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- Hall, C. Michael, et al.
(author)
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Denying bogus skepticism in climate change and tourism research.
- 2015
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In: Tourism Management. - : Elsevier BV. - 0261-5177 .- 1879-3193. ; 47, s. 352-356
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Journal article (peer-reviewed)abstract
- This final response to the two climate change denial papers by Shani and Arad further highlights the inaccuracies, misinformation and errors in their commentaries. The obfuscation of scientific research and the consensus on anthropogenic climate change may have significant long-term negative consequences for better understanding the implications of climate change and climate policy for tourism and create confusion and delay in developing and implementing tourism sector responses.
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| 2. |
- Hall, C. Michael, et al.
(author)
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No time for smokescreen skepticism : A rejoinder to Shani and Arad
- 2015
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In: Tourism Management. - : Elsevier BV. - 0261-5177 .- 1879-3193. ; 47, s. 341-347
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Journal article (peer-reviewed)abstract
- Shani and Arad (2014) claimed that tourism scholars tend to endorse the most pessimistic assessments regarding climate change, and that anthropogenic climate change was a "fashionable" and "highly controversial scientific topic". This brief rejoinder provides the balance that is missing from such climate change denial and skepticism studies on climate change and tourism. Recent research provides substantial evidence that reports on anthropogenic climate change are accurate, and that human-induced greenhouse gas emissions, including from the tourism industry, play a significant role in climate change. Some positive net effects may be experienced by some destinations in the short-term, but in the long-term all elements of the tourism system will be impacted. The expansion of tourism emissions at a rate greater than efficiency gains means that it is increasingly urgent that the tourism sector acknowledge, accept and respond to climate change. Debate on tourism-related adaptation and mitigation measures is to be encouraged and welcomed. Climate change denial is not.
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| 3. |
- Becken, Michael, et al.
(author)
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DESMEX: A novel system development for semi-airborne electromagnetic exploration
- 2020
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In: Geophysics. - : Society of Exploration Geophysicists. - 0016-8033 .- 1942-2156. ; 85:6, s. 253-267
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Journal article (peer-reviewed)abstract
- There is a clear demand to increase detection depths in the context of raw material exploration programs. Semi-airborne electromagnetic (semi-AEM) methods can address these demands by combining the advantages of powerful transmitters deployed on the ground with efficient helicopter-borne mapping of the magnetic field response in the air.The penetration depth can exceed those of classical airborne EM systems,since low frequencies and large transmitter-receiver offsets can be realized in practice. A novel system has been developed that combines high-moment horizontal electric bipole transmitters on the ground with low-noise three-axis induction coilmagnetometers, a three-axis fluxgate magnetometer and a laser gyroinertial measurement unit integrated within a helicopter-towed airborne platform. The attitude data are used to correct the time series for motional noise and subsequently to rotate into an Earth-fixed reference frame. In a second processing step, and as opposed to existing semi-airborne systems, we transform the data into the frequency domain and estimate the complex-valued transfer functions between the received magnetic field components and the synchronously recorded injection current by regression analysis. This approach is similar to the procedure employed in controlled-source EM. For typical source bipole moments of 20-40 kAm and for rectangular current waveforms with a fundamental frequency of about 10 Hz, we can estimate reliable three-component transfer functions in the frequency range from 10-5000 Hz over a measurement area of 4 x 5 km2 for a single source installation. The system has the potential to be used for focused exploration of deep targets.
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| 7. |
- Kamm, Jochen, et al.
(author)
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Inversion of slingram electromagnetic induction data using a Born approximation
- 2013
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In: Geophysics. - 0016-8033 .- 1942-2156. ; 78:4, s. E201-E212
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Journal article (peer-reviewed)abstract
- We present an efficient approximate inversion scheme for near-surface loop-loop EM induction data (slingram) that can be applied to obtain 2D or 3D models on a normal desktop computer. Our approach is derived from a volume integral equation formulation with an arbitrarily conductive homogeneous half-space as a background model. The measurements are not required to fulfill the low induction number condition (low frequency and conductivity). The high efficiency of the method is achieved by invoking the Born approximation around a half-space background. The Born approximation renders the forward operator linear. The choice of a homogeneous half-space yields closed form expressions for the required electromagnetic normal fields. It also yields a translationally invariant forward operator, i.e., a highly redundant Jacobian. In connection with the application of a matrix-free conjugate gradient method, this allows for very low memory requirements during the inversion, even in three dimensions. As a consequence of the Born approximation, strong conductive deviations from the background model are underestimated. Highly resistive anomalies are in principle overestimated, but at the same time difficult to resolve with induction methods. In the case of extreme contrasts, our forward model may fail in simultaneously explaining all the data collected. We applied the method to EM34 data from a profile that has been extensively studied with other electromagnetic methods and compare the results. Then, we invert three conductivity maps from the same area in a 3D inversion.
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| 8. |
- Pedersen, Laust B., et al.
(author)
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Equivalent images derived from very-low-frequency (VLF) profile data
- 2005
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In: Geophysics. - : Society of Exploration Geophysicists. - 0016-8033 .- 1942-2156. ; 70:3, s. G43-G50
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Journal article (peer-reviewed)abstract
- We describe the implementation of a new fast imaging technique for filtering very-low-frequency (VLF) data measured on profiles into corresponding equivalent current systems in the earth. Single-frequency VLF data using magnetic measurements alone are often used to delineate lateral changes in electrical conductivity, e.g., fracture zones in crystalline terrains or changes in lithology in the sedimentary cover. Here, an attempt is made to add depth information to the conductivity distribution by realizing that the single-frequency VLF profile data contain information about (1) the background medium through their decay away from the conductors, (2) the position, and (3) the depth of the dominating conductors through the relative contribution of in-phase and quadrature components to the VLF anomaly in addition to the rate of change of the anomaly close to the conductors. Synthetic data from a model containing a shallow and a deeper conductor are filtered to show that the estimated current distributions coincide well with the horizontal position of the conductors, but even they provide some smeared images of the depth distribution of the conductors. A comparison with models obtained from regularized inversion of the same data shows good correspondence. The VLF field data from an area with clay lenses overlying wet sand and crystalline basement are filtered into current distributions that grossly mimic the electrical conductivity distribution of the clay lenses as obtained from radiomagnetotelluric measurements along the same profile.
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