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"Warning" about
Global Warming

Science Mysteries

Scientists predict that if global warming continues, the world's major ice shelves will melt by 2100, causing oceans to rise by 7m to 14m, devastating coastal areas worldwide.

Global Warming Predictions - Main Menu

1. Science Predictions about Global Warming

Most scientists today agree that the Earth is heating up, due primarily to an atmospheric increase in carbon dioxide caused mainly by the burning of fossil fuels such as coal and petroleum. 2005 was the hottest year on Earth since the late 19th century, when scientists began collecting temperature data. The past decade featured five of the warmest years ever recorded, with the second hottest year being 1998.

Image:Instrumental Temperature Record.png
Global mean surface temperatures 1850 to 2006
Source: Wikipedia

The image above shows the instrumental record of global average temperatures as compiled by the Climatic Research Unit of the University of East Anglia and the Hadley Centre of the UK Meteorological Office. The GNU Free Documentation License Version 1.2; with no Invariant Sections, Front-Cover Texts, or Back-Cover Texts.

Mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980

Mean surface temperature anomalies during the period 1995 to 2004
with respect to the average temperatures from 1940 to 1980
Source: Wikipedia

The geographic distribution of surface warming during the 21st century calculated by the HadCM3 climate model if a business as usual scenario is assumed for economic growth and greenhouse gas emissions. In this figure, the globally averaged warming corresponds to 3.0 °C (5.4 °F)

The geographic distribution of surface warming during the 21st century
calculated by the HadCM3 climate model if a business as usual scenario
 is assumed for economic growth and greenhouse gas emissions.
In this figure, the globally averaged warming corresponds to 3.0 °C (5.4 °F)
Source: http://en.wikipedia.org/wiki/Global_Warming#Biomass_production

Arctic Sea Ice Coverage - Flash Animation:
 http://www.theglobeandmail.com/v5/content/features/ClimateChange/receding_arctic.html

 

Arctic Meltdown

Global sea levels could rise by more than 20 feet (6 meters) with the loss of shelf ice in Greenland and Antarctica, devastating coastal areas worldwide.

There is little doubt that sea levels would rise by that much if Greenland melted. But scientists disagree on when it could happen.

A recent Nature study suggested that Greenland's ice sheet will begin to melt if the temperature there rises by 3ºC (5.4ºF) within the next hundred years, which is quite possible, according to leading temperature-change estimates.

Many experts agree that even a partial melting would cause a one-meter (three-foot) rise in sea levels, which would entirely submerge low-lying island countries, such as the Indian Ocean's Maldives.

The Arctic Ocean could be ice-free in summer by 2050.

Some climate models are more conservative, suggesting that there will be no summer ice in the Arctic by the year 2100. But new research shows it could take as little as 20 years for the sea ice to disappear.

"Since the advent of remote satellite imaging, we've lost about 20 percent of sea-ice cover. We think of the Arctic as the heat sink to the climate system. We're fundamentally changing this heat sink, and we don't know how the rest of the climate system is going to respond."   --  Mark Serreze, a research scientist at the National Snow and Ice Data Center in Boulder, Colorado.

Sources:

 

Arctic meltdown just decades away, scientists warn

By David Adam in London
September 30, 2005

Global warming in the Arctic might be accelerating out of control, scientists have warned, as new data revealed the floating cap of sea ice has shrunk to probably its smallest in at least a century.


This satellite im shows the Arctic sea ice spread on September 21, 2005, when it dropped to
the lowest extent yet recorded. The yellow outline indicates where the concentration of ice
was as of September 21, 1979. Photo: AFP

Experts at the US National Snow and Ice Data Centre in Colorado fear the region is locked into a destructive cycle, with warmer air melting more ice, which in turn warms the air further. Satellite pictures show that the extent of Arctic sea ice this month dipped 20 per cent below the long-term average for September - melting an extra 1.3 million square kilometres - an area about the size of the Northern Territory. If current trends continue, the summertime Arctic Ocean will be ice-free well before the end of this century.

The head scientist at the Colorado centre, Ted Scambos, said melting sea ice accelerates warming because dark-coloured water absorbs heat from the sun that was previously reflected back into space by white ice.

"Feedbacks in the system are starting to take hold. We could see changes in Arctic ice happening much sooner than we thought and that is important because without the ice cover over the Arctic Ocean we have to expect big changes in Earth's weather," Dr Scambos said.

The findings are consistent with recent computer simulations showing that a build-up of greenhouse gases could lead to a profoundly transformed Arctic later this century. The North Pole ice cap always grows in winter and shrinks in the summer. The average minimum area from 1979, when precise satellite mapping began, until 2000 was 11 million square kilometers. The new summer low, measured 11 days ago, was 20 per cent below that.

This is the fourth consecutive year that melting has been greater than average, and it pushed the overall decline in sea ice per decade to 8 per cent, up from 6.5 per cent in 2001.

Walt Meier, also at the Colorado centre, said: "Having four years in a row with such low ice extents has never been seen before in the satellite record. It clearly indicates a downward trend, not just a short-term anomaly."

Surface air temperatures over most of the Arctic Ocean often have been 2-3 degrees higher this year than from 1955 to 2004.

The notorious north-west passage through the Canadian Arctic from Europe to Asia was completely open this summer, except for a 95-kilometre swathe of scattered ice floes. The north-east passage, north of the Siberian coast, has been ice-free since August 15.

Springtime melting in the Arctic has begun much earlier in recent years. This year it started 17 days earlier than expected. The winter rebound of ice, where sea water refreezes, has also been affected. Last winter's recovery was the smallest on record and the peak Arctic ice cover failed to match the previous year's level.

The decline threatens wildlife in the region, especially polar bears. It is also the latest in a series of discoveries that have raised the spectre of environmental tipping points: critical thresholds beyond which the climate would be unable to recover.

Source: The Guardian, The New York Times

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