David Randall: The Role of Clouds and Water Vapor in Climate Change

[@kjaanishji2595]

Wonderful lecture! Thanks prof. David

[@grindupBaker]

At 59:37 I think David should have addressed first unequivocally the questioner's possible misunderstanding "...evaporation rates will go up therefore there'll be more cloud...". Water vapour is not cloud so if evaporation rates go up therefore there'll definitely be more water vapour but not necessarily more cloud. I'm not sure that David's '...lots of things can happen to that water vapour..." sank in. Water vapour is an invisible gas of H2O molecules, just like N2, O2, CO2, CH4, N2O, O3. The assessed 13,000,000,000,000 tonnes of "water vapour" in Earth's atmosphere appears to include the liquid form but the actual gaseous water vapour is by far the larger portion of it (I forget the ratio now but it's several to 1) so no reason at all why a warmer surface might not increase gaseous water vapour while simultaneously decreasing its liquid form "clouds". You know that there's an invisible gas of H2O molecules water vapour everywhere in air because it's between your eye balls and the screen you're reading this on unless you got your room to 0% humidity with some special equipment, no clouds in your room though I hope.

[@grindupBaker]

I like listening to this guy because he's so drole & that's my favourite. He shows cartoon of a blazing Sun that's 50 times smaller and 14,000 times closer than reality & comments "It's actually somewhat further away than what you see in the picture". No shit Prof, really ?

[@citizenschallengeYT]

At 45:30 - Can someone explain why cloud cover seems to increase when atmospheric H2O concentration drops?

[@jottes3776]

Its explained at the end of the lecture, in the questions part.

[@nicholasveridiculity91]

Now just compare ultraviolet and cosmic ray flux with cloud data and we'll really start to see an amplifying effect. It is important to note that, over the Arctic Ocean (being higher in latitude), colder temperatures (which increase the likelihood of low clouds formation) are more present in Winter, combining with higher clouds in Summer to serve as a greenhouse for irradiance: where low clouds hold heat underneath more effectively as they thicken during Winter and solar minimums (increasing with cosmic rays during solar minimums).

[@grindupBaker]

There's been no significant trend in cosmic ray flux over the last 60 years.

[@citizenschallengeYT]

Here's an UPDATE regarding the overall impact of clouds on Earth's heat budget: *Observational constraints on mixed-phase clouds imply higher climate sensitivity* Tan, Storelvmo, Zelinka | Science 08 Apr 2016: Vol. 352, Issue 6282, pp. 224-227 science.sciencemag.org/content/352/6282/224 also see: mobile.nytimes.com/2016/04/08/science/climate-models-may-overstate-clouds-cooling-power-research-says.html

[@markyoung8613]

Cloud cover increases because less water vapour means cloud formation happens at the point of precipitation. Ie warm moist air moves into an area of dry air and therefore is attracted to other water molecules quickly (molecular structure, oxygen always has 2 free ports (electrons), if anything comes near the oxygen molecules grab it). In moist air the water vapour moves into a H2O saturated air mass, saturated air mass has less free ports. So water vapour can drift away. Cirrus clouds form in cold air, they are wispy and thin because the electrochemical activity has slowed down and the electrons vibrate less. Electrons need to vibrate so as they can engage with each other. Or put simply heat and saturation govern chemical interaction.

[@PacificCircle1]

I would like to see researchers investigate the role of evaporation due to irrigation and deforestation. Such activates must increase water vapor, the primary Greenhouse gas.

[@alanmcintire8727]

+PacificCircle1 It's been done. journals.ametsoc.org/doi/abs/10.1175/JCLI3627.1 We get slightly cooler days thanks to plant transpiration, warmer nights, and an overall slight warming.l

[@PacificCircle1]

Alan Mcintire Thanks. That study was done in my region! Cool. What I should have said was the role of human induced humidity should be given more weight in the Climate Change discussions.

[@grindupBaker]

"Such activates must increase water vapor" no because only an increase in average tropospheric temperature can increase water vapor because it doesn't have a very low boiling point like CO2, CH3, O3, N2O and some other gases.

[@grindupBaker]

Very interesting thanks. I hope your models is better than I did for elevators cause I gots bods walking thru walls like X-Men or Quatermass and The Pit. They call for 100mm rain on Burnaby Mountain tomorrow & Saturday. I think it's caused by "clouds" and "Atmospheres".

[@grindupBaker]

29:55 I can predict the weather in Vancouver 2 weeks from now with consummate skill. Rain.

[@112hidde112]

The contrails....

[@grindupBaker]

The Horror ! The Horror ! Oh The Humanity !

[@markyoung8613]

Water vapour is only .04% of our atmosphere. So the cloud formation effect will be

[@grindupBaker]

Your "Water vapour is only .04% of our atmosphere. So the cloud formation effect will be

[@markyoung8613]

Opps. looks like the 1'c has already happened, and the Ice shelves, Opps, Opps oh shite.

[@zzebowa]

"all these things have now happened" Sorry, that isn't true. Tropospheric warming has not been substantial enough, humidity has not increased (look at ALL data sets) and only one pole is warming.

[@grindupBaker]

"Tropospheric warming has not been substantial enough". How substantial do you want it ? What do you consider enough ? You accidentally didn't say.

[@diannemurray]

You claim it isn't true. But have you got any citations from peer-reviewed journals to back up your assertion? I see no reason to believe you over a professor on an accredited University's KZbin channel. You cpu;d be anyone. you could be being paid by oil companies for all the rest of us know. Pony up with the data or it's bullshit.

[@roger_is_red]

try listening because then you learn and will not come off as being so useless

[@zzebowa]

@@diannemurray NASA NVAP-M, ISCCP VW, there you go, no substantial VW increase

[@zzebowa]

@@grindupBaker Lets say half the Claussius Clapeyron relationship