Two articles on the latest "melting icecap" scare

Antarctica: Long Term Policy, Short Term Data - A Poor Fit

Post lifted from The Commons blog

Today we were subjected to breathless news reports that - to quote the Washington Post's page one headline - the "Antarctic Ice Sheet Is Melting Rapidly: New Study Warns Of Rising Sea Levels". Its author, Juliet Eilperin, goes on to state that the ice sheet "is losing as much as 36 cubic miles of ice a year in a trend that scientists link to global warming, according to a new paper ..."

So what is this "trend" based upon? The trend, reported in a paper in yesterday's Sciencexpress [1], which offers previews of coming attractions in Science magazine, is based on data collected over a 34-month period!

Sorry, Juliet, 34 months does not a "trend" make, unless you are 3-year old, in which case you can be forgiven for thinking that's a truly long time. like ... almost forever. Juliet, however, does go on to restore some balance to her story by quoting Richard Alley, "One person's trend is another person's fluctuation." Bravo!

Let's now look at the second part of the two-punch headline, namely, the warning regarding rising sea levels. It turns out that the resulting ice melt would raise sea level by 0.4 millimeters per year. Well, that works out to 1.6 inches per century. I guess I better hurry and relocate to higher ground - I have heard you can drown in a thimble-full of water (and I don't swim). That also means 1.3 feet in a 1,000 years. Seems I have to live longer than Methuselah to enjoy that beachfront property. Damn!

This is the second time in a month that there has been much ado about short term trends. In mid-February, another paper in Science reported that the glaciers in Greenland were melting more rapidly than previously thought [2]. That paper estimated that Greenland ice sheet was losing 224 cubic kilometers per year. That means it will take another 5,400 years to melt the remaining 1,200,000 cubic km, which might raise sea level by 23 feet (7 meters), or so I am told. That is a sea level rise of 0.05 inches per year.

Now this second paper was based on as much as 9-years worth of data. Phenomenal by comparison - but is this long enough?

To get an idea as to the answer, nearby I have two plots of temperature "anomalies' (i.e., fluctuations around the long term means) from 1880 through 2005 for the Antarctic (actually everything south of 60 degrees S). The top curve provides trends for land surface temperatures. The bottom curve is a composite for land and sea temperatures, hence the difference between the magnitude of the trend (0.12 degrees C per decade vs. 0.01 degrees C per decade).

What this shows is that you can get any kind of trend you want depending on when you start your 3- or 9-year period. Ditto, if you want to work with a 50- or 60-year period. In other words, beware long term policies based on short term data [3].

Nevertheless, the Washington Post reports that based partly on these studies, Sen. John F. Kerry (Mass.) and Rep. Henry A. Waxman (Calif.) said yesterday that the "United States must act quickly to impose mandatory limits on carbon dioxide and other greenhouse gases."

Perhaps, from the point of view of these two gentlemen, any "fluctuation" that lasts for 2 or 6 years is sufficiently long to base robust policy on.






Greenland and Antarctic Contributions to Sea Level Rise

(Article from CO2 Science Magazine)

Reference:

Zwally, H.J., Giovinetto, M.B., Li, J., Cornejo, H.G., Beckley, M.A., Brenner, A.C., Saba, J.L. and Yi, D. 2005. Mass changes of the Greenland and Antarctic ice sheets and shelves and contributions to sea-level rise: 1992-2002. Journal of Glaciology 51: 509-527.

What was done:

The authors determined changes in ice mass "from elevation changes derived from 10.5 years (Greenland) and 9 years (Antarctica) of satellite radar altimetry data from the European Remote-sensing Satellites ERS-1 and -2."

What was learned:

Zwally et al. report that "the Greenland ice sheet is thinning at the margins (-42 ? 2 Gt a-1 below the equilibrium-line altitude (ELA)) and growing inland (+53 ? 2 Gt a-1 above the ELA) with a small overall mass gain (+11 ? 3 Gt a-1; -0.03 mm a-1 SLE (sea-level equivalent))." Likewise, they say that "the ice sheet in West Antarctica (WA) is losing mass (-47 ? 4 Gt a-1) and the ice sheet in East Antarctica (EA) shows a small mass gain (+16 ? 11 Gt a-1) for a combined net change of -31 ? 12 Gt a-1 (+0.08 mm a-1 SLE)." Hence, they report that "the contribution of the three ice sheets to sea level is +0.05 ? 0.03 mm a-1." Furthermore, although not impacting sea level, they note that "the Antarctic ice shelves show corresponding mass changes of -95 ? 11 GT a-1 in WA and +142 ? 10 Gt a-1 in EA."

What it means:

We often hear horror stories about the potential for Greenland and Antarctica to add many meters to the level of the seas in response to global warming. However, Zwally et al. put things in proper perspective by noting that the real-world data they processed indicate that the ongoing contribution of the Greenland and Antarctic ice sheets to sea-level "is small relative to the potential contribution from ice sheets." How small? At the current sea-level-equivalent ice-loss rate of 0.05 millimeters per year, it would take a full millennium to raise global sea level by just 5 cm, and it would take fully 20,000 years to raise it a single meter. In addition, Zwally et al. report that "the contribution of the ice sheets is also small compared to the most recent estimate of current sea-level rise of 2.8 ± 0.4 mm a-1 from satellite altimetry (Leuliette et al., 2004)," which in their words, "further confounds possible explanations of the causes of contemporary sea-level rise."

In conclusion, the real-world findings of Zwally et al. suggest that the climate-alarmist hype about global warming causing sea levels to rapidly rise to dangerous heights due to the mass wasting of earth's great ice sheets is simply false. This outrageous claim is nothing more than a scare tactic designed to persuade the public to accept the bitter pill they prescribe for the solving of a patently obvious non-problem.

(For more postings from me, see EDUCATION WATCH, GREENIE WATCH, POLITICAL CORRECTNESS WATCH, GUN WATCH, SOCIALIZED MEDICINE, AUSTRALIAN POLITICS and DISSECTING LEFTISM. My Home Page. Email me (John Ray) here.)

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