Poll Is it happening?-GlobalWarming

[Bj]

These bonds are strongest at 4°C. After that, they start to degrade and the molecules move further apart. If they do that, you have less mass in the same volume, meaning lower density.
That's why ice floats on the water and that's why water as a substance is of such significant interest.

BJ: Ice is a sort of crystal, these don't get the smallest possible package. You have some special electrostatic connections between the atom pairs there, which push the atoms away a bit. Water is densest at about 4°C at normal pressure, if I remember correctly - that's why freshwater fish survive in the winter, as the lowest region of the lake never freezes.

Thanks guys, I think I understand that little phenomenon a little better now.

 

[Eagle]

I stand corrected. My initial premise was based on my experience making Ice Cream, and it didn't occur to me that the salt lowers the density of the water, causing it to expand. Doh!

Ice cream has a lot of air mixed in it too. That is why it is so soft and doesn't hurt your mouth when you eat it despite being -10 C.

 

[Quick_Nick]

I know I said no more from me ... but, just to show that the government and NASA aren't infallible:

http://www.telegraph.co.uk/opinion/main.jhtml?xml=/opinion/2008/11/16/do1610.xml

I'm glad someone brought up that link. (I was going to, but didn't bother )
I'm not saying I agree with it, and I'm not saying I don't agree with it, but it's an interesting article. It would be more believable if some better-known news sources would mention it, but it seems like a very possible scenario anyways.
Thanks again for posting that. I won't yet vote in this poll though.

 

[unknown_orbiter]

A good scientist can tell you how much he is wrong.

Going back to an earlier post, I would like to commemorate Urwumpe an a very wise statement.

 

[RisingFury]

I love in Slovenia, Europe.

Most of Slovenia used to be covered by snow from late October, right up to March. We'd get so much snow that when I was going to primary school, it'd take me 20 minutes instead of 5.

For the past few years, we're getting barely any days that it's snowing at all.



The three lakes I have in my town used to freeze over in the winter... the ice would be thick enough to drive a car on. Pretty much every day was below 0.
Now, we're happy if we see a thin crust of ice forming on the lakes at any point during the winter...


Right now, November 19., it's still so warm I'm taking my bike to school instead of walking. If I see any snow on the ground this year, I'll pop a bottle of champagne.



Slovenia has always had problems with hail in the summer, but the past two summers have been crazy. Hail the size of oranges fell from the sky, thunderstorms lasting for 24 hours or more, flash floods so powerful they moved houses around... and this year, there was even a talk of a tornado. Although officially the swirling wind never reached tornado strength, it was still powerful enough to level complete forests. Twisters in a places that is a hilly as Slovenia?

 

[cjp]

About arctic melting:

For a floating object (like ice), the mass of the displaced water is equal to the mass of the object (counting both the part under water and the part above water). The volume of the displaced water is equal to the volume of the part of the object under water.

Let's call the volume of ice below water Vb, and above water Va. Now, what happens when we take the ice out of the sea: the volume of the sea(*) decreases with Vb. Now, if we melt the ice from just below freezing to just above freezing (hardly any density change), this results in a volume of water of Va+Vb. Adding this to the sea will increase the volume of the sea with this amount, so the net result is a sea volume increase of Va.

Did I make a mistake here? I always learned it shouldn't change.

(*) Actually the volume of sea water doesn't change of course, but the sea level would drop an amount equivalent to this:
Say, the sea has a surface A and an original height h, then the original true volume would be A*h - Vb, while a naive measure would be A*h. After taking out the ice, the true volume would still be A*h - Vb, and the new height would be h' = h - Vb/A, so delta_h = -Vb/A. You would see the same sea level decrease if the volume truly decreased with Vb.

 

[tblaxland]

Now, if we melt the ice from just below freezing to just above freezing (hardly any density change), this results in a volume of water of Va+Vb.

Did I make a mistake here? I always learned it shouldn't change.

Yes, I highlighted the mistake in red. When water undergoes a phase change from solid to liquid, its density changes considerably, even though the temperature change is quite small. Water ice has a density of 0.9167 g/cm³ at 0°C, whereas liquid water has a density of 0.9998 g/cm³ at the same temperature.

So what happens is that the ice shrinks from volume Va+Vb to volume Vb and there is no net change in water level (as previously graphically demonstrated by BJ).

EDIT: The two main predicted contributors to future sea level rise are mostly thermal expansion (110-430mm) and melting of ice which is not currently floating in the oceans (mainly glaciers, 10-230mm).

 

[cjp]

Water ice has a density of 0.9167 g/cm³ at 0°C, whereas liquid water has a density of 0.9998 g/cm³ at the same temperature.

Ah, that is what I was looking for. You see, I tried to find out what the effect of salt in the sea is, but this error got in the way.

So, for the displaced water (d), ice above (a) and below(b) sea level, the following relationships between volume (V) and mass (m) exist:
Vd = Vb
md = ma + mb
md = dens_sea * Vd
ma = dens_ice * Va
mb = dens_ice * Vb
So:
dens_ice * (Va + Vb) = dens_sea * Vb
Va = Vb * (dens_sea - dens_ice) / dens_ice
With dens_* being densities.

This makes sense, as it demonstrates dens_ice needs to be lower than dens_sea to have a positive value for Va.

Now let's fill in some values:
dens_ice = 0.9167 g/cc
dens_sea = 1.025 g/cc (it's salt water)
So, Va = 0.1184 * Vb
(only 11% of an iceberg is above water, which is still more than for an ice cube in fresh water)

Now, taking away the ice reduces the sea level equivalent to Vb. Melting the ice results in (dens_ice/dens_water) * (Va+Vb) water, with dens_water being the density of fresh water:

dens_water = 0.9998 g/cc

So, that is (0.9167/0.9998) * (1.1184 * Vb) = 1.025 * Vb. Probably not a coincidence that this 1.025 is about the density of sea water. Anyway, the net result is still 0.025 * Vb increase of volume. So, when melting the arctic, effective sea volume increases with 2.5% of the arctic ice volume.

Now, I should really take into account some non-linearities in the density resulting from mixing cold,fresh and warm,salt water, but I'll leave that as an exercise to the reader .

 

[Urwumpe]

small correction: Floating arctic ice volume.



Most ice on this planet is not floating.

 

[cjp]

small correction: Floating arctic ice volume.



Most ice on this planet is not floating.

Yeah, for the non-floating ice that melts, you get the full 100%. Also, as has been mentioned, thermal expansion causes more significant sea-level rise.

And in Holland, another effect is the sinking of the ground. Partially an effect of nature (an after-effect of the last ice age), and partially because it used to be a swamp here, but we pumped out all the water. Most parts of Holland used to be around sea level. Now the lowest point is at -6 meter.

 

[Omhra]

the question I have is... What amount of this heating up is making its way to the crust and mantle of Earth? I feel there is a misinterpretation that the Global Warm-up stays only in the atmosphere.. this has to be wrong.. the mantle must also be heating up.
Any one?

 

[cjp]

the question I have is... What amount of this heating up is making its way to the crust and mantle of Earth? I feel there is a misinterpretation that the Global Warm-up stays only in the atmosphere.. this has to be wrong.. the mantle must also be heating up.
Any one?

On Wikipedia:

Global terrestrial heat flow is about 45 TW (1 TW = 1012 watts). This is very approx 1/10 watt/square meter (which is about 1/10,000 of solar irradiation).

This is also why I don't think geothermal energy production is useful on a global scale (hot spots like Iceland are an exception). At least not as useful as solar and wind energy.

And even if it were big, heat coming from below has had more than enough time to come into equilibrium with radiation leaving earth. Only changes in the heat flow could potentially cause climate changes. I never heard of any such changes being measured. Even if they existed, I'd expect them to take hundreds or thousands of years, and not the decade scale of the current climate change.

So, the answer is: no.

 

[unknown_orbiter]

My belief: Global warming is happening... because it has been happening in cycles for billions of years. We are ants on this planet. The co2 we have been releasing over the past century is NOTHING compared to its levels during the Jurassic or Cretaceous periods. The worst we can do is pollute. Radiating the planet, pollute the water, and kill off animals. The atmosphere is too old, too thick, and allover to damn large for some SUV exhaust to dent it. People say they want weather and temperature to stay the same, and not getting that must mean it is our fault. Meteorology is based upon chaos, not conformity.

 

[pete.dakota]

The co2 we have been releasing over the past century is NOTHING compared to its levels during the Jurassic or Cretaceous periods.

You got proof on that? Or are you assuming?

The worst we can do is pollute. Radiating the planet, pollute the water, and kill off animals. The atmosphere is too old, too thick, and allover to damn large for some SUV exhaust to dent it.

I'm really not trying to insult you, or make a personal attack: but this is a very ignorant opinion. To assume man can't change the atmosphere because it's too 'big' is ridiculous. We (and more importantly, our influence) is greater than the sum of our parts: i.e, even though humans are tiny compared to the planet, the ramifications - over centuries - of our actions are not.

Consider that the Tsar Bomb matched 1% the energy output of the Sun, in one instance.

Though, as you say, the atmosphere is too large for one SUV to dent it, try several billion SUVs, cars, factories, boats, planes all around the world venting out greenhouse gasses CONSTANTLY... it never stops.

As the evidence cited above shows -- though I'm sure it's being mostly ignored by nay-sayers -- practically all scientific research into man's effect on climate change suggest, with very little doubt, that our actions are contributing and exacerbating global warming - perhaps up to 90% that of what would be expected to be naturally occurring.

Sometimes I can't help but think that, around here, some people just like playing Devil's advocate...

 

[Urwumpe]

Also - anybody who wanders over Earth with an open eye will have a hard time to find a spot not formed by humans. The landscape of Croatia for example was never always like that. It was formed by humans, especially the venetian shipyards.

Also, for showing the scale of our own actions: The oil and coal we burned in the last 150 years is equal to CO2 gathered by plants in 150 million years.

 

[unknown_orbiter]

Yes there is proof of Co2 levels during these periods. We are producing a lot of Co2 as a whole, but consider the size of the atmosphere. I did not mean to that the atmo is too big to be affected. I mean that we cannot drastically change the atmo for a while more. Yes, we are making an impact on the temp by fractions of degrees. Really there is no real way to determine HOW MUCH we are hurting ourselves. The human race is raping the planet (rain forest destruction, strip mining, etc), but we are still small compared to the Planet though.
Meh to be honest I have very mixed feelings about our effects. We are only JUST now experiencing global warming to a noticeable degree, and it would be very coincidental if it wasn't due to us.

 

[Urwumpe]

Yes there is proof of Co2 levels during these periods.

Yes - there was CO2 at that time.

There was even more in the past. But: How will you like tropical sea surface temperatures of 42°C? That is whirlpool temperature.

We are producing a lot of Co2 as a whole, but consider the size of the atmosphere.

It weights only about 5.1480×1018 kg on the average.

Or: 5,148,000 billion tons or gigatons. By burning fossile fuels, we produce 27 Gigatons of CO2 each each.

That may not sound much, but other big sources (volcanism and decay of organic material) adds only about 10-20 times more each year.

And 5-10% is easily enough to tip a scale and disturb a fragile balance.

 

[zerofay32]

Not happenning, not an issue.

Zerofay32

EDIT: Also, nature is inherently Inbalance. The problems happen when humans try to balance nature.

 

[pete.dakota]

Not happenning, not an issue.

Evidence, please.

Saying it's not a issue, citing SUV-based metaphors, and the enormity of the atmosphere is not enough to dismiss the solid, scientific research that you, as an internet user, are privy to, and need to understand.

 

[Omhra]

I had to laugh... If we try to reduce emissions we are meddling? and if we burn fossil fuels we are not... do you even read what you type?...