[Vision2020] NASA GISS: Dec. 8 2011: "Paleoclimate Record Points Toward Potential Rapid Climate Changes"
Paul Rumelhart
godshatter at yahoo.com
Wed Dec 14 19:20:47 PST 2011
James Hansen is expecting a 20 meter sea level rise for every degree of
warming? It's already warmed a bit more than half a degree C since the
late 1800s. Where's our 12 meter sea level rise? In contrast, sea
level has risen about 0.2 meters in the same time period. I understand
that he isn't saying that we'll get all 20 meters at once.
Googling around the web a bit comes up with about a 3.1 mm/year sea
level rise, which is the "accelerated" rate they are worried about in
recent decades.
20 m * (1 yr / 0.0031 m) ~= 6450 yr
This level should be reached at around year 8461 BCE, given the current
rate of sea level rise. I think we'll have time to deal with it as it
happens. And that's for one degree. If we get the expected 3, which is
a little conservative, then we'll get to that level on or around 21365 BCE.
If we got all 20 meters by 2100, then that would mean a sudden
acceleration to: 20 m / (2100 - 2011) yr = 0.225 m/yr. So we would
expect to see as much sea level rise, on average, every year that we've
seen so far since pre-industrial times for this to happen.
As it stands, if the current rate of sea level rise continues, we should
expect a sea level rise of (2100 - 2011) * .0031 m = 0.276 m. A little
more than a years worth of Hansen's figures. Just one meter of sea
level rise would mean that the current sea level rise would have to
almost quadruple in the next few years.
And people wonder why I'm skeptical.
Paul
On 12/14/2011 04:06 PM, Ted Moffett wrote:
> Monday Dec. 12, 2011 the "Lewiston Tribune" front page headline read
> "Climate Deal Extends Status Quo."
> http://lmtribune.com/editors_pick/article_e889c1b8-bb55-5783-9fb1-4635ca902dee.html
>
> The article was sourced from "The Associated Press," authored by Maxx
> and Ritter, so my comments do not directly apply to "Lewiston Tribune"
> journalists
> The headline might have read, to address the magnitude of the problem
> humanity is potentially facing, "No Substantive Climate Deal Portends
> Meters of Sea Level Rise by 2100" if the article was referencing
> credible peer reviewed science on this issue ("Global sea level linked
> to global temperature"
> http://www.pnas.org/content/early/2009/12/04/0907765106.full.pdf ).
> Instead, the article meekly declared "Scientists say that if levels of
> greenhouse gases continue to rise, eventually the world's climate will
> reach a tipping point, with irreversible melting of some ice sheets
> and a several foot rise in sea levels."
> Several foot rise? How about potentially meters of sea level rise by
> 2100? With more to follow as climate change continues into the next
> century:
> National Academies Press: "Beyond the Next Few Centuries: Long-Term
> Feedbacks and Earth System Sensitivity"
> http://www.nap.edu/openbook.php?record_id=12877&page=217
> <http://www.nap.edu/openbook.php?record_id=12877&page=217>
> Read this recent release from NASA's Goddard Institute for Space
> Studies, regarding a paper now "in press" (abstract at bottom):
> http://www.giss.nasa.gov/research/news/20111208/
>
>
> Research News
>
>
> Paleoclimate Record Points Toward Potential Rapid Climate Changes
>
> Dec. 8, 2011
>
> */Related NASA AGU news briefing materials may be found here
> <http://www.nasa.gov/topics/earth/features/rapid-change.html>./*
> *//*
>
> New research into the Earth's paleoclimate history by NASA's Goddard
> Institute for Space Studies director James E. Hansen suggests the
> potential for rapid climate changes this century, including multiple
> meters of sea level rise, if global warming is not abated.
>
> By looking at how the Earth's climate responded to past natural
> changes, Hansen sought insight into a fundamental question raised by
> ongoing human-caused climate change: "What is the dangerous level of
> global warming?" Some international leaders have suggested a goal of
> limiting warming to 2 degrees Celsius from pre-industrial times in
> order to avert catastrophic change. But Hansen said at a press
> briefing at a meeting of the American Geophysical Union in San
> Francisco on Tues, Dec. 6, that warming of 2 degrees Celsius would
> lead to drastic changes, such as significant ice sheet loss in
> Greenland and Antarctica.
>
> Based on Hansen's temperature analysis work at the Goddard Institute
> for Space Studies, the Earth's average global surface temperature has
> already risen .8 degrees Celsius since 1880, and is now warming at a
> rate of more than .1 degree Celsius every decade. This warming is
> largely driven by increased greenhouse gases in the atmosphere,
> particularly carbon dioxide, emitted by the burning of fossil fuels at
> power plants, in cars and in industry. At the current rate of fossil
> fuel burning, the concentration of carbon dioxide in the atmosphere
> will have doubled from pre-industrial times by the middle of this
> century. A doubling of carbon dioxide would cause an eventual warming
> of several degrees, Hansen said.
>
> In recent research, Hansen and co-author Makiko Sato, also of Goddard
> Institute for Space Studies, compared the climate of today, the
> Holocene, with previous similar "interglacial" epochs — periods when
> polar ice caps existed but the world was not dominated by glaciers. In
> studying cores drilled from both ice sheets and deep ocean sediments,
> Hansen found that global mean temperatures during the Eemian period,
> which began about 130,000 years ago and lasted about 15,000 years,
> were less than 1 degree Celsius warmer than today. If temperatures
> were to rise 2 degrees Celsius over pre-industrial times, global mean
> temperature would far exceed that of the Eemian, when sea level was
> four to six meters higher than today, Hansen said.
>
> "The paleoclimate record reveals a more sensitive climate than
> thought, even as of a few years ago. Limiting human-caused warming to
> 2 degrees is not sufficient," Hansen said. "It would be a prescription
> for disaster."
>
> Hansen focused much of his new work on how the polar regions and in
> particular the ice sheets of Antarctica and Greenland will react to a
> warming world.
>
> Two degrees Celsius of warming would make Earth much warmer than
> during the Eemian, and would move Earth closer to Pliocene-like
> conditions, when sea level was in the range of 25 meters higher than
> today, Hansen said. In using Earth's climate history to learn more
> about the level of sensitivity that governs our planet's response to
> warming today, Hansen said the paleoclimate record suggests that every
> degree Celsius of global temperature rise will ultimately equate to 20
> meters of sea level rise. However, that sea level increase due to ice
> sheet loss would be expected to occur over centuries, and large
> uncertainties remain in predicting how that ice loss would unfold.
>
> Hansen notes that ice sheet disintegration will not be a linear
> process. This non-linear deterioration has already been seen in
> vulnerable places such as Pine Island Glacier in West Antarctica,
> where the rate of ice mass loss has continued accelerating over the
> past decade. Data from NASA's Gravity Recovery and Climate Experiment
> (GRACE) satellite is already consistent with a rate of ice sheet mass
> loss in Greenland and West Antarctica that doubles every ten years.
> The GRACE record is too short to confirm this with great certainty;
> however, the trend in the past few years does not rule it out, Hansen
> said. This continued rate of ice loss could cause multiple meters of
> sea level rise by 2100, Hansen said.
>
> Ice and ocean sediment cores from the polar regions indicate that
> temperatures at the poles during previous epochs — when sea level was
> tens of meters higher — is not too far removed from the temperatures
> Earth could reach this century on a "business as usual" trajectory.
>
> "We don't have a substantial cushion between today's climate and
> dangerous warming," Hansen said. "Earth is poised to experience strong
> amplifying feedbacks in response to moderate additional global warming."
>
> Detailed considerations of a new warming target and how to get there
> are beyond the scope of this research, Hansen said. But this research
> is consistent with Hansen's earlier findings that carbon dioxide in
> the atmosphere would need to be rolled back from about 390 parts per
> million in the atmosphere today to 350 parts per million in order to
> stabilize the climate in the long term. While leaders continue to
> discuss a framework for reducing emissions, global carbon dioxide
> emissions have remained stable or increased in recent years.
>
> Hansen and others noted that while the paleoclimate evidence paints a
> clear picture of what Earth's earlier climate looked like, but that
> using it to predict precisely how the climate might change on much
> smaller timescales in response to human-induced rather than natural
> climate change remains difficult. But, Hansen noted, the Earth system
> is already showing signs of responding, even in the cases of "slow
> feedbacks" such as ice sheet changes.
>
> The human-caused release of increased carbon dioxide into the
> atmosphere also presents climate scientists with something they've
> never seen in the 65 million year record of carbon dioxide levels — a
> drastic rate of increase that makes it difficult to predict how
> rapidly the Earth will respond. In periods when carbon dioxide has
> increased due to natural causes, the rate of increase averaged about
> .0001 parts per million per year — in other words, one hundred parts
> per million every million years. Fossil fuel burning is now causing
> carbon dioxide concentrations to increase at two parts per million per
> year.
>
> "Humans have overwhelmed the natural, slow changes that occur on
> geologic timescales," Hansen said.
>
>
> Web Link
>
> NASA/GISS Science Brief: Earth's Climate History: Implications for
> Tomorrow <http://www.giss.nasa.gov/research/briefs/hansen_15/>
>
>
> Reference
>
> Hansen, J.E., and Mki. Sato, 2011: Paleoclimate implications for
> human-made climate change
> <http://pubs.giss.nasa.gov/abs/ha05510d.html>. In Climate Change:
> Inferences from Paleoclimate and Regional Aspects. A. Berger, F.
> Mesinger, and D. Šijači, Eds. Springer, in press.
>
> ----------------------------------------
>
> http://pubs.giss.nasa.gov/abs/ha05510d.html
>
>
> Publication Abstracts
>
>
> Hansen and Sato 2011, in press
>
> Hansen, J.E., and Mki. Sato, 2011: Paleoclimate implications for
> human-made climate change. In Climate Change: Inferences from
> Paleoclimate and Regional Aspects. A. Berger, F. Mesinger, and D.
> Šijači, Eds. Springer, in press.
>
> Paleoclimate data help us assess climate sensitivity and potential
> human-made climate effects. We conclude that Earth in the warmest
> interglacial periods of the past million years was less than 1°C
> warmer than in the Holocene. Polar warmth in these interglacials and
> in the Pliocene does not imply that a substantial cushion remains
> between today's climate and dangerous warming, but rather that Earth
> is poised to experience strong amplifying polar feedbacks in response
> to moderate global warming. Thus goals to limit human-made warming to
> 2°C are not sufficient — they are prescriptions for disaster. Ice
> sheet disintegration is nonlinear, spurred by amplifying feedbacks. We
> suggest that ice sheet mass loss, if warming continues unabated, will
> be characterized better by a doubling time for mass loss rate than by
> a linear trend. Satellite gravity data, though too brief to be
> conclusive, are consistent with a doubling time of 10 years or less,
> implying the possibility of multi-meter sea level rise this century.
> Observed accelerating ice sheet mass loss supports our conclusion that
> Earth's temperature now exceeds the mean Holocene value. Rapid
> reduction of fossil fuel emissions is required for humanity to succeed
> in preserving a planet resembling the one on which civilization developed.
>
> ------------------------------------------
>
> Vision2020 Post: Ted Moffett
>
>
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