Carbon soot may be driving the expansion of the tropics – not CO2

From the University of California – Riverside it seems that black carbon soot is driving tropical expansion. How could this be? I thought CO2 was all powerful, so powerful with the strength of 400,000 Hiroshima bombs each day that animals can’t outrun its effects.

Manmade pollutants may be driving Earth’s tropical belt expansion

UC Riverside-led team identifies black carbon and tropospheric ozone as most likely drivers of large-scale atmospheric circulation change in the Northern hemisphere tropics

RIVERSIDE, Calif. — Black carbon aerosols and tropospheric ozone, both manmade pollutants emitted predominantly in the Northern Hemisphere’s low- to mid-latitudes, are most likely pushing the boundary of the tropics further poleward in that hemisphere, new research by a team of scientists shows.

While stratospheric ozone depletion has already been shown to be the primary driver of the expansion of the tropics in the Southern Hemisphere, the researchers are the first to report that black carbon and tropospheric ozone are the most likely primary drivers of the tropical expansion observed in the Northern Hemisphere.

Led by climatologist Robert J. Allen, an assistant professor of Earth sciences at the University of California, Riverside, the research team notes that an unabated tropical belt expansion would impact large-scale atmospheric circulation, especially in the subtropics and mid-latitudes.

“If the tropics are moving poleward, then the subtropics will become even drier,” Allen said. “If a poleward displacement of the mid-latitude storm tracks also occurs, this will shift mid-latitude precipitation poleward, impacting regional agriculture, economy, and society.”

Study results appear in the May 17 issue of Nature.

Observations show that the tropics have widened by 0.7 degrees latitude per decade, with warming from greenhouse gases also contributing to the expansion in both hemispheres. To study this expansion, the researchers first compared observational data with simulated data from climate models for 1979-1999. The simulated data were generated by a collection of 20 climate models called the Coupled Model Intercomparison Project version 3 or “CMIP3.”

The researchers found that CMIP3 underestimates the observed 0.35 degrees latitude per decade expansion of the Northern Hemisphere tropics by about a third. But when they included either black carbon or tropospheric ozone or both in CMIP3, the simulations mimicked observations better, suggesting that the pollutants were playing a role in the Northern Hemisphere tropical expansion.

Next, to ensure that their results were not influenced by intrinsic differences between CMIP3’s 20 models, the researchers expanded the time period studied to 1970-2009, comparing available observed data with simulated data from NCAR‘s Community Atmosphere Model (CMIP3 data did not extend to 1970-2009). They then repeated the exercise with the GFDL Atmospheric Model. Using these models allowed the researchers to directly isolate the effects of black carbon and tropospheric ozone on the location of the tropical boundaries.

As before, they found that the models underestimate the observed Northern Hemisphere expansion of the tropics by about a third. When black carbon and tropospheric ozone were incorporated in these models, however, the simulations showed better agreement with observations, underscoring the pollutants’ role in widening the tropical belt in the Northern Hemisphere.

“Both black carbon and tropospheric ozone warm the tropics by absorbing solar radiation,” Allen explained. “Because they are short-lived pollutants, with lifetimes of one-two weeks, their concentrations remain highest near the sources: the Northern Hemisphere low- to mid-latitudes. It’s the heating of the mid-latitudes that pushes the boundaries of the tropics poleward.”

Allen further explained that with an expansion of the tropics, wind patterns also move poleward, dragging other aspects of atmospheric circulation with them, such as precipitation.

“For example, the southern portions of the United States may get drier if the storm systems move further north than they were 30 years ago,” he said. “Indeed, some climate models have been showing a steady drying of the subtropics, accompanied by an increase in precipitation in higher mid-latitudes. The expansion of the tropical belt that we attribute to black carbon and tropospheric ozone in our work is consistent with the poleward displacement of precipitation seen in these models.”

Black carbon aerosols are tiny particles of carbon produced from biomass burning and incomplete combustion of fossil fuels. Most of the world’s black carbon production occurs in the Northern Hemisphere, with Southeast Asia being a major producer. The same is true of tropospheric ozone, a secondary pollutant that results when volatile organic compounds react with sunlight.

“Greenhouse gases do contribute to the tropical expansion in the Northern Hemisphere,” Allen said. “But our work shows that black carbon and tropospheric ozone are the main drivers here. We need to implement more stringent policies to curtail their emissions, which would not only help mitigate global warming and improve human health, but could also lessen the regional impacts of changes in large-scale atmospheric circulation in the Northern Hemisphere.”

Thomas Reichler, an associate professor of atmospheric sciences at the University of Utah, noted that the new work by the Allen-led team represents a major advance in climate dynamics research.

“For a long time it has been unclear to the research community why climate models were unable to replicate the observed changes in the atmospheric wind structure,” said Reichler, who was not involved in the study. “This work demonstrates now in very convincing ways that changes in the amount and distribution of tiny absorbing particles in the atmosphere are responsible for the observed changes. Since previous model simulations did not account properly for the effects of these particles on the atmosphere, this work provides a surprisingly simple but effective answer to the original question.”

Allen, who conceived the research project and designed the study, was joined in the research by Steven C. Sherwood at the University of New South Wales, Australia; Joel Norris at the Scripps Institution of Oceanography, San Diego; and Charles S. Zender at UC Irvine.

Next, the research team will study the implications of the tropical expansion from a predominantly hydrological perspective.

“The question to ask is how far must the tropics expand before we start to implement policies to reduce the emissions of greenhouse gases, tropospheric ozone and black carbon that are driving the tropical expansion?” said Allen, who joined UCR in 2011.

###

UCR start-up funds to his lab supported the study.

=================================================================

On the other hand, this is yet another modeling study. But, preferring hard data, I find the comparison of these two images quite interesting for the visual correlation they present in India:

Satellite aerosol optical depth (AOD) for the period between Oct. 1, 2009 and April 14, 2010, over India shows the increased thickness of air pollution over the Indo-Gangetic Plain in the northeasetern portion of the country.

Above: Satellite aerosol optical depth (AOD) for the period between Oct. 1, 2009 and April 14, 2010, over India shows the increased thickness of air pollution over the Indo-Gangetic Plain in the northeastern portion of the country. (source: Scripps)

And this one shows the “hot spots” so to speak:

Source: NASA, Dorothy Koch and James Hansen here.

I find it ironic that in the poorest developing places in the world (Africa/India/China), black carbon optical thickness is at its highest, but the developed countries with their massive pollution control agencies like EPA, have smaller amounts by comparison.

Maybe instead of wasting billions on CO2 bureaucracy, a better solution is to improve the energy infrastructure of these places and fix the cooking stove problem.

Note where CO2 seems the highest, it isn’t the equatorial band:

AIRS maps the distribution of carbon dioxide i...

AIRS maps the distribution of carbon dioxide in the atmosphere. (Photo credit: Wikipedia)

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Jenn Oates

Anthony said “How could this be? I thought CO2 was all powerful, so powerful with the strength of 400,000 Hiroshima bombs each day that animals can’t outrun its effects.”
Now, help me out here…was that sarcasm?
🙂

Latitude

so they ride up to the peak of 1999…
….then ride up to 2009
and first declare that the tropics are expanding
We’ll see, first the tropics would have to expand………….this reminds me of the ag maps expanding the growing zones
…and people getting caught with frozen plants

SteveW

So, basically they programmed the effects of both black carbon and ozone into their model, then report the fact that the model responds to changes in input values of both in the manner it was programmed to do?
Groundbreaking stuff.

Stephen Wilde

The tropics stopped widening around 2000. Perhaps earlier but that is when I first noticed. One example is the return of drought to the Sahel after recent greening.
All the recent observations of more meridional jets and blocked weather systems is more evidence. The tropical belts are likely now narrowing again.
Also the decline in hurricane activity due to increasing wind shear at the relevant levels as the polar air masses encroach more often into the upper atmosphere above the hurricane regions.
Stratospheric ozone, the relative sizes of the equatorial and polar air masses and global temperature trends all appear to be linked to solar activity and not CO2 or aerosols or CFCs after all.

John West

”expanded the time period studied to 1970-2009”
There’s something I can’t quite put my finger on, but, for some reason I’m not surprised from the decade of the coming ice age scare to the decade of we’re melting scare there’s been some expansion of the tropics.

So “Black aerosols” are the “wrong kind of aerosols”? ….
Wonder if that’s discrimination 😉
Seriously, though: 0.7 degree? They think they can measure movement of ‘the tropics’ by that much? Riiiiight….
Looks like more modeling fantasy to me.

Louis

If the tropics are expanding due to black carbon, that would mean black carbon is winning over other aerosols that reflect solar radiation. The Alarmists will have to come up with another excuse for the current lack of warming other than aerosols if this is true.

Greg R.

Wait, What? There seems to be more air pollution over land than there is over water? And less CO2 over equitorial waters?
Alarmists had better figure a way to get rid of those pesky algae and phytoplankton before they chomp them all up.
….Speaking of which, has there ever been a study of atmospheric CO2 levels/air pollution levels during high/low plankton/algae blooms in the tropics? Just wondering…..

Latitude

E.M.Smith says:
May 16, 2012 at 1:27 pm
Seriously, though: 0.7 degree? They think they can measure movement of ‘the tropics’ by that much? Riiiiight….
================
snicker 😉
That’s five miles a decade…………………………to us
They said the tropics have “widened” 0.7……that’s 10 miles……five on the top…and five on the bottom
I’m sure they can measure that…………..LOL

DirkH

How much is that in Hiroshimas?

Curious George

Coupling 20 models is the way to increase accuracy. Fascinating!

Mike

[SNIP: Mike, you are pushing the envelope. If all you have is snark and misdirection… -REP]

wikeroy

It is a moving target. Again, and again, and again.

Another model-based study. The CMIP3 models have no basis in reality. We’ve shown that time and again here.

FerdinandAkin

DirkH says:
May 16, 2012 at 1:37 pm
How much is that in Hiroshimas?

Hiroshimas are the wrong units of measure here. What we need is the to use the New Jersey system and describe the expansion of the Tropics in units of “Christies”

Graeme W

Trying to be positive, this is a step in the right direction for science. They’ve come up with a hypothesis as to why the current climate models are inaccurate and they’ve tested those with appropriate parameter changes to see if the climate models would then better fit the observations.
The next step, which isn’t stated in the article, is to then see if those parameter changes match the observations. That is, do the changes they’ve configured for black carbon aerosols and ozone match the observations for the period in question. If they do, then that indicates that they may be on the right track. There would still be a lot of other work to do, though – such as how do their parameter changes affect other outcomes of the models, and if they affect them negatively, then that means that either their hypothesis is wrong and the effect of their changes was just coincidental, or that the climate models are still significantly imperfect.

Tom in Florida

Latitude says:
May 16, 2012 at 1:34 pm
“They said the tropics have “widened” 0.7……that’s 10 miles……five on the top…and five on the bottom”
However, most of the black carbon soot is in the northern hemisphere so perhaps that hemisphere’s tropics have moved 7.5 miles and the southern hemisphere tropics only 2.5 miles. Or perhaps it’s 8 & 2, or even 6 & 4. Only the models know for sure.

Latitude

Tom in Florida says:
May 16, 2012 at 2:23 pm
===========================
Tom, you know in the past 10 years the climate has not changed from Publix to WinnDixie…….;)
In 100 years, you would still not be zone 11……….LOL

Robertvdl

Why is there a high concentration of co2 in Antarctica in july 2008 ? Is there a highway we don’t know of ? Our do they have a barbeque winter.
Or is it the Amundsen-Scott South Pole Station (Webcam offline in SH winter) . The station is completely self-sufficient during the winter, and powered by three generators running on JP-8 jet fuel.
https://en.wikipedia.org/wiki/Amundsen%E2%80%93Scott_South_Pole_Station

Kaboom

Combining 20 climate models that only output nonsense will certainly even out the non and only leave the sense.

This is all very disappointing! I understood that the Science was all settled and that CO2 was responsible for absolutely everything, rain, wind, drought, all that. Now here they go introducing Carbon. Where will it all end.
The target and goalposts have moved yet again just when we thought that we were in the last quarter!

gringojay

Greg R,
Remember that planet started with much higher CO2 & low O2 concentration so that photosynthesizing life (like algae) used a C3 pathway to make their carbon mass. The C4 pathway of fixing carbon into living mass was a later evolutionary development necessitated for adaptation to how planet’s relative level of CO2 decreased & thus O2 increased.
An assumption was/is that most algae stayed with just their original C3 pathway of getting it’s carbon for mass from CO2. Technological mRNA analysis shows there are some algae in the tidal zone that posses what is necessary for both the C3 & the C4 pathways capable of processing carbon mass from CO2’s carbon.
Green algal blooms are counter intuitive, since CO2 solubility goes down (& conversely O2 solubiity goes up) when temperature goes up – like when tidal rhythm makes water shallower & prone to relatively warm. The point is, the seemingly excessive green mass bloom you see is because those algae have significantly shifted over to using the C4 pathway to take advantage of their C4 ability to work better in the locally lower CO2 conditions of warmer tidal water. The mistake is to think that algae only can fix carbon from CO2 via the C3 pathway & thus assume it can only be be blooming in green mass because the algae is simply responding primordially as it started out doing to the high CO2/low O2 planetary conditions of archaic times. (That mistaken premise leads to modeling a deduction that the green algal blooms are now unnatural & due to contemporary “high” CO2.)

Werner Brozek

“For a long time it has been unclear to the research community why climate models were unable to replicate the observed changes in the atmospheric wind structure,”
Is it possible that this is the case since they just had their eye on CO2 and virtually ignored everything else?
As before, they found that the models underestimate the observed Northern Hemisphere expansion of the tropics by about a third. When black carbon and tropospheric ozone were incorporated in these models, however, the simulations showed better agreement with observations, underscoring the pollutants’ role in widening the tropical belt in the Northern Hemisphere.
As we know, they also assumed positive feedbacks for CO2 so a given increase in CO2 causes 3 times as much warming as the CO2 alone. Is it therefore also possible that with negative feedbacks due to CO2, the black carbon and tropospheric ozone explain 100% of the observations; or at least a much larger fraction?

Brian H

Tom in Florida says:
May 16, 2012 at 2:23 pm
Latitude says:
May 16, 2012 at 1:34 pm
“They said the tropics have “widened” 0.7……that’s 10 miles……five on the top…and five on the bottom”
However, most of the black carbon soot is in the northern hemisphere so perhaps that hemisphere’s tropics have moved 7.5 miles and the southern hemisphere tropics only 2.5 miles. Or perhaps it’s 8 & 2, or even 6 & 4. Only the models know for sure.

Or 11 and -1, or 20 and -10, or …

Brian H

Weasel word alert:

the simulations mimicked observations better,

When black carbon and tropospheric ozone were incorporated in these models, however, the simulations showed better agreement with observations, underscoring the pollutants’ role in widening the tropical belt in the Northern Hemisphere.

Mimicked better? Showed better agreement? Underscoring?
Would that be 1%, 10%, or 100% better mimicry? With what error bars? Numberless qualitative handwaving.

View from the Solent

“black carbon soot”. As opposed to what other types of soot?

How much of the world uses charcoal for heat and cooking?

Robert of Ottawa

Burn those coals, boys! If it gets warmer more Northerly, then the amount of new agricultural land that comes into play in Russia (#1 size) and Canada (#2 size) is enormous. Stoke those fires of agricultural and natural production!

Robert of Ottawa

View From The Solent, yes, a redundant expression rather like WASP – White Anglo Saxon Protestant – have you ever seen a Black one? These redundant adjectives are deliberately added to trigger other emotions to support the sell-job.
Now, just to throw a grenade into the fire (after all they do it with skeptics all the time) are the Warmistas racists as they connect Black with Bad?

KenB

Interesting hypothesis albieit based on coupled models playing leap frog or whatever, now do we keep scrubbing out all those emmissions as we have for the past 20 years or so, or geoengineer some more to even up the temperature anomalies, just in case the weak sun isn’t doing what it does best and the planet is actually in freeze mode. Guess the answer is give us more money and we will generate another hypothesis to give us more money…….normal, post normal science?

RoHa

In TV programme last night, one person said (in reference to the carbon tax) “Everyone blames the carbon, but they say nothing about the two oxygen atoms attached.” But it looks as though those oxygen atoms are innocent by-standers after all.

goldie

Hmm, this is interesting. Just to note, there is a strong northern hemispheric bias for anthropogenic pollutants of short to mid duration due to the increased emissions in the Northern Hemisphere and also the difference in Sea Land Ratio (since the oceans are a sink for ozone). My understanding is that there is also a temperature bias, with the Northern hemisphere showing a greater increase over the last 30 – 40 years.
By comparison there appears to be no difference in CO2 levels between the Northern and Southern Hemisphere, which indicates (to my mind) two things. 1) CO2 cannot be the sole arbiter of temperature and 2) whilst CO2 is long lived in the atmosphere one would expect to see some sort of bias towards the source since this is missing it suggests that CO2 has a global source (e.g. the oceans).
In 1993, I reported in a keynote that VOC concentrations (which are pre-cursors to ozone) in London were falling as emissions controls on vehicles took effect on the overall car fleet in the UK. That was not a popular finding because most of the academics in the room were hoping to drum up more research grants (heard that before?). However, it might begin to explain why temperatures have evened off.
Then again it might have absolutely nothing to do with it .

shrnfr

Maybe yes, maybe no. It is certainly a hypothesis that bears further investigation. The time period overlap with the upswing in the AMO bothers me a little. I suppose a proper test would be to make some predictions based on the models as to the effect of the incremental soot generation from the Chinese coal plants. Our plants in the states have been getting cleaner for years. You no longer have the infamous London Fogs of the coal burning Victorian times. So one would expect a stasis in the generation of particles in North America and Europe but an increase in China with consequent differences in observations between the two areas.
Short of such an experiment however, all I expect this to do is to generate more anti-coal hysteria at the EPA. After all we have a consensus you know…

“But our work shows that black carbon and tropospheric ozone are the main drivers here. We need to implement more stringent policies to curtail their emissions, which would not only help mitigate global warming and improve human health”
I do not know about the soot, but no gas can cause warming and ozone is even more of a trace gas than CO2, at less than one hundredth to one thousandths as much. However, the estimates of its ability as a greenhouse gas is 1000-fold that of CO2. That’s just fine as CO2 cannot and does not warm the surface, as claimed by the warmists, then 1000 times nothing is still nothing.
Very simply the greenhouse effect in our atmosphere is junk science. It does not exist. Atmospheric gases can absorb IR and convert a tiny amount to heat energy, but it is small and heat can also be converted to IR. Any IR absorbed and emitted downward has no effect as the surface is warmer than the atmosphere and the 2nd Law of Thermodynamics reigns supreme. No amount of junk science can later real science.
Atmospheric gases do effectively convert heat energy to IR During The Night helping with the rapid loss of temperature during that so rare, even extinct, condition in the climate models that real people call NIGHTTIME.

So, we get rid of all diesel engines to decrease the black soot, which has been decreasing over the years as these engines become more efficient—it must be that the little bit left has decided to be much more influential in response to its decrease. It’s a natural reaction of an inanimate substance when threatened. That fits the tree-hugger view of nature.
To decrease ozone, they will want to remove all electrical motors. Never mind that they run just about EVERYTHING! But, then, destroying the civilized world is part of the agenda, also.

DirkH

40000.0/360= 111.111111111 [ km for one degree ]
0.7*111= 77.7 [ 0.7 degree in km]
77.7/1.6= 48.5625 [ 0.7 degree in miles ]

Latitude says:
May 16, 2012 at 1:34 pm
They said the tropics have “widened” 0.7……that’s 10 miles……five on the top…and five on the bottom

An arc minute in latitude is a nautical mile, so 0.7 degrees is 42 nautical miles, not 10.
It’s still just fiddling with parameters to fit the data.

Eric

It’s man, it’s bad, and we gotta do something now! It’s man, it’s bad, and we gotta do something now! It’s man, it’s bad, and we gotta do something now! /sarc

Doug Allen

The Surface Black Carbon Concentration map shows 40- 100 ng per cubic meter in the Arctic region and probably 0- 20 in the Anarctic region, but the map doesn’t extend that far south. Anthony, I went to the “source,” and it’s a broken link. Is there a map showing the entire Earth that confirms the very low surface black carbon concentration in the Anarctic? I’ve thought and said for a long time that the Arctic and Anarctic melting differences may have nothing to do with CO2 and everything to do with the surface black carbon albedo differences.

#pocket-lining models again…

Philip Bradley

Even though I have been saying for years that aerosols and particulates (black carbon being the main particulate) are the most important driver of climate change, I have a couple of major problems with this study.
Change in a global average isn’t evidence of a global effect. Black carbon is a regional phenomena and I would need to see solid empirical evidence that its effect is global.
The main effect of atmospheric black carbon is scattering and absorption of solar radiation, together with cloud seeding, which warms the troposphere and cools the surface. Energy which would have otherwise reached the surface, is retained in the troposphere and lost to space sooner, thus cooling the climate. Only empirical data will convince me otherwise.

u.k.(us)

“The question to ask is how far must the tropics expand before we start to implement policies to reduce the emissions of greenhouse gases, tropospheric ozone and black carbon that are driving the tropical expansion?” said Allen, who joined UCR in 2011.
====================
The U.S. spends 0.689 trillion dollars on defense to ensure someone can’t say:
“before we start to implement policies to reduce the emissions of greenhouse gases”
Any part of that you didn’t understand ?

blogagog

Off topic – Holy crap! Make sure and uncheck those two boxes before you comment. I received ~50 emails by just leaving the top one checked.

ferdberple

Interesting. Looking at the AIRS 2008 CO2 map, super green California has high CO2 concentration, and tar sand super polluting Alberta Canada has some of the lowest CO2 levels on the planet!
So, while all the hollywood actors and politician talk the talk, they sure as shooting can’t walk the walk.

ferdberple

“For a long time it has been unclear to the research community why climate models were unable to replicate the observed changes in the atmospheric wind structure,”
======
Hang on, the science is settled. The reason the models can’t replicate the observed changes is due to CO2 gumming up the works. Take away the CO2 and the models will be better than 100% accurate. They will be 110% accurate, so says the Team and the IPCC agrees, so it is correct.

Grey Lensman

They clearly did not read this scoop WWF report
http://wwf.panda.org/about_our_earth/all_publications/living_planet_report/
Beamed from space no less

ferdberple

But, But, But the AGW theory of warming says that it was carbon soot that caused the decline in temperatures from 1945-1975 in spite of increasing CO2. AGW theory says it is this same soot now from INdia and China that is holding temperatures down. If China and India clean up their air, AGW theory tells us that temps will skyrocket – or maybe that is the purpose behind this study?

Ah, but the REAL question is … Which is Yin and which is Yang?

Gunga Din

The tropics are moving North? So farm ponds here in Ohio will become beachfront propery?

davidmhoffer

1. We have some models that don’t produce accurate results.
2. We don’t know why they don’t produce accurate results.
3. We apply a fudge factor based on soot and ozone, and get accurate results.
4. We assume from this that the ONLY thing wrong with the models was that they didn’t account for soot and ozone.
5. We never considered that perhaps other portions of the models are also wrong, but off set each other.
Do the models have predictive skill with the soot and ozone included? Can they hindcast?
I’m betting not, and I’m betting they didn’t even think to try. They got the numbers they were expecting to get, so everything else in the model must be correct. How did they decide how much to weight the effects and feedbacks from soot and ozone? On what did they base this? The amount needed to make the model output give the answers they were expecting?