31 research outputs found
Using the past to constrain the future: how the palaeorecord can improve estimates of global warming
Climate sensitivity is defined as the change in global mean equilibrium
temperature after a doubling of atmospheric CO2 concentration and provides a
simple measure of global warming. An early estimate of climate sensitivity,
1.5-4.5{\deg}C, has changed little subsequently, including the latest
assessment by the Intergovernmental Panel on Climate Change.
The persistence of such large uncertainties in this simple measure casts
doubt on our understanding of the mechanisms of climate change and our ability
to predict the response of the climate system to future perturbations. This has
motivated continued attempts to constrain the range with climate data, alone or
in conjunction with models. The majority of studies use data from the
instrumental period (post-1850) but recent work has made use of information
about the large climate changes experienced in the geological past.
In this review, we first outline approaches that estimate climate sensitivity
using instrumental climate observations and then summarise attempts to use the
record of climate change on geological timescales. We examine the limitations
of these studies and suggest ways in which the power of the palaeoclimate
record could be better used to reduce uncertainties in our predictions of
climate sensitivity.Comment: The final, definitive version of this paper has been published in
Progress in Physical Geography, 31(5), 2007 by SAGE Publications Ltd, All
rights reserved. \c{opyright} 2007 Edwards, Crucifix and Harriso
GPR Response From Buried Pipes: Measurement on Field Site and Tomographic Reconstructions
The identification of the physical nature of an object
or target causing a ground-penetrating radar (GPR) anomaly, as
well as the estimation of a target’s dimensions and geometry, is
rather challenging. To improve target identification, basic studies
are still required, and they can be addressed primarily using a
laboratory- or field-based physical model. The field model (test
site) is usually expensive and difficult to build, but it provides
data for controlled target properties and geometry from a natural
environment that are essential for testing processing techniques.
In this paper, we present the results from a field experiment where
GPR data were collected on plastic and metallic pipes. The main
objective is the comparison of the classical migration technique
with a microwave tomography approach for reconstructing the
geometrical target properties. The use of the microwave tomography
approach will allow us to obtain more focused and stable
images of the buried objects compared to the ones obtained using
classical migration techniques