Climate Observing Systems: Data System Challenges

Existing observing and data systems have provided considerable information about past climate variations and changes. The recent reports by the Intergovernmental Panel on Climate Change, the National Research Council, and the USGCRP National Assessment of Climate Variability and Change are testaments to a vast array of knowledge. These reports also expose some serious deficiencies in our ability to discern past climate variations and change which lead to substantial uncertainties in key climate state, climate feedback, and climate forcing variables. How significant are these uncertainties? For climate trends that have our highest confidence, like the change in mean global surface temperature, the 95 percent confidence intervals amount to about two-thirds of the calculated change. With such large uncertainties it is exceedingly difficult to discern accelerated changes. For other variables, especially variables related to climate feedbacks and forcings (with exceptions for long-lived and well-mixed greenhouse gases like CO₂ or CH₄) or climate and weather extremes, we often have little or no information to discern trends or cannot objectively assess confidence intervals. Do we know how to reduce existing uncertainties? First and foremost, a climate observation oversight and monitoring capability is needed that tracks the gathering of the data, the processing system, and the performance of the observations, especially time-dependent biases. An organized capability does not now exist, but could be developed at a new and/or existing centers. This center(s) should then have the means and influence to fix problems and be able to establish requirements for new in-situ and satellite observing including related data systems. Such a capability should complement the following: (1) Climate observations from both space-based and in-situ platforms that are taken in ways that address climate needs and adhere to the ten principles outlined by the NRC (1999 Adequacy of Climate Observing Systems) and GCOS. An international framework is vital. (2) A global telecommunications network and satellite data telemetry capacity to enable data and products to be disseminated. (3) A climate observations analysis capability that produces global and regional analyses of various products for the atmosphere, oceans, land surface and hydrology, and the cryosphere. (4) Four dimensional data assimilation capabilities that process the multivariate data in a physically consistent framework to enable production of the analyses, not just for the atmosphere but also for the oceans, land surface and so on. (5) Global climate models that encompass all parts of the climate system and which are utilized to design effective sampling strategies and evaluate observations. These improvements primarily relate to the data system, after the observation has been made, but they must be accompanied with a concerted effort to improve our instrumentation, platforms, and sampling resolutions for key climate variables. How much would such a data system cost? Practical experience has shown that an effective archive and access system can be designed for about 5 to 10 percent of the total cost of the observing system. Building on a solid investment in data management infrastructure and hardware (including data quality control, access, and long-term stewardship), a comparable investment would be required to address oversight, monitoring, data analysis, data assimilation, and adherence to the ten principles. An implementation time frame on the order of five to ten years is probably a realistic time frame, similar to the planning and implementation horizon of major new observing systems.