Review of NASA's Earth Science Enterprise Research Strategy for 2000-2010 (2000)

In particular, the five ESE research themes (oceans and ice, ecosystems, atmospheric chemistry, global water and energy cycle, and solid-Earth science) are directly applicable to the first three issues—variability, forcings, and feedbacks—although they are less well matched with the fourth and fifth issues, consequences and predictions. The primary science issues (Table 2) are given priority in planning the ESE program. The primary science issues are also consistent with the objectives of the USGCRP (Table 2) and with the spirit of the integrated Earth system science approach adopted previously by NASA and reiterated by the NRC report Global Environmental Change: Research Pathways for the Next Decade,⁸ referred to here as the Pathways report. The committee believes that addressing these primary science issues establishes a firm foundation for the Earth Science Enterprise.

Because the primary science issues listed in Table 2 are too broad to guide implementation, NASA has also formulated 23 detailed science questions (see Table 3). The Plan's discussion of these questions includes both the scientific rationale for the questions and the quantities (parameters, implementation details, technical readiness, operational potential, and partnership potential) needed to answer them. The committee's analysis of the soundness of the selection of the detailed questions, and their consistency with recommendations made in NRC reports⁹,¹⁰,¹¹,¹²,¹³,¹⁴,¹⁵,¹⁶,¹⁷,¹⁸,¹⁹,²⁰,²¹,²²,²³ is given below.

The first recommendation of the Pathways report is that “. the USGCRP strategy should be centered on sharply defined and effectively executed programs and should recognize the essential need for focused observations, both space-based and in situ, to test scientific hypotheses and document changes” (p. 521). All the detailed ESE questions related to Earth system variability and trends concern documenting change, and all are responsive to various relevant NRC reports (see Table 3). However, several key aspects integral to understanding the basic state of the Earth system, and Earth system variability and change, are missing. For example, question V2 deals with changes in the global ocean on climatic time scales, but not changes in the atmosphere, land, or sea ice. Similarly, question V4, which deals with changes in stratospheric ozone, does not mention tropospheric chemistry trends, even though it is a major research emphasis within the ESE. Variability in ecosystems and in chemical systems is not explicitly discussed. Finally, the dominant climate modes (i.e., El Niño/Southern Oscillation, Pacific (inter)Decadal Oscillation, North Atlantic Oscillation) are treated in a fragmentary manner without a clear strategy for putting the pieces together, as required in an Earth system science approach.

The table in the Plan associated with these detailed questions (Table 4.1) identifies remotely sensed quantities, but in situ measurements are almost always required to completely answer Earth science questions. For example, remote sensing measurements are not sufficient to document changes in the global ocean circulation (question V2), for which in situ measurements are essential. Identifying the complementary observations for addressing questions V1-V6 would be a useful addition to the next version of the Plan.

The construct of forcing and response leads to a set of questions that are broadly consistent with recommendations made in several NRC reports (Table 3). However, it also emphasizes questions that deal with relatively long time scales, an approach that eliminates most issues of natural Earth system variability on seasonal-to-interannual and decadal-to-centennial scales. Thus, the forcing-related questions address long-term changes in solar radiation, atmospheric constituents, land-use changes, and landform-surface changes. The response-related questions focus on the longer-term responses of clouds, ecosystems, the deep ocean, the stratosphere, the polar ice sheets, and air quality. There is, however, no mention of forcing due to volcanoes, which is relevant to atmospheric chemistry and understanding the Earth system.

Some of the questions, particularly questions related to Earth system responses and feedback processes, should be stated in more general terms. Questions R3 and R5, in particular, could be answered “yes ” now. Yet, the issues encompassed by these questions are important and should be captured in the phrasing. Question R5 would be better posed as a query regarding sea level rise in response to long-term climate change, wording that would imply the study of ocean warming and related sea level rise, as well as changes within the cryosphere as a function of time and space. Question R3 could be rephrased to focus on processes.

The shift in focus from short-term measurements, which NASA has traditionally emphasized, toward long-term monitoring, which NASA has not interpreted as part of its mission, appears to be intentional (see “NASA's Responsibility for Answering the Detailed Science Questions” below). If that is the case, the ESE will have to define a strategy for (1) conducting long-term monitoring, (2) obtaining in situ observations, and (3) combining and synthesizing both types of observations in models so that the ESE science questions on Earth system variability (especially trends) and on forcing and response can be answered.

The ESE science questions on the consequences of global change are posed as socially relevant issues: effects of global change on weather, precipitation patterns, water resources, land-use changes, and sea-level rise. These questions carry a requirement for long-term monitoring, but they also have a specific human dimension that links the science to societal concerns. Because NASA does not have strength in social science research, it must seek experts with the requisite

knowledge and/or form partnerships with other agencies and organizations to address these questions.²⁴

Addressing the questions on global change prediction and assessment involves synthesis of knowledge and understanding as a basis for improved predictive capability. All require significant modeling, data assimilation, analysis, and partnerships with other agencies and organizations. For example, responding to question P1 on weather forecasting depends on the involvement of the weather prediction community (e.g., NOAA's National Centers for Environmental Prediction). Question P1, however, does not represent a global change issue because its focus is weather forecasting on short time scales. A more accurate label for the primary science issue would be Earth System Science Predictions or Assessments.

Question P2 relates to the seasonal-to-interannual and decadal-to-centennial prediction and predictability at the heart of the Pathways report imperatives. However, whether the question can be answered is open to doubt because of shortcomings in the planned observational effort (see “Questions Related to Earth System Variability and Trends ” above). Answering certain of the 19 questions listed in the four preceding science issues in Table 3 will clearly help in predicting climate variability, but answering all of the previous questions will not lead to answering P2. The same is true for questions P3 to P5, which deal with long-term climate trends and changes in atmospheric chemistry.

The detailed science questions in the Plan reflect previous NASA planning documents, such as the EOS Science Plan,²⁵ and are responsive to the recommendations of various NRC reports. All the questions are worthy of being addressed. Many other detailed science questions within NASA's purview, however, are relevant to the five primary science issues and are not included in the Plan. (See, for example, the discussion in “Questions Related to Earth System Variability and Trends” above.) Moreover, the Plan does not acknowledge or discuss a number of capabilities and programs within NASA (e.g., ENSO research, tropospheric chemistry research, the Applications program) that would be integral to answering the detailed questions. Finally, the wording of the questions should emphasize understanding, rather than description. The Plan should be modified to include a brief discussion of how ESE's five research themes and other relevant but unmentioned NASA programs relate to the detailed science questions.

Recommendation 1. NASA should ensure either (a) that the revised Plan's detailed science questions reflect all of the major research and programmatic elements of ESEs current science program (e.g., ENSO, trends in tropospheric chemistry) or (b) that the revised Plan explains clearly why the science questions do not include certain ESE research and program elements.