22/03/2018

What information is necessary to be “weather smart” and “climate ready”, and how is it produced?  On World Meteorology Day, Silvio Gualdi explains the difference between weather forecasts and climate predictions, and why they are important for our present and future societies.

Tools and strategies to cope with the consequences of extreme meteorological events and global warming are a priority in a world where climate equilibria are increasingly altered. On World Meteorological Day, the World Meteorological Organization (WMO) chose the theme “Weather-ready, Climate-smart” to raise the attention on an increasingly critical situation and on the urgency to develop adequate preparedness and response capacity.
Carbon dioxide concentration permanently exceeded 400 ppm, the highest level in three millions years. According to the latest report of WMO (State of the Climate 2017), climate warming trend continues, with 2017 being the warmest year on record not influenced by an El Niño event. At the same time, we are starting observing growing impact of meteorological phenomena on economies and populations. In 2017 the hurricane season in the Caribbean caused damages of 215 billion dollars, the highest cost recorded so far. According to recent data by the European Environment Agency (presented by Sergio Castellari in the webinar “Adaptation to climate change in Europe: linking knowledge, policies and practices“, organized by the CMCC Foundation and the Italian Society for Climate Sciences, SISC), natural disasters caused by weather and climate-related extremes accounted for some 83% of the monetary losses in the EU Member States, accounting for a total of EUR 410 billion euros.

Growing population and economic wealth, urbanization in hazard-prone areas, and degradation of natural ecosystems contribute to increase the exposure and vulnerability of societies to meteorological and climate events such as cyclones, heavy rains, heat waves, droughts.

The primary tool for planning and implementing adequate prevention and risk reduction strategies is information, with the aim to provide the most accurate possible weather forecasts and climate predictions for the short, medium and long term. These are different kinds of information elaborated thanks to very similar tools, as Silvio Gualdi, Director of the “Climate Simulation and Prediction” (CSP) Division of the CMCC, explained.
Weather forecasts are very close to being deterministic forecasts, meaning that their goal is to determine – to the most exact extent possible – how the weather will be in a certain place and on a certain time. This is feasible within a certain limit, theoretically of around ten days but, in reality, it is often even shorter. Beyond this limit the forecast becomes progressively less reliable. In climate predictions the goal is to determine the probability that certain conditions will occur in a given period of time, for example the probability that next summer will be warmer or colder,  drier or wetter, than usual. While the accuracy of weather forecasts can be evaluated by directly observing what happens, the reliability of seasonal predictions is determined by the system’s capacity to deliver probabilities that are consistent with observations, thus only by examining a (reasonably long) historical series of forecasts made in the past”.

The systems applied for elaborating weather forecasts and climate predictions are very similar mathematical models. They are used in different ways with the help of powerful supercomputing centers such as the CMCC’s in Lecce or the new datacenter of the European Center for Medium-Range Weather Forecasts (ECMWF), which will be hosted in Bologna starting from 2019.

“The models that are used to produce weather forecasts are close relatives, even brothers, of the models used for climate predictions,” Gualdi explains. “Currently major centers are increasingly using the so called “seamless systems”, which are a continuum in their structure and definition. By adopting very similar approaches, these models are used to produce either weather forecasts or climate predictions”.

The information obtained represents the basis of those climate services that public institutions and companies need to deal with weather and climate impacts, and to reduce exposure to meteorological risks in the short, medium and long term. In these context, CMCC develops seasonal predictions for companies operating in different sectors. “For example, we develop seasonal predictions for an agri-food company, in order to determine the probability of adverse environmental conditions in certain areas of Turkey, where the world’s largest production of hazelnuts takes place. There is a strong interest to know in advance the probability of temperature conditions or drought problems which may affect the cultivation of hazel trees”, Gualdi says. “We also provide seasonal predictions assessing the probability of precipitation anomalies for a company producing hydroelectric energy. In this way, it is possible to plan the management of water basins, for example by releasing water when the predictions indicate a very rainy season or by retaining as much water as possible in the reservoirs to prepare for drought conditions”.

This kind of information is also useful to civil protection agencies, which thanks to early warning systems are able to better deal with conditions that can become critical. In its message for World Meteorology Day, the WMO Secretary General emphasizes that investing in the development and enhancement of national meteorological and climate services is the best way for governments to adapt to climate change. With the establishment of the agency ItaliaMeteo, included in the Budget Law for 2018, Italy is following this path. As the new ECMWF datacenter, ItaliaMeteo will be based in Bologna and it will be the first civil national body for meteorology and climatology, with the aim of coordinating the many regional and local actors operating in this sector.

“The ultimate goal, and the wish of those involved in developing these activities, is that the information we produce is used to reduce the impacts of climate change on our lives”, Gualdi concludes. “Our society is becoming increasingly vulnerable to these risks. Our goal should be to make it increasingly more resilient to them”.