Is brekker, og isen som dekker Grønnland og det enorme kontinentet Antarktis forsvinner, glir ned i havet mye fortere enn noen tidligere har innrømmet offentlig.
Den Britiske avisen The Independent har i en serie av artikler nylig satt fokuset på den globale oppvarming, den seneste utviklingen i saken og ikke minst satt fokuset på at enkelte folk for alvor beginner å se sannheten i øynene.
Mange vitenskapsmenn og «amatører» i saken, inkludert meg, har i ti år advart mot det som nå blir klart for alle, at resultaterne presentert av IPCC (Intergovernmental Panel on Climate Change), enda så kontroversielle de var da de ble publisert, var altfor moderate. Nå avslører bevisene seg overalt. Vi ble fortalt at det ville ta minst tusen år før isen forsvant. Jeg har alltid avvist tusenårsmodellen. Den virket altfor strøken, rett og slett, for mye som en dekkoperasjon. Vi ble som vanlig løyet for og ledet vill.
NASA og den amerikanske regjeringen prøvde å kneble Jim Hansen, slik andre har blitt kneblet, på tusen små og store måter.
Les artiklene. Les dem nøye. Les dem igjen og igjen. Og vennligst overbevis deg selv om at dette er sannheten, sannheten og intet annet enn sannheten, fordi det er det det er. Det er ikke den fulle og hele sannheten… siden den er langt verre, men det er det nærmeste den kommende virkeligheten som faktisk har blitt offentliggjort på en slik avslørende måte, en måte så umulig å fornekte.
Hva som engang for veldig lenge siden var åpne grenser er i ferd med å bli det igjen.
Climate change: On the edge
Greenland ice cap breaking up at twice the rate it was five years ago, says scientist Bush tried to gag
By Jim Hansen
Published: 17 February 2006
A satellite study of the Greenland ice cap shows that it is melting far faster than scientists had feared - twice as much ice is going into the sea as it was five years ago. The implications for rising sea levels - and climate change - could be dramatic.
Yet, a few weeks ago, when I - a Nasa climate scientist - tried to talk to the media about these issues following a lecture I had given calling for prompt reductions in the emission of greenhouse gases, the Nasa public affairs team - staffed by political appointees from the Bush administration - tried to stop me doing so. I was not happy with that, and I ignored the restrictions. The first line of Nasa's mission is to understand and protect the planet.
This new satellite data is a remarkable advance. We are seeing for the first time the detailed behaviour of the ice streams that are draining the Greenland ice sheet. They show that Greenland seems to be losing at least 200 cubic kilometres of ice a year. It is different from even two years ago, when people still said the ice sheet was in balance.
Hundreds of cubic kilometres sounds like a lot of ice. But this is just the beginning. Once a sheet starts to disintegrate, it can reach a tipping point beyond which break-up is explosively rapid. The issue is how close we are getting to that tipping point. The summer of 2005 broke all records for melting in Greenland. So we may be on the edge.
Our understanding of what is going on is very new. Today's forecasts of sea-level rise use climate models of the ice sheets that say they can only disintegrate over a thousand years or more. But we can now see that the models are almost worthless. They treat the ice sheets like a single block of ice that will slowly melt. But what is happening is much more dynamic.
Once the ice starts to melt at the surface, it forms lakes that empty down crevasses to the bottom of the ice. You get rivers of water underneath the ice. And the ice slides towards the ocean. Our Nasa scientists have measured this in Greenland. And once these ice streams start moving, their influence stretches right to the interior of the ice sheet. Building an ice sheet takes a long time, because it is limited by snowfall. But destroying it can be explosively rapid.
How fast can this go? Right now, I think our best measure is what happened in the past. We know that, for instance, 14,000 years ago sea levels rose by 20m in 400 years - that is five metres in a century. This was towards the end of the last ice age, so there was more ice around. But, on the other hand, temperatures were not warming as fast as today.
How far can it go? The last time the world was three degrees warmer than today - which is what we expect later this century - sea levels were 25m higher. So that is what we can look forward to if we don't act soon. None of the current climate and ice models predict this. But I prefer the evidence from the Earth's history and my own eyes. I think sea-level rise is going to be the big issue soon, more even than
warming itself.
It's hard to say what the world will be like if this happens. It would be another planet. You could imagine great armadas of icebergs breaking off Greenland and melting as they float south. And, of course, huge areas being flooded.
How long have we got? We have to stabilise emissions of carbon dioxide within a decade, or temperatures will warm by more than one degree. That will be warmer than it has been for half a million years, and many things could become unstoppable. If we are to stop that, we cannot wait for new technologies like capturing emissions from burning coal. We have to act with what we have. This decade, that means focusing on energy efficiency and renewable sources of energy that do not burn carbon. We don't have much time left.
Jim Hansen, the director of the Nasa Goddard Institute for Space Studies in New York, is President George Bush's top climate modeller. He was speaking to Fred Pearce
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Sea levels likely to rise much faster than was predicted
By Steve connor, Science Editor in St Louis
Published: 17 February 2006
Global warming is causing the Greenland ice cap to disintegrate far faster than anyone predicted. A study of the region's massive ice sheet warns that sea levels may - as a consequence - rise more dramatically than expected.
Scientists have found that many of the huge glaciers of Greenland are moving at an accelerating rate - dumping twice as much ice into the sea than five years ago - indicating that the ice sheet is undergoing a potentially catastrophic breakup.
The implications of the research are dramatic given Greenland holds enough ice to raise global sea levels by up to 21ft, a disaster scenario that would result in the flooding of some of the world's major population centres, including all of Britain's city ports.
Satellite measurements of the entire land mass of Greenland show that the speed at which the glaciers are moving to the sea has increased significantly over the past 10 years with some glaciers moving three times faster than in the mid-1990s.
Scientists believe that computer models of how the Greenland ice sheet will react to global warming have seriously underestimated the threat posed by sea levels that could rise far more quickly than envisaged.
The latest study, presented at the American Association for the Advancement of Science, in St Louis, shows that rather than just melting relatively slowly, the ice sheet is showing all the signs of a mechanical break-up as glaciers slip ever faster into the ocean, aided by the "lubricant" of melt water forming at their base.
Eric Rignot, a scientist at the Jet Propulsion Laboratory and the California Institute of Technology in Pasadena, said that computer models used by the UN's International Panel on Climate Change have not adequately taken into account the amount of ice falling into the sea from glacial movements.
Yet the satellite study shows that about two-thirds of the sea-level rise caused by the Greenland ice sheet is due to icebergs breaking off from fast-moving glaciers rather than simply the result of water running off from melting ice.
"In simple terms, the ice sheet is breaking up rather than melting. It's not a surprise in itself but it is a surprise to see the magnitude of the changes. These big glaciers seem to be accelerating, they seem to be going faster and faster to the sea," Dr Rignot said.
"This is not predicted by the current computer models. The fact is the glaciers of Greenland are evolving faster than we thought and the models have to be adjusted to catch up with these observations," he said.
The Greenland ice sheet covers an area of 1.7 million sq km - about the size of Mexico - and, in places, is up to 3km thick. It formed over thousands of years by the gradual accumulation of ice and snow but now its disintegration could occur in decades or centuries.
Over the past 20 years, the air temperature of Greenland has risen by 3C and computer models suggested it would take at least 1,000 years for the ice sheet to melt completely. But the latest study suggests that glaciers moving at an accelerating rate could bring about a much faster change.
"The behaviour of the glaciers that dump ice into the sea is the most important aspect of understanding how an ice sheet will evolve in a changing climate," Dr Rignot said. "It takes a long time to build and melt an ice sheet but glaciers can react quickly to temperature changes. Climate warming can work in different ways but, generally speaking, if you warm up the ice sheet, the glacier will flow faster," he said.
The ice "balance sheet" of Greenland is complex but - in simple terms - it depends on the amount of snow that falls, the amount of ice that melts as run-off and the amount of ice that falls directly into the sea in the form of icebergs "calving" from moving glaciers.
Satellites show that the glaciers in the south of Greenland are now moving much faster than they were 10 years ago. Scientists estimate that, in 1996, glaciers deposited about 50 cubic km of ice into the sea. In 2005 it had risen to 150 cubic km of ice.
Details of the latest study, published in the journal Science, show that Greenland now accounts for an increase in global sea levels of about 0.5 millimetres per year - compared to a total sea level rise of 3mm per year.
When previous studies of the ice balance are taken into account, the researchers calculated that the overall amount of ice dumped into the sea increased from 90 cubic km in 1996 to 224 cubic km in 2005.
Dr Rignot said that there are now signs that the more northerly glaciers of Greenland are beginning to adopt the pattern of movements seen by those in the south. "The southern half of Greenland is reacting to what we think is climate warming. The northern half is waiting, but I don't think it's going to take long," he said.
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Global warming '30 times quicker than it used to be'
By Steve Connor
Published: 17 February 2006
Greenhouse gases are being released into the atmosphere 30 times faster than the time when the Earth experienced a previous episode of global warming.
A study comparing the rate at which carbon dioxide and methane are being emitted now, compared to 55 million years ago when global warming also occurred, has found dramatic differences in the speed of release.
James Zachos, professor of earth sciences at the University of California, Santa Cruz, said the speed of the present build-up of greenhouse gases is far greater than during the global warming after the demise of the dinosaurs.
"The emissions that caused this past episode of global warming probably lasted 10,000 years," Professor Zachos told the American Association for the Advancement of Science at a meeting in St Louis. "By burning fossil fuels, we are likely to emit the same amount over the next three centuries."
He warned that studies of global warming events in the geological past indicate the Earth's climate passes a threshold beyond which climate change accelerates with the help of positive feedbacks - vicious circles of warming.
Professor Zachos is a leading authority on the episode of global warming known as the palaeocene-eocene thermal maximum, when average global temperatures increased by up to 5C due to a massive release of carbon dioxide and methane.
His research into the deep ocean sediments suggests at this time about 4.5 billion tons of carbon entered the atmosphere over 10,000 years. This will be the similar amount of carbon released into the atmosphere from cars and industrial emissions over the next 300 years if present trends continue, he said.
Although carbon can be released suddenly and naturally into the atmosphere from volcanic activity, it takes many thousand of years for it to be removed permanently by natural processes. The ocean is capable of removing carbon, and quickly, but this natural capacity can be quickly overwhelmed, which is probably what happened 55 million years ago.
"It will take tens of thousands of years before atmospheric carbon dioxide comes down to pre-industrial levels," the professor said. "Even after humans stop burning fossil fuels, the effects will be long-lasting."
Det er vel en kjent sak i isbre-norge at breer som smelter trekker seg tilbake.
SvarSlettMens grønlandske breene kalver mere fordi brefarten mot kysten blir større pga tykkere iskappen er blitt tykkere den siste tiden. At innlandsisen vokser er vel ingen indikasjon om global oppvarming.
vh Joachim
Leste du det som stod der??? Det virker slett ikke slik.
SvarSlett