Hadley Centre - no GHG emissions reductions = 5.5 to 7 deg C warming by 2100

2.8 C with a 47% reduction is a lot, not even considering this scary nugget from the tail end of the climateprogress article Dana posted:

I would note that the Hadley Center, though more inclusive of carbon cycle feedbacks than most other models, still does not model most of the feedbacks above or any feedbacks from the melting of the tundra. 

i WOULD EXPECT

If we maintain current temperatures and cut emissions by 70% immediately, we would not maintain current temperatures and would not maintain current CO2 concentrations.

That is to say, our current temperatures are likely high enough to raise earth's greenhouse effect by increasing our CO2 and water vapor level. We probably do not need to add anything at all to GHG in order to sustain and even raise our temperatures, and raise the GHG concentration.

If we have warming now, it is far more as a result of buildup of GHG from previous years rather than new additions. But even more significantly, dropping our emissions does not imply that  GHG concentrations will decline.  Dropping our GHG emissions does ALLOW  but not cause ghg CONCENTRATIONS to decline.

What would cause a decline in concentrations, assuming we are not emitting, might be a drop in temperatures. But with current concentrations of GHG, we will not predict that drop in temperatures.  It could happen if some event like a large number of volcanoes blow.

If the arctic continues to warm up, we could have large releases of CH4, and of course we have a lot of reduction in reflectivity as arctic ice disappears.

So we have to come up with some explanation why concentrations would start to drop significantly before a couple centuries have gone by.

Right now our oceans appear to be unwilling to absorb CO2 as fast as in the past, and our soils are gassing off more. Forests are dry enough to support large wildfires, further reducing our rates of sequestration.

That bit is definitely scary...but it's pretty terrifying even without that taken into consideration.  Also from the climateprogress article...

The consequences of 5.5°C warming by 2100, which Hadley says is “likely” on our current emissions path are all but unimaginable — mass extinction, devastating ocean acidification, brutal summer-long heat waves, rapidly rising sea levels, widespread desertification.

So we must stabilize at 450 ppm or below — or risk what can only be called humanity’s self-destruction.

I hope you're right.  Not to be too pesimistic on a Monday...but I'll feel a little better when there's some real policy in place.

hmm. chancellor merkel is doing her best to scupper that......and out gov in u.k. are only paying lip service, they are very keen to get this new coal plant through, with not even a nod to carbon capture.