Our grandchildren will know no Arctic.
Arctic sea ice shrinks to third lowest area on record
Arctic sea ice melted over the summer to cover the third smallest area on record, US researchers said Wednesday, warning global warming could leave the region ice free in the month of September 2030.
Last week, at the end of the spring and summer “melt season” in the Arctic, sea ice covered 4.76 million square kilometers (1.84 million square miles), the University of Colorado’s National Snow and Ice Data Center said in an annual report.
“This is only the third time in the satellite record that ice extent has fallen below five million square kilometers (1.93 million square miles), and all those occurrences have been within the past four years,” the report said.
A separate report by the National Oceanic and Atmospheric Administration (NOAA) found that in August, too, Arctic sea ice coverage was down sharply, covering an average of six million square kilometers (2.3 million square miles), or 22 percent below the average extent from 1979 to 2000.
The August coverage was the second lowest for Arctic sea ice since records began in 1979. Only 2007 saw a smaller area of the northern sea covered in ice in August, NOAA said.
The record low for Arctic sea ice cover at the end of the spring and summer “melt season” in September, was also in 2007, when ice covered just 4.13 million square kilometers (1.595 million square miles).
- What does the 2010 Arctic Sea ice minimum extent signify? (greenanswers.com)
- Arctic sea ice reaches lowest 2010 extent, third lowest in satellite record (eurekalert.org)
By Steve Connor, Science Editor. The sun’s role in climate change may have been overplayed, according to a study indicating that the Earth could actually get slightly cooler, rather than warmer, as the activity of the 11-year solar cycle increases.
Until now it was assumed that as solar activity – indicated by the number of sunspots on the Sun’s surface – increases, then so does the amount of solar radiation coming to the Earth to heat the planet.
However, a study based on satellite data of the Earth’s atmosphere has shown there is a complicated interaction between the varying amounts of radiation from the Sun and the amount of ozone in the atmosphere.
“Evapotranspiration” returns about 60 percent of annual precipitation back to the atmosphere, in the process using more than half of the solar energy absorbed by land surfaces. This is a key component of the global climate system, linking the cycling of water with energy and carbon cycles.
The soils in large areas of the Southern Hemisphere, including major portions of Australia, Africa and South America, have been drying up in the past decade, a group of researchers conclude in the first major study to ever examine on a global basis.
Most climate models have suggested that evapotranspiration, which is the movement of water from the land to the atmosphere, would increase with global warming. The new research found that’s exactly what was happening from 1982 to the late 1990s. Some of the areas with the most severe drying include southeast Africa, much of Australia, central India, large parts of South America, and some of Indonesia. Most of these regions are historically dry, but some are actually tropical rain forests.
In 1998, this significant increase in evapotranspiration — which had been seven millimeters per year — slowed dramatically or stopped. In large portions of the world, soils are now becoming drier than they used to be, releasing less water and offsetting some moisture increases elsewhere.
Due to the limited number of decades for which data are available, scientists say they can’t be sure whether this is a natural variability or part of a longer-lasting global change. But one possibility is that on a global level, a limit to the acceleration of the hydrological cycle on land has already been reached.
If it’s long-term, it could result in reduced terrestrial vegetation growth, less carbon absorption, a loss of the natural cooling mechanism provided by evapotranspiration, more heating of the land surface, more intense heat waves and a “feedback loop” that could intensify global warming.
“This is the first time we’ve ever been able to compile observations such as this for a global analysis,” said Beverly Law, a professor of global change forest science at Oregon State University. Law is co-author of the study and science director of the AmeriFlux network of 100 research sites, which is one major part of the FLUXNET synthesis that incorporates data from around the world.”We didn’t expect to see this shift in evapotranspiration over such a large area of the Southern Hemisphere,” Law said. “It is critical to continue such long-term observations, because until we monitor this for a longer period of time, we can’t be sure why this is occurring.”
The rather abrupt change from increased global evapotranspiration to a near halt in this process coincided with a major El Nino event in 1998, the researchers note in their report, but they are not suggesting that is a causative mechanism for a phenomenon that has been going on for more than a decade now.
Greater evapotranspiration was expected with global warming, because of increased evaporation of water from the ocean and more precipitation overall. And data indeed show that some areas are wetter than they used to be.
However, other huge areas are now drying out, the study showed. This could lead to increased drought stress on vegetation and less overall productivity, Law said, and as a result less carbon absorbed, less cooling through evapotranspiration, and more frequent or extreme heat waves.
Longer term observations will be needed to determine if these changes are part of decadal-scale variability or a longer-term shift in global climate, the researchers said.
This study was authored by a large group of international scientists, including from OSU; lead author Martin Jung from the Max Planck Institute for Biogeochemistry in Germany; and researchers from the Institute for Atmospheric and Climate Science in Switzerland, Princeton University, the National Center for Atmospheric Research in Colorado, Harvard University, and other groups and agencies.