Thursday, June 10, 2010

Heat Death vs Cold Death

Here is a bit from a posting by Ron House on the Watts Up With That? web site. He looks at the sun's heating during the last ice age, at the height of the last warming, and today. He compares that will the "heating" we add due to our technology. These numbers are a real shock:
... at the depth of the last ice age, around 22,000 years ago, the Sun’s power (again at 65°N) was around 463Wm-2. On the other hand, at the height of our own interglacial, the Holocene, which occurred about 11,000 years ago (yes, we have been on the downward slope ever since—though you would never guess it from the hairy scary stories about warming in the media) the summer insolation at 65°N was about 527Wm-2. In other words, we have:

WhatWhenSun's Power
Previous Ice Age22,000 years ago463 W per sq m
Holocene Peak11,000 years ago527 W per sq m
The Perfect TimeNow476 W per sq m


The difference between peak warmth and deepest cold was around 55Wm-2;
The current value, being only 13Wm-2 above the value at the depth of the ice age, is almost all the way back to ‘cold conditions’; it may be that only stored ocean heat is keeping us out of an ice age (for now).
Moving on, how do these power figures compare with human energy output (mainly by burning fossil fuels)?

Human energy usage in 2006 was 491 exajoules. This translates to an average power usage of 15.56 terawatts each second (divide by the number of seconds in a year). To compare this with the Sun’s power as discussed above, we need to average this over the entire planet. The Earth’s surface area is 510 million sq. km., which gives 30,500 W per sq. km, or 0.03Wm-2. One final adjustment is needed to allow us to do the comparison: the Sun’s insolation given above was as received at noon, whereas this figure is an average over the whole planet. Since the planet’s area is four times the areas of a circle of the same radius, we must multiply by four, giving about 0.12Wm-2 as our final figure for comparison.

The human energy output of about 0.12Wm-2 is clearly overpowered by even the smallest of the numbers we have looked at so far. The 13Wm-2 difference between ice age conditions and today is at least a hundred times larger than human energy output. We might delay a killer ice age slightly, but our heating of the planet is nowhere near large enough to save us.
What the above makes clear is that we live on a knife's edge of instability. And that the power of Nature swamp our puny technology. We like to think we are powerful masters of our environment with our technology, but we are still but a pin prick on the surface of the earth.

I remember read scare stories in Junior Scholastic back in the late 1950s projecting that current energy use -- especially with nuclear reactors -- would lead within the foreseeable future to the earth's running so hot that rivers boil away. That was the fantasy of "masters of the earth" run wild. And it was the same doom-and-gloom fascination that hold people in thrall today.

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