Re: Is it getting hot in here or is it just me?

Posted by Dale on Mar 07, 2002 at 10:32

(204.212.222.29)

Re: Nope, we must act NOW (Mike Kremer)Lets assume EVERY family and every shop in your wonderful future world, uses the equivalent of a 2Kw bar fire thats switched on for 10 hours(thats conservative?)out of the 24.

Thats going to warm up the world somewhat, right?Am I the only one who loves to grab a calculator and see what numbers turn into when properly crunched? You want to assume every family and shop. That number is a little nebulous. How about every individual. Families combine individuals at home but we have the other part for the shops. Let’s just take today’s number of 6 billion. You can double the number if it turns out to make any difference. So, 6e9 * 2KW * 10 * 365.25 = 4.4e13 kwh/year. I’m sure you would object if I used that energy to raise the temperature of all the earth (distribute the energy through the entire mass of the earth ) so I’ll just use the upper 10 centimeters of the land mass and the oceans (surely it’s ok to assume ocean currents to distribute the heat there?). I won’t bother with the air or the loss of heat into space because I think the temperature rise will be so small it won’t matter. (My basis for this assumption before calculating anything is the earth would already be real hot if anything other than solar energy were causing a significant temperature rise.)

So here we go: the mass of the top 10 centimeters of the land mass Me = 1 / 7 * 3.14*D^2 * 10 * m where D is the diameter of the earth in centimeters and m is the mass of a cubic centimeter of earth. Me = 0.45 * (1.63e18) * 10 * 1.6 = 1.17e19 grams. The mass of the oceans Mw = 6 / 7 * 3.14 * D^2 * 3.66e5 * 1 = 1.6e24 grams. The specific heat of earth is 0.22 g-c/g and the specific heat of water is 1 g-c/g. Therefore the temperature change can be calculated from 4.4e13 * 860e3 = (Me * 0.22 + Mw * 1) * 1.16e-3 * Td where Td is the change in temperature in degrees C per year. Td = 3.26e22 / (1.17e19 *.22 + 1.6e24 * 1) = 0.02 degrees C per year if every man woman and child on earth used about $75 of electricity per month.

You know what? That doesn’t sound like very much but we better not take a chance. Better that a few million people die every year by freezing to death than that we raise the temperature of the earth by 0.02 degrees by being selfish. ;)

BTW, I did these calculations rather fast. They look about right but I would appreciate it if someone would check them. Confirmation is always apprciated. :) Anyone who does will probably be as surprised as I was that the earth term disappears in the ocean term. I always knew the oceans were what kept life on earth possible but this calculation makes it obvious why life on any planet not covered by oceans will be much more difficult.