I have been making my way through the series of lectures by David Archer based on his book Global Warming: Understanding the Forecast.

http://geoflop.uchicago.edu/forecast/docs/lectures.html

I'm not sure who on OLO originally recommended it but thank you. Certainly giving my bandwidth a hiding.

For someone who did year 12 physics over 2 decades ago I have had to blow a few cobwebs off certain parts of the brain to start to digest them properly but thoroughly recommend them to anyone wishing to take their understanding to the next level.

For me personally I thought the issue is too important to let only my ideology dictate my stance so if I could make the time to extend my knowledge then I needed to make the effort.

I am about half way through the series and was wondering if a discussion or q&a might be had on some of the ideas?

One of those early concepts was the fact that David Archer seemed to be saying the earth only loses heat to the universe via light because space is a vacuum. I understand much of the light out is in the IR frequency but is there any other way of heat loss occurring? It is a little hard to get ones head around the notion this is the only path.

The other concept I'm struggling a little with is the need for a difference in temperature to be present for there to be a greenhouse effect.

I'm pretty keen to stick with the science, or in this case the basic physics, rather than the politics if that's okay. If anyone has seen them all, or who is making their way through them and wants to kick a few of the concepts around, or know the answers to the above regardless, then any input would be welcome.

Hi, I'd love to be in a discussion that was purely about science. He's right about heat loss only occurring into space via radiation. Three ways heat is lost is conductance, convection and radiation. For the first two you need reasonably dense particles, and the first works best with compounds in a crystalline lattice structure, like metals. The second works with liquids and gases, and the third with anything that doesn't block radiation.

I think it was in Grade 10 when we went into the physics of the vaccuum flask. Do you remember it had a glass inside vessel surrounded by a vaccum, which took care of conductance and convection, and then a silver lining on the inside of the outer-skin to reflect the radiation back into the liquid.

Similar principle to the greenhouse effect really, with the greenhouse gases as the outer-skin, except the greenhouse gases absorb and re-rediate rather than reflecting. You don't have much, if any conductance happening, but lots of convection as well.

Not sure what your second issue is. Can you explain it a little more?

Csteele

This link (GrahamY knows about it) will help explain a few things better than 350 words can do.

http://eesc.columbia.edu/courses/ees/climate/syllabus.html

Work your way through the syllabus, or go straight to the topic that interests you.

Although somewhat dated, it is still relevant and is still being taught.

A few wannabe 'climate scientists' are going to lob in here, why not get back after a bit of home grown research - be glad to continue the discussion then.

I like real science discussions. It would save a lot of time and bandwidth time though, if we are going to discuss particular concepts mentioned in the series, if you (we) could in future reference the specific lecture the concept first appears and the approximate time it is mentioned, this helps to give some context for the question.

In the meantime I myself shall start from the beginning (when I find the time).

Dear Graham and others,

I am up to lecture 15 and although I get most of what I have viewed there is some of it I have only just got a slim grasp of. I realise he has had to cram a hell of a lot into a course and it is a little frustrating not being there to ask questions so thanks for the input.

Probably showing my scientific shallowness but I had the sense that the Earth was bathed to varying degrees with solar wind, i.e. steams of different sized particles that rushed past us, and I thought a warm body might have contributed to their energies thus removing heat. Not correct it would seem.

My second query came from Lecture 9. I think he is possibly just stating the obvious but in a way that makes it complicated. From the 3:00 minute mark to the 4:45 he talks about the layer having to be colder than the ground to have a green house effect but I thought the difference came about because of the green house effect. Seemed to be putting the cart before the horse, or am I missing something critical?

One impression from David's lectures was that all the light we received from the sun was then turned into lower frequencies after striking the ground and it was these that were interacting with the various GHGs in the form of IR. I didn't realise until I looked further that 49% of the Sun's heating of the Earth is due to direct IR from it.

I am also struggling a little with the notion that it gets warmer after the troposphere leaving it the coldest layer of the atmosphere. Perhaps the mechanics might be explained a little later.

I'm not sure why the troposphere is cooler than the layers either side. Someone else will have to fill that gap.

As most of the sun's energy passes through the air then it can't heat it more than it heats the earth. There is also a question of thermal mass. There is not a lot of mass in the air to hold much heat. And if the atmosphere was hotter than the earth the heat wouldn't escape from the earth. The fact that the earth cools means that the atmosphere has to be cooler than the earth because energy moves from high to low states, i.e. hotter to colder in this context. If the atmosphere were warmer then the earth is going to keep heating until it reaches a temperature which is higher and then the heat loss will start again.

I would have thought that the solar wind would have some small effect on temperature, but my understanding is that most of it is deflected. There is the Svensmark theory about solar wind and cosmic rays modulating cloud formation, but I know you're not asking about that.