Recent content by Graeme M

Thank you everyone for your comments. I hadn't realised this would be such a tricky question, but perhaps the problem is I am asking about an entirely unphysical situation. I will leave it there, though happy to respond to any more comments.

OK. Drakkith clearly said this:

Pretty much, yes. If the atmosphere were at +15C and all the GHGs removed (leaving about 99% of the total mass), I'd assume it could not lose that heat to space because the GHGs are the mechanism by which the atmosphere radiates heat to space. So unless there is some other mechanism (like...

Just to be clear, I'm not trying to "disprove" the greenhouse effect of how GHGs affect the atmosphere. I am reasonably comfortable with how it all works at a relatively basic level. What I am struggling with is the suggestion that without GHGs, the atmosphere will be at equilibrium at -18C. As...

Yes, which is what is frustrating. In that post, I was more trying to get to a simple explanation of how the real atmosphere is affected by growing concentrations of CO2/CH4 etc. It got complicated real fast, but that's OK. I don't really need a rehash of that. What I am asking with this post...

No, because that's what I understand to be the case. However, at this point we have an atmosphere being warmed that has no means to radiate that heat away to space. As Drakkith said above, O2 and N2 cannot radiate heat via thermal radiation, all they can do is transfer heat to other O2 and N2...

I really worry that continuing to ask this question is going to make me seem sillier than I fear I am. Maybe if I try to be clear about the bit I want to understand - the rest I more or less grasp. Respondents appear to be missing what I am asking and focussing on the way that IR to space is how...

"Substantially more" isn't changing the fact that IR from the surface right now radiates to space in the end. What's relevant to my question is whether or not with an O2/N2 only atmosphere, the warmed surface of the planet will warm the atmosphere via conduction and convection, and how that...

Sure, just as it does now. But the ground also warms the atmosphere from conduction and convection which dominate at lower near-surface levels. Why would that no longer happen in an atmosphere without GHGs?

Now we are getting closer to what I'm really after. As is pointed out, symmetric molecules like O2 and N2 transfer heat from molecular collisions. I get that. But actual thermal radiation happens with asymmetric molecules such as GHGs like CO2 and CH4. In the real atmosphere, non-radiating...

That's what I'm struggling with. I thought the point of the GHGs is that they can emit IR, so non-GHG gasses transfer heat via conduction (molecular collisions) and the GHGs then radiate that out to space. But if non-GHGs cannot radiate IR AND there are no GHGs, how does the atmosphere lose its...

Quick question that I haven't been able to find the answer to. Greenhouse gasses both warm and cool the atmosphere by slowing heat loss to space. But what would happen without GHGs? I read that the earth would be colder (though still relatively warm), but why? Without GHGs the atmosphere would...

Thanks BillTre. That seems more what I am wondering about. What tells us that Melanesian folk, for example, are modern humans with Denisovan ancestry rather than Denisovans with modern human ancestry? Perhaps russ_watters is explaining that: I think this is where I am being confused. What does...

The book is "The World Before Us: How Science is Revealing a New Story of Our Human Origins" by Tom Higham, an English archaeological scientist. I found it very informative. Just to clarify, I'm not suggesting anything about humans and Denisovans being the same "species". Denisovans branched...

That isn't really addressing what I asked. What I am getting at is that modern humans and Denisovans must have very similar DNA. I read that in most African and European populations there is next to zero Denisovan DNA, but it is much higher (4-6%) in Melanesians which presumably is a result of...