If co2 forcing is so powerful... then how do you explain levels 10 times higher than today on a frozen world?

Question

450 Million years ago Earth was at it coldest point in the past 1 Billion years and Co2 levels were 10 times what they are today. This seems to go against current Co2 forcing theories supported by AGW believers .

Answer 1

In high enough levels Co2 blocks light from entering then earths atmosphere.  It could cause global warming then an ice age.

Answer 2

Bob326: nice retort to Bob, re: volcanic dust, just one problem there is nothing about volcanic dust in Bobs comment

Answer 3

The theory goes like this:  Those high levels were at the *end* of the global ice age.  The *cause* of the global ice age was the high weathering rate of silicates that drew down the atmospheric CO2 concentration, reducing the radiative forcing from CO2, allowing the planet to cool, resulting in the global ice age.  Once the planet was completely glaciated, silicate weathering essentially ceased, allowing volcanic CO2 to build up in the atmosphere over some 100 million years.  The increasing CO2 lead to a greater radiative forcing, warming the planet enough to stop the ice age.  However, since the planetary albedo was so high due to all the ice, it took a relatively high concentration of CO2 to trigger the end of the ice age.  But the key point in the theory is that it was the radiative forcing from CO2 that ended the ice age.  

This is "snowball earth" 101.  I suggest you go to

www.snowballearth.org

and read the material for students to get more details.  In short, there is nothing inconsistent with high CO2 levels in the paleo record occurring at roughly the same time as global glaciation.  Furthermore, that these global ice ages were both triggered and ended by changes in the composition of the atmosphere, in particular the radiatively important trace gases CO2 and CH4, ought to give you pause for thought.

Edit:  Bob326, if you didn't read the information then how do you know it isn't relevant, or that it is highly speculative?  I would submit you dislike the idea because it confirms what all scientists who understand planetary atmospheres already know, that radiative forcing from trace gases is critical in determining global mean temperatures.

Answer 4

Conditions were so different then, no comparison is possible.  Solar radiation is different, the amount of water vapor in the air was different, etc.

The Earth was _very_ hot 500 million years ago.  Scientists believe that reduction in CO2 caused it to cool 450 million years ago, by converting CO2 to O2, and making the first breathable atmosphere.  Details here.

http://www.sciencedaily.com/releases/200...

Do you honestly think scientists don't know all about that distant history?  And most all of them still say this warming is mostly due to CO2.

EDIT - water vapor CANNOT be a forcing for warming.  Excess water vapor falls out as precipitation.

http://www.sciencedaily.com/releases/200...

And neither is the Sun.  We KNOW that, because we measure it.

"Recent oppositely directed trends in solar

climate forcings and the global mean surface

air temperature", Lockwood and Frolich (2007), Proc. R. Soc. A

doi:10.1098/rspa.2007.1880

http://www.pubs.royalsoc.ac.uk/media/pro...

News article at:

http://news.bbc.co.uk/1/hi/uk/6290228.st...

None of the arguments above can possibly be correct unless scientists are dumb or liars.  If you believe that, you can believe anything, I suppose.

Answer 5

Bob said:

"Conditions were so different then, no comparison is possible. Solar radiation is different, the amount of water vapor in the air was different, etc. Possibly the biggest factor is that the air was not as transparent due to intense volcanic dust."

Lets see:

Solar-- The sun was weaker during the Ordovician-Silurian ice age, but it was of similar strength during the Ordovician greenhouse conditions that preceded the ice age.

Water vapor-- different from what? The greenhouse conditions of Ordovician? Of course it was, the temperature was much lower. Different from now? Reference please.

Volcanic dust--are you suggesting that increased volcanic dust was a driver of the transition to icehouse conditions? That would mean more volcanic activity directly prior to the transition, which is a new theory to me. So again, reference please.

I agree that land mass location, ocean circulation, and overall conditions were different then, but don't make up things to prove that point.

Bob said:

"The Earth was _very_ hot 500 million years ago. Scientists believe that reduction in CO2 caused it to cool 450 million years ago, by converting CO2 to O2, and making the first breathable atmosphere. Details here."

Weathering and plant life did cause a decrease in atmospheric CO2...to roughly 4400ppm.

Bob then said:

"Do you honestly think scientists don't know all about that distant history?"

I wouldn't say that we know "all about distant history". Rather that we are pretty sure that we have a good idea of some things about distant history.

EDIT:

Bob,

Water vapor as a forcing--it can be only if water vapor production remains as a constant or increasing rate. Its a point a lot of people miss, so I don't fault you. However, absolutes and blanket statements are almost never a good idea.

And regarding the Lockwood and Frohlich: The L&F paper uses TSI, UVI and cosmic ray trends to conclude that it is likely that those three effects have not influenced the climate much during the past 30 years, but that is NOT the same thing as your conclusion:

"And neither is the Sun. We KNOW that, because we measure it."

The L&F paper implies several times that there is still much uncertainty with regards to the sun's influence on climate. We just don't know enough about the sun's role to say conclusively.

And Richard Mackey recently gave a presentation at the EGU meeting on different solar forcings (he is preparing a paper for review)--he seems to think that irradiance isn't as big of player as the Sun’s electromagnetic field and material output, and the gravitational changes (I can provide a copy of his presentation if you wish). All of whom's influences are not really well understood. So again, absolutes and blanket statements, especially in science, are never a good idea.

Oh, and Andrew Q, Bob originally mentioned volcanic dust, but he must have changed it. The quote I have from him above is what he originally said.

Edit2:

gcnp,

I did not read the site you linked to, but it seemed like an odd title for the current conversation. The Ordovician-Silurian ice age was icehouse conditions not snowball earth conditions. The theory behind snowball earth is highly speculative with very little evidence. Beyond that, the last snowball earth (supposedly) was over 600mya--in a different eon completely from what we are talking about.

Edit3:

gcnp,

Because I have researched the "snowball earth" theory and I know it is highly speculative.

Also, it is still irrelevant to the topic of this thread, being that the last theorized snowball earth was over 100 million years prior to the Ordovician-Silurian ice age, which is the period in question.

You say:

"that radiative forcing from trace gases is critical in determining global mean temperatures."

That is how the greenhouse effect works. I don't doubt that the greenhouse effect exists.

And I took a look at your site, and it is still the same old same old--no real relevations in snowball earth theory.

Answer 6

This is a difficult point for AGW advocates. True the Earth was different back then, but AGW holds that high levels of CO2 lead to warming. If a doubling from the present level will lead to temp over 10C higher than now, why was it only 10C warmer when CO2 was 20 times higher than it is at present? Was it the Earth that was different or was it the laws of physics? The sun was obviously putting out more energy than today so CO2 should have had even more infrared radiation to trap in the atmosphere. Yet it didn't.

The link below shows this data in clear fashion. It's based on ice core data and geologic data. Since this same data is used by the IPCC it's odd that you'd now question it.

As you can see at the same link, we're currently about 18,000 years into the present interglacial . They last 15-20,000 years on average so it's possible we'll revert to the current ice age at any time. And as we've seen from the geologic record, high CO2 levels won't be enough to stop that from occurring.

Answer 7

As far as I am aware the record of Co2, which scientists use as evidence of GW only goes back 450,000 years, there are no records that date back to the time periods you talk about.

You didn't post any supporting links for this claim.

KRW: quick science lesson on the greenhouse effect, visible light passes through the atmosphere regardless of Co2. This light reaches the surface of the Earth and is converted into infrared heat most which is radiated back into space Co2 absorbs some of this heat, more Co2 means more heat retained.

Answer 8

we were not around 450 billion years ago

and at one time this whole planret was a dessert ,another time the air was 70% carbon dioxide

we could never have lived then ,and neither did much else.except plants.

the point is we are here now and have to do with what is now

http://dsc.discovery.com/convergence/glo...