A report on a lecture given by a glaciologist

[Weather-history]

Here's a report on a lecture given by a leading glaciologist of the time, Hans Ahlmann, on the 3rd of May 1948

Edited July 22, 2008 by Mr_Data

[johnholmes]

tks for another interesting read Kevin

[Gray-Wolf]

I guess with the increase in global dimming over the next 40yrs public attention was shifted away from the issue. Only with the advent of our own 'clean air act' (1968?) and a similar suite of measures across western Europe and North America did the awful scale of mans inpacts on the globe begin to emerge.

Strange to think though that we did not include the emmisions that led to the acid rainfall that resulted in the strilisation of swathes of northern european lakes and the death of so many Pine trees.........not that mans emmisions can impact our globe you understand......or so some would have it

[jethro]

I guess with the increase in global dimming over the next 40yrs public attention was shifted away from the issue. Only with the advent of our own 'clean air act' (1968?) and a similar suite of measures across western Europe and North America did the awful scale of mans inpacts on the globe begin to emerge.

Strange to think though that we did not include the emmisions that led to the acid rainfall that resulted in the strilisation of swathes of northern european lakes and the death of so many Pine trees.........not that mans emmisions can impact our globe you understand......or so some would have it

I had a look at the whole dimming scenario a while ago (one of the few subjects Stratos and I were in agreement about!) - the whole situation raises more questions than answers.

Sooty emissions were very high prior to the warming of the early 20th century, so if particulates are responsible for cooling in the 60's/70's, why did they not act in the same way then? We'd had "dirty air" for a long time, and yet temperatures managed to increase, Arctic ice melted and glaciers retreated.

The clean air act did correspond with a cooling period, between 1958 (when measurements reliably began) and 1992 when the effect levelled off, we received, on average 10% less Solar radiation. Since the early 90's the effects of global dimming have lessened considerably with a resurgence in Solar radiation hitting the Earth - this corresponds with the rapid increase in temperatures in the mid-late '90's.

This again raises more questions than answers; if dirty air made the world cooler, and the now cleaner air has made it warmer, then it surely follows that given temperatures have been on a par with the '30's in recent years, Arctic melt and glacier retreat also is on a par with the 30's, then the dramatic warming due to CO2 is actually far less dramatic than believed? What we have actually achieved is a "manmade" cooler period which now rectified, has revealed we are as warm now as we were 80 years ago - despite large increases of emissions of CO2. This actually fits far, far better with the known properties of CO2, in that the first increases have the largest, most dramatic effect upon climate - the more you add, the less effect it has upon temperatures.

[Optimus Prime]

Surely the ammount of burnt coal in the atmosphere wouldn't be enough to cause a large scale cool down, we know locally, places like Mexico City that lies in a plateau, burning of fuels can create smog over time which in turn limits sunlight, but on a global scale I can't see how that can work.

[jethro]

Surely the ammount of burnt coal in the atmosphere wouldn't be enough to cause a large scale cool down, we know locally, places like Mexico City that lies in a plateau, burning of fuels can create smog over time which in turn limits sunlight, but on a global scale I can't see how that can work.

Like many things in this field of research, there are contradictory findings.

Here's a link from Wiki - sometimes not the best source of info but this gives a good, general over-view.

http://en.wikipedia.org/wiki/Global_dimming