Greenhouse-gas levels highest for 650,000 years

news@nature.com ^ | 24 November 2005 | Michael Hopkin

[UnbelievingScumOnTheOtherSide]

Current levels of greenhouse gases in the atmosphere are higher than at any time in the past 650,000 years... today's concentrations of carbon dioxide and methane far outstrip those in the past.

Faulty analysis since CO2 and Methane are not the largest component of greenhouse gases and are in fact only a tiny fraction. The main greenhouse gas cannot be measured in ice cores where its concentration will vary with the temperature of the ice and it is perfectly natural:

"Water Vapor is the most abundant greenhouse gas in the atmosphere, which is why it is addressed here first. However, changes in its conentration is also considered to be a result of climate feedbacks related to the warming of the atmosphere rather than a direct result of industrialization. The feedback loop in which water is involved is critically important to projecting future climate change, but as yet is still fairly poorly measured and understood.

As the temperature of the atmosphere rises, more water is evaporated from ground storage (rivers, oceans, reservoirs, soil). Because the air is warmer, the relative humidity can be higher (in essence, the air is able to 'hold' more water when its warmer), leading to more water vapor in the atmosphere. As a greenhouse gas, the higher concentration of water vapor is then able to absorb more thermal IR energy radiated from the Earth, thus further warming the atmosphere. The warmer atmosphere can then hold more water vapor and so on and so on. This is referred to as a 'positive feedback loop'. However, huge scientific uncertainty exists in defining the extent and importance of this feedback loop. As water vapor increases in the atmosphere, more of it will eventually also condense into clouds, which are more able to reflect incoming solar radiation (thus allowing less energy to reach the Earth's surface and heat it up). The future monitoring of atmospheric processes involving water vapor will be critical to fully understand the feedbacks in the climate system leading to global climate change. As yet, though the basics of the hydrological cycle are fairly well understood, we have very little comprehension of the complexity of the feedback loops. Also, while we have good atmospheric measurements of other key greenhouse gases such as carbon dioxide and methane, we have poor measurements of global water vapor, so it is not certain by how much atmospheric concentrations have risen in recent decades or centuries, though satellite measurements, combined with balloon data and some in-situ ground measurements indicate generally positive trends in global water vapor." National Oceanic and Atmospheric Administration - Greenhouse Gases

methane: during this period, levels hovered around 600 parts per billion. Today's atmospheric methane concentration is well over 1,700.

This is only a half-truth that lets one infer that methane is rising. In fact it appears to have reached a new equilibrium:

"Methane is an extrememly effective absorber of radiation, though its atmospheric concentration is less than CO2 and its lifetime in the atmosphere is brief (10-12 years)... Direct atmospheric measurement of atmospheric methane has been possible since the late 1970s and its conentration rose from 1.52 ppmv in 1978 by around 1%/year to 1990, since when there has been little sustained increase. The current atmospheric concentration is ~1.77 ppmv, and there is no scientific consensus on why methane has not risen much since around 1990." Ibid.

the initial phase of the Kyoto Protocol, which ends in 2012.

The end of the Mayan calendar! Coincidence?! ;-)

[UnbelievingScumOnTheOtherSide]

"A few good volcanoes can make our input look minuscule."

don't you mean OUTPUT? That orrifice was not made for input.

Input and output are strictly a point of view. From the atmosphere's POV both are inputs.

[aliquando]

No, I was referring to what we contribute to the atm. Therefore, input was grammatically correct.

[UncleJeff]

Only that agriculture is the weakest link in the chain of civilization, and it wouldn't take changes large enough to flood NYC to cause fairly drastic shifts in growing seasons.

Agriculture made civilization possible. It's failure would make civilization impossible.

[amigatec]

You embarrass yourself.

You have your beliefs and I have mine. Yes I am a young-Earth creationist.

[phantomworker]

Thanks!

[GreenFreeper]

What's your take? Just curious.

Doesn't seem like anything all that new though its interesting that they note previous warming periods were not the result of increased C02 levels. I happen to think reflective particulate matter contributes more than carbon dioxide and that CO2 is a fairly good indicator of that. I don't necessarily think we are the only culprit of global warming but I do think we should be mindful of the potential impacts of our actions (precautionary principal).

The real thing that bothers me regarding global warming are the extremes- the people in complete denial and the alarmists. The truth probably lies somewhere in the middle and it is in our best interest to curb these trends. The problem is that air quality is a true tradgedy of the commons- those that do the damage are not the only people who will be affected. That leaves plenty of room for exploitation. IMO