Seas rise — vast amounts of ice melt for every 1 mm gain

July 24, 2009

It takes the equivalent of a massive chunk of ice of 390 cubic kms (150 cubic miles) to raise world sea levels by one millimetre, according to David Carlson, director of the International Programme Office of the International Polar Year.

As an example, he says that works out as a lump 39 kms long, 10 wide and 1 km thick. Or I reckon it could be a blockbuster ice cube with sides 7.3 kms long — that would smother most of  a large city such as Paris (top left — you can see the Eiffel Tower in the middle).

David’s numbers give an idea of the scale of the thaw under way — seas have been rising at about 3 millimetres a year in recent years in a trend that almost all climate scientists blame on global warming caused by human activities. That’s equivalent to a rate of 30 cms a century.

And it’s also a lot faster than a rise of 1.8 mm a year from the 1960s, according to the U.N. Climate Panel. The thaw is one of the spurs to action under plans for a new U.N. treaty to fight global warming due to be agreed in Copenhagen in December.

Some scientists reckon seas could rise by one metre this century. Most of the rise projected by 2100, however, is likely because water expands as it gets warmer, rather than because of a thaw of glaciers or of ice sheets smothering Greenland or Antarctica.

One bit of good news on the ice front is that it looks as if sea ice in the Arctic will not shrink to a new record low this summer, after 2007 marked the smallest since satellite records began in the 1970s (and probably a lot longer than that).

Ice shrinks to its annual low in September before freezing out again: so far the ice is still far bigger than in 2007 at the same time although it is also far smaller than the 1979-2000 average, according to the U.S. National Snow and Ice Data Center. And ice floating on the sea doesn’t really contribute to raising sea levels — it’s effectively part of the water already.

(Picture: undated satellite image of the Eiffel Tower and the surrounding area in Paris, France. REUTERS/DigitalGlobe TZ)

9 comments

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Smother? Really? 1 mm will “smother” Paris? I doubt it. I mm wouldn’t even go over the banks to put a little wet slick on the roads. The 30 mms that *might* happen in a century = 1.181 inches, that wouldn’t even rise above the banks of the Seine.

Really. The objective reality, based on your own reporting here, is hardly worth getting in a dither about.

Posted by drrebel | Report as abusive

correcting my own…30 *cms* a century is 11.81 inches (I missed the decimal point) which is less than one foot. Don’t know the height of the edges of the Seine, but still would hardly “smother” it. Plus, in a century, human beings (if we can ever get around to using these big brains we like to brag about) should be able to figure out a workaround. That might make the streets of Miami a little wet and they might lose some of their beaches. But even most beaches of the world have more than a 3 foot elevation so we might lose some beaches, but hardly enough to move everything inland. And what’s up with the diff between those who say 30 cms a century and 1 meter a century? That’s a 3x diff!! Makes me wonder who’s using what sources for their data.

Posted by drr | Report as abusive

“DrRebel” misunderstood the original article, which said that the 7.3 km cube of ice would smother most of central Paris, not that the resulting melt water would raise the ocean level enough to inundate the city.

The rest of “drrebel”‘s comment appears to make no sense.

Posted by Michael Youngblood | Report as abusive

Michael,

Some people read without comprehending.

Posted by Gerald Jones | Report as abusive

Measuring sea level is almost impossible at the millimeter scale. The Earth’s crust is actually rising due to the subsidence of the last Ice Age over 20,000 years ago. This produces FALLING sea levels in many places, such as Stockholm where the fall is over 5 mm/year. All credible experts agree that a minimum of 50 years of accurate data would be required to establish any change, and there is no such data.

Let’s worry about this when there is some proof, of any human-induced climate change at all. The satellite ice records date back to 1978. How much was there before that? Well, the Northwest Passage opened in 1905, which is how Amundsen reached the North Pole. Anecdotal data is no data…

Posted by Michael Moon | Report as abusive

Sea level is measured by globally averaging data from many places and times. Looking only at where the crust is rebounding just measures your preconceptions. In 9 years, when we have 50 years of satellite data, will the reader consider it?

Human induced climate change is accept by 90% of scientists in the field. Even George Bush now believes it.

Amundsen went to the North Pole in 1926 by air, not in 1903-1906 by boat. The Northwest Passage, open or closed, does not go to the pole.

You might want to correct the statement that “human induced climate change is accept(ed) by 90% of scientists in the field. It’s nowhere close to that. And, among others in the engineering and scientific community who understand the complex system of processes that affect our climate, it’s even less. And, there are new studies in technical publications every week that either cast uncertainty on the “settled science” or disprove it completely. There is no such thing as settled science.

Posted by Troy Shackelford | Report as abusive

You’re just dead wrong about “most beaches of the world have more than a 3 foot elevation”. The vast majority of humans on the planet live in low-lying areas of less than a meter.

Educate yourself and stop spreading disinformation:
http://www.cfa.harvard.edu/space_geodesy  /SEALEVEL/

Sea level predictions vary because:

1) there are multiple factors that will have varying impacts. If Greenland’s ice sheets melt, that is one impact. If Western Antarctica melts, that another. If BOTH Greenland and the Western Antarctica sheets melt completely, we’re talking a 23 foot rise. That would bother even you, I’ll wager.

2) The variations you see might also be due to the fact that current estimates of sea level rise are often calculated under varying scenarios — if we take big or small actions now, versus later, versus doing nothing at all. Those different scenarios are not always clearly defined in new stories.

Posted by Methuselah | Report as abusive

Why do you continue to refer to the term “Global Warming” when NASA and several CREDIBLE scientists have proven the earth has cooled each of at least the last nine years? This is irresponsible journalism at best and outright bias in reporting at worst. Mother Earth worshipers have changed the term to “Climate Change” because they can no longer call it “Global Warming”. But isn’t that just another word for “weather”? Oh, how the politically correct have taken over. Also, it is VERY clear science that even grade schoolers know, that melting ice does not increase water levels. Do the simple science experiment yourself with a glass or bowl of water and some ice cubes. Also, where is the mention that the ice in antartica is actually INCREASING? The only things the scientists have to “predict” the future are overly complex computer models. Who says these models are right? Them? Who funds them? The government? Al Gore? The end result is that those same models FAILED to predict the Global COOLING that has happened in the past few years. That tells me the models and flawed and therefore, the whole argument is questionable. 90% of the scientists? NO! This also is a misstatement and no fact.

Posted by John | Report as abusive