Friday, February 26, 2010

Emissions Compared to IPCC Scenarios

I found this here, and it saved me the trouble of making my own version.  The "Marker" scenarios in the darker blue zone (or a subset of them actually) are what the IPCC studied as possible emission scenarios that were used to drive model-based estimates of what would happen to the climate over the 21st century.  As you can see, the burst up due to the rapid growth of Chinese emissions in the 'oughts' has started to drive the actuals higher than any scenario that was studied.

You can get more details of the scenarios here.

In the short term it probably doesn't make much, if any, difference because there's so much lag in the climate system anyway because of the huge heat capacity of the oceans.  In the longer term, it's likely to make for a heck of a lot more climate change.


Just to back up that last point a little bit, here's the left hand half of Fig 10.4 of the IPCC Fourth Assessment Report, showing the rise in global average temperature over the twenty-first century.  The heavy lines are the average of a number of models (the numbers 17, 21, etc are how many models were used), and the light shading represents one standard deviation in the annual means of the various model runs.  The colors represent various emissions scenarios.

So this is humanity's best guess about the impacts of climate change, and you can see that what we do now doesn't have a huge important impact on the temperature mid-century (which is going up quite a bit regardless in any reasonably likely scenario).  But by 2100, the fact that we appear, at least for the moment, to be under a "worse than any of them" emissions scenario, will probably have a big impact if it continues.
and here's figure 10.8, which shows the regional distribution of temperature change.

Again in the 2046-2065 panel, the result is not terribly dependent on the emissions scenario, but by 2080-2099 it is.  So, at least to the extent the climatologists have really understood all the relevant dynamics of the system, it appears that our children's world is already largely set, and we are deciding our grandchildren's climate.

Or to put it another way, the fact that our children will face an unstable climate is largely the fault of those of us in the developed world, but the fact that our grandchildren will face an even more unstable climate will be mainly due to the fact that China, etc, have decided to copy us.


KLR said...

A puzzling aspect of this is that a sustained period of reduction in carbon emissions in the early 80s didn't show as a commensurate decrease in observed CO2. The stock explanation is that natural sinks weren't operating strongly enough to scrub all the CO2 out, but if the system is that non-linear it doesn't seem likely that another (voluntary) period of reduced emissions will necessarily have much to show for it after 5 years.

1980-84 global CO2 emissions as documented at


The fit for the 80s looks very close to R2 1.0. Where you did see a temporary decrease in observed CO2 was the early 90s - this brought about, apparently, by 1992's -1.86% in emitted GHGs, and some extra vigorous sinks.

The interplay between the two is covered at this site: CO2 measurements Start at the graph at 5.1. Presumably the impact of further observed emission cuts will be amplified by wearing down of natural sinks from human impact; this all has been modeled and I'm out of my element big time here.

What do you think of the assertions by Aleklett etc that we simply lack the carbon to go A1? I found Hanson's thesis that peak oil will simply be a bump on the road to exploiting shale/XTL rather wanting, too. His primary ref was Hirsch, whose work left a bit to be desired in specifics. I wish he'd document some of those in detail - would be good to see more opinions on CTL's prospects, for instance.

KLR said...

Emissions data at Global Fossil Fuel Carbon Emissions - Graphics. I meant a linear trend for the 80s in observed CO2.

Stuart Staniford said...

KLR - I haven't updated these stats in a few years, but the environmental carbon sink is generally quite noisy year-to-year - eg see this graph:

porsena said...

KLR - There's a large inertia in the climate system and its feedbacks. Easing off the accelerator for three or four years won't much affect our speed.

Like Aleklett, I have also said that the IPCC's scenarios unrealistically didn't take account of peak oil. Today I'm thinking there's probably more than enough left to fuel a future that's well over the magic two degrees warmer than the pre-industrial temperature.

Stuart- Your top graph is certainly disturbing. I have the same understanding (from the same sources) about the relative insensitivity of temperature change to emission rates over the next couple of decades. However, the emissions path we take now will affect the magnitude of changes experienced by anyone born in the last thirty years.

Those using this year's hard winter in the Eastern US to argue that global warming is a hoax forget that one of the predictions of the IPCC model ensemble is increased variability. Just a bit further north, ice between Newfoundland and Quebec and off Labrador is the thinnest it's been since 1968. The red colour in this sea ice anomaly chart indicates how abnormally weak these ice conditions are.

Here in BC, location of the spring Olympics, we're on track to have our warmest February on record. An often overlooked feature of global climate is that, absent something like a major volcanic eruption, when it's unusually cold in one place it's normally unusually warm somewhere else.

KLR said...

It's the cost of going XTL that interests me, which seems much more daunting than most believe. Mingo CTGasoline plant in WV will be $3 billion and two years (not counting lengthy review etc process) for 18 kb/d. Wow, that's a lot of trouble to make up for, oh, one typical year of declines in Louisiana. This is to say nothing of the costs in infrastructure, water, environmental damage, and the increased depletion of coal itself.

Yet over at RC I've seen Gavin Schmidt ref Hansen's paper for his handwaving away of any potential limit on carbon. He has a few dismissive mentions of peak oil in his Dire Warnings book, too. Perhaps I'm wrong; yet again, it's a bit unnerving that we bloggers seem to be the only ones interested in these basic numbers.

Econdemocracy said...

It's not your fault Stuart but the y axis is a bit misleading on the temperature chart for those trying to look for that oft-cited 2 degrees C mark - warming of 2C or more above pre-industrial level as a danger point. The 0 mark is not the pre-industrial level but, it's hard to eyeball, something like 1990 maybe? Which means the danger level is not found by letting a horizontal line at "2C" from the y-axis his the graphs, but rather letting a horizontal line at a much lower level (1.4C? graph is a bit small to read).

I also have a problem with thet 2C mark namely if it was your baby daughter (or baby son) and there was a danger level at 2, would you let the toxin be injected into her/his body until it was exacdtly 2? Chances are you'd prudently not "Try to limit it to 2" but "Try to limit it to x" where x is a much smaller number. Consequently "2C" should be thought of as not "safe it below that level" but "a level to aim BELOW" and not a level to "aim for".

"Like Aleklett, I have also said that the IPCC's scenarios unrealistically..Today I'm thinking there's probably more than enough left to fuel a future that's well over the magic two degrees warmer than the pre-industrial temperature."

That's right. The "unrealistic" cuts two opposite ways: less crude might be burned up, but possibly much more tar sands, plus shale, plus coal (some without cabon capture, some with cabon capture which we might discover 20 or 50 years later, isn't a perfect 'capture'), methane clathrates, etc, where more might be burned. .Thus while "unrealistic" it is the right kind of "unrealistic" to project from current trends, to be honest about it and say that, and to state in a side note that due to peak oil, emissions might be lower (because...easy to explain) or might be higher (above factors) or might be roughly the same.

"but the fact that our grandchildren will face an even more unstable climate will be mainly due to the fact that China, etc, have decided to copy us. "

Or "due to the fact that China, in response to current foreign policies of the US and EU, which have so far refused a massive technology transfer, seems to have decided to copy us" It is not a perfect "Copy" either, they have some environmental programs in motion, and plans, but qualitatively I don't strongly dispute their "copying" us as a description. But we must not forget any Chinese decision is made in context, and our policies have a big role in determining that context. If we change policies, the context changes, and different decisions by China and others are possible then. But profits might suffer or advantage might suffer, if we give "too much" away in technology transfer, so possibly screwing the planet over seems to be a price elite decisionmakers are willing to (have others) pay in the future.