The comments over at More Misc are trailing off, but I am (as ever) astonished by peoples' desire to have the last word. Let it never be said that KK is uncontroversial. Still, what more could he ask? So, time for something else.
I didn't comment on Al Gore's latest (did I?) or even watch it, but David Hone has what look like some perceptive comments.
I'm beginning to get google circle spam in unmanagable amounts: too many X's are adding me to their circles, and I can no long bother check them all out, let alone reciprocate. Still, I did find Climate Deniers Campaign Against the BBC Backfires. Yes, it is old, like me.
In other old news, the UK shale gas find made the news over here and the blogs. That links somewhat to the maybe gas is as bad as coal idea, which I find dubious (but haven't worked through yet). Various people don't want to use the gas and the Grauniad reports Chris Huhne with: The UK's "dash for gas" will be halted by the government because if unchecked it would break legally binding targets for carbon dioxide emissions, Chris Huhne, energy and climate change secretary, said on Monday evening. That seems weird to me because (pace Cornell) switching to gas is better than coal (certainly if measured in terms of CO2 emissions, which is the legally binding bit). However what he actually said was "We will not consent so much gas plant so as to endanger our carbon dioxide goals" which is ever so slightly different, and could be consistent with approving lots more gas. Apart from anything else, we could extract and sell it to johnny foreigner. Or then again, if the gas were too cheap to meter (ahem) it would make CCS economic. Curiously enough, Timmy in April had a rather different perspective. I'm very dubious that our so-called legally binding CO2 targets are meaningful, anyway.
[Update: on the gas-vs-coal: the thing I didn't look at closely was how much Wigley's numbers depend on aerosols from coal. I assume, a lot. But going forward, that is unlikely to be true: we just couldn't increase coal use that much without cleaning it up a lot.]
* Coal to gas: the influence of methane leakage CLIMATIC CHANGE Volume 108, Number 3, 601-608, DOI: 10.1007/s10584-011-0217-3, 2011.
* Press Release: CMU Researchers Find Fewer Greenhouse Gas Emissions From Controversial Drilling at Marcellus Shale Sites Statewide
* Alberta leads Canada in Fight Against Global Warming
Have you watched the documentary Gasland?
After watching that, you can count me among the "various people" who are at minimum sceptical about shale gas.
[No, though I saw a small fragment. But watching such videos is no way to make policy -W]
The problem with the "gas is as bad as coal" idea is that Wigley didn't model any 'cleaning' (reduced aerosols) of future coal production for his comparison. We take the salty stuff here.
"how much Wigley's numbers depend on aerosols from coal. I assume, a lot. "
If I recall, slightly more than half of the raw temperature increase from the coal to gas switch comes from the aerosols, and slightly less than half from methane leakage (assuming 2.5 to 5% rates).
Contrary to Roger Romney-Hughes, I believe that Wigley _does_ assume that global coal cleans up to modern US standards by 2070, but given the assumed increase in coal combustion in the reference case, that's still a lot of sulfur being emitted.
Here's the quote from the paper about sulfur assumptions: "To account for this we assume a value of 12 TgS/GtC for the present (2010) declining linearly to 2 TgS/GtC by 2,060 and remaining at this level thereafter."
We could compare this to the RCP scenarios, which have about 8 TgSO2/yr from fossil sources in 2100, which is 4 TgS/yr... which would imply only 2 GtC/yr from coal... that's pretty low, so I'm assuming most of the RCP models are cleaner than the Wigley assumption by the end of the century.
M @ 3, you're correct; from the full text of Wigley's paper (free-access html version here):
"...emissions factors for SO2 will decrease over time. To account for this we assume a value of 12 TgS/GtC for the present (2010) declining linearly to 2 TgS/GtC by 2,060 and remaining at this level thereafter."
He also accounts for changes in black carbon proportional to the changes in sulfates. The reduction in the proportion of energy generation from coal is assumed to be a linear 50% between now and 2050.
Looking at his Fig. 3, it's important to remember the numbers reflect change in methane emissions over present and to consider the combined effect of the changes in all modeled species - his 'total' curves, which show that even at an increase in methane leakage of 5% (which includes not only any increase from shale gas leakage but also the decrease from reduced coal mining), the modeled T change is negative after ~2060 - when the modeled halving of coal generation and cleanup of aerosol proportion are complete.
As Wigley says, the effect is small, and it's no substitute for keeping GHGs from all sources out of the atmosphere - but the post-2060 effect is cooling, and the projected warming over the next 50 years owes more to the reduction in aerosols than to the increase in methane (shown at larger scale on Fig. 2b). This is opposite to what's been claimed in many places.
I corresponded directly with Wigley on this, and he told me that even if coal plants were shut down and not replaced, there is the same warming trend over the next few decades. So the paper has been misrepresented as a refutation of natural gas, when it is really about the aerosol effect of coal. That should have been clear when it showed an expected rise in temperature even with zero leakage assumed.
Thus, I wrote a tongue-in-cheek essay that the Wigley paper shows that solar and wind power will increase global warming:
Apologise for ot, although it is old news ! this is apparently famous on the internet (but I'd never heard of it)
Your work was taxpayer-funded, and PNAS represents that its authors will make underlying data available. I'd like to review the data myself and ensure availability for others, including experts and my students. Others have expressed interest in access to the data in addition to myself, and your website seems well-suited for public release of these data.
[It is rather funny. Thanks for the link - I hadn't seen it before -W]