CVAS - Climate Variability Across Scales
The Climate Variability Across Scales (CVAS) working group examines climate variability in space and time, with the focus on Holocene decadal to millennial variability, and its implications for future climate evolution. Special focus is given to scaling as a means to compare paleo time series with observations and simulations.
This group is open to anyone who is interested, and early-career researchers are encouraged to be involved:
- Sign up to the CVAS mailing list
- Assess the time-scale dependent transfer functions from climate to the recorded proxy in order to implement and improve proxy system models, building on and integrating work by PAGES' former working group DAPS.
- Improve statistical and modeling tools for analyzing and comparing (paleoclimate) time series and spatial distributions and to bring these tools to other PAGES working groups.
- Create a synthesis of the spatio-temporal structure of climate variability based on the PAGES 2k Network and TEMP12k databases: “The CLIMAP of temperature variability” and compare this to current model simulations (CMIP/PMIP).
- Investigate the implication of the results for reconstruction and assimilation efforts and for constraining climate projections.
- Advance our understanding of the physical mechanisms of scaling constrained by our empirical findings.
- Explore the application of CVAS concepts beyond climate variability e.g. the possible interactions between 'physics' and 'life' at the centennial scale (with links to PAGES working group EcoRe3)
While climate variability occurs over huge ranges, decadal to millennial variability is of special importance. Firstly, the natural variability at these scales dynamically interacts and overlaps with anthropogenic forcing, with implications for understanding both the industrial epoch and future climate projections.
Secondly, paleoclimate records suggest that variability at these scales is strong, yet it cannot be explained by the much lower frequency orbital forcing. Thirdly, existing climate models seem to strongly underestimate centennial to millennial climate variability, at least on regional scales, pointing to major deficiencies in either internal variability, the strength of responses to forcing, or erroneous paleoclimate-based variability estimates.
The origin, magnitude and scaling of environmental variability are linked to the stability of the Earth system, its sensitivity to external forcing, as well as the statistics of extremes and are thus a central topic in PAGES' holistic Earth system science approach.
Phase 3 of CVAS (January 2024-January 2027) will develop a coherent framework encompassing paleoclimate archives, and complex and theoretical climate models, building on the climate variability mapping of CVAS-2 (in preparation).
Phase 2 of CVAS (2020-2023) quanified climate variability across space and at decadal and longer time scales by combining advanced understanding of paleo-proxy data, proxy-system modeling, scaling analysis techniques, theory and climate models.
Phase 1 of CVAS (2016-2019) brought together paleoclimate scientists across disciplines on the question of scaling in climate variability using tools and theory from nonlinear geophysics.
The main goal of CVAS-3 consists of developing a coherent framework encompassing paleoclimate archives, and complex and theoretical climate models, building on the climate variability mapping of CVAS-2 (in preparation). This will be achieved through the work of four topics (below) working in synergy to improve our understanding of proxies and translate this into products for data-model comparisons and identify the underlying mechanisms leading to long-term climate variability.
(i) Theory and models
(ii) Proxy-system modelling and statistics
(iii) Climate model (de/re)tuning
(iv) Uncalibrated proxies and chronologies
> Read more about the above four topics
Find out more about the group's scientific goals here.
Find out more about the group's seminar series here.
Learn more and participate
Phase 3 timeline
January 2024: Start of CVAS-3, open call to the CVAS mailing list regarding participation in the sub-groups.
February-March 2024: Online seminar pertaining to (iii) on the topic of “Climate model development and tuning: built for (in)stability?”. The seminar will aim to stimulate discussion around the aims of (iii) by inviting expert climate model developers to present the history and philosophy behind their work, and express their perspective on the ability of climate models to simulate potential instability, or whether they were “Built for stability” (Valdes, 2011).
April 2024: CVAS EGU session and a CVAS EGU short course.
June 2024: In person meeting in Europe (potential central locations to minimize travel include Tübingen, Brussel, Berlin, Amsterdam) tackling two core topics: “Development of spectral tuning targets” relating to (i), (ii) and (iii), and “From proxy and sampling statistics to climate variables” related to (ii) and (iv).
October-November 2024: Online seminar: Topic relating to latest advances in proxy development, proxy-system modelling and statistical methods.
December 2024: CVAS AGU session. We will utilize this opportunity to boost North American active participation in the group.
January-June 2025: Finalization of the spectral tuning targets and call for usage in model development, evaluation and calibration.
February-March 2025: Online seminar: Topic to be determined.
April 2025: CVAS EGU session and a CVAS EGU short course.
June 2025: In person meeting in North America (potential locations on east coast to facilitate travel from Europe, Montreal, Boston, Ottawa).
December 2025: CVAS AGU session.
2026: EGU and AGU sessions, as well as online seminars with topics following recent developments.
Synthesis meeting should be held outside of Europe and North America for the first time.
In previous CVAS workshops, the two formerly very separated communities – nonlinear geophysics and paleoclimatology (data-producers, modelers and statisticians) – created strong links and an understanding for one other. This challenging cross-disciplinary thinking was advertised and brought to a wider audience via annual CVAS EGU sessions and CVAS EGU short courses. Tools and review articles were developed, including a Past Global Changes Magazine issue. CVAS Phase 2 built on this foundation by reinforcing partnerships and exchange with other PAGES groups (i.e. 2k Network, SISAL, VICS) to solve the outstanding problem of decadal to millennial variability in the climate system.Moving from understanding each other to synergistic production of knowledge, specific topics were selected for each workshop and teams formed. They prepared their contribution to the workshop topic in advance and synthesized the results after the workshop, with the aim of producing publications which could be directly built upon in order to answer objectives of Phase 2. CVAS Phase 2 integrated and continued the proxy system modeling part of DAPS, with a special focus on the transfer function between climate variability and proxy variability. The outcomes of this research is relevant for all reconstruction efforts in PAGES situated in different research groups. Finally, we explored the application of the CVAS concepts beyond climate variability, e.g. the possible interactions between 'physics' and 'life' at the centennial scale with PAGES groups such as EcoRe3.
CVAS-2 was successful in broadening the network with over 200 people from 45 countries now subscribed to the mailing list with three successful seminar series reviewing CVAS and DAPS themes: recent progresses, reviewing climate variability on all timescales, and integrating the developing field of proxy-system modelling. In person meetings were held in Heidelberg (July 2021) and Potsdam (March 2023).
The recently accepted Nature Geoscience Perspective (Laepple et al. 2023) was incepted in Heidelberg and presents a provocative review and perspective on model-data comparison resolving the apparent contradiction between studies investigating temperature variability on global versus regional scales. The CVAS Potsdam workshop was held concurrently with the 2k Network workshop and culminated in a joint topical science meeting on centennial variability. This successful meeting led to ongoing collaborative research projects involving CVAS and 2k researchers.
During CVAS-2, EGU and AGU sessions were held every year, as well as a short course at EGU.Overall, at least 15 papers stemming from CVAS have been published or accepted to date in diverse journals including Nature Climate Change, Nature Geoscience, Nonlinear Processes in Geophysics, Journal of Climate, Earth System Dynamics and Climate of the Past.
Phase 2 timeline
January 2020: Start of CVAS Phase 2
Formation of subgroups on the:
(A) transfer of climate to proxy variability (incorporating the DAPS PSM work)
(B) methods for variability and scaling analysis
(C) theory and mechanisms of (climate)variability; and
(D) variability synthesis product.
May 2020: Splinter Meeting at EGU, CVAS EGU session and a CVAS EGU short course
All details here.
December 2020: First CVAS-II Meeting: Beyond Palaeoclimate Ping Pong
All details here.
July 2020: Setup of a website/repository (or continuation of the DAPS website) on tools, data and models
May 2021: Splinter Meeting at EGU, CVAS EGU session and a CVAS EGU short course
Autumn 2021: Second CVAS general meeting
May 2022: Splinter Meeting at EGU, CVAS EGU session and a CVAS EGU short course
Autumn 2022: CVAS Synthesis meeting
Heather Andres (ECR; climate modeling, attribution, model-data comparison)
Michel Crucifix (theoretical climate dynamics)
Christian Franzke (theoretical meteorology, methods)
Fabrice Lambert (data liaison officer; ice-core records)
Thomas Laepple (group leader; statistics, proxy recording systems)
Gerrit Lohmann (climate modeling, dynamical system theory)
Shaun Lovejoy (nonlinear geophysics)
Kira Rehfeld (statistics, climate modeling)
Cristian Proistosescu (ECR; statistics, conceptual climate models)
Anne de Vernal (marine records)
PAGES SSC liaison
Paul Valdes (University of Bristol, UK)