Category: Climate Change
Published: Thursday, 27 August 2015 12:56
Written by Bernd Riebe
Video: Watching Rising Seas from Space
27 AUG 2015 - NASA's interdisciplinary Sea Level Change Team
Seas around the world have risen an average of nearly 3 inches (8 centimeters) since 1992, with some locations rising more than 9 inches (25 centimeters) due to natural variation, according to the latest satellite measurements from NASA and its partners. An intensive research effort now underway, aided by NASA observations and analysis, points to an unavoidable rise of several feet in the future.
The question scientists are grappling with is how quickly will seas rise?
"Given what we know now about how the ocean expands as it warms and how ice sheets and glaciers are adding water to the seas, it's pretty certain we are locked into at least 3 feet [0.9 meter] of sea level rise, and probably more," said Steve Nerem of the University of Colorado, Boulder, and lead of the Sea Level Change Team. "But we don't know whether it will happen within a century or somewhat longer."
Team scientists will discuss a new visualization based on 23 years of sea level data -- the entire record of available satellite data -- which reveals changes are anything but uniform around the globe. The record is based on data from three consecutive satellite missions; the first a collaboration between NASA and the French space agency, Centre National d'Études Spatiales (CNES), launched in 1992. The fourth in the series will be Jason-3, led by the National Oceanic and Atmospheric Administration (NOAA) with participation by NASA, CNES and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT).
In 2013, the United Nations Intergovernmental Panel on Climate Change issued an assessment based on a consensus of international researchers that stated global sea levels would likely rise from 1 to 3 feet (0.3 to 0.9 meter) by the end of the century. According to Nerem, new research available since this report suggests the higher end of that range is more likely, and the question remains how that range might shift upward.
The data reveal the height of the sea surface is not rising uniformly everywhere. Regional differences in sea level rise are dominated by the effects of ocean currents and natural cycles such as the Pacific Decadal Oscillation. But, as these natural cycles wax and wane, they can have major impacts on local coastlines.
"Sea level along the west coast of the United States has actually fallen over the past 20 years because long-term natural cycles there are hiding the impact of global warming," said Josh Willis, an oceanographer at NASA's Jet Propulsion Laboratory in Pasadena, California. "However, there are signs this pattern is changing. We can expect accelerated rates of sea level rise along this coast over the next decade as the region recovers from its temporary sea level 'deficit.'"
Scientists estimate that about one-third of sea level rise is caused by expansion of warmer ocean water, one-third is due to ice loss from the massive Greenland and Antarctic ice sheets and the remaining third results from melting mountain glaciers. But the fate of the polar ice sheets could change that ratio and produce more rapid increases in the coming decades.
The Greenland ice sheet, covering 660,000 square miles (1.7 million square kilometers) -- nearly the area of Alaska -- shed an average of 303 gigatons of ice a year over the past decade, according to satellite measurements. The Antarctic ice sheet, covering 5.4 million square miles (14 million square kilometers) -- larger than the United States and India combined -- has lost an average of 118 gigatons a year.
"We've seen from the paleoclimate record that sea level rise of as much as 10 feet [3 meters] in a century or two is possible, if the ice sheets fall apart rapidly," said Tom Wagner, the cryosphere program scientist at NASA Headquarters in Washington. "We're seeing evidence that the ice sheets are waking up, but we need to understand them better before we can say we're in a new era of rapid ice loss."
Although Antarctica's contribution to sea level rise currently is much smaller than that of Greenland, recent research indicates this could change in the upcoming century. In 2014, two West Antarctica studies focused on the acceleration of the glaciers in the Amundsen Sea sector showed its collapse is underway.
East Antarctica's massive ice sheet remains the primary unknown in sea level rise projections. Though it appears to be stable, a recent study found under a major glacier two deep troughs that could draw warm ocean water to the base of the glacier, causing it to melt.
"The prevailing view among specialists has been that East Antarctica is stable, but we don't really know," said glaciologist Eric Rignot of the University of California Irvine and JPL. "Some of the signs we see in the satellite data right now are red flags that these glaciers might not be as stable as we once thought. There's always a lot of attention on the changes we see now, but as scientists our priority needs to be on what the changes could be tomorrow."
One of the keys to understanding future rates of ice loss is determining the role ocean currents and ocean temperatures play in melting the ice sheets from below their edges. A new, six-year NASA field campaign took to the waters around Greenland this summer to probe how warming ocean waters are triggering Greenland glacier degradation. The Oceans Melting Greenland (OMG) project is taking coastal ocean temperature measurements, observing glacial thinning at the ice's edge, and producing the first high-resolution maps of the seafloor, fjords and canyons in the continental shelf surrounding Greenland.
NASA uses the vantage point of space to increase our understanding of our home planet, improve lives and safeguard our future. NASA develops new ways to observe and study Earth's interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.
Jet Propulsion Laboratory, Pasadena, Calif.
Category: Climate Change
Published: Saturday, 18 April 2015 10:30
Written by Bernd Riebe (NOAA)
18 April, 2015 - The average temperature across global land and ocean surface temperatures combined for March 2015 was 0.85°C (1.53°F) higher than the 20th century average of 12.7°C (54.9°F). This marks the highest March temperature in the 136-year period of record, surpassing the previous record of 2010 by 0.05°C (0.09°F). The Northern Hemisphere had its second highest March temperature on record, behind only 2008, while the Southern hemisphere tied with 2002 for third highest.
The March 2015 global temperature was the third highest monthly departure from average on record for any month, just 0.01°C (0.02°F) lower than the monthly anomalies for February 1998 and January 2007. This also replaces February 2015 (+0.84°C / +1.51°F) as the third highest departure from average among all months, moving that month to fourth highest. Seven of the past eleven months (May, June, August, September, October, and December 2014, along with March 2015) have tied or set new record high monthly temperatures.
The average March temperature over land surfaces across the globe tied with 1990 as the second highest for March on record, at 1.59°C (2.86°F) above the 20th century average. The warmth was spread fairly evenly across the hemispheres, as the Northern and Southern Hemisphere each observed their third highest March land surface temperatures on record. Most land areas were warmer to much warmer than average, as shown by the Temperature Percentiles map above, with record warmth in parts of the western United States and Canada, various regions in eastern Africa, parts of Scandinavia and northwestern Russia, part of south central China, and an area of northeastern Australia. Central India, southeastern Mauritania, central Mexico, and eastern Canada were cooler than average. Part of northeastern Canada was much cooler than average, with the region observing temperatures at least 3°C (5°F) below average. On the other side of the continent, most of central to western North America had temperatures at least 3°C higher than the 20th century average. Temperatures were also at least 3°C above average across most of Eurasia, with the exception of Far East Russia south of the East Siberian Sea, which was cooler than average.
· Australia observed its eighth warmest March since national records began in 1910, due mainly to heat in the north and east of the country. Queensland was the hotspot, with its warmest maximum (anomalies of +2.88°C / +5.18°F), minimum (+1.62°C / +2.91°F), and mean (+1.89°C / +3.40°F) temperatures compared to the 1961–90 average in the 106-year period of record. Victoria and Tasmania were cooler than average for the month, while South Australia and Western Australia were close to average.
· It was also a warm March in New Zealand thanks to frequent tropical airflow over the country, according to NIWA, with the national temperature for the month 1.0°C (1.8°F) above the 1981–2010 average. Many sites observed temperatures well above average (at least +1.2°C / +2.2°F).
For the oceans, the March global sea surface temperature was 0.55°C (0.99°F) higher than the 20th century average for the month. This marks the third highest globally-averaged March temperature in the 136-year period of record. Only March 1998 and 2010 ocean surface temperatures were warmer, with both months 0.56°C (1.01°F) higher than the 20th century average. Record warm temperatures continued to dominate in the northeast Pacific Ocean and were also notable in the southwest Pacific and parts of the Arctic Seas to the north and northwest of Scandinavia. Overall, every major ocean basin had at least some areas with record warmth and large areas with much warmer-than-average temperatures. Also, continuing a pattern seen since fall 2014, much of the North Atlantic Ocean between Canada and the United Kingdom had much cooler-than-average temperatures during March, with an area of record cold observed within that that region.
El Niño conditions were present during March. Ocean temperatures in the Niño 3.4 region—the area between 5°N and 5°S latitude and 170°W to 120°W longitude where ENSO conditions are monitored—was +0.7°C (+0.11°F) during the last week of March, according to NOAA's Climate Prediction Center (CPC), indicating that a weak-phase El Niño is continuing. According to the CPC, there is about a 70 percent chance that El Niño will continue through Northern Hemisphere summer 2015, and more than 60 percent chance it will last through fall. El Niño conditions tend to enhance global temperatures, with stronger events having generally larger impacts.
NOAA National Climatic Data Center, State of the Climate: Global Analysis for March 2015