By Sherry Listgarten
E-mail Sherry Listgarten
About this blog: Climate change, despite its outsized impact on the planet, is still an abstract concept to many of us. That needs to change. My hope is that readers of this blog will develop a better understanding of how our climate is evolving a... (More)
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Uploaded: Aug 4, 2019
I love the great comments and questions you contribute each week, so I thought for a change I’d answer a few of your questions in a blog post proper instead of in the comments...
"If you could write a little more about the difference between emissions that lead to warming, and pollution that leads to cooling, I'd appreciate the clarity. I believe it has to do with the size of the aerosol -- the smaller size atmospheric particles let sunlight through (which warms the planet surface), and the bigger ones block sunlight at a certain altitude (so that sunlight "bounces" back into space before heating the surface)."
I really like this question. It is
confusing how some things in the atmosphere warm the planet and some things cool the planet. And I like your guess that maybe the sun bypasses the small stuff but reflects off the big stuff. That is some good intuition! Here is a bit more information, though you can read lots more here
and in other places. There are many questions that remain unanswered or uncertain -- the impact of pollutants on climate is a very active area of research.
When incoming light from the sun encounters particles in our atmosphere, it sometimes reflects off of them. But if the particles are too tiny, as you guessed, the light will just go right by. Visible radiation from the sun has a wavelength between 400-700 nanometers, which seems really small (a nanometer is a millionth of a millimeter). But greenhouse gas molecules are less than one nanometer in size. So mostly the light just passes by. There is a small amount of “scattering” that happens when sunlight comes in through our atmosphere. When it does happen, it tends to interact with the shortest wavelengths, which are the blue ones. That is why, in fact, our sky looks blue -- the blue light has been scattered around. It is also why the sun looks yellow and sunsets look red/orange. Instead of seeing all the colors, you see only what’s left once the blue has been scattered away. FWIW, this scattering of light by very small objects is called Rayleigh scattering.
Even when atmospheric particles are big, though, the sun doesn’t always reflect off of them. Some of the larger (1000-10,000 nanometer) particles (“aerosols”) that are suspended in the atmosphere for days or weeks include soot from coal plants and forest fires, sulfates from fossil fuel combustion and volcanoes, mineral dust from deserts, and sea salts from ocean spray. The aerosols that cool best are the ones that are light-colored and stay in the air for a while. Black carbon (aka soot) is a dark aerosol, so it absorbs rather than reflects the incoming sunlight. But sulfates, for example, are very reflective.
Source: University of Michigan
Aerosols can cool not only because they reflect sunlight, but because they disrupt clouds, causing them to form more, smaller droplets that better reflect light. If you have seen clouds from a ship’s smokestacks, or contrails from a plane, these are the effect of pollution interacting with ambient water vapor. So aerosols cool not only by reflecting light directly but also by enhancing the ability of water vapor to do the same.
So particle size and color both help explain why incoming radiation reflects only off of some particles. But what about the infrared radiation emitted by the Earth? We know that greenhouse gas molecules trap that radiation, which is how they warm the planet. (See this earlier post
for more on that.) But what about aerosols? They can have a similar effect, particularly when they mix with water, as mentioned above. Water in the atmosphere has both a warming and a cooling effect. Water vapor that has condensed into tiny water droplets, forming clouds, is very reflective and cools the planet. On the other hand, water vapor is a greenhouse gas, and warms the planet. Clouds at night, for example, generally provide a warming effect.
There are many interactions of aerosols with water vapor, clouds, and precipitation, and it’s difficult to tell how they sort out. If you take airplane contrails, for example, it’s not obvious what net effect they might have -- warming or cooling. And it may depend on whether they occur in day or night, over dark areas or light areas, etc. According to a recent report in Nature Communications, contrails warm rather than cool
the planet. In fact, by some estimates, aircraft-induced cloudiness accounts for over half of the warming impact of aircraft flights. But research is ongoing.
The net effect of pollution is fairly well understood to cool the planet. Some researchers recently attempted to quantify this effect. Norwegian climate scientist Bjorn Samset says in this interview
that “if you removed all our emissions today, then the world would rapidly — within a year or two — warm between a half of a degree and 1 degree Celsius additionally.” Yikes. But stay tuned. The impact of aerosols on climate continues to be a very active area of research with many unknowns.
"It's unclear to me what may be "good" or "ok" to burn...dead wood, live trees, biofuels, diesel?? or none of these?"
What is okay to burn? Hmm. AFAIK, none of those is great to burn, at least emissions-wise. But if you think about it from a budget point of view, some things are better than others. As an example, suppose you’ve got an Arctic lake (or a big pond of cow poo) that is emitting lots of methane. If you collect and burn that methane, you are putting a bunch of carbon dioxide into the air. That is bad. But it’s better than putting the methane in the air, at least in the short term. So it is arguably *good* to burn naturally-emitted methane, at least until we learn to do something better.
Here’s another budget-related thought. If you compare burning dead wood to burning fossil fuels, the CO2 from the wood would eventually recycle back into the atmosphere over a sufficiently long time, while the fossil fuel could have just stayed buried in the ground. So it’s arguably better to burn wood than fossil fuel, since you are “just” accelerating a natural process. But that is a bit of a stretch. There is a longer discussion on that in this recent Smithsonian article
As far as I know, the jury is still out on biofuels like ethanol. I think it’s fair to say that improvements are being made to reduce emissions from growing crops (e.g., sequestering carbon in soil), while fossil fuel extraction is getting more emission-intensive (e.g., getting oil from tar sands). But for now the full lifecycle comparison is not great, with biofuels maybe 10-20% better, though even that depends on the time scale at which you look.
Finally, some combustion generates pollutants other than greenhouse gases. That is why some people claim that natural gas is a “clean” fuel, because it doesn’t release those pollutants. But if you buy that, I have a nice low-lying tropical island to sell you…
I think if people really want to burn something, and I’m sure we do, it’s best to figure out hydrogen, which emits only water when burned.
"What is the relative safety of each mode of transportation? For me, it's not simply about price, speed, convenience and environmental issues. I need to make it to my destination in one piece before anything else…. Perhaps in the next blog posting, we can see the fatalities per passenger mile traveled."
It’s generally reported that buses are much safer than driving. There are lots of kinds of buses, though, from transit buses to school buses to the intercity motorcoaches being discussed here. For motorcoaches specifically, and passenger fatalities specifically, they have been improving in recent years.
Source: FMCSA Large Truck and Bus Crash Facts
There was something of a crackdown 5-10 years ago, for example, requiring seat belts (!)
You can also look up per vendor information at FMCSA here
, though I’m told these are not fully adjudicated. In the last 24 months, Greyhound has had 3 fatal crashes and 76 injury crashes. Given they drive five billion passenger miles per year, that is a pretty good rate. On a smaller scale, Megabus’ western subsidiary (Megabus West LLC) has had 0 crashes in the last 24 months.
So, I would say that buses are pretty safe, and much safer than driving. I expect that planes are technically the safest way to get to LA, though, assuming you ignore the impact of their pollution.
Thanks again for all the great questions!
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Posted by CrescentParkAnon.,
a resident of Crescent Park,
on Aug 12, 2019 at 5:58 pm
There is an interview with Richard Muller at Climate One talking about some of the things mentioned previously. The web page is here, which includes the audio interview, and transcript of what was said:
My concern is that I did a Google search for Muller's name and the first thing that came up was a link that totally attacks him in ways that I think if you listen to what he actually says, and listen to his concerns and intent show that attack as exactly the kind of thing he is warning about ... but on both sides.
So, Muller for all his concerned work and care ended up being attacked by both sides - because that is just how ridiculous the whole issue has gotten in the public.
Here is the brief except where he says the data after being adjusted show that Earth's temperature is rising: Web Link
Yeah, yeah. And that's their job. They collected raw data which is virtually unusable, then they analyzed it, and much of their data is then used also by the NASA group, and there's some independent work done in the UK. What -- but in the process of doing this analysis on the data, all three groups were doing a lot of adjustments to the data. And the data have to be adjusted. We see records in which it's clear the temperature jumps from zero degrees all the way up to 32 in one hour. Well, no, someone just started to switch from Celsius to Fahrenheit. So you have to go look at the data and make those adjustments.
But there were problems with this. There were undocumented station location changes. There were -- only a small fraction of the data were being used. Of the stations that were available -- of the nearly 40,000 stations that are available, the group, the NOAA group was using only 8,000 of them. The group in the UK was only using 2,000. There were issues of how they were selecting these. If they were selecting them because they had long records, which was the method that they said they were using, then there's a danger that records with long records were once rural. If they are 200 years old, they almost certainly were once rural. But now they may be deeply buried inside of the city and there's the urban heat island effect. So there are all of these questions, and when I read the papers, I could not find adequate answers to these questions that bothered me. I wanted to know whether global warming was real and whether it's caused by humans. And I could not convince myself when I carefully scrutinized the data.
That was a couple years ago. Last fall, you came out and said you have scrutinized the data. And what was the conclusion?
That the global warming of the past 50 years was very close to what the prior groups had claimed it was.
So they were right?
On this issue they were right. That's right. And I -- my reaction was that the issues that they did not answer, that they didn't answer in their papers and that they didn't answer publicly were issues that they had put a great deal of careful scientific thought into. And they were able to answer it to the standards necessary. Now, there's a difference between being able to come to a conclusion and being able to convince every skeptic that you've come to that conclusion. The details of this get so complex, that their failing was not in the work they had done. Their failing, I felt at the end, was in their ability to address openly all of the issues that had been addressed in such way that an unbiased outside observer coming in would be compelled to accept their conclusions.
Which is you're talking about a communication issue and scientists are often not--
--the best communicators, they agree with what they don't know rather than what [crosstalk].
So they were right.
There's a whole set of issue there.
On the measurement of the temperature change, they were right.
And what was the reaction to your report? You previously were known as a climate skeptic or a denier, and there were some pretty strong words for you. Among some people, you were called a media whore; some people thought you were, you know, a convert. So what was the reaction?
Well, actually, if these had all happened 15 years ago, you wouldn't have such quotes. These days we have the internet--
Thank God for blogs.
And anybody can use the strongest language that they want and put it on. And then even if they retracted, it's there.
Yeah, that was -- so--
So, yeah, a lot of people misunderstood. They -- people still today confuse media reports of what, let's say, I have done with what I have done. And it's like this famous painting, “This is Not a Pipe", it's a painting of a pipe. So people would respond to what people had said I had said, not to what our group, our Berkeley Surface Temperature group had actually said. To try to avoid this, we -- our goal was not just to test the conclusions of the prior groups, but to do it in a far more transparent and open way. So even though they had not yet been accepted for publication, we put them online -- Jim Hanson [crosstalk]--
And you were criticized for putting out non-peer-reviewed literature by people saying, “Hey, this is--
Despite the fact that that's the longest tradition in science. People have done this; we used to call them preprints. And it was -- traditionally I was raised in by Nobel laureate, Luis Alvarez. You send your papers out and you get peer review--
--before you even submit them to the journal.
And this was what I learned was peer review. And now, some people have decided, no, that's not peer review. Now, it's only the journals who decide what's peer review.
And what was the response of some of the funders? The funders of this include Charles Koch with the Koch Industries, Bill Gates, Ann and Gordon Getty. How did they respond to the results?
Richard Muller: I haven't had anything other than expressions of pleasure that we were able to do what we proposed to do.
Greg Dalton: And so you validated the basic measurement of the earth's surface temperature is warming.
Richard Muller: That's right. That's right.
Greg Dalton: That's right.
And we were able to measure with greater accuracy. We were able to address what we felt in an open and clear way the objections that had prevented me from reaching this conclusion in the past. This included the fact that we were able to use all the stations. I have a -- my -- person we hired to do much of the math and computing named Robert Rohde, who is one of the few geniuses I've ever met in my life. And he did a superb job on the statistical analysis on the data -- data work. And we were able to show that the station -- we were able to use all the stations which previous groups couldn't do. We were able to directly look at -- because we could use all the stations, we could pick a subset of the stations that were all rural, none of them in cities. And we could get the global temperature solely from the rural stations. This is the most direct way to address the urban heat island effect. We got the same answer. We can do this because we're using all the stations.
So the science is sound -- you've written about -- there's skeptics, which all scientists should be skeptics, and there's closed-minded deniers. So, talk about the difference then. Did you convince anyone -- did your work convince anyone who's like, “Uh, okay, well, if this guy says it, it must be true."
Well, it's hard to know, but there are deniers on both sides. I mean, they are -- I call the deniers the people who pay no attention to the science.
They don't care -- they start with the assumption that there's a great conspiracy, and that whatever's happening in the climate is good.
If Al Gore says it, it's got to be wrong.
That's right. Now, on the other side, there are the exaggerators who are just as bad as the deniers.
Muller was trying to filter out the Right-wing conspiracy theorist deniers and the Left-wing exaggerators. When you listen to Muller speak you realize he is calmly coming at this issue as objectively as he can, as a good scientist would. My appreciation of his work is because of this, because that is literally the best we can do. Doubling the volume of voices, or the spitefulness of words on either side makes no difference, except in riling up people on both sides who probably at this point do not care about the truth or understand any of it, and yet convincing those people because of elections has become a priority issue.
The question is now, given there is global warming, what can be done in a theoretical sense, and what can be done poltically. I don't like what either side is doing, nor do I think either side is being particularly productive.
If we want to solve the problem we need to listen open-mindedly to experts, and be open to hearing criticism and criticizing. I don't see how this happens in the current political predicament.
I like what Elizabeth Warren had to say, but in order to survive in the Democratic party she has to pay lip service to the Green New Deal, Al Gore, detest nuclear power, and act like she agrees with every Green voice and plan out there, and then somehow transmit that to enough people to get the Democratic nomination, as do all the rest of them on both sides.
If we want a democracy we have to be responsible adults about it because what has been happening for a long time now is that democracy seems to be failing, or it is incompatible with our version of capitalism. The establishment seems not to want the American people to learn, or to know the facts