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Messages - BenB

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Arctic sea ice / Re: The 2020 melting season
« on: July 16, 2020, 01:37:36 PM »
I haven't had any time for sea ice this year, but wow, this season is exceptional. I thought it was worth reminding ourselves where the ice is this year vs. 2012 (first image). Basically, 2020 is slightly ahead north of the Barents and Kara seas, ahead in Chukchi, and far ahead in ESS and Laptev. In the areas that matter, 2012 is only far ahead in Beaufort. Having said that, an extent comparison exaggerates the difference a bit, as there is greater compaction in 2020.

Then, looking at current melt conditions, I looked back at Worldview for the second half of July in 2012, 2016 and 2019. All were dominated by cloudy weather, although 2012 did clear up a few times. 2020 is forecast to stay relatively clear.

Looking at the most recent day in 2012 and 2020 (2nd and 3rd image), the difference is striking. 2012 has slightly more rubble north of Beaufort, and obviously much less ice in Beaufort, but apart from that 2020 looks worse in every way. There is definitely more melt ponding/surface wetness in 2020. Cloud cover speaks for itself.

Qs: Is insolation in the second half of July strong enough to do so much damage to the relatively thick ice in the CAB that some of it will melt out by the end of the season?
Will continued clockwise rotation of the ice push the weak-looking ice in the ESS into the warm Laptev waters? If so, it won't be long of this world. Will some of the Beaufort ice also be pushed into warmer waters?
Will the Atlantic ice edge continue to push north, or will it stagnate just north of Svalbard/Franz Josef?
Is this the big year, or is it just setting us up for next year?

Arctic sea ice / Re: The 2019 melting season
« on: August 28, 2019, 10:55:56 AM »
I think the rebound on the Pacific side is matched by a reduction in concentration further into the pack on that side, which is consistent with the low over Beaufort and what you can see on Modis - ice being pushed south into Chukchi/Beaufort from the central pack, leaving gaps behind further north. The low stays around for a couple of days more, although it's not very deep, so the general pattern should continue. Most of the ice that gets pushed into Chukchi/Beaufort melts fairly quickly, so I don't think the advances will last long. The question is how significant the reduction in concentration deeper into the pack will become.

Policy and solutions / Re: Renewable Energy
« on: August 27, 2019, 10:06:15 PM »
Gerontocrat, I know about the unit conversion page, but ultimately that's generally information you can work out for yourself anyway. The bit that's missing is their own methodology for calculating the primary energy in each energy source, which is individual to each source and hence not covered by the unit converter. You can find some of that information on other pages, but they don't go out of their way to make it easily accessible.

Policy and solutions / Re: Renewable Energy
« on: August 27, 2019, 04:14:19 PM »
You're welcome Terry. It would make life easier if all of the main providers of statistical information used the same methodology, but I suppose that – like with sea ice – the various methods all have their merits, and different agencies/companies prefer different ones.

I think that the IEA could be clearer with how they do their calculations, as you have to dig around quite a bit to find the information, and it's not all in one place. Even now, I haven't been able to find their explanation of how they calculate the primary energy for coal, but I've tried to infer it as best I can from their comments and the figures for electricity generation vs. primary energy.

Policy and solutions / Re: Renewable Energy
« on: August 27, 2019, 12:12:48 PM »
Yes, Oren, but a couple of points to bear in mind:

  • I believe most of the renewables in the IEA figures are biomass - basically people burning wood for food and heating in poorer countries. So if you treble the contribution from "modern" renewables, the total amount of renewables doesn't increase as much as you might expect, but the change over the past decade say is much more pronounced.

  • It's the IEA, not EIA. This may seem pedantic, but confusingly the EIA is the Energy Information Administration, which is responsible for energy statistics in the US. The IEA is the International Energy Agency, which is a kind of think tank on energy matters for the OECD countries.

Policy and solutions / Re: Renewable Energy
« on: August 27, 2019, 10:38:48 AM »
This page is also useful for understanding the IEA methodology:

"For instance, in the case of nuclear electricity production, as heat is the primary energy form selected by the IEA, the primary energy equivalent is the quantity of heat generated in the reactors. However, as the amount of heat produced is not always known, the IEA estimates the primary energy equivalent from the electricity generation by assuming an efficiency of 33%, which is the average of nuclear power plants in Europe. In the case of hydro, as electricity is the primary energy form selected, the primary energy equivalent is the physical energy content of the electricity generated in the plant, which amounts to assuming an efficiency of 100%."

Again my bold.

Policy and solutions / Re: Renewable Energy
« on: August 27, 2019, 10:35:11 AM »
For reference:

"The IEA had at a point used the “partial substitution method”, based on the assumption that hydro, wind, solar electricity had displaced thermal generation. This involved using an average thermal conversion efficiency (e.g. 36%) to back-compute their corresponding “primary energy equivalent”. This made their shares in the primary energy supply greater (around three times as much). However, the principle was abandoned as it relied on arbitrary conversion factors and was creating some transformation losses inside the energy balance that did not really exist."

My bold.

Policy and solutions / Re: Renewable Energy
« on: August 26, 2019, 08:54:25 PM »
Incidentally, the IEA used to assume a conversion efficiency of, I think, 36% for renewables, so that their numbers would be more directly comparable to those of fossil fuels and nuclear power. However, they decided that the conversion figure had no basis in any real conversion loses, and it created spurious losses in their overall energy balance. On the other hand, it means you can't use primary energy figures to accurately assess the contribution of renewables.

Even taking that into account, the contribution of renewables to overall useful energy is still quite small, but not as small as the tpes number implies. For example, hydro generates, globally, significantly more than nuclear, but on a primary energy basis it looks like less.

I believe BP still makes an adjustment to renewables to make them more comparable.

Policy and solutions / Re: Renewable Energy
« on: August 26, 2019, 04:30:44 PM »
Sure.It's a chart of primary energy. IEA considers primary energy of renewables to be electricity so it just converts twh to barrels of oil equivalent.. For nuclear it considers thermal energy to be primary energy, and it considers average efficiency of thermal power stations to be 33%, so it multiplies the twh before calculating BOE. For coal the primary energy is the chemical energy in the coal, so there's an additional loss.

Policy and solutions / Re: Renewable Energy
« on: August 26, 2019, 11:00:48 AM »
As no-one has volunteered an answer, I'll answer my own question. The order is coal,nuclear, hydro, wind, solar.

Policy and solutions / Re: Renewable Energy
« on: August 25, 2019, 10:58:36 PM »
Gerontocrat, I wasn't saying it was a realistic scenario. Just asking what the order of those energy sources would be in that scenario. Do you know the answer?

Edit. The point is that I think some people will be surprised by the answer.

Policy and solutions / Re: Tesla glory/failure
« on: August 24, 2019, 08:38:13 AM »
in spite of public transport being the quickest and most effective route to lower emissions,
I see that promoted a lot so let me throw some realities yor way.

London has the earliest underground network in the world…….London breaches its clean air commitment every year.  It used to be in the Autumn, now it is in the spring.  The reason is the sheer volume of FF vehicles coming into the city due to the sheer cost and congestion of public transport.

Neil, I'm totally in favour of EVs as well, and as I've said, I hope Tesla succeed. But all of the things you say about London don't change the fact that almost all forms of public transport have far lower emissions per person than cars and that even in Norway you only have under 10% of all cars on the road being electric at the moment. Because people hold on to their cars for 10-15 years, it takes a long time to replace all of them. Getting more people out of their cars and into buses/trains, and replacing diesel buses with electric buses (buses have a shorter lifespan than cars generally), is the quickest way to reduce emissions. Imagine London without any PT - it would be far worse. The reason that London has bad pollution is not that it has PT, it's that in spite of having an extensive PT network, people still use their cars far too much.

Arctic sea ice / Re: The 2019 melting season
« on: August 24, 2019, 08:28:21 AM »
This is the situation for basically all of today. Large amounts of heat being pulled in from the Baffin sea, the North Atlantic and to a lesser degree, Eastern Siberia.

Yes, with the cyclone ending up a bit further north, it may end up compacting the ice more on the Atlantic side, as well as bringing in warmer Atlantic waters, with persistent southerlies forecast for the coming days. Overall there's quite a strong reverse dipole.  It will be interesting to see exactly what's happening beneath the clouds, when the weather gods finally deign to give us a look.

Policy and solutions / Re: Renewable Energy
« on: August 24, 2019, 07:30:27 AM »
Various people have mentioned that using TPES is problematic, but I don't think the reason has been fully explained. To explain why I think the TPES graphs are misleading, I'll imagine a country where:

All space heating is provided by natural gas + electricity
All transport is fuelled by oil (petrol/diesel) + electricity
All industrial processes are Powered by electricity

As a result, coal, hydro, wind, nuclear and solar are only used to generate electricity.

The amount of electricity they generate is as follows:

Hydro: 100 TWh/year
Wind: 80 TWh/year
Solar: 60 TWh/year
Nuclear: 40 TWh/year
Coal: 35 TWh/year

Which of those would be shown as the biggest share/% on Gerontocrat's IEA graph for total primary energy? And which would be shown as the smallest? And what would their order be in size?

Arctic sea ice / Re: The 2019 melting season
« on: August 20, 2019, 08:33:26 AM »
The Euro is supporting GFS in predicting that the powerful cyclone forming in the CAA will move into the northern Beaufort on D4-5 and then gradually weaken as it moves over towards the Asian side of the basin. If this happens, it should promote further substantial area loss at the expense of extent, at least initially (ie in the D5-8 time frame).

Policy and solutions / Re: Tesla glory/failure
« on: August 18, 2019, 09:12:27 AM »
Blumen, I said on the renewables thread that it's reasonable to question Musk's motives, and you asked why. Here's my answer.

First, as I already said, I think it's reasonable to question anyone's motives, and I think it happens more than you give credit for. Oil executives, supermarket owners, bankers, etc. all get accused of having various nefarious plans quite regularly and by many people. Also Jobs, Gates, Bezos, etc.

Secondly, Musk presents himself as someone who wishes to save the planet through the transition to electric mobility and renewables. There's more reason to question someone's motivations if they're claiming to do something so big and outside their immediate  remit, in the sense that the legal purpose of a public company is to make money.

In addition, Musk has the personal carbon footprint of an African elephant , promotes individual over collective transport, in spite of public transport being the quickest and most effective route to lower emissions, promotes space travel... Personally I hope Tesla is successful, but I have a feeling that for musk it's more about him being the saviour of the planet than about saving the planet, but I may be wrong.

Anyway, I don't want to repeat the thousands of for and against arguments with respect to musk, just set out why questioning his motives seems reasonable to me.

Policy and solutions / Re: Renewable Energy
« on: August 18, 2019, 08:28:20 AM »
Dukes is the official source of uk energy stats. Renewables up fourfold over the same period.Total supply (incl.imports) down 8 percent since 2010.

Note that although imports are up, this is not because of a shortage of domestic supply. Uk often imports heavily when wind generation is high,  as prices are then low. Particularly at night when France has excess nuclear too. Uk holds capacity auctions to ensure sufficient supply to meet peak demand, essentially paying generators to remain in reserve. I believe this reserve has never actually been required in the years since the system started operating. Either way, demand at this time of year is way below peak (maybe 60% of peak?), so there was loads of spare capacity available. However, day to day demand is met through a market system, with a reserve to meet surges in demand plus more importantly sudden failures of power stations. Normally non-renewable power stations are a bigger problem in this regard, simply because they're bigger, so you lose more in one hit. However Hornsea is so big that it's more like a small thermal power station.

Clearly something went badly wrong on this occasion, but it really has nothing to do with a lack of potential supply.

Policy and solutions / Re: Renewable Energy
« on: August 17, 2019, 12:58:48 PM »
Blumen, personally I think it's reasonable to question anyone's motivations. But I don't think we should clog up this thread with arguments over musk. I'll answer more fully in one of the other threads when I have a chance.

Policy and solutions / Re: Renewable Energy
« on: August 17, 2019, 12:55:44 PM »
Terry, UK electricity demand has been falling for a number of years, not rising. Demand from evs is currently tiny and negligible in the grand scheme of things. Demand is low at this time of year and variable renewable generation was high. Hence your assumptions are incorrect in this case.

Policy and solutions / Re: Renewable Energy
« on: August 16, 2019, 01:23:51 PM »
Terry, I quite agree it's reasonable to ask questions about Musk's motivations, but EVs had absolutely zero to do with the recent blackout in the UK. That was related to two generators, one gas-fired and one wind-powered, being disconnected from the grid in quick succession, and the back-up systems not managing to respond quickly enough to restore frequency, resulting in "load shedding" - i.e. disconnecting a relatively limited number of customers. But demand was relatively low at the time, and wind generation (even after Hornsea disconnected) was relatively high for the time of the year. So it was some kind of technical failure in the systems of the National Grid and/or Distribution Network Operators (DNOs), the nature of which will no doubt become clearer in due course. But it wasn't due to EVs, and it wasn't because the people who run the grid in the UK believe that wind power has a load factor of 90%.

Arctic sea ice / Re: When will the Northwest Passage "open" in 2019?
« on: August 16, 2019, 12:12:26 PM »
Tall ships:

Basically they're large, traditionally-rigged sailing ships.

Policy and solutions / Re: Renewable Energy
« on: August 16, 2019, 10:46:46 AM »
Oren, I would be as baffled as you, except I know that some people aren't really looking at what happened, and trying to understand it, or for that matter at the actual figures for electricity demand from EVs. They have an angle, and they see this as a good excuse to push it. In addition to your valid points, I will add two things:

  • Wind generation was high at the time of blackout, and demand was low. There was a huge amount of slack in the system, but for whatever reason it wasn't possible to deploy it quickly enough. Possibly National Grid had cut corners on frequency response and spinning reserve to save money, possibly some freak event occurred.
  • Frequency was restored within about 15 minutes, and it took less than a couple of hours for the DNOs to restore all demand. The high level of disruption was mainly due to the impact on the railways. This kind of short interruption to the electricity supply to some customers happens all over the world from time to time, both in places with no renewables and in places with high levels of renewable penetration.

Jaxa extent now 4,768,552 km2, so moving into the territory that some people considered possible as a minimum.

I'm not yet (that) old, but I agree with Gero that in general people on ASIF create GIFs that are too fast. You end up having to watch them lots of times, and still don't get as clear an understanding of what's going on as you would if they were slower. Also support having the last frame slow/long, so that if the GIF is looping, it's clear what the final state is, and when the GIF starts/ends.

Arctic sea ice / Re: The 2019 melting season
« on: August 15, 2019, 10:18:23 AM »
All hinges now on bottom melt, and to a certain degree, on how much heat is pulled from depth by wind.

2019 has a lot of ocean heat "in the bank". With the winds that are forecast over the coming week, it will withdraw some of the heat from its savings account, and use it to melt the ice.

This will involve both northerlies pushing ice into warm waters (Beaufort, Fram), southerlies pushing warm water and warmish, humid air into the ice, and a bit of both at different times (Kara, Barents, Laptev, ESS). How much damage can that do at this late stage? Significant amounts of damage to volume, but how it will affect area and extent is harder to judge, and depends where the ice stops when the music (melt) stops.

Policy and solutions / Re: Renewable Energy
« on: August 13, 2019, 09:59:25 AM »
They're saying that for storage to be competitive for ensuring the 100% availability of a renewable-based grid, it would need to be far cheaper than for ensuring 95% availability. This is because you need to provide a disproportionate amount of extra storage to cover relatively rare events of low renewable energy generation. However, the good news is they ignored lots of other ways to help deal with those events, such as interconnectors, demand response, etc., so the real-world cost target would be higher (and hence more easily attainable).

Arctic sea ice / Re: 2019 vs 2012
« on: August 12, 2019, 09:41:34 AM »
SST update for 11 August 2012 vs 2019. The next few days will see warm, humid air and warm waters push north into the Laptev sector of the CAB. Meanwhile, northerlies will transport/export ice into the Chukchi, on one side of the Arctic, and into the Barents/Greenland seas on the other. I would expect area declines to pick up, but extent may hold up better initially. We could also see more areas of open water near the Pole as the ice is pushed apart.

Up half a bin to 3.5-4 million. I think the coming warmth and thin ice will keep us close to record territory, but most likely a little bit behind 2012.

Stuck with 3-3.5 million. Still think second place not too far behind 2012 is the most likely outcome.

Policy and solutions / Re: Renewable Energy
« on: August 08, 2019, 10:07:07 AM »
If by 2023 there still a lag of 40-50% from total needs....the 1.5oC is long gone...

Well, rboyd didn't include hydro, which could add another say 100-150 TWh. There's also likely to be some growth in nuclear. So that would leave you very close to break-even.

Obviously what happens in the future depends on lots of big and small decisions between now and then, particularly by governments/regulators, as well as technological developments, but there's no reason why renewables can't start to reduce demand for fossil fuels for electricity generation by around 2022-23. After that, they should cut into demand by increasing amounts year on year.

With greater support and a sense of urgency from governments around the world, their contribution could be massively increased. Doing more to improve energy efficiency would also make a big difference. I'm not saying we will get there, but we could do, if it were prioritised by governments and people/societies.

Policy and solutions / Re: Renewable Energy
« on: August 07, 2019, 05:26:10 PM »
Instead of using units of electricity growth per year, you should use percentage?

Not really for analysing absolute growth in renewables vs absolute growth in overall electricity consumption, where the idea was to look at whether all demand growth can be met by renewables. But we can certainly do a % analysis as well:

Annual growth in global electricity consumption 2008-2018 = 2.7%
Annual growth in non-hydro renewables 2008-2018 ~18% and 2017-2018 = 14.5%
Annual growth in hydro 2017-2018 = 3%

Assuming overall growth remains 2.7%, non-hydro remains 14.5% and hydro remains 3%, growth in hydro + non-hydro exceeds demand growth in 2022. In around 20 years from now, non-hydro + hydro cover all of the world's electricity needs. That's obviously unlikely to happen, but it gives an idea of the changes that would occur if current growth rates continue.

Policy and solutions / Re: Renewable Energy
« on: August 07, 2019, 01:49:16 PM »
Despite all the enthusiasm renewables are not even close to cover the growth of electricity generation, let alone replacing fossil fuels.

As I pointed out, they covered over 70% of typical growth in the last year. Isn't that close?

Policy and solutions / Re: Renewable Energy
« on: August 07, 2019, 01:48:24 PM »
...because we are still talking about small numbers.

But we're not talking about small numbers, are we? Just one year's growth in renewables was equivalent to 1.66% of total global electricity generation. That's a very big number - only slightly less than Germany uses in a year, and over 50% more than the UK uses. Clearly growth will slow at some point, but the fact that renewables are now the cheapest option in many places will help to sustain strong growth for many years to come.

Policy and solutions / Re: Renewable Energy
« on: August 07, 2019, 01:37:39 PM »
Well, he would say that, wouldn't he?  ;) Anyway, natural gas is better than coal, so if it replaces coal as a stop-gap measure, that may be a good thing, provided that it isn't used as an excuse to slow down the development of renewables.

Policy and solutions / Re: Renewable Energy
« on: August 07, 2019, 01:23:38 PM »
Why is it such a tall order? Renewables have grown much faster than that over the past 10 years. In 2008, non-hydro renewables generated around 400 TWh and they grew 50-60 TWh in 2009. Now they're growing at 300+ TWh/year, so 5-6 times higher.

And where does the "triple" come from, anyway? And over what time frame? Electrification is already taking place, but a lot of the increase in demand has so far been offset by greater energy efficiency. EVs may change that somewhat, but not so much as to prevent renewables overtaking demand growth.

Policy and solutions / Re: Renewable Energy
« on: August 07, 2019, 11:54:11 AM »
From BP statistical review of energy 2019:

Global electricity consumption 2008: 20433.3 TWh
Global electricity consumption 2018: 26614.8 TWh

Average growth: 618 TWh/year

Renewables excl. hydro 2017: 2166.5 TWh
Renewables excl. hydro 2018: 2480.4 TWh

Growth rate: 314 TWh/year

Hydro 2017: 4065.4
Hydro 2018: 4193.1

Growth rate: 128 TWh/year

Combined renewables growth: 442 TWH/year

Renewables covered 442/618=71.5% of average growth in global electricity consumption.

I've used the 10-year average in electricity consumption growth to reduce the noise. I'm only using the last year's growth rates for renewables because they're growing so quickly that the 10-average would massively understate the current situation.

Within a few years, it's likely that renewables will cover more than 100% of growth in demand, i.e. electricity generation from other sources will decline. Of course this doesn't deal with all of the other areas where fossil fuels are used, but it is much more than just some token effort.

Arctic sea ice / Re: The 2019 melting season
« on: August 07, 2019, 09:38:05 AM »
Area and extent continue to drop steadily, and open water is appearing all over the CAB, even though the weather has been nothing special over the past week or so. The forecast only turns nasty beyond D5, but the weak state of the ice and high SSTs means that we can expect above-average declines to continue.

Here's a comparison  between 29 July and 7 August, looking at an area located around 85N, 165-180W:

Arctic sea ice / Re: The 2019 melting season
« on: August 02, 2019, 11:42:38 AM »
- The Euro model predicts a pretty central moderate 975-980 hPa low by day 8, forecast will probably change. It would be bad if it happened not as central but shifted toward the ESS/Chuckchi.

I'm attaching the Euro forecast (first image) so people can easily see what you're talking about. On the other hand, the GFS has moved away from a deep low (second image).

Arctic sea ice / Re: The 2019 melting season
« on: August 02, 2019, 09:23:34 AM »
Still think the W. Beaufort may have ice outside of 80N at the minimum.

You mean E. Beaufort, presumably? It's possible, if more ice is transported from the CAB. I think what's already there will melt out, though. See the difference just one day makes:

Arctic sea ice / Re: The 2019 melting season
« on: August 01, 2019, 07:11:31 PM »
If you look closely at the area graphs, every sea is toast (at zero ice or soon to be) with the exception of the CAA and the CAB. This is where 2019 will fail to keep pace with 2012 and end up in 2nd place.

We'll see. I think second place is most likely, but I don't rule out first place. I think that once the surrounding seas melt out, the CAB will start to decline more quickly. How quickly? As for the CAA, the forecast isn't great, so it will continue to lose ice. I doubt it will match 2012.

Arctic sea ice / Re: The 2019 melting season
« on: August 01, 2019, 05:35:06 PM »
A couple of points in relation to CAB area/extent:

1. How far 2019 is behind depends on the numbers you're using. The Wipneus graphs show CAB area and extent near record low (see below). I do think we're a bit behind 2012, but not necessarily as far as the NSIDC figures suggest.

2. Normally the CAB starts melting from the Atlantic side, which is where we're behind this year. On the other hand, we're far ahead on the Pacific side. This means that the CAB will relatively soon be attacked from all sides, whereas normally it would take longer for open water to reach it on the Pacific side.

Edit: Part of the difference in the numbers is due to the difference in how the seas are defined, but that only emphasises that you can draw demarcation lines between the surrounding seas and CAB in different places in order to reach the conclusion you want to reach. I think the overall amount of ice is most relevant at this stage.

Arctic sea ice / Re: 2019 vs 2012
« on: August 01, 2019, 10:38:13 AM »
Taking KK's rankings and providing an inverse weighting (1st place gets 5 points, 2nd - 4, etc.), I get "How bad it is" weighted values:

Year   Weighted
2012     26
2016     27
2017     23
2018     18
2019     26

This makes 2019 look tied with 2012.  2016 'had the potential' but later faded.

Accepting KK's rankings, it's interesting that those results tie in with what actually happened. Correlation, but not necessarily causation. Incidentally, I'd say that 2019 is worse than 2012 in Greenland, and only clearly behind 2016, because although the ice front is slightly further south, there's much more heat in the adjoining waters. But these things are subjective, and in general KK's rankings look about right.

Arctic sea ice / Re: The 2019 melting season
« on: August 01, 2019, 10:22:37 AM »
The forecasts keep jumping around, with no clear pattern, but the general picture seems to be a mix of warm and cold anomalies, and of weak high and low pressure systems. In other words, neither very good nor very bad for the ice. Images attached are Euro 72-hour forecast.

The warmth over CAA over the next few days is worth watching, as is the renewed build-up of SSTs in the Laptev thanks to high pressure and clear skies.

Finally, at the speculative end of the forecasts, the Euro sees a fairly strong cyclone develop around D9, and the GFS goes Medieval on the ice over the period D8-15, with a powerful cyclone followed by a massive intrusion of heat from Siberia. Time will tell.

Arctic sea ice / Re: 2019 vs 2012
« on: July 30, 2019, 09:50:45 AM »
There's a lot of talk about average melt between now and the rest of the season. That's useful for keeping the discussion grounded in reality, but you also have to look at the current conditions:

SSTs - very important to bottom melt in the run-in of the season
volume/thickness - important for obvious reasons
current ice surface conditions/albedo - makes a huge difference to how much insolation is absorbed into the system
the weather forecast for the coming week

I would say all of these factors suggest above average melt between now and the minimum. Not necessarily equal to 2012, but almost certainly higher than usual.

For SSTs, last year Neven handily posted a comparison of conditions on 28 July for 4 recent years. I've added 2019. 2012 and 2016 both lost significantly more extent than normal between 28 July and minimum. 2017 and 2018 lost less. Which is 2019 most similar to?

Arctic sea ice / Re: 2019 vs 2012
« on: July 29, 2019, 06:44:44 PM »
One of the areas where 2012 had significantly less ice extent on this date is the eastern Beaufort. However, on closer comparison the situation is more nuanced, and arguably 2019 looks more likely to melt out further north. In the event, 2012 then experienced quite strong melt, whereas the forecast is less "favourable" this year, so we'll have to wait and see what happens.

Arctic sea ice / Re: The 2019 melting season
« on: July 29, 2019, 12:15:57 PM »
I'm attaching today's view of the area north of the Laptev bite (visible in the top left of the image), reaching as far north as 86N. The forecasts have this area being anomalously warm for the foreseeable future, even as the highs and lows move around the Arctic basin. As well as the many smallish polynyas, there is evidence of surface melting everywhere, and the ice looks in pretty bad shape. I think we'll lose quite a bit of it over the coming couple of weeks.

In fact, the next two weeks will be extremely interesting, because they will help to answer how much of an impact the GAC really had. Was the rapid melting mainly due to preconditioning, or would the ice have survived in the absence of the GAC? This time, with similarly preconditioned ice and warm SSTs, there will be more high pressure systems, clearer skies and warm anomalies.

Arctic sea ice / Re: The 2019 melting season
« on: July 25, 2019, 10:03:18 AM »
It has been commented, quite rightly, that the ice in Beaufort keeps being replenished with fresh ice, and is therefore melting out more slowly than it would otherwise do. In spite of that, the edge of the ice has retreated significantly over the past two weeks:

Arctic sea ice / Re: The 2019 melting season
« on: July 24, 2019, 12:18:54 PM »
Warm air is already entering the Beaufort/Chukchi margin, and by 72 hours the Euro has it covering most of the CAB and CAA (first image). The heat then intensifies and merges with heat coming from the Atlantic side (second image), with the "high" temperatures lasting for a good 4 days. Then there appear to be twin cyclones on the horizon, but a lot could change by then.

Arctic sea ice / Re: The 2019 melting season
« on: July 23, 2019, 12:40:59 PM »
Belated condolences, Neven (been away on holiday).

The last week exemplifies the importance of momentum. In spite of weather that was generally agreed to be favourable for ice retention, extent has continued to fall rapidly. A bit of the momentum has almost certainly been lost, but there's so much weak, thin ice that it's unlikely to slow things down much any time soon.

With the forecasts suggesting that we're about to return to a dipole, momentum will pick up again, with the ice in Beaufort, Lincoln, CAA and central CAB bearing the brunt of it. If the pattern holds for a while (and the forecast suggests it will), the first half of August will be very interesting.

Went for 3.25-3.75, but anywhere in the range 3-4 is reasonably likely, in my view.

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