Abstract. Earth scientists describe a wide range of observational
measurements as “proxy measurements”. By referring to such a vast body of
measurements simply as “proxy”, researchers dilute significant differences in
the various ways that measurements relate to the phenomena they intend to
describe. The limited language around these measurements makes it difficult
for the nonspecialist to assess the reliability and uncertainty of data
generated from proxy measurements. Producers and reviewers of proxy data
need a common framework for conveying proxy measurement methodology,
uncertainty, and applicability for a given study. We develop a functional distinction between different forms of measurement
based on the different ways that their outputs (values, interpretations)
relate to the phenomena they intend to describe (e.g., temperature).
Paleotemperature measurements, which are used to estimate temperatures of
systems in Earth's past, serve as a case study to examine and apply this new
functional proxy definition. We explore the historical development and
application of two widely used paleotemperature proxies, calcite δ18O and TEX86, to illustrate how different measurements relate to
the phenomena they intend to describe. Both proxies are vulnerable to causal
factors that interfere with their relationship with temperature but address
those “confounding causal factors” in different ways. While the goal of
proxy development is to fully identify, quantify, and calibrate to all
confounding causal factors, the reality of proxy applications, especially
for past systems, engenders unavoidable and potentially significant
uncertainties. We propose a framework that allows researchers to be explicit
about the limitations of their proxies and identify steps for further
development. This paper underscores the ongoing effort and continued need
for critical examination of proxies throughout their development and
application, particularly in Earth's history, for reliable proxy
interpretation.
Does a proxy measure up? A framework to assess and convey proxy reliability
