climate change

matthew2008 · 18-06-2013 12:49pm #1

'climate change' has been occuring long before humans ever existed and long before humans ever produced a serious amount of greenhouse gases etc... what makes us so sure that its us thats causing the current climate change despite the fact that silmilar changes have occured throughout history without our help... is this another example of humans egocentric-ness??

ScumLord · 18-06-2013 1:19pm

matthew2008 wrote: »

'climate change' has been occuring long before humans ever existed and long before humans ever produced a serious amount of greenhouse gases etc... what makes us so sure that its us thats causing the current climate change despite the fact that silmilar changes have occured throughout history without our help... is this another example of humans egocentric-ness??

The climate is always changing and because it's always changing we do have some idea of how it changes naturally without human intervention. So it's not just a guess by scientists.

Humans have been having a big effect on the ecosystem for a long time. When the last ice age was drawing to a close humans in north America went on a killing rampage and wiped out many species using just stone tools, I believe it was the largest extinction event since the meteor that wiped out the dinosaurs. Animals that survived previous ice ages disappeared when humans were brought into the equation.

This isn't unique to humans either, other animals have been introduced to ecosystems and changed that ecosystem.

I think rather than us changing the ecosystem it's probably more a case of we're speeding up the change that would happen anyway. We are obviously having an effect.

The real problem with climate change is that we're effectively changing the environment away from one that's ideal for humans, rather than breaking the climate.

Capt'n Midnight · 18-06-2013 5:17pm

We own the nitrogen cycle. Humans fix more nitrogen than any other species.
We are responsible for most of the ozone hole.

You can argue about the CO2 from us vs. nature, but if you take into account desertification and desertification and changing the vegetation in most arable and many grassland areas andthe draining of bogs and clearing land by burning it's clear we are involved in other ways besides industrial emissions.

Even if you argue that the underlying cycle is natural we are the storm surge at high tide.

Yes volcanoes could out do us, but volcanoes can create mass extinctions so not really saying much,

ScumLord · 18-06-2013 5:30pm

Capt'n Midnight wrote: »

Yes volcanoes could out do us, but volcanoes can create mass extinctions so not really saying much,

The other thing about volcanoes is that destructive as they are, in the long run they enrich the area surrounding them, they create new land and they are a recurring natural process. Our effect is probably like a nonstop volcano.

matthew2008 · 18-06-2013 11:10pm

cheers i see what youse are saying, over-simplified we are simply adding to what is (could be) a natural occurence! iv no background in science as of now but am always sceptical when humans put us as a cause of somethig (positive or negative) as i said above iv always thought we (people) are incredibly egocentric

djpbarry · 19-06-2013 1:45pm

matthew2008 wrote: »

iv no background in science as of now but am always sceptical when humans put us as a cause of somethig...

Why? It must be obvious that humans can have a major ecological impact?

ScumLord · 19-06-2013 1:49pm

I'm more worried about the chemical imbalances we're making. Our overuse of nitrogen in farming is turning entire lakes into algae colonies coking out all other forms of life.

I always think of climate change as a big red cape keeping us distracted from the much more harmful things we're doing.

matthew2008 · 20-06-2013 2:07am

djpbarry wrote: »

Why? It must be obvious that humans can have a major ecological impact?

its obvious that humans can have an ecological impact, but not obvious how major this impact is/could be imo... espically when you hear about how serious some people say climate change is

fits · 20-06-2013 6:36am

ScumLord wrote: »

I always think of climate change as a big red cape keeping us distracted from the much more harmful things we're doing.

It is easy to think this when living in Ireland. Here, the effects so far have been minimal enough when compared with other parts of the world and we are lucky that the projections are pretty mild for Ireland also (although there is uncertainty of course)

Its much more noticeable in other areas such as the Mediterranean.

You are right of course though that there are other very serious issues also which attract less attention.

djpbarry · 20-06-2013 9:26am

matthew2008 wrote: »

its obvious that humans can have an ecological impact, but not obvious how major this impact is/could be imo...

This is the crux of the issue. Climate change isn't obvious, therefore it's not accepted as reality.

For example, the effects Deepwater Horizon oil spill were plain to see, so it's much easier for people to accept that oil spills are bad. However, increasing atmospheric carbon dioxide concentration, rising global mean temperature and rising sea levels are much more subtle changes that people can't see or feel the effects of and are therefore far less willing to accept there is anything to be concerned about.

Capt'n Midnight · 20-06-2013 9:52am

Climate change is hard to see here because we have a mild climate being downwind of a large ocean.
But we've had a lot of record matching events in recent years. Next time you are on holidays in a hot dry climate ask one of the older residents their opinion about climate change.

Places with real weather get our annual variation in hours
https://en.wikipedia.org/wiki/Spearfish,_South_Dakota

Spearfish holds the world record for the fastest temperature change. On January 22, 1943 at about 7:30 a.m. MST, the temperature in Spearfish was -20°C. The Chinook wind picked up speed rapidly, and two minutes later (7:32 a.m.) the temperature was +7°C . The 27°C rise in two minutes set a world record that still holds. By 9:00 a.m., the temperature had risen to 12°C. Suddenly, the chinook died down and the temperature tumbled back to -20°C. The 32°C drop took only 27 minutes

fits · 20-06-2013 11:16am

Capt'n Midnight wrote: »

Climate change is hard to see here because we have a mild climate being downwind of a large ocean.
But we've had a lot of record matching events in recent years. Next time you are on holidays in a hot dry climate ask one of the older residents their opinion about climate change.

Places with real weather get our annual variation in hours
https://en.wikipedia.org/wiki/Spearfish,_South_Dakota

Have to disgree with you about getting real weather. Ask anyone who takes a boat out on the west coast. We also had a spectacular temperature rise on Christmas day 2010

Justin1982 · 23-06-2013 2:47am

matthew2008 wrote: »

'climate change' has been occuring long before humans ever existed and long before humans ever produced a serious amount of greenhouse gases etc... what makes us so sure that its us thats causing the current climate change despite the fact that silmilar changes have occured throughout history without our help... is this another example of humans egocentric-ness??

Its simple enough really. An increase in Carbon Dioxide gas levels (as well as other green house gases) in the atmosphere causing the average temperature of the Earth to heat up. Thats a fact. Humans are releasing a ridiculous amount of Carbon Dioxide into the atmosphere. Thats a fact. Humans are warming up the atmosphere.

The doubt creeps in when climate scientists try to calculate by how many degrees the Earth on average will heat up over the next few years, how quickly, what the effects of that temp increase will be and how different regions will be affected.
But they have a good idea and their models/theories are getting better all the time.
You can bet your house on the average temperature of the earth not rising by more than 3 degrees over the next century. But you probably wont win I'm afraid.
Even if there was a 80% percent chance that scientists models were all wrong. Its really not worth the risk for humanity to take.

Lbeard · 23-06-2013 10:10am

Justin1982 wrote: »

Its simple enough really. An increase in Carbon Dioxide gas levels (as well as other green house gases) in the atmosphere causing the average temperature of the Earth to heat up. Thats a fact. Humans are releasing a ridiculous amount of Carbon Dioxide into the atmosphere.

Thats a fact.

Could you give a specific reason why Carbon Dioxide is any more a contributor to atmospheric warming than any other gas?

Preferably a peer-reviewed paper that explains the mechanism?

The doubt creeps in when climate scientists try to calculate by how many degrees the Earth on average will heat up over the next few years, how quickly, what the effects of that temp increase will be and how different regions will be affected.
But they have a good idea and their models/theories are getting better all the time.
You can bet your house on the average temperature of the earth not rising by more than 3 degrees over the next century. But you probably wont win I'm afraid.
Even if there was a 80% percent chance that scientists models were all wrong. Its really not worth the risk for humanity to take.

Justin, out of your own scientific curiosity, have you made any attempt to investigate this issue yourself?

djpbarry · 23-06-2013 11:15am

Lbeard wrote: »

Could you give a specific reason why Carbon Dioxide is any more a contributor to atmospheric warming than any other gas?

Preferably a peer-reviewed paper that explains the mechanism?

I believe Svante Arrhenius was the first to propose the mechanism:

http://www.bibnum.education.fr/files/Arrhenius-texte.pdf

Lbeard · 23-06-2013 11:27am

djpbarry wrote: »

I believe Svante Arrhenius was the first to propose the mechanism:

http://www.bibnum.education.fr/files/Arrhenius-texte.pdf

Svante was hand wavy. And it's not modern physics.

What's the modern physics explanation?

Capt'n Midnight · 23-06-2013 12:10pm

Lbeard wrote: »

Could you give a specific reason why Carbon Dioxide is any more a contributor to atmospheric warming than any other gas?

Preferably a peer-reviewed paper that explains the mechanism?

First off water vapour is the main contributor because of the amount of it in the atmosphere and the way clouds can reflect light back into space.

There is no question that we have changed the composition of the atmosphere. So following on from that the question is whether that change is good or bad.

A very important thing to remember is that most of the changes to the atmosphere have happened recently. Yes it started with the industrial revolution but most of the increase in CO2 has been in the last 50 years or so and presumably will continue to accelerate.

But it's complicated.
Aircraft are one of the ways we change the balance of the upper atmosphere.

http://www.eci.ox.ac.uk/research/energy/downloads/aviation-climatecare.pdf
Look at the graph on page 8
read the appendix on page 10

The level of understanding of each of these effects varies. The influence of carbon dioxide is well
understood, ozone and methane progressively less so, and contrails and cirrus clouds poorly
understood. Therefore the more effects that are included, the better the scientific picture, but the greater
the uncertainty in values adopted.

It's complicated as the gases from aircraft have different effects in different parts of the atmosphere. For instance they reduce methane.

The CO2 and Water Vapour emissions generally weigh more than the fully loaded aircraft on anything other than short hops.

Lots of stuff about the effects on cloud cover when aircraft were grounded after 9/11

There is no question that massive volcanic eruptions or asteroid impacts could change it more , but that's not stuff that happens every day.

The worry is about tipping points where there are changes that can't be easily reversed.
- fires in Indonesia , it's going to take a century of "green" palm oil to undo the CO2 released there
- Amazon rainforest changing to scrubland with semi-annual fires , happening in the west
- permafrost melting releasing methane
- methane hydrates release

There is a also a financial aspect that really isn't part of the science discussion without evidence, but it boils down the balancing of the best options slow down changes or compensate those most affected or other.

Lbeard · 23-06-2013 2:18pm

Capt'n Midnight wrote: »

It's complicated as the gases from aircraft have different effects in different parts of the atmosphere. For instance they reduce methane.

The CO2 and Water Vapour emissions generally weigh more than the fully loaded aircraft on anything other than short hops.

And what difference does removing methane from the upper atmosphere have?

Once you burn it, heat is released, its' temperature is conserved in the reaction. Now you've got hot CO2 and water. You've just gone an made the upper atmosphere hotter - I suppose you have taken some heat out turning the jet blades.

But what difference does it make if CO2 and water are in the upper atmosphere than methane?

There must be a precise mechanism that makes a difference. This is chemistry and physics, not biology where there a zillions of mechanisms we don't understand. The precise mechanism that differentiates CO2 from methane in global warming......What is it?

Justin1982 · 23-06-2013 11:08pm

Lbeard wrote: »

Could you give a specific reason why Carbon Dioxide is any more a contributor to atmospheric warming than any other gas?

Preferably a peer-reviewed paper that explains the mechanism?

Justin, out of your own scientific curiosity, have you made any attempt to investigate this issue yourself?

Its down to the fact that specifically green house gases are good absorbers/emitters of infrared radiation but not of radiation in the wavelength range of visible light and most radiation from the sun. So radiation gets through the atmosphere efficiently. Its absorbed by suface of earth fairly efficiently (apart from the poles). Same radiation is then re-emitted largely from surface of earth as infra-red radiation which doesnt get efficiently emitted back through the atmosphere as its absorbed by green house gases and turned largely into thermal energy of the atmosphere, ie. radiation energy from sun is largely turned into greater velocity of the green house gases, then gets passed to all other gases in atmosphere as green house gases bump into other gas molecules.

I'm not sure I need a peer reviewed paper. I can highlight a process you are probably very familiar with already

Probably the most convincing way of demonstrating how efficient green house gases is to consider a warm day with no clouds. Lets say it gets up to 30 degrees celcius. If later that night there is no clouds (a large accumulated green house gas) then temperature of atmosphere drops dramatically (possibly to < 10 degrees). On the other hand if clouds do develop before night fall then the temperature on the ground can remain quiet high (probably in the twenties).

I have taken enough of an interest to look into the science of global warming when I was in college. The thing that really clarified it for me though was a special documentary on Global Warming carried out by BBC a few years ago which had the aim of clarifying the issue for the public. They had scientists from both sides of the divide. They were all asked a series of questions and asked to take a position. All of them took the position that they were 100% sure of the science of global warming. They were 100% sure that humans were causing global warming. They differed on the exact effect of global warming, the extent of it, how different regions would be affected and the degree change in average world temperature. But as far as I remember it, the anti global warming camp at least agreed that the temperature of earth would rise by at least 1 degree celcius by end of century.

No one is sure of the exact consequences and degree of temperature rise or over how long. Thats where the researchers are still working and disagreeing.

But there is other problems associated with global warming. If temp rises by a high number then it causes temp of oceans to heat up and ice caps to melt completely. There is large amounts of green house gas locked up in frozen form on the oceans floor in various parts of the world which could be heated up to required temp to escape as gas and cause a negative feedback effect. Large amounts of green house gas being released, causing even more warming and even more release of currently frozen green house gases. The science of it is fairly well known at this stage and its known that this has happened in the past a long way back in the Earths past and caused a lot of the Oceans longest living species to die out.

The good news is that even if huge amounts of green house gas was released into atmosphere, if we stopped releasing more green house gas via human means then the Earth would naturally reabsorb the green house gases via various sinks (as its done in the past). Might happen over a long enough period though and its definitely possible for the Earth's atmosphere to reach high enough temp that it would be catastrophic for the human species in most parts of the world. A lot of ifs and buts of course. But all possible.

Lbeard · 24-06-2013 12:40am

Justin1982 wrote: »

Its down to the fact that specifically green house gases are good absorbers/emitters of infrared radiation but not of radiation in the wavelength range of visible light and most radiation from the sun. So radiation gets through the atmosphere efficiently. Its absorbed by suface of earth fairly efficiently (apart from the poles).

Okay, you're not thinking about this properly. Forget what anyone has said - clear your mind and build everything from the ground up again. Some rhetorical questions. When atoms and molecules absorb radiation what happens? Does it give the atoms/molecules momentum? Visible light is the higher energy end of the spectrum. When you look at the blue sky, and you know why it's blue, and even the sun appears yellow when it should be white. Is there something inefficient happening to this incoming radiation? If it's going somewhere, where is it going?

Same radiation is then re-emitted largely from surface of earth as infra-red radiation which doesnt get efficiently emitted back through the atmosphere as its absorbed by green house gases and turned largely into thermal energy of the atmosphere, ie. radiation energy from sun is largely turned into greater velocity of the green house gases, then gets passed to all other gases in atmosphere as green house gases bump into other gas molecules.

Are you dead certain about this? Have you looked at the spectrographs? Are they being interpreted correctly?

Is the absorption being interpreted correctly as having a thermal effect? Could some of the spectrum even be cooling the CO2.

What makes a greenhouse gas thermally any different from any other gas (water is a special case because of clouds). If the entire atmosphere was CO2, what colour would the sky be?

Probably the most convincing way of demonstrating how efficient green house gases is to consider a warm day with no clouds. Lets say it gets up to 30 degrees celcius. If later that night there is no clouds (a large accumulated green house gas) then temperature of atmosphere drops dramatically (possibly to < 10 degrees). On the other hand if clouds do develop before night fall then the temperature on the ground can remain quiet high (probably in the twenties).

You've got it a little wrong. Clouds are made of ice particles, they're not actually a gas. How they trap heat is when hot particles shoot up, they hit the snowflakes and come racing back down. The clouds also reflect IR back down.

The Green house effect is often wrong headly misunderstood. (I know this because I had very wrong headed misunderstandings of it). You have to think about the thermodynamics. Temperature is a measure of particle momentum - photons and atoms. If there are no clouds a hot atom, traveling straight up, will keep going until it loses all it's kinetic energy to potential energy do to gravity, it will then fall, regaining it's kinetic energy. Photons are a little different - the earths gravity is not strong enough to stop them escaping. You know all this, but have you really thought about it?

I have taken enough of an interest to look into the science of global warming when I was in college. The thing that really clarified it for me though was a special documentary on Global Warming carried out by BBC a few years ago which had the aim of clarifying the issue for the public. They had scientists from both sides of the divide. They were all asked a series of questions and asked to take a position. All of them took the position that they were 100% sure of the science of global warming. They were 100% sure that humans were causing global warming. They differed on the exact effect of global warming, the extent of it, how different regions would be affected and the degree change in average world temperature. But as far as I remember it, the anti global warming camp at least agreed that the temperature of earth would rise by at least 1 degree celcius by end of century.

Television is not the best source for science.

One thing you'll find interesting if you look into this yourself, is many of the people on both sides of the "debate", say and write stuff that contradicts basic science. The hand waving is awful. Some will say its cosmic rays - but of course they won't offer the numbers.

No one is sure of the exact consequences and degree of temperature rise or over how long. Thats where the researchers are still working and disagreeing.

Is it meaningful or meaningless - think about the other questions and then think about this one.

A lot of ifs and buts of course. But all possible.

Look into the bits you should be able to understand quite well. You're in for a surprise..

You understand quantum mechanics, if a climate scientist waved their hands at you and told you there was some hidden unknown mechanism, how credulous would you be?

Capt'n Midnight · 24-06-2013 9:13am

Lbeard wrote: »

Is the absorption being interpreted correctly as having a thermal effect? Could some of the spectrum even be cooling the CO2.

What does this mean ?

Check out Stefans Law , fourth power of absolute temperature and all that

Lasers are rare, in nature you generally don't get amplification, and doubling the energy by combining photons is also very rare so no so many green lasers in nature.

The Green house effect is often wrong headly misunderstood. (I know this because I had very wrong headed misunderstandings of it). You have to think about the thermodynamics. Temperature is a measure of particle momentum - photons and atoms. If there are no clouds a hot atom, traveling straight up, will keep going until it loses all it's kinetic energy to potential energy do to gravity, it will then fall, regaining it's kinetic energy. Photons are a little different - the earths gravity is not strong enough to stop them escaping. You know all this, but have you really thought about it?

???

escape velocity is a tad higher than the thermal energy of an atom, the nearest you'll get is having an atom in the upper atmosphere where the solar wind might strip if off. And it's a process that takes billions of years even with Venus so close to the sun and Mars with lower gravity.

djpbarry · 24-06-2013 9:44am

Lbeard wrote: »

Svante was hand wavy. And it's not modern physics.

Eh? Arrhenius’ equation is still widely used (and still remarkably accurate)?

Lbeard wrote: »

The precise mechanism that differentiates CO2 from methane in global warming......What is it?

I’m not entirely sure what you mean – the mechanism is the same. Both carbon dioxide and methane absorb energy in the infra-red, which causes molecular vibrations.

Lbeard · 24-06-2013 3:58pm

Capt'n Midnight wrote: »

What does this mean ?

Check out Stefans Law , fourth power of absolute temperature and all that

Yes, because atom momentum is proportional to the photon momentum from the same body.

Lasers are rare, in nature you generally don't get amplification, and doubling the energy by combining photons is also very rare so no so many green lasers in nature.

Lasers are rare but photons are not. You haven't really thought this through, have you.

escape velocity is a tad higher than the thermal energy of an atom, the nearest you'll get is having an atom in the upper atmosphere where the solar wind might strip if off. And it's a process that takes billions of years even with Venus so close to the sun and Mars with lower gravity.

The thermal energy of an atom is in its' momentum. If you through a ball in the air, it will slow down, losing it's kinetic energy to potential energy, it will eventually stop. This is what happens to water molecules, they lose their kinetic energy to a point they can condense into clouds.

Atoms generally cannot get enough kinetic energy to escape into space, but for photons it's easy. We lose heat to outer space through photons.

Lbeard · 24-06-2013 4:08pm

djpbarry wrote: »

Eh? Arrhenius’ equation is still widely used (and still remarkably accurate)?

Remarkably accurate as in whoever uses the equation gets the same answers as anyone else who uses it.

I’m not entirely sure what you mean – the mechanism is the same. Both carbon dioxide and methane absorb energy in the infra-red, which causes molecular vibrations.

Your explanation, I'm not going to say is completely incorrect, and it's an explanation lots of people use. Unfortunately it's mangled. When a molecule absorbs radiation, its' electrons move to a higher energy level - it doesn't vibrate. Explaining heat in terms of atoms vibrating is misleading.

Capt'n Midnight · 24-06-2013 4:23pm

Molecules can store vibrational and rotational energy too.
And apart from the Nobel gases the vast bulk of the atmosphere is comprised of molecules.

http://en.wikipedia.org/wiki/Molecular_vibration

Also any kinetic energy an atom/molecule has would be shared very quickly due to collisions. Mean free path , random walk and all that. (distance travelled after n collisions is only square root of n )

djpbarry · 24-06-2013 4:53pm

Lbeard wrote: »

Remarkably accurate as in whoever uses the equation gets the same answers as anyone else who uses it.

No, remarkably accurate as in it predicts experimental observations extremely well.

Lbeard wrote: »

Your explanation, I'm not going to say is completely incorrect, and it's an explanation lots of people use. Unfortunately it's mangled. When a molecule absorbs radiation, its' electrons move to a higher energy level - it doesn't vibrate.

It most certainly does. Absorbing energy can cause atoms in a molecule to move periodically relative to each other (vibrate).

Lbeard · 24-06-2013 5:00pm

Capt'n Midnight wrote: »

Molecules can store vibrational and rotational energy too.
And apart from the Nobel gases the vast bulk of the atmosphere is comprised of molecules.

http://en.wikipedia.org/wiki/Molecular_vibration

Yeah. I thought someone would say that. In terms of molecules absorbing radiation, to say their vibrating, as in there's a thermal effect is misleading or wrong.

Also any kinetic energy an atom/molecule has would be shared very quickly due to collisions. Mean free path , random walk and all that.

Yes. But the random walk can take a particle high in the atmosphere as well as low. And in terms of collisions, you can think of the net direction of momentum over the net movement of a particle. Water molecules in clouds are colder than at the ground, but they store a lot of energy in potential energy. The net energy of water molecules in clouds is greater than water molecules near the ground. Because of gravity, energy content and temperature are not proportional to each other.

(distance travelled after n collisions is only square root of n )

This gets a lot more tricky with an atmosphere. It's even complicated when considering neutrons thermalising in a solid of uranium or plutonium. It requires quite a bit of modelling to know what you're getting.

ScumLord · 24-06-2013 5:33pm

Capt'n Midnight wrote: »

The worry is about tipping points where there are changes that can't be easily reversed.
- fires in Indonesia , it's going to take a century of "green" palm oil to undo the CO2 released there
- Amazon rainforest changing to scrubland with semi-annual fires , happening in the west

It's not the first time in human history we've deforested large parts of the world. Europe probably had a lot of forrest at one stage and we removed most of it over a fairly short period of time. Not as quick as today but is there any way we can find evidence of how that affected the world? I'm sure the same happened throughout the civilised world of the time.

Maybe removing that forrest mass wasn't as much of a strain because there was so much other forest throughout the world?

fits · 24-06-2013 5:48pm

ScumLord wrote: »

Maybe removing that forrest mass wasn't as much of a strain because there was so much other forest throughout the world?

The human population was also much lower and the industrial revolution had yet to begin.

Lbeard · 24-06-2013 6:12pm

fits wrote: »

The human population was also much lower and the industrial revolution had yet to begin.

These kind of arguments derail the whole discussion. To claim humans have an influence on climate temperature, you need a precise mechanism.

Otherwise it's like claiming we're being punished by some magic force for not eating organic yogurt, and cous cous.

fits · 24-06-2013 6:21pm

Lbeard wrote: »

These kind of arguments derail the whole discussion. To claim humans have an influence on climate temperature, you need a precise mechanism.

Otherwise it's like claiming we're being punished by some magic force for not eating organic yogurt, and cous cous.

There is a direct link between human population and the industrial revolution, and greenhouse gases in the atmosphere.

Are you questioning the fact that the proportion of CO2 in the atmosphere is higher than it was pre the industrial revolution, or are you dismissing the greenhouse effect completely?

climate change

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