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Imlay 1973.pdf
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TRB Library
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HUE-JOH
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Imlay 1977.pdf
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TRB Library
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HUE-JOH
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Imlay Environmental Stimulus.pdf
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TRB Library
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HUE-JOH
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Imlay Vita Publications.pdf
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TRB Library
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HUE-JOH
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Impact of a Century of Climate Change on Small-Mammal Communities in Yosemite National Park, USA
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We provide a century-scale view of small-mammal responses to global warming, without
confounding effects of land-use change, by repeating Grinnell’s early–20th century survey across
a 3000-meter-elevation gradient that spans Yosemite National Park, California, USA. Using
occupancy modeling to control for variation in detectability, we show substantial (~500 meters on
average) upward changes in elevational limits for half of 28 species monitored, consistent with the
observed ~3°C increase in minimum temperatures. Formerly low-elevation species expanded their
ranges and high-elevation species contracted theirs, leading to changed community composition at
mid- and high elevations. Elevational replacement among congeners changed because species’
responses were idiosyncratic. Though some high-elevation species are threatened, protection
of elevation gradients allows other species to respond via migration
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Climate Science Documents
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Impact of deforestation in the Amazon basin on cloud climatology
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Shallow clouds are prone to appear over deforested surfaces whereas deep clouds, much less frequent than shallow clouds, favor forested surfaces. Simultaneous atmospheric soundings at forest and pasture sites during the Rondonian Boundary Layer Experiment (RBLE-3) elucidate the physical mechanisms responsible for the observed correlation between clouds and land cover. We demonstrate that the atmospheric boundary layer over the forested areas is more unstable and characterized by larger values of the convective available potential energy (CAPE) due to greater humidity than that which is found over the deforested area. The shallow convection over the deforested areas is relatively more active than the deep convection over the forested areas. This greater activity results from a stronger lifting mechanism caused by mesoscale circulations driven by deforestation-induced heterogeneities in land cover.
climate land-cover heterogeneity mesoscale circulations
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Impact of disturbed desert soils on duration of mountain snow cover
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Snow cover duration in a seasonally snow covered
mountain range (San Juan Mountains, USA) was found to
be shortened by 18 to 35 days during ablation through
surface shortwave radiative forcing by deposition of
disturbed desert dust. Frequency of dust deposition and
radiative forcing doubled when the Colorado Plateau, the
dust source region, experienced intense drought (8 events
and 39–59 Watts per square meter in 2006) versus a year
with near normal precipitation (4 events and 17–34 Watts
per square meter in 2005). It is likely that the current
duration of snow cover and surface radiation budget
represent a dramatic change from those before the
widespread soil disturbance of the western US in the late
1800s that resulted in enhanced dust emission. Moreover,
the projected increases in drought intensity and frequency
and associated increases in dust emission from the desert
southwest US may further reduce snow cover duration
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Impact of reduced Arctic sea ice on Greenland ice sheet variability in a warmer than present climate
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A global climate model with interactive vegetation and a coupled ice sheet-shelf component is used to test the response of the Greenland ice sheet (GIS) to increased sea surface temperatures (SSTs) and reduced sea ice (SI) cover during the mid-Pliocene warm period (∼3 Ma) as reconstructed from proxy records. Seasonally open water in the Arctic and North Atlantic are shown to alter regional radiation budgets, storm tracks, and moisture and heat advection into the Greenland interior, with increases in temperature rather than precipitation dominating the ice sheets response. When applied to an initially glaciated Greenland, the presumed warm, ice-free Pliocene ocean conditions induce rapid melting of nearly the entire ice sheet and preclude a modern-like GIS from (re)growing, regardless of orbital forcing. The sensitivity of Greenland to imposed Pliocene ocean conditions may have serious implications for the future response of the ice sheet to continued warming in the Arctic basin.
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Impact of terrestrial biosphere carbon exchanges on the anomalous CO2 increase in 2002–2003
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Understanding the carbon dynamics of the terrestrial
biosphere during climate fluctuations is a prerequisite for
any reliable modeling of the climate-carbon cycle feedback.
We drive a terrestrial vegetation model with observed
climate data to show that most of the fluctuations in
atmospheric CO2 are consistent with the modeled shift in
the balance between carbon uptake by terrestrial plants and
carbon loss through soil and plant respiration. Simulated
anomalies of the Fraction of Absorbed Photosynthetically
Active Radiation (FAPAR) during the last two El Nin˜o
events also agree well with satellite observations. Our
model results suggest that changes in net primary
productivity (NPP) are mainly responsible for the
observed anomalies in the atmospheric CO2 growth rate.
Changes in heterotrophic respiration (Rh) mostly happen in
the same direction, but with smaller amplitude. We attribute
the unusual acceleration of the atmospheric CO2 growth rate
during 2002–2003 to a coincidence of moderate El Nin˜o
conditions in the tropics with a strong NPP decrease at
northern mid latitudes, only partially compensated by
decreased
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Impact of terrestrial biosphere carbon exchanges on the anomalous CO2 increase in 2002–2003
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Concluding paragraphs:
In general, we find that the remarkable feature of the 2002– 2003 anomaly seems to be that climate fluctuations, not only related to El Nin ̃o and occurring across all latitudes, acted together to create an unusually strong outgasing of CO2 of the terrestrial biosphere. Further research will be required to investigate if this fluctuation carries features of projected future climate change and the CO2 growth rate anomaly has been a first indicator of a developing positive feedback between climate warming and the global carbon cycle.
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