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1.
Long-term aridity changes in the western United States   总被引:7,自引:0,他引:7  
The western United States is experiencing a severe multiyear drought that is unprecedented in some hydroclimatic records. Using gridded drought reconstructions that cover most of the western United States over the past 1200 years, we show that this drought pales in comparison to an earlier period of elevated aridity and epic drought in AD 900 to 1300, an interval broadly consistent with the Medieval Warm Period. If elevated aridity in the western United States is a natural response to climate warming, then any trend toward warmer temperatures in the future could lead to a serious long-term increase in aridity over western North America.  相似文献   

2.
Warming and earlier spring increase western U.S. forest wildfire activity   总被引:2,自引:0,他引:2  
Western United States forest wildfire activity is widely thought to have increased in recent decades, yet neither the extent of recent changes nor the degree to which climate may be driving regional changes in wildfire has been systematically documented. Much of the public and scientific discussion of changes in western United States wildfire has focused instead on the effects of 19th- and 20th-century land-use history. We compiled a comprehensive database of large wildfires in western United States forests since 1970 and compared it with hydroclimatic and land-surface data. Here, we show that large wildfire activity increased suddenly and markedly in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations, and longer wildfire seasons. The greatest increases occurred in mid-elevation, Northern Rockies forests, where land-use histories have relatively little effect on fire risks and are strongly associated with increased spring and summer temperatures and an earlier spring snowmelt.  相似文献   

3.
A U.S. national assessment, drawing on the best available climate model predictions, has concluded that the United States will indeed warm, affecting everything from the western snowpacks that supply California with water to New England's fall foliage. But on a more detailed level, the assessment often draws a blank. As much as policy-makers would like to know exactly what's in store for Americans, the rudimentary state of regional climate science will not soon allow it, and the results of this 3-year effort brought the point home.  相似文献   

4.
The cause of decadal climate variability over the North Pacific Ocean and North America is investigated by the analysis of data from a multidecadal integration with a state-of-the-art coupled ocean-atmosphere model and observations. About one-third of the low-frequency climate variability in the region of interest can be attributed to a cycle involving unstable air-sea interactions between the subtropical gyre circulation in the North Pacific and the Aleutian low-pressure system. The existence of this cycle provides a basis for long-range climate forecasting over the western United States at decadal time scales.  相似文献   

5.
A response of plant growth to increased atmospheric carbon dioxide, which has been anticipated from laboratory data, may now have been detected in the annual rings of subalpine conifers growing in the western United States. Experimental evidence shows that carbon dioxide can be an important limiting factor in the growth of plants in this high-altitude environment. The greatly increased tree growth rates observed since the mid-l9th century exceed those expected from climatic trends but are consistent in magnitude with global trends in carbon dioxide, especially in recent decades. If correctly interpreted, these findings have important implications for climate studies involving tree ring observations and for models of the global carbon dioxide budget.  相似文献   

6.
The effects of increasing carbon dioxide (CO2) and climate on net carbon storage in terrestrial ecosystems of the conterminous United States for the period 1895-1993 were modeled with new, detailed historical climate information. For the period 1980-1993, results from an ensemble of three models agree within 25%, simulating a land carbon sink from CO2 and climate effects of 0.08 gigaton of carbon per year. The best estimates of the total sink from inventory data are about three times larger, suggesting that processes such as regrowth on abandoned agricultural land or in forests harvested before 1980 have effects as large as or larger than the direct effects of CO2 and climate. The modeled sink varies by about 100% from year to year as a result of climate variability.  相似文献   

7.
The perfect ocean for drought   总被引:5,自引:0,他引:5  
The 1998-2002 droughts spanning the United States, southern Europe, and Southwest Asia were linked through a common oceanic influence. Cold sea surface temperatures (SSTs) in the eastern tropical Pacific and warm SSTs in the western tropical Pacific and Indian oceans were remarkably persistent during this period. Climate models show that the climate signals forced separately by these regions acted synergistically, each contributing to widespread mid-latitude drying: an ideal scenario for spatially expansive, synchronized drought. The warmth of the Indian and west Pacific oceans was unprecedented and consistent with greenhouse gas forcing. Some implications are drawn for future drought.  相似文献   

8.
The study of alternatives to conventional industrial agricultural production has intensified in recent years. While many types of alternative production systems, and the motivations of individuals to participate in them, have been studied, there are significant gaps in the literature. One such dearth is research on those participating in self-provisioning activities. This study begins to fill the gap by looking at the self-provisioning activity of home gardening using data from the 2008 Ohio Survey of Food, Agriculture, and Environmental Issues. Discerning who household gardeners are is important given the recent economic, cultural, and political climate of the United States. The results show that home gardening occurs throughout the state of Ohio at surprisingly high levels. Bivariate and multivariate analyses reveal several noteworthy associations between gardening and household characteristics, including spatial location, pro-environmental and economic hardship behaviors, and level of participation in localized food systems.  相似文献   

9.
About 70 percent of tropical western Atlantic mollusk species have become extinct since the Pliocene, which has led to perceptions of a corresponding decline in diversity. However, a compilation of gastropod species from Plio-Pleistocene faunas of the United States Atlantic coastal plain and from Recent western Atlantic faunas indicates that regional diversity has not changed since the Pliocene. Gastropod diversity in the Pliocene Pinecrest Beds in Florida approximates that seen today on either coast of Florida. Gastropod diversity is not demonstrably different in the Recent tropical western Atlantic than in the Recent tropical eastern Pacific. High extinction rates must have been balanced by high origination rates.  相似文献   

10.
Kerr RA 《Science (New York, N.Y.)》2000,290(5493):920-921
The climate treaty being hammered out this month at The Hague may be doomed to failure, as numerous observers say the United States simply won't ratify any treaty that requires such wrenching reductions in carbon emissions, and if the United States bails out, the protocol is in very deep trouble. Some policy analysts think that by tweaking the rules, the United States could eventually sign on, but if they are tweaked too much, other countries may balk. The key, some say, will be keeping the treaty going now and rethinking its controversial goals later.  相似文献   

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