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Monday, January 12, 2015

Two decades of bias found in western US mountain climate measurements at higher elevations, compromised ability to correctly assess snowpack, bias spread to other 'climate products,' 1991-2012 high elevation temp. trends statistically indistinguishable from lower elevation trends-GRL peer reviewed study

1/9/15, "Artificial Amplification of Warming Trends Across the Mountains of the Western United States," Geophysical Research Letters, Jared W. Oyler, Solomon Z. Dobrowski, Ashley P. Ballantyne, Anna E. Klene, Steven W. Running

"This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/2014GL062803.

Abstract

Observations from the main mountain climate station network in the western United States (US) suggest that higher elevations are warming faster than lower elevations. This has led to the assumption that elevation-dependent warming is prevalent throughout the region with impacts to water resources and ecosystem services. Here, we critically evaluate this network's temperature observations and show that extreme warming observed at higher elevations is the result of systematic artifacts and not climatic conditions. 

With artifacts removed, the network's 1991–2012 minimum temperature trend decreases from +1.16 °C decade−1 to +0.106 °C decade−1 and is statistically indistinguishable from lower elevation trends. Moreover, longer-term widely used gridded climate products propagate the spurious temperature trend, thereby amplifying 1981–2012 western US elevation-dependent warming by +217 to +562%. In the context of a warming climate, this artificial amplification of mountain climate trends has likely compromised our ability to accurately attribute climate change impacts across the mountainous western US."

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"The SNOTEL bias has likely compromised our ability to understand the unique drivers and impacts of climate change in western U.S. mountains."

1/9/15, "Mountain system artificially inflates temperature increases at higher elevations," sciencecodex.com

"In a recent study, University of Montana and Montana Climate Office researcher Jared Oyler found that the western U.S. has warmed, just not as much as claimed.

The results show that sensor changes have significantly biased temperature observations from the Snowpack Telemetry (SNOTEL) station network. More than 700 SNOTEL sites monitor temperature and snowpack across the mountainous western U.S. SNOTEL provides critical data for water supply forecasts. Researchers often use SNOTEL data to study mountain climate trends and impacts to mountain hydrology and ecology.

Oyler and his co-authors applied statistical techniques to account for biases introduced when equipment was switched at SNOTEL sites in the mid-1990s to mid-2000s. 

His revised datasets reduced the biases to reveal that high-elevation minimum temperatures were warming only slightly more than minimum temperatures at lower elevations.

"Observations from other station networks clearly show that the western U.S. has experienced regional warming," Oyler said, "but to assess current and future climate change impacts to snowpack and important mountain ecosystem processes, we need accurate observations from the high elevation areas only covered by the SNOTEL network. The SNOTEL bias has likely compromised our ability to understand the unique drivers and impacts of climate change in western U.S. mountains."
 
Published in the journal Geophysical Research Letters. Co-authors on the paper "Artificial Amplification of Warming Trends Across the Mountains of the Western United States" include UM researchers Solomon Dobrowski, Ashley Ballantyne, Anna Klene and Steve Running. It is available online at http://onlinelibrary.​wiley.​com/​enhanced/​doi/​10.​1002/​2014GL062803/ . via wuwt



His results, published Jan. 9 in the journal Geophysical Research Letters, show that sensor changes have significantly biased temperature observations from the Snowpack Telemetry (SNOTEL) station network.
More than 700 SNOTEL sites monitor temperature and snowpack across the mountainous western U.S. SNOTEL provides critical data for water supply forecasts. Researchers often use SNOTEL data to study mountain climate trends and impacts to mountain hydrology and ecology.
Oyler and his co-authors applied statistical techniques to account for biases introduced when equipment was switched at SNOTEL sites in the mid-1990s to mid-2000s.
His revised datasets reduced the biases to reveal that high-elevation minimum temperatures were only slightly more than minimum temperatures at lower elevations.
"Observations from other station networks clearly show that the western U.S. has experienced regional warming," Oyler said, "but to assess current and future change impacts to snowpack and important mountain ecosystem processes, we need accurate observations from the high elevation areas only covered by the SNOTEL network. The SNOTEL bias has likely compromised our ability to understand the unique drivers and in western U.S. mountains."
Co-authors on the paper "Artificial Amplification of Warming Trends Across the Mountains of the Western United States" include UM researchers Solomon Dobrowski, Ashley Ballantyne, Anna Klene and Steve Running. It is available online at onlinelibrary.wiley.com/enhanc… 0.1002/2014GL062803/ .


Read more at: http://phys.org/news/2015-01-mountain-artificially-inflates-temperature-higher.html#jCp
In a recent study, University of Montana and Montana Climate Office researcher Jared Oyler found that while the western U.S. has warmed, recently observed warming in the mountains of the western U.S. likely is not as large as previously supposed.

Read more at: http://phys.org/news/2015-01-mountain-artificially-inflates-temperature-higher.html#jCp





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