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Can't quite get the animation at http://cci-reanalyzer.org/Forecasts/ to load fully, but the frames which I did see clearly show a pretty huge temp anomaly forecast for later this week... http://imgur.com/eQNvqpE

L. Hamilton

A bar graph showing annual minimum PIOMAS volume, updated through 2014, can be found here:


Adam Ash

Thanks for the update Neven. I'm always a tad puzzled by your use of the term 'rebound' in relation to the minor annual wriggles we are seeing around the overall trend of ice volume decline. With respects, the term smacks of wishful thinking, or King Canuteism, I'm not sure which.

The Big Picture is that present annual minimum Arctic sea ice volume is currently ten thousand cubic kilometres less than it was when we started to take notice in the late 1970s.


When that 10km3 loss is considered in the context of the recent observed minimum of just under four thousand cubic kilometres its clear that the Arctic and hence the climate (particularly the climate of the Northern Hemisphere) is in very 'hot water' indeed.

Should the annual minimum ever get back above its historic 15,000 km3 norm I would accept use of the term 'rebound', but until then (I suggest we will need to wait for several million years, if ever), its not a 'rebound', its a just a twitch from a dying ice block.

Bill Fothergill


Whilst in no way wishing to put words in Neven's mouth, I think you'll find that the use of the term "rebound", or "recovery" for that matter, has more to do with a touch of sarcasm than anything else.

In certain quarters, any metric that is not a record is instantly sized upon as unequivocal proof of a recovery/rebound or whatever other bollox one cares to employ.

The rationale is pretty straightforward. Whichever metric is under discussion, be it volume, area, extent, or temperature, most years fail to produce a new record.

For example, the (multi-channel) NSIDC monthly sea ice extent data starts at 1979. There has therefore been 35 opportunities for the September minimum figure to be beaten. However, record figures have only been set on 8 occasions. (1984, 85, 90, 95, 2002, 05, 07, 12) This represents only about 0.23 of the time. If one rounds to the nearest whole number, this then equates to zero.

Hence, one can easily see that the logic is absolutely impeccable: if it's not a record most of the time, it's not happening.

Hope that helps somewhat. (Now exiting sarc mode)

Philip Cohen

I see no sarcasm in the use of 'rebound'. By any reasonable standard 2013 was a big jump upward: about three times the size of the 2012 fall, whether by square miles or percentage, and that was big enough that people were predicting a quick collapse in ensuing years.

What 2013 was not, was a recovery: 'regaining a normal position or condition'. Denialists conflate the two, as Bill Fothergill says; that doesn't mean we have to.

Bert van den Berg

Thanks for the chart of annual minimum arctic ice volume. The increase of the last two years is certainly the largest over the 35 years plotted. However what is more interesting to me is that the 35 years of data does not show 3 years in a row of increasing volume. I believe the same applies for the chart of annual minimum ice area. Thus in looking at past history, we should be confident next year will feature a decline in ice area and volume (in other words, an increase in ice volume next year is a low probability event).


Thanks for chiming in, Philip Cohen. You've explained it well.

I see recovery as becoming healthy, like a patient or something. This is not the case (yet) with Arctic sea ice.

A rebound to me is like a ball bouncing up and down. Now it's bouncing up, and like Bert van den Berg says, at some point it will bounce down again. In theory, the bounces become smaller until the ball lies on the floor.

But to stretch the analogy further: before the ball stops bouncing and stays on the floor (ie Arctic becomes ice-free for all practical purposes), it already becomes increasingly difficult to keep dribbling. Anyone who has played basketball, knows this.

In other words: the consequences of Arctic sea ice loss are already happening. They don't start when the Arctic becomes ice-free. That's 'just' an iconic image that can't be wished away.

Pete Williamson

Neven to stretch your basketball analogy a bit further, any team that ignores rebounds is going to lose the game! ( caveat I know as little about basketball as I do about climate science)

I would have thought the past two years would have taught us a little more about the role of internal variability/dynamics on arctic ice.It seems particularly interesting because its moving in the opposite direction to the way we might expect radiative forcing to affect the ice.


Sorry to be off topic here Neven but.......I just wanted to help spread the word about this climate related fund-raising project, last 4 days & they are 3/4 the way there!

See the details over at the Forum, on this link:


The trend in sea ice over the last 30-some years certainly appears to be negative, but surely no one believes that a linear model is appropriate over an extended period of time. The stock market was in a down trend from September 19th to Oct 9th that looked just as convincing as the graph above, but since then, it sold off big and then rebounded to even higher highs. Likewise, the market has been in an even larger linear uptrend for the last three years, but surely no one thinks that will last forever.

I have no idea whether the sea ice will continue to get thinner or whether it has already started to thicken, but a 30 year trend line doesn't tell a person much. If solar irradiance continues to decline, I would bet the ice will continue to get thicker, but I have no way to predict solar irradiance either.

Just my 2 cents worth.


With respect, drphilosopher, stock trends do not equal Actic trends in terms of the fundamental mechanics driving variability.

I'll add also that to toss out a comment on decreasing insolation is a bit of a red herring; total available heat driving climate is increasing even while various cycles - both solar and orbital - are slightly decreasing net northern hemisphere insolation received.

The driver of observed long term changes is CO2 and related greenhouse gasses released as a side effect of human activity, not insolation changes.

Chris Reynolds


Note that the second plot in the above image shows irradiance and sea ice, from that plot one would come to the conclusion that a higher level of insolation leads to more sea ice, this is obviously absurd. This relationship happens because the decline in sea ice driven by human activities has happened as solar insolation has fallen as we have left the Grand Solar Maximum of the mid to late 20th century. As JD Allen points out, the insolation decline will have little effect.

Those above images are from these two sources (in order).

Johannessen 2008, "Decreasing Arctic Sea Ice Mirrors Increasing CO2 on Decadal Time Scale." https://bora.uib.no/bitstream/1956/2840/1/200806005.pdf

Notz & Marotzke, 2012, "Observations reveal external driver for Arctic sea-ice retreat" http://www.mpimet.mpg.de/fileadmin/staff/notzdirk/2012GL051094.pdf

In the following image of model runs the coloured lines include anthropogenic forcings, the grey lines don't.

Put simply, without human impacts there is no decline of sea ice. That image is from Wang & Overland, 2012, A sea ice free summer Arctic within 30 years? - CMIP5 Update.


With all due respect to my interlocutors, correlation isn't causation. One would expect the CO2 level to rise with ocean temperature because the solubility of the ocean decreases as its temperature rises. A rise in ocean temperature would also account for a decrease in arctic ice extent. So, one would expect the level of CO2 in the atmosphere to be negatively well correlated with arctic sea ice volume, even if the relationship is not causal.

So, what might be causing the rise in ocean temperature? Perhaps, it's just hysteresis.

Every summer, the solstice occurs around June 21st, but the hottest day of the summer usually occurs some time in July or August, depending upon where you are in the country. Why? Because of hysteresis. The current temperature depends not only on the current forcing function, but on its past history and the history of the temperature of the land. Moreover, the amount of hysteresis tends to depend upon the amount of water nearby. In a place like Colorado which is semi-arid, there is very little hysteresis and the hottest days of the year sometimes occur in late June, though usually in July. In the Midwest, it's usually in July. In California, near the coast, it is usually even later.

The ocean as a whole is very slow to heat and cool. So, even though the solar forcing function peaked some time ago, one shouldn't jump to the conclusion that the ocean is not still warming as a result of solar forcing. I don't know how much hysteresis is in the system, but it wouldn't surprise me if the trends we are seeing in global climate change have a lot to do with such factors. It is possible that the land temperature has ceased to increase because it is not effected as much by hysteresis but that the ocean is still warming because it is such an enormous heat reservoir. Of course, the ocean will affect the land and vice versa, but won't necessarily overwhelm local conditions.

At any rate, if hysteresis is a large factor, one wouldn't necessarily expect to see a strong correlation between solar irradiance and surface temperature over a relatively short time frame. Every year between June 21st and the time the temperature reaches its maximum later in the summer, the average daily insolation (if you prefer) is negatively correlated with the temperature change. So, the fact that the average yearly insolation is negatively correlated with the mean surface temperature change since the time of the most recent solar maximum doesn't mean much if taken in isolation.

One would expect the CO2 level to rise with ocean temperature because the solubility of the ocean decreases as its temperature rises.

One would expect the CO2 level to rise when Gigatons of carbon are burnt and emitted every year to keep human civilisation in its current economic set-up going. The oceans are a carbon sink and take up a large part of these CO2 emissions (with the added effect of making them become less alkaline/more acid). But you are indeed right that when the oceans stop taking up part of that excess CO2 in the atmosphere, the CO2 concentration will rise even faster. Under a business-as-usual scenario, that is.

So, what might be causing the rise in ocean temperature? Perhaps, it's just hysteresis.

Do you mean inertia?


drphilosopher - you are misinterpreting the physical chemistry of CO2.

For what you are saying to be true, ocean CO2 would need to be saturated. That is not true. It would have to be declining. That also is not true.

Oceans are not, have never been a primary source for C02 in the atmosphere. They are, and always will be a sink for CO2. The tangible truth of that exists in the Ordovician limestones I scrambled over mapping stratigraphy in the Hudson valley decades ago. It is expressed in every other calcareous marine sediment laid down over geologic eras.

The flow of CO2 is into, not out of the oceans. Your premise is false, and illustrates a need on your part to expend the energy to improve your understanding of the basic science.

Chris Reynolds

The oceans are acidifying. Therefore the oceans are not the source of the increase in atmospheric CO2.

When I was a sceptic such trash was doing the rounds, I am amazed to see it is still being claimed, especially when sceptics (well he was one when I was one) such as Ferdinand Engelbeen have thoroughly destroyed the argument and demonstrated how the CO2 increase is man made.

The correlation between CO2 and sea ice is with global CO2, not local CO2 levels above the ice.

Inertia isn't a bad analogy, but what is actually happening is latency caused by energy storage. It takes time for land and ocean to warm causing a lag behind insolation in the annual cycle. Strictly speaking inertia refers to a mechanical effect, but there is the term 'thermal inertia'.

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