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Call Off the Quest
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Over the past 30 years, the climate research community has made valiant efforts to answer the “climate sensitivity” question: What is the long-term equilibrium warming response to a doubling of atmospheric carbon dioxide? Earlier this year, the Intergovernmental Panel on Climate Change (1) concluded that this sensitivity is likely to be in the range of 2° to 4.5°C, with a 1-in-3 chance that it is outside that range. The
lower bound of 2°C is slightly higher than the 1.6°C proposed in the 1970s (2).
26 OCTOBER 2007 VOL 318 SCIENCE
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A westward extension of the warm pool leads to a westward extension of the Walker circulation, drying eastern Africa
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Observations and simulations link anthropogenicgreenhouse and aerosol emissions with rapidly
increasing Indian Ocean sea surface temperatures (SSTs). Over the past 60 years, the Indian Ocean warmed two to three times faster than the central tropical Pacific, extending the tropical warm pool to the west by *40 longitude ([4,000 km). This propensity toward rapid warming in the Indian Ocean has been the dominant mode of interannual variability among SSTs throughout the tropical Indian and Pacific Oceans (55E–140W) since at least 1948, explaining more variance than anomalies associated with the El Nin˜o-Southern Oscillation (ENSO). In the atmosphere, the primary mode of variability has been a corresponding trend
toward greatly increased convection and precipitation over the tropical Indian Ocean. The temperature and rainfall increases in this region have produced a westward extension of the western, ascending branch of the atmospheric Walker circulation. Diabatic heating due to increased mid-tropospheric water vapor condensation elicits a westward atmospheric response that sends an easterly flow of dry air aloft toward eastern Africa. In recent decades (1980–2009), this response has suppressed convection over tropical eastern Africa, decreasing precipitation during the ‘long-rains’ season of March–June. This trend toward drought contrasts with projections of increased rainfall in eastern Africa and more ‘El Nin˜o-like’ conditions globally by the Intergovernmental Panel on Climate Change. Increased Indian Ocean SSTs appear likely to continue to strongly modulate the Warm Pool circulation, reducing precipitation in eastern Africa, regardless of whether the projected trend in ENSO is realized. These results have important food security implications,
informing agricultural development, environmental conservation, and water resource planning.
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Ecological responses to recent climate change
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There is now ample evidence of the ecological impacts of recent climate change, from polar terrestrial to tropical marine environments. The responses of both flora and fauna span an array of ecosystems and organizational hierarchies, from the species to the community levels. Despite continued uncertainty as to community and ecosystem trajectories under global change, our review exposes a coherent pattern of ecological change across systems. Although we are only at an early stage in the projected trends of global warming, ecological responses to recent climate change are already clearly visible.
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Columbia Water Center White Paper America’s Water Risk: Water Stress and Climate Variability
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The emerging awareness of the dependence of business on water has resulted in increasing awareness of the concept of “Water Risk” and the diverse ways in which water can pose threats to businesses in certain regions and sectors. Businesses seek to secure sustainable income. To do so, they need to maintain a
competitive advantage and brand differentiation. They need secure and stable supply chains. Their exposure risks related to increasing scarcity of water can come in a variety of forms at various points in the supply chain. Given increasing water scarcity and the associated deterioration of the quantity and quality of water sources in many parts of the world, many “tools” have been developed to map water scarcity riskor water risk. Typically, these tools are based on estimates of the average water supply and demand in each unit of analysis.Often, they are associated with river basins, while business is associated with cities or counties. They provide a useful first look at the potential imbalance of supply and demand to businesses.
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Conservation VALUE OF ROADLESS AREAS FOR VULNERABLE FISH AND Wildlife Species in the Crown of the Continent Ecosystem, Montana
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The Crown of the Continent Ecosystem is one of the most spectacular landscapes
in the world and most ecologically intact ecosystem remaining in the
contiguous United States. Straddling the Continental Divide in the heart of the
Rocky Mountains, the Crown of the Continent Ecosystem extends for >250
miles from the fabled Blackfoot River valley in northwest Montana north to Elk
Pass south of Banff and Kootenay National Parks in Canada. It reaches from
the short-grass plains along the eastern slopes of the Rockies westward nearly
100 miles to the Flathead and Kootenai River valleys. The Crown sparkles with
a variety of dramatic landscapes, clean sources of blue waters, and diversity of
plants and animals.Over the past century, citizens and government leaders have worked hard to
save the core of this splendid ecosystem in Montana by establishing world-class
parks and wildernesses – coupled with conservation of critical wildlife habitat
on state and private lands along the periphery. These include jewels such as
Glacier National Park, the Bob Marshall-Scapegoat-Great Bear Wilderness,
the first-ever Tribal Wilderness in the Mission Mountains, numerous State of
Montana Wildlife Management Areas (WMAs), and vital private lands through
land trusts such as The Nature Conservancy. Their combined efforts have
protected 3.3 million acres and constitute a truly impressive commitment to
conservation. It was a remarkable legacy and great gift …but, in the face of new
challenges, it may not have been enough.
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‘As Earth’s testimonies tell’: wilderness conservation in a changing world
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Too often, wilderness conservation ignores a temporal perspective greater than the past
50 years, yet a long-term perspective (centuries to millennia) reveals the dynamic nature
of many ecosystems. Analysis of fossil pollen, charcoal and stable isotopes, combined
with historical analyses and archaeology can reveal how ongoing interactions between
climatic change, human activities and other disturbances have shaped today’s landscapes
over thousands of years. This interdisciplinary approach can inform wilderness
conservation and also contribute to interpreting current trends and predicting how
ecosystems might respond to future climate change. In this paper, we review literature
that reveals how increasing collaboration among palaeoecologists, archaeologists,
historians, anthropologists and ecologists is improving understanding of ecological
complexity. Drawing on case studies from forested and non-forested ecosystems in
Europe, the Americas, Africa and Australia, we discuss how this integrated approach can
inform wilderness conservation and ecosystem management.
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Animal Versus Wind Dispersal and the Robustness of Tree Species to Deforestation
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Studies suggest that populations of different species do not decline equally after habitat loss. However, empirical tests have been confined to fine spatiotemporal scales and have rarely included plants. Using data from 89,365 forest survey plots covering peninsular Spain, we explored, for each of 34 common tree species, the relationship between probability of occurrence and the local cover of remaining forest. Twenty-four species showed a significant negative response to forest loss, so that decreased forest cover had
a negative effect on tree diversity, but the responses of individual species were highly variable. Animal-dispersed species were less vulnerable to forest loss, with six showing positive responses to decreased forest cover. The results imply that plant-animal interactions help prevent the collapse of forest communities that suffer habitat destruction.
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Carbon sequestration in the U.S. forest sector from 1990 to 2010
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From 1990 through 2005, the forest sector (including forests and wood products) sequestered an average 162 Tg C year1 . In 2005, 49% of the total forest sector sequestration was in live and dead trees, 27% was
in wood products in landfills, with the remainder in down dead wood, wood products in use, and forest floor and soil. The pools with the largest carbon stocks were not the same as those with the largest sequestration rates, except for the tree pool. For example, landfilled wood products comprise only 3% of total stocks but account for 27% of carbon sequestration. Conversely, forest soils comprise 48% of total stocks but account for only 2% of carbon sequestration. For the tree pool, the spatial pattern of carbon stocks was dissimilar to that of carbon flux. On an area basis, tree carbon stocks were highest in the Pacific Northwest, while changes were generally greatest in the upper Midwest and the Northeast. Net carbon sequestration in the forest sector in 2005 offset 10% of U.S. CO2 emissions. In the near future, we project that U.S. forests will continue to sequester carbon at a rate similar to that in recent years. Based on a comparison of our estimates to a compilation of land-based estimates of non-forest carbon sinks from the literature, we estimate that the conterminous U.S. annually sequesters 149–330 Tg C year1. Forests, urban trees, and wood products are responsible for 65–91% of this sink.
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A new, global, multi-annual (2000–2007) burnt area product at 1 km resolution Vol. 35
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This paper reports on the development and validation
of a new, global, burnt area product. Burnt areas are
reported at a resolution of 1 km for seven fire years (2000 to
2007). A modified version of a Global Burnt Area (GBA)
2000 algorithm is used to compute global burnt area. The
total area burnt each year (2000– 2007) is estimated to be
between 3.5 million km2 and 4.5 million km2
. The total
amount of vegetation burnt by cover type according to the
Global Land Cover (GLC) 2000 product is reported.
Validation was undertaken using 72 Landsat TM scenes
was undertaken. Correlation statistics between estimated
burnt areas are reported for major vegetation types. The
accuracy of this new global data set depends on vegetation
type.
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Animal migration amid shifting patterns of phenology and predation: lessons from a Yellowstone elk herd
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Migration is a striking behavioral strategy by which many animals enhance resource acquisition while reducing predation risk. Historically, the demographic benefits of such movements made migration common, but in many taxa the phenomenon is considered globally threatened. Here we describe a long-term decline in the productivity of elk (Cervus elaphus) that migrate through intact wilderness areas to protected summer ranges inside Yellowstone National Park, USA. We attribute this decline to a long-term reduction in the
demographic benefits that ungulates typically gain from migration. Among migratory elk, we observed a 21-year, 70% reduction in recruitment and a 4-year, 19% depression in their pregnancy rate largely caused by infrequent reproduction of females that were young or lactating. In contrast, among resident elk, we have recently observed increasing recruitment and a high rate of pregnancy. Landscape-level changes in habitat quality and predation appear to be responsible for the declining productivity of Yellowstone migrants. From 1989 to 2009, migratory elk experienced an increasing rate and shorter duration of green-up coincident with
warmer spring–summer temperatures and reduced spring precipitation, also consistent with observations of an unusually severe drought in the region. Migrants are also now exposed to four times as many grizzly bears (Ursus arctos) and wolves (Canis lupus) as resident elk. Both of these restored predators consume migratory elk calves at high rates in the Yellowstone wilderness but are maintained at low densities via lethal management and human disturbance in the year-round habitats of resident elk. Our findings suggest that large-carnivore recovery and drought, operating simultaneously along an elevation gradient, have disproportionately influenced the demography of migratory elk. Many migratory animals travel large geographic distances between their seasonal ranges. Changes in land use and climate that disparately
influence such seasonal ranges may alter the ecological basis of migratory behavior, representing an important challenge.
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