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Mapping Climate Change in the Oceans
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NOAA Research and NOAA Fisheries collaborate on new method to assess fish vulnerability to climate change
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Mapping tree density at a global scale
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The global extent and distribution of forest trees is central to our understanding of the terrestrial biosphere. We provide the first spatially continuous map of forest tree density at a global scale. This map reveals that the global number of trees is approximately 3.04 trillion, an order of magnitude higher than the previous estimate. Of these trees, approximately 1.39 trillion exist in tropical and subtropical forests, with 0.74 trillion in boreal regions and 0.61 trillion in temperate regions. Biome-level trends in tree density demonstrate the importance of climate and topography in controlling local tree densities at finer scales, as well as the overwhelming effect of humans across most of the world. Based on our projected tree densities, we estimate that over 15 billion trees are cut down each year, and the global number of trees has fallen by approximately 46% since the start of human civilization.
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Climate Science Documents
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McKenney et al 2007 N Am trees_climate change.pdf
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Project Documents
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Literature
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McLachlan et al_2005_tree migration_climate change.2005.pdf
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Literature
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Medieval warming initiated exceptionally large wildfire outbreaks in the Rocky Mountains
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Many of the largest wildfires in US history burned in recent decades, and climate change explains much of the increase in area burned. The frequency of extreme wildfire weather will increase with continued warming, but many uncertainties still exist about future fire regimes, including how the risk of large fires will persist as vegetation changes. Past fire-climate relationships provide an opportunity to constrain the related uncertainties, and reveal widespread burn- ing across large regions of western North America during past warm intervals. Whether such episodes also burned large portions of individual landscapes has been difficult to determine, however, because uncertainties with the ages of past fires and limited spatial resolution often prohibit specific estimates of past area burned. Accounting for these challenges in a subalpine landscape in Colorado, we estimated century-scale fire synchroneity across 12 lake- sediment charcoal records spanning the past 2,000 y. The percent- age of sites burned only deviated from the historic range of vari- ability during the Medieval Climate Anomaly (MCA) between 1,200 and 850 y B.P., when temperatures were similar to recent decades. Between 1,130 and 1,030 y B.P., 83% (median estimate) of our sites burned when temperatures increased ∼0.5 °C relative to the preceding centuries. Lake-based fire rotation during the MCA decreased to an estimated 120 y, representing a 260% higher rate of burning than during the period of dendroecological sampling (360 to −60 y B.P.). Increased burning, however, did not persist throughout the MCA. Burning declined abruptly before temperatures cooled, indicating possible fuel limitations to continued burning.
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Monthly carbon dioxide levels hit new milestone
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NOAA scientists reported that in March 2015 the monthly average global carbon dioxide level went above 400 parts per million for the first time.
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Mountain Streams Offer Climate Refuge
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A new study offers hope for cold-water species in the face of climate change. The study, published today in the Proceedings of the National Academy of Sciences, addresses a longstanding paradox between predictions of widespread extinctions of cold-water species and a general lack of evidence for those extinctions despite decades of recent climate change.
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Mountains to Sound Greenway Trust
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The Mountains to Sound Greenway National Heritage Area is a unique geographic corridor made up of connected ecosystems and communities spanning 1.5 million acres from Seattle to Ellensburg along Interstate-90 in Washington state. The Mountains to Sound Greenway Trust is a coalition-based organization that leads and inspires action to conserve and enhance this special landscape, ensuring a long-term balance between people and nature.
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Multi-year drought-induced morbidity preceding tree death in Southeastern US forests
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Recent forest diebacks combined with threats of future drought focus attention on the extent to which tree death is caused by catastrophic events as opposed to chronic declines in health that accumulate over years. While recent attention has focused on large-scale diebacks, there is concern that increasing drought stress and chronic morbidity may have pervasive impacts on forest composition in many regions. Here we use long-term, whole-stand inventory data from Southeastern US forests to show that trees exposed to drought experience multi-year declines in growth prior to mortality. Following a severe, multi-year drought, 72% of trees that did not recover their pre-drought growth rates died within 10 years. This pattern was mediated by local moisture availability. As an index of morbidity prior to death, we calculated the difference in cumulative growth after drought relative to surviving conspecifics. The strength of drought-induced morbidity varied among species and was correlated with drought tolerance. These findings support the ability of trees to avoid death during drought events but indicate shifts that could occur over decades. Tree mortality following drought is predictable in these ecosystems based on growth declines, highlighting an opportunity to address multi-year drought-induced morbidity in models, experiments, and management decisions.
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Climate Science Documents
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Multistability and Critical Thresholds of the Greenland Ice Sheet
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Recent studies have focused on the short-term contribution of the Greenland ice sheet to sea-level rise, yet little is known about its long-term stability. The present best estimate of the threshold in global temperature rise leading to complete melting of the ice sheet is 3.1 °C (1.9–5.1 °C, 95% confidence interval) above the preindustrial climate, determined as the temperature for which the modeled surface mass balance of the present-day ice sheet turns negative. Here, using a fully coupled model, we show that this criterion systematically overestimates the temperature threshold and that the Greenland ice sheet is more sensitive to long-term climate change than previously thought.
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