CO2 did not Lag temperature by 800 years - new Science Study

[JackTaylor]

New York Times
http://www.nytimes.com/2013/03/01/science/earth/at-ice-age-end-a-smaller-gap-in-warming-and-carbon-dioxide.html?_r=1&

has an article about CO2 levels during ice age recovery being in lock-step or leading temperature rising - warming, NOT an 800 year lag as many others claims.

[Dromicosuchus]

...I'm a tad bewildered.  There should be a delay, yes?  Shifts in NH insolation, and the resulting reduction in ice cover, were what drove the rise and fall out of the ice ages, so there ought to be some time lag between the initial pulse of (slight) warming and the CO2 increase that magnified the effect.  Am I understanding things incorrectly?

Mind, I wouldn't necessarily be surprised if I was; the transition in and out of ice ages, I know, is a devilishly complex process, and the northern and southern hemispheres interact in complex ways during that transition.  I wonder, too, why the researchers looked at N2 to determine the transition, rather than examining O18 ratios in the CO2 itself.  With the usual caveats regarding my ignorance, that would seem to me to be a better strategy, since with your temperature proxy locked into the CO2 molecules themselves you'd guarantee that the temperature data and CO2 concentration data hadn't drifted relative to one another.

[crandles]

There should be a delay, yes? 

AIUI,

If something other than CO2 starts the warming and only later does the CO2 start getting released to act as feedback loop then there should be a delay depending on how long it takes to start the feedback loop.

If CO2 starts the temperature rise then you expect the CO2 rise to start at a pretty similar time to the temperature rise. Whether and how much before or after depends on what strength effects non CO2 causes of temperature change are having.

[gfwellman]

If the natural  Milankovitch mechanism is
Insolation->direct heating->ocean releases CO2->main warming
there should be a lag with a timescale appropriate to heating the top layer of the ocean enough to get things going.

But if the mechanism is more like
Insolation->permafrost and vegetative changes *and* direct heating->CO2 released from permafrost and CO2 released by ocean->main warming
then the timescales are mixed and one is possibly short enough to obscure any lag within the resolution and sensitivity of our paleo measurements.

[JackTaylor]

Regardless of the exact mechanism, IMHO the significance is that Dr. Parrenin may have information which hopefully becomes evidence.

With all the information - skepticism - speculation ( favorable - unfavorable about GHS ) causing a warming climate beyond Milankovitch Cycles, the supposed 800 year lag has been a large if not the most significant obstacle for proponents of AGW.
   

[ggelsrinc]

This involves the old lagging indicator argument which totally ignores science, because a lagging indicator is an oxymoron to science. Now, don't take what I say as preaching to the choir, but this is how my argument has developed with Denialistas.

Anything that changes radiative forcing always has it's affect, regardless of amounts. All greenhouse gases were warming the Earth during the coldest part of the ice ages when they were at their lowest. Methane and water vapor would also be reduced during cold periods. If it can be proven that a change in the amount of a greenhouse gas has an insignificant affect on temperature, then challenge the Denialista to support that conclusion with calculations. I usually point out how a humid area will retain it's temperature throughout the night while a dry desert area won't. Obviously water vapor is a greenhouse gas that will retain heat without sunlight.

After years of having this argument with Denialistas, I've adopted the style of picturing our Earth in it's present form. I show the changes that caused the Earth to be sensitive to Milankovitch Cycles and glaciation. I show how the modern thermohaline circulation was born when North and South America connected and interrupted the remnant of a circum-equatorial current. This isolated the Atlantic Ocean and allowed it to cool.

The amount of radiative forcing caused by Milankovitch Cycles seems large, because it causes such major changes in glaciation, but it's actually a very small force in a short period of time. The same feedbacks can cause cooling or warming and all that is needed to counter the cooling effect of Milanovitch Cycles is to cause enough warming in a short period of time.

[Bruce Steele]

Since this study only looks at the end of the last ice age maybe it was human influences that helped things along even 20,000 years ago. Humans have had a love affair with fire for a very long time, way before the start or end to the last ice age. Even as hunter gatherers we utilized fire to modify our habitat. Locally fire was utilized to burn chaparral scrub hills each spring so as to encourage grasslands. Grassland habitat is much more productive for deer, rabbits, and game production than thick chaparral. Maybe signs of soot should be considered in the ice record analysis. It would also be interesting to see if the CO2 / heat record in the ice is the same in ice ages before human population had expanded out of Africa(or earlier).I have always found it ironic that we elevate our importance ( in the image of god )while at the same time denying our influences on nature. This probably isn't universally the case for all human cultures but it plays a huge role in the denialist mantra. 

[Bob Wallace]

Obviously water vapor is a greenhouse gas that will retain heat without sunlight.

This could explain the relative lack of warming in the US Southeast states?

Since their air was already quite humid they would not have been experiencing the nighttime cooling of dryer parts of the country.  (And I well remember those hot, muggy nights.  Tossing a CO2 blanket on top wouldn't make much difference in nighttime heat retention, water vapor was already taking care of that.