Jake, if we go up 5 or 6 degrees we are, as far as I can make out, in territory going back about 40 million years in a world with sea level 80 metres higher and a world climate not especially suited to homo sapiens even with our clever technology.

tim, Hansen reckons with 4C plus we have an entirely different world. Of 5 or 6 degrees Mark Lynas reckons it’s like playing Russian roulette with a Luger, the point being I think that it doesn’t (can’t) have an empty chamber.

Jake, I can’t yet be as pessimistic as you are, but personally, being risk-averse, I’d like to see us going for a 350 ppm of CO2e target ASAP on the way to 300. Lynas (following Jones, C et al 2006 in Scellnhuber, H J (ed.) Avoiding Dangerous Climate Change Cambridge UP) reckons we need 350 ppm CO2 (not CO2e) to stay within 1C longer term. Since we are committed to about 1.3C if we stop now I think 350 ppm would have to happen real soon.

Lynas (following Meinshausen also in Schellnhuber and quoted also by Stern)reckons that 400 ppm of CO2 (we are 384 now) gives us a 75% chance of staying within 2C. Those are less good odds than Russian roulette, although a 2-3C world may not be terminal to civilisation as we know it. Then again the tipping points it might trigger could carry us through to a 4C plus world. This is the very essence of why 2C plus is dangerous.

It’s my ambition to do a post spelling all this out a bit more and citing the supporting documentation, partly because I’m sick of being called an alarmist but mostly I’d like people like Roger to tell me whether it’s reasonable or way off beam. Time is my enemy, though.

We can’t attribute the relative level of influence of natural variability and change on rainfall at the moment, and there is also an evaporative effect with warming that is increasing dryness.

The key issue made by putting the recent climate with climate change in the report is that we need to take a whole of climate approach. I would like my fellow climatologists to make this point more emphatically and obviously and indeed have been saying so all week at the Greenhouse 2007 conference.

What we are most likely experiencing now is a double whammy of long-term climate variability interacting with climate change. If the recent low in rainfall (downward shift from 1997 in southern Aust) is variability, then we may expect a partial recovery in the future. If it is all anthropogenic, we would expect this or worse in the long term. My priors are leaning towards the former, and it is an area of active research to determine what exactly is going on.

In other words, this 5 to 6 degrees centigrade predicted global average temperature rise is more than this planet has experienced since the last ice age, 20,000 years ago!

And it’s all caused by those *!%$$! that worship the god of the economy, with total disregard for the environment!

And if you delve deep enough into the IPCC reports from the United Nations, you’ll discover that the lag time between emissions and climate change is so great that it’s too bloody late to worry about reducing emissions – by the time reducing them (even to zero, right this very instant) has any effect upon the climate almost all life on the planet will be dead anyway!

Sleep well.

“It also has to be noted that a difference between 5 and 6C is pretty much the same as the difference between being shot in the head 5 or 6 times.”

Kind of puts it into perspective…

They’re wondering out loud whether it has something to do with the cloud of sulphur dioxide, ozone, particulates, and whatnot emanating from China.

Juz, concerning the 2 degree limit, the report is looking forward from a 1990 (actually 1980-2000 average) standpoint. Hence the 2 degree in this report is well past the 2 degrees normally given out as the threshold for dangerous climate change, which is referenced to pre-industrial levels.

I heard author Penny Whitton interviewed and she repeatedly assured us that the current drought would pass, that the rains would come, but the average precipitation would decline over time in most parts of Australia. So we are meant to believe that it will be well into the century before things get to be as bad as they are now. I’m interested to know why she believes this other than that it is in the models, but I’m not sure I’ll find it in the report.

On the ‘now’, jt author Scott Power from the BOM said that this year to September had been the hottest ever. He also said that the spring rain in the Murray Darling so far had been the lowest ever. So near term we are meant to expect things to get better.

If you go here and activate the animation at the bottom of the page you’ll find that Sydney and Canberra do quite well in the rainfall stakes and are better at the end of the century than at the beginning. This is not good for concentrating the political mind.

The report also shows the 2 degree limit is going to be hard to stay under without deep emission cuts. Sadly, I don’t trust either party to actually listen to the scientists on this one, what with people’s plasma TV needs foremost in their minds.