Climate Policy

[kandrathe]

I am not sure that is true. A plant would over his whole lifetime have a 0 contribution to the CO2 concentration, that is if its whole carbon based 'skeleton' would decompose, if it doesn't it has a negative impact on CO2 concentrations.

This is not true. Where does peat come from? Unless you want to consider a plants life span to be millions of years. Then, due to natural processes the carbons can be released sometimes after thousands or millions of years. I'm not even sure what happens to biomass that falls to the bottom of deep oceans. At the end of the last ice age at 18000 and 13000 years ago changes in the environment released over 600 Gt of CO2 into the atmosphere in two large burps (the equivalent of our current rate over 100 years).

And especially because we are definitely having less plant biomass now than we had a few 1000 years ago this seems a bit strange to me.

How is this true? I think you assume it is true, but while we have less forests I'm not sure we have less biomass. If this were true, wouldn't we see a decrease in O2 levels?

Water vapor is passive in this equation. Water vapor concentrations in air depend on temperature, after that it is positive or negative feedback. This is because it is in a physical equilibrium, while CO2 is in a chemical equilibrium (or maybe there are huge stockpiles of dry ice on Antarctica).

In measuring the "green house effect", you need to measure the impact of both water vapor, as well as other GHG's in absorbing and dissipating heat, as well as clouds (and other albedo sources) in both insulting the ground and reflecting radiation away. It has been a big mistake in this whole debate not to attempt to understand this highly complex system. Even solar flares with increases in ionizing radiation may have a temporary effect in increasing the atmospheres albedo effect.

In all the percentages and values you mention be sure that you all use the same base temperature, so 0 K, or better an average global temperature of say, 1850. So when you would take 0 K as base than the 0.28 % contribution of CO2 might be right, but has no practical sense or use.

Right. I'm just trying to make the point that CO2 is probably not as important as everyone seems to think it is, but I don't have any issues with transforming away from fossil fuels for other reasons (e.g. limited resource, pollution, renewable sources are available, etc.).

[Jester]

In measuring the "green house effect", you need to measure the impact of both water vapor, as well as other GHG's in absorbing and dissipating heat, as well as clouds (and other albedo sources) in both insulting the ground and reflecting radiation away. It has been a big mistake in this whole debate not to attempt to understand this highly complex system.

Your understanding of the scientific literature is that there has been no attempt to address the issues of the greenhouse effect of water vapor, the role of GHGs in absorbing and dissipating heat, and the insulating and relfective effect of albedo and clouds? I'm way too lazy to search the literature, but if you didn't find at least a dozen papers on each of those topics in the last decade alone, I'd be dowright shocked.

Or did you mean in the debate here on the Lounge? I don't know that we have anyone qualified to understand a technical paper on any of those issues, let alone combine them into a comprehensible synthesis.

-Jester

[kandrathe]

Your understanding of the scientific literature is that there has been no attempt to address the issues of the greenhouse effect of water vapor, the role of GHGs in absorbing and dissipating heat, and the insulating and reflective effect of albedo and clouds? I'm way too lazy to search the literature, but if you didn't find at least a dozen papers on each of those topics in the last decade alone, I'd be downright shocked.

I found quite a few, but you are correct, most of the physics and chemistry is beyond me.

Or did you mean in the debate here on the Lounge? I don't know that we have anyone qualified to understand a technical paper on any of those issues, let alone combine them into a comprehensible synthesis.

Right, I meant here at the Lounge. I don't think eppie should just dismiss water vapor, since it is the most significant factor in the green house effect (~ 70 to 90%). Although, he might just be talking about variation depending on temperature. Yet, it seemed like he was saying it was irrelevant.

[Jester]

I don't think eppie should just dismiss water vapor, since it is the most significant factor in the green house effect (~ 70 to 90%). Although, he might just be talking about variation depending on temperature. Yet, it seemed like he was saying it was irrelevant.

Here's Gavin Schmidt's explanation for its irrelevance, if you're interested.

In short, water vapor doesn't stay in the atmosphere for long. Its long-term values are determined by other variables. Thus, it does not drive climate change, but rather reinforces other changes, like an increase in CO2.

-Jester

[eppie]

This is not true. Where does peat come from? Unless you want to consider a plants life span to be millions of years. Then, due to natural processes the carbons can be released sometimes after thousands or millions of years. I'm not even sure what happens to biomass that falls to the bottom of deep oceans. At the end of the last ice age at 18000 and 13000 years ago changes in the environment released over 600 Gt of CO2 into the atmosphere in two large burps (the equivalent of our current rate over 100 years).

Yes you are right.....this would mean a zero total contribution (after the peat has been burned).
The only way of systematically getting less CO2 in gas form is trapping in hydrocarbons or elemental form (so oil or coal formation ) or as carbonates in non soluble minerals. Or an average larger amount of plant biomass on earth.

How is this true? I think you assume it is true, but while we have less forests I'm not sure we have less biomass. If this were true, wouldn't we see a decrease in O2 levels?

Hmm, I am starting doubt. Anyway, we will have less biomass if we add up the contribution of the biomass that has been transformed in oiol, coal and peat. I am not sure if we would see decrease in O2 levels, O2 depends not only on trapping in CO2 and releasing through photosynthesis I think.

In measuring the "green house effect", you need to measure the impact of both water vapor, as well as other GHG's in absorbing and dissipating heat, as well as clouds (and other albedo sources) in both insulting the ground and reflecting radiation away.

Of course, but the thing with molecular water is that it is always (even in ice ages) available in limitless quantities, and vapour will always be in equilibrium depending on temperature and pressure. So higher temps. mean more water vapour (thanks Pete) but it can't be a steering factor. CO2 is only available in gas form or solubilized form, but then it is technically carbonate) and otherwise it is in another chemical state. If you pump 20 times the CO2 concentration in air, it will stay there untill it gets absorbed by the sea and 'eaten' by plants. This has two results, more plants (iof we don't destroy them again) and a more acidic sea.
If you pump 20 times the amount of water in the air, you get rain. So of course water absorbs heat and aids global warming, but it is a passive contributor.

It has been a big mistake in this whole debate not to attempt to understand this highly complex system. Even solar flares with increases in ionizing radiation may have a temporary effect in increasing the atmospheres albedo effect.Right. I'm just trying to make the point that CO2 is probably not as important as everyone seems to think it is, but I don't have any issues with transforming away from fossil fuels for other reasons (e.g. limited resource, pollution, renewable sources are available, etc.).

Solar flares have always been there, and they will influence heating up, but this is hardly on geological time scales. So of course there are many other factors that influence warming.....but most of them are not systematic.

[eppie]

I found quite a few, but you are correct, most of the physics and chemistry is beyond me. Right, I meant here at the Lounge. I don't think eppie should just dismiss water vapor, since it is the most significant factor in the green house effect (~ 70 to 90%). Although, he might just be talking about variation depending on temperature. Yet, it seemed like he was saying it was irrelevant.

I don't dismiss it, but it can never be a factor that steers climate change, it is something that follows (so a positive (or negative) feedback.
Again, this all is important when you take 0K (or something like that) as base line. But for the discussion, and for the relevance for humanity, we should take a an average temperature as base point.

[Zenda]

While I agree that the world is over populated, I am not so heartless as to want to see the excess ones starve and freeze until we reach the new bearing population.

The world is not overpopulated (especially regarding energy needs), and many people are starving and freezing already. 10% of the total population require 10 times (or more) as much space as others, remember?

To put things into perspective, a recent investigation suggests that wind-generated energy alone could take care of our current electricity consumption. At 20% capacity...

http://www.pnas.org/content/106/27/10933

[Ashock]

The world is not overpopulated (especially regarding energy needs), and many people are starving and freezing already. 10% of the total population require 10 times (or more) as much space as others, remember?

To put things into perspective, a recent investigation suggests that wind-generated energy alone could take care of our current electricity consumption. At 20% capacity...

http://www.pnas.org/content/106/27/10933

I am already doing my part. I only flush after a deuce. I wish others were just as dedicated to the cause.

[--Pete]

Hi,

Solar flares have always been there, and they will influence heating up, but this is hardly on geological time scales.

The long term solar cycles are not well understood, thus this statement is unfounded. It may be true, it may not.

--Pete

[--Pete]

Hi,

The world is not overpopulated . . .

Depends on your criteria. In my opinion, the world became overpopulated with humans the day we first had to do something about our own waste -- no other species has had that problem.

--Pete

[kandrathe]

The world is not overpopulated (especially regarding energy needs), and many people are starving and freezing already. 10% of the total population require 10 times (or more) as much space as others, remember?

First, I don't agree. It depends on what you believe to be the appropriate density of people per square mile.

Second, people choose to live in higher densities, and some people live in extremely high densities. These areas still require a huge amount of energy, food, water, and materials to be transported to them resulting in higher risks when these supply chains are severed. If you wanted to be authoritarian, you could make them disperse. 4% of the US energy consumption is used to grow food, but 15% is used to move it to peoples plates.

Consider how a city like Phoenix, Arizona exists. It has no water, poor land for sustainable agriculture (yet with irrigation and fertilizer it ranks fairly high), but tons of unused solar power. Yet, they generate 4,000 MW at Palo Verde (nuclear), 2,040 MW at Four Corners (coal), 995 MW at Cholla (coal), 2250 MW at Navajo Reservation (coal), 1060 MW at Redhawk (ng), 1000 MW at West Phoenix(ng), 680 MW at Octillo (ng), 450 MW at Sundance (ng), 395 MW at Saguaro(ng), 16MW at Douglas (diesel), 150 MW at Yucca (ng) and a plethora of solar installations with a combined output of 5 MW. That is a generating capacity just over 13000 MW, of which 4000 MW is nuclear and 5 MW is solar.

Third, I think there is a national interest (for all countries) in maintaining the current population level, or one just slightly smaller. GDP, and national defense often rely upon a ready supply of people to run the workforce and military.

Fourth, food supplies are artificially high due to the use of fossil fuels. "If the fertilizers, partial irrigation [in part provided by oil energy], and pesticides were withdrawn, corn yields, for example, would drop from 130 bushels per acre to about 30 bushels." (source)

To put things into perspective, a recent investigation suggests that wind-generated energy alone could take care of our current electricity consumption. At 20% capacity...

http://www.pnas.org/content/106/27/10933

/facepalm

I spent quite a bit of time debunking that myth on the lounge before. Now, you said wind energy. But, first let's consider the source of wind energy, solar energy. Wind is even less reliable, and really only viable in some areas. The upside is that excess solar energy over the ocean, can provide some wind energy to the land.

"Over the course of a year the average solar radiation arriving at the top of the Earth's atmosphere is roughly 1366 watts per square meter (see solar constant). The radiant power is distributed across the entire electromagnetic spectrum, although most of the power is in the visible light portion of the spectrum. The Sun's rays are attenuated as they pass though the atmosphere, thus reducing the insolation at the Earth's surface to approximately 1000 watts per square meter for a surface perpendicular to the Sun's rays at sea level on a clear day." (source) Of course, that is assuming 100% perfect conditions, this map shows the calculated averages for the planet. If you look at where I live, the yearly mean value is 140 to 160 W/m2. Most people around here use 600 KWh/month (30 days), or 20 KWh/day, or 20,000 Wh / day. Assume about 20% efficiency for modern solar panels, and then using math, you can figure how many square meters of solar panels just one house would need. Using the optimistic number of 160 * 20% giving 32W/m2. Summer days are up to 15 hours (15h x 32W/m2 = 480Wh/m2), and winter days are 8 hours (8h x 32W/m2 = 256Wh/m2). I need heat, while AC is only a luxury, so I will need to assume the worst case here. To get 20,000 Wh/day I would need (20000/256 = ~78 square meters of solar panels), so figure 8 banks that are 2 meters x 5 meters in size. ~20% efficient solar panels cost about $2/watt, or figure about $40,000 for the solar panels, then we need AC/DC converters, regulators, and a bank of batteries to provide electricity for the 16 hours of darkness in the dead of winter. So, I think I figured before another $25,000 for the equipment besides solar panels. Now we are up to about $65,000 to run a typical home around here on solar power. Then, we should consider 1) we have a pretty hazardous power plant in our house, 2) we need to maintain it when it breaks, and 3) it has a limited life span ( lets be generous and say 20 years). So, without factoring in the cost of capital, and just dividing the $65K by 20 years we are spending $3250 / year on our power, or $270 /month, or $.45 per KWh. Compare that to current energy plant rates of $.12 to $.15 per KWh. But, perhaps you were thinking of a huge solar farm occupying thousands of square miles.

So as an exercise for you, calculate the 13000MW capacity of Arizona converting it to solar. How many square meters of panels, covering how many square miles of land? How do they handle night time demand?

Ok, now for that article on wind power. The USA currently produces 4,156,745,000 MWh of electricity. The article you linked to suggested a network of 2.5 MW turbines, meaning (and being very generous with the numbers) 69,279,084 (2.5 MW running 24 hours/day) wind turbines using about 10 acres each (pad, blade clearance, roads, shack). This means just to replace current generating capacity you will cover 1,082,486 square miles just for the wind turbines, less power lines. For comparison, Kansas occupies 82,277 square miles.

[Concillian]

nature is not all that predictable either.

It certainly seems that something is changing. People probably have had some level of impact, and maybe jostled the equilibrium. Or, maybe there is some other long wave explanation for an increase in temperature, which is also resulting in a proportional related decrease in CO2 fixation. That scenario also seems to have merit. It is easy to show statistical causal relationships, but this does not mean it is actually true. For example, chart the expansion of deserts over the past 300 years to populations. Are we the cause?

It's not predictable, however:

when you have an event (invention of the steam engine, start of the industrial revolution) ca. 1770 or so
Then after that event you see a statistical anomoly (CO2 levels rather significantly higher than in recent history (500k years or so)
And the response makes sense from the standpoint of physics (steam engines burn fossil fuels and emit CO2)

Why would you ignore that and instead think it's really just a coincidence that all this has happened at exactly the same time (give or take a decade) that mankind started burning fossil fuel en masse?

I found a better graph that illustrates the point:
http://en.wikipedia.org/wiki/File:Carbon...400kyr.png

Note the inset, which demonstrates the inflection point right around the start of the industrial revolution.

Now I think there is room to argue that CO2 is not as significant a contributor to temperature rises as some currently believe (* check note later). However, the data I've seen is pretty conclusive on mankind being the primary contributor to recent CO2 PPM levels. To argue any different is basically arguing a 1 in a billion type of probability is what we're experiencing. I'm not saying it's impossible, but if I'm making policies that decide the fate of millions of people, I'm banking on the cause and effect relationship and our current understanding of physics rather than some massively improbable coincidence that mother nature decided to start out on a natural statistical anomoly ±10 years from the start of the industrial revolution.
(*)
I think if you look on longer timescales than the previous million years (more like the last BILLION years) you can find examples where CO2 concentration in the atmosphere was nearly an order of magnitude higher than now, but climate was similar. I'm not completely sure what other concentrations in the atmosphere were like at that time, I've seen some data that I haven't been able to verify the source of showing oxygen under 5% like half a billion years ago too, I'm not sure I want to use that kind of data as a basis for governmental policies, but at least there is some actual data around that doesn't rely on throwing scientific methods out the window and assuming this is all one big coincidence.

[Zenda]

Ok, now for that article on wind power. The USA currently produces 4,156,745,000 MWh of electricity.

That's where you go wrong. The article made no claims about the possibilities of providing for a world full of Americans. It was about total current world consumption, and how much that would take. It should be no surprise that if you take only a subset with way above average needs, that this subset would also require more space then average.

You have the same wrong assumptions on overpopulation. Sure, if the world was full of Americans, it would never be able to sustain the amount of people we have now. But as it is, 90% of the world population could vastly improve it's standards of living by getting rid of just the other 10%.

PS.

For the record, if we'd try the same calculation for the Netherlands, we'd need far more 'extra' land (relatively). While our personal ecological footprint is a bit lower, our population density is much higher.

[Zenda]

I spent quite a bit of time debunking that myth on the lounge before.

That looks to be the same nifty calculation that you used before, yes.

Let's take a closer look. I don't agree with every assumption you made, but we'll step over that and concentrate on the mathematics.

With a yearly mean value of 140 to 160 W/m2, let's say 150 w/m2, and efficiency of 20%, we arrive at 30 W/m2. That is not the same as 480Wh/m2 (summer) or 256Wh/m2 (winter) for a day. The number you started with is a yearly mean, and already compensates for nights. So, the average daily yield would be 24*30 = 720 Wh/m2. So, with 20000 Wh needed per day, an area of 28 m2 would be enough.

Next, to compare prices, you use $2/W as a basis and add about 50% for other provisions. Let's make it $3/W, then. Since you already have corrected for 80% inefficiency in the previous part of the calculation, that $3 would be for each netto Watt. So, 28 m2 would cost 3*30*28 = $2520. Now, is that per day? No, that's for the lifespan of the installation. At 20 years, that would be $10.50 per month. That seems a lot lower as $270 per month to me.

If you want to argue that nights should still be accounted for, multiply the $10.50 by 3. If you think there should be another reduction of 80% somewhere, multiply the $10.50 with 5. Do both, and you'll still be below the $270.

[kandrathe]

Next, to compare prices, you use $2/W as a basis and add about 50% for other provisions. Let's make it $3/W, then. Since you already have corrected for 80% inefficiency in the previous part of the calculation, that $3 would be for each netto Watt. So, 28 m2 would cost 3*30*28 = $2520. Now, is that per day? No, that's for the lifespan of the installation. At 20 years, that would be $10.50 per month. That seems a lot lower as $270 per month to me.

Nope. I think the 150W/m2 is the results of measuring the suns angle and the number of cloudy days. If is as you say, average out for an entire year, then it is useless for calculations, since you really need to plan for peak need.

For watts, you need to look at how many watts you would use for the entire 24 hours period, and then assume you will capture and store that during the sunny part of the day (hoping there is one). I started by looking up the average usage here in Minnesota, and that being 600 KWh /month divided by 30 is 20,000 watts hours per day. A day has only so much time for which you can generate the load, so I figured 8 in the winter,and more like 16 in the summer. So, there is where you get 20000 watt hours / 8 hours = 2500 watts for winter and 1250 watts for summer. Then, you need to go back to insolation calculations to figure out how much power you get per square meter to calculate the total area required. 150 W / square meter looks about right for what we get in Minnesota, compared with the amount of the 1000 W per square meter at sea level on the equator with a cloudless sky. Now you can factor in the 20% efficiency if you like here, so in terms of capture you would get 30W / square meter. So, if we look at 2500 / 30 we get 83.34 square meters again (I used 160 instead of 150).

Something is wrong with your calculations. Do you use 2520 / $3 = 840 watts in a day? That would be equal to four 50 watt light bulbs left on for a little over 4 hours. Look up the price of solar panels. Here is an description of one persons journey with installing solar power. His bids ranged from $38K to $60K after rebate(s).

[kandrathe]

That's where you go wrong. The article made no claims about the possibilities of providing for a world full of Americans. It was about total current world consumption, and how much that would take. It should be no surprise that if you take only a subset with way above average needs, that this subset would also require more space then average.

How much energy will you allot to each person in your world? Any unit of power measurement over time will do.

You have the same wrong assumptions on overpopulation. Sure, if the world was full of Americans, it would never be able to sustain the amount of people we have now. But as it is, 90% of the world population could vastly improve it's standards of living by getting rid of just the other 10%.

How much food would you allot per person in your world? Calories per day would be a useful start. Once petroleum based agriculture crashes, how will you sustain the current supply of food? Quintuple the number of acres tilled? Or, will you allow starvation to crash the population down to pre-petroleum levels (about 1 billion). Also consider that the US exports quite a bit of its agricultural production to feed the rest of the world.

Then, consider, "China presently has about 1.827 billion mu (121.8 million hectares), or 1.39 mu (0.09 hectares) per capita, about a third of the global average. In 1996, it had 1.951 billion mu (130.07 million hectares), or 1.59 mu (0.11 hectares) per person -- a loss of 6.4 percent of the arable land in 11 years mainly to urbanization." I'm not sure what you plan to do about the farm land shortage in China, let 2/3 of the population die off?

Once you answer those questions, we can determine whether we want to live in your world, or mine.

In my world we would work toward sustaining our current standard of living, while continuing to adopt efficiencies, and moving toward sustainable harmony with our environment. All of this transformation being a net positive experience for the economy, and its participants. I envision a world with cheap and abundant energy, where the people have learned to live in harmony with their planet.

[kandrathe]

And how does the 88.7 break down, if not into anthropogenic sources?

Um, I'm not sure. It was related to the portion of the unsequestered CO2 based on calculations I used from some scientific paper. But, as I recall, the IPCC goes has 4 scenarios (Gton CO2 per annum);

Scn. Human (+) Natural (+) Subtotal (+) Natural (-) Net (+&-)
---------------------------------------------------------------
_A_ 7.0 (100%) 0.000 ( 00%) 07.000 03.50 (50%) 3.5
_B_ 7.0 ( 95%) 0.400 ( 05%) 07.400 03.90 (53%) 3.5
_C_ 7.0 ( 50%) 7.000 ( 50%) 14.000 10.50 (75%) 3.5
_D_ 7.0 ( 05%) 133.0 ( 95%) 140.00 136.5 (98%) 3.5

The IPCC prefers Scenario C (the 50/50 model) which results in 75% of the added carbon from both natural and human sources being sequestered, leaving 1.25 Gton / annum of anthropogenic CO2 left in the atmosphere (and 1.25 Gton from nature). But, it is likely all four scenarios are too static to be of much use anyway in describing such a dynamic system. There are large changes in the natural release of CO2, and also in the sequestration of CO2. It really shocks me that the measured CO2 increase is so very linear and constant. You would think if it were due to human release that it would vary with the world GDP, or at least the fluctuations in power plant usage. But, rather it oscillates up and down each year with the coming of summer and winter, almost as if it rose and fell with the average daily temperature.

Again, as I see there are two simple explanations (not that this is a simple problem); A) CO2 rises linearly with the seemingly linear increase of small levels of GHG's released by humans for the past 300 years, or B) CO2 rises with an increase in temperature due to a reduced ability of the environment to sequester it. So I think that is the $10,000 Climatologist question; which came first, the CO2 rise, or the temperature rise?

[Jester]

Again, as I see there are two simple explanations (not that this is a simple problem); A) CO2 rises linearly with the seemingly linear increase of small levels of GHG's released by humans for the past 300 years, orB)CO2 rises with an increase in temperature due to a reduced ability of the environment to sequester it. So I think that is the $10,000 Climatologist question; which came first, the CO2 rise, or the temperature rise?

Not really. The role of CO2 as a greenhouse gas is well understood. If CO2 is being released, the temperature will rise, unless some feedback interferes. It doesn't matter if the CO2 begins the warming or not. That isn't really in debate.

If what you're saying is that there is some other factor generating the observed warming, and that CO2 is only playing a secondary role, then the obvious question is: what? As far as I can tell, every attempt to come up with something else has fallen far short of even being a better explanation than CO2, let alone completely displacing the idea that CO2 is a major contributor to warming.

-Jester

[Zenda]

Nope. I think the 150W/m2 is the results of measuring the suns angle and the number of cloudy days.

You think so? Should you not be sure, before using that number as a basis for your calculations? Anyway, like I said, you can assume winter conditions all year long, and multiply the costs with 3 to arrive at $31.50 per month.

Btw, I'm not claiming that $10 to $30 per month is realistic. It just the result of your faulty assumptions and wrong approach.

Do you use 2520 / $3 = 840 watts in a day?

Don't you have any feeling for numbers?

Allright, let's calculate backwards. One Watt is 1 Joule/Second, and 1 Wh is 3600 Joule. If you need 20 kWh per day, you need 20*3600*1000 = 72.000.000 joules per day. If $3 gives you 1 joule/second for 8 hours a day (your winter conditions), it would yield 1*8*3600 = 28.800 Joules per day. So, you would need 72000000/28800 = 2500 units of $3, which is $7500. Which is 3 times the $2500 we had earlier, like I predicted.

Here is an description of one persons journey with installing solar power. His bids ranged from $38K to $60K after rebate(s).

Well, I guess that shows you are wrong too. This person has the following conclusion:

http://www.extremetech.com/article2/0,28...685,00.asp

"So our estimated annual power bill will drop from about $4,400 a year to less than $1,100 a year, with the average cost per kWH dropping from 25 cents to 6.3 cents. The payback time, assuming energy costs don't spike steeply, is a little under nine years."

[Zenda]

Also consider that the US exports quite a bit of its agricultural production to feed the rest of the world.

The times with the USA being one of the largest grain exporters (most of it to 'enemy' Russia, oddly enough) are over, in case you missed that. Nowadays, the USA imports far more food as it can export.

There is the huge amount of imported foodstuff for your lifestock to consider, yes. Don't you know that 'growing' one Kg meat can take 5 to 30 times the amount of land needed to grow a Kg of grain? No, that's not the size of the pastures they are in.