Scenes from a Hat: The Unemployening - Page 3

amplify · #21 04-24-2007, 09:59 AM

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POG fast seduction techniques

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Hi. HUWW4BJs?

amplify · #22 04-24-2007, 10:01 AM

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Sexually suggestive haiku

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your aroma was
lingering softly until
I shaved my goatee

ESKiMO-SiCKNE5S · #23 04-24-2007, 10:09 AM

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The REAL causes of global warming

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What about the sun?

irradiance.gif (21293 bytes) This Solar Irradiance Reconstruction is by Judith Lean, Naval Research Laboratory. ABSTRACT (Lean 2000): Because of the dependence of the Sun's irradiance on solar activity, reductions from contemporary levels are expected during the seventeenth century Maunder Minimum. New reconstructions of spectral irradiance are developed since 1600 with absolute scales traceable to space-based observations. The long-term variations track the envelope of group sunspot numbers and have amplitudes consistent with the range of Ca II brightness in Sun-like stars. Estimated increases since 1675 are 0.7%, 0.2% and 0.07% in broad ultraviolet, visible/near infrared and infrared spectral bands, with a total irradiance increase of 0.2%.

Back of an envelope calculation: Earth is estimated to have warmed 0.6 °C ± 0.2 °C so all we need to do is divide the estimated temperature increment by Earth's temperature (288 K) and times by 100 to get the percentage increment thus: 0.6 (K)/288 (K) x 100 = 0.2%. So, the sun is 0.2% more energetic and conveniently the planet's temperature is believed to have increased 0.2%. Solar influence explains the entire change, now everyone's content the global warming thing has been solved, right? No? Us neither, although solar variance seems a likely candidate for at least a portion of the apparent change.

IrradianceVsTemp.gif (24399 bytes) Let's look at this a little more carefully. Assuming all warming has taken place since the mid-Nineteenth Century, (an assertion with which we do not concur), solar influence could still account for the bulk of assumed change because the difference in solar irradiance from the (admittedly cherry-picked) low of 1889 to end of available record is 2.33 Wm-2 or 0.17% and Earth's temperature of 288 K + 0.17% = 288.49 K, a figure well within our warming bounds of 288.6 ± 0.2 K. Superficially attractive and certainly the fit is significantly better than that observed for atmospheric carbon dioxide increment, although it is still less than perfect.

aerosol.gif (30687 bytes) Much has been made of sulphate aerosols "masking" warming that would otherwise have occurred and so we might ponder whether the post-WWII boom of reconstruction and development added significantly to atmospheric aerosols. This could have induced the apparent lag in solar warming in the 1950s and 1960s. Additionally, this was the Cold War era of atomic weapons development and atmospheric testing which could have added to atmospheric particulate load (remember the fears of "nuclear winter"?). Unfortunately, we lack the resources to check this at present but we may revisit the hypothesis in the future. Further research is required, as they say.

So, while the solar irradiance/temperature variance fit is not entirely compelling it is a significant improvement over that of temperature/atmospheric carbon dioxide.

There are, of course, other potential anthropogenic influences on global mean temperature, although the net sign remains unknown of such changes as albedo (Earth's reflectivity) resulting from land use change, humidity and cloudiness in response to plant transpiration changes from broad scale agriculture and irrigation. Then there's changing particulate loads and aircraft exhaust affecting cloud abundance, altitude and type, etc., to name but a few. It could be that these other anthropogenic effects tend to cancel each other out, leaving a net total change of zero, we just do not yet know enough to quantify everything.

Always assuming the estimated warming of +0.6 ± 0.2 °C actually exists (and it is at least plausible that it does, even if our ability to precisely quantify it remains poor), is there room for increased solar irradiance and calculated enhanced greenhouse forcing? Actually, from the figures above, they are a pretty neat fit. Estimated increased carbon dioxide forcing ~0.17 °C + percentage increase from increased solar irradiance ~0.49 °C = ~0.66 °C, well within the error bounds of +0.6 ± 0.2 °C.