GeologyRocks

Don't know about the climate change debate but I know for a fact that this is considered in the normal, daily weather forecasts already. Any big city or even small town has it's own mirco-climate largely influenced by its ability change the temperature.

I would suspect that the heat we (humans) create is relatively insignificant in the context of the earth.

I would suspect that the body heat emitted by all other warm-blooded creatures was far greater than that emitted by humans and their activities. And, that being the case the Earth would have undergone a runaway greenhouse effect shortly after warm-blooded creatures evolved. That has not occured therefore I would not have thought it was an issue.

I remember being taught that the reason CO2 in the atmosphere keeps heat in (a scientific fact, not for dispute and separate from the man-made vs natural vs no warming argument) is due to the dominant wavelength of radiation emitted by the sun (visible-light) being different to that emitted by the surface of the earth (infra-red). It just so happens that the wavelength of infra-red radiation emitted by the earth is of the length that excites CO2 molecules (and other greenhouse gases eg CH4)  which is why the heat from the sun can pass through the atmosphere but the heat from the earth can't all get back out.

It is estimated that the 'greenhouse effect' in total (i.e. the heat kept in the Earth's atmosphere by greenhouse gases) is on the order of 30C (or 30K if you prefer!). Therefore without some greenhouse effect life, as we known it (Jim), would not exist on Earth. And the snow in the UK would be even worse than it is at the moment!

Hmmm, I seem to have gone slightly of topic here but I'll return to the main theme for a closign remark. I'm not sure what base data goes into climate models but once the basic model is built I presume the modelling is along the lines of 'if we change x what happens to y'. In this situation I would expect body heat (and heat from industrial processes etc) to be set to a constant. Which raises the interesting point that this is obviously wrong, increasing industrialisation in China, India, Brazil etc. demonstrates this, but at what point does it have a measurable effect on climate, and how far away are we from that point?

Again I seem to have ended by just asking the original question again. To prevent myself going further back in time I propose to stop typing........now!

I do not have the link to hand, but I have read something that works it out. With the figures they gave, we have created a negligable amount of heat. Absoluely tiny compared with crustal heatflow.

Just to adress a couple of points here...

1. al8301 is indeed justified in what they say about the wavelengths that the earth gives off being sufficient to excite CO₂. Whilst I'm willing to admit that I gone into the specific wavelenghts my Physicist hat tells me this is logical.

2. I can't comment on the details in climate change modelling (that's an entirely different rant for me!) but the heat given off by buildings etc does cause a significant difference in the temperatures between the CBD and rural fringes of cities. This is called the urban heat island affect and temps can vary by as much as 7C from memory due to the way concrete etc will store heat for longer. It seems reasonable to assume that this would then make some difference to global temps but a very small one indeed!

A bit of money for old rope I'm sure but it seemed relevant at the time

TJM