Monday, December 09, 2013

The American Chemical Society on Climate Change

Nonono, not the policy statement, well there is that, but a bunch of resources that ACS has put out there a climate science tool kit for folks to learn from and use, put together by a top notch working group with support from ACS leadership.  As part of the effort ACS held a meeting to brief staff about how to approach climate communication

When a conversation turns to climate change, do you know the basic science to take part? Do you understand the far-reaching impacts of climate change and how it's affecting you today?  Learn the answers to these questions and more.

There are three professionally illustrated PowerPoint presentations which can be used in toto or from which slides can be select:  One for the public, one for educators and one for industry professionals (Powerpoint downloads).  And yes, a plug for Skeptical Science
This site is very helpful for a non-climate scientist who wants to stay current with the literature on global warming and climate change. As the description says, many of the posts take to task the published arguments of global warming skeptics and these rebuttals help to sharpen one’s climate science reasoning and logic. Sometimes the comments elicited by these posts also demonstrate the futility of getting into a “tis-taint” argument, if you are trying to engage someone or a group in a climate science conversation.
Eli would encourage everybunny to rummage about the site a bit, but to get started here is the part analogies for the greenhouse effect, which starts with the usual that the mechanism is not the same as a greenhouse.  Well, Eli has thought about this a bit, briefly put there are three methods of heat transfer, radiation, convection and conduction.  The atmosphere is a lousy conductor and so is glass, so that plays no role.  Greenhouses work by limiting convection, heat transfer by mass flow.  The greenhouse effect works by limiting radiation, heat transfer by photon flow, so there really is a way in which they are the same, the both limit the rate of heat transfer from a hotter to a colder place, but they just affect different mechanisms of heat transfer.  Be that as it may, it has become a bit of a distraction to make that analogy.
A different analogy is the atmosphere acting like a blanket. Think of yourself under a blanket in a cold room. You represent the Earth, a warm body giving off energy, what we usually call “heat”. The blanket represents the atmospheric layer of greenhouse gases. As the heat energy leaves your body it is absorbed by the innermost fibers of the blanket. As they give off some of that energy, they warm the next layer of fibers and so on and on until some energy leaves the outermost cold fiber layer and is lost to the room. Just as the sun continually warms the Earth, you continually produce energy through respiration. You will finally reach a balance where the energy leaving the blanket is equal to the energy you produce and your skin will remain at a constant temperature, just like the surface of the Earth.
Among the Earth’s blanket of greenhouse gases, carbon dioxide is the one you probably hear about most often, because it is increasing in the atmosphere as we burn a great deal of coal, oil, and gas for energy. Besides carbon dioxide, greenhouse gases include water vapor, methane (natural gas), nitrous oxide (from fertilizer use), and chlorine- and fluorine-containing gases used in air conditioning units and as solvents. Adding more greenhouse gas to the atmosphere increases the amount of absorption and release of heat energy required for the energy from the surface to reach the top of the atmosphere and go off into space.
In our blanket analogy, this is like putting on another blanket, so there are more layers of blanket fibers for the energy to pass through to reach the top. The old energy balance is upset and after a time a new one takes its place with you feeling warmer than before. This is what is occurring for the Earth as well. The increased amounts of greenhouse gases our activities are adding to the atmosphere have upset the balance that was in place since the end of the last ice age and the Earth is getting warmer than it was before we started burning large amounts of fossil fuels.
 Eli had that discussion a long time ago.  Atmoz is missed.

10 comments:

SteveS said...

IMHO John Tyndall nailed it way back:

"As a dam built across a river causes a local deepening of the stream, so our atmosphere, thrown as a barrier across the terrestrial rays, produces a local heightening of the temperature at the Earth’s surface."

Why not stick with the original (and best) analogy?

Anonymous said...

Anon-101a here:

The analogy of the blanket is still 100% fine. A blanket stops radiation too, remember: it's opaque to IR.

Where it is broken is where the analogies are taken partially.

Your body = earth.
The room = the universal vacuum of space

(note that this is the thing that is never considered explicitly and where ignoring it causes the analogy to break down)

Blanket = thing that blocks heat transfer from Body to Room.

A thin blanket stops (almost) 100% of energy transfer to the room and internalises it instead.

The thin blanket of the greenhouse gasses block (almost) 100% of the energy transfer to space and internalises it instead.

Anonymous said...

"The analogy of the blanket is still 100% fine. A blanket stops radiation too, remember: it's opaque to IR."

Your ceiling is opaque to IR, and does radiate you with some energy, just not enough.

Blankets work by slowing the convective loss from your body, not because they radiate.

Continually kick the blanket up to allow convective exchange and you experience the reduced effectiveness of the blanket.

In the same way, kick the atmosphere with convective exchange, and the imposed radiative forcing is also less effective.

Martin Vermeer said...

SteveS,

the whole quote is worth reading:

"No doubt, therefore, can exist of the extraordinary opacity of this substance to the rays of obscure heat; and particularly such rays as are emitted by the earth after it has been warmed by the sun. It is perfectly certain that more than ten per cent, of the terrestrial radiation from the soil of England is stopped within ten feet of the surface of the soil. This one fact is sufficient to show the immense influence which this newly-discovered property of aqueous vapours must exert on the phenomena of meteorology.

This aqueous vapour is a blanket more necessary to the vegetable life of England than clothing is to man. Remove for a single summer-night the aqueous vapour from the air which overspreads this country, and you would assuredly destroy every plant capable of being destroyed by a freezing temperature. The warmth of our fields and gardens would pour itself unrequited into space, and the sun would rise upon an island held fast in the iron grip of frost. The aqueous vapour constitutes a local dam, by which the temperature at the earth's surface is deepened: the dam, however, finally overflows, and we give to space all that we receive from the sun.

The sun raises the vapours of the equatorial ocean; they rise, but for a time a vapour screen spreads above and around them. But the higher they rise, the more they come into the presence of pure space; and when, by their levity, they have penetrated the vapour screen, which lies close to the earth's surface, what must occur ?

It has been said that, compared atom for atom, the absorption of an atom of aqueous vapour is 16,000 times that of air. Now the power to absorb and the power to radiate are perfectly reciprocal and proportional. The atom of aqueous vapour will therefore radiate with 16,000 times the energy of an atom of air. Imagine then this powerful radiant in the presence of space, and with no screen above it to check its radiation. Into space it pours its heat, chills itself, condenses, and the tropical torrents are the consequence. The expansion of the air, no doubt, also refrigerates it; but in accounting for those deluges, the chilling of the vapour by its own radiation must play a most important part. The rain quits the ocean as vapour; it returns to it as water. How are the vast stores of heat set free by the change from the vaporous to the liquid condition disposed of? Doubtless in great part they are wasted by radiation into space. Similar remarks apply to the cumuli of our latitudes. The warmed air, charged with vapour, rises in columns, so as to penetrate the vapour screen which hugs the earth; in the presence of space, the head of each pillar wastes its heat by radiation, condenses to a cumulus, which constitutes the visible capital of an invisible column of saturated air."

(http://archive.org/details/noticesproceedi00britgoog)

They don't make them like that any more

SteveS said...

Agreed Martin - he got the mechanism pretty much right first time! And he had an awesome beard...

Why reinvent the wheel (or invent the blanket) when the dam analogy is much more informative and came from the discoverer himself?

Anonymous said...

Anon-101a here:

"Your ceiling is opaque to IR"

Yup.

And you try sleeping outside without even a bit of cardboard above you.

But having a blanket makes a difference, just as having a roof as opposed to just cardboard or canvas above you makes a diffference.

Anonymous said...

Anon-101a here

By the way, that roof doesn't block any of the IR coming from the body parts covered by the thinnest of blankets or a sheet.

It blocks the IR coming from the top of the blanket or sheet. But not from the body underneath it.

So the claim: "Your ceiling is opaque to IR" does nothing to the IR coming from the body underneath the blanket.

Does it.

So unless you want to claim it is irrelevant to the "blanket of greenhouse gasses is like a blanket on your body" analogy, it was a lie by misdirection.

Wasn't it.

Anonymous said...

Whut?

Your blankie keeps you warm because it stops your body heat from escaping through convection.

Anonymous said...

Anon-101a here:

It blocks IR too.

All that IR from your body: blocked by the blankie.

But maybe you need to pop along to the top of the thread and start reading the posts from the beginning, lest you get even more confused, annonny.

Anonymous said...

Anon101-a here:

"Blankets work by slowing the convective loss from your body, not because they radiate."

Blankets stop ALL convection from your body underneath it.

Blankets stop ALL radiation loss from your body underneath it.

Since space has no convection, the blanket of greenhouse gasses stop ALL convection from the earth and all IR from the surface that is covered by an optically thick blanket of GHGs.

So the analogy is still 100% fine.