Anthropogenic global warming

[HMS_Beagle]

As I understand, temperatures rise or fall depending on the balance between incoming radiation and outgoing radiation from the earth to outer space & the sun. Before sunrise, the temperature usually continues to fall toward the day's low. At which point, the balance is zero (incoming = outgoing). I'm ignoring the lag of the temperature toward the balance. After that, the balance is to the incoming radiation (incoming > outgoing). The temperature continues to rise until sometime in the afternoon, when again incoming = outgoing. Thereafter, the temperature declines toward tomorrow's low because incoming < outgoing.

Am I right it's usually a question of radiation balance? Of course the reality is really complicated. There may be a cold front sweeping down. Or it's rather cloudy. Rainy, etc.


I don't know for sure, but it seems to me that the CO2 component of the atmosphere has a minor role in determining the radiation balance, on the basis of those graphics that I've posted. And it's likely to remain minor for years.

You're still missing the big picture.

All the nights and days and mornings and evenings of the whole planet average out. When it's day here it's night on the other side, remember?

If everything remains constant then the radiation balance of the planet would stay constant. However, when you add CO2 to the atmosphere you get less IR radiation being returned to space and the planet gets warmer. This has been empirically measured and confirmed by satellite data over the last 50 years as well as all the temperature proxies we have here on Earth. The change in climate at specific locations on the Earth is going to be very chaotic, often hard to predict but the overall temperature average of the whole planet is increasing.

It's still just basic physics.

[Jonathandavid]

Am I right it's usually a question of radiation balance?

No, that is not correct. The incoming and outgoing radiation of the earth roughly balances out. Ofocurse, this is measured on timescales much larger than a single day, to which you are referring. Climate change is not measured in a single day/night cycle.

If you read back my first post, you'll see that the earth contributes most in warming the atmosphere, and that some of the atmosphere's energy is lost to space in the form of longwave radiation. Greenhouse gases absorb IR radiation and thus warm the lower atmosphere, but as warm bodies give off IR radiation, this energy is also directed to the upper atmosphere again, and some of it is lost, most is trapped, etc. etc.

If you'd follow a particular 'parcel' of energy from the sun through the earth's climate system, it will go back to space. Both the incoming and outgoing radiation of the earth is about 342 W/m2. The net gain or loss is actually close to zero. The thing to remember here is that very small changes can already lead to noticeable climate change and that most climate change is due to the distribution of energy in the atmosphere and oceans. Also, a short dip in outgoing power followed by renewed balance means that the earth's total heat will have risen without falling. Both the article and book I referenced earlier go into more detail about this. You can also look up 'radiation budget earth' on google pictures and get a nice overview.

What you call a 'minor contribution of CO2' is actually illustrated in these diagrams: of the incoming solar (shortwave) radiation, only a small part is absorbed immeditately by the atmosphere. Most goes through to the earth's surface, where it is converted to heat, causing the earth to give off longwave radiation. It is this radiation that gets trapped.

[HMS_Beagle]

TS, maybe it would be clearer to you by understanding that the spectrum of terrestrial radiation leaving the Earth is not the same as the solar radiation hitting the planet. In the diagram below the large yellow shape is received solar radiation, the same graph you posted above. The green shape on the right is the outgoing terrestrial radiation.

ocean33.gif

Notice that the terrestrial outgoing energy is much more at the wavelengths absorbed by atmospheric CO2.

HTH.

[Jonathandavid]

One remark about that graph: I think it gives the outgoing radiation from the top of the atmosphere, where the CO2 has already absorbed certain wavelengths, i.e. the dip at abt. 15 microns.

The temperature values given in the text seem a bit high.

[Truthseeker]

TS, maybe it would be clearer to you by understanding that the spectrum of terrestrial radiation leaving the Earth is not the same as the solar radiation hitting the planet. In the diagram below the large yellow shape is received solar radiation, the same graph you posted above. The green shape on the right is the outgoing terrestrial radiation.

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I find it hard to interpret. Flux density (flux divided by the wavelength??) is not something I'm familiar with. Also, putting things on the log-log graphing makes it difficult to see if there's a radiation balance, I guess.

And guess what, I forgot about the heat from underground. I can't remember if it is supposed to be negligible or just minor compared to solar influx.

[phank]

The big picture isn't that hard to grasp, and I think it needs to be grasped before we start getting into the details. The idea is, the earth is warmed by the sun. For any fixed composition of the earth and its atmosphere, there is an equilibrium - as much energy is radiated away as is received, so the global temperature is constant. If this equilibrium is upset in one direction, we would soon get snowball earth because heat radiated away exceeds heat received. In the other direction, we get cinder earth, because not enough heat is being radiated out. The equilibrium historically has been in about the middle, the temperature range in which the biosphere evolved.

Now, it doesn't take a whole lot of change to move the equilibrium in one direction or the other. The most influential change, of course, is a change in the sun's output. But if the sun is constant, then the next biggest influence is water vapor. If water vapor is also constant (on average worldwide), we move to the next most influential, etc. In actuality, CO2 is well down the list in terms of relative influence. What makes CO2 important is that the concentrations of CO2 in the atmosphere are not constant (again on average worldwide and year round). The concentration of CO2 in the atomosphere today is the highest it has been in the last 800,000 years. And since CO2 does have a (relatively small, since it's still a trace gas) greenhouse effect, steadily increasing concentrations result in moving the equilibrium of the planet in the warmer direction. The earth is retaining slightly more of the sun's radiation than it used to.

Sometimes I imagine a sink with water both pouring out the faucets and running down the drain. What we're doing as we burn fossil fuel is, we're plugging the drain a bit. The water level in our sink is rising. It's rising very slowly (estimated 2 degree increase over the next century), but it's rising.

[Truthseeker]

Phank, thank you. Do you know that our volcanoes have injected far, far more junk into the atmosphere than we collectively have since the beginning of the Stone Age? Lots more CO2, too. We did come close to having an ice world, well, sorta. We also had a much warmer world--not a cinder world, thankfully?? That meteorite that did in the dinosaurs didn't quite do the job of making Earth a cinder world forever. Have you completely accounted for these events, yes?

[phank]

Phank, thank you. Do you know that our volcanoes have injected far, far more junk into the atmosphere than we collectively have since the beginning of the Stone Age? Lots more CO2, too. We did come close to having an ice world, well, sorta. We also had a much warmer world--not a cinder world, thankfully?? That meteorite that did in the dinosaurs didn't quite do the job of making Earth a cinder world forever. Have you completely accounted for these events, yes?

You are quite correct. Over VERY long periods of time, we have seen eras of very active volcanism, and these have indeed altered global climate for long periods. We have also seen moderate variations in the sun's output, and there is some evidence of times in the distant past when we did have "snowball earth", when the whole planet was iced over. This is generally considered to have been a time of lower insolation. I'm not sure that bolide impacts have had particularly long-term climate effects, depending on what we mean by "long". If we're talking about centures here, then yes, such impacts can produce the equivalent of "nuclear winter."

There have also been other ways that the thermal equilibrium has been shoved around. Life itself has drastically altered the composition of our atmosphere.

So we need to understand that we're not talking drastic here. AGW is modeled to be very mild compared to these past eras and events, even at the high end of its predicted range. If another supervolcano happens along, AGW will be so insignificant the human survivors, if any, won't particularly care about it. The underlying subtext here (which we rarely see presented) is that people have crammed themselves into every livable part of the planet, and are overfishing, overmining, overdrawing aquifers, etc. to fill even more. This "living at the edge" naturally exacerbates any climate change, because ANY change is going to make SOME part of the planet less livable. If the human population were, say, only 10% of what it is today, nobody would much care about a 2 degree temperature increase over a century. They'd just move.

[HMS_Beagle]

Do you know that our volcanoes have injected far, far more junk into the atmosphere than we collectively have since the beginning of the Stone Age? Lots more CO2, too.

In the Stone Age we didn't have a global population of over 7 billion people and an extremely fragile food supply chain that can't withstand more than the slightest perturbations in climate. In the Stone Age we didn't have more than 4 billion people living in coastal areas within 20 miles of the oceans who will be severely impacted by sea level rise.

Just because natural events long ago caused major climate change doesn't much help the problems we're bringing on ourselves now.

[Jonathandavid]

As I said earlier, since industrialization the CO2 concentration of the atmosphere has increased from 280 ppm to 400 ppm (see Sloan & Wolfendale 2013, reference given earlier). Volcanoes were around both before and after industrialization, so there is something going on here.

The difference, of course, is in when you start to measure. Naturally volcanoes have spewed out a lot of CO2 since ancient times, but that was not the beginning of anthropogenic climate change. That only become noticeable in the order of decades ago, when the CO2 produced by us was significantly more than that produced by volcanoes.

But why not see what the experts on volcanology have to say about this? The US Geological Survey has the following text on its website:

Volcanic Versus Anthropogenic Carbon Dioxide" written by USGS scientist Terrence M. Gerlach.

Volcanoes cannot explain the current warming trend.

[Truthseeker]

As I said earlier, since industrialization the CO2 concentration of the atmosphere has increased from 280 ppm to 400 ppm (see Sloan & Wolfendale 2013, reference given earlier). Volcanoes were around both before and after industrialization, so there is something going on here.

The difference, of course, is in when you start to measure. Naturally volcanoes have spewed out a lot of CO2 since ancient times, but that was not the beginning of anthropogenic climate change. That only become noticeable in the order of decades ago, when the CO2 produced by us was significantly more than that produced by volcanoes.

But why not see what the experts on volcanology have to say about this? The US Geological Survey has the following text on its website:

Volcanic Versus Anthropogenic Carbon Dioxide" written by USGS scientist Terrence M. Gerlach.

Volcanoes cannot explain the current warming trend.

I stand corrected re volcano CO2 contributions compared to A-generated atmospheric CO2 --my dance when someone catches a whopper of mine

But volcanoes did produce global cooling many times, as shown here http://www.geology.sdsu.edu/how_volc...e_effects.html <<<search for "examples of global cooling" (quotation marks not included)

[Jedidiah]

How much carbon is put into the air each year from the burning coal mines under what was once Centralia, Penn? They have been burning since 1962.

[Jonathandavid]

The Eos article gives many estimates for CO2 emissions, although not for specific locations. But you can get an idea about the order of magnitude.

As for the influence of volcanoes on earth's past climate, my subjective estimate is that they have been the single most influential forcing. Volcanoes were the most likely cause for the melting of the 'snowball earth' and they are a part of the so-called BLAG hypothesis, which is about climate change on extremely long timescales. I'm sure volcanoes have significantly influenced climate. They just can't explain the current warming.

Note that global warming due to volcanic activity assumes the greenhouse effect.

[TheLurch]

But volcanoes did produce global cooling many times, as shown here http://www.geology.sdsu.edu/how_volc...e_effects.html <<<search for "examples of global cooling" (quotation marks not included)

Volcanoes produce short-term cooling due to the aerosols they pump into the upper atmosphere, which reflect sunlight. So, for example, the largest eruption of last century (Pinatubo) reduced temperatures for about five years afterwards before the warming trend kicked in again. Other volcanic eruptions are thought to have triggered the Little Ice Age.

Eruptions of that size do not significantly alter the CO2 levels in the atmosphere (as your recent reading indicated). Very large volcanic events or extended periods of volcanic eruptions, however, can. Elevated volcanic activity is thought to have pulled the planet out of its "snowball earth" periods, and the warming (and ocean acidification) triggered by the eruptions that created the Siberian Traps is thought to have contributed to the end-Permian mass extinction, more commonly known as the great dying.

If any of that interests you, let me know, and i'll find some links for you.

[shunyadragon]

Friends

Greenland is one of the interesting benefactors of Global warning, where the effects are probably greater then any other place in the world.

Positive Effects

In southwestern Greenland, for example, the grass-growing season gets longer each year, boosting productivity for some 60 sheep farms now established in the region. Up to 23,500 sheep and lambs are slaughtered annually.

Dairy cattle have recently been reintroduced, and a government-led project is expected to yield 29,058 gallons (110,000 liters) of milk annually, according to the new report.

Locally grown potatoes have appeared in supermarkets, alongside broccoli and other vegetables never before cultivated in Greenland.

Commercial fishermen are anticipating bumper cod catches after the fish recently moved north into Greenland's waters. Halibut are also increasing in size.

Read on, it also addresses the negative effects.