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The climate science community has developed an extensive set of requirements to meet the needs for climate observations. For some variables, new observational techniques will have to be developed and employed. For others, it is possible to utilize existing observing capability. Additional effort is required to produce satisfactory climate data records from operational data. We recommend a re-dedication of our national efforts to develop and to sustain the essential components of a comprehensive global observing system, involving oceanic, atmospheric and land-based (ecosystems and land cover) elements capable of meeting climate requirements.

Over the past decade a number of basic principles have been developed for the delivery of long-term data with minimal space- and time-dependent biases. A 1999 NRC study Adequacy of Climate Observing Systems addressed the adequacy of the climate observing system and endorsed a suite of climate monitoring principles. These principles are critical for climate observations, and have also been endorsed by the United Nations Framework Convention on Climate Change, and in the recommendations for a Global Climate Observing System (GCOS). Briefly described the NRC recommendations include:

a. Management of Network Change: Assess how and the extent to which a proposed change could influence the existing and future climatology.

b. Parallel Testing: Operate the old system simultaneously with the replacement system.

c. Metadata: Fully document each observing system and its operating procedures

d. Data Quality and Continuity: Assess data quality and homogeneity as a part of routine operation procedures.

e. Integrated Environmental Assessment: Anticipate the use of data in the development of environmental assessments.

f. Historical Significance: Maintain operation of observing systems that have provided homogeneous data sets over a period of many decades to a century or more.

g. Complementary Data: Give the highest priority in the design and implementation of new sites or instrumentation within an observing system to data-poor regions, poorly observed variables, regions sensitive to change, and key measurements with inadequate temporal resolution.

h. Climate Requirements: Give network designers, operators, and instrument engineer's climate monitoring requirements at the outset of network design.

i. Continuity of Purpose: Maintain a stable, long-term commitment to these observations, and develop a clear transition plan from serving research needs to serving operational purposes.

j. Data and Metadata Access: Develop data management systems that facilitate access, use, and interpretation of data and data products by users.

The United States actively supports the Global Climate Observing System (GCOS) through its participation in and support of the GCOS networks, and through its support of related climate observing activities. The United States recognizes that international cooperation both in the data collection and sharing of the information is essential to provide the climate information required by the United Nations Framework Convention on Climate Change.

A systematic inventory of the U. S. climate related observing systems was just completed. A comprehensive report was prepared as directed by UNFCCC Decision CP/1999/L.3 [PDF], which requested all Annex I Parties to provide a detailed report on systematic observations in accordance with the UNFCCC reporting guidelines on global climate change observing systems adopted by UNFCCC Decision CP/1999/L.4. The principles of this report are based on the climate observing requirements for observing networks, practices, and data management as agreed to internationally in documentation such as "The Plan for the Global Climate Observing System (GCOS)," Version 1.0, May 1995 GCOS-14 (WMO/TD-No. 681). [PDF]

An essential set of baseline climate reference surface stations will be accelerated and enhanced in the US and in all countries. They will provide high priority surface climate measurements and include temperature, precipitation, cloud cover, humidity, soil moisture, and ground temperatures. The GCOS (sponsored by WMO, IOC, UNEP, and ICSU) has identified a GCOS Surface Network (GSN) of approximately 1000 locations worldwide where observations are required for climate monitoring. These stations provide a baseline for global change, and will further serve as calibration/validation sites for space-based retrievals of surface climate measurements. This will both enhance the regional coverage of key climate parameters from in situ data and allow expansion of surface data to the global scale.

The GCOS Upper Air Network (GUAN) consists of about 150 stations selected to produce a homogeneous global distribution. The stations, which are a subset of the larger WMO World Weather Watch Global Observing System, are intended to meet both weather and climate objectives. The network provides global fields of key climate parameters (e.g., temperature, humidity, and winds) and is crucial to supporting both the monitoring of the climate system and the research needed to understand its variability and ultimately to make climate predictions.

At present greenhouse gas sampling principally involves clean maritime air collected at surface sites. Atmospheric CO₂ sources and sinks are estimated by global models that rely on such observations and consequently these estimates are poorly determined. Over the next 3-10 years, global satellite retrievals of column CO₂ are expected to become increasingly quantitative and help improve flux estimates. We will exploit available synergies that could be obtained by simultaneously measuring compounds such as CO₂, tropospheric ozone, and aerosols.

The WMO Global Atmosphere Watch (GAW) currently consists of a global array of about 20 comprehensive stations and about 380 more specialized observing sites at which only very limited measurements of atmospheric constituents are made. Four of the GAW sites are operated by the US.

Shortcomings

While the national system has made a start in the design and operation of a climate reference network, the GCOS experience to date indicates that developing countries in particular have often been unable to maintain the observing schedules, or to transmit the information effectively. Approximately half the global network does not meet the observing and reporting protocols.

Monitoring reports consistently indicate that only about two thirds of the stations are fully or partially compliant with the observing and reporting requirements. These inadequacies have led to large uncertainties in trends of tropospheric temperature and humidity in particular.

The global network is currently adequate to characterize global, long-lived, greenhouse gas levels, but inadequate to determine sources and sinks at less than global scales. In all cases, the network of in situ measurements is inadequate for climate attribution studies. Long-lived greenhouse gases are not measured adequately over continents as analyses of model sensitivity show. However, local meteorology and sources make interpretation of continental surface concentrations alone quite difficult. Future satellite measurements of column-integrated CO₂ require enhanced modeling skill. Furthermore, satellite measurements will need ground-truth to ensure that apparent gradients and fluxes are not spurious.

The emissions producing ozone and aerosols are poorly known, especially in regions like Asia, where they are expected to increase rapidly with industrialization. Sampling and interpretation of pollutant emissions have not been adequate, and simulation of the processes controlling ozone and aerosol must improve in order to recommend reasonable amelioration. The three-dimensional distribution of tropospheric ozone is not well understood, and location is a large factor of its deleterious effects. Continuous measures of volcanic aerosol amounts in the tropical stratosphere are not in place to sample the effects of the next climate-altering eruption. The tropospheric ozone distribution is not adequately described by current networks, which are spotty in time and space.

Proposed Strategy

• Working with international organizations and through bilateral agreements, provide additional support for instrumentation for observations and for training of technicians in developing countries. Support regional working groups and initiatives such as the GCOS Regional Workshop Program aimed at designing and developing national contributions to the observing systems. Accelerate the installation of a US climate reference network and ensure that all high priority surface climate measurements are included in the network.

• Place new WMO Global Atmosphere Watch (GAW) in priority sites to measure pollutant emissions in specific regions (e.g., at islands downwind from Asia with instrumentation to measure relevant tropospheric compounds such as ozone, aerosol compounds and precursors, soot and optical effects, and tracer gases, carbon monoxide and organics). Add new stations to measure aerosol and ozone in poorly sampled regions of the globe.

• Work in conjunction with international partners to reestablish and support the benchmark upper-air network for the long-term. The US should particularly address stations located in data-sparse areas (e.g., remote islands, Latin America, Africa) to ensure the supply of expendables, communication equipment, and training for technical staff and should work with other countries to establish a system which would ensure the continuation of such support. Increase support for the national and international surface and free-air sampling programs.  New instruments to directly measure free tropospheric values of greenhouse gases from the ground and from aircraft need to be developed as well as those to determine isotopic composition of CO₂ without requiring an air sample. For example, the upward looking infrared spectrometers technology developed for stratospheric work can be applied to obtain accurate column-integral CO₂; it should simultaneously measure other species.  Ancillary measurements, including of the variable effect of humidity in diluting CO₂, and measurements of carbon monoxide, nitrous oxide, and methane will be available and very useful. Installations may be staged, starting in South and North America. A combination of in situ measurements with sufficiently accurate satellite measurements will be required for future work on global sources and sinks. Surface networks should be coordinated and inter-calibration improved. CO₂ measurements should be coordinated with studies of the intercontinental transport and buildup of other active greenhouse pollutants.

Ongoing plans and activities

The present status and immediate future plans regarding these observing systems are compiled by the National Oceanic and Atmospheric Administration on behalf of the United States Government. The report was published in August 2001 under the title: "The United States detailed National Report on Systematic Observations for Climate: United States Global Climate Observing System (US-GCOS) Program". [PDF]

Deliverables

Complete internationally sponsored global networks for surface and upper air measurements.

The ocean's role in the climate system includes both storage and transport; the ocean is the main memory of the climate system and is second only to the sun in effecting variability in the seasons and long-term climate change. We need to determine whether the thermohaline circulation is slowing, as some models predict, whether El Niño is looming, and to map other regional changes of vital interest to the health of the ocean. The ocean is both source and sink for CO₂ and contains 50 times more carbon than the atmosphere. Sea level change is one of the most important consequences of climate change; it impacts essentially every coastal nation. Accurate observations are needed as data for climate models, for determining the present rate of change in ocean structure and for alerting us to any unforeseen changes in ocean circulation with potential climate impacts. It is anticipated that there will be future needs for tracking of additional variables (e.g., nutrients, ocean blooms, phytoplankton, pollution, dissolved CO₂ and other trace constituents).

Shortcomings

An observing system that can accurately document climate-scale changes in ocean heat, carbon, and sea level change is not in place. Currently, it is estimated that the ocean observing system, based in large part on research programs, is providing only a fraction of what is needed. Some effective subsystems have recently been developed to monitor some aspects of the ocean, the most notable being the TAO array of moored buoys in the Pacific Ocean. Major issues remain in better determining fields of sea surface temperature and surface fluxes. There is also a crucial need to systematically provide continuous, three-dimensional fields of variables for the ocean: heat content, salinity and currents. Knowledge of the distribution and changes in the heat storage in the upper ocean (above the thermocline) is a key element in understanding why observed climate variations at the surface have occurred. Sea ice is very important to climate change. Areal extent can be monitored from space but thickness, mass and volume are in situ tasks, and data are not routinely available. The requirements for ocean observations for climate have been well documented, the relevant technology is available, and the international community is mobilized through GCOS and the Global Ocean Observing System (GOOS) to implement key elements of the system.

Proposed Strategy

Current initiatives include arrays of autonomous drifting floats at the surface and profiling instruments at depth, moored arrays for temperature, salinity, and currents, tide gauge stations, and observations from ships which need to be extended to all oceans; proven satellite missions (e.g. altimetry, scatterometry, ocean color, precipitation, sea surface temperature, etc.) which need to be continued in both research and operational modes, and systems of data assimilation (initially via the Global Ocean Data Assimilation Experiment, GODAE) and analysis which also require considerable resources. Initially a goal should be to adequately determine upper ocean fields on a monthly basis although some users require weekly or higher frequency data. Other major parts of the ocean vary slowly and need less frequent observations. The deep ocean, for example, needs annual or perhaps 5-yearly observations. Ocean station time series at a few key locations can help in monitoring physical climate as well as carbon. Continued investment in telecommunications and information technology is essential to ensure the timely delivery of critical ocean climate data.

Ongoing plans and activities

The present status and immediate future plans regarding these observing systems are compiled by the National Oceanic and Atmospheric Administration on behalf of the United States Government. The report was published in August 2001 under the title: "The United States detailed National Report on Systematic Observations for Climate: United States Global Climate Observing System (US-GCOS) Program".

Deliverables

The terrestrial components of the observing system measure hydrological, cryospheric, and ecosystem variables, many through the Global Terrestrial Observing System (GTOS). A global observing capability for atmospheric and hydrologic variables uses satellite and in situ systems to support interannual and decadal studies. Water cycle observations are currently poorly coordinated. Given the importance of water for understanding climate forcing and variability, and the strong coupling that exists between the land, ocean and atmosphere it is necessary that elements of the terrestrial observing system be considered in a fully integrated fashion. The largest variations over land occur through the amount of moisture in the soil and such variations are vitally important to agriculture and climate. In particular, hourly precipitation and daily soil moisture fields from surface and space-based indicators are required. Hydrological observations also include surface and groundwater, river flows, lake levels, and related variables. Cryospheric variables are collected as parts of glacier and permafrost networks, both requiring additional sampling sites to be more representative. At present, a comprehensive system to observe elements of the global water cycle is just being implemented. Ecosystem observations are made through a small number of comprehensive sites and a larger number of more specialized locations. For example, the Global Observation of Forest Cover (GOFC) program is an international initiative under GTOS to secure the necessary satellite and in-situ land cover related observations in support of global change research and natural resource management. GOFC supports global assessments of carbon and ecosystems in three implementation areas: land cover, fire, and biophysical observations through better articulation of the observation requirements, determination of the accuracy of satellite data products through a network of validation sites, and improved access to data and information products tailored to support decision and policy making.

Shortcomings

The GTOS involves a large and disparate community. Many individual observing components are being developed, but international participation is not adequate to meet the requirements. The US lacks a federal focal point for terrestrial climate observations to coordinate the disparate observational activities underway in the various federal agencies.

Proposed Strategy

The US should take a lead role in developing those observing system components that are of highest priority to meet climate needs. These include aspects of the Global Terrestrial Networks for glaciers (GTN-G), permafrost (GTN-P), ecosystems (GTN-E), and global forest cover (GOFC). The US agencies will coordinate their observing activities more effectively.

Ongoing plans and activities

The present status and immediate future plans regarding these observing systems are compiled by the National Oceanic and Atmospheric Administration on behalf of the United States Government. The report was published in August 2001 under the title: "The United States detailed National Report on Systematic Observations for Climate: United States Global Climate Observing System (US-GCOS) Program".

Deliverables

US leadership is needed to implement a suite of terrestrial observing components to obtain crucial measurements of terrestrial variables related to carbon cycles, surface hydrology (including precipitation, evaporation, runoff, stream-flow and soil moisture), ecosystems, and the cryosphere (including snow cover, glaciers, and permafrost).

The US operates an extensive space-based, remote sensing observation program for elements of the atmosphere, ocean, terrestrial systems, and climate forcing. Satellites provide the primary means of obtaining a global perspective and comparing different parts of the globe. A comprehensive global climate record is not practicable without a major satellite component, but challenges remain in mission continuity and data quality regarding artificial changes from orbital and calibration modifications. The satellite observations, together with complementary in situ observations, aim to provide essential information on how climate is varying and changing.

Shortcomings

The science community has identified key issues with constructing long-term climate records from satellite observations. Thus far the most prominent record has been the one constructed from the MSU (Microwave Sounding Unit) temperatures, but even those have undergone major revisions and further substantial revisions are being reported. Follow-on satellite missions often have a somewhat different orbit and different time-of-day sampling. Orbits decay unless continually boosted, and there is substantial drift in the time of observations for polar orbiting satellites. In the past, instrument calibrations have been altered by the launch and the space environment, and measurements have been affected by other instruments and the platform.

• Satellite missions intended for climate monitoring would be launched into stable orbits designed to minimize drift in time of observation to within 2 hours over the lifetime of the satellite, and/or utilize boosters to stabilize the orbit.

• Sufficient satellites will be operating to enable adequate sampling of the diurnal cycle. Satellites would be launched on schedule, rather than on failure of the previous mission, to ensure overlap of measurements, which is essential for the climate record.

• All instruments would require pre- and post-launch calibration and the existence of a sustained in situ network for an extensive ground truth validation. Resources are needed to improve telecommunications and telemetry capacity.

Ongoing plans and activities

The present status and immediate future plans regarding these observing systems are compiled by the National Oceanic and Atmospheric Administration on behalf of the United States Government. The report was published in August 2001 under the title: "The United States detailed National Report on Systematic Observations for Climate: United States Global Climate Observing System (US-GCOS) Program".

Deliverables

• US leadership to develop and deploy instruments with improved calibration and validation, and to disseminate the critical global observations that will result.

• Development of innovative instruments that have demonstrated promising capabilities, such as those based on GPS technologies, and instruments for carbon observations in the atmosphere and the sea surface; aerosol distribution, properties, and cloud interactions; and global land surface characterization including forests, managed ecosystems, and the cryosphere.

Climate reference data set development work is a key step in understanding the observed climate record. Observations relevant to climate have been collected for various other purposes, and may not meet climate monitoring standards. Once the data are collected they often require calibration using appropriate standards, careful and systematic analysis and sometimes, ‘data archeology' to produce a reliable time series to detect climate change and attribute these changes to specific causes. In addition, observational uncertainties are required so they can be considered in evaluating the record. Ultimately, the data must be able to represent the true nature of observed changes and variations. In addition to developing climate-relevant data sets, the number one priority for many scientists and decision-makers is access to global data. Data products such as time series based on proxy paleoclimatic date and other data are of prime relevance to climate change.

Shortcomings

Data management and related information services require resources but are often overlooked when programs are planned and implemented. Data volume is expected to increase dramatically, creating challenges of archival, maintenance and effective access to the data.

Proposed Strategy

• Develop indicators and provide reports on monitoring the health and performance of the climate observing system,

• Develop and institute consistent and well-designed data management practices to ensure the delivery climate-relevant data of immediate consequence and utility. Additional resources will ensure consistent data management across the broad range of climate variables, value-added data sets, and model products,

• Implement climate data assimilation and periodic reanalysis, and develop operational capabilities, including new model-based analyses of the ocean and land surface as well as for the atmosphere, and

• Enhance the capability to deliver climate change relevant data and information to the user community through existing climate extension service programs at the national, regional and state level (e.g., NOAA Regional Climate Centers, American Association of State Climatologists Recognized State Climate Offices, NOAA/NWS field offices, and other federal agencies such as FEMA, USDA, and DOI).

Ongoing plans and activities

The present status and immediate future plans regarding data and information management issues have been compiled by NOAA. The report was published in August 2001 under the title: "The United States detailed National Report on Systematic Observations for Climate: United States Global Climate Observing System (US-GCOS) Program".

Deliverables

• Improved climate record by ensuring the integrity and continuity of the observations, their analysis into products, and links to modeling and research activities; and

• Maintenance of the climate record by state-of-the-art systems for data archival and access.