G-P02 · TOPIC · climate-services-and-warningGCRI dossier · service level R0
GCRIClimate and HazardsIn development
Topic dossier · Climate and Hazards

Climate services and warnings

Climate services turn observations, forecasts and projections into information people can use: daily forecasts, seasonal outlooks, warnings and climate guidance for sectors. A warning only works if it reaches people in time, in a form they understand, and if they know what to do. This page sets out how services and warning systems are organized, how forecasts are verified, and what evidence serves the services and authorities that run them.

Systems · around this subjectDesign, not a record
Multi-hazard outlook: the screen's structure, terms and states for Climate services and warnings.Placeholder names and illustrative values; a design, not a record or a live system.

Fig.Multi-hazard outlook. Design wireframe with placeholder names and illustrative values, not a record or a live system.

01In brief

The short answer.

Climate services are the production and delivery of climate and weather information that people and organizations can act on, from forecasts and outlooks to warnings. A warning works only if it reaches people in time and in a form they understand. Authorised national services issue warnings, and verification shows how skilful they are.

02Geography

Hazards now in World.

For climate services and warnings, in GCRI's spatial-intelligence reading, the map opens on flood water, population density and true-colour imagery with a 15-day forecast chart at the centre, framed on World; 3 further NASA layers wait in the list.

The interactive map needs JavaScript; the layer list and sources are below.

Layers 3

Hazards now, for this page

Latest available

NASA GIBS / EOSDIS · ASTER GDEM (METI, NASA) · Blue Marble (NASA) · © OpenStreetMap contributors (ODbL) · Natural Earth

Loading the latest NASA imagery.

Drag to move. Ctrl or ⌘ and scroll, pinch or the buttons to zoom; hover for the values under the pointer; reset returns to the region.

For climate services and warnings, in GCRI's spatial-intelligence reading, the map opens on flood water, population density and true-colour imagery with a 15-day forecast chart at the centre, framed on World; 3 further NASA layers wait in the list.Satellite and model products as NASA publishes them, each with its own date; indicators, not assessments of any place; claim ceiling INTEGRATED.

Data: NASA GIBS · ASTER GDEM · Blue Marble · © OpenStreetMap contributors · Natural Earth · NASA EONET · GDACS · Copernicus Sentinel-2 L2ASources and licences

  • We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Science Data and Information System (ESDIS). Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • VIIRS near-real-time products (flood, land surface temperature, snow cover, corrected reflectance), NASA LANCE; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • Center for International Earth Science Information Network (CIESIN), Columbia University. 2018. Gridded Population of the World, Version 4 (GPWv4): Population Density, Revision 11. NASA Socioeconomic Data and Applications Center (SEDAC). Licensed under CC BY 4.0. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). CC BY 4.0
  • NASA Fire Information for Resource Management System (FIRMS), VIIRS 375 m active fire product, NASA LANCE; vector tiles via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • GPM IMERG precipitation, NASA Precipitation Processing System; distributed by the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • MODIS land products (vegetation indices, gross primary production, land cover), NASA LP DAAC and LANCE; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • ASTER GDEM is a product of METI and NASA (ASTER Global Digital Elevation Model V003, NASA LP DAAC); imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • Made with Natural Earth. Free vector and raster map data @ naturalearthdata.com. Public domain
  • © OpenStreetMap contributors (ODbL), via NASA GIBS (coastlines, boundaries, roads and place names). Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). ODbL
  • Blue Marble, NASA Earth Observatory; imagery via NASA GIBS. Colours redrawn from the published colour map; values averaged into H3 cells where shown (modified). NASA open data
  • Context on the globe and flat map: coastlines, boundaries, roads and place names from NASA GIBS reference layers (OpenStreetMap data, ODbL, © OpenStreetMap contributors); Blue Marble imagery as an optional base; 3D terrain and the elevation read-out from the ASTER GDEM elevation colour index (5 m to 200 m classes, exaggerated for legibility). Boundaries are drawn as published and imply no position on any territory.
  • Globe: MapLibre GL JS 6.9.1, BSD-3-Clause, © MapLibre contributors.
  • Live: NASA EONET Events are indicative, not official warnings.
  • Live: GDACS (EC JRC / UN OCHA) Events are indicative, not official warnings.
  • Observed (EO): Copernicus Sentinel-2 L2A (contains modified Copernicus Sentinel data 2026), Microsoft Planetary Computer
  • Optional layers (22 sources in the layer list: live, forecast, observed and context) print their provider credit on the map and here when switched on; forecasts are model output and derived indices are estimates.

Layers and dates

  • Flood water, 3-day composite: VIIRS Global Flood Product, NASA LANCE · 14 Oct 2026
  • Population density, 2020: Population: CIESIN, Columbia University, Gridded Population of the World v4.11 (2018), NASA SEDAC, CC BY 4.0 · static
  • True colour: VIIRS NOAA-20 corrected reflectance, NASA LANCE · 13 Oct 2026
  • Active fires and thermal anomalies, last day: VIIRS NOAA-20 375 m (FIRMS), NASA LANCE FIRMS · 13 Oct 2026
  • Precipitation rate, daily mean: GPM IMERG, NASA GES DISC · 12 Oct 2026
  • Land cover type (IGBP), yearly: MODIS Terra and Aqua land cover (MCD12Q1), NASA LP DAAC · 2024

03The question

Climate services and warnings: how the risk develops.

Forecast-to-user pathways and authority. The dossier below sets out how the risk develops, what is measured, where the data come from, how it is modelled and who decides.

Mechanism

Detection and forecasting

Observing networks, radar, satellites and numerical models detect developing hazards and forecast them. Lead time and skill vary by hazard, from days for cyclones to minutes for flash floods.

Mechanism

Impact-based warnings

Warnings that describe what the weather will do, such as roads flooding or buildings at risk, prompt more action than warnings that only give rainfall amounts or wind speeds.

Mechanism

The last mile

Warnings must reach everyone through broadcast, mobile alerts, sirens and community networks, in local languages and accessible formats. Gaps fall hardest on remote, poor and marginalised people.

Mechanism

Trust and response

People act on warnings they trust and understand. False alarms, unclear authority and conflicting messages erode trust, while drills and preparedness turn warnings into action.

04Key terms

Terms used on this page.

Each term as this page uses it. Where a standard-setting body defines the term, the wording follows that body.

TermDefinition
Impact-based forecastingForecasting that describes the expected effects of weather on people and assets.
Lead timeThe interval between a warning being issued and the hazard arriving.
Common Alerting ProtocolAn OASIS and ITU data standard for exchanging public warnings across channels.
05Indicators

What is measured, and how well.

Each indicator carries its unit, its cadence, the kind of source behind it and the evidence label a value would carry. No values are shown: a programme supplies them under its own authority.

IndicatorUnitCadenceSource typeLabel
Forecast skillcontinuous ranked probability skill score against a referenceper verification cycleForecast verificationOBSERVED
Warning lead timehours between warning issue and hazard onsetper eventWarning logs and event recordsOBSERVED
Population covered by multi-hazard early warningpercent of populationannualSendai Framework Monitor target GOFFICIAL
Warnings in Common Alerting Protocolpercent of warnings issued in CAPannualAlert feeds and WMO Register of Alerting AuthoritiesOBSERVED
False alarm ratioratio of warnings without the hazardper verification cycleWarning verificationOBSERVED
People who received and acted on a warningpercent of surveyed populationper surveyPost-event surveysREPORTED
06Canvas

From sources to decisions.

The topic as a computational graph: named sources feed the methods, an evidence review gates the outputs, and the decisions stay with the authorities that hold them.

Pipeline canvas · Climate services and warnings as a run graphDesign, not a record
Climate services and warnings: flood forecasting and warning chainRainfall forecasts drive a hydrological then a hydraulic model; inundation maps are compared with thresholds; the mandated authority issues the warning, it reaches people through every channel, and action follows. Design of the process, not a record of a run.

Fig. 02Nodes carry their type, two metric rows and a state; connectors show what feeds what; dashed frames name the owners; the timeline is the cadence. Design of the pipeline, not a record of a run.

07Sources

Where the evidence comes from.

Named public datasets and institutional records, each with its licence class. Sources by agreement are used only under their terms and never republished.

SourceWhat it givesLicence class
WMO State of Climate Services reportsStatus of climate services capacity by country and sectorPublic, WMO terms of use
Sendai Framework Monitor, target GNational reporting on early warning coverage and risk informationPublic, UN terms of use
WMO Register of Alerting AuthoritiesOfficial alerting authorities and their CAP feedsPublic, WMO terms
Early Warnings for All initiative reportsProgress on the four pillars of early warningPublic, terms per publishing agency
Copernicus Emergency Management Service early warning systemsEuropean and global flood, drought and fire forecastsFree, Copernicus terms
08Decisions

Who decides, and what the evidence serves.

Climate and Hazards prepares evidence. The decisions below are taken by the authorities named, under their own rules, and never by the platform.

Who decidesThe questionEvidence this page serves
National meteorological and hydrological servicesWhere to invest in observing, forecasting and warning capacityVerification results; service maturity profiles
Civil protection authoritiesHow warnings translate into protective action and evacuationWarning chain reviews; post-event surveys
Telecommunications regulatorsHow mobile networks carry public alertsWarning dissemination coverage; CAP adoption
Development partnersWhich early warning gaps to supportEarly Warnings for All pillar assessments

Outputs this topic produces

  • Verification summaries of forecast and warning performance
  • Warning chain reviews from detection to community response
  • Service maturity profiles against the Global Framework for Climate Services
  • Communication guides for impact-based warnings
09Core questions

What experts ask.

The questions follow information from forecast to action.

  • How skilful are forecasts at the lead times that matter for a given action?
  • Who has the legal mandate to issue a warning, and does everyone know who that is?
  • Do warnings describe likely impacts, not only weather, and say what to do?
  • Do they reach everyone at risk, including people without phones, in other languages or with disabilities?
  • What happens when a warning turns out to be a false alarm or a miss?
10Mechanisms

Mechanisms and drivers.

Forecast skill declines with lead time and varies by hazard: large-scale storms can be forecast days ahead, while intense local downpours are hard to pin down even hours before. Seasonal forecasts give probabilities, not certainties. Impact-based warnings combine hazard forecasts with exposure and vulnerability to describe what the weather will do, which people find easier to act on.

Warnings fail most often in the last mile: unclear authority, conflicting messages, messages that do not reach people, or advice that is impossible to follow. Trust is built over time, and repeated false alarms or missed events erode it. A single authoritative voice, consistent messages and clear actions are widely recognized as essential.

11Methods and data

How it is studied, and where the methods stop.

Method or dataWhat it showsLimits
Forecast verificationSkill, reliability and bias at given lead timesRare extremes give few cases for verification
Warning chain and stakeholder mappingWho issues, relays and acts on warningsFormal arrangements may differ from practice
Post-event reviewsWhether warnings were received, understood and acted onRely on recall and partial data
Social and behavioural researchWhy people do or do not actFindings are context-specific
12Methods

How it is studied, and what the methods cannot say.

  1. Forecasting and time-series analysisEnsemble forecast interpretation · Seasonal outlook use · Forecast verificationApplied here
  2. Climate and atmospheric scienceDetection and attribution of change · Extreme event attribution · Process-based model evaluationApplied here
  3. High-performance, cloud and edge computingRunning and storing ensembles · Analysis near the data · Edge processing for observationsApplied here
  4. Space systems and satellite servicesObservation continuity planning · Satellite communications for warningsApplied here
13Questions

Questions and answers.

What is an impact-based forecast?
A forecast or warning that describes the expected effects of a hazard on people and assets, such as flooded roads, rather than only meteorological values.
What is the Common Alerting Protocol?
An international data standard for public warnings, maintained by OASIS and adopted by ITU, that lets one warning be sent consistently across many channels.
Who issues official weather warnings?
The national meteorological and hydrological service or another authority designated by law. Other sources should point people to those official warnings.
Why do warnings need a single authoritative voice?
Because conflicting messages cause confusion and delay. Recognized warning authorities exist so that people know whose information to act on.
What is an impact-based warning?
A warning that describes the expected effects of a hazard, such as flooded roads or power cuts, and what people should do, rather than only the weather values.
Does Climate and Hazards issue warnings?
No. It studies how warning systems work and publishes research. Warnings come from competent national and local authorities.
Climate and Hazards

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