Kevin Drum approvingly posted this chart from Muller:

I applaud the effort to match theory to actual, you know, observations rather than model results.  I don’t have a ton of time to write currently, but gave some quick comments:

1.  This may seem an odd critique, but the fit is too good.  There is no way that in a complex, chaotic system only two variables explain so much of a key output.    You don’t have to doubt the catastrophic anthropogenic global warming theory to know that there are key variables that have important, measurable effects on world temperatures at these kind of timescales — ocean cycles come to mind immediately — which he has left out.   Industrial-produced cooling aerosols, without which most climate models can’t be made to fit history, are another example.  Muller’s analysis is like claiming that stock prices are driven by just two variables without having considered interest rates or earning in the analysis.

2.  Just to give one example critique of the quality of “science” being held up as an example, any real scientist should laugh at the error ranges in this chart.   The chart shows zero error for modern surface temperature readings.  Zero.  Not even 0.1F.    This is hilariously flawed.  Anyone who went through a good freshman physics or chemistry lab (ie many non-journalists) will have had basic concepts of errors drilled into them.  An individual temperature instrument probably has an error when perfectly calibrated of say 0.2F at best.  In the field, with indifferent maintenance and calibration, that probably raises to 0.5F.  Given bad instrument sitings, that might raise over 1F.  Now, add all those up, with all the uncertainties involved in trying to get a geographic average when, for example, large swaths of the earth are not covered by an official thermometer, and what is the error on the total?  Not zero, I can guarantee you.  Recognize that this press blitz comes because he can’t get this mess through peer review so he is going direct with it.

3. CO2 certainly has an effect on temperatures, but so do a lot of other things. The science that CO2 warms the Earth is solid. The science that CO2 catastrophically warms the Earth, with a high positive feedback climate system driven to climate sensitivities to CO2 of 3C per doubling or higher is not solid. Assuming half of past warming is due to man’s CO2 is not enough to support catastrophic forecasts. If half of past warming, or about .4C is due to man, that means climate sensitivity is around 1C, exactly the no-feedback number that climate skeptics have thought it was near for years. So additional past man-made warming has to be manufactured somehow to support the higher sensitivity, positive feedback cases.

Judith Curry has a number of comments, including links to what she considers best in class for this sort of historic reconstruction.

Update: Several folks have argued that the individual instrument error bars are irrelevant, I suppose because their errors will average. I am not convinced they average down to zero, as this chart seems to imply. But many of the errors are going to be systematic. For example, every single instrument in the surface average have manual adjustments made in multiple steps, from TOBS to corrections for UHI to statistical homogenization. In some cases these can be calculated with fair precision (e.g. TOBS) but in others they are basically a guess. And no one really knows if statistical homogenization approaches even make sense. In many cases, these adjustments can be up to several times larger in magnitude than the basic signal one is trying to measure (ie temperature anomaly and changes to it over time). Errors in these adjustments can be large and could well be systematic, meaning they don’t average out with multiple samples. And even errors in the raw measurements might have a systematic bias (if, for example, drift from calibration over time tended to be in one direction). Anthony Watt recently released a draft of a study I have not read yet, but seems to imply that the very sign of the non-TOBS adjustments is consistently wrong. As a professor of mine once said, if you are unsure of the sign, you don’t really know anything.

Today in Forbes, I have an article bringing the layman up to speed on Henrik Svensmark and this theory of cosmic ray cloud seeding.  Since his theory helped explain some 20th century warming via natural effects rather than anthropogenic ones, he and fellow researchers have face an uphill climb even getting funding to test his hypothesis.  But today, CERN in Geneva has released study results confirming most of Svensmark’s hypothesis, though crucially, it is impossible to infer from this work how much of 20th century temperature changes can be traced to the effect (this is the same problem global warming alarmists face — CO2 greenhouse warming can be demonstrated in a lab, but its hard to figure out its actual effect in a complex climate system).

From the article:

Much of the debate revolves around the  role of the sun, and though holding opposing positions, both skeptics and alarmists have had good points in the debate.  Skeptics have argued that it is absurd to downplay the role of the sun, as it is the energy source driving the entire climate system.  Michael Mann notwithstanding, there is good evidence that unusually cold periods have been recorded in times of reduced solar activity, and that the warming of the second half of the 20th century has coincided with a series of unusually strong solar cycles.

Global warming advocates have responded, in turn, that while the sun has indeed been more active in the last half of the century, the actual percentage change in solar irradiance is tiny, and hardly seems large enough to explain measured increases in temperatures and ocean heat content.

And thus the debate stood, until a Danish scientist named Henrik Svensmark suggested something outrageous — that cosmic rays might seed cloud formation.  The implications, if true, had potentially enormous implications for the debate about natural causes of warming.

When the sun is very active, it can be thought of as pushing away cosmic rays from the Earth, reducing their incidence.  When the sun is less active, we see more cosmic rays.  This is fairly well understood.  But if Svensmark was correct, it would mean that periods of high solar output should coincide with reduced cloud formation (due to reduced cosmic race incidence), which in turn would have a warming effect on the Earth, since less sunlight would be reflected back into space before hitting the Earth.

Here was a theory, then, that would increase the theoretical impact on climate of an active sun, and better explain why solar irradiance changes might be underestimating the effect of solar output changes on climate and temperatures.

I go on to discuss the recent CERN CLOUD study and what it has apparently found.

From an interview with Judith Curry

They don’t disprove anthropogenic global warming, but we can’t airbrush them away. We need to incorporate them into the overall story. We had two bumps—in the ’90s and also in the ’30s and ’40s—that may have had the same cause. So we may have exaggerated the trend in the later half of the 20th century by not adequately interpreting these bumps from the ocean oscillations. I don’t have all the answers. I’m just saying that’s what it looks like.

The bump in the 90’s is important because its slope is considered exhibit A in the evidence for strong anthropogenic global warming by alarmist scientists.  Climate scientists have argued that the “bump” is so steep that it could not be natural and has to be man made.

I am not going to diss on Ms. Curry, as she is in the minority of climate scientists who don’t treat scientific disagreements as proof of evil conspiracies.  I often say that reasonable people can disagree, and she seems to approach scientific debate in this manner, rather than as a quest for religious conformity.

However, how much of a pass do we really give climate scientists for missing something so obvious as ocean cycles, particularly since even untrained amateurs like myself have been pointing out this omission for years.   For example:

Hmm, the 90’s seem suddenly less unprecedented.  In fact, from here, there seem to be a lot of bumps:

Period	Length	Trend (Degrees C per decade)	Significance
1860-1880	21	0.163	Yes
1910-1940	31	0.15	Yes
1975-1998	24	0.166	Yes
1975-2009	35	0.161	Yes

In fact, one can model past temperatures as a linear trend  (that started well before CO2 was added in any substantial quantity) and periodic bumps

I wonder what periodic effect could be causing the bumps?

Even leaving out the AMO and other cycles and just simplifying to the PDO, it sees that ocean cycles might be important.  Again, temperatures over the last 100+ years look a lot like a linear trend plus ocean  cycle-driven bumps

A while back I advanced the hypothesis that soot was a major driver of sea ice melting in the Arctic.  Black carbon deposits on ice and snow tend to force them to melt much faster by reducing their albedo.  I hypothesized that this might explain why there were record low summer sea ice coverages of late in Arctic sea ice but relatively average winter sea ice extents — black carbon can’t build up in the fall and winter because they are constantly covered with new snow and ice while soot that falls in the summer stays on the surface.

By the way, this would be good news – an anthropogenic effect due to soot is MUCH easier to correct than one due to CO2, as we know how to have a prosperous fossil fuel powered economy without soot but we don’t know how to have one without CO2.

Kevin Lawton has a post correlating past warming with areas that are susceptible to thaws, concluding that black carbon may have a role in past warming.  I have to think about his argument more, but he has some good links to recent work on black carbon and warming.

The good news:  The AZ Republic actually published a front page story (link now fixed) on the urban heat island effect in Phoenix, and has a discussion of how changes in ground cover, vegetation, and landscaping can have substantial effects on temperatures, even over short distances.  Roger Pielke would be thrilled, as he has trouble getting even the UN IPCC to acknowledge this fact.

The bad news:  The bad news comes in three parts

1. The whole focus of the story is staged in the context of rich-poor class warfare, as if the urban heat island effect is something the rich impose on the poor.  It is clear that without this class warfare angle, it probably would never have made the editorial cut for the paper.
2. In putting all the blame on “the rich,” they miss the true culprit, which are leftish urban planners whose entire life goal is to increase urban densities and eliminate suburban “sprawl” and 2-acre lots.  But it is the very densities that cause the poor to live in the hottest temperatures, and it is the 2-acre lots that shelter “the rich” from the heat island effects.
3. Not once do the authors take the opportunity to point out that such urban heat island effects are likely exaggerating our perceptions of Co2-based warming — that in fact some or much of the warming we ascribe to Co2 is actually due to this heat island effect in areas where we have measurement stations.

My son and I quantified the Phoenix urban heat island years ago in this project.

I am still wondering why Phoenix doesn’t investigate lighter street paving options.  They use all black asphalt, and just changing this approach (can you have lighter asphalt?) would be a big help.  By the way, our house is all white with a white foam roof, so we are doing our part to fight the heat island!

My company runs a snow play area north of Flagstaff, Arizona.  One of the problems with this location is that the main sledding runs are on a black cinder hill.  Covered in snow, this is irrelevant.  But once the smallest hole opens up to reveal the black cinders underneath, the hole opens and spreads like crazy.  The low albedo cinders absorb heat much faster than reflective white snow, and then spread that heat into the snow and melts it.

Anthony Watt does an experiment with ash and snow in his backyard, and the effects are dramatic.

Even tiny amounts of soot pollution can induce high amounts of melting. There is little or no ash at upper right.. Small amounts of ash in the lower and left areas of the photo cause significant melting at the two-hour mark in the demonstration.

I won’t steal his thunder by taking his pictures, but you should look at them — as the saying goes, they are worth a thousand words.

We know that Chinese coal plants pump out a lot of black carbon soot that travels around the world and deposits itself over much of the norther hemisphere.  We can be pretty sure a lot of this carbon ends up on the Arctic ice cap, and as such contributes to an acceleration of melting.

I’v tried to do a thought experiment to think about what we would expect to see if this soot was driving a measurable percentage of Arctic ice melt.  It seems fairly certain that the soot would have limited effects during the season when new snow is falling.  Even a thin layer of new snow on top of deposited carbon would help mitigate its albedo-reducing effect.  So we would expect winter ice to look about like it has in the past, but summer ice, after the last snowfalls, to melt more rapidly in the past.  Once the seasons cool off again, when new ice is forming fresh without carbon deposits and snow again begins to fall, we would expect a catch-up effect where sea ice might increase very rapidly to return to winter norms.

Here is the Arctic ice chart from the last several years:

Certainly consistent with our though experiment, but not proof by any means.  The last 2 years have shown very low summer ice conditions, but mostly normal/average winter extent.  One way we might get some insights into cause and effect is to look at temperatures.  If the last 2 years have had the lowest summer sea ice extents in 30 years, did they have the highest temperatures?

Not really, but it may have been past warming has had a lag effect via ocean temperatures.

The point is that I am not opposed the idea that there can be anthropogenic effects on the climate, and it looks like black carbon deposits might have a real negative impact on sea ice.  If that were the case, this is really good news.  It is a LOT easier and cheaper to mitigate black carbon from combustion (something we have mostly but not completely done in the US) than it is to mitigate CO2  (which is a fundamental combustion product).