I will, as usual, be taking my annual virtual trip to the North Pole. Thanks, Captain Neven!

A correction to the clarifications: What you are describing could be called "Degree Days". But we are talking about "Degree Days Freezing" which means that only temperatures below zero count. I.e. while "-10C" adds 10 to the cumulative total, "+2C" leaves the total unchanged. On Neven's Sea Ice Graph Page, there is also a "Degree Days Thawing" (and its associate anomaly), in which all negative temperatures have been replaced with 0.

I would like to completely disagree about the possible effectiveness of a carbon tax. When gasoline hit $5.00 / gallon in California a few years ago, bus ridership skyrocketed, especially during the commute hours. Where two busses per hour were all that were needed to pick up everyone on my route before that (and they were only 50% full), they were able to run 6 SRO busses per hour for over a month (until gas prices fell again). I have no doubt that $10.00 / gallon would further increase the use of public transit. And while people may not trade in their SUVs immediately, they tend not to replace them when gas prices are high. http://www.washingtonpost.com/wp-dyn/content/article/2005/10/03/AR2005100301657.html

Hi, Rob. I enjoyed seeing your hindcast above, and was particularly impressed by the delta=-0.09 for 2012. I have an idea for correcting for the "data point in the training set" bias you refer to: Calculate your parameters by deleting the year you are calculating. (I.e. if you are using 1992-2012 as the baseline, then when calculating 2006, you'd use 1992-2005 union 2007-2012, but not 2006) My guess is that it would still be fairly darn good and would allow you to more accurately determine of the correct confidence interval, etc.

Did anyone else notice that Climate Change was the front page story on the New York Times? http://www.nytimes.com/2015/01/17/science/earth/2014-was-hottest-year-on-record-surpassing-2010.html?_r=0

The PIOMAS graph has been updated for August.

I just noticed that nsidc has posted a mid-month update: http://nsidc.org/arcticseaicenews/2014/07/melting-in-the-north-freezing-in-the-south/

This is slightly OT, but has anyone heard from Jim Pettit?

A4R, I noticed a typo in your blog, please correct: "global mean methane topping 398 ppm on March 11 2014 12-24 hrs UTC at 945 mb" Should obviously be global CO2.

I hope you are right, Hans. However, my fear is that, as oil gets harder to find, we will switch to fuels with worse and worse carbon footprints. The Alberta tar sands are definitely a giant leap in this direction..

Forgive me for going off-topic, but I feel the need to point out that an Eulerian Path visits each EDGE once, not each VERTEX once: http://en.wikipedia.org/wiki/Eulerian_path

At the risk of getting more egg on my face, I'd like to point out two minor typos in Kevin McKinney's otherwise excellent paper: One, You typed "namy" instead of "many". Two, Each water molecule has only one oxygen atom, not two.

Facepalm! Kevin McKenney was completely correct. Everyone else labeled theirs mean versus min, and I somehow read his backwards. Sorry for any confusion.

I'm curious at the difference that some people have between their "Mean" and "Min" September values: Name Mean Min Diff Kevin O'Neill 2.9 2.5 14% DoomComesSoon 1.7 1.478 13% NLPatents 3.0 < 3.0 At least 0% Kevin McKinney 3.24 3.43 -6% wili 1.5 0.9 40% Noting that the historical difference is between 1.0% and 7.5% (with an average of 3.4%) -- although admittedly it has been trending upwards, though not by that much. I am most concerned by Kevin McKinney, who raised his estimate. I'd guess that he applied his correction in the wrong direction, since 6% seems not unreasonable. Note that NLPatents makes sense, I am including it only for completeness.

2.8 Mkm2 +- 0.7 Mkm2 Trying to estimate where the trend is going by eyeball.

@Chris Reynolds Thanks for that analysis on our shrinking volume. However, I spent a few minutes scratching my head over one line before realizing that it was just a typo: And for comparison... 2013 3.261 actual That would be "2012 3.261 actual", right?

@Boa05att It may not be as much of a shock as you claim, as they also say: "The general view that the ice-cap is not at risk of a summer collapse in the next few years may need to be revisited and revised."

Just pointing out that crandles didn't disprove the paper. The paper said "increased area" and crandles demonstrated "near-constant volume". I bet both are correct.

I don't know what Kris means by "twice as high" (given that the temperatures are below 0 Celcius) but the average of the average values is -1.85C and the average of the normal values is -6.57C.

Oh, discussing nits reminds me, on the Rob's Masie spaghetti plot there is an extraneous "13) Baltic Sea" in the lower left hand corner of the map.

The "shining star" is the area where not enough sunlight falls for MODIS to capture an image. (Also called the "Pole hole" on this blog if you want to search for it.) I am pretty sure that the green is real, and it seems likely to be algae or something similar (though I am no expert).

@Wayne Kernochan In other words, 2 1/2-5 meters may be a low estimate. Actually, I believe that it is similar to "Moore's Law" (the prediction of the doubling of computer processor capabilities every 18 months). Hanson isn't specifying "why" the doubling should continue, and it is possible that this is simply one of the unknown unknowns that will cause it. @Peter Ellis Sorry, that's plain wrong. Assuming a constant doubling time is simply projecting an unbounded exponential, which is not just physically implausible, but literally impossible. Any exponential increase will stop, what matters is when. Well, of course the doubling would stop when there is no more ice to melt. :( With that said, however, some people on this blog prefer a Gompertz curve because the last little bit will be the bit that is most resistant to melting. Only the future knows for sure, but any scenario of runaway ice loss is a very bad thing.

@George Phillies I think the answer is "instantly" (given your rather magical assumptions). The volume of the Antarctic Ice Cap is ~25M km2 and the volume of the ocean is @1.3B km2. That's a ratio of over 40:1. Since the heat of fusion of ice is roughly 80cal/g, the average temperature of the ocean would need to be about 2C. Looking at this graph and noting that the average depth of the ocean is only 4000m, I'd say there's probably enough heat right there. http://www.windows2universe.org/earth/Water/temp.html

Looking at this graph from google: http://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&met_y=ny_gdp_mktp_cd&idim=country:USA&dl=en&hl=en&q=us+gdp I'd agree that the US GDP has grown all but one year. That doesn't mean that the per capita has, but I'd assume that the per capita is not what's relevent to total energy use/electricity use/CO2 emissions.

@Seke Rob, I've been meaning to point this out for a while. You put "9.10.12" for the date of the prior record on PIOMAS daily, which I assume should be "9.10.11" bill