CCSP Synthesis and Assessment Product Prospectus

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CCSP Synthesis and Assessment Product Prospectus

    CCSP Product 3.4 Prospectus INTERNAL CCSP REVIEW ONLY

1 Prospectus for Synthesis and Assessment Product 3.4


    3 Abrupt Climate Change


    5 Lead Agency: USGS

    6 Supporting Agencies: NOAA, NSF

    7 ________________________


    9 1. Overview: Description of Topic, Audience, Intended Use,

    10 and Questions to be addressed


    12 1.1 Description of Topic


    14 This prospectus provides an implementation plan for developing and producing Climate Change 15 Science Program (CCSP) Synthesis and Assessment Product 3.4, “Abrupt Climate Change.

    16 Paleoclimate records of climate and environmental change derived from archives such as tree rings, 17 ice cores, corals, speleothems and sediments indicate that global and regional climate has 18 experienced repeated abrupt changes, many occurring over a time span of decades or less. The 19 National Research Council (NRC) report “Abrupt Climate Change” (Alley, et al., 2002) offers two 20 definitions of abrupt climate change. A mechanistic definition defines abrupt climate change as 21 Transition of the climate system into a different state (of temperature, rainfall, and other aspects) 22 on a time scale that is faster than the responsible forcing.” This definition implies that abrupt

    23 climate changes involve a threshold or non-linear feedback within the climate system from one 24 steady state to another. An impacts-based definition defines abrupt climate change as “Change of

    25 the climate system that is faster than the adaptation time of social and/or ecosystems.” Abrupt

    26 climate changes might have a natural cause (such as volcanic aerosol forcing), an anthropogenic 27 cause (such as increasing carbon dioxide in the atmosphere), or might be unforced (related to 28 internal climate variability). Regardless of the cause, abrupt climate change presents potential 29 risks for society that are poorly understood. An improved ability to understand and model future 30 abrupt climate change is essential to provide decision-makers with the information they need to 31 plan for these potentially significant changes.


    33 Current research on abrupt climate change is focused on documenting evidence of past abrupt 34 climate change, refining the temporal and geographic extent of the change, proposing mechanisms 35 to explain the change, and performing atmosphere-ocean model experiments. Examples of abrupt 36 climate change that have received special attention include the Younger Dryas cold reversal event 37 that occurred during the last deglaciation, the rapid onset of widespread periods of drought that 38 have been documented in hydrologic records of the past 2,000 years in the American West, and 39 abrupt shifts in modes of ocean-atmosphere interaction (e.g., El Nino-Southern Oscillation and the 40 Arctic Oscillation) seen in both paleo and instrumental records. Although the Younger Dryas 41 event occurred during a time when a large ice sheet was present on North America, causing some 42 to question whether an event of comparable magnitude could occur in the near future, 43 understanding its cause is critical if we are to evaluate scenarios of future climate change. 44

    45 Abrupt climate changes can affect regions or the entire globe. Many of the abrupt changes 46 examined so far are regional rather than global in extent. Such abrupt changes reflect

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    CCSP Product 3.4 Prospectus INTERNAL CCSP REVIEW ONLY

    1 reorganizations of the climate system from one stable state to another, and are characterized by 2 changing patterns in the transfer of heat and energy with accompanying shifts in temperature, 3 precipitation, winds, and other variables. For example, one region may warm as another cools, or 4 become drier as another becomes wetter. Regional impacts could be large while the global mean 5 change is small. In the modern world of increasing population and limited resources, regional 6 changes are particularly significant in terms of the challenges or risks that they pose to society. 7 Abrupt climate changes with either regional or global impacts will be considered in this 8 assessment.


    10 Much debate exists as to what types of climate change should be considered under the umbrella of 11 abrupt climate change. The El Nino-Southern Oscillation (ENSO) and Arctic Oscillation (AO) are 12 examples of climate processes that appear to have different stable modes. Typically, as these 13 processes develop, climate variables such as temperature and sea level pressure remain in one 14 mode for a period of time, change to a different mean state, and change back again. Proponents 15 argue that different stable modes exist, and that the shift between modes constitutes an abrupt 16 climate change. The contrary view questions whether stable modes exist at all, or argues that these 17 changes do not fit the definition of an abrupt climate change event. This assessment follows the 18 lead of the NRC report in including these processes under the umbrella of abrupt climate change, 19 and supports the NRC recommendation to examine in more detail the processes that could lead to 20 different modes of ocean-atmosphere interaction.


    22 Abrupt climate changes can be accompanied by a change in the frequency of extreme events such 23 as hurricanes, heat waves, droughts and floods. In a changing climate, an abrupt increase in 24 extreme event frequency might be far more difficult to adapt to compared to a gradual increase. 25 For this reason, we include abrupt changes in extreme event frequency within report 3.4 and 26 exclude gradual changes in extreme event frequency. Climate extremes are the subject of 27 Synthesis and Assessment Product 3.3, “Weather and Climate Extremes in a Changing Climate.


    29 1.2 Intended Use and Audience


    31 This CCSP Synthesis and Assessment Product will be in the form of a report that (a) summarizes 32 the present status and key findings of national and international research on abrupt climate change, 33 and (b) discusses the strengths and limitations of existing knowledge for describing and analyzing 34 the risks of abrupt climate change. Abrupt climate change research is in an immature stage: 35 processes are still being identified; gaps exist in the archive of paleoclimate data; new records are 36 currently being developed; and modeling efforts are evolving. The analysis of probability (of a 37 specific change occurring), recently pioneered for global warming predictions (Knutti, et al., 38 2002), has yet to be applied to abrupt climate change. For these reasons we expect the report to be 39 most useful to those seeking to understand what is currently known and, conversely, what is not 40 known about the climate processes that can lead to abrupt climate change.


    42 1.3 Questions to be Addressed


    44 The paleoclimate record contains many examples of abrupt climate change. The NRC report on 45 Abrupt Climate Change considered a broad array of processes and impacts to explain past and 46 potential future instances of abrupt climate change. This Synthesis and Assessment Product will

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    CCSP Product 3.4 Prospectus INTERNAL CCSP REVIEW ONLY

    1 consider four types of change documented in the paleo record that stand out as being so rapid and 2 large in their impact that they pose clear risks to society in terms of our ability to adapt. They are 3 supported by sufficient evidence that hypotheses can be tested and risks investigated, and the 4 research indicates that the changes could occur in the future. These changes are i) alterations of the 5 ocean meridional overturning circulation; ii) widespread and sustained hydrologic changes to the 6 hydrologic cycle; iii) rapid release to the atmosphere of methane trapped in permafrost and 7 continental shelves; iv) rapid change in ice sheet mass. Note that the processes listed above closely 8 correspond to question 4.3 from the CCSP Strategic Plan, which reads: “What is the likelihood of

    9 abrupt changes in the climate system such as the collapse of the ocean thermohaline circulation, 10 inception of a decades-long mega-drought, or rapid melting of the major ice sheets?”


    12 i. Meridional Overturning Circulation change and influence on climate


    14 The Atlantic Ocean is characterized by a meridional overturning circulation (MOC) that has an 15 important effect on the climate of the surrounding continents. The wind-driven surface circulation 16 transports water northward in the North Atlantic, where it loses heat to the atmosphere, becomes 17 denser and sinks in the Nordic and Labrador Seas, forming a southward-flowing subsurface water 18 mass that eventually fills the North Atlantic as the North Atlantic Deep Water mass between 19 2,000-4,000 m (Talley, 1996). Much of this deep water eventually returns to the surface Atlantic 20 via the Pacific and Indian Oceans, forming what has been alternately termed the meridional 21 overturning circulation, the global conveyor belt or thermohaline circulation (THC). There is 22 evidence that the overturning in the Atlantic is not independent but is instead coupled to other 23 aspects of the climate. Independent of possible coupling, there is some evidence and ongoing 24 research to investigate whether the impacts of the Atlantic MOC are global in extent. 25

    26 One of the most remarkable discoveries in the field of paleoclimatology has been the observed 27 coincidence between the glacial climate state and reduced or altered MOC in the North Atlantic, as 28 observed in paleo proxies for the deep ocean circulation (McManus, et al., 2004). In contrast, the 29 present interglacial climate state is characterized by vigorous meridional overturning, which 30 through global feedback promotes a vigorous northeastward flow of warm surface waters of the 31 Gulf Stream (and North Atlantic Drift) across the North Atlantic, which, in turn, sustains more 32 equable climates in Europe. While the paleo record is still incomplete, evidence exists that some of 33 the abrupt climate changes that occurred during the last glacial interval, such as the 34 Dansgaard-Oeschger cycles, and during the deglacial period, such as the Younger Dryas, were 35 caused or amplified by changes in overturning circulation. These observations motivate the 36 paleoclimate community to improve our understanding of the overturning circulation, how it has 37 varied in the past, what the dominant controls have been, and how widespread are the impacts. 38

    39 Key parameters that influence ocean circulation are expected to change in the future. Most 40 simulations of future climate predict a slowdown of the thermohaline circulation in response to 41 increasing greenhouse gases in the atmosphere. As the climate warms due to the increase in 42 greenhouse gases, the North Atlantic surface ocean will also warm and become fresher due to 43 melting of margins of the Greenland ice sheet and precipitation increases in the mid-latitude North 44 Atlantic. Both increasing temperature and decreasing salinity reduce the density of the North 45 Atlantic surface ocean, hindering the convective sinking of the water and thus inducing a 46 slowdown of the MOC. Some climate models predict an eventual complete shutdown of the

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    1 overturning simulation, a change that might be permanent if the circulation has different stable 2 states. But many different processes and feedbacks affect this circulation, leading to considerable 3 uncertainty in these projections that must be evaluated from a combination of observational, 4 process-based, and modeling studies. From the perspective of risk, one of the most important 5 aspects of the MOC is the existence of a threshold level, beyond which North Atlantic surface 6 water becomes too buoyant to convect, providing a sound conceptual basis for abrupt climate 7 change.


    9 The primary questions to be addressed in this section of the report are:


    11 ; What are the factors that control the overturning circulation?

    12 ; How well do the current ocean general circulation models (and coupled

    13 atmosphere-ocean models) simulate the overturning circulation?

    14 ; What is the present state of the MOC?

    15 ; What is the evidence for change in the overturning circulation in the past? 16 ; What are the global and regional impacts of a change in the overturning circulation? 17 ; What factors that influence the overturning circulation are likely to change in the future, 18 and what is the probability that the overturning circulation will change? 19 ; What are the observational and modeling requirements required to understand the 20 overturning circulation and evaluate future change?


    22 The primary value of this section for decision-makers and policy-makers will be to provide a 23 summary of the present level of scientific understanding and remaining uncertainties in identifying 24 and describing the factors that influence the thermohaline circulation and its regional and global 25 impacts.


    27 ii. Rapid changes to the hydrologic cycle


    29 Accurate forecasts of seasonal precipitation change are critical for managing water resources 30 throughout the world, especially in water-stressed regions such as the American West and northern 31 Africa. Such forecasts have also proven to be crucial in the mitigation of floods and landslides. 32 Measurements from satellites and oceanic and atmospheric monitoring are used in developing and 33 testing sophisticated model forecasts. In recent years, significant advances have been made in 34 predicting precipitation in the western US using Pacific and Atlantic sea surface temperatures. 35 These analyses assume that future variability in these parameters will be similar to that which has 36 been experienced during the past 100 years (the reanalysis period).


    38 During 2002, more than 50 percent of the coterminous US experienced moderate to severe drought 39 conditions. Detailed study of the North American paleoclimate record of the past 2,000 years, 40 however, has revealed numerous periods of extended drought exceeding in duration and 41 geographic extent the 7-year-long, epic drought of the 1930s Dust Bowl. For example, a 42 prolonged dry event occurred throughout much of North America between AD 1575 and 1595, the 43 so-called 16th Century Megadrought. This 20-year long megadrought, however, pales in 44 comparison to a 400-year long period of elevated aridity and epic drought that was experienced 45 throughout the western United States between AD 900 to 1300 during the Medieval Climate 46 Anomaly (MCA). The MCA megadrought likely resulted from oceanic and atmospheric

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    1 conditions unlike those that we have experienced during the past 100 years, possibly from a 2 prolonged and sustained La Niña state in the Pacific. A sustained La Niña favors drought 3 conditions in the American Southwest, while the Northwest experiences increased precipitation 4 and a greater likelihood of floods. The debate continues as to whether climate processes such as 5 ENSO will be affected by human induced global warming. Understanding the causes and impacts 6 of past megadroughts and associated oceanic/atmospheric conditions is therefore crucial to 7 assessing the risk of abrupt hydrologic change that we might experience in the future. 8

    9 Questions to be considered in this section are:


    11 ; What is our present understanding of the causes of major drought and hydrologic change 12 over the historical record, including the role of the oceans or other natural or 13 non-greenhouse gas anthropogenic effects as well as land-use changes?

    14 ; What is our present understanding of the duration, extent and causes of megadroughts of 15 the past 2,000 years?

    16 ; What states of oceanic/atmospheric conditions and the strength of land-atmosphere 17 coupling are likely to have been responsible for sustained megadroughts?

    18 ; How might such a state affect the climate in regions not affected by drought? (For example, 19 enhanced floods or hurricanes in other regions.)

    20 ; What will be the signatures of change in the state of natural variability of the ocean and 21 atmosphere that will signal the abrupt transition to a megadrought?


    23 The primary audience for this section is policymakers, who require an improved basis for 24 ascertaining the present state-of-knowledge, as well as uncertainties, in our scientific 25 understanding of the causes of past major droughts and the likelihood future ones. This 26 understanding will allow the early implementation of programs to limit the impact of major 27 droughts such as a those outlined by the National Drought Mitigation Center at the University of 28 Nebraska, Lincoln. These impacts include loss or damage to agriculture, forest production, and 29 fisheries; increased energy costs; loss to tourism industry; decreased water supply for public 30 consumption; damage to ecosystems and biodiversity; increased fires; decreased air quality (dust, 31 fires); increased health risk, both through rise of drought-related diseases and from diseases 32 associated with famine and poorer nutrition; and increased political unrest. At the same time, this 33 report will also benefit policymakers attempting to implement programs that limit societal losses 34 in other areas where increased precipitation and/or increased likelihood of floods may be forecast 35 from abrupt hydrologic change.


    37 iii. Rapid release of methane from hydrates


    39 Methane is produced naturally during the anaerobic decomposition of organic matter by bacteria 40 and is regularly released to the atmosphere. Vast amounts of methane, however, are stored in the 41 frozen form of methane hydrate (molecules containing methane and water in the solid state) in 42 Arctic permafrost and in sea floor sediments below a depth of about 250 m. It is estimated that 43 there are 1000-6000 Gigatons (Gt) of carbon stored as methane hydrates in ocean sediments and 44 about 400 Gt stored in sediments under permafrost regions (Buffett and Archer, 2004). For 45 comparison, the atmosphere currently contains ~730 Gt of carbon. A warming of bottom ocean 46 waters or the land surface caused by greenhouse gases could cause the hydrates to melt and release

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    1 methane to the atmosphere. Methane is a powerful greenhouse gas, and is about 24 times more 2 effective on a mass basis at absorbing long wave radiation than is carbon dioxide. Such a release 3 of methane to the atmosphere could amplify the initial warming. Following its rapid oxidation, 4 carbon initially released as methane will persist for centuries as carbon dioxide. 5

    6 Questions to be addressed in this section of the report are:


    8 ; What is the volume of methane in terrestrial and marine sources and how much of it is 9 likely to be released in various climate change scenarios?

    10 ; What is the impact on the climate system of the release of varying quantities of methane 11 over varying intervals of time?

    12 ; What is the evidence in the past for abrupt climate change caused by massive methane 13 release?

    14 ; How much methane is likely to be released by thawing of the topmost layer (3 m) of 15 permafrost? Is thawing at greater depths likely to occur?

    16 ; What conditions (in terms of sea level rise and warming of bottom waters) would allow 17 methane release from hydrates locked up in sea floor sediments?

    18 ; What are the observational and modeling requirements necessary to understand methane 19 storage and its release under various future scenarios of abrupt climate change? 20

    21 iv. Rapid change in ice sheet mass balance


    23 Glaciers and ice sheets grow or recede due to differences between accumulation and ablation. 24 Traditionally these processes were thought to change slowly, over centuries to millennia. Recent 25 observations (Rignot, et al., 2006) and process-based studies (Zwally, 2002) indicate that ice loss 26 can occur much more rapidly, within decades, driven by mechanical processes that include the 27 formation of meltwater at the surface and subsequent flow to deeper layers, seasonal cycles in melt 28 and flow, warming and lubrication at the base, acceleration of outlet glaciers, and disintegration of 29 ice shelves. Some observations indicate that ice loss of the Greenland Ice Sheet and West 30 Antarctic Ice Sheet has accelerated in the last decade. If these rates continue to increase, sea level 31 rise will occur much faster than predicted in the Intergovernmental Panel on Climate Change 32 (IPCC) 2001 assessment, which did not consider mechanical processes in the ice sheet models. 33 New data from process-based studies and observations of ice sheet mass balance could 34 significantly shift predictions in future climate models.


    36 The paleoclimate record provides evidence that ice melt is an abrupt climate change that can occur 37 much faster than the forcing. The rapid melting of the large Northern hemisphere ice sheets at the 38 end of the last Ice Age, observed as the rate of sea level rise, occurred much faster than the orbital 39 forcing thought to drive these changes. It is likely that individual ice sheets and glaciers responded 40 even faster. Sea level records integrate the effects of many ice sheets melting at different rates in 41 both hemispheres. Improved paleoclimate records of ice sheet and glacier melt can contribute to 42 our understanding of abrupt melting of the remaining ice sheets and glaciers. Some of these topics 43 are also considered under the CCSP report titled “Past climate variability and change in the Arctic 44 and at high latitudes” (Synthesis and Assessment Product 1.2).


    46 Questions to be addressed in this section of the report are:

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    2 ; What is the paleoclimate evidence regarding rates of rapid ice sheet melting? 3 ; What are the recent rates and trends in ice sheet mass balance? 4 ; What is the impact on sea level if the recently observed rapid rates of melting continue? 5 ; What is needed to model the mechanical processes that accelerate ice loss? 6


    8 2. Contact Information for Responsible Individuals at Lead and Supporting Agencies 9

    10 The US Geological Survey (USGS) is the lead agency for this CCSP Synthesis and Assessment 11 Product, with the National Oceanic and Atmospheric Administration (NOAA) and National 12 Science Foundation (NSF) as the supporting agencies. Because USGS is the lead agency, the 13 product will be subject to USGS guidelines implementing the Information Quality Act (IQA). 14 Contact information for responsible individuals at lead and supporting agencies is: 15

    16 USGS (Lead) John McGeehin

    17 U. S. Geological Survey

    18 MS 926A

    19 12201 Sunrise Valley Drive

    20 Reston, VA 20192

    21 Email:

    22 Phone: 703-648-5349


    24 John Barron

    25 U. S. Geological Survey

    26 345 Middlefield Road

    27 MS 910

    28 Menlo Park, CA 94025

    29 Email:

    30 Phone: 650-329-4971


    32 NOAA David M. Anderson

    33 NOAA Paleoclimatology Program

    34 325 Broadway, E/CC23

    35 Boulder, Colorado, 80305

    36 Email:

    37 Phone: 303-497-6237


    39 NSF Dave Verardo

    40 National Science Foundation

    41 Paleoclimate Program

    42 4201 Wilson Blvd, Room 725

    43 Arlington, VA 22230

    44 Email:

    45 Phone: 703-292-8527


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1 3. Lead Authors


    3 The following individuals are proposed as lead authors:


    5 Dr. Peter Clark

    6 Dr. Ed Cook

    7 Dr. Thomas Delworth

    8 Dr. Carrie Morrill

    9 Dr. Daniel Muhs

    10 Dr. Jonathan Overpeck

    11 Dr. Richard Seager

    12 Dr. Konrad Steffen

    13 Dr. Andrew Weaver

    14 Dr. Robert Webb


    16 Appendix A provides brief biographies for each of the authors proposed thus far. It is anticipated 17 that additional authors will be added to the team in order to ensure comprehensive and balanced 18 subject matter expertise, in conformance with requirements for the Federal Advisory Committee 19 Act (FACA). The author team will also depend extensively on solicitation of relevant information 20 from experts in the Federal and academic research community during the preparation of this 21 report.



    24 4. Stakeholder Interactions


    26 Stakeholder input will be solicited through the public comment period tied to the development of 27 this prospectus and all subsequent draft documents put forth by the authors of SAP 3.4. The 28 authors in collaboration with the lead and supporting agencies may call upon a set of stakeholders 29 to broaden the input for this study as necessary. The process of drafting and incorporating public 30 comment will comply with the rules set forth in the Federal Advisory Committee Act. 31


    33 5. Drafting


    35 The lead authors will draft answers to the key questions in their respective sections. They will also 36 prepare an introductory section to describe the topic, the audience, and the intended use of this 37 product. The lead author for each section may assign primary responsibility for drafting to a 38 specific contributing author. The scientific/technical synthesis of the document will utilize 39 published, peer-reviewed scientific literature.


    41 Two workshops are envisioned as a means to help the research community provide input and 42 identify divergent opinions on as many as four abrupt climate change topics, 1) meridional 43 overturning circulation, 2) abrupt hydrologic change, 3) methane hydrate release, and 4) rapid ice 44 melt. The lead authors will be responsible for incorporating materials from contributing authors 45 and from the workshop participants in the draft product.


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    1 After the product is drafted, the lead authors (or coordinating lead author and the authors 2 responsible for each of the sections) will write a non-technical summary. Lead and contributing 3 authors will base their writing on published, peer-reviewed scientific literature. Where appropriate, 4 the product and its non-technical summary will identify disparate views.



    7 6. Review


    9 USGS will ensure that Synthesis and Assessment Product 3.4 is reviewed at all stages as specified 10 in the Guidelines for Producing CCSP Synthesis and Assessment Products and consistent with the

    11 Information Quality Act and Information Quality Bulletin for Peer Review. All comments and

    12 responses will be documented and made publicly available.


    14 The public is invited to nominate Expert Reviewers to participate in the peer review of the draft of 15 CCSP Synthesis and Assessment Product 3.4. Nominations should be sent to John McGeehin, 16 USGS lead, at the address given in Section 3 of this prospectus. Nominations are due by 30 17 November 2006. All nominations will be forwarded to the USGS IQA representative for 18 consideration. Nominations must include an up-to-date curriculum vitae and listing of publications. 19 As IQA Lead Agency, USGS will ensure that selected reviewers are technically qualified, as 20 demonstrated by scientific experience, published work, and stature within and across the scientific 21 community. USGS will ensure that the slate of reviewers reflects a balance of scientific and 22 technical perspectives. USGS will also be responsible for screening the nominees for real or 23 perceived conflict of interest and independence. Peer reviewers who are Federal employees will be 24 subject to Federal requirements governing conflict of interest [see 18 U.S.C. 208, 5 C.F.R. Part 25 2635 (2004)]. Reviewers who are not Federal employees will be screened pursuant to the National 26 Academy of Sciences policy for committee selection with respect to conflict of interest. 27

    28 The Expert Review will consist of technical experts who will submit comments similar to those 29 solicited as part of a journal peer review. In addition, independent reviews may be obtained from 30 non-climate scientists, selected by USGS, to comment on how understandable and useful the draft 31 product is to non-specialists.


    33 USGS will provide a charge statement for reviewers, which will be distributed with the draft 34 product and posted at USGS’s IQA website, and linked and/or replicated on the CCSP web site

    35 . The charge statement will be posted on the above sites as soon 36 details become available. The names and affiliations of the reviewers that are selected will be 37 posted on these sites.


    39 Following the Expert Review, the lead authors will revise the draft product by incorporating 40 comments and suggestions from the reviewers. USGS will prepare a written response to the peer 41 reviewers’ comments explaining its agreement or disagreement with the views of the peer

    42 reviewers, and the actions taken in response to the peer review. The draft product will then be 43 released for a 45 day public comment period following CCSP guidelines. The lead authors will 44 prepare a third draft of the product, taking into consideration the comments submitted during the 45 Public Comment Period. The scientific judgment of the lead authors will determine responses to 46 the comments.

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    2 Once USGS, as IQA Lead Agency, determines that the report conforms to CCSP and IQA 3 guidelines, it will submit a draft of the product and a compilation of the comments received to the 4 CCSP Interagency Committee. If the CCSP Interagency Committee determines that further 5 revision is necessary, their comments will be sent to USGS and supporting agencies for 6 consideration and resolution by the lead authors. If needed, USGS may ask an independent science 7 advisory group to provide additional scientific analysis to help resolve scientific uncertainty 8 associated with specific issues. Once the CCSP Interagency Committee has determined that the 9 report has been prepared in conformance with the CCSP guidelines, the IQA and FACA, it will 10 submit the report to the National Science and Technology Council (NSTC) for final review and 11 approval. The CCSP Interagency Committee in consultation with the lead and supporting agencies 12 and the lead authors will address issues raised during the NSTC review.



    15 7. Communications


    17 Once NSTC clearance has been obtained, USGS will coordinate publication and release of the 18 Synthesis and Assessment Product. The published report will follow the standard format for all 19 CCSP Synthesis and Assessment Products.



    22 8. Proposed Timeline


    24 Prospectus

    25 Drafting, January - October 2006

    26 Stakeholder interactions (including other scientists), Ongoing during prospectus development 27 CCSP review, September 2006

    28 Draft Prospectus public review, October/November 2006

    29 Revised draft, November/December 2006

    30 Final, December 2006


    32 Report

    33 Drafting, March 2007-August 2007

    34 Workshop 1. March 2007

    35 Workshop 2. August 2007

    36 Stakeholder involvement ongoing during drafting process and public comment period 37 Draft 1 provided to expert reviewers, September 2007

    38 Draft 2 made available for public comment, February 2008

    39 Draft 3 submitted to CCSP for review April 2008

    40 Product released June 2008


    42 References


    44 Alley, R. B., et. al. (2002). Abrupt climate change: Inevitable Surprises. Washington, D. C., 45 National Academy Press.


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