1. Five centuries of global temperature change
2. Correlation between ultraviolet radiation and climate
3. Whaleborne sensors probe Arctic waters
4. Stream flow increased sharply in 1970s
5. Energetic atoms can signal changes in space weather
6. Solar wind's influence on heliospheric magnetic field
7. Biomass burning a source of alkyl nitrates
8. Aerosol concentration varies during the day
9. Comparing human, satellite cloud cover observations
10. New method for estimating glacial meltwater

The global average ground temperature has increased by an average of .45 Kelvin [0.81 degrees Fahrenheit, 0.45 degrees Celsius] over the past 200 years and .9 Kelvin [2 degrees Fahrenheit, 0.9 degrees Celsius] during the past 500 years, according to a survey of shallow subsurface measurements by Hugo Beltrami. Using ground surface temperature histories, which can be used to recreate historical temperature perturbations, he also identified a small average heat flux increase since the year 1800. Beltrami collected data from more than 800 temperature-depth samples from all continental areas, mostly from mining exploration sites, and estimated the global energy balance at the Earth's surface and the ground surface temperature history for the last five centuries. His results, which are similar to findings from analytical model predictions, can be used in land surface models and past climate reconstructions.

Title: Climate from borehole data: Energy fluxes and temperatures since 1500

Author:
Hugo Beltrami, St. Francis Xavier University, Antigonish, Nova Scotia, Canada.

Source: Geophysical Research Letters (GRL) paper:10.1029/2002GL015702, 2002

A new assessment of the types of radiation coming from the Sun may allow researchers to better estimate the link between solar emissions and climate on Earth. Peter Foukal presents an improved estimate of the Sun's variable total and ultraviolet outputs, which have distinct signatures that can be differentiated using data
available over most of the past century. Previous estimates of the Sun's variable outputs were not able to distinguish as accurately between the ultraviolet and total light variability. Foukal estimates that ultraviolet irradiance variation might account for no more than 20 percent of the global warming in the 20th century, but that the variation in the Sun's total output might account for much more of the warming. He also suggests that the new data may also help explain the correlation found in previous studies between the Sun's variability and climate since the last Ice Age.

Title: A comparison of variable solar total and ultraviolet irradiance outputs in the 20th century

Author:
Peter Foukal, Heliophysics, Inc., Nahant, Massachusetts.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL015474, 2002

Norwegian and UK scientists used whale-mounted water temperature and depth sensors to measure the salinity and temperature patterns of an Arctic fjord during its initial winter freezing. When they analyzed the new data, Lydersen et al. discovered a previously unreported inflow of warm water from the North Atlantic under the ice-covered fjord. Because of the region's extensive ice cover, collecting enough water samples to analyze the high-Arctic water structure had been nearly impossible during much of the year. The researchers, however, attached satellite-linked, conductivity-temperature-depth monitors to wild white whales, which routinely feed at the bottom of the fjord, to gather previously the unavailable information. Monitoring the changes to the water near the Arctic can help researchers 
estimate deepwater formation and movement and track other oceanic changes potentially induced by global warming.

Title: Salinity and temperature structure of a freezing Arctic fjord-monitored by white whales (Delphinapterus leucas)

Authors:
Christian Lydersen, Ole Anders Nost, Kit M. Kovacs, Norwegian Polar Institue Tromsoe, Norway;
Phil Lovell, Bernie J. McConnell, Colin Hunter, Michael A. Fedak, University of St. Andrews, Fife, Scotland, UK;
Tor Gammelsrod, the University Courses on Svalbard, Longyearbyen, Norway, and University of Bergen, Bergen, Norway.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL015462, 2002

Stream flow levels in the contiguous United States increased sharply near 1970 and have remained relatively unchanged since, an indication that stream flow increases are likely not a gradually rising trend. McCabe and Wolock analyzed nearly 60 years of stream flow data recorded from a nationwide array of 400 U.S.
streams, finding a demonstrable "step" increase in the median and minimum water levels around 1970, which they attribute to increase in precipitation, particularly along the East Coast. The maximum stream flow conditions showed less significant variation. The abrupt change in stream flow typically signals a climate system shift that often will remain constant until a new shift occurs; such shifts are relatively common, occurring in near-decadal patterns, and are often related to changes in ocean temperature and circulation patterns.

Title: A step increase in streamflow in the conterminous United States

Authors:
Gregory J. McCabe, U.S. Geological Survey, Denver, Colorado;
David M. Wolock, U.S. Geological Survey, Lawrence, Kansas.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL015999, 2002

The first remote measurement of energetic neutral atoms in the Earth's plasma sheet indicates that their emissions can be used to accurately monitor space weather and may help predict major geomagnetic storms. McComas et al. present the initial spacecraft observations of the atoms, which are located near the midpoint of
the Earth's charged particle shield. The authors found that high emissions preceded and persisted through the growth of magnetic storms, while low emissions following storms were caused by the depletion of the plasma sheet. High emissions from the sheet, where plasma is added to feed magnetic storms, are associated with dense solar winds buffeting the Earth. The researchers conclude that observations of the neutral atoms, along with monitoring the interplanetary magnetic field orientation, could provide a better approximation of space weather conditions.

Title: Filling and emptying the plasma sheet: Remote observations with 1-70 keV energetic neutral atoms

Authors:
David J. McComas, P. Valek, J. L. Burch, C. J. Pollock, Southwest Research Institute, San Antonio, Texas;
R. M. Skoug, M. F. Thomsen, Los Alamos National Laboratory, Los Alamos, New Mexico.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL016153, 2002

The motion of magnetic field lines across the solar corona has a significant impact on the orientation of the heliospheric magnetic field, a finding that could improve researchers' understanding of the evolution of solar winds and the behavior of space-borne particles that affect Earth's weather. Murphy et al. analyzed observations of regions between fast- and slow-moving solar winds from the Ulysses spacecraft and suggest that the rarefaction areas exhibit behavior that cannot be explained by the current, commonly used Parker model. The authors present a new model that explains large deviations in the angle of the heliospheric
magnetic field seen in observations far from the Sun. Their results could refine existing theories and test the validity of recent models,  which predict how magnetic field lines move in the solar corona.

Title: Strongly underwound magnetic fields in co-rotating rarefaction regions: Observations and implications

Authors:
Neil Murphy, E. J. Smith, Jet Propulsion Laboratory, Pasadena, California;
Nathan A. Schwadron, Southwest Research Institute, San Antonio, Texas.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL015164, 2002

Biomass burning is a newfound source of environmentally damaging alkyl nitrates, according to researchers who have studied gaseous emissions from Australian bushfires. Simpson et al. report the first observations of alkyl nitrates from savannah burning, which they attribute directly to the blaze. Alkyl nitrates are a
component of reactive nitrogen, a compound that affects ozone levels and other elements of atmospheric chemistry and can be carried by the wind and affect otherwise-pristine remote areas. Previously, scientists believed that its presence in remote areas was caused exclusively by saltwater emissions or atmospheric chemical reactions. The authors found that high temperatures from fires can initiate alkyl nitrate formation and, in some instances, can raise the local emissions more than 100 times above normal levels. They conclude that the contribution from widespread biomass burning is unlikely to have a major impact on global reactive nitrogen levels.

Title: A biomass burning source of C1-C4 alkyl nitrates

Authors:
Isobel J. Simpson, Simone Meinardi, Donald R. Blake, Nicola J. Blake, F. S. Rowland, University of California, Irvine, California;
Elliot Atlas, Frank Flocke, National Center for Atmospheric Research, Boulder, Colorado.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL016290, 2002

Aerosol concentrations can vary significantly over the course of a day near source regions over the land, which can exacerbate pollution and influence human health and the climate. Smirnov et al. analyzed nearly 10 years of aerosol measurements from a network covering much of the western hemisphere and suggest that
the daily cycle of local sources of aerosols, like biomass burning and industrial emissions, cause a diurnal trend in the pollutant optical depth. Their survey found, however, very little diurnal change over the oceans. The authors studied the variability of airborne aerosols over wide swaths of the United States, South
America, and Africa, noting up to a 40 percent increase in the optical depth of aerosols during the daytime and most prevalent in afternoons for urban sites.

Title: Diurnal variability of aerosol optical depth observed at AERONET (Aerosol Robotic Network) sites

Authors:
Alexander Smirnov, T. F. Eck, NASA Goddard Space Flight Center, Greenbelt, Maryland, and Goddard Earth Sciences and Technology Center, University of Maryland, Baltimore, Maryland;
B. N. Holben, Goddard Earth Sciences and Technology Center, University of Maryland, Baltimore, Maryland;
I. Slutsker, NASA Goddard Space Flight Center, Greenbelt, Maryland, and Science Systems and Applications, Inc., Lanham, Maryland;
B. Chatenet, University of Paris, Creteil, France;
R. T. Pinker, University of Maryland, College Park, Maryland.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL016305, 2002

The loss of detailed cloud cover recordings can likely be remedied by remote observations that will help researchers continue long-term climate studies over the continental United States. Bomin Sun suggests that, despite a large possible range, satellite cloud data is closely correlated to traditional surface observations,
which will allow researchers to substitute the satellite observations for data previously recorded by humans. After the nationwide implementation of an automated observation system in the early  1990s, a network of computers has recorded cloud information, replacing human ground-based cloud observations. The automated system does not, however, consider the type of cloud cover or high-level cloud cover. The absence of such information is a potential hindrance to atmospheric researchers, who use cloud statistics to infer trends and variables that affect climate change.

Title: Cloudiness over the contiguous United States: Contemporary changes observed using ground-based and ISCCP D2 data

Author:
Bomin Sun, National Climatic Data Center, Asheville, North Carolina.

Source: Geophysical Research Letters (GRL) paper: 10.1029/2002GL016305, 2002

A new method to assess the melting rate beneath floating ice shelves in the Southern Ocean may provide an improved estimate for the freshwater balance around the Antarctic continent and a better understanding of the global ocean circulation. Hohmann et al. describe a way to determine the neon content, in addition to the
currently used helium, to track the amount of meltwater originating from under an ice shelf. Both gases are found in air bubbles trapped in glacial ice and are released in the water when it melts, and both gases dissolve at high pressure. Helium is, however, also present in other freshwater sources. The researchers used both helium and neon concentrations to calculate the meltwater inventory in the southeast Pacific, finding a melting rate comparable to previous estimates. Glacial meltwater is a significant part of cold, dense bottom and deep water formed around Antarctica and shared by the world's oceans.

Title: Excess helium and neon in the southeast Pacific: Tracers for glacial meltwater

Authors:
Roland Hohmann, P. Schlosser, S. Jacobs, A. Ludin, R. Weppernig, Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York.

Source: Journals of Geophysical Research-Oceans (JGR-C)  paper: 10.1029/2000JC000378, 2002

*****
Ordering information for science writers

Journalists and public information officers of educational and scientific institutions (only) may receive one or more of the papers cited in the Highlights by sending a message to Emily Crum at ecrum@agu.org, indicating which one(s). Include your name, the name of your publication, and your phone and fax number. State
whether you prefer to receive the paper(s) as pdf attachments by email or as a fax.

Others should send a request to service@agu.org, citing the doi of the paper (number beginning 10.1029/....), to order a copy of the paper.

The Highlights and the papers to which they refer are not under AGU embargo.
###