The PAGES/CLIVAR Intersection: Vision for the future

Gavin Schmidt1, Valérie Masson-Delmotte2, and Intersection Panel Members 1Goddard Institute for Space Studies, NASA, New York, USA; gschmidt@giss..gov 2Laboratoire des Sciences du Climat et de l'Environnement, Gif-sur-Yvette, France; [email protected] News Program

The PAGES/CLIVAR Intersection Working 2) variability over the last of multidecadal variability and its impacts Group is jointly sponsored by PAGES and few millennia on, in particular, hydrology. the Climate Variability and Predictability Well-dated, high-resolution proxy re- (CLIVAR) project of the World Climate Re- constructions and model simulations 4) Hydrological changes and search Programme (WCRP), and plays an incorporating estimates of natural and interactions with the land surface important role in developing and imple- anthropogenic forcings for the last 2 ka Recent observations indicate that the trop- menting the overlapping research inter- offer opportunities to assess the natu- ical realm is expanding with increasing ests of both these programs. The forma- ral decadal to centennial variability and occurrence of drought in the sub-tropics. tion of the Intersection was predicated on forced responses in conditions similar to This trend is projected to continue under the idea that paleoclimate studies provide present. Despite progress in recent years, IPCC AR4 scenarios. There is also consid- a useful adjunct to studies of modern cli- however, important uncertainties and ca- erable evidence suggesting terrestrial cli- mate variability and likely future change. veats exist with regard to both empirical mate variability is strongly influenced by Since its establishment in the mid-1990’s, reconstructions and model estimates. hydrological and biospheric interactions the goals of the Intersection have evolved Upcoming activities will therefore and feedbacks. This is particularly relevant with the changing focus of each parent or- focus on advancing process-based com- to high-latitude regions and the tropics, ganization. At the Panel meeting in Italy in parisons of models and data through an where it has been shown that feedbacks June 2008, the goals were again updated enhanced appreciation of forward mod- between the monsoon and land surface and are now detailed in a new PAGES/CLI- eling of specific proxies and at specific conditions have significantly influenced VAR Intersection Vision Document. In ad- sites, including the role of downscaling climate variability on all timescales. dition, the Panel decided that Valérie Mas- from large-scale model simulations. The ESMs that incorporate these feed- son-Delmotte will replace Eystein Jansen Paleoclimate Reconstruction Challenge backs are now being used for future cli- as Co-Chair, alongside Gavin Schmidt. The (http://www.pages-igbp.org/science/ mate change prediction and need to be Panel also discussed the need for a rep- prchallenge/) and the regional PAGES 2k rigorously tested against the paleoclimate resentative from Asia, with particular ex- Network (http://www.pages-igbp.org/sci- record. The emphasis of the Intersection pertise in analyzing the instrumental and ence/last2millennia.html) will both play will primarily be on initiating and support- rich documentary records of, for example, key roles in driving the science of this is- ing data synthesis activities concerned China, to join the Panel. Any interested sue. with data-model interaction. Particular candidates are asked to contact Gavin or emphasis lies on forward modeling of Valérie directly. 3) North Atlantic circulation climate proxy data with relevance to low A number of key scientific issues iden- changes latitude changes in hydrology. tified by the Intersection Panel will be ad- Interactions among the , atmo- dressed over the coming years. They are sphere, and sea ice are the likely cause 5) Tropical cyclones, extreme categorized into overarching cross-cut- of decadal to multi-decadal and centen- precipitation events ting issues, in addition to 4 more specific nial variability in the Atlantic meridional For some extreme events (e.g., tropical topical issues. overturning circulation (MOC), with atten- cyclones, droughts and floods), there dant impacts on spatial patterns of tem- is some theoretical basis for expecting 1) Overarching cross-cutting perature and precipitation. Thus improved changes in their occurrence and/or in- issues understanding of MOC variability may tensity, associated with changes in the - Forward modeling of proxy data, which serve to improve the climate projections background climate state. However, it is means including the processes that pro- in these regions. Uncertainties in model the of extreme events that they duce proxy records directly within Earth parameterizations and the response of the are rare, and so the observational record System Models (ESMs) is considered of to anthropogenic forcings is often sparse. By targeting specific prox- fundamental importance to further im- make projections of future MOC behavior ies (paleo-tempestology) or by increasing proving model-paleodata comparisons. unclear. Since multiple proxy records re- the appreciation of long documentary re- - Reducing uncertainties in proxy recon- flect MOC changes and their climatic im- cords available in Europe, US East Coast, structions (and data synthesis in general) pact, MOC variability is an excellent show- Japan, China and Korea, an improved basis are important for improving climate mod- case for the value of using forward models for the characterization of some extreme eling targets and for understanding the of paleo-proxies, specifically ocean prox- events could be developed. intrinsic variability and forced response of ies, water, carbon and nitrogen isotopes, For more detailed information on the climate system. atmospheric chemistry, dust and sea salt the planned activities of the Intersec- - Calibration of proxies against variability aerosols. tion, and the full Vision Document, please seen in the instrumental period is a pre- The Intersection will support syn- see http://www.clivar.org/organization/ requisite for improved synthesis of proxy- thesis activities focused on data-model pages/pages.php or download the docu- and observation-based approaches, and integration, particularly those that seek ment from the PAGES Product Database requires interaction between paleoclima- to improve mechanistic understanding at http://www.pages-igbp.org/products/ tologists and climatologists. under "others". 121

PAGES news • Vol 17 • No 3 • October 2009