David_42
Registered Democrat.
- Aug 9, 2015
- 3,616
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NASA has a wonderful website about climate change, and to be honest, I'll trust NASA and the overwhelming majority of scientists then some deniers on an internet forum.
NASA: Climate Change and Global Warming
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http://climate.nasa.gov/vital-signs/sea-level/
Much more to add...
NASA: Climate Change and Global Warming
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http://climate.nasa.gov/vital-signs/sea-level/
http://climate.nasa.gov/vital-signs/global-temperature/Sea level rise is caused primarily by two factors related to global warming: the added water from melting land ice and the expansion of sea water as it warms. The first chart tracks the change in sea level since 1993 as observed by satellites.
The second chart, derived from coastal tide gauge data, shows how much sea level changed from about 1870 to 2000.
http://climate.nasa.gov/news/937/This graph illustrates the change in global surface temperature relative to 1951-1980 average temperatures. The 10 warmest years in the 134-year record all have occurred since 2000, with the exception of 1998. The year 2014 ranks as the warmest on record. (Source: NASA/GISS). This research is broadly consistent with similar constructions prepared by the Climatic Research Unit and the National Oceanic and Atmospheric Administration.
The time series below shows the five-year average variation of global surface temperatures from 1884 to 2014. Dark blue indicates areas cooler than average. Dark red indicates areas warmer than average.
Climate Change: Vital Signs of the Planet: Land IceOcean waters melting the undersides of Antarctic ice shelves are responsible for most of the continent's ice shelf mass loss, a new study by NASA and university researchers has found.
Scientists have studied the rates of basal melt, or the melting of the ice shelves from underneath, of individual ice shelves, the floating extensions of glaciers that empty into the sea. But this is the first comprehensive survey of all Antarctic ice shelves. The study found basal melt accounted for 55 percent of all Antarctic ice shelf mass loss from 2003 to 2008, an amount much higher than previously thought.
Antarctica holds about 60 percent of the planet's fresh water locked into its massive ice sheet. Ice shelves buttress the glaciers behind them, modulating the speed at which these rivers of ice flow into the ocean. Determining how ice shelves melt will help scientists improve projections of how the Antarctic ice sheet will respond to a warming ocean and contribute to sea level rise. It also will improve global models of ocean circulation by providing a better estimate of the amount of fresh water ice shelf melting adds to Antarctic coastal waters.
The study uses reconstructions of ice accumulation, satellite and aircraft readings of ice thickness, and changes in elevation and ice velocity to determine how fast ice shelves melt and compare the mass lost with the amount released by the calving, or splitting, of icebergs.
"The traditional view on Antarctic mass loss is it is almost entirely controlled by iceberg calving," said Eric Rignot of NASA's Jet Propulsion Laboratory in Pasadena, Calif., and the University of California, Irvine. Rignot is lead author of the study to be published in the June 14 issue of the journal Science. "Our study shows melting from below by the ocean waters is larger, and this should change our perspective on the evolution of the ice sheet in a warming climate."
Ice shelves grow through a combination of land ice flowing to the sea and snow accumulating on their surface. To determine how much ice and snowfall enters a specific ice shelf and how much makes it to an iceberg, where it may split off, the research team used a regional climate model for snow accumulation and combined the results with ice velocity data from satellites, ice shelf thickness measurements from NASA's Operation IceBridge -- a continuing aerial survey of Earth's poles -- and a new map of Antarctica's bedrock. Using this information, Rignot and colleagues were able to deduce whether the ice shelf was losing mass through basal melting or gaining it through the basal freezing of seawater.
In some places, basal melt exceeds iceberg calving. In other places, the opposite is true. But in total, Antarctic ice shelves lost 2,921 trillion pounds (1,325 trillion kilograms) of ice per year in2003 to 2008 through basal melt, while iceberg formation accounted for 2,400 trillion pounds(1,089 trillion kilograms) of mass loss each year.
Climate Change: Vital Signs of the Planet: Arctic Sea Ice MinimumData from NASA's Grace satellites show that the land ice sheets in both Antarctica and Greenland are losing mass. The continent of Antarctica has been losing about 134 billion metric tons of ice per year since 2002, while the Greenland ice sheet has been losing an estimated 287 billion metric tons per year.
Global Ice Viewer - Very interesting.Arctic sea ice reaches its minimum each September. September Arctic sea ice is now declining at a rate of 13.3 percent per decade, relative to the 1981 to 2010 average. This graph shows the average monthly Arctic sea ice extent in September since 1979, derived from satellite observations.
The animated time series below shows the annual Arctic sea ice minimum since 1979, based on satellite observations. The 2012 sea ice extent is the lowest in the satellite record.
Much more to add...