displays a gradual warming and superimposed year-to-year and decadal-scale fluctuations. The upward trend contains the climate response to an anthropogenic increase of heat-trapping atmospheric greenhouse gases. The temperature ups and downs around the trend - that are particularly pronounced in the Arctic - mostly reflect natural variability. Natural climate variations are of two types, internal and external. The former is produced by the climate system itself, e.g. due to variations in ocean circulation. An example of the latter is solar-induced climate variability. Decadal-scale variability is of large societal relevance. It is observed, for example, in Atlantic hurricane activity, Sahel rainfall, Indian and East Asian Monsoons, Eurasian winter coldness and in the Arctic SAT and sea ice. The understanding and skillful prediction of decadal-scale climate variability that modulates the regional occurrence of extreme weather events will be of enormous societal and economic benefit.
InterDec is an international initiative aiming at understanding the origin of decadal-scale climate variability in different regions of the world and the linkages between them by using observational data sets and through coordinated multi-model experiments. How can a decadal-scale climate anomaly in one region influence very distant areas of the planet? This can happen through atmospheric or oceanic teleconnections. Fast signal communication between different latitudinal belts within days or weeks is possible through atmospheric teleconnection, whereas communication through oceanic pathways is much slower requiring years to decades or even longer. Understanding these processes will enhance decadal climate prediction of both mean climate variations and associated trends in regional extreme events. Scientists from different European countries, from China and Japan will closely collaborate to disentangle the secrets of the inter-relations of decadal-scale variability around the globe.

Societies are vulnerable to weather and climate extremes by setting agriculture, infrastructure (e.g. electricity supply or transport) and human activities and life at risk.
InterDec will provide an improved science based foundation of the linkages between the Arctic , midlatitudes and the Tropics, thus leading to a better understanding of regional climate variability and change. This will include more robust estimates of uncertainties, as well as to more reliable predictions of regional weather and climate extremes, such as breaks and intensifications of East Asian and African (Sahel) Monsoon, Eurasian mid-latitude cold spells, heat waves and flooding or rapid declines in Arctic sea ice. More reliable climate predictions and projections can improve disaster prevention as well as adaptation and mitigation strategies. The latter are especially important in densely populated areas. More reliable climate predictions and projections can also make the business sector more resilient and competitive and optimize stakeholder decisions.

InterDec science will help to inform decision making in a range of areas including: the development and exploitation of Arctic Sea routes and the management of energy infrastructure, both in terms of short term resource management on sub-seasonal to seasonal timescales and decisions about the development of new infrastructure; and development of agricultural policy for food security. Improved confidence in sub-seasonal and seasonal forecasts will allow for better planning and response for disaster risk reduction in response to extreme events, e.g. heat waves, floods and droughts.