Realclimate.org has posted links to YouTube videos of the best lectures on climate from the recently concluded AGU (American Geophysical Union) annual meeting.http://www.realclimate.org/index.php/archives/2012/12/some-agu-highlights/#more-13674
I have watched and recommend these, in this order:
Sagan Lecture: Piers Sellers “The Race to Understand a Changing Planet”
Charney Lecture: Drew Shindell “Mitigating Near-Term Climate Change While Advancing Human Development”
Tyndall Lecture: Ray Pierrehumbert: “Successful Predictions”
The Pierrehumbert lecture is quite technical (and sobering), but he is one of the very foremost experts on atmospheric physics.
Summary of some of the main points from these lectures:
The climate is changing faster than predicted.
The extent of summer Arctic sea ice is shrinking faster than predicted.
The anthropogenic emission rate has increased rather than slowed as hoped.
The models have been substantially improved with:
Added biological and biochemical feedback effects
Improved physics in the atmosphere, ocean, and cryosphere
Improved sensor data
The result has been a steady improvement in prediction quality.
Several of the prediction failures of the last few decades have been resolved, with sensor data now matching the models.
Improved resolution shows that the warming at temperate latitudes is mostly concentrated on the land, which means the human impact is intensified.
On the current BAU (Business as Usual) trajectory, the climate will be quite nasty by mid-century, not 2100.
Besides the retreat of glaciers, much of the snow pack at temperate latitudes will be gone by mid-century, putting stress on food production
Control of methane emissions and Carbon black should be politically sellable because these measures will generate substantial local near-term improvements in health. Both methane control and CO2 control are necessary to achieve a leveling-off of global temperature rise at 2 C.