Frequently asked questions world map


Frequently asked questions

General / Weather / Climate / Water / Natural hazards and disasters / Environment / Observations


  • 1. What is the World Meteorological Organization?

      • The World Meteorological Organization (WMO) is a specialized agency of the United Nations dedicated to meteorology (weather and climate), operational hydrology (water) and other related geophysical sciences such as oceanography and atmospheric chemistry.

  • 2. When did WMO start?

      • WMO emerged from the International Meteorological Organization (IMO), which dates back to 1873. WMO’s Convention came into force on 23 March 1950 and the Organization became a specialized UN agency in 1951.

  • 3. What does WMO actually do?

      • WMO coordinates the activities of National Meteorological and Hydrological Services in 188 States and Territories so that basic weather, climate and water services are made available to anyone who needs them, when they need them. Through this coordination, a global, end-to-end capability that delivers worldwide access to a wide variety of real-time and non-real-time data and information was established in 1950 and has since undergone continuous improvement in scope, reliability and accuracy. These weather, climate and water services contribute towards socio-economic development, environmental management and policy formulation. WMO guarantees the publication of observations and statistics and furthers the application of meteorology and hydrology (including the monitoring and predictions of climate change and ozone) to all aspects of human activities such as aviation, shipping, water issues and agriculture. WMO also encourages research and training in meteorology and hydrology and their related applications and contributes towards reducing the impact of weather- and climate-related hazards. This is accomplished through regular, reliable forecasts and early warnings on flooding, drought, tropical cyclones, tornadoes and other extreme events. Predictions concerning locust swarms and the transport of pollutants (nuclear and toxic substances, volcanic ash) are also provided by WMO Members.

  • 4. How does WMO function?

      • WMO acts as a central framework where Members, including representatives of National Meteorological and Hydrology Services (NMHSs), can effectively discuss all issues related to weather, climate and water. The goal of WMO is to ensure that these streams of information flow as rapidly and efficiently as possible and contribute to the safety and well-being of all peoples. The Organization is governed by the World Meteorological Congress composed of all WMO Members, which meets every four years to review, and give policy guidance to, WMO Programmes. The Executive Council (37 members) gathers annually and monitors the implementation of decisions taken by Congress. Six regional associations (RAs: Asia, Africa, Europe; North America, Central America and the Caribbean; South America and South-West Pacific), composed of their geographical Members, coordinate activities within their respective Regions. Members select experts to take part in eight technical commissions researching issues within their areas of competence. The Secretary-General (Michel Jarraud, since 2004) heads the WMO Secretariat based at WMO headquarters in Geneva. The body acts as an administration, documentation and information centre for the Organization. Pressing issues or international emergencies that need to be addressed can be accommodated through existing programmes.

  • 5. How does WMO monitor global weather and climate?

      • WMO undertakes this task through the National Meteorological and Hydrological Services of its Members which own and operate the systems for collecting, processing and analysing information from thousands of observation systems, including satellites and ships.


        WMO issues Annual Statements on the Status of the Global Climate. These statements document the extreme weather and climate events in the regional context and provide a historical perspective on the variability and trends of climate, particularly surface temperatures that have occurred since the 19th century. WMO is also working with the National Meteorological and Hydrological Services to develop climate change detection tools and software to compute indices that reflect the best estimate of climate trends within the countries.

  • 6. What is the difference between weather and climate?

      • Climate, in a narrow sense, can be defined as the average weather conditions for a particular location and period of time. In a wider sense, it is the state of the climate system (see section 1.2.2). Climate can be described in terms of statistical descriptions of the central tendencies and variability of relevant elements such as temperature, precipitation, atmospheric pressure, humidity and winds or through combinations of elements, such as weather types and phenomena that are typical to a location, region or the world for any period of time.

  • 7. How many countries are Members of WMO?

      • WMO’s Membership comprises 183 countries and 6 territories (on 4 December 2009).

  • 8. How do Members interact?

      • Delegates and experts work together on various programmes, exchanging information, research, statistics and technology to provide a better picture of global conditions. They also share experiences and discuss ways of discovering and employing improvements.

  • 9. How can I become a meteorologist?

      • Meteorology requires knowledge of higher mathematics, physics and chemistry, as well as good computer proficiency. The basic requirement for becoming a Meteorologist is a BSc degree in Meteorology or Atmospheric Sciences. Another option is to first get a BSc in Mathematics, Physical Sciences or Engineering and then follow courses in Meteorology. Teaching, research or management positions usually require higher degrees. Meteorological technicians, who may not possess an academic degree, generally undertake the responsibility of collecting and reporting observational weather data. Their qualification is normally obtained through completion of technical-level courses of a varying duration (between a few months and 1-2 years) depending on the envisaged work.


  • 1. How far ahead can we predict the weather and climate these days?

      • A five-day weather forecast today is generally as reliable as a three-day forecast two decades ago. Outlooks of up to a week, especially in temperate mid-latitude regions are becoming increasingly reliable. Information can be disseminated around the world from one location to another within three hours, while recently understood phenomena such as El Niño Southern Oscillation (ENSO) (El Niño, La Niña and neutral phases) can be forecast up to a year in advance. Seasonal climate predictions can be forecast up to a month, three months or six months ahead although these climate predictions are probabilistic in nature. Such forecasts, often from advanced centres, are made available globally to all nations.

  • 2. Why are weather forecasts sometimes inaccurate?

      • Air pressure, temperature, mountain ranges, ocean currents and many other factors combine to produce an enormous quantity of interacting variables all of which can alter the weather to a greater or lesser extent. However, greater understanding of the science, plus the use of powerful computer models, continue to improve our ability to make more accurate predictions with longer lead times.

  • 3. How can we improve weather and climate forecasts?

      • WMO’s 10-year THORPEX (The Observing System Research and Predictability Experiment (an activity of WMO’s World Weather Research Programme) is currently addressing this very concern. It focuses on identifying problems with forecasting and research. Enhanced observation and data analysis systems, increased understanding of atmosphere dynamics and predictability; and improved global and regional numerical weather prediction models are some areas where improvements can be made. Training more meteorologists in developing nations and providing them with more and sophisticated equipment are also necessary.


        Concerted efforts are being made by some National Meteorological and Hydrological Services and leading international climate modelling groups under the coordination of the World Climate Research Programme to develop regional climate models so that they become capable of providing regional-scale (typically 25 x 25 km and higher resolution with appropriate computing facilities), climate information for impact studies, to facilitate their use within the modest computational infrastructure of developing countries, and to provide training in the use of this information as necessary.

  • 4. Will we ever be able to control weather in the future?

      • Experiments on weather modification have been, and continue to be, carried out. The most prevalent method is cloud seeding, which dates back to 1946 and is the attempt to alter the amount or type of precipitation produced by clouds. This is done by targeting clouds from aircraft or from the ground with substances such as silver iodide, dry ice and even salt. In the 1950s and 1960s, US scientists experimented in modifying tropical cyclones (Project Stormfury) but the research was inconclusive. Today, cloud seeding is employed in many countries in an effort to increase precipitation in drought-stricken areas, reduce the size of hailstones that form in thunderstorms, reduce fog around airports and even to provoke snow at major ski resorts. However, the impacts of operations in rainfall enhancement and hail suppression have still not been properly quantified and modification remains an area of active research.

  • 5. Why is it that developing nations always seem to suffer most during extreme weather events?

      • Every year, natural disasters affect many communities around the world, leading to loss of lives, destruction of social and economic infrastructure and degradation of already fragile ecosystems. Such hazards are inevitable and can threaten everyone, but they tend to hit communities in developing and least developed countries the hardest, increasing their vulnerability and setting back their economic and social goals, sometimes by decades. While economic losses in dollars for developing countries are fewer than those for developed countries, impact (as a percentage of GDP) is often much higher. Many developing nations lie in tropical zones where extreme weather events such as tropical cyclones, droughts and flooding are more frequent than in other regions. Developing nations possess limited facilities and qualified human resources to monitor and predict these phenomena and provide warnings to all sectors of the population. Addressing this challenge is a major concern for WMO.


  • 1. How is WMO tackling climate change?

      • WMO and the United Nations Environment Programme (UNEP) established the Intergovernmental Panel on Climate Change (IPCC) in 1988 to take stock of scientific knowledge of the threat of human-induced climate change. The IPCC is now recognized as the authorative international, scientific and technical voice on climate change. WMO hosts the IPCC Secretariat.


        WMO’s World Climate Programme, in partnership with other UN specialized agencies, such as the UN Environment Programme, the UN Education, Scientific and Cultural Organization (UNESCO) and the Intergovernmental Oceanographic Commission (UNESCO),  as well as National Meteorological and Hydrological Services, research institutions and organizations, facilitates international climate change research programmes with the aim of providing better and more up-to-date information, thus enabling decision-makers to reach more informed conclusions as to the causes and impacts of climate change and to develop appropriate response strategies.

  • 2. Is our climate changing?

      • Experts generally agree that the Earth is warming up. How much this has been directly attributed to or caused by human activity—the effects of which are extremely difficult to assess—is not clear, though increases in greenhouse gases such as carbon dioxide are more than likely taking their toll. What is clear is that, globally, 1998 was the warmest year ever recorded and eight of the 10 other top annual mean temperatures have occurred during the last decade. The upturn has likely been responsible for melting ice sheets in both polar regions. Mountain glaciers around the world have been on the wane as well. A rise in global mean sea level of between 0.09 and 0.88 metres by 2100 has been projected, mainly due to the thermal expansion of sea-water and loss of mass from ice caps and glaciers.

  • 3. How will this affect our climate over the coming century?

      • The Intergovernmental Panel for Climate Change (IPCC) Fourth Assessment Report (2007) projects an increase of globally averaged surface temperatures of 2.1 to 6.1 degrees Celsius, compared to the middle of the 20th century, by 2100. Nearly all land areas are projected to experience more hot days and heat waves and fewer cold days and cold waves. In a warmer world, the hydrological cycle becomes more intense, with heavier and more frequent precipitation and flooding in many areas. Increased summer drying and associated risk of drought over most mid-latitude continental interiors are also predicted. Climate change is expected to decrease water availability in arid and semi-arid regions, which could lead to a doubling of the population living with water scarcity in the next 30 years. Areas affected by diseases such as malaria (and waterborne illnesses) could well expand, while crop models indicate a decrease in yields for tropical and sub-tropical areas. It has also been calculated that a rise of more than a few degrees would trigger a fall in plant productivity throughout most regions of the world. IPCC has started work on its Fifth Assessment Report, aimed at refining a number of the previous conclusions, but the whole report, which requires the coordinated work of about 2000 scientists, will not be completed before 2014.

  • 4. What is the difference between climate change and climate variability?

      • Climate variability is the term used to describe a range of weather conditions that, averaged together, describe the “climate” of a region. In some parts of the world, or in any region for certain time periods or parts of the year, this variability can be weak, i.e. there is not much difference in the conditions within that time period. However, in other places or time periods, conditions can swing across a large range, from freezing to very warm, or from very wet to very dry, thereby exhibiting strong variability. A certain amount of this is understood and accepted by the region’s inhabitants. Occasionally, an event or sequence of events occurs that has never been witnessed or recorded before, such as the exceptional hurricane season in the Atlantic in 2005 (though even that could be part of natural climate variability). If such a season does not recur within say, the next 30 years, we would look back and call it an exceptional year, but not a harbinger of change. For the scientific community to recognize a change in climate, a shift has to occur, and persist for quite a long time. The Intergovernmental Panel on Climate Change (IPCC) is conducting considerable efforts in trying to determine, for various hydrometeorological hazards (e.g. tropical cyclones and tornadoes) and for related events (e.g. flash floods), whether their occurrence is affected by human-induced climate change. The IPCC Fourth Assessment Report provides evidence that climate change affects the frequency and (or) intensity of some of those events, but further work is under way to refine those findings and prepare a more comprehensive assessment as part of a Special Report to be published in 2011.

  • 5. What are El Niño and La Niña?

      • El Niño, Spanish for "boy child" (because of the tendency of the phenomenon to arrive around Christmas), is an abnormal warming of water in the Equatorial Pacific Ocean every three to five years and can last up to 18 months. Severe cases of El Niño, as in 1997/98, are responsible for drought, flooding, as well as areas of formation for tropical cyclones and severe winter storms. The 1997/98 El Niño and its associated impacts have been blamed for the deaths of hundreds of people and caused billions of dollars of damage in an estimated 15 countries especially in the Panama Canal region but also as far away as the east coast of Africa. La Niña means “the little girl”, the opposite of El Niño, and refers to the abnormal cooling of the ocean temperatures in the same Pacific region.


  • 1. What is the hydrological cycle?

      • Around 98 per cent of the water on Earth lies in the seas and is therefore saline. Powered by solar energy, seawater and other surface waters evaporate and form clouds. These clouds condense and provide freshwater in the form of precipitation. Under the force of gravity, freshwater makes its way back towards the seas in rivers and as groundwater, serving the needs of living organisms on the way. From the sea it again evaporates and the process repeats itself.

  • 2. Are the world's water resources decreasing?

      • Only 2 per cent of the total water available at any given time on Earth is freshwater, approximately 70 per cent of which is located in the ice caps. Globally, over a short period of time (a few centuries in this case), total freshwater delivered through the world’s hydrological cycle remains constant. However, water is not distributed evenly around the world. In any given river basin, freshwater delivery through rain differs from year-to-year. Many of the planet’s largest river basins run through thinly populated regions, while numerous densely populated zones possess inadequate water supplies, a problem which has been worsened by increasing pollution. Freshwater supplies have been further stretched by demands from irrigation, industry, urbanization and rising living standards.

  • 3. How is climate change likely to affect the availability of water resources?

      • Rising temperatures will accelerate the hydrological cycle, changing the temporal and spatial distribution of freshwater, though total planetary water availability is likely to remain constant. The shrinkage of glaciers will probably result in reduced flows to areas which rely on such supplies in lean seasons. Should sea levels rise, coastal aquifers could suffer reductions in water quality. Demand from human consumption, agriculture and natural vegetation are expected to alter as well. All these factors are likely to have an impact on our water management practices.

Natural hazards and disasters

  • 1. What role does WMO play in the event of a natural disaster?

      • WMO works through the National Meteorological and Hydrological Services (NMHSs) to ensure that, among other things, effective 24-hour operational early warning systems for weather-, climate- and water-related hazards are made available in a timely manner and with longer lead times across political boundaries to all affected populations. Through its 10 international, scientific and technical programmes, a network of 188 National Meteorological Services (NMSs), 40 Regional Specialized Meteorological Centres (RSMCs) and three World Meteorological Centres (WMCs), WMO coordinates the global operational infrastructure for observing, detecting, modelling, forecasting and developing and issuing early warnings for a wide range of weather-, climate- and water- related hazards such as tornadoes, severe storms, tropical cyclones, storm surges, floods, heat waves, cold spells, droughts, locust swarms and forest fires. For example, WMO’s global network has proved highly effective for issuing tropical cyclone (hurricanes and typhoons) early warnings over the past 20 years in the Atlantic and Pacific regions, resulting in the prevention of significant loss of lives and property. Six WMO Regional Specialized Meteorological Centres (RSMCs), devoted to tropical cyclones and operated by National Meteorological Services (NMSs), provide all countries with access to technical support, analysis and forecasts.

  • 2. How does WMO disseminate data relating to natural hazards to the communities concerned?

      • In the case of tropical cyclones, six WMO Regional Specialized Meteorological Centres (RSMCs) provide support for a specific region in the world. Atmospheric and oceanic data are collected via in situ and space-based instruments by the countries and transmitted through WMO’s Global Telecommunication System (GTS) to RSMCs, where round-the-clock forecasts and tropical cyclone advisories are developed. Advisories are then transmitted over the GTS, facsimile and Internet at intervals of three to six hours to the NMHSs of countries at risk. Forecasters use these advisories to produce national tropical cyclone warnings, which are dispatched immediately to newspapers, radio and television stations, emergency services and other users. Responsibility for issuing warnings rests with the NMS of the country concerned. In response to this information by decision-makers and disaster preparedness entities, many lives have been spared through timely measures, including evacuations. Beyond these natural hazards and through eight RSMCs, WMO supports its Members and international organizations in responding to large-scale transboundary environmental emergencies caused by major nuclear and chemical accidents, volcanic eruptions and wildfires. WMO is committed to the extension of (in an optimum and cost-effective manner, in collaboration with relevant national, regional and international organizations) its early warning competency and mechanisms to address hazards other than those of hydro-meteorological origin, such as tsunamis.

  • 3. Why is it that developing nations always seem to suffer most during extreme weather events?

      • Every year, natural disasters affect many communities around the world, leading to loss of lives, destruction of social and economic infrastructure and degradation of already fragile ecosystems. Such hazards are inevitable and can threaten everyone, but they tend to hit communities in developing and least developed countries the hardest, increasing their vulnerability and setting back their economic and social goals, sometimes by decades. While economic losses in dollars for developing countries are fewer than those for developed countries, impact (as a percentage of GDP) is often much higher. Many developing nations lie in tropical zones where extreme weather events such as tropical cyclones, droughts and flooding are more frequent than in other regions. Developing nations possess limited facilities and qualified human resources to monitor and predict these phenomena and provide warnings to all sectors of the population. Addressing this challenge is a major concern for WMO.

  • 4. How can WMO help developing nations better prepare for extreme weather events?

      • WMO and its Members provide assistance to reduce risks related to such events. This assistance includes providing meteorological equipment, training for meteorologists, hydrologists and climate forecasters; education and public outreach programmes; technical assistance for the issue of forecasts and warnings; as well as funding and workshops. The Organization also works closely with other agencies at international and regional levels to promote the concept of dissaster preparedness and prevention. WMO also contributes infrastructure and technical expertise towards the development of early warning systems for non-weather related hazards such as end-to-end tsunami early warning systems in the Indian Ocean and other regions at risk.

  • 5. How are hurricanes named and who names them?

      • Tropical cyclones (which can become hurricanes in the Atlantic and eastern North Pacific and typhoons in the western North Pacific) can last from a day to a couple of weeks. Therefore, there can be more than one tropical cyclone at a time in a same region. Weather forecasters give each tropical cyclone a name from the predesignated list of names so that the cyclone can be easily identified without confusion with others. The name lists are designated for every region by the tropical cyclone regional bodies such as the Hurricane Committee (for the Atlantic and eastern North Pacific) and the Typhoon Committee (for the western North Pacific). Each list has its unique character. In Atlantic basin, for example, women’s and men’s names are alternated. The first five names for the 2009 season in the Atlantic are Ana, Bill, Claudette, Danny and Erika and, in the eastern North Pacific, Andres, Blanca, Carlos, Dolores and Enrique. In the western North Pacific, a new system for naming tropical cyclones began in 2000. Each of the 14 nations affected by tropical cyclones submitted a list of names totaling 141. The names include those of animals, flowers, astrological signs and a few personal names are used in pre-set order. If a tropical cyclone causes serious death and destruction, its name is retired from use and replaced by a new name by the decision of the tropical cyclone regional body concerned.

        Read more about storm naming


  • 1. What is ozone?

      • Ozone is a form of oxygen whose molecule carries three atoms instead of two. Ozone is found both in the troposphere, i.e. the lower 10 km of the atmosphere and in the stratosphere (10-50 km above the ground). Ozone is our shield against harmful ultraviolet radiation from the Sun, so we need ozone in the atmosphere to protect us. However, ozone at ground level is a pollutant. It can trigger breathing difficulties for human beings and damage to plants and crops and is one of the major ingredients of smog. Whether ozone is “good” or “bad” therefore depends on its altitude in the atmosphere.

  • 2. What is happening to the ozone layer?

      • The ozone layer has been under attack from chlorine (chlorofluorocarbon, CFC) and bromine (halon) compounds abundantly used in the past in products such as aerosol spray, can propellants, refrigerants, pesticides, solvents and fire extinguishers. When these substances reach the stratosphere, the ultraviolet radiation from the Sun causes them to break apart and release chlorine and bromine atoms, which react with ozone. These reactions trigger chemical cycles of ozone destruction that deplete the protective ozone layer. It has been calculated that just a single chlorine atom can obliterate more than 1 000 000 ozone molecules. Bromine atoms however, are some 50 times more efficient at destroying ozone  but, fortunately, there are far fewer bromine containing compounds than CFCs in the atmosphere. Countries have been adhering to international agreements currently in place, such as the Vienna Convention and the Montreal Protocol and its Amendments. After peaking recently, the total amount of chlorine and bromine containing compounds in the stratosphere is now slowly going down, but it will probably take 50 years before the amount of chlorine and bromine is back at where it was before 1980 (roughly when the first Antarctic ozone hole was observed). Recent scientific reports show that ozone reduction has been less rapid in some regions of the globe, but it could take years before ozone starts to increase again.

  • 3. How does WMO monitor pollution?

      • WMO undertakes global long-term monitoring of air pollution around the world through the Global Atmosphere Watch (GAW) network, which consists of more than 300 stations that measure the amount of pollution (chemical and even nuclear) in the atmosphere. Data obtained are used to help assess the state of the ozone layer and climate change, and examine the effects on ecosystems and human health. Using models to discover how different types of pollution react in diverse weather patterns, WMO helps National Meteorological Services and other relevant agencies improve their public information products including air quality and UV index forecasts. Predictions provided by NMHSs concerning the transport of pollutants (nuclear, toxic substances, volcanic ash) allows for decisions to be taken for combating negative effects.


  • 1. What is the WMO vision for the evolution of its observing systems?

      • The WMO Vision of the Global Observing System provides high-level goals to guide the evolution of the Global Observing System in the coming decades. These goals are intended to be challenging but achievable. More information on the Vision of the GOS is available here.

  • 2. How do WMO members decide on the evolution of the global observing systems?

      • This is achieved through the Rolling review of Requirements (RRR) – see Question/Answer “What is the Rolling Review of Requirements (RRR)?” below

  • 3. What is the Rolling Review of Requirements (RRR)?

      • The Rolling Review of Requirements is a process aiming at providing WMO members with guidance for the evolution of the global observing systems addressing the needs of WMO applications. Experts review observational requirements in key WMO application areas (e.g. global NWP, seasonal to interannual climate forecasting, aeronautical meteorology, etc.), look at the current observing systems capabilities (both space-based, and surface-based), conduct a critical review (including impact studies in some cases), identify the gaps, and produce Statements of Guidance for each of the application areas. The statements of guidance are then reviewed, in the view to produce the Implementation Plan for the Evolution of global observing systems (EGOS-IP), a key document providing Members with clear and focused guidelines and recommended actions in order to stimulate cost-effective evolution of the observing systems to address in an integrated way the requirements of WMO programmes and co-sponsored programmes. More information on the RRR can be found here.

  • 4. Where are identified observational gaps documented?

      • After looking at the observational requirements, and the performances of space-based and surface-based observing systems, experts in each WMO application area conduct a critical review, and document the identified gaps in Statements of Guidance for those application areas. The Statements of Guidance can be found here.





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