Give us a sense of what’s really happening with climate change on our planet right now. I think you want to side-step that question and talk about whatpeople are doing to study this problem. Who are these people who aregoing out and measuring ocean temperatures? Who are these people who aretracking the year-on-year retreat of the Arctic sea ice? Who are thesepeople who are going out and measuring the small processes involved incloud formation, in soil moisture retention, in ocean eddies, inevaporation? It’s these things that we then put together to build thenumerical simulations that I work on, these climate models, that we’reusing to help us piece together what’s happened in the past, what’shappening now, and what’s likely to happen in the future. I think it’s far more important that people get a sense of thescience as a work in progress, rather than one particular message orpiece of content knowledge getting hammered home.
An interesting new study published in Nature points out that an increase in the strength of the Arctic Oscillation between 2005 and 2008 caused winds in the region to grow more cyclonic and shift ocean currents in ways that drew more upper-surface freshwater from Russian rivers toward the Canada Basin and the Beaufort Sea. To see the shift in the animation above, look for the tightening of the wind patterns (shown in blue) over the Canada Basin that begins about 13 seconds into the video. Notice how the stream of less salty water from river runoff in Russia (shown in red) begins to loop westward toward Canada in sync with the circulation of the wind rather than continuing toward Greenland as it typically would. The purple arrows show the transpolar drift, a current that generally pushes water toward Greenland. NASA’s Jet Propulsion Laboratory has a press release with more details, and a number of news outlets have written stories about the study. In the image below, the altered path of the freshwater current is shown in red.
Hailstorm and tornado activity increases in the middle of the work week (Tuesday-Thursday) compared to weekends. Weekly cycles in weather behavior are a clear sign of human influence on our climate. The weekly cycle is believed to be caused by the well-known weekly changes in pollution levels with the day of the week. Aerosol pollution decreases the size of water droplets coalescing in clouds. They are lighter and don’t fall out as rain, but instead rise to much higher altitudes where they freeze and release additional heat. This invigorates the storm and produces more ice aloft. This might explain the increase in hailstorms as well as the increase in lightning that has also been observed. It is conjectured by Rosenfeld and Bell, based on numerical model simulations, that storms, amped up by pollution, nevertheless produce weaker cold pools at their base. Tornadoes develop less easily when a cold, rapidly moving pool forms beneath the storm. By weakening cold pool formation, pollution may lead to storms with better chances of forming a tornado than is the case for storms formed in clean air.
Text by Adam Voiland. Video showing lightning storms from the perspective of the International Space Station was posted originally on Johnson Space Center’s Crew Earth Observations Office website. Graphic comparing pollution levels, hail, and tornadoes from Bell’s 2011 JGR paper.
Months later, an analysis conducted by scientists atNASA’s Goddard Space Flight Center including Si-Chee Tsay andSheng-Hsiang Wang showed that over the next ten days following thearrival of the dust, satellite instruments on Aqua and SeaWiFS detecteda marked jumped in phytoplankton abundance (shown by the green circle in the chart above). That’s notable because the nutrient-limited ocean water in the area isn’t known to support much life.
The key ingredient that triggered the bloom, the scientists believe, was iron and phosphorus within the dust particles. Many types of phytoplankton require trace amounts of key nutrients to thrive and blooms can’t easily occur when levels are low, as they are in the northern South China Sea. Satellites have observed dust plumes triggering phytoplankton blooms in the past, but this is the first time the phenomenon has been observed in the South China Sea, an area where heavy dust deposition is relatively infrequent.
To understand how the Antarctic ice sheet is going to behave in the future, scientists first need to know how much snow and ice is in there. And a major step in determining that figure is calculating how much snow accumulates each year on the frozen continent.
Researchers from the Satellite Era Accumulation Traverse (SEAT) are extracting ice cores in central West Antarctica to update snow accumulation records, since the majority of previously collected cores only extend to the mid-1990s. The scientists analyzed three of the five cores collected during their 2010-2011 field campaign, and their preliminary results show that snow accumulation has decreased significantly (up to 40 percent) across central West Antarctica during the last decade.
“This is the opposite of what you’d expect at a time when there’s a significant warming of West Antarctica,” says Landon Burgener, of the SEAT team, who presented the group’s preliminary results at the American Geophysical Union’s Fall Meeting.
Higher temperatures mean higher water evaporation, which in theory should lead to more snowfall. The measured decrease in snow accumulation goes against the predictions of global climate models, so why is it happening? It might have to do with less frequent, weaker storms in the area, says Summer Rupper, one of the principal investigators of the SEAT project. Less storms means that the extra moisture in the atmosphere ends up falling back to Earth somewhere else, probably over the ocean. Next, the team will examine the (scarce) existing weather data for West Antarctica to see if it’s true that the area is becoming less stormy. Rupper also wants to use ground-based radar data to study how representative the cores are of the places where they were extracted.
Meanwhile, other members of the SEAT team are currently in Antarctica to collect eight more cores that they will analyze to see if they also show a decline in snow accumulation.
Text by Maria-José Viñas. Photo and map courtesy of the SEAT team: The photo (top) shows members of the team drilling an ice core during the 2010-2011 season; the map (above) shows the drilling sites in central West Antarctica. Follow the work of the SEAT researchers in Antarctica on their blog, “Notes from the field.”
You’ve most likely seen color-coded, real-time AIRNOW maps of air quality on the web or on television that show whether the air is safe, unhealthy, or hazardous. What you may not realize is that the network of ground-based instruments the EPA uses to make those maps has large gaps in some parts of the country, particularly in sparsely populated areas of the Great Plains and Intermountain West. (Red in the map above indicates areas without ground monitoring stations; black dots show the locations of stations).
To address this problem, an effort sparked by recent advances in satellite measurements of air pollution seeks to integrate NASA and NOAA satellite measurements into the AIRNOW system. The accuracy of satellite measurements of air quality can vary depending on the weather, the topography, the brightness of the underlying surface and other factors, so the researchers leading the effort are developing a method that selectively incorporates only the reliable satellite data. The researchers are still refining the technique and the system isn’t yet operational, but preliminary case studies suggest the technique will be up and running by 2013.
The figure above shows the technique researchers are developing tofuse ground observation and satellite observations of the small particles (PM2.5) that causes health problems. Groundobservations have high uncertainties (shown in the darkest blue) indifferent areas than the satellite observations. The right combinationof the two – see the fused maps at the bottom of the figure – will be more accurate than either the ground network or satellite measurements alone.
Text by Adam Voiland. AdamPasch of Sonoma Technology presented a poster about this topic at theAmerican Geophysical Union fall meeting in San Francisco on Dec. 5, 2011. Video producedby Sonoma Technology. Imagery courtesy of Adam Pasch.
Himalayan glaciers feed rivers and lakes across South Asia that more than a billion people depend upon for fresh water. It’s for this reason – and the fact that many have experienced rapid changes in recent decades – that scientists keep an especially watchful eye on ice in the region.
Much of the data collected to date suggests the prognosis isn’t good. As Goddard Space Flight Center atmospheric scientist William Lau detailed during a presentation at the American Geophysical Union’s fall meeting, air temperatures in the region have been rising at more than 5 times the rate of global warming. And at high elevations in the eastern Himalayas glaciers have been observed retreating by about 1 percent per decade for the last twenty to thirty years. (In contrast, glaciers in the western Himalayas have been relatively stable).
Though greenhouse gases are responsible for part of the warming, Lau’s research finds that two major processes, both associated with airborne particles called aerosols, also play a critical role. The first, a meteorological hypothesis known as the elevated head pump, involves a shift in the monsoon cycle driven by pollution and dust in the region that Lau’s modeling shows brings warmer and wetter conditions to the Himalayan Plateau. The second involves the deposition of dark particles on snow surfaces so that they decrease the albedo and increase temperatures.
The 2011 La Niña, one of the strongest in recent decades, absorbed so much moisture from the oceans and dropped it as precipitation over northern parts of Australia and South America that global mean sea levels fell by about half a centimeter. That was the key point that Eric Lindstrom, an oceanographer based at NASA headquarters, made today while giving a presentation at NASA’s outreach booth at the American Geophysical Union’s fall meeting. He gave the talk with the help of a sophisticated visualization system — called the Hyperwall — that’s capable of displaying large sets of data. The system consists of nine 42-50“ flat-screen monitors arranged in a 3 X 3 array. As Lindstrom pointed out, the fast transition from the 2009-10 El Niño to the 2010-11 La Niña triggered changes in precipitation patterns across the tropics, transferring enough water over land to cause global mean sea level to fall during the spring and summer of 2011. Data from NASA’s GRACE and TRMM satellites have confirmed that the “extra” water and rain has ended up over land as freshwater (see below). The drop in sea level happened despite the background rate of global mean sea level rise, which has been fairly steady at 3.2 millimeters per year since the early 1990s.
What’s happening to Himalayan glaciers, rivers, lakes, and streams has become one of the most important – and widely debated – topics in science.
There’s certainly no shortage of questions. Which of the 15,000 glaciers in the region are retreating and which growing? How many glacial lakes are on the verge of bursting their banks and flooding downstream communities? Will the region’s great rivers, such as the Indus and the Ganges, be able to withstand the region’s changing climate and rapid population growth and continue to sustain the hundreds of millions of people who depend on them? How can devastating floods, such as the one that struck Pakistan last year, be avoided?
Firm answers to such questions have been hard to come by in recent decades because of the limited monitoring resources available in many key countries in the region. Now, however, a new effort, dubbed HIMLA and led by Molly Brown of NASA’s Goddard Space Flight Center, aims to change this by harnessing state-of-the-art, satellite-based monitoring and modeling techniques.
As part of the effort, scientists will feed data from satellite instruments such as MODIS and ASTER into a hydrological model that will produce daily snow/water equivalence maps that will feed into other hydrological models to determine how much freshwater flows into the region’s rivers from snow and glaciers. The ultimate goal: an early warning system that, like the Famine Early Warning System Network does for drought, will help predict floods before they happen.