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Messages - Ken Feldman

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501
Science / Re: The Science of Aerosols
« on: June 04, 2018, 08:58:30 PM »
Here's a 2015 study that shows the responses of three climate models to an idealized removal of all aerosols:

https://www.atmos-chem-phys.net/15/8201/2015/acp-15-8201-2015.pdf

Table 2 on page 8207 of that journal summarizes the results.  The formatting of the table doesn't translate, so here's an excerpt:

Emissions  Model           Temp Change (C)
SO2          HadGEM            0.838
SO2          ECHAM-HAM      0.831
SO2          NorESM             0.396
SO2          Mean                0.688

The effects for Organic Carbon was less warming (mean of 0.132) and for Black Carbon was slight cooling (mean of -0.044).

This is for the instantaneous removal of all anthropogenic aerosols, which won't happen (less than half of aerosols are now coming from utilities and industries).  And it doesn't include the responses from natural aerosols which may increase as a result of climate change.

So while the reduction of anthropogenic aerosols due to a decrease in fossil fuel burning may result in a slight increase in temperature, it probably will be far less than the 2 to 4 degrees I keep seeing people post in the ASI forums.

502
Science / Re: The Science of Aerosols
« on: June 04, 2018, 08:31:36 PM »
Jai,

I'm not finding any studies published in peer-reviewed journals that support a 2 - 4 degree increase in Arctic temperatures from removal of aerosols.  Please post links to your sources.

Here's another recent study that shows the impact of aerosols is much lower than previously reported:

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017JD027298

Here's the abstract:

Quote
Source attribution of Arctic sulfate and its radiative forcing due to aerosol‐radiation interactions (RFari) for 2010–2014 are quantified in this study using the Community Earth System Model equipped with an explicit sulfur source‐tagging technique. The model roughly reproduces the seasonal pattern of sulfate but has biases in simulating the magnitude of near‐surface concentrations and vertical distribution. Regions that have high emissions and/or are near/within the Arctic present relatively large contributions to Arctic sulfate burden, with the largest contribution from sources in East Asia (27%). Seasonal variations of the contribution to Arctic sulfate burden from remote sources are strongly influenced by meteorology. The mean RFari of anthropogenic sulfate offsets one third of the positive top of the atmosphere (TOA) RFari from black carbon. A 20% global reduction in anthropogenic SO2 emissions leads to a net Arctic TOA forcing increase of +0.019 W m−2. These results indicate that a joint reduction in BC and SO2 emissions could prevent at least some of the Arctic warming from any future SO2 emission reductions. Sulfate RFari efficiency calculations suggest that source regions with short transport pathways and meteorology favoring longer lifetimes are more efficient in influencing the Arctic sulfate RFari. Based on Arctic climate sensitivity factors, about −0.19 K of the Arctic surface temperature cooling is attributed to anthropogenic sulfate, with −0.05 K of that from sources in East Asia, relative to preindustrial conditions.

503
Science / Re: The Science of Aerosols
« on: June 01, 2018, 11:39:48 PM »
jai,

I don't have access to the full article, so don't know the answers to your questions.

There is another recent study (posted up thread) showing that the total removal of anthropogenic aerosols might increase global temperatures between 0.5 and 1.1 degrees C. Most global climate models have the arctic warming at twice (or a bit more) the global warming.  So if this study is showing only 0.7 degrees C of arctic warming, then maybe the increase from reducing pollution wont be as severe as the other study indicates.

504
The IEA is predicting that there will be about 125 million EVs by 2030:

https://www.cnbc.com/2018/05/30/electric-vehicles-will-grow-from-3-million-to-125-million-by-2030-iea.html

Quote
Electric vehicle (EV) ownership will balloon to about 125 million by 2030, spurred by policies that encourage drivers, fleets and municipalities to purchase clean-running cars, the policy advisor to energy-consuming nations forecast on Wednesday.

That marks a big jump from 2017, when the IEA estimated there were 3.1 million electric vehicles in use, up 54 percent from the previous year.

However, that's only a small fraction of the total number of cars:

Quote
IEA's outlook still leaves plenty of room for fossil fuel-powered vehicles. Forecasts put the world's total car count at roughly 2 billion somewhere in the 2035 to 2040 window.

However, the IEA also sees a pathway to 220 million electric vehicles by 2030, provided the world takes a more aggressive approach to fighting climate change and cutting emissions than currently planned.

505
Policy and solutions / Re: Coal
« on: June 01, 2018, 11:28:42 PM »
A new form of "clean coal" in the works?

https://www.forbes.com/sites/brighammccown/2018/05/31/could-clean-coal-actually-become-a-reality/2/#17fbdbe768bb

Some excerpts:

Quote
Through a process called chemical looping, researchers believe they have found a way to use coal without generating significant amounts of carbon dioxide (CO2). According to Dr. Liang-Shih Fan, distinguished university professor in Chemical and Biomolecular Engineering, he and his team have been able to use a process called coal-direct chemical looping to burn coal without emitting pollution.

Chemical looping burns fossil fuels and biomass in pressurized reactors without oxygen in the air. Metal oxide in the reactor provides oxygen for the combustion, which then “loops” the gases through different chambers, producing heat. At a basic level, the method burns oxygen, while holding onto carbon, and the heat generated during the combustion enables steam turbines to generate electricity. The process is capable of converting fuels into energy or other chemical products, while emitting less than one percent of the CO2 the fuels would otherwise produce.

And it even has a way of making the coal burning plants generate money from the byproducts of combustion:

Quote
To create value, the process not only converts fuels into energy, but can also create secondary products by recycling the byproducts of traditional power generation. What would otherwise be wasted can now be sold, potentially making the process more energy and financially efficient.

506
Science / Re: The Science of Aerosols
« on: June 01, 2018, 08:11:06 PM »
I posted this in one of the Arctic threads, it's also relevant to this discussion.

Article on the role of aerosols in the reduction of Arctic sea ice to date and the expected Arctic warming in the future:

https://journals.ametsoc.org/doi/10.1175/JCLI-D-17-0287.1

Abstract:

Quote
Observations show that the Arctic sea ice cover has been shrinking at an unprecedented rate since the 1970s. Even though the accumulation of greenhouse gases in the atmosphere has been closely linked with the loss of Arctic sea ice, the role of atmospheric aerosols in past and future Arctic climate change remains elusive. Using a state-of-the-art fully coupled climate model, the authors assess the equilibrium responses of the Arctic sea ice to the different aerosol emission scenarios and investigate the pathways by which aerosols impose their influence in the Arctic. These sensitivity experiments show that the impacts of aerosol perturbations on the pace of sea ice melt effectively modulate the ocean circulation and atmospheric feedbacks. Because of the contrasting evolutions of particulate pollution in the developed and developing countries since the 1970s, the opposite aerosol forcings from different midlatitude regions are nearly canceled out in the Arctic during the boreal summer, resulting in a muted aerosol effect on the recent sea ice changes. Consequently, the greenhouse forcing alone can largely explain the observed Arctic sea ice loss up to the present. In the next few decades, the projected alleviation of particulate pollution in the Northern Hemisphere can contribute up to 20% of the total Arctic sea ice loss and 0.7°C surface warming over the Arctic. The authors’ model simulations further show that aerosol microphysical effects on the Arctic clouds are the major component in the total aerosol radiative forcing over the Arctic. Compared to the aerosol-induced energy imbalance in lower latitudes outside the Arctic, the local radiative forcing by aerosol variations within the Arctic, due to either local emissions or long-range transports, is more efficient in determining the sea ice changes and Arctic climate change.

507
Arctic sea ice / Re: Arctic sea ice minimum early prediction
« on: May 31, 2018, 10:08:35 PM »

I am obliged to remind you that anthropogenic aerosols (air pollution/SO2) is currently cooling the arctic between 2 and 4C and preserving over 30% of total annual sea ice loss.

What is the source of this information?  It appears to be a gross overestimate of the amount of cooling from aerosols.

This paper from 2015 shows that the cooling effects of aerosols to be between 1.3 and 2.2 degrees C of cooling: http://www.nature.com/articles/518140e

Quote
Aerosols have a cooling effect by reflecting sunlight back into space. Mohammad Reza Najafi at the University of Victoria in Canada and his colleagues analysed nine climate models running from 1913 to 2012, comparing simulations with and without greenhouse gases, aerosols and other climate drivers. Their results show that aerosols have offset 1.3–2.2 °C of Arctic warming from greenhouse gases, limiting the observed warming to 1.2 °C. With aerosol emissions projected to drop in the coming decades, the rate of the warming is likely to increase.

And this paper from 2017 states that the projected reductions in anthropogenic aerosols will lead to a warming in the Arctic of 0.7 degrees C: https://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-17-0287.1

Quote
Observations show that the Arctic sea ice cover has been shrinking at an unprecedented rate since the 1970s. Even though the accumulation of greenhouse gases in the atmosphere has been closely linked with the loss of Arctic sea ice, the role of atmospheric aerosols in past and future Arctic climate change remains elusive. Using a state-of-the-art fully coupled climate model, the authors assess the equilibrium responses of the Arctic sea ice to the different aerosol emission scenarios and investigate the pathways by which aerosols impose their influence in the Arctic. These sensitivity experiments show that the impacts of aerosol perturbations on the pace of sea ice melt effectively modulate the ocean circulation and atmospheric feedbacks. Because of the contrasting evolutions of particulate pollution in the developed and developing countries since the 1970s, the opposite aerosol forcings from different midlatitude regions are nearly canceled out in the Arctic during the boreal summer, resulting in a muted aerosol effect on the recent sea ice changes. Consequently, the greenhouse forcing alone can largely explain the observed Arctic sea ice loss up to the present. In the next few decades, the projected alleviation of particulate pollution in the Northern Hemisphere can contribute up to 20% of the total Arctic sea ice loss and 0.7°C surface warming over the Arctic. The authors’ model simulations further show that aerosol microphysical effects on the Arctic clouds are the major component in the total aerosol radiative forcing over the Arctic. Compared to the aerosol-induced energy imbalance in lower latitudes outside the Arctic, the local radiative forcing by aerosol variations within the Arctic, due to either local emissions or long-range transports, is more efficient in determining the sea ice changes and Arctic climate change.

508
Policy and solutions / Re: Coal
« on: May 29, 2018, 07:29:48 PM »
I posted a link to this article in the renewables thread, but it has major implications for coal use too: https://www.bloomberg.com/view/articles/2018-05-20/storage-will-be-the-next-biggest-thing-in-energy

Here are the relevant sections for coal:

Quote
As a result, the cost of new-build renewables has been sinking. The highest-cost solar and wind projects in the U.S. will now produce electricity at least as cheaply as the lowest-cost coal plants, according to a report last year by Lazard Inc.

In Australia, that price differential means one of the world’s largest coal exporters is unlikely ever to build another generator powered by the stuff, Catherine Tanna, managing director of EnergyAustralia Pty, told a Bloomberg Invest conference in Sydney Wednesday. By the early 2020s, renewables will have gotten so cheap that it will be more cost effective to build them than to operate even an existing coal or nuclear plant, Jim Robo, CEO of Florida-based NextEra Energy Inc., said during an investor call in January.

509
Policy and solutions / Re: Renewable Energy
« on: May 29, 2018, 07:19:34 PM »
The economics of solar and wind are getting better and better.  This article has some very encouraging news:  https://www.bloomberg.com/view/articles/2018-05-20/storage-will-be-the-next-biggest-thing-in-energy

Some excerpts:

Quote
Unlike almost all their rivals in the energy-generation space, solar panels and wind turbines are mass-produced goods. That means they’re subject to the rules of continual improvement and falling costs that we see with semiconductors, household products and clothing as production volumes rise and factories undercut each other. Traditional power plants are essentially large-scale construction projects, which rarely achieve the same sorts of efficiency dividends.

As a result, the cost of new-build renewables has been sinking. The highest-cost solar and wind projects in the U.S. will now produce electricity at least as cheaply as the lowest-cost coal plants, according to a report last year by Lazard Inc.

Quote
By the early 2020s, renewables will have gotten so cheap that it will be more cost effective to build them than to operate even an existing coal or nuclear plant, Jim Robo, CEO of Florida-based NextEra Energy Inc., said during an investor call in January


510
Arctic sea ice / Re: The 2018 melting season
« on: May 25, 2018, 12:39:21 AM »
Beginning the analysis in 1979 is cherry picking. Why did we stop discussing the decades long increasing trend - leading up to 1979 - in Arctic sea ice extent? Noting that there's been a flat trend here for a decade is simply interesting in the moment. Does it perhaps suggest that we could be ending one cycle and beginning another? Also interesting that the Arctic sea ice volume is rather interesting in the moment.  http://ocean.dmi.dk/arctic/icethickness/thk.uk.php

One can toggle back - I just put May 23, 2008 side by side with yesterday's ice thickness - interesting.

 Graph was in the 1990 IPCC report.

Seems to me that the cherry pick is to go back to the 1990 report.  The most recent IPCC report was published in 2013.  Here is the comparable graphic from the current report:

http://www.climatechange2013.org/images/figures/WGI_AR5_Fig4-3.jpg

There is no "decades long increasing trend" that you refer to.  Interestly, after 1990 (you left all of that data off in your post), the trend is clearly downward.

511
Arctic sea ice / Re: Latest PIOMAS update (May mid-monthly update)
« on: May 22, 2018, 10:15:19 PM »
I believe the 3 meter thick ice north of Laptev modeled by PIOMAS is far thinner. Any guesses as to why? Remaining fragments of thick MYI  frozen in a thinner sheet causing ULS and/or CryoSat to overestimate due to lack of necessary resolution?

Ridging and rafting during the refreeze season can cause ice to grow much thicker than the 2 meters or so it would get just from the cold weather.

See this website for more information about how sea ice forms:  https://nsidc.org/cryosphere/seaice/characteristics/formation.html

Here's an excerpt that explains ridging and rafting:

Quote
If the ocean is rough, the frazil crystals accumulate into slushy circular disks, called pancakes or pancake ice, because of their shape. A signature feature of pancake ice is raised edges or ridges on the perimeter, caused by the pancakes bumping into each other from the ocean waves. If the motion is strong enough, rafting occurs. If the ice is thick enough, ridging occurs, where the sea ice bends or fractures and piles on top of itself, forming lines of ridges on the surface. Each ridge has a corresponding structure, called a keel, that forms on the underside of the ice. Particularly in the Arctic, ridges up to 20 meters (60 feet) thick can form when thick ice deforms. Eventually, the pancakes cement together and consolidate into a coherent ice sheet. Unlike the congelation process, sheet ice formed from consolidated pancakes has a rough bottom surface.

512
Policy and solutions / Re: Coal
« on: May 11, 2018, 10:16:06 PM »
Of course they are.  :(

DOE looking 'very closely' at Cold War-era law to boost coal, nuclear production
http://thehill.com/policy/energy-environment/386891-doe-looking-very-closely-at-using-cold-war-era-law-to-boost-coal

It's amazing how quickly they abandon the "free market" philosophy when their political interests are threatened.  Meanwhile, here's how their efforts have gone so far:


https://oilprice.com/Alternative-Energy/Renewable-Energy/Coal-Is-Losing-Ground-Despite-Trumps-Promises.html

Quote
So, the demise of coal is merely a matter of time, and it seems unstoppable despite efforts by the Department of Energy to support the crumbling segment. The latest here was Secretary of Energy Rick Perry’s call for modular coal projects “that provide stable power generation with operational flexibility, high efficiency, and low emissions.”

Stability of power generation was what kept coal going in the face of oncoming—still expensive at the time—renewables traffic. But then the shale revolution unearthed billions upon billions of cubic feet of cheap natural gas—this was the beginning of the end for coal. What’s more, gas has the additional attraction of lower carbon emissions, even though the U.S. emissions total has not changed much as gas replaces coal because of the sheer amount of new gas capacity that is being brought online.

Now renewables are becoming cheaper, too, and energy storage is about to solve the problem of intermittent solar and wind generation, leaving coal on the ropes it would seem. The EIA in its latest Short-Term Energy Outlook forecasts that coal production will fall by 3 percent to 751 million tons this year as a result of a 4-percent decline in local demand, most of it coming from the power generation sector. But exports will also decline, by 9 percent.

The demise of coal is slow, but it seems unstoppable. There is just nothing working for coal, except perhaps clean coal technologies, which are, alas, too expensive for the time being to have a chance at competing with gas and renewables.

513
Policy and solutions / Re: Coal
« on: May 11, 2018, 10:09:36 PM »
Every time they update the estimates of the number of coal plants that will be retired over the next decade, the number increases.  Here's the latest: https://www.forbes.com/sites/jeffmcmahon/2018/05/09/coal-collapsing-faster-under-trump-wind-solar-gas-to-benefit/#15be95235ee4

Quote
“The real story I believe is in coal retirements," said Bruce Hamilton, a director in the energy practice at Navigant, which has modeled every coal plant in the U.S. and projected 73 gigawatts will retire in the next 10 years.

"That’s more than twice what we projected last year at this time. It’s more than we had two years ago when the Clean Power Plan was in the assumptions."

The projection changed in part because of more announced retirements, Hamilton said, "but more importantly, the fundamentals of the economics of coal have gotten worse, with costs going up, while the competition for coal—that is, gas, wind and solar—has all gotten cheaper. So it’s getting to the point where huge swings are forecast. You can see it will be throughout the decade."


514
Policy and solutions / Re: Nuclear Power
« on: May 10, 2018, 06:28:04 PM »
The big problem for nuclear is that there's no price on carbon emissions.  So nuclear's big advantage (carbon free power) is negated.

Due to cost, utilities are building wind, solar and natural gas power plants in free market economies.  A few nukes have been started in Europe and the US, but the cost has skyrocketed after construction started and the inevitable construction delays have occurred.  With the cost of renewables and natural gas plants coming down, it remains to be seen if those plants will be completed.

In a few countries with State controlled economies (China and the mid-east), new nukes are being ordered.  With cheap labor they can be somewhat competitive, but even in semi-free market economies like India, nukes are being priced out.

In the US, when a nuke needs major repairs, more often than not the utility will shut it down as other options have become cheaper.

Gen IV plants may come online before nuclear fusion plants are commercially viable.  Place your bets!

TLDR:  Too cheap to meter has become too expensive too matter.

515
Policy and solutions / Re: Coal
« on: May 09, 2018, 09:53:17 PM »
Renewabes are now cheaper than coal in India:

https://qz.com/1272394/cheap-solar-and-wind-energy-prices-are-killing-indias-coal-power-plants/

Quote
Over the last year, wind and solar power tariffs have fallen to a record low of around Rs2.4 per unit, much lower than the average of Rs3.7 per unit at which analysts say coal-based power is currently being sold on India’s power exchanges.

As a result, coal-based power plants are falling out of favour with power distribution companies (discoms).

“The (coal-based power) plants are ready but… no discom was coming forward for long-term PPAs (power purchase agreements) because they were getting power at a cheaper rate from renewable sources,” Sudhir Kumar, associate director at CARE Ratings, told Quartz.

Last financial year, for the first time, India added more power capacity from renewable sources than coal.

516
Consequences / Re: Ice-free Arctic
« on: April 18, 2018, 07:08:08 PM »
I still think we underestimate the influence of volcanoes on our climate. They are completely unpredictable but can have massive impact on our climate.

A few VEI7 or an VEI8 and we can throw all our climate models into the garbage.

Overall, I think the impact of volcanoes on past climate is not very well researched and many unknowns remain.

I'll agree with you that super large volcanic eruptions (VEI8) would have a very large impact on the climate and that we need to study them more.  Even large volcanic eruptions (VEI7) can have a long term (by human standards) effect on the climate.  It's now thought that increased volcanic activity in the 1300s and 1400s started the "little ice age".

And if there are a few VEI 8 eruptions, we won't be worrying about climate modeling, the few survivors on the globe will be too busy scrounging for food!  Fortunately, VEI 8 eruptions are very rare, happening about 30 million years apart.

Pinatubo was a VEI 5.  Krakatau was a VEI 6.  The Yellowstone eruptions were VEI 7, happening a few 100,000 years apart with the most recent about 650,000 years ago.

We have good measurements of the gases emitted by volcanoes and know that they are a small fraction of what humans emit.  Volcanoes emit between 180 million tons and 440 million tons of carbon dioxide per year, depending on the amount of volcanic activity.  Human emissions are on the order of 45 billion tons per year. 

In fact, we've increased the CO2 content of the atmosphere by almost 100 ppm since we started measuring it about 60 years ago, and the rate of increase is increasing to more than 20 ppm per decade.  We can see the effects of this right now and they are projected to get much worse before the end of this century.

So I think worrying about AGW and what we can do to reduce our emissions is a bit higher priority than worrying about the next VEI 7 eruption which is probably hundreds of thousands of years in the future.

517
Arctic sea ice / Re: The 2018 melting season
« on: April 13, 2018, 09:03:01 PM »

The paper linked shows Bering avg inflows increased 50% from the 00s to 2014.. I would guess we have seen a similar year over year increase between 2017->2018 (or larger) due to the lack of sea ice. HYCOM's SSS maps clearly show the push, I would not be shocked if this yr surpassed 2-2.5Sv.

In a follow on paper (abstract available here: https://www.sciencedirect.com/science/article/pii/S0079661117302215?via%3Dihub), the authors indicate that the increase in flow was a maximum of 1.2 Sv in 2014.  They state that the data shows a long term increase of 0.01 Sv per year.  So 2 to 2.5 Sv would seem outside of the realm of possibility.

Quote
Year-round in situ Bering Strait mooring data (1990–2015) document a long-term increase (∼0.01 Sv/yr) in the annual mean transport of Pacific waters into the Arctic. Between 2002 and 2015, all annual mean transports (except 2005 and 2012) are greater than the previously accepted climatology (∼0.8 Sv). The record-length maximum (2014: 1.2 ± 0.1 Sv) is 70% higher than the record-length minimum (2001: 0.7 ± 0.1 Sv)

The flows also seem to be dominated by pressure differences between the Pacific and the Arctic, not winds, so the absence of ice a month earlier than normal wouldn't have much influence over the flows.

Quote
By separating the flow into portions driven by (a) the local wind and (b) a far-field (Pacific-Arctic “pressure-head”) forcing, we find the increase in the Bering Strait throughflow is primarily due to a strong increase in the far-field forcing, not changes in the wind.

518
Arctic sea ice / Re: The 2018 melting season
« on: April 13, 2018, 07:38:48 PM »
I've been pondering the Bering for a while now this season.  The change in potential is like giving a "kick" to a pendulum, which has less meaningful impact now, but unknown but possibly dangerous ones later in the season.

I have three questions I will be trying to answer as we continue.
1) How will this heat and early open extent affect weather.
2) How much will escape to the Chukchi and how soon.
3) What cascade may take place as a result of the first two events.

Some basic info about flow of water from the Bering Sea to the Arctic in this presentation:

http://psc.apl.washington.edu/HLD/Bstrait/Woodgate_AONSeattleNov2015_17thNov2015.pdf

The linked presentation provides the results of 25 years (1990 to 2015) of monitoring flows through the Bering Strait.  Flows from the Pacific into the Arctic are on the order of about 1 Sv which is 1/3 to 1/5 the average flows across the Fram Strait.  The strait is usually ice covered from January through April, so the area opened a little earlier this year, but still has some ice in it.  I'm not sure this is going to have a large impact on the rest of the melt season.  I think, as 2007 and 2012, it will come down to the May melt ponds and the amount of ice exported across the Fram.

Here's a paper on the southern Bering Sea:  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5619787/

It's seasonally ice covered as described below:

Quote
The eastern Bering Sea is ice-free during the summer and much of the fall. Sea ice usually begins to form on the northern shelf in December, with strong, frigid northerly winds both opening polynyas where sea ice forms and advecting the ice southward [5]. The leading edge melts, cooling and freshening the water column. Typically, ice appears on the southern shelf in January, reaches a maximum in February or March, and is gone by mid-May [6]. In cold years, sea ice advances more than 1000 km from the Bering Strait (66°N) to the Alaskan Peninsula, while in warmer years, ice remains north of 58°N.

Historically, the southeastern Bering Sea has been characterized by high year-to-year variability in sea-ice extent in March and April [7]. This high variability was interrupted in 2001 by a five-year period of low (almost nonexistent on the southern shelf) sea-ice extent and warm ocean temperatures (2001–2005). To improve understanding of how long-term warming can impact this ecosystem, a major study (Bering Sea Project, http://www.nprb.org/bering-sea-project) was designed to explore this ecosystem from 2007 to 2010. Because of the historical record of high inter-annual variability, it was expected that at least one of the project years would also support warmer (less sea ice) conditions. Unfortunately for the Bering Sea Project, the warm period of 2001–2005 was followed by a period of extensive sea ice during spring and cold ocean temperatures over the entire eastern shelf (2007–2012) [7,8]. During the intermediate year, 2006, some ice was observed on the southern shelf and ocean temperatures were near normal.
 

519
Policy and solutions / Re: Nuclear Power
« on: April 13, 2018, 06:54:18 PM »
Quote
I believe Canada has a few reactors that have, or had been running for many decades, possibly in excess of 60 years?
Canadian reactors actually have had terribly short lives before having to be shutdown for refurbishment. Candu refurbishment seems to take tons of money and many years. I think the Bruce reactors took 18 years of refurbishment. Point Lepreau needed 4 years of refurbishment after running for about 10 years and needed refurbishment again in less than 10 years.

The newer reactors in Ontario have a better record - they require major refurbishment at closer to 30 years of age. The Darlington refurbishment is planned to run from 2016-2026.

Funny how capacity factors for nukes never count the many years of shutdown they need for maintenance.

I don't know about the Candu reactors, but US reactors average 90% capacity factors because they only refuel once every two years and schedule the major maintenance during the refueling shutdown.

https://www.forbes.com/sites/jamesconca/2015/05/11/when-should-a-nuclear-power-plant-be-refueled/#161525c93d95

Quote

An outage usually takes only 40 days, so once every two years means the plant operates just under 100% of the time – 98% in the case of this nuclear plant. When Columbia Generating Station starts up again at the end of June it will produce even more electricity, more efficiently and more reliably.

...

There are many other reasons to shut down a power plant - for maintenance, repair and replacing components - but if everything is running perfectly, you can do all of those things during the occasional refueling outage.

During the outage, more accurate ultrasonic instruments will be installed for measuring the water flow through the reactor core, producing more electricity and saving water. A new Power Range Neutron Monitoring system will be installed for better fuel use, replacing analog circuit controls with more reliable and redundant digital controls. In addition, three new 175-ton power transformers will be installed.

The benefits of these improvements will allow for a more efficient use of nuclear fuel, an increase in the overall efficiency of reactor operations, and increased equipment reliability.

A refueling outage is also very good for all the other businesses in the area. For this refueling, 1,500 new out-of-town workers will descend upon the plant to supplement the 1,100 permanent Energy Northwest employees, something that local businesses look forward to with every outage (NEI).

The outage will replace 248 of the plant’s 764 nuclear fuel assemblies (see figure). Fuel is replaced after being in the core for six years, so every two years a third of the fuel is replaced and the other two thirds are moved around to make for even burning.

Many smaller maintenance projects will occur at the same time - 13,000 separate tasks in only six weeks. Sawatzke says, “The team has worked hard and we are well prepared and ready to execute.”

If the past is any clue to the future, this outage will go smoothly and on schedule, returning this super-efficient power plant to operation in time for the Fourth of July.



520
Policy and solutions / Re: Renewable Energy
« on: April 13, 2018, 06:04:14 PM »
Good story on renewables with battery storage here:  https://oilprice.com/Energy/Energy-General/The-Supersized-Future-Of-Energy-Storage.html

An excerpt (note the part I bolded):

Quote
... Another project, however, is not: A British billionaire is building a 120 MW/140 MWh installation not far from Tesla’s installation in Australia.

Sanjeev Gupta, owner of Australian steelworks Whyalla, is building the battery to use both as storage for electricity produced by a solar farm, and in construction at the steelworks site. What we’re seeing there is likely just the beginning of ever-bigger battery storage systems that will accompany every large-scale solar or wind project.

A recent Moody’s report on energy storage supports this forecast. It found that investors are getting more and more interested in energy storage projects as their commercial viability improves. Moody’s calculated that a kWh of electricity from a battery storage installation currently costs around US$0.133. That’s based on a price of US$400 per kWh of storage (a high-price estimate) for a fully installed system divided by 3,000 charge/recharge cycles per battery over a lifetime of 10 years.

Now, Moody’s notes that this cost per kWh is still higher than conventional electricity, but adds that things are changing fast as batteries become cheaper and cheaper, so soon we may actually have renewable electricity that costs less than the output of fossil fuels power plants.

There is the question of battery life spans, of course, when compared to the life span of the average gas-fired power plant. Also, there are some unique challenges, Moody’s vice president and senior credit officer Rick Donner said in the report, especially with regard to operating risks. Still Donner said, on the whole, battery storage projects carry the same risks as conventional power generation projects.

Costs are falling, in the meantime. Moody’s estimates that by 2020-2022, the cost per kWh of storage will drop to US$100. This will make even bigger projects than Crimson viable. If things continue moving in the same direction as they have been for the last decade, it won’t be long before a 100 MW storage system becomes the lower end of renewable storage capacity.

521
Policy and solutions / Re: Nuclear Power
« on: April 12, 2018, 08:38:38 PM »
In the article I linked to above, it linked to a more detailed report available here:  http://esi.nus.edu.sg/docs/default-source/esi-bulletins/esibulletinvol10-issue-6-(1).pdf?sfvrsn=2)

The report has about two pages on the recent past failures to commercialize SMRs.  Here are the relevant paragraphs:

Quote
There is a further hurdle to be overcome before these large numbers of SMRs can be built. For a company to invest in a factory to manufacture reactors, it would have to be confident that there is a market for them. This has not been the case and hence no company has invested large sums of its own money to commercialise SMRs. An example is the Westinghouse Electric Company, which worked on two SMR designs, and tried to get funding from the U.S. Department of Energy (DOE). When it failed in that effort, Westinghouse stopped working on SMRs and decided to focus its efforts on marketing the AP1000 reactor and the decommissioning business. Explaining this decision, Danny Roderick, then president and CEO of Westinghouse, announced: “The problem I have with SMRs is not the technology, it’s not the deployment -- it’s that there’s no customers... The worst thing to do is get ahead of the market”.4

Given this state of affairs, it should not be surprising that no SMR has been commercialised. Timelines have been routinely set back. In 2001, for example, a DOE report on prevalent SMR designs concluded that “the most technically mature small modular reactor (SMR) designs and concepts have the potential to be economical and could be made available for deployment before the end of the decade, provided that certain technical and licensing issues are addressed”. Nothing of that sort happened; there is no SMR design available for deployment in the United States so far.

Similar delays have been experienced in other countries too. In Russia, the first SMR that is expected to be deployed is the KLT-40S, which is based on the design of reactors used in the small fleet of nuclear-powered icebreakers that Russia has operated for decades. This programme, too, has been delayed by more than a decade and the estimated costs have ballooned.5

South Korea even licensed an SMR for construction in 2012 but no utility has been interested in constructing one, most likely because of the realisation that the reactor is too expensive on a per-unit generating-capacity basis. Even the World Nuclear Association stated: “KAERI planned to build a 90 MWe demonstration plant to operate from 2017, but this is not practical or economic in South Korea” (my emphasis). Likewise, China’s plans for constructing a series of High Temperature Reactors (HTR-PM) appear to have been cancelled, in part because the cost of generating electricity at these is significantly higher than the generation cost at standard-sized light water reactors.

The final paragraph in that article states:

Quote
Meanwhile, other sources of electricity supply, in particular combinations of renewables and storage technologies such as batteries, are fast becoming cheaper. It is likely that they will become cheap enough to produce reliable and affordable electricity, even for these remote and small communities never mind larger, grid-connected areas, well before SMRs are deployable, let alone economically competitive.

522
Policy and solutions / Re: Nuclear Power
« on: April 12, 2018, 08:23:55 PM »
There are also people who think SMRs wont be commercially viable:

https://www.greentechmedia.com/articles/read/interest-in-small-modular-nuclear-grows#gs.6semL=g

Quote
In the December 2017 edition of the National University of Singapore’s Energy Studies Institute Bulletin, for example, Canadian academic Professor M.V. Ramana provided a detailed argument for why SMRs could never be a viable technology.

Nuclear plants in general require high levels of capital, he noted, and high construction costs mean the electricity they provide ends up being more expensive than coal, gas and, more recently, wind andsolar 

SMRs may be able to overcome the first problem, said Ramana, who is a professor at the University of British Columbia's School of Public Policy and Global Affairs.

But SMRs could end up with even higher energy costs because the smaller reactors can't take advantage of economies of scale unless they're manufactured “by the thousands, even under very optimistic assumptions about rates of learning.”

Experience indicates such rates of learning may be rare in the nuclear industry. In France and the U.S., according to Ramana, reactor construction costs have historically risen rather than falling.

Also, mass production would need the industry to settle on a single SMR design. As of 2016 there were 48 listed by the International Atomic Energy Agency.

Finally, said Ramana, for all the interest in SMRs, no country has yet got behind the technology enough for it to be commercialized. This likely indicates demand for the reactors is not as solid as proponents imagine.

523
Policy and solutions / Re: Nuclear Power
« on: April 12, 2018, 08:18:45 PM »
NuScale Power is hoping to have a set of 12 50 MW SMRs operational in Utah 2026.  They need additional investors though.

https://www.bloomberg.com/news/articles/2018-04-10/first-small-scale-nuclear-reactor-may-be-just-eight-years-away

Quote
NuScale Power LLC, which is leading global efforts to build a so-called small modular reactor, is seeking as much as $120 million in equity investment to accelerate design of a matching power generator. The company has already spent more than $700 million, and has “hundreds of millions of dollars more to spend,” Chief Financial Officer Jay Surina said in an interview on the sidelines of the Bloomberg New Energy Finance Future of Energy Summit in New York.

“We could use another investor or two,” he said. Backed by Fluor Corp., NuScale is casting a wide net that includes “deep-pocketed individual investors,” Surina said, noting it’s “too early yet for private equity.”

524
Policy and solutions / Re: Nuclear Power
« on: April 12, 2018, 06:51:16 PM »
To get back on-topic again: It's been a long time since I looked into GenIV nuclear, about 10 years or so, when I concluded that it was the only acceptable form of nuclear. I remembered that I really liked the aspect of scalability, ie that smaller, mobile modules could be built for residential areas, etc (I believe Toshiba was working on that). Can someone give me a brief update on how far has the technology progressed since then?

And likewise for Bob Wallace's question: How will Gen-future nuclear be able to close the very large price gap between nuclear and wind/solar enough to get nuclear back into the game?

Gen IV nuclear is still in the developmental stage.  In the US, deployment is still 10 to 15 years away: 
Quote
Accordingly, the Department has provided substantial support to the development of light water-cooled SMRs, which are under licensing review by the Nuclear Regulatory Commission (NRC) and will likely be deployed in the next 10-15 years.

ref: https://www.energy.gov/ne/nuclear-reactor-technologies/small-modular-nuclear-reactors

There is also a Generation IV International Forum (GIF) looking at six different potential Gen IV reactor types.  In December 2017, the GIF stated:

Quote
At least four of the systems have significant operating experience already in most respects of their design, which provides a good basis for further R&D and is likely to mean that they can be in commercial operation before 2030.

More info here: http://www.world-nuclear.org/information-library/nuclear-fuel-cycle/nuclear-power-reactors/generation-iv-nuclear-reactors.aspx

Given the rapid decrease in prices for solar, wind and batteries, I doubt that Gen IV reactors will be deployed before they become priced out of the market.

525
Policy and solutions / Re: Oil and Gas Issues
« on: April 11, 2018, 11:29:13 PM »
This is a potentially very big decision if upheld: PA court challenges the rule of capture:

http://www.ehn.org/pennsylvania-fracking-trespassing-2555983611.html

sidd

Whoa!  It's worth reading that article.

Basically, someone with natural gas on their property didn't want to sell the mineral rights, so the extraction company set up a well on an adjacent property and did a horizontal well, fracced the shale, and took the gas without paying the property owner that didn't sell the mineral rights!  And the lower court upheld it as  legal.  It was overturned at the state superior court.

526
Policy and solutions / Re: Nuclear Power
« on: April 10, 2018, 07:51:40 PM »
Two new reactors for the Turkey Point site near Homestead, FL: https://weather.com/news/news/2018-04-09-turkey-point-nuclear-reactor-expansion-homestead

Quote
On Thursday, the U.S. Nuclear Regulatory Commission (NRC) approved a pair of new reactors at the Turkey Point Nuclear Generating Station, which is owned by Florida Power & Light, the Palm Beach Post reported. If the reactors are built, they could cost as much as $21.8 billion and wouldn't be ready until at least 2031, the report added.
 
In a 2014 investigation, weather.com and the Huffington Post identified the Turkey Point plant as one of the eight U.S. power plants most vulnerable to flooding from sea level rise by the end of the century. It showed that in worst-case projections, nearly all of the plant could be flooded by a tropical system in 2033, if current sea level rise projections materialize.

I'm surprised that anyone is even proposing to build new nukes in the US after the Westinghouse bankruptcy.  If the current estimated cost is $21.8 billion, the probably cost will be over $40 billion.  And with the rapid growth of renewables and battery storage, does anyone think that there will be a need for these plants in the 2030s?

527
Policy and solutions / Re: Aviation
« on: April 10, 2018, 07:42:30 PM »
Battery powered commuter planes could be operational on regional air routes up to 650 miles by 2021.  Story here: https://www.fastcompany.com/40549048/world-changing-ideas-transportation-eviation-alice-commuter



Quote
In five years, if you want to take a trip from San Francisco to San Diego, it may be possible to do it on a small electric plane–and with a ticket that costs less than driving or taking the train. The Israel-based startup Eviation, which is building a new all-electric, nine-seat airplane, called the Alice Commuter expects to begin making its first commercial flights in 2021 and scale up to hundreds of routes across the U.S. over the next few years.

528
Policy and solutions / Re: Renewable Energy
« on: April 06, 2018, 01:53:40 AM »
More money was invested in solar in 2017 than in any other energy technology.  Story here:  https://oilprice.com/Alternative-Energy/Solar-Energy/Solar-Attracted-More-Investment-Than-Any-Technology-In-2017.html

From the story:

Quote
The proportion of world electricity generated by wind, solar, biomass and waste-to-energy, geothermal, marine and small hydro in 2017 was 12.1 percent (up from 5.2 percent in 2007).

Since 2004, the world has invested $2.9 trillion in these green energy sources.

Falling costs for solar electricity, and to some extent wind power, is continuing to drive deployment, the study claims. Last year was the eighth in a row in which global investment in renewables exceeded $200 billion — and since 2004, the world has invested $2.9 trillion in these green energy sources.

529
Policy and solutions / Re: Renewable Energy
« on: April 05, 2018, 06:42:46 PM »
Solar power’s greatest challenge was discovered 10 years ago. It looks like a duck.

https://www.vox.com/energy-and-environment/2018/3/20/17128478/solar-duck-curve-nrel-researcher

Quote
Back in 2008, a group of researchers at the National Renewable Energy Laboratory (NREL) noticed a funny-looking shape in their modeling.

They were starting to take solar photovoltaic (PV) panels seriously, running projections of what might happen if PV were deployed at scale. They noticed that large-scale deployment had a peculiar effect on the electricity “load curve,” the shape that electricity demand takes throughout the day.

That's  a variation on the "sun doesn't always shine, wind doesn't always blow" argument.  The solution is the same, storage.  From the article you linked:

Quote
The holy grail: affordable energy storage

David Roberts

It is frequently argued that a system based on wind and solar will need an enormous amount of storage — not just hourly, but daily or even seasonal storage — and that batteries aren’t up to the task. So we’ll either have to limit the scale of renewables or find some other cheap, large-scale, long-term storage. What’s your take?

Paul Denholm

We spend a huge amount of time talking about this topic here around the lunch table — a lot of calories are spent on it. So I’ll tell you what I’d say is the informal general consensus about ultra-high-penetration renewables scenarios.

The consensus is emerging that we can probably do 80 percent [renewables] with some combination of spatial diversity and short-duration storage.

We can deal with diurnal shifts with short-duration storage, and not too much of it. When we did our Renewable Electricity Future study back in 2012, we got up to 80 percent renewables with only about 100 GW of additional storage. It’s not that much.

In the US, we currently get about 19% of our electricity from nuclear and 5% from hydro-power, so we could go carbon free with battery storage, some of which could come from smart electric vehicle charging.

530
Policy and solutions / Re: Renewable Energy
« on: April 05, 2018, 06:25:07 PM »
Those numbers are quite a bit higher than what Lazard puts out, across the board. I wonder where their methodology differs.

Regardless, the consilience is a good thing.

They're using Leveled? Cost of Energy (LCOE), which takes into account the capacity factor and the operating and maintenance costs.  The previous numbers were the bid cost of installing the systems.

531
Arctic sea ice / Re: Abrupt sea ice loss
« on: April 05, 2018, 06:03:54 PM »
Over at the Ice Free Arctic  thread Ken Feldman posted this

Quote
A 2011 study estimated that the albedo effect of an ice-free arctic for a month in late summer would increase from the current forcing of 0.11 watts per meter squared (W/m-2) to 0.30 W/m-2.  Using current estimates of climate sensitivity, that would lead to a global temperature increase of 0.15 degrees C. Here's the abstract from the study:

https://forum.arctic-sea-ice.net/index.php/topic,1886.msg145111.html#msg145111


So if the ice is gone for the last month of every year, over ten years the world is more than 1C warmer. I imagine that's where the number comes from.

That said, those calculations use local and temporal forcing changes and apply them to global yearly forcing changes. That misses the whole point. That global, annual .15C become several degrees at the local level of the Arctic. That's significant because it delays the onset of the freezing season.

It's 0.15C total, not an additional 0.15C every year.  Don't forget the planck (or blackbody) feedback, which is that the temperature increase leads to more heat being shed into space.

However, over time, that 0.3 W/m-2 (about a month of nearly ice free conditions) eventually grows to 0.7 W/m-2 (the whole spring and summer ice-free) as the Arctic continues to lose ice earlier during the summer, allowing for the Arctic Ocean to warm more.  Other studies have shown that it will take decades to go from the first nearly ice free September to the whole summer being ice free.

532
Policy and solutions / Re: Renewable Energy
« on: April 04, 2018, 06:29:51 PM »
We're nearing the tipping point now.  This article is on the Oilprice.com blog:  https://oilprice.com/Alternative-Energy/Renewable-Energy/Renewables-Are-Closing-In-On-Fossil-Fuels.html

Quote
However, the economics are pretty dire for fossil fuels. The LCOE for onshore wind currently stands at about $55 per megawatt-hour (MWh), which is a global comprehensive average that incorporates equipment, construction, financing, operating and maintenance costs, and average run time. That cost is down 18 percent from the first six months of 2017, an impressive and significant decline.

Solar LCOE costs without tracking comes in at $70/MWh, which is also down 18 percent from the first half of 2017.

These averages obscure some truly low-cost wind and solar potential in certain parts of the world. BNEF says that onshore wind in India averages $39/MWh, down by nearly half from 2017. Solar PV in India only costs $41/MWh. That compares favorably to the $68/MWh for coal and $93/MWh for natural gas. In fact, clean energy is cheaper than coal and gas in both China and India.

The analysis was done by Bloomberg New Energy Finance for a report here: https://about.bnef.com/blog/tumbling-costs-wind-solar-batteries-squeezing-fossil-fuels/

With sources like Bloomberg and Oilprice.com reporting that renewables plus storage are cheaper than new fossil plants, I think the transformation of the energy supply from fossil fuels to renewables is finally on the launch pad.  Investors are going to be putting their money into renewables and batteries, not fossil fuels.  There aren't going to be many new fossil fuel plants built in the future and a lot will be prematurely retired due to their operating costs.

533
Consequences / Re: Ice-free Arctic
« on: March 31, 2018, 12:54:49 AM »
Quote
The thickness maps show ice 3 to 4 meters thick in areas north of 80N

That's mostly due to multiyear ice accumulating yearly excess ice.

I'll ask again, because you are making it sound like temperatures don't matter for ice formation, when I believe it is the major component of ice formation. Yet you are not saying it straight up, you are simply dancing around it. I'm very confused.

To your understanding, does it matter how cold it gets or is it simply enough to reach the minimum freezing point? If it does matter, what percentage of the ice is made through bottom growth and what percentage is made by snow/rain/ridging.

Both are important, but ridging and rafting is obviously capable of adding more thickness than thermodynamic processes.  This is from a site on the Antartic sea ice, but the physical processes are the same:

Quote
Analysis of the pack shows that deformation, rather than basal freezing, is the dominant mechanism for increasing ice thickness beyond 0.2-0.4 m. This results in an increase in local ice thickness whilst at the same time opening leads where, during the growth season, new ice is able to form. The net effect is increased ice production resulting in an increase in the total mass of ice within the pack, and subsequent changes in the ice thickness distribution.
 

Here's a link to the site:  http://aspect.antarctica.gov.au/home/about-sea-ice/ridging-and-rafting

And here's a follow-up to the paper on storms in the North Atlantic helping the ice to grow:

Quote
As the Arctic sea ice cover continues to thin, convergent sea ice motion can more readily pile up ice into large ridges. Such ridges can be hazardous to marine activities in the Arctic. Divergent ice motion produces openings in the ice called leads, where new ice can readily grow. Winds are the main driver for both ridging and lead formation. A single storm event can lead to significant redistribution of sea ice mass through ridging and new leads. As part of the Norwegian Young Sea ICE (N-ICE2015) expedition, colleagues at the Norwegian Polar Institute made detailed sea ice thickness and ice drift observations before and after a storm in an area north of Svalbard (Figure 5). Results showed that about 1.3 percent of the level sea ice volume was pressed together into ridges. Combined with new ice formation in leads, the overall ice volume increased by 0.5 percent. While this is a small number, sea ice in the North Atlantic is typically impacted by 10 to 20 storms each winter, which could account for 5 to 10 percent of ice volume each year.
  The source for that story is the NSIDC website at this link: http://nsidc.org/arcticseaicenews/2018/02/




534
Policy and solutions / Re: Renewable Energy
« on: March 30, 2018, 09:17:53 PM »
Another article on how solar and wind are becoming (and in some cases, already have become) cheaper than coal and gas:  https://thinkprogress.org/solar-wind-power-prices-are-beating-natural-gas-c9912054400c/

Quote
Prices for solar, wind, and battery storage are dropping so rapidly that renewables are increasingly squeezing out all forms of fossil fuel power, including natural gas.

The cost of new solar plants dropped 20 percent over the past 12 months, while onshore wind prices dropped 12 percent, according to the latest Bloomberg New Energy Finance (BNEF) report. Since 2010, the prices for lithium-ion batteries — crucial to energy storage — have plummeted a stunning 79 percent (see chart).

535
Consequences / Re: Ice-free Arctic
« on: March 30, 2018, 08:51:24 PM »
Quote
This statement is incorrect.  Ice formation is a binary function of below freezing and not below freezing.  Once seawater gets below the freezing point, -1.8 C, ice crystals will form.  It's basic physics.

Are you arguing that temperatures have no significant bearing on ice formation rate?

Quote
After that, sea ice thickness is determined by other factors, including wind and snow.  Wind and snow help thicken the ice sheet.  The wind by allowing more heat to dissipate through the ice, and snow by weighing down the ice and allowing more snow ice to form.

Woosh. Most ice formation is due to bottom growth. That growth is completely dependent on the gradient of temperature of the water with the atmosphere. The colder it is the larger the gradient producing more ice.

Of course, snow and frozen rain do add to the total but that number is much smaller than bottom growth.

Quote
Snow also helps to protect the ice during the melt season through it's higer albedo.  Here's a link to a paper about observations of snow on ice during the 2015 spring:


Did you even read that abstract to the end? Read the last sentence.

Quote
So a few degrees of warming during the winter, provided that the temperatures stay below freezing (resulting in new ice crystals forming in leads and snow falling on that ice), don't prevent new ice from forming.  That's why models predict that the Arctic will become a seasonal ice sheet (similar to Antarctica or the Sea of Okhotsk), not ice free all year.

Sure a few degrees will of course result in almost unnoticeable effects but the warmer it gets the less growth you get through bottom melt.

The thickness maps show ice 3 to 4 meters thick in areas north of 80N, where the temperatures have been been warmer in winter.  So I'm arguing that the effects of rafting, ridging and snow ice formation can offset the slower bottom growth from the above average temperatures and delay the complete melt out of the Arctic ice.  These mechanisms will also allow the Arctic ice the reform in winters after it eventually goes ice-free in summers, becoming a seasonal ice sheet, like the Antarctic sea ice.

And I did read the entire article, not just the abstract.  With more storms, you get more snow on the thinner ice.  That leads to more snow-ice formation and the protective albedo effect.  From the discussion section of the article that explains the last sentence of the abstract (emphasis added):

Quote
Mean precipitation from 1980 to 2016 shows the highest precipitation in the Atlantic sector of the Arctic (Figure S2b). This region is characterized by a larger number of autumn and winter storm events (Graham, Rinke, et al., 2017; Graham, Cohen, et al., 2017; Rinke et al., 2017; Woods & Caballero, 2016; Zhang et al., 2004). This is largely due to the influence of North Atlantic Ocean. High precipitation in this region is supported by the deep (>50 cm) snowpacks observed in this region during spring field campaigns in 2015 (Merkouriadi, Gallet, Graham, et al., 2017) and 2017 (M. Granskog; M. Nicolaus, personal communication, 2017). Given the recent observations of thicker snow cover and thinning of the ice cover in the Atlantic sector
of the Arctic (Renner et al., 2014; Rösel, Divine, et al., 2016; Rösel, Polashenski, et al., 2016), we surmise the potential for snow-ice formation in this region is the largest in the Arctic Ocean but can become imminent in larger areas when the ice is thinning.

In autumn and winter of 2014–2015, frequent storm events brought heavy precipitation and positive air temperature anomalies to our study region (Figures 1a and 1b). These storms are also associated with sustained 6-hourly wind speeds above 10 m s1, according to the ERA-I reanalysis (Merkouriadi, Gallet, Graham, et al., 2017). These strong winds initially come from the south and advect warm and moist air from the North Atlantic into the Central Arctic, resulting in heavy precipitation and positive temperature anomalies (Cohen et al., 2017; Kayser et al., 2017; Woods & Caballero, 2016). It is clear from our results that these storm events, and associated precipitation and temperature changes, play a crucial role in the growth, development, and structure of FYI. The impact of these storms in relation to the growth onset of FYI needs to be considered in sea ice modeling studies.

536
Consequences / Re: Ice-free Arctic
« on: March 30, 2018, 06:06:04 PM »
What I want you to understand is that ice formation is not a binary function "below freezing", "not below freezing". Ice formation speeds up the colder it is. FDD's as illustrated by Tealight show how Arctic winter temperatures increased over time.

This statement is incorrect.  Ice formation is a binary function of below freezing and not below freezing.  Once seawater gets below the freezing point, -1.8 C, ice crystals will form.  It's basic physics.

After that, sea ice thickness is determined by other factors, including wind and snow.  Wind and snow help thicken the ice sheet.  The wind by allowing more heat to dissipate through the ice, and snow by weighing down the ice and allowing more snow ice to form.

Snow also helps to protect the ice during the melt season through it's higer albedo.  Here's a link to a paper about observations of snow on ice during the 2015 spring:  https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2017GL075494

From the introduction of the paper: 
Quote
Snow on sea ice is a critical physical parameter that modulates the growth and decay of sea ice (Maykut, 1978; Sturm & Massom, 2010). In spring, when solar insolation is high, even little snow fall on Arctic sea ice can significantly slow down surface melt, due to the snow’s high albedo (Perovich et al., 2017). In winter, when sea ice grows in the absence of solar insolation in the high Arctic, the role of snow is twofold. Snow insulates the sea ice surface from cold air temperatures, hindering thermodynamic growth of sea ice (Ledley, 1991; Maykut, 1978). However, snow can also contribute to the sea ice mass balance through the formation of snow-ice (e.g., Leppäranta, 1983). Snow-ice forms when seawater floods and refreezes at the ice/snow interface, due to excessive snow load that pushes the ice surface below sea level. Snow-ice is a common process in seasonally ice-covered seas but has not been prevalent in the Arctic, where thick perennial sea ice has dominated (Sturm & Massom, 2010).

So a few degrees of warming during the winter, provided that the temperatures stay below freezing (resulting in new ice crystals forming in leads and snow falling on that ice), don't prevent new ice from forming.  That's why models predict that the Arctic will become a seasonal ice sheet (similar to Antarctica or the Sea of Okhotsk), not ice free all year.

537
Consequences / Re: Ice-free Arctic
« on: March 30, 2018, 01:23:38 AM »
Quote
It just might be because even as "warm" as the previous winters have been, they haven't come close to reaching the melt point of ice:

The thermodynamic ice thickness growth rate is a function of time and temperature. The metric used to calculate that function is the Freezing Degree Day. You can read about it here:

 https://nsidc.org/cryosphere/seaice/processes/thermodynamic_growth.html

 Tealight has a nice set of graphs describing FDD behavior over the last several years here:

https://sites.google.com/site/cryospherecomputing/fdd

Quote
Volume has increased despite the warmer winters:

Do you mean 2017/2018 volume increased relative to 2016/2017? Of course. See the FDD graphs above. 2016/17 was the warmest winter on record, so it follows that that it had a very low volume gain. Luckily, 2017 had the second smallest volume loss since 2014. That left the volume minimum in a good position to overtake 2017/2018 even if it was almost as warm.

2017/2018 my yet surprise. If the Bering situation results in a chukchi/beufort/ess situation, Volume Maximum might reach record low.

Tealight's graphs seem to undercalculate the thickness of the ice.  Compare the graph, which calculates a current ice thickness of 150 cm to the map showing the current ice thickness:

Tealight's graph.

Current ice thickness and volume from DMI

It seems that the simple formula leaves out a lot of real life situations.  Here's what NSIDC says on the page you linked: 
Quote
The ice thickness increases at a rate roughly proportional to the square root of the cumulative FDD. Formulas such as this are empirical, meaning they are calculated only with observed data, so they really are simplifications of the ice growth processes. The formulas assume that the ice growth occurs in calm water and is reasonably consistent, and they do not take into account sea ice motion, snow cover, and other surface conditions.

NSIDC has a good page summarizing how sea ice forms.  Here's a link:https://nsidc.org/cryosphere/seaice/characteristics/formation.html

The wind and waves can cause forming ice sheets to raft over each other (becoming thicker) and crash into each other, forming ridges. From the link above:

Quote
If the ocean is rough, the frazil crystals accumulate into slushy circular disks, called pancakes or pancake ice, because of their shape. A signature feature of pancake ice is raised edges or ridges on the perimeter, caused by the pancakes bumping into each other from the ocean waves. If the motion is strong enough, rafting occurs. If the ice is thick enough, ridging occurs, where the sea ice bends or fractures and piles on top of itself, forming lines of ridges on the surface. Each ridge has a corresponding structure, called a keel, that forms on the underside of the ice. Particularly in the Arctic, ridges up to 20 meters (60 feet) thick can form when thick ice deforms.

538
Consequences / Re: Ice-free Arctic
« on: March 29, 2018, 07:37:33 PM »
Quote
The sea ice extent in 2012 bottomed out at 3.39 million square kilometers.  In 2013 the minimum was 5.05 million square kilometers.

The 2012-2013 freezing season had the record volume gain at the time at 19.063 x 1000km^2. Then it lost 17.04 during the melting season for a total volume gain of 1.79, year over year. In that cycle the Arctic grew. The 2013-2014 freezing season was much weaker at 17.726 but the melting season was the weakest since 2007 for a net year over year gain of 1.42.

In both years the gains exceeded the losses thus we had two years in a row of volume growth. But only in one of those years was record gains obtained.

Both 2016 and 2017 had similarly low volumes but they only gained 17.031. For both seasons winter temperatures remained highly anomalously warm for the whole season.

Volume has increased despite the warmer winters:



It just might be because even as "warm" as the previous winters have been, they haven't come close to reaching the melt point of ice:


539
Consequences / Re: Ice-free Arctic
« on: March 28, 2018, 11:41:04 PM »
My assumptions justifying thinking the gulf stream will find its way into the arctic ocean.

1. A BOE will let the stratification of the arctic ocean be disrupted by wave action.

2. when the sun sets and things cool off with the stratification a thing of the past you get bottom water production rather than ice.

3. what drives the currents around Greenland and the CAA currently is the Earth's rotation the warmth coming up from the equator (gulf stream) and the large freshwater input from ice melt and run off.

4. it is the cold reduced salinity run off water plus ocean water surface water current that pushes the gulf stream away from the east coat of north America.

The freshwater mixes with surface water, if that becomes bottom water then the surface water needs to be replaced.  The cold water would sink rather than stay on the surface.  So instead of a current coming out of the arctic ocean past Greenland you would have a current going in instead.

No current pushing the gulf stream east.  So it would go north into the arctic ocean.

With 20C water coming into the arctic basin you could see 20C air temps over the water and storms like there was no tomorrow.

Climate models show that a slow down of the Gulf Stream (actually the Atlantic Meriodonal Overturning Current, or AMOC) is more likely due to global warming.  There's a good summary of it here:  https://e360.yale.edu/features/will_climate_change_jam_the_global_ocean_conveyor_belt

Quote
A huge amount of heat is moved around our planet by a single ocean current system — the Atlantic Meridional Overturning Circulation (AMOC) — which accounts for up to a quarter of the planet’s heat flux. The system is driven by density: waters that are cold or salty are denser and so dive down to the ocean floor. As a result, today, cold waters sink in the North Atlantic and flow southwards, while warm tropical waters at the surface flow northwards in the Gulf Stream, making northern Europe unusually mild for its latitude. But if northern waters get too warm, or too fresh from melting ice, then they can stop being dense enough to sink. That causes a major traffic jam for the water attempting to move north, and the system grinds to a halt.

...

If the North Atlantic current slows dramatically, then the entire Northern Hemisphere would cool; a complete collapse of the current could even reverse global warming for about 20 years. But the heat that ocean currents fail to transport northwards would make parts of the Southern Hemisphere even hotter. And a cooler north isn’t necessarily good news. Should the AMOC shut down, models show that changes in rainfall patterns would dry up Europe’s rivers, and North America’s entire Eastern Seaboard could see an additional 30 inches of sea level rise as the backed-up currents pile water up on East Coast shores.

540
Consequences / Re: Ice-free Arctic
« on: March 28, 2018, 11:27:58 PM »
I don't care if an article is peer reviewed. It it contradicts my perception of reality I'll challenge it. This models predicts extraordinary growth that no one has ever witnessed before.

 I'll tell you exactly the mistake of the model.

The model assumes that after November, Arctic temperatures return to average. The average temps remain average even while generating record ice growth until April.

That's the opposite of the observations. So far the surface temperature anomalies last until April and ice has not grown at the incredible rate required by this model. There is something seriously wrong with it. The part of my reply that you didn't address explains why, let me repeat their assumption:

Quote
For SAT a large positive anomaly occurs between October and February after the initial perturbation, with a peak of almost 11 K in November (Figure 2). After February, there are no further SAT anomalies stronger than natural variability.

We are already at 5-8 K winter anomaly that last until April.  Yet you want me believe that after the first BOE all that extra heat will be vented out to of the arctic system? That makes no sense.

The record low ice extent to date was in 2012.  Here's how the 80N temperatures responded (note the below average temperatures in February):



The sea ice extent in 2012 bottomed out at 3.39 million square kilometers.  In 2013 the minimum was 5.05 million square kilometers.  So somehow, 1.66 million square kilometers of exceedingly thin first year ice survived.

541
Arctic sea ice / Re: Abrupt sea ice loss
« on: March 28, 2018, 06:33:58 PM »
It's important to read how they run the simulations in the models.  Here's what they did in the paper above:

Quote
The loss of Arctic sea ice during the whole year that we examine here only occurs under the large radiative forcing of the RCP8.5 simulations. In these simulations, the CO2 concentration is prescribed and shows an accelerating increase until the year 2100 (implying a radiative forcing from well-mixed greenhouse gases of 8.5 W m−2), followed by a stabilization period with a decelerating increase (Meinshausen et al. 2011). In the year 2250, the CO2 concentration reaches its final level of almost 2000 ppm.

If we continue on a high emissions path as described by the paragraph above, loss of the winter Arctic sea ice will be the least of our worries.  Note that the current goals of international agreements are to stabilize concentrations at 450 ppm and that some organizations are work toward an eventual reduction to 350 ppm by studying ways to take CO2 out of the atmosphere and sequester it.

542
Consequences / Re: Ice-free Arctic
« on: March 28, 2018, 12:00:14 AM »
Quote
After the first BOE, the ice will struggle to return.

I've pasted links and excerpts of several peer-reviewed scientific papers that refute this argument.  Do you have any peer-reviewed studies that support it?

Why would the Arctic behave differently than other bodies of water that melt out and then refreeze seasonally?  It's much colder and in the dark much longer than they are.

543
Consequences / Re: Ice-free Arctic
« on: March 23, 2018, 10:21:30 PM »
Quote
...  because chances are I'm wrong about an irreversible state change

I'm glad you're open to new information.  Here's something you may be happy to read:

https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-14-00654.1

Abstract: 
Quote
Record lows in Arctic sea ice extent have been making frequent headlines in recent years. The change in
albedo when sea ice is replaced by open water introduces a nonlinearity that has sparked an ongoing debate
about the stability of the Arctic sea ice cover and the possibility of Arctic ‘‘tipping points.’’ Previous studies
identified instabilities for a shrinking ice cover in two types of idealized climate models: (i) annual-mean
latitudinally varying diffusive energy balance models (EBMs) and (ii) seasonally varying single-column
models (SCMs). The instabilities in these low-order models stand in contrast with results from comprehensive
global climate models (GCMs), which typically do not simulate any such instability. To help bridge
the gap between low-order models and GCMs, an idealized model is developed that includes both latitudinal
and seasonal variations. The model reduces to a standard EBM or SCM as limiting cases in the parameter
space, thus reconciling the two previous lines of research. It is found that the stability of the ice cover vastly
increases with the inclusion of spatial communication via meridional heat transport or a seasonal cycle in
solar forcing, being most stable when both are included. If the associated parameters are set to values that
correspond to the current climate, the ice retreat is reversible and there is no instability when the climate is
warmed. The two parameters have to be reduced by at least a factor of 3 for instability to occur. This implies
that the sea ice cover may be substantially more stable than has been suggested in previous idealized
modeling studies.

Here's a plain language summary of the article: https://scripps.ucsd.edu/news/research-highlight-arctic-sea-ice-loss-likely-be-reversible

Quote
Research Highlight: Arctic Sea Ice Loss Likely To Be Reversible
   
Scenarios of a sea ice tipping point leading to a permanently ice-free Arctic Ocean were based on oversimplified arguments

New research by Till Wagner and Ian Eisenman, scientists at Scripps Institution of Oceanography, UC San Diego, resolves a long-running debate over irreversible Arctic sea ice loss.

Ever since the striking record minimum Arctic sea ice extent in 2007, the ominous scenario of a sea ice tipping point has been a fixture in the public debate surrounding man-made climate change and a contingency for which Arctic-bordering countries have prepared.

For decades, scientists have been concerned about such a point of no return, beyond which sea ice loss is irreversible. This concern was supported by mathematical models of the key physical processes (known as process models) that were believed to drive sea ice changes. The process models forecasted that increased global warming would push the Arctic into an unstoppable cascade of melting that ceases only when the ocean becomes ice-free.

...

Wagner and Eisenman resolve this discrepancy in the study in an upcoming Journal of Climate article,  “How Climate Model Complexity Influences Sea Ice Stability.”

They created a model that bridged the gap between the process models and the GCMs, and they used it to determine what caused sea ice tipping points to occur in some models but not in others.

“We found that two key physical processes, which were often overlooked in previous process models, were actually essential for accurately describing whether sea ice loss is reversible,” said Eisenman, a professor of climate dynamics at Scripps Oceanography. “One relates to how heat moves from the tropics to the poles and the other is associated with the seasonal cycle. None of the relevant previous process modeling studies had included both of these factors, which led them to spuriously identify a tipping point that did not correspond to the real world.”

“Our results show that the basis for a sea ice tipping point doesn’t hold up when these additional processes are considered,” said Wagner. “In other words, no tipping point is likely to devour what’s left of the Arctic summer sea ice. So if global warming does soon melt all the Arctic sea ice, at least we can expect to get it back if we somehow manage to cool the planet back down again.”

544
Consequences / Re: Ice-free Arctic
« on: March 23, 2018, 10:04:56 PM »
One of the weaknesses with just projecting from recent trends is that the natural variability inherent in the climate system could be missed.  For example, it's estimated that the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO) both influence the transport of heat from the tropics to the Arctic.  Recent studies estimate that natural variability is responsible for 30% to 50% of the recent losses in Arctic sea ice are due to natural variability.

Some studies are showing that the AMO is shifting from a positive phase, as it has been since the 1990s, to a negative phase.  During a positive phase of the AMO, more warm Atlantic water is transported to the Arctic than during a negative phase.  This could lead to a slow-down in the loss rates of the Arctic sea ice, which wouldn't be captured by projecting trends.

Here's an article explaining the link between the AMO and Arctic sea ice:  http://adsabs.harvard.edu/abs/2016EGUGA..18.1978D

Here's the abstract:
Quote
The Arctic and North Atlantic have experienced pronounced changes over the 20th and early 21st centuries, including a rapid loss of Arctic sea ice over the last several decades, prominent multidecadal variability in both ocean temperatures and sea ice, and decadal-scale change in tropical storm activity. We use suites of coupled climate model simulations to probe some of the factors responsible for the observed multidecadal variability in the Atlantic/Arctic system. In our models we show that multidecadal fluctuations of the North Atlantic Oscillation (NAO) induce multidecadal fluctuations of the Atlantic Meridional Overturning Circulation (AMOC). A positive phase of the NAO is associated with strengthened westerly winds over the North Atlantic. These winds extract more heat than normal from the subpolar ocean, thereby increasing upper ocean density, deepwater formation, and the strength of the AMOC and associated poleward ocean heat transport. In model simulations the observed negative phase of the NAO in the 1960s and 1970s led to a weaker than normal AMOC, reduced poleward ocean heat transport, a cold North Atlantic, and an increase in Arctic sea ice extent in both winter and summer. The NAO strengthened from the 1970s to the mid 1990s, leading to an increase of the AMOC and a warming of the North Atlantic. The increased heat transport extended throughout the North Atlantic, into the Barents Sea, and finally into the Arctic, contributing to a rapid reduction of sea ice in the 1990s through the 2000s. Feedbacks involving shortwave radiation are an important component of the overall changes. The NAO-induced AMOC increase also led to hemispheric-scale atmospheric circulation changes and increased Atlantic hurricane activity, as well as atmospheric teleconnections to the Southern Ocean. Since the mid 1990s the strong positive phase of the NAO has weakened to a more neutral phase. Climate projections for the next decade that take into account recent behavior of the NAO as well as anthropogenic radiative forcing suggest a weakening of the AMOC and associated ocean heat transport, which would tend to moderate the rate of Arctic sea ice loss over the next decade. This effect is superimposed on the persistent and growing effects of anthropogenic climate change.

And here's another article about the possibility of a slow down in the sea ice loss: http://www.pnas.org/content/112/15/4570

Abstract: 
Quote
Satellite observations reveal a substantial decline in September Arctic sea ice extent since 1979, which has played a leading role in the observed recent Arctic surface warming and has often been attributed, in large part, to the increase in greenhouse gases. However, the most rapid decline occurred during the recent global warming hiatus period. Previous studies are often focused on a single mechanism for changes and variations of summer Arctic sea ice extent, and many are based on short observational records. The key players for summer Arctic sea ice extent variability at multidecadal/centennial time scales and their contributions to the observed summer Arctic sea ice decline are not well understood. Here a multiple regression model is developed for the first time, to the author’s knowledge, to provide a framework to quantify the contributions of three key predictors (Atlantic/Pacific heat transport into the Arctic, and Arctic Dipole) to the internal low-frequency variability of Summer Arctic sea ice extent, using a 3,600-y-long control climate model simulation. The results suggest that changes in these key predictors could have contributed substantially to the observed summer Arctic sea ice decline. If the ocean heat transport into the Arctic were to weaken in the near future due to internal variability, there might be a hiatus in the decline of September Arctic sea ice. The modeling results also suggest that at multidecadal/centennial time scales, variations in the atmosphere heat transport across the Arctic Circle are forced by anticorrelated variations in the Atlantic heat transport into the Arctic.

None of this is to deny the impact of greenhouse gas emissions and the warming climate.  If we don't reduce are emissions and lower the concentrations in the atmosphere, the Arctic will eventually become ice free.  It's just a question of how soon.

545
Consequences / Re: Ice-free Arctic
« on: March 23, 2018, 09:43:02 PM »
Here's a good article on the sensitivity of trend analysis with Arctic sea ice:  http://www.mdpi.com/2072-4292/10/2/230

Here's an extract from the article:
Quote
Using an inter-calibrated satellite sea ice product, this article examines the sensitivity of decadal trends of Arctic sea ice extent and statistical projections of the first occurrence of an ice-free Arctic summer. The projection based on the linear trend of the last 20 years of data places the first Arctic ice-free summer year at 2036, 12 years earlier compared to that of the trend over the last 30 years. The results from a sensitivity analysis of six commonly used curve-fitting models show that the projected timings of the first Arctic ice-free summer year tend to be earlier for exponential, Gompertz, quadratic, and linear with lag fittings, and later for linear and log fittings. Projections of the first Arctic ice-free summer year by all six statistical models appear to converge to the 2037 ± 6 timeframe, with a spread of 17 years, and the earliest first ice-free Arctic summer year at 2031.


546
Arctic sea ice / Re: The 2018 melting season
« on: March 23, 2018, 07:55:42 PM »
A bit off topic (apologies!) but can anyone point me to a good site for the Gulf Stream and changes over time in the Gulf stream?

There's a good overview at carbon brief, link here:https://www.carbonbrief.org/the-atlantic-conveyor-belt-and-climate-10-years-of-the-rapid-project

Here's a link to the RAPID project, which measures the Atlantic current at 26N:  http://www.rapid.ac.uk/background.php

Here's a picture from the site of the flows from the first decade of the Rapid project:


547
Consequences / Re: Ice-free Arctic
« on: March 21, 2018, 11:15:03 PM »
First let me be very clear. Your post and my post are talking about two very different things.

you talked about:

When will the Arctic be sea ice free in the summer for the first time?

I talked about:

What happens after the first ice free Arctic, if anything?


There are some short-term negative feedbacks that occur after the ice melts out.  This article describes them: http://pubman.mpdl.mpg.de/pubman/item/escidoc:2461121/component/escidoc:2461125/PAGESmagazine_2017_14-19_Notz.pdf

Here's an excerpt:

Quote
Annual variability: The importance of negative
feedbacks
In addition to seasonal forecasts on time scales of a few
months, also forecasts on time scales of a few years
have made some headlines over the past decade. These
headlines were usually related to claims that the Arctic
would lose its remaining summer sea ice within just a few
years. The underlying reasoning of such claims was often
related to a discussion of a possible ’tipping point’ that is
related to the ice-albedo feedback. Given the substantial
loss of Arctic sea ice in the past few years, the ocean
could potentially absorb enough heat to rapidly melt the
remainder of the sea ice cover.
However, our current understanding of the Arctic climate
system strongly suggests that this reasoning is unrealistic.
A first indication for this finding derived from model
experiments in which all Arctic sea ice was synthetically
removed from the Arctic Ocean at the onset of summer,
thus maximising the possible ice-albedo feedback
(Tietsche et al., 2011). Despite such maximised feedback,
the ice cover recovered in these experiments within
just a few years. This is because on annual time scales,
negative feedbacks dominate the evolution of the Arctic
sea ice cover. Three negative feedbacks are particularly
important: First, the open ocean very effectively releases
its heat to the atmosphere during winter, causing a rapid
loss of much of the heat that was accumulated in the icefree
water during summer. Second, the thin ice that forms
during winter can grow much more rapidly than ice that
survived the summer, because heat can more effectively
be transported from the ocean to the atmosphere when
the ice cover is thin (Bitz and Roe, 2004). Third, as ice
forms later in the season, it will carry a thinner insolating
snow cover as any snow fall occurring before ice
formation simply falls into the open ocean (Notz, 2009).

548
Policy and solutions / Re: Seaweed Farming
« on: March 09, 2018, 10:43:24 PM »
How about including seashells as well in a new and broader title with even more focus on CO2 drawdown:

Seaweed and seashell farming

Good suggestion.  I made the change.

549
Consequences / Re: Ice-free Arctic
« on: March 09, 2018, 10:27:16 PM »

I post a response.  Initially, the ice will regrow and then melt again in summer.


Yes, but:

 1. Initial conditions in October will be very different from initial conditions of the past. To begin with there won be a giant slab of ice keeping the waves down and the humidity locked in the oceans. The water will be very warm from all the incoming radiation. The atmosphere will be very warm too.

2. Before ice can form all the extra heat and humidity must be vented and the waves calmed. That means that refreezing will begin late and from 0.

3. Winter temperatures are already crashing. After A BOE Arctic growth is bound to be anemic.

4. Come the melting season of the following year the ice will be thinner than ever, with a record low extent.

5. This means that the year following  the first ice-free year will be ice free again but much sooner, gathering more heat than ever.

6. See 1.

Quote
Eventually, if the Arctic warms enough, the Arctic will be ice free for more and more of the year.


Yep

Quote
However, when the Arctic cools, the ice will grow back.


And there is not reason for it to cool until GHG levels in the atmosphere are significantly lower. It can be centuries or millenia. Eventuall, regardless of CO2, milankovitch cycles guarantee that it will return.

The arctic gets really, really cold in winter.  Even when it's warmer than usual, it's still below freezing.  That's why most scientists who study the arctic don't think we'll see ice-free (less than 1,000,000 square km of ice) Septembers until the 2050s at the earliest.  And even then, if we reduce our emissions, the Arctic will refreeze every winter and the loss of sea ice will plateau.

Quote
This paper addresses the specter of a September ice-free Arctic in the 21st century using newly available simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5). We find that large spread in the projected timing of the September ice-free Arctic in 30 CMIP5 models is associated at least as much with different atmospheric model components as with initial conditions. Here we reduce the spread in the timing of an ice-free state using two different approaches for the 30 CMIP5 models: (i) model selection based on the ability to reproduce the observed sea ice climatology and variability since 1979 and (ii) constrained estimation based on the strong and persistent relationship between present and future sea ice conditions. Results from the two approaches show good agreement. Under a high-emission scenario both approaches project that September ice extent will drop to ∼1.7 million km2 in the mid 2040s and reach the ice-free state (defined as 1 million km2) in 2054–2058. Under a medium-mitigation scenario, both approaches project a decrease to ∼1.7 million km2 in the early 2060s, followed by a leveling off in the ice extent.

Full article in the Proceedings of the National Academies of Science (2013) here: http://www.pnas.org/content/110/31/12571

And here's a more recent article about the duration of ice-free portions of the Arctic during summer:  https://pubag.nal.usda.gov/catalog/5405017.  Here's the abstract:

Quote
Global warming and continued reduction in sea ice cover will result in longer open water duration in the Arctic, which is important for the shipping industry, marine mammals, and other components of the regional ecosystem. In this study we assess the length of open water duration in the Alaskan Arctic over the next few decades using the set of latest coupled climate models (CMIP5). The Alaskan Arctic, including the Chukchi and the Beaufort Sea, has been a major region of summer sea ice retreat since 2007. Thirty five climate models from CMIP5 are evaluated and twelve are selected for composite projections based on their historical simulation performance. In the regions north of the Bering Strait (north of 70° N), future open-water duration shifts from a current 3–4months to a projected near 5months by 2040 based on the mean of the twelve selected climate models. There is considerable north–south gradient in projected durations. Open water duration is about 1month shorter along the same latitudes in the Beaufort Sea compared with that in the Chukchi Sea. Uncertainty is generally ±1month estimated from the range of model results. Open-water duration in the Alaskan Arctic expands quickly in these models over the next decades which will impact regional economic access and potentially alter ecosystems. Yet the northern Alaskan Arctic from January through May will remain sea ice covered into the second half of the century due to normal lack of sunlight.


550
Policy and solutions / Seaweed and Seashell Farming
« on: March 09, 2018, 07:06:37 PM »
I read "Atmosphere of Hope" by Tim Flannery recently and came across a topic I didn't know about, seaweed farming.  Apparently it's a way to reduce ocean acidification and draw down CO2 from the atmosphere.  It's been growing exponentially in the past decade and people are making money and producing food from it.

Quote
Globally, around 12 million tonnes of seaweed is grown and harvested annually, about three-quarters of which comes from China. The current market value of the global crop is between US$5 billion and US$5.6 billion, of which US$5 billion comes from sale for human consumption. Production, however, is expanding very rapidly.

Seaweeds can grow very fast – at rates more than 30 times those of land-based plants. Because they de-acidify seawater, making it easier for anything with a shell to grow, they are also the key to shellfish production. And by drawing CO₂ out of the ocean waters (thereby allowing the oceans to absorb more CO₂ from the atmosphere) they help fight climate change.

Here are a couple of links to articles about it:

https://theconversation.com/how-farming-giant-seaweed-can-feed-fish-and-fix-the-climate-81761

https://www.washingtonpost.com/lifestyle/food/seaweed-is-easy-to-grow-sustainable-and-nutritious-but-itll-never-be-kale/2015/10/26/1d1719b8-7750-11e5-b9c1-f03c48c96ac2_story.html?utm_term=.ddbbc9294451

https://e360.yale.edu/features/new_breed_of_ocean_farmer_aims_to_revive_global_seas

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