Clearest indication yet that polar ice sheets are melting fast

The reality? 11 mm or less over the last 2 decades!

The article claims 11 mm of water solely from melting ice sheets. It says the total increase was five times larger than that.

The increase over the last 19.5 years, 1993 to mid-2012, was between 53-68 mm. The average rate was 3.1 mm/year +/- 0.4.

http://sealevel.colorado.edu/content/2012rel4-global-mean-se...

The original IPCC report on global warming predicted an average rate of global mean sea level rise of about 6 cm per decade.

IPCC AR1 did not predict 6 cm/decade rate for this time; it predicted 6 cm/decade averaged over the century 2000-2100, starting slowly and then accelerating. (Rising CO2 levels accelerate melting; economic growth accelerates CO2 rise).

If you look at AR1's actual forecast,

http://i.imgur.com/2r67Z.png

What it predicted for the near-term, 1990-2010 was (eyeballing the graph): a 9 cm rise, lower range 5 cm, upper range 14 cm. A rate of 2.5-7 mm/year.

The graph is from page 277.

http://www.ipcc.ch/ipccreports/far/wg_I/ipcc_far_wg_I_chapte...

1) sea level rises have always been one of the trickier predictions to make, and the IPCC has never been cagey about this. It's subject to a large number of secondary and tertiary feedbacks, which can cause huge variances in what the models say, and should not be a proxy for how correct models from the 80s and 90s were. Notice that the Wikipedia article actually summarizes the report as saying "6 cm per decade over the next century (with an uncertainty range of 3 – 10 cm per decade)". In other words, there is a lot of variability here, but the best guess (22 years ago...think of the kinds of computers those models were running on) was that the average rise over the next century would be 6cm per decade.

This is quite different than the current article, which is of course about actual measurements and what they mean for the models, which is presumably exactly the kind of verification (one way or the other) that we should be looking for. If the models were wrong (as undoubtedly some were since there are a number of different models and we have to try to reconcile them) then we can go back and figure out why our models were wrong; not throw the baby out with the bathwater.

2) according to your claim, the reality was 11mm (or less) over the last two decades, "over a factor of 100 miss". Now, I'm an American and the metric system confuses me, but isn't half of 11mm 5.5mm, which is .55cm, which would only be a factor of 10 off from 6cm?

3) According to current data (check here[1] for sources and raw data), the sea level actually rose 3.1mm per year from 1993 to 2003. I don't know where you got your 11mm for the last two decades, but the reality adds up to 3.1cm over that decade, only a factor of two off and well within the prediction from 1990, which has of course been supplanted by several reports since then.

The last IPCC assessment even explicitly stated that they can't be certain if the acceleration of sea level rise seen in the last two decades can be expected to continue or if other dynamics will become dominant, as they don't have enough data (for the current trend) and their models might not be sophisticated enough yet. Their best guess in 2007 was 18 to 59cm by 2100, but I believe that's been revised since then.

Hey, what do you know: scientists being scientists. If you actually take time to take a look, they include their confidence intervals every time.

[1] http://www.climatewatch.noaa.gov/article/2009/climate-change...

  > (irreversibly on human time-scales)

"It's happening at a rate that is irreversible on human time-scales"

It's a good thing, then, that there are satellites measuring the earth's gravity, temperature, and land/sea level on a global basis, not just at coastlines. Also, the position of ground-based sensors would be tracked by GPS, so one could tell if the land itself was rising or falling.

As a layperson I've learned that lot of effort goes into developing consistent, scientifically useful models of the earth's shape and position: https://en.wikipedia.org/wiki/Geodesy

The amount of science in "Climate change and ocean rising/falling discussions" makes me want to gouge my eyes out, usually they are about as scientific as pyramid power.

Did you read the linked article? Granted, a lot of popularized articles about climate change contain propagandizing and pounding of phrases like "settled science," and I don't know why that is, but that doesn't invalidate the science that actually exists. Reading a large number of climate change articles on e.g. Ars Technica leaves me with a pretty good impression of the state of actual climate science, certainly better than my impression of "pyramid power."

Edit: since the comment to which I replied was deleted I will not post the username of its author, but here is the original text:

  Plate tectonics cause land to rise/fall faster than the speed at which
  the ocean is rising/falling. Tides are affected by many factors like
  ocean currents, weather patterns, temperatures, changes in the very
  shape of the Earth itself.
  
  The land underneath, the hard bits underneath your chair is floating on
  molten metal. And the water in the ocean is floating on top of this hard
  substance that is floating on molten metal. The surface of the earth is
  in Constant change, half rising, half falling at varying rates.
  
  If the frothing bubbling iron soup under the land were to change at all
  due to gravimetric or other physical reasons, the changes in sea level
  would be far more dramatic than what is measured in the sea level
  change. You can't just go to your local beach and stick a measuring pole
  in the sand with a calendar and a clock. Likewise you can't just go to a
  thousand randomly selected beaches and run averages, why?  Because you
  are only testing the ocean's edges, you need to randomly test the depth
  of the ocean at every point.
  
  To do this right, you must actually calculate the volume of Ocean water,
  and this hurts people's brains because it is impossible and isn't good
  for FUD articles.
  
  It could very well be possible that the oceans would normally be
  receding on account of other factors, yet it is still rising from the
  perspective of beaches because the Earth is becoming more spherical.
  
  The amount of science in "Climate change and ocean rising/falling
  discussions" makes me want to gouge my eyes out, usually they are about
  as scientific as pyramid power.  I choose to ignore people who talk
  about these sorts of things because I like to learn things by proofs,
  not be taught to believe things because of propaganda and agenda driven
  fear uncertainty and doubt for the profit of unscrupulous manipulators.

That's not what I've been hearing. I see people saying that no individual weather event or localized change can be attributed to global climate change, but that as more total energy is added to the earth system, more chaotic weather events and localized changes can be expected in aggregate (edit: e.g. http://youtu.be/5EaLVOv8cIk?t=1m49s).