Status of the Global Observing System for Climate

by Global Climate Observing System Secretariat 

The Plateau Rosa Global Atmospheric Watch (GAW) station, Italy 

Global observation of the Earth’s atmosphere, ocean and land is essential for identifying climate variability and change, and for understanding their causes. For example, recent observations and analyses have shown that global mean sea level has continued to rise, and it has been possible for the first time to identify the relative importance of the contributions from thermal expansion, melting ice and the storage of water on land.

Observation also provides data that are fundamental for evaluating, refining and initializing the numerical models that predict how the climate system will vary over the months and seasons ahead, and that project how climate will change in the longer term under different assumptions concerning greenhouse gas emissions and other human influences. Long-term observational records have enabled the Intergovernmental Panel on Climate Change (IPCC) to deliver the message that warming of the global climate system is unequivocal.

This article highlights the main finding and conclusions of the Status of the Global Observing System for Climate (Report)1, published in late 2015. The Report offers an extensive account of how well climate is currently being observed, where progress has been made, where progress is lacking or where deterioration has occurred. It provides a basis for identifying the actions required to reduce gaps in knowledge, to improve monitoring and prediction, to support mitigation, and to help meet increasingly urgent needs for information on impacts, adaptation and vulnerability.

The Status Report was prepared by the Global Climate Observing System (GCOS), a co-sponsored programme of WMO, the Intergovernmental Oceanographic Commission (IOC) of the United Nations Educational, Scientific and Cultural Organization (UNESCO), the United Nations Environment Programme (UNEP) and the International Council for Science (ICSU).

This article highlights the main finding and conclusions of the Status of the Global Observing System for Climate (Report), published in late 2015. The Report offers an extensive account of how well climate is currently being observed, where progress has been made, where progress is lacking or where deterioration has occurred. 

Finding on atmospheric, oceanic and terrestrial observations

Global observation varies in its nature, arrangement and extent across the atmospheric, oceanic and terrestrial domains. Owing to the heritage of many decades of meteorological data collection, atmospheric observation is the best developed, with relatively dense though far from gap-free networks, clear observational standards, largely open data exchange and international data centres covering most, if not all, variables. Refinement of atmospheric observation is ongoing.

Ocean observation has developed quickly, with international planning and implementation of observational networks, and new technologies that enable more and better autonomous data collection. While there are still limitations and some issues with established networks, overall structures are in place for the improvement to continue. 

The Providence FluxTower, Southern Sierra, California, USA 

Terrestrial observations have traditionally been made on smaller scales, with different standards and methods in different countries. They also have a poor history of open data exchange. Space-based observation is now providing global coverage of improving quality for a number of variables, increasingly with open data access, and there is progress in other areas, through global networks for glaciers and permafrost, for example. Standards, methods and data-exchange protocols for key hydrological variables have been developed. However, an integrated approach to terrestrial observation is still lacking.

Most of the principal findings that have been drawn from the reviews that were undertaken variable by variable and action by action fall straight forwardly into two separate groups, one for in situ measurement and ground-based remote sensing and one for space-based remote sensing, even though many applications of observations make combined use of both groups of data. There are both positive and negative findings, and both need to be acknowledged and taken into account when planning what needs to be undertaken in the future.


For the in situ and other non-space-based components of the observing system, the following is found:

  • The development and contribution to climate monitoring, understanding and prediction of the Argo network since floats that profile temperature and salinity were first deployed in 2000 have been outstanding. The original goal of 3 000 floats was reached in 2007. The network is now expanding into marginal seas and high latitudes. It is beginning to host sensors that measure biogeochemical variables and offers the prospect of profiling to greater depths. 
  • There have been improvements in coverage, and quality of measurements, for a number of longer established in situ networks, including the main meteorological networks.
  • Several oceanic and terrestrial in situ measurement networks and ground-based remote sensing networks for atmospheric composition have been established or significantly expanded in recent years, but some requirements for forming such networks have not been met.
  • Some atmospheric-composition and marine-buoy networks have provided fewer observations recently due to planned closures, inadequate maintenance or unexpected equipment failures. Responses have been effective in limiting some of the shortfalls. Particular issues with moored-buoy networks have prompted a review of the observing system for the tropical Pacific.
  • Surface meteorological measurements from ships have declined in number over major parts of ocean basins, but have increased near coasts. 
  • Some gaps in the coverage of networks over land have been reduced. Local gaps that appear small from a global perspective may nevertheless be critical, especially where populations are at risk or where local changes have global impacts.
  • Capacity development continues to fall far short of what is needed to fill critical network gaps in a sustainable way, and more generally to ensure that vulnerable developing countries have the local observations needed to adapt to climate change.
  • Automation has increased the temporal frequency of observation, and has enabled measurements to be made at additional remote locations, but certain issues relating to data quality and loss of ancillary information remain outstanding.
  • Progress in specifying and establishing reference observing sites and networks has been mixed: good for upper-air measurements but attaining representative global coverage is a challenge.
  • There are opportunities to benefit from expanding global near-real-time data exchange and from adopting new reporting codes and metadata standards. 
  • Recovery of historical data has progressed in some respects, but it is still limited in extent and hampered by restrictive data policies.
  • Generation of data products, for example, on surface air temperature, humidity and precipitation, continues to improve.
  • Sustaining observing-system activities that are initiated with short-term research funding is a recurrent issue.

For the space-based component of the observing system, the following ndings are reported: 

  • The newer and planned generations of operational meteorological satellite systems offer improved quality and a broader range of measurements. China is becoming established as the provider of a third pillar in the constellation of polar-orbiting systems. 
  • The European Copernicus programme is placing additional types of observation on an operational basis, with increased coverage and quality of measurement, and accompanying service provision.
  • There have been increases in the numbers of national providers, cooperative international missions and other collaborative arrangements.
  • There has been very little progress on the continuation of limb sounding (when the instrument looks sideways at the limb of the Earth rather than downwards, which is referred to as nadir sounding in the case of a sounding instrument) and the establishment of a reference mission.
  • Continuity of observation is at risk for measurements of solar irradiance and of sea-surface temperature at microwave frequencies.
  • New observational capabilities have been demonstrated, and others are being prepared for demonstration. Future deployment is uncertain for some of the demonstrated capabilities, for example, for monitoring cloud and aerosol profiles, sea-ice thickness and soil moisture.
  • The generation and supply of products derived from space-based observations have progressed with increasing attention paid to documenting product quality and uncertainty.
  • Inter-agency cooperation has been effective in product validation and in starting the development of architecture for climate monitoring from space and an inventory of products.
  • Data access is becoming more open, but further progress is required. Some data remain to be recovered from early missions, and long-term preservation of data, including occasional reprocessing, is not yet fully ensured.

Data-centre holdings are increasing with the passage of time, and are generally distributed by data type. International data centres hold collections of in situ data for many but not all essential climate variables. Basic satellite data are usually held by the agency that operated the satellite. Derived data products are hosted primarily by the organizations that generated the products. This arrangement is not seen to be problematic, but the Report outlines a few concerns. 


Launch of an Argo float, Indian Ocean 

Reanalysis of data

Global reanalysis of comprehensive sets of observations has been sustained with improving capabilities and better understanding of user requirements and difciencies in current products.The activity is being placed on a firmer footing in Europe, through inclusion in operational Copernicus service provision, and in Japan and the United States of America, through the commitment of providers to continue and refresh production.

Atmospheric reanalysis for the radiosonde and satellite eras has been supplemented by reanalysis covering the twentieth century and more, assimilating only surface atmospheric data but constrained also by observationally based surface and radiative forcings. Reanalysis has become better established for the ocean, the land surface and atmospheric composition. Good progress has also been made in the development of data-assimilation systems that couple various elements of the climate system, the atmosphere and the ocean in particular. 

International coordination

International organization of observing systems has been strengthened, especially for the atmosphere and ocean, through the development of the WMO Integrated Global Observing System and the revitalization of the IOC-led Global Ocean Observing System. The withdrawal of support for the GlobalTerrestrial Observing System by its lead sponsor has restricted coordination and standardization for the terrestrial domain, but many individual elements of terrestrial observation have progressed.

Further conclusions concerning overarching and cross-cutting topics, and topics specific to the atmospheric, oceanic and terrestrial domains, are presented in the full Report. It is also presents a general indication of progress over the past five or so years by assessing the accomplishment of the actions set out in the 2010 Implementation Plan for the Global Climate Observation System.

To conclude, many countries have improved the contributions that they or their intergovernmental agencies make to the global observing system for climate. The system continues to progress and support better the needs of an increasingly wider user community. With the passage of time, the length of the modern instrumental data records is extending and improving – for recent years by better observations and for earlier years by recovery and better reprocessing and reanalysis of data. However, the system nevertheless continues to fall short of meeting some essential requirements for observationally based climate information, which anthropogenic climate change makes ever more urgent. What needs to be done will be addressed in the forthcoming new implementation plan that GCOS is preparing for publication later in 2016.

We invite readers to consult the Report for a fuller picture of the progress that have been made over recent years, but also to get a better understanding of how much work remains to be done. 

International organization of observing systems has been strengthened, especially for the atmosphere and ocean, through the development of the WMO Integrated Global Observing System and the revitalization of the IOC-led Global Ocean Observing System. 


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