birder
Level 3 Rank
Posts: 223
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Post by birder on Feb 28, 2010 11:31:51 GMT
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Post by socold on Feb 28, 2010 13:40:25 GMT
Human activity accounts for just 2 percent of global carbon dioxide emissions - the remainder is generated by natural processes like plant decay.A far more relevant scientific fact about carbon dioxide is that as a result of human activity co2 concentration in the atmosphere has risen 35% over the past 200 years to levels not seen for at least 1 million years (probably 15 million):  CO2 is not the major greenhouse gas - its water vapour instead. Current climate models don't know how to model this and various types of cloud.The same reason we know water vapor is the strongest greenhouse gas, we know that co2 is the second strongest. In fact the reason we know water vapor is the strongest is from climate models! A doubling of CO2 in the atmosphere (of which remember humans only account for 2% of) traps less than 2% of outgoing heat from the planet.And a 5 degreeC (9 degreeF) warming of Earth's average temperature would be a less than 2% change in Earth's temperature. Small numbers don't always mean a small deal.
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Post by scpg02 on Feb 28, 2010 17:44:10 GMT
A far more relevant scientific fact about carbon dioxide is that as a result of human activity co2 concentration in the atmosphere has risen 35% over the past 200 years to levels not seen for at least 1 million years (probably 15 million): Not true. Direct measurements showed CO2 was higher than today in the late 1800s. |
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jtom
Level 3 Rank
Posts: 248
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Post by jtom on Feb 28, 2010 17:49:06 GMT
Looking at that graph, I am far more concerned about those long periods of time where CO2 levels were too low to support plant growth. Not a good situation for the animal kingdom, including Man.
By the way, there are other reconstructions of CO2 that indicate it's been bouncing between 200+ and 500- ppb just within the last few hundred years. Dependes on if you trust direct measurements of CO2 using equipment with a large range of error (compensated by a large number of measurements) versus ice core proxies, which has its own detractors. Lately, I've been getting more and more skeptical of proxies.
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Post by socold on Feb 28, 2010 20:38:53 GMT
A far more relevant scientific fact about carbon dioxide is that as a result of human activity co2 concentration in the atmosphere has risen 35% over the past 200 years to levels not seen for at least 1 million years (probably 15 million): Not true. Direct measurements showed CO2 was higher than today in the late 1800s. They weren't measuring the atmospheric co2 level. |
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Post by scpg02 on Feb 28, 2010 20:45:44 GMT
Not true. Direct measurements showed CO2 was higher than today in the late 1800s. They weren't measuring the atmospheric co2 level. And your proxies are? |
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Post by glc on Feb 28, 2010 21:25:23 GMT
They weren't measuring the atmospheric co2 level. And your proxies are? CO2 measurements are direct measurements taken at specially selected locations. The measurements you referred to in the 1800s were also direct measurements but they were taken at locations where the gas was not "well-mixed". If you look at these measurements it's clear that many of the measurements were taken in city locations. There are cases in the Beck 'study' where CO2 levels have jumped (or fallen) ~100 ppm in just one or two years. |
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Post by sigurdur on Feb 28, 2010 21:30:05 GMT
CO2 measurements are direct measurements taken at specially selected locations. The measurements you referred to in the 1800s were also direct measurements but they were taken at locations where the gas was not "well-mixed". If you look at these measurements it's clear that many of the measurements were taken in city locations. There are cases in the Beck 'study' where CO2 levels have jumped (or fallen) ~100 ppm in just one or two years. You are correct GLC. Taking the mean of the samples during that period, co2 was similiar to what it is today. |
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Post by scpg02 on Feb 28, 2010 21:35:15 GMT
CO2 measurements are direct measurements taken at specially selected locations. The measurements you referred to in the 1800s were also direct measurements but they were taken at locations where the gas was not "well-mixed". If you look at these measurements it's clear that many of the measurements were taken in city locations. There are cases in the Beck 'study' where CO2 levels have jumped (or fallen) ~100 ppm in just one or two years. You are correct GLC. Taking the mean of the samples during that period, co2 was similiar to what it is today. Doesn't that preclude the notion that they are dramatically higher today? |
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Post by sigurdur on Feb 28, 2010 21:39:08 GMT
No, they are not dramatically higher today that during the 1800's.
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Post by nautonnier on Mar 1, 2010 12:07:37 GMT
Not true. Direct measurements showed CO2 was higher than today in the late 1800s. They weren't measuring the atmospheric co2 level. SoCold they WERE measuring the atmospheric CO 2 level in many cases these direct measurements of atmospheric CO 2 continued for more than a century. It is the Vostok and other ice cores that are using the proxy of bubbles in ice that are assumed ( incorrectly) to be the same gas composition as when the air was initially trapped by falling snow. |
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Post by sentient on Mar 1, 2010 13:36:21 GMT
naut, I am aware of many studies which tackle the problem of firn. Co-deposition of carbonate laden dusts is one of the problems, fractionation due to gravitation and thermal diffusion are two others. A seminal paper by Huber et al (2006) (attached) may shed some light on how these problems are dealt with in the proxy ice records: Attachments:
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Post by sentient on Mar 1, 2010 13:38:01 GMT
The oxygen isotope problem is further addressed by Mani et al (2008) (attached): Attachments:
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Post by hunter on Mar 1, 2010 13:47:38 GMT
Human activity accounts for just 2 percent of global carbon dioxide emissions - the remainder is generated by natural processes like plant decay.A far more relevant scientific fact about carbon dioxide is that as a result of human activity co2 concentration in the atmosphere has risen 35% over the past 200 years to levels not seen for at least 1 million years (probably 15 million): CO2 is not the major greenhouse gas - its water vapour instead. Current climate models don't know how to model this and various types of cloud.The same reason we know water vapor is the strongest greenhouse gas, we know that co2 is the second strongest. In fact the reason we know water vapor is the strongest is from climate models! A doubling of CO2 in the atmosphere (of which remember humans only account for 2% of) traps less than 2% of outgoing heat from the planet.And a 5 degreeC (9 degreeF) warming of Earth's average temperature would be a less than 2% change in Earth's temperature. Small numbers don't always mean a small deal. socold,, There is no evidence at all that temperatures are going to raise, on average 5oC due to CO2 introduced by man. |
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Post by nautonnier on Mar 1, 2010 14:25:10 GMT
naut, I am aware of many studies which tackle the problem of firn. Co-deposition of carbonate laden dusts is one of the problems, fractionation due to gravitation and thermal diffusion are two others. A seminal paper by Huber et al (2006) (attached) may shed some light on how these problems are dealt with in the proxy ice records: You may be interested in this: "CO2 diffusion in polar ice: observations from naturally formed
CO2 spikes in the Siple Dome (Antarctica) ice core"Journal of Glaciology, Vol. 54, No. 187, 2008 "ABSTRACT. One common assumption in interpreting ice-core CO2 records is that diffusion in the ice
does not affect the concentration profile. However, this assumption remains untested because the
extremely small CO2 diffusion coefficient in ice has not been accurately determined in the laboratory. In
this study we take advantage of high levels of CO2 associated with refrozen layers in an ice core from
Siple Dome, Antarctica, to study CO2 diffusion rates. We use noble gases (Xe/Ar and Kr/Ar), electrical
conductivity and Ca2+ ion concentrations to show that substantial CO2 diffusion may occur in ice on
timescales of thousands of years. We estimate the permeation coefficient for CO2 in ice is 4
10–21 molm–1 s–1 Pa–1 at –238C in the top 287m (corresponding to 2.74 kyr). Smoothing of the CO2
record by diffusion at this depth/age is one or two orders of magnitude smaller than the smoothing in the
firn. However, simulations for depths of 930–950m (60–70 kyr) indicate that smoothing of the CO2
record by diffusion in deep ice is comparable to smoothing in the firn. Other types of diffusion (e.g. via
liquid in ice grain boundaries or veins) may also be important but their influence has not been quantified." |
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