2018-06-04

On Microsoft acquiring GitHub

In the news today is that Microsoft is acquiring GitHub (Pocket Link to Verge). That's a big deal for a lot of big (and small) open source projects. It's definitely going to rub a lot of open-source developers the wrong way, as many are motivated to contribute to open source projects as a direct response to decades of difficulties with Microsoft.

I am not a Microsoft user, nor a fan. But I do acknowledge that there's been some apparent improvements over the past few years under CEO Satya Nadella. They have some open projects that are notable, especial VS Code, which is becoming very popular. From what I hear, Windows is still a monstrosity that should not be used, but it is clear that Windows 10 is improved over the last few versions; note, last time I really used windows was still Windows 98, I think.

My suspicion is that Microsoft wants GitHub because they want to use it internally for very large projects. Recently Microsoft has been working to make git more useful for humungous projects, specifically with the virtual file system (techcrunch). By controlling GitHub, Microsoft becomes the biggest player in git as well, which I'm sure won't please some.

It's also worth noting that GitHub developed the text editor Atom, which is pretty similar to their aforementioned VS Code. Atom is an open source project, but it will be interesting to see what happens to Atom development going forward.

Finally, I'll also mention that GitHub has adopted Markdown as it's documentation markup language of choice. There's already a GitHub flavor of Markdown, which I think is probably the dominant version. Now that Microsoft owns GitHub, I wonder if it will impact the use of Markdown, and especially if GitHub-flavored Markdown will further evolve away from the original?

2018-05-28

What is aerosol radiative forcing?

There is a lot of research about the climate impact of aerosols. One of the fundamental measures of the climate impact is the "radiative forcing" associated with aerosols. It's not obvious what exactly aerosol radiative forcing is, however, so here we begin our examination of this question.

The IPCC AR4 provides a nearly useless description: [LINK]

We can discern two important facets of aerosol radiative forcing from that description:
  1. It is measured based on top-of-atmosphere (TOA) radiative fluxes. 
  2. It includes the impact of aerosol on clouds. 
It is also useful to look at other parts of AR4, where better text describes aerosol effects. I started at the link above because when I search for "aerosol radiative forcing" that is one of the top hits I get. That's an unfortunate hit because the text surrounding that small section is much more informative.  

The first thing that can be clarified is that #1 above is part of the definition of radiative forcing. As far as IPCC reports go, radiative forcing is the impact that a forcing agent has on the net TOA fluxes. The concept is useful because it is derived from the basic physics of conservation of energy and thermodynamics. In equilibrium the net TOA flux is zero (averaged over a year, or many years). When a forcing agent is applied to they system, such as anthropogenic aerosol, the energetic consequence may be a change in that TOA balance (i.e., a radiative forcing), and having a TOA imbalance causes the system to respond. We deduce that if the forcing is negative the system will cool to achieve a new balance, but if the forcing is positive (i.e., more energy is entering the system than leaving) the system will warm to achieve a new balance. Aerosols typically fall into the negative forcing category, and so cause a cooling, but the story is not really so simple.

In particular, it is helpful to split aerosol effects into two pieces:
  1. direct effects of aerosol particles on radiative transfer through the atmosphere (scattering and absorption) (aka, aerosol-radiation interaction, ari)
  2. indirect effects of aerosol that change the radiative properties of clouds, or change the lifetime of clouds (aka, aerosol-cloud interaction, aci)
The IPCC AR5 [LINK] includes a lot of treatment of aerosol radiative forcing. Since it's newer, perhaps we should focus there for some clarity on this issue. An important distinction is drawn in AR5 between radiative forcing (RF) and effective radiative forcing (ERF). While RF is just what we were describing, namely the change in the TOA net flux (allowing adjustment of the stratosphere), but ERF allows the troposphere to also adjust to the forcing agent. To establish ERF is tricky because it does not allow the global average surface temperature to adjust; the idea is that ERF includes tropospheric "rapid adjustments" to occur, while RF only allows for the rapid stratospheric adjustment to occur. Confused yet? 

We will return to this distinction in another post. For now, we need to consider that both direct and indirect effects have a RF but also an ERF. This complicates the picture because it further muddies the water with respect to how we describe how aerosols effect the climate system. Mostly AR5 seems to deal with RF associated direct aerosol effects and ERF for indirect effects.  For now, though, let's return to our basic question of what is aerosol radiative forcing.

Based on IPCC AR4 and AR5, along with a lot of literature reviewed therein, and also my own literature review that spans from the 1980s to today, the easiest way to express the meaning of aerosol radiative forcing is:
Aerosol radiative forcing is the change in TOA radiative fluxes between the preindustrial period and the present day. The aerosol radiative forcing can be divided into direct effects in which aerosol effects radiative transfer and indirect effects in which aerosol interacts with clouds. 
Estimates of the total direct aerosol radiative forcing is around -0.35 (-0.85 to +0.15) W m-2. Including indirect effects switches to using the ERF concept, which we will examine in another post, but the AR5 bottom line is that the total aerosol effect is a negative forcing of about -1 W m-2, but that is basically plus or minus 1 W m-2

What I want to point out before closing is that I described RF in the beginning as fundamental, but the definition that I've just provided seems far from fundamental. When we use this definition of aerosol radiative forcing, we need to define what pre-industrial means and what present day means. We know intuitively what both are supposed to mean, but quantitatively this is ambiguous. Particularly troublesome is that we do not have adequate observations from pre-industrial times to really know what the aerosol concentrations or emissions were. This provides an irreducible uncertainty for aerosol radiative forcing using this definition.  We will revisit some of these concepts in future posts, and we will return to the difficulties associated with this definition of aerosol radiative forcing.

2012-12-29

Joseph Romm raves about Reagan, balks at Barrack: Figures of speech make and break communication


I have recently read Joseph Romm's new book, Language Intelligence,
which is really a brief review of rhetoric. It introduces modern readers to
the age-old topic of eloquent language intended to persuade
audiences. Romm uses just a few prime examples for each of the several
topics covered, from the ancient Greek greats to medieval masters who
wrote the King James Bible to modern practitioners such as Lady
Gaga. The point is to expose the principles of rhetorical discourse,
such as the various forms of repetition, irony, metaphor, and
seduction, and provide readers with some of the tools necessary to
build an effective argument as well as to erect a wall to defend
against the constant bombardment by advertisers, politicians, and
other persuaders.

The lessons are clear and well illustrated by examples. Especially
useful are the examples from recent political figures such as both
George Bushes, Bill Clinton, Barrack Obama, and Mitt Romney. Several
Republican strategists are pointed out for their cunning use of
rhetorical devices (Luntz and Rove, especially). Scientists (climate
scientists, especially) are singled out for their clumsy attempts to
communicate, usually avoiding rhetorical figures of speech. The
use of the figures being discussed occasionally becomes too blatant,
often in the final paragraphs of sections, but it is pleasing as a
reader to see such employment as sections close because it reinforces the
lesson. I am convinced that this brief introduction should be standard
reading for college students across disciplines, and those in the
sciences should pay careful attention to the lessons and employ more
intelligent language when describing their own work. Older readers
might pick up some new tricks, too, if they choose to read the book.

2012-08-28

American Meteorological Society Statement on Climate Chnage

Posting two days in a row!?!?

I just wanted to draw attention to the updated statement on climate change from the American Meteorological Society. Here's the link: [LINK]. It is just a 7 page statement that goes through the following sections:

  • Background 
  •  How is climate changing? 
  •  Why is climate changing? 
  •  How can climate change be projected into the future? 
  •  How is the climate expected to change in the future? 
  •  Final remarks
There is nothing surprising in the statement. The AMS supports the scientific consensus that the Earth's surface and lower atmosphere are warming due to the accumulation of greenhouse gases in the atmosphere from combustion of fossil fuels and deforestation. Overall, it is well-written and straight-forward, and I recommend taking a look at it no matter what your background is. My guess is that everyone will get the gist, and if you've got any background in climate science then you'll pick up on some of the details. I'd quibble over some of the word choices here and there, but the substance is fine. Maybe they over emphasize climate models in the future section, because many of the points they make there are not based solely on model projections, but also observations and basic theory. Anyway, go take a look.

2012-08-27

Smart meters and dumb people

As a regular listener of Coast to Coast AM, I have been aware of a conspiracy theory involving the transition from old-timey analog utility meters to internet-connected smart meters. Smart meters allow 2-way communication between a house's utility meter and the utility company. The idea is to monitor electricity use in real time (or near real time), which can allow more nimble management of the electric grid. The idea is to get electricity where it is needed when it is needed and allow better management of electricity generation. Both proponents and opponents cite the potential for tiered pricing, such as raising prices during peak energy use times. While some say this will help incentivize energy conservation, others say the tiered pricing could hurt lower income households disproportionately.

The consipracists, however, are not worried about low-income households or energy conservation.  There are really two flavors of the smart meter conspiracy. First is an irrational fear of technology that manifests as a concern about the radiation from smart meters being a health hazard. Yes, really [example]. This is not a legitimate concern, as the radiation levels are even below those of cell phones, and it is unlikely that many residents will spend significant time with their heads agains their electricity meter. The second version of the conspiracy is rooted in a deep distrust of government and an overly aggressive view of privacy. These are the people, like the ones cited in this Grist post [LINK] and the accompanying AP news article [LINK] about the smart meter opposition in Texas, who believe that the smart meters are ... well, let's just boil it down, they think that the smart meters allow the government to spy on them at home [great example, go ahead a browse this crazy site, I'll wait.]. There might be some actual privacy issues with smart meters (which that example kind of hits, but then goes to crazy), such as the potential for utilities to synthesize usage and sell the information to interested parties (who want to target their marketing efforts). This probably isn't much of a concern at this point, as it is unclear that utilities are savvy enough to profitably undertake such an analysis. Really, this comes down to some far-right-wing ideas that get mixed up by fear mongers into ridiculous conspiracy theories, encapsulated by this quote from the above cited blog, "This is all part of the radical green agenda that is being forced down the throats of people all over the world."

Maybe I should just list a couple of points that I think are relevant (in no particular order):

  1. Energy conservation is a good idea, and represents one of the "stabilization wedges" that we talk about as currently available solutions to global warming. [LINK]
  2. The radiation associated with electronics is not harmful.  [LINK]
  3. One of the criticisms that the opponents of smart meters seem to bring up often is that the FCC does not have strong enough restrictions on radiation [example]. Yet, as pointed out in Grist and the AP story above, these people tend to be on the far-right/libertarian/tea-party fringe of the political spectrum, meaning that philosophically they are opposed to government regulation (in favor of letting the "market" work out the appropriate solutions). This is completely inconsistent. I don't think this is an argument against the smart meter opposition, just a point that I wish would be discussed.
  4. The possibility of utilities selling the information aside, there seems to be a general fear of a degradation of privacy with smart meters, but I don't think there is any evidence that any personal information could be or is being collected by these meters.
  5. The transition to smart meters is being driven by the "market" as utilities try to reduce costs and maximize efficiency. This is a direct descendant of the deregulation of utilities in the USA, which right-leaning folks should be applauding (if they were being consistent with their purported economic philosophy).
  6. Because the utilities are deregulated, this information would be flowing to the utilities, and not the government. That means that there must be an extra layer of conspiracy in order to bring the government into the picture. Each additional layer of conspiracy makes the theory less and less plausible.
I think I can leave it there.

Note that in the links above that are cited as examples, I have used the "rel=nofollow" attribute which prevents search engines from following the links and improving those cites' search rankings. I decided to do that because those cites, while entertaining, do not present a useful view of the issue. The other links are normal, and represent appropriate source material. 

2012-07-20

Making mds and mdworker processes stop sucking CPU

I usually don't post computing tips, but I just learned how to get rid of a problem that has been bothering me off and on for over a year.

The problem: On multiple Macs running OSX 10.6 and/or 10.7, sometimes a large amount of CPU power (and also system memory) is being used by a process called mds. The problem persists over many hours, and on laptops causes the fans to spin and battery to drain.

Some relevant information: MDS and its friend mdworker are part of Apple's Spotlight software. Basically they troll your system looking for changes and recording them in an index. That index is used by Spotlight to help you find things like that email from four years ago describing how do some arcane thing that you couldn't possibly remember, except that it has the phrase "don't cry at this point". Anyway...

The fix: I've tried a number of things over the many months of having this problem. At home, I removed external drives from the Spotlight index and that fixed the problem. To do that, open System Preferences, go to Spotlight, click on the Privacy tab, and add the external drives to the list.

On my work computers I've done the same thing, but still have the problem sometimes. It has been especially bad on my new MacBook Air with no external drives connected.

Doing some searching, I found this very useful bit: LINK.

The crucial thing that post points out is that backup software that works in the background can cause files to be constantly changing. Constantly changing files need to be re-indexed in the view of Spotlight/mds.

For some reason, I'm not allowed to backup however I want at work (e.g, to a Time Machine drive that could be sitting right here in my office). Instead, my IT department installs some software that supposedly backs up my system. Going to /System/Library/Application\ Support and finding the name of that backup software (in this case it is Symantec) and adding that directory to the list of non-indexed places solves the problem. This is equivalent to the case in that link that uses some other backup software, and I bet that other backup systems also trigger the same behavior.

REPEAT: Exclude your backup software's /System/Library/Application\ Support directory from Spotlight indexing in System Preferences -> Spotlight -> Privacy and mds CPU usage should drop to 1% or less.

Sigh of relief.

2012-05-01

Wind turbines and warming

The Christian Science Monitor [LINK] does a decent job in smacking the media coverage of a new Nature Climate Change paper by Zhou et al. [LINK]. It is no surprise to see another example of the media making hay of a superficially surprising study. Most of the articles apparently get the story mostly right, but the headline writers once again have their heads up their asses... but actually not, as their job is to get people to read the headline and then click to get to the article in order for the ads on that page to load. One particularly horrible story comes from, wait for it, FoxNews.com; the story is titled "Wind farms are warming the earth, researchers say" and it is written poorly by Eric Niiler (of Discovery News?). I'm clearly not going to post a link to that story, but just say that it does not present a very fair assessment of the paper (which I did link to above and which I did actually read).

The science of the study is nothing terribly exciting, but could provide observational evidence for the scale and magnitude of a simple mixing effect. The idea is that big wind turbines in Texas are mixing air in their vicinity, and at nighttime that means mixing air in two distinct layers. On clear nights, as the ground cools, cool air settles in contact with the ground. Cool air is more dense than warm air, so this situation creates a stable vertical structure of colder, denser air below warmer, lighter air. Usually temperature decreases as you go up, so we call this stable configuration an inversion. Just to throw some more jargon at you, this very common situation is a nocturnal stable boundary layer. The study finds trends during 2003-2011 in both daytime and nighttime surface temperature, but the larger and convincing trend is the nighttime trend, especially during summer. 

These stable layers are usually quite thin, maybe 100 meters deep. Just above the inversion, the air retains the heat from the daytime (sometimes called the residual layer). There is also a slightly less common meteorological phenomenon called a nocturnal low-level jet that is a layer of relatively fast wind that can form in or above this residual layer. (see my skillfully drawn cartoon)

If you want to put wind turbines up, one attractive feature would be thin nighttime inversions and frequent low level jets. As it happens, Texas has a lot of places like that. Note, however, that you would not want very strong winds on the top of the turbine compared to the bottom because strong torque is structurally undesirable. 

Let's imagine a turbine spinning in a low level jet above a stable layer (as in my awesome cartoon). The motion of the blades creates a turbulent wake just downstream, which mixes approximately isotropically. Let's say this means that the air is mixed up from the surface to a little above the turbine height. The result of this mixing is the same as if you stir a cup that has some warm liquid on top and cold liquid on bottom: the temperature is mixed and the resulting temperature is the mass-weighted average of the warm fluid and the cool fluid. This is exactly what the paper finds in western Texas, though they don't include a calculation of the efficiency of the mixing because their satellite data does not include profiles of temperature with height. The authors take the data in close proximity to the turbines, average it, and subtract the average from the data that is farther away from turbines. In the residual, they find this warming trend. This means that very close to the turbines, there is a nighttime warming trend, which the authors attribute to the mixing by the turbines. 

The consequences of this finding are not some kind of cautionary tale about trying to use renewable energy sources. In terms of climate change, this means almost nothing. First, as is pointed out in even that FoxNews.com article, these turbines produce 10,000 megawatts of electricity (that's enough for about three million American homes); that is a substantial amount of CO2 not being emitted to the atmosphere. Second, the effects being reported are small. Third, but most important, the warming effects of the turbines are confined to the immediate vicinity of the turbines themselves. The entire study area in western Texas is about 100km across, and the warming from the turbines is warming that is enhanced in a fraction of this small area. Related to this, the effects are not additive. Once a region has enough turbines to create this effect, that's it, the "trend" can not continue into the future because there won't be more turbines added to the area. (In fact, as turbine design gets more efficient, you'd expect to see the trend reversed eventually because there would be less downstream turbulence.)

Finally, some of the blow-hards (ha ha, get it?) are saying that this warming could be bad for crops. It is plausible that crops are being grown within the small regions that could be affected by this nighttime mixing. If these people were so worried about warming affecting crops, I think they'd note that the local impact in western Texas is about the same amount of warming as the ENTIRE GLOBE has seen from greenhouse gases. A nearby weather station [LINK] shows a pretty clear warming trend (note there must be a site change or instrument change around 1959) and I'd guess that the overall 20th Century warming for western Texas is greater than the wind farm effect. The 1979-2005 trend looks like it is about the same size in summer [LINK], and note that is average temperature, not nighttime temperature which is the notable value for these wind farms. I'm not sure what 0.5C warming at nighttime does to crops, but I'm guessing that the greenhouse warming is more important (even within this study area) than the wind farm "warming." 


LINKS:

http://www.csmonitor.com/Science/2012/0430/Don-t-believe-the-headlines.-Wind-farms-do-not-cause-global-warming


http://www.wunderground.com/climate/local.html?id=42572266000&var=TAVG