NASA Study Shows Thinning Arctic Sea Ice

"We're heading towards an Arctic that won't have any summer sea ice in 20-30 years -- the most recent research indicates that the last time that happened was at least 5,500 years ago."

What caused this to happen 5,500 years ago?

What caused this to happen 5,500 years ago?
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It was all the coal fired power plants we had 5,500 years ago.

Below I quote Walt Meier, sea ice researcher at the National Snow and Ice Data Center, in response to the above two comments. - Laurie J. Schmidt

First, we don't know for sure exactly when the Arctic was sea ice-free during the summer. I was citing a recent paper that showed evidence that it had been at least 5500 years ago, but it may have been longer and it is also possible, though not likely based on the research, that it was more recently than 5500 years ago.

Obviously, changes in climate before the last century were not significantly caused by humans. There are always natural factors that occur, whether it be the strength of the sun, the orbit of the earth, or other non-human factors. Those factors are still occurring today. However, the key thing is that those factors are not sufficient to explain the changes that have been seen over the past 30 years. We do have an a very clear explanation for why those changes are occurring now - human emissions of greenhouse gases.

Just because in the past you've always gotten sick because of a flu bug, doesn't mean that this time you can rule out food poisoning as the cause.

I guess we're making progress. Last year at this time we were worried that the Arctic would be ice free by the end of the summer and it did not happen. Is thin ice better than no ice?

And, what's the big deal if the Arctic is ice free? Melting sea ice won't raise sea levels. If terrestrial ice melts into the ocean, then you might have something worth worrying about but current computer models overestimate terrestrial melting and undercount interior ice mass gain in Greenland.

Plus, the Antarctic ice mass is getting larger to boot. Of course, I wouldn't be surprised if it turns out that the Arctic was ice free as little as 500+ years ago during the Medieval Warm Period. After all, explorers then were looking for the Northwest Passage.

Nice try, PopSci.

i agree with laughingboy we in north America tend only to look at what is happening around us. although in fact the earth is very balanced as to temprature changes where the arctic is warming up the antarctic is cooling down this should in no way take us by suprise when we look at how the north pole has moved and how the earth is no longer in the same rotation as it was 20 years ago.

Laurie,

Thanks for the update!

There's a few reasons to be concerned with melting Artic sea ice:
1) If you like taking your kids to the zoo and seeing real live polar bears, you need to have sea ice for them to hunt seals on. It's not possible to keep enough polar bears in zoos to keep them from getting inbred, so a large healthy natural population is necessary. Maybe you don't care, and an animated polar bear selling soda on TV is good enough for you.

2) Ice is white. It reflects heat, while dark seawater absorbs it. So it makes a lovely little feedback loop which could make things warmer than they're already getting. Yes, it may have been that warm 5,500 years ago, but our civilization has changed since then. I don't think anybody disagrees that tornadoes and hurricanes get their energy from the atmosphere, and the more energy in that atmosphere, the worse these storms get. A few more tornadoes in the Midwest wouldn't have affected the Indians much 5,000 years ago; now people will die because we have towns everywhere. Likewise, you only see hurricanes in the summer, because they need heat. Most of our population lives near the coast, making us more vulnerable than our ancestors who lived 5,000 years ago. Maybe hurricanes and tornadoes were worse in the past due to natural causes, but that doesn't mean we shouldn't care that we're going back in that direction.

Can we change it? Maybe. Is it natural? I don't have enough education to say. But don't say it doesn't matter.

Oh, might wanna check this out. It seems to fly directly in the face of this article.

http://wattsupwiththat.com/2009/04/09/wuwt-ice-survey-shows-thickening-arctic-ice/

hey Eparker!
If lack of ice would kill out the polar bears then i think they would have died out 5500 years ago..and again a few thousand years before that.. and before that.... Besides even if they die out, they'll just join the 99.99% of other species of the planet. Im actually more saddened that i cant take my kids to see a saber tooth tiger, or the wooly mamoth :) -guess those pictures of a polar bear floating on a loan piece of ice in the ocean got to u lol.

Im so sick of how everyone is worried about changing climate killing people... HURRICANES???? more people die from air pollution in big cities than any hurricane could ever do. But everyone has forgotten about the REAL poisons we put into the air.. things like carbon Monoxide.

Also how much good do you hyper-environmentalists think your doing using those CFL lightbulbs when most people through those little mercury bombs into the trash anyways. its ridiculous.

EParker:

Your assertion that the weather is driven by the atmosphere is not exactly correct. Nearly all atmospheric activity is ultimately driven by the sun, with some input from geologic events like volcanic eruptions. If your theory about storms being more intense due to warming is correct, then the record of the last couple of years does not really help your case. We've had fewer hurricanes than predicted.

Using weather patterns like this is probably not a good idea. We really don't have enough data to work with. Katrina may sound like a really bad storm, but the hurricane that hit Galveston in the early 1900's killed ~6-8 thousand people. Was it caused by increased CO2? Not likely.

You might also want to consider other effects of moderate warming, such as cloud formation. If there's more water in the atmosphere (which is a primary tenet of GW theory and the so-called "vicious cycle"), then isn't it likely that more cloud formation is likely? While these may have localized warming affect at night, they have a net cooling affect on the planet by reflecting sunlight back into space.

This is a complex effect, and as you rightly note, we don't have the information to make the assertions that some in the scientific community are making. It should also be noted that "consensus" has not been reached and good science allows for critical analysis of theories.

No one in this thread stated that "it doesn't matter". But there are a significant number of people, in fact a majority of the US population, who are not convinced that climate change is man-made. What does matter to all of these people is their bottom line. If warming is not significantly man-made, then it makes no sense to alter lifestyles and our standard of living to accommodate someone's political agenda.

Yes, actually someone in this thread did state that it doesn't matter. laughingboy said:

"And, what's the big deal if the Arctic is ice free?"

Polar bears are capable of living on land. They are capable predetors in any snowy environment. If the ice is gone, more will starve during summer, but all will not. Those seals have to land somewhere to balf, and the shores only changes the dynamic of their lifestyles. They are more than capable of adaptation.

Interbreeding with Grizzlies is a risk, but interspecies barriers exist throughout the animal kingdom where crossable species mix.

Also, an abundance of first/second year ice is EXACTLY what you exspect after a few years of record melt. That is how ice recovers. One. Year. At. A. Time. If the melt is down this year, then next year the ice is older. Etc. Etc. Etc.

Ms. Schmidt is correct. I asked what's the big deal. Polar bears survived previous times the Arctic was ice free and they'll probably survive now. As for eparker's observations of ice reflecting sunlight and seawater absorbing it, again, the overall effect on the atmosphere is up in the air.

Climate models make all sorts of assumptions on the feedback loop of all sorts of things to make predictions. Sadly, they've turned out comically wrong.

Ironically, there was an article out today suggesting the Arctic melting was not caused by CO2 but by pollution controls:

http://www.theregister.co.uk/2009/04/09/arctic_aerosols_goddard_institute/

I'm a bit dubious but it's still funny.