The Scientific Global Warming Debate.

[lutzj]

Global warming can also be the result of a natural cycle as well. While it's not certain, it's possible that Earth was recently in a minor ice age. Thus any recent temperature increases observed can be accounted for by a natural cycle. Of course this argument is rather difficult to prove and doesn't quite fit in to your definition of "unnatural way."

It WAS in a minor ice age: an "ice age" is defined as any period with glaciers at the poles. Earth is simply continuing on the warming trajectory it has been on since 30,000 years ago. Our own records cannot be called very accurate for two reasons:

1. We only have about 150 years of reliable data.

2. Just before we started taking systematic measurements, much of Europe, North America, and other places warmed considerably due to the end of the Little Ice Age. Temperatures have been bouncing around for most of human history, it's just that we've only caught on recently.

 

[shyuhe]

So I (partially) answered my own question after reviewing some thermo. To start with, radiation is the transfer of heat via EM radiation (UV/IR etc.), conduction is the mechanical transfer of heat from direct contact (imagine a hot plate and cold plate touching), and convection is the transfer of heat by fluids moving from a hot region to a cold region (hot water put in a cold pool so that hot and cold atoms are now mixed together)

IR is heat transfer via radiation and is absorbed by CO2 in the air. This is then converted into mechanical energy (vibrational/stretching of the CO bond). So it doesn't re-release heat back into the atmosphere via radiation. However since the CO2 molecule still has a higher energy level, it remains possible that it can transfer this energy via conduction - so my original question of why the heat doesn't go into outerspace remains unanswered (obviously it can't escape via radiation or convection). I hope that clarifies my question.

 

[Ball Lightning]

In my opinion which i have said many times before, that humans have caused significant climate change which if not stopped will likely cause drastic unforseen and forseen hard ships for the human race, along with all other life on earth which we hold in our hands.

 

[Ball Lightning]

It WAS in a minor ice age: an "ice age" is defined as any period with glaciers at the poles. Earth is simply continuing on the warming trajectory it has been on since 30,000 years ago. Our own records cannot be called very accurate for two reasons:

1. We only have about 150 years of reliable data.

2. Just before we started taking systematic measurements, much of Europe, North America, and other places warmed considerably due to the end of the Little Ice Age. Temperatures have been bouncing around for most of human history, it's just that we've only caught on recently.

We have around 600,000 years of reliable CO2 and temperature, the current CO2 levels, which have been proved in countless experiments to help increase temperature, have been rising for the last 6000 years, very slowly at first and in the last 200 years more and more rapidaly, now reaching the highest level for at least a million years. And all this came about in the last 200 years and less.

 

[Rheinmetall]

If the timescale is 30,000 years, the change we're experiencing today is too fast for that timescale.

 

[PaperBeetle]

So I (partially) answered my own question after reviewing some thermo. To start with, radiation is the transfer of heat via EM radiation (UV/IR etc.), conduction is the mechanical transfer of heat from direct contact (imagine a hot plate and cold plate touching), and convection is the transfer of heat by fluids moving from a hot region to a cold region (hot water put in a cold pool so that hot and cold atoms are now mixed together)

IR is heat transfer via radiation and is absorbed by CO2 in the air. This is then converted into mechanical energy (vibrational/stretching of the CO bond). So it doesn't re-release heat back into the atmosphere via radiation. However since the CO2 molecule still has a higher energy level, it remains possible that it can transfer this energy via conduction - so my original question of why the heat doesn't go into outerspace remains unanswered (obviously it can't escape via radiation or convection). I hope that clarifies my question.

I don't really know physics, but I would guess that the molecules in the atmosphere don't pass heat into space via conduction because there is virtually nothing in space for them to touch. Convection is going to suffer a similar fate; the atmosphere is fluid, but the vaccuum is not. Which leaves radiation as the only method for heat to get from the earth out into space.

 

[Serutan]

I don't think we're on the same page here Abaddon. I'm questioning why the longwave is bounced back instead of passed through. What's so different about the shortwave that it passes through? Is it because UV can cause a cascading reaction in the ozone layer to pass through the energy but IR is too low energy to start a cascading reaction out of the atmosphere?

No, it has to do with the characteristics of gas atoms/molecules. Each
reacts to the spectrum of radiation in one of three ways : transparent,
absorption, reflection. The greenhouse gases are reflective in a portion
of the IR wavelengths, hence they help retain heat.

As to the OP : I think it's a combination. As has been mentioned, CO2 was
rising before the Industrial Revolution, and has accelerated since. So while
the warming trend already existed, human activity is accelerating and intensifying it.

 

[shyuhe]

Thanks folks. That makes more sense now. Boy I'm out of touch with thermo now...

 

[Falcon02]

As to the OP : I think it's a combination. As has been mentioned, CO2 was
rising before the Industrial Revolution, and has accelerated since. So while
the warming trend already existed, human activity is accelerating and intensifying it.

Also, the average temperature of Mars has been increasing, helping to suggest that Solar cycles do seem to be one of the reasons for increased temperatures. But as stated human activity hasn't helped counter it...

EDIT: NASA - A Gloomy Mars Warms Up

EDIT2: after reviewing the article more closely it appears the warming of Mars seems to be more due to changes in dust distribution and coloration then solar cycles, but I'll leave the link.

 

[Simple Simon]

Also, the average temperature of Mars has been increasing, helping to suggest that Solar cycles do seem to be one of the reasons for increased temperatures. But as stated human activity hasn't helped counter it...

EDIT: NASA - A Gloomy Mars Warms Up

EDIT2: after reviewing the article more closely it appears the warming of Mars seems to be more due to changes in dust distribution and coloration then solar cycles, but I'll leave the link.

Yeah, that article was trumped out by the GW-deniers, but if you actually think about it, TWO planets warming up and all the rest NOT warming up doesn't really say anything positive about a solar trend.

Fact is: earth is warming, no known mechanism BUT retention of heat via suddenly and massively increased greenhouse gasses can explain the warming, and we happen to have blasted a few billion tons of them into the air over the last 8,000 years or so, with a steep increase since ~1750.

Yep, sounds man-made to me!

 

[knez]

Yeah, that article was trumped out by the GW-deniers, but if you actually think about it, TWO planets warming up and all the rest NOT warming up doesn't really say anything positive about a solar trend.

Fact is: earth is warming, no known mechanism BUT retention of heat via suddenly and massively increased greenhouse gasses can explain the warming, and we happen to have blasted a few billion tons of them into the air over the last 8,000 years or so, with a steep increase since ~1750.

Yep, sounds man-made to me!

and you know that how?

 

[Simple Simon]

and you know that how?

what do I know how?

What do you expect here - do you want me to give you a course in climatology or what?

I know earth is warming up from the many different sources of data we have: direct measurements, fossil and subfossil pollen samples, tree rings, foraminifera and other plankton and nekton fossil data, etc.

I know it is not any other mechanism than heat retention, since the sun is not increasing radiation, and the amount of radiation reaching earth is coupled to Milankovic cycles. These are known, and do not explain the current warming, while they DO explain a bunch of past temperature ups and downs. Also, other suggested phenomena, such as solar flare cycles, that fall into the category of 'increased solar radiation' have shown to be not responsible - the solar flares specifically were supposed to correlate, but recent data shows that the correlation was
a) based on bad data
b) does not extend into the 1990 and on.

I know how greenhouse gases work - chemistry textbook.

I know that we pumped loads of them out - records on amount of coal, oil, gas from fossil sources burnt. Also, historical documents show a pretty good account of the amount of deforestation and spread of rice paddies (the latter being a main source of methane).

Ergo: we have a mechanism, we have the substance, we have no other explanation, as all other known mechanism which could be at fault can explain only ancient, but not the current trend.

OK, maybe it's the spaghetti monster doing it, but somehow I do not believe that.

 

[knez]

all the rest NOT warming up

how do you know that?

 

[Simple Simon]

all the rest NOT warming up

how do you know that?

your vocabulary seems rather limited!

I'll answer that question once you comment on the rest of my post. You are not a High Inquisitor, so please do not behave like one.

 

[BasketCase]

<LURKER NOTICE>

Sweeeeeeet! Found another Global Warming thread.

Don't worry, I'll keep my mouth shut and just read for the time being.

 

[BasketCase]

Well, lurker mode sure didn't last long.

Reflection doesn't fully capture what I'm asking though. So IR is released by the surface and it goes back towards the atmosphere. It runs into the atmosphere but the atmosphere can release the heat in any direction. Why back towards the earth instead of towards outer space? This shouldn't have anything to do with wavelength. Or is it because I'm not properly distinguishing between radiation, convection, and conduction?

edit: grammar error

You're mostly spot-on. Referring to the boldface part: heat does generally radiate evenly--via all three mechanisms. The thing that keeps the Earth warm is the fact that a fraction of the heat goes back down; some of the energy of the Earth stays on/in the Earth for a longer time. If the planet had no atmosphere, almost all of the Sun's energy would bounce right back out into space immediately.


Edit: Whoops. Got it wrong--on planets with no atmosphere, the daytime side is sizzling hot and the night side is an ice cube. The amosphere slows down heat transfer and helps spread the heat all over the planet evenly.

 

[Mise]

EDIT: NASA - A Gloomy Mars Warms Up

EDIT2: after reviewing the article more closely it appears the warming of Mars seems to be more due to changes in dust distribution and coloration then solar cycles, but I'll leave the link.

Yes, exactly -- the mechanisms for Mars' warming and Earth's warming are completely different. And nothing to do with the Sun.

 

[ainwood]

your vocabulary seems rather limited!

I'll answer that question once you comment on the rest of my post. You are not a High Inquisitor, so please do not behave like one.

Moderator Action: He is from croatia. His english may not be as good as yours, so please make some allowances for that.

 

[knez]

my English is rather good (at least when I read)

anyway, or whatever, global warming as a consequence of human activities is just a theory with good marketing

1. Earths mechanisms are way to complex to draw any kind of definite conclusion(s)

2. about

all the rest NOT warming up

--> seriously, how can you know that (planets far from Sun aren't very afected by it's radiation, and effects on let's say Mercury (very close to the Sun, practicly no atmosphere) aren't something we can really measure/understand/interpret correctly

3. so let's assume you all are right, and global warming is consequence soley of human activities. No offense, but the things suggested for stoping it will just make things crappier (solar energy etc.)
as usually, the road to hell is paved with good intentions

 

[zxcvbnm]

my English is rather good (at least when I read)

anyway, or whatever, global warming as a consequence of human activities is just a theory with good marketing

1. Earths mechanisms are way to complex to draw any kind of definite conclusion(s)

2. about --> seriously, how can you know that (planets far from Sun aren't very afected by it's radiation, and effects on let's say Mercury (very close to the Sun, practicly no atmosphere) aren't something we can really measure/understand/interpret correctly

3. so let's assume you all are right, and global warming is consequence soley of human activities. No offense, but the things suggested for stoping it will just make things crappier (solar energy etc.)
as usually, the road to hell is paved with good intentions

1 and 2

How will action hurt us even if it wasn't caused by humans?

3

How?