Sorry, you need to enable JavaScript to visit this website.

CVAS scientific goals

Phase 3

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
This topic will develop theoretical models based on physical principles describing the space-time scaling structure of climate variability from annual to millennial timescales. Calibration and development will be informed by estimates derived from climate archives and a range of model simulations, from conceptual to full complexity models.

(ii) Proxy-system modelling and statistics
This topic will model proxy- and archive-specific processes and quantify their (timescale-dependent) effect on variability estimates in a probabilistic framework. This will allow a comprehensive quantification of the uncertainty in reconstructions and the construction of spatially explicit spectral tuning targets.

(iii) Climate model (de/re)tuning
This topic will explore a larger model parameter space to identify parameters linked to the amplitude and spatial structure of supra-decadal variability. Intermediate complexity models and fast coupled GCMs will be used first, and knowledge gained will be transferred into full complexity climate models.

(iv) Uncalibrated proxies and chronologies
This topic will study uncalibrated proxies using advanced statistical and time series analysis methods to identify drivers and dynamic links. Spectral and other characteristics will be investigated and compared against calibrated proxies, theoretical physical models and climate model simulations. The potential for obtaining hydroclimate spectra will be explored. The scaling properties of chronologies will also be studied as irregularities in measurement density over a wide range of scales can lead to systematic statistical biases, which can be corrected.

Phase 2 

The overarching goal of Phase 2 of CVAS was to examine climate variability in space and time, with the focus on Holocene decadal to millennial variability, and its implications for future climate evolution.

A special focus was given to scaling as a means to compare paleo time series with observations and simulations.

One key finding from Phase 1 (2016-2019) was the difficulty in separating proxy error from climate variability. The time-scale dependency of the transfer function and error in many proxy recording and reconstruction processes means that they affect scaling estimates for proxy records.

This has implications for not only the CVAS target of variability but also any quantitative use of paleoclimate records, a core theme of PAGES.

Image 1: A view of a single climate zone (Baie St. Paul, Quebec, Canada) showing several subsystems including wetlands, ocean (estuary) and atmosphere that are each highly variable over wide ranges of space - time scales. CVAS is trying to understand this climate puzzle. Image: Shaun Lovejoy, 2015.
Image 1: A view of a single climate zone (Baie St. Paul, Quebec, Canada) showing several subsystems including wetlands, ocean (estuary) and atmosphere that are each highly variable over wide ranges of space - time scales. CVAS is trying to understand this climate puzzle.
Image: Shaun Lovejoy, 2015.

Thus, in Phase 2, we further implemented and continued the proxy modeling efforts of the DAPS working group.

In this context, the objectives of the multidisciplinary working group involving specialists of non-linear physics, climatologists and paleoclimatologists, were to:

1. 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 the DAPS work.
2. 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.
3. 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).
4. Investigate the implication of the results for reconstruction and assimilation efforts and for constraining climate projections.
5. Advance our understanding of the physical mechanisms of scaling constrained by our empirical findings.
6. Explore the application of the CVAS concepts beyond climate variability, e.g. the possible interactions between 'physics' and 'life' at the centennial scale (with links to EcoRe3).