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Even the best climate models are affected by uncertainty in how much aerosols contribute to global warming. That uncertainty could mean that emissions cuts could reduce warming -- or that it might continue to increase for a while, despite cuts. Those are the conclusions of a recent review published by a University of Washington grad student.  (Source: NOAA)
Researcher calls the conclusions of the UN's IPCC incomplete and flawed

Kyle Armour, a doctoral student in physics at the University of Washington is boldly challenging that certain assertions of the Nobel Prize-winning International Panel on Climate Change, in their current state, may be flawed.  He argues that the UN's suggestion that stopping aerosol emissions will stop warming is misleading [press release].  These conclusions are noteworthy, given the controversial state of warming research and legislation aimed to "stop" global warming.

At issue is various climatology models, collected from published research, that attempt to simulate the effects of changing global climate variables. These variables include changing the levels of an "aerosols" (atmospheric dust) like sea salt or soot from burning fossil fuels; or greenhouse gases (GHGs) like CO2 or methane.  The effects of these variables are dubbed "forcings" (aerosol forcing, GHG forcings, solar forcing, etc.).  Various forcings sum up to predict a net climate change and its contributors by approximate percentage.  

Models are typically fit to current data, but the narrow range that many climate variables have been constrained to in the modern era limits them.  They're also limited by how many variables and effects on those variables they consider.  Last, but not least, they're limited by how accurately and completely we can measure certain variables (e.g. total global aerosol levels).

In this case, Kyle Armour says that current models are flawed in that they fail to consider how high the uncertainty is regarding the amount that aerosols contribute to climate change.  

He says that the aerosols could contribute a lot to climate change, or only a little.  

In the "best case" scenario they would only contribute a little to net warming, thus they would not be masking the effects of GHG-related warming.  If all emissions of aerosols and GHGs stopped (a cessation of fossil fuel burning, and mammalian livestock farming, in short) the aerosols would quickly exit the atmosphere.  GHGs would remain for years at elevated levels, but the net result would be a slight decrease in temperatures by about half a degree Fahrenheit, given that the aerosols were the chief culprits.

In other words, the current temperature, which is about 1.5 degrees Fahrenheit above pre-Industrial Revolution levels would dip to only 1.0 degrees Fahrenheit above that base level -- but wouldn’t return entirely for many years.

Society can obviously not just instantly cut emissions, Mr. Armour acknowledges, but he says that such a scenario would offer justification to emissions cuts.

However, it's also possible that aerosols offer a larger contribution and are masking the effects of GHGs.  In this case, even if emissions stopped, temperatures would continue to rise and likely reach 3.5 degrees Fahrenheit above pre-Industrial Revolution levels, as the GHGs would persist in the atmosphere.  Such a temperature increase would likely cause some of the more severe predicted climate change effects (though it could offer benefits as well).

In other words, Mr. Armour is arguing that uncertainty in the aerosol components of models may lead to the IPCC significantly underestimating the amount of warming that will occur under various scenarios.

Mr. Armour says that keeping this uncertainty in mind is critical and the IPCC needs to do a better job in doing so in its next report.  He states, "This is not an argument to say we should keep emitting aerosols. It is an argument that we should be smart in how we stop emitting. And it's a call to action because we know the warming we are committed to from what we have emitted already and the longer we keep emitting the worse it gets."

One interesting conclusion of the study not explored by Mr. Armour is the question of maximum forcing.  Clearly historically temperatures rose due to increased GHGs, but leveled off (reach equilibrium) or reversed as the global system dampened the warming effects.  (In other words the Earth remained habitable, if a bit hotter, and didn't become some sort of arid, barren fireball.)  This equilibrium may be reached by a number of mechanisms -- radiative heat loss into space/changes in ocean currents/changes in atmospheric water vapor, etc.  The question is what is the "maximum" reachable temperature?  

If Mr. Armour is correct and we may already be locked in to a large temperature rise, the question is whether we'll reach this maximum.  If so, the climate change will already be enacted.  While this will be unfortunate in some ways (population would have to shift, growing areas would shift, etc.) and fortunate in others, humanity would already be forced to adapt to the change.

If indeed a maximum with dampening is destined to be reached, stopping emissions would do little good (unless we can somehow remove a significant quantity of GHGs from the atmosphere, which does not seem currently feasible).  Thus the question of whether fossil fuel and farming emissions should be cut, and if so how much, largely rests on a data set that is largely unknown and uncertain.  Mr. Armour's key conclusion is in noting this, and in noting that the IPCC needs to do a better job informing policy makers (politicians) of this uncertainty.

Mr. Armour's work has been published [abstract] in the journal Geophysical Research Letters.

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RE: primary driver of climate
By rikulus on 2/16/2011 4:17:58 PM , Rating: 1
Primary driver: the Sun. But you really think our "thin little atmosphere" isn't responsible for the climate we experience? Ever taken a f*ing science class? Sorry to be harsh, it's just amazing how stupid some of the statements made on this site are, and it really makes me sad.

Without our "thin little atmosphere", then we would have the same climate as the moon, right? Just driven by the sun. Average high and low daily temperatures on the moon: 107C and -153C. Maybe you don't know Celsius, so that's 225°F and -243°F. Still think the atmosphere doesn't count?

And it doesn't matter if the world's "perfect" climate wasn't in the early 1800's. Global temperatures are rising, there is no debate about that. Sea levels increase as the water expands due to temperature change and as non-floating ice melts. Billions of people live near sea level, and it is going to cost an incredible amount of money to move or protect them. It's not about the Earth becoming a dried up raisin, it's about $$. The cost to stop using fossil fuels (which is easier to quantify, and nobody wants to voluntarily pay) vs the cost of global warming effects (which are harder to quantify, could be many times worse, and we'll have no choice but to pay... well actually, the next generations will have no choice but to pay, which doesn't seem to bother anybody.)

RE: primary driver of climate
By kattanna on 2/16/2011 4:50:52 PM , Rating: 5
Primary driver: the Sun

as the external source, of course.

but i was implying a more terrestrial item, IE the worlds oceans. THATS what drives the worlds climate. the atmosphere is more of an insulating planet.

Ever taken a f*ing science class?

LOL probably far more then you my friend. but thanks for asking instead of jumping to conclusions.

Sorry to be harsh, it's just amazing how stupid some of the statements made on this site are, and it really makes me sad.

and it seems your part of the problem. once again thanks for playing the "jump to wild half arsed conclusions game"

Global temperatures are rising, there is no debate about that

for the most part, correct. though there is some concern about just how proper some of the records are and all the adjustments that keep being made to them.

also, there is debate about whats the primary driver of the change. While the increased levels of CO2 certainly do play a part, its a small part, and gets to be a smaller part of any increase as concentrations rise.

the next generations will have no choice but to pay, which doesn't seem to bother anybody

ahh, yes. and we get to the apocalyptic statements!!

The cost to stop using fossil fuels (which is easier to quantify, and nobody wants to voluntarily pay)

thats not true. there are many, and more everyday who would love to switch off fossil fuels for our electrical energy needs, but there's a loud and vocal group preventing us from doing that...the environmentalists. They have blocked, and continue to block, the US from switching over to cleaner forms of energy, IE nuclear. They also block our ability to recycle our existing waste, which is really odd from a group that loves to recycle everything else, isnt it?

RE: primary driver of climate
By rikulus on 2/16/2011 5:36:53 PM , Rating: 2
Well, I did jump to a conclusion which set me off there, so for that I apologize, one does hear some crazy things on here. Oceans do drive the weather and mediate the climate, but when talking about long term climate change, we are changing properties of the atmosphere that affect it's insulating properties, but the ocean's properties aren't changing. So, the atmosphere is still the primary driver of change. (I'm talking about the oceans ability to absorb and release heat, not absorb CO2, which is really talking about the atmosphere, in terms of climate.)

That wasn't meant to be apocolyptic, just an observation about how a certain large generation treats finite resources and national deficits.

And we can compare science courses any time you'd like. :) actually, you seem like a person that would be nice to have a decent conversation with.

RE: primary driver of climate
By gamerk2 on 2/17/2011 9:48:33 AM , Rating: 2
but the ocean's properties aren't changing.

Incorrect. CO2 would be trapped via chemical reactions for some time, simmilar to how early O2 would have been trapped via reactions with Iron located in the worlds oceans. Only when that oceans ability to contain O2 was exhaused did oxegyn appear in the atmosphere in significant amounts, and you should expect a simmilar behavior with Co2.

RE: primary driver of climate
By kattanna on 2/17/2011 11:05:30 AM , Rating: 2
Oceans do drive the weather and mediate the climate, but when talking about long term climate change, we are changing properties of the atmosphere that affect it's insulating properties, but the ocean's properties aren't changing. So, the atmosphere is still the primary driver of change

actually i see it in reverse. the atmosphere drives the day to day weather, while the oceans drive the long term climate. let me give you some examples of what i mean.

the UK should actually be a much colder place then it is, but because of ocean currents, warmer waters flow into the area transporting heat that has a long term effect on its climate. short term variations in the atmosphere gives it varying weather patterns, but if the ocean currents changed, that would effect its long term overall climate.

same thing with the poles. we didnt have polar ice caps until north and south america joined and closed off the ocean currents that flowed from the pacific to the atlantic.

its all about the heat, IMO. and the oceans can store large amounts of it for long periods of time and move it around very efficiently, while the atmosphere is a poor container of heat.

RE: primary driver of climate
By rikulus on 2/16/2011 5:40:17 PM , Rating: 2
Oh, and from my peerspective, the strongest group keeping us on fossil fuels give chants of "drill baby drill", and those aren't environmentalists.

RE: primary driver of climate
By walk2k on 2/16/11, Rating: -1
RE: primary driver of climate
RE: primary driver of climate
By walk2k on 2/16/2011 5:28:12 PM , Rating: 3
Yeah it's amazing how many expert scientists with advanced degrees in Climatology on the internet LOL

Anyway pretty sure this article is only talking about aerosols not greenhouse gasses.

RE: primary driver of climate
By zozzlhandler on 2/16/2011 8:30:59 PM , Rating: 2
The sea levels may or may not rise. They are certainly not rising as predicted. I have very little faith in any of the predictions made by anyone - I suspect we simply do not know enough to predict, and that our measurements have too high an error margin to e useful in prediction.

RE: primary driver of climate
By Dr of crap on 2/17/2011 10:56:23 AM , Rating: 2
Since you seem like an educated person - what about pre-1800 temps?
We do not know what the "prefect climate" was. Or if there was / is a period of time that the warming cooling cycle stopped and became the perfect weather condition. We have nothing to base that on.

And as you say the almighty dollar will rule. So if it means we need to spend more dollars to NOT add to the warming of the planet with the things we do everyday - it will not happen.
How are you to police the entire world?
Will you stop burning gas and oil and wood and live like Tarzan??
I think I can safely say no you would not!
So I'll burn natural gas to keep my house warm, and I'll commute to work in my gas burning car.
And I don't think you'll find too many people that will GIVE UP their lifestyle so that future people will not have to be over heated. They might say they will, but if you follow them home it will be a different story. Remember the dollar rules. And if they have to spend more it won't happen!

"Vista runs on Atom ... It's just no one uses it". -- Intel CEO Paul Otellini

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