Reply #22: It sounds like a semantic misunderstanding - we seem to be on the same page [View All]

[Psephos]

(I appreciate, btw, your civil tone in this discussion.) :)


As previously noted, greenhouse gases do not directly warm the Earth, they slow the rate at which it radiates its heat into space. The effect is a rise in the thermal equilibrium point, but the gases themselves do no heating (i.e., do not introduce additional energy into the system). Instead, they prevent the leakage and loss of whatever energy the system already contains.

...but global warming is caused by increasing levels of greenhouse gasses.

Such a statement alone is too narrow to be useful. Planetary warming can be caused by a lot of things in addition to greenhouse gases, most importantly in the short run including a rise in solar output. The mild cooling trend of the past half-dozen years is now thought to be a consequence of the extraordinarily quiet sunspot cycle we've experienced, and subsequent dip in total solar output of about 0.01-0.02 percent. Best estimates are that the coming uptick in the normal cycle will be lower amplitude than normal.

Decadal and larger-timescale oscillations in thermal currents in the ocean basins are also profound influences.

Astronomic cycles also figure prominently. Precession in the axis of Earth's rotation, gravitational perturbations in Earth's orbit from other planets, position of the Solar System relative to the Galactic plane, extrasolar interferences with the Solar wind, etc.

Surface albedo, and more importantly, cloud density, have the ability to shift us to Hothouse Earth or Snowball Earth. Cloud formation depends on a variety of influences, especially including levels of aerosols that can act as nuclei around which water vapor will condense. Sulfur dioxide and micro-particulates are two prominent villains, and both can arise from natural as well as human sources.

Methane is far more potent a GG than CO2, and greenhouse effects due to rises in its concentration are more important. Human terra-forming and agriculture are changing atmospheric methane levels. (I will leave discussion of potential catastrophic releases of methane ices and hydrates from the ocean depths for another thread.)

CO2, because of its dynamic and highly complex recycling through ocean dissolution, organic carbon burial, and uptake by growing plants, cannot be treated as a static independent variable without considering feedback loops. Unfortunately, these loops remain beyond all but the crudest mathematical descriptions.

I've barely begun here. Suffice to say that global warming (or more accurately, Earth's thermal homeostasis) is a chaotic, multivariate system of dynamic, recursive feedback loops, "strange attractors," and unseen teleconnections. It can't be mathematically described using linear equations, and its equilibrium state cannot be ascertained from initial conditions.

These properties attain to any chaotic, multivariate system of dynamic, recursive feedback loops. For example, the economy. Billions of dollars were spent on ultra-highspeed computers, millions of lines of modeling code, convocations of the greatest economic scientists and quantitative modelers...and none of the models predicted the meltdown of the financial core witnessed last year.

The economy is almost infinitely less complex than the ocean/atmosphere complex, the geology and geography of Earth, the planetary motions, the moody Sun, water chemistry, the influence of the biosphere, and all the other things that factor into climate trends.

Yet no one using these models foresaw the outcome in the economy.

It's inappropriate to make the flat statement that greenhouse gases cause global warming for the same reason that linear mathematics are inappropriate to the job of describing the machinery.

---------------------

The energy would replace the energy we currently get from fossil fuels, about 1/10,000 of the energy that the earth receives directly from the sun. This isn't what causes global warming.


First, the article says nothing about space-station energy replacing fossil fuels. That's your addition. It sounds reasonable, but consider that the world's largest CO2 emitter, China, is not going to be trying to limit its CO2 emissions (except for political window dressing), and will actually be increasing them steadily for the foreseeable future. (For example, China is currently building ~50 new large coal-fired power plants per year). Any fossil fuel "saved" by the space station will simply be consumed by a China, an India, or (name any of a hundred non-signatory countries) instead. Any "saved" fossil fuel will increase supply, which means it will lower price, which means it will increase demand. Which means it's going into the air.

More importantly, the way you worded your sentence, you seem to be saying that Earth receiving energy from the Sun doesn't cause global warming (remember, btw, space station power is simply re-directed solar energy). Instead, you seem to imply that GGs cause global warming. Again, Earth's temperature depends upon an equilibrium between incoming and outgoing heat.

Think of the Earth as an oven, with the door propped open slightly by a wooden spoon. Turn the oven on. With the coil glowing (Sun shining), the oven heats up, but some of the heat escapes through the crack in the door (Earth's natural heat radiation into space). At a certain point - the equilibrium temperature - the coil is glowing continuously, but the escaping heat balances the coil heat, and the oven equilibrates at, say, 400 degrees. Now shut the door (raise the level of GGs, and prevent the heat escape). The oven temperature rises, then equilibrates at, say, 500 degrees (because heat still escapes through the oven's insulation and surfaces).

Now cut the coil power in half (lower the Sun's output). The equilibrium temperature drops.

Now restore the power, and also turn the broiler coil on at full power (Increase the Sun's output). The equilibrium temperature rises.

Your statement that the energy the Earth receives from the Sun doesn't cause global warming is not true. If solar output is constant, then it has a neutral effect on the current equilibrium. But solar physicists have already shown that the Sun is fickle and full of surprises, and its only constant is its inconstancy.


---------------------

I try to promote precision in discussions about AGW because without it, any hope we have of even the barest scientific understanding of how this ultracomplex system works will disappear.

I think we're of like mind, both on the overall global warming phenomenon, and on the need to rein in CO2 emissions. So really, what I wrote above is for the consideration of others.

Best to you.