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Robert Tulip
2015-Sep-04, 01:43 AM
When CO2 was last at 400 ppm, what was the sea level?

Spacedude
2015-Sep-04, 01:24 PM
For what it's worth I found this :

"When CO2 was over 400 ppm last, in the Pliocene….sea level was 20 metres higher. "

See: http://rockyrexscience.blogspot.co.uk/2015/07/climate-change-pliocene-rebooted.html … #geology #science #oceans

Jens
2015-Sep-04, 02:04 PM
I'm not an expert at all but from what I've seen it seems that 400 ppm is still quite a low level when looking at past data. It seems there were times when it was 2000 ppm.

Robert Tulip
2015-Sep-05, 12:25 AM
I was searching on google and could not find a simple answer. But the discipline of forming a concise question for BAUT, and then putting that into google led me to a similar site to the one spacedude mentions

At http://scienceblogs.com/significantfigures/index.php/2013/05/10/the-last-time-atmospheric-co2-was-at-400-parts-per-million-humans-didnt-exist/


The last time atmospheric CO2 was at 400 parts per million was during the ancient Pliocene Era, three to five million years ago, and humans didn’t exist.

Global average temperatures were 3 to 4 degrees C warmer than today (5.4 to 7.2 degrees F).
Polar temperatures were as much as 10 degrees C warmer than today (18 degrees F).
The Arctic was ice free.
Sea level was between five and 40 meters higher (16 to 130 feet) than today.
Coral reefs suffered mass die-offs.

Jens is right, but I think those much higher levels were at a time when there was little free oxygen and no ice.

This looks to be a usefully informative graph of sea level, temperature and CO2 over earth history, especially with the logarithmic scale on the x axis. (http://www.biocab.org/Geological_TS_SL_and_CO2.jpg)

speach
2015-Sep-05, 11:45 PM
http://co2now.org/

Robert Tulip
2015-Sep-06, 02:01 AM
http://co2now.org/

Thanks speach, I looked at that site and did not find anything on my question. Perhaps you can help me out with a direct link. I will look at its science papers mentioning the Pliocene (http://co2now.org/Know-the-Changing-Climate/Climate-Science/climate-science-news-and-updates.html), although these date from 2009.

It gives Vostok ice core data back to 800,000 years, but the CO2 range in its oldest linked data set (ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/epica_domec/edc-co2-2008.xls) is only 171-260 ppm, about half the current level.

The link (http://scienceblogs.com/significantfigures/index.php/2013/05/10/the-last-time-atmospheric-co2-was-at-400-parts-per-million-humans-didnt-exist/) I gave explains that the timing for the last 400 ppm level is about five times longer than the ice core records at that Antarctic site. Any papers providing more detail on this specific question would be appreciated.

BigDon
2015-Sep-10, 08:45 PM
Most of you posters know this already but I run into a whole lot of people who don't.

A lot of people think that a rise in sea level describes how far up the beach the water is going to come.

They are seeing it as a horizontal spread of the oceans instead of a vertical rise in sea level.

And that is not correct. As a rule of thumb for every quarter of an inch rise in sea level you lose ten feet of beach. A vertical rise of 20 meters, 787.4 inches, means an encroachment of 6 miles around all the continents.

Would wide that's a substantial amount of inundation.

Would that be enough to open the North American Inner Seaway again?

NEOWatcher
2015-Sep-10, 10:05 PM
Would that be enough to open the North American Inner Seaway again?
I'm no expert, but I would say no.
Since the seaway existed, plate tectonics raised the entire central part of North America. The great plains are thousands of feet above sea level. Even Arizona is mostly above 500 feet. It might flow into the southern Colorado river, and maybe up to the Salton Sea, but that's about it. On the Other hand, the East Coast would be devastated. Most of Florida would disappear.

Noclevername
2015-Sep-10, 11:54 PM
The densely populated East Coast with most of the US' and Canada's industry and ports? Bad scene, man, bad scene.

BigDon
2015-Sep-11, 04:56 PM
True that, but it won't come so fast as to kill people on the East Coast. Even poor people.

This isn't a storm surge we're talking about. The disruption of the culture and economy are going to be the worst of it. Maybe equal to the last 6 or 7 years only in a much shorter time span.

I have a friend who's family owns an actually percentage, containing whole numbers, of the state of New York. And even though most of the land is butt up to the Adirondacks I can see him being impacted financially.

I know the Bay Area is going to become an archipelago.

Amber Robot
2015-Sep-11, 05:24 PM
I know the Bay Area is going to become an archipelago.

Not according to http://geology.com/sea-level-rise/

The California Central Valley is the bigger loser there.

I will note that both my home and my employer will be inundated by about 3-4 meters of sea rise.

BigDon
2015-Sep-11, 05:48 PM
Amber, if I may call you Amber, that link is so cool that if this board had a thank you and rep system, like modern boards do, I'd give you one of each for that alone.

Darn it, I'm not supposed to be here. I was on my way to somewhere else!

Noclevername
2015-Sep-12, 12:26 AM
True that, but it won't come so fast as to kill people on the East Coast. Even poor people.

Never said it was. It will merely turn them into refugees and render homes, farms, factories and businesses unusable.

BigDon
2015-Sep-16, 08:16 PM
More like migrants than refugees Clev. A major difference.

Noclevername
2015-Sep-16, 10:18 PM
More like migrants than refugees Clev. A major difference.

Not to them. Homeless and desperate is homeless and desperate.

yyyyyyyy
2015-Sep-16, 11:15 PM
At this site (http://thewatchers.adorraeli.com/2013/01/29/rising-sea-level-will-displace-a-substantial-fraction-of-the-human-population/), someone named Benjamin H. Strauss, described as a "Climate Central researcher", estimates that 710 million people are within ten metres of sea level, and 1.3 billion people are within 25 metres; the latter figure is cited as being 21% of the world's population, which suggests that the world population is quite a bit lower than any source I can find would indicate. Having to relocate 1.3 billion people may sound like a lot, but from 1900 until 2000, the world population increased from 1.65 billion to 6.07 billion, an increase of 4.42 billion, or 268% of the 1900 population. Most of these people are neither homeless nor refugees. So several billion new people have been housed, fed, and clothed, during a century that featured several major global wars, radical revolutions, and other upheavals. It is always possible that the world will fail to accommodate the relocation of 1.3 billion in a reasonable way, but it is by no means an impossible task. Most buildings will be torn down before they're 100 years old, even if they are not threatened by rising sea levels.

If accompanying changes make large amounts of farmland barren, that would have an effect, and not just on people living at low elevations.

BigDon
2015-Sep-17, 05:35 PM
Welcome Y, if I may call you Y.

Shallow seas outproduce farmland by an order of magnitude.