WASHINGTON - Will 2010 be the warmest year on record? How do the recent U.S. "Snowmageddon" winter storms and record low temperatures in Europe fit into the bigger picture of long-term global warming? NASA has launched a new web page to help people better understand the causes and effects of Earth's changing climate.

The new "A Warming World" page hosts a series of new articles, videos, data visualizations, space-based imagery and interactive visuals that provide unique NASA perspectives on this topic of global importance.

The page includes feature articles that explore the recent Arctic winter weather that has gripped the United States, Europe and Asia, and how El Nino and other longer-term ocean-atmosphere phenomena may affect global temperatures this year and in the future. A new video, "Piecing Together the Temperature Puzzle," illustrates how NASA satellites monitor climate change and help scientists better understand how our complex planet works.

The new web page is available on NASA's Global Climate Change Web site at: http://climate.nasa.gov/warmingworld

For more information about NASA and agency programs, visit: http://www.nasa.gov

Source: NASA

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After analyzing historical records and climate model data for two major U.S. droughts in the 1930s and 1950s, NOAA scientists found two very different causes, shedding new light on our understanding of what triggers drought. Studies such as this one that expand our insights into drought are essential for improving forecasts and can aid in the creation of an early warning system to help communities take precautions and prepare.

"In the case of the severe 1950s drought of the Southern Plains states, it appears global sea surface temperatures were the principal cause. However, the 1930s 'Dust Bowl' drought over the central and northern Plains states was not caused by ocean conditions, but rather the evidence points to random changes in the atmosphere as the instigator in that event," said Martin Hoerling, lead author and a meteorologist at NOAA's Earth System Research Laboratory in Boulder, Colo. The work, "Distinct Causes for Two Principal U.S. Droughts of the 20th Century (abstract only if not subscriber)," is currently available online and will be published in the October 16 edition of Geophysical Research Letters.

Scientists studied two national events - one over the Southern Plains during 1946-1956 and the other in the central and northern Plains during 1932-1939, commonly known as the Dust Bowl period. The authors note that the two events are considered the most severe and prolonged droughts over the Great Plains since 1895. In the United States, the Plains encompass roughly the area west of the Mississippi River and east of the Rocky Mountains. It has been long held that droughts are influenced by sea surface temperatures. But the NOAA scientists saw differences in the two droughts they studied and delved deeper into the causes.

"Our finding that the 1930s Dust Bowl drought was likely caused by a random change in the atmosphere does conflict with earlier scientific studies," said Hoerling. "But in our analysis, using a more extensive set of model experiments and diagnostic tests, the prior speculation that the Dust Bowl drought had early warning indicators in the ocean temperatures could not be supported." However, the evidence surrounding the Southern Plains drought does point to sea surface temperatures as the driver for that decade-long event that began in 1946. The authors note that the Southern Plains region is more sensitive to sea surface temperatures than the Northern Plains due to its proximity to tropical Pacific Ocean-influenced weather patterns.

"Both the observations, as well as the simulations show strong and frequent La Niñas during Southern Plains drought," said Hoerling. "Droughts are common in that region during La Niña years." La Niña is characterized by unusually cold water temperatures in the equatorial Pacific Ocean as opposed to El Niño which reflects unusually warm temperatures. These events can affect global weather patterns; in the United States, La Niña often signals drier-than-normal conditions in the southwest and central Plains regions, and wetter fall and winter seasons in the Pacific Northwest.

The authors note that while an ocean observing system - a network of instruments including stationary and free-floating buoys as well as satellites - is vital to any drought early warning system, it may not adequately warn of a drought caused by other factors, and may not provide early warning for a drought over the northern Plains states, such as what occurred in the 1930s.

Xiao-Wei Quan and Jon Eischeid from the Physical Sciences Division of NOAA's Earth System Research Laboratory in Boulder, Colo., also are authors on the paper.

Source: NOAA

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Recent tree loss, largely driven by climate stress, in forests around the world could portend increased tree mortality under climate change, according to a U.S. Geological Survey (USGS) report recently released online in the journal Forest Ecology and Management.

The USGS-led review suggests that many of the world's forests are sensitive to climate-related drought and heat stress, raising the concern that forests may become increasingly vulnerable to future mortality, even in environments that are not normally considered water-limited. The results suggest risks to ecosystem services that are valuable to forests and societies around the world.

"Trees can die much more quickly than they grow," said Craig D. Allen, USGS scientist and lead author of the report. "The widespread examples of drought and heat-induced tree mortality that we document illustrate how climate can drive abrupt, broad-scale impacts to essential forest services ranging from timber and protection of watersheds and biodiversity to recreational, aesthetic and spiritual benefits."

Although tree mortality episodes occur in the absence of climate change, the report's results are consistent with projections of future increases in tree mortality due to climate-related stresses. These heat and drought stresses could fundamentally alter the composition, structure and biogeography of forests in many regions, as well as affect how forests sequester carbon.

"This work by USGS underscores multiple risks that climate change poses to our forests and our world," said Secretary of the Interior Ken Salazar. "It also illuminates the importance of our efforts to develop practical, on-the-ground land management strategies that will help us adjust to the stresses that climate change is placing on our forests."

The report details 88 cases of significant tree mortality around the world associated with heat and drought since 1970, documenting climate-induced tree losses from Africa, Asia, Australia, Europe, North America and South America.

"From northern forests of spruce, pine or oak to tropical savannas and rainforests, many forest types appear vulnerable to such climate-driven mortality and to forest pests that are also highly sensitive to temperature," Allen said.

The report also identifies key information gaps and scientific uncertainties that currently hinder our ability to identify climate-related trends in tree mortality and to predict future losses in response to climate change, including lack of species-specific knowledge about tree water and temperature stress limits and the absence of a globally coordinated observation system.

However, in conjunction with other recent observational and experimental studies indicating that higher temperatures can drive increases in tree mortality, this article highlights risks that tree mortality could become more frequent and extensive as global climate change progresses.

Source: USGS

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