Future warming likely to be on high side of climate projections, research finds

Nov 08, 2012
Computer models that more accurately depict dry conditions in a key part of the subtropical atmosphere are also more likely to predict greater climate warming from increased greenhouse gases. Each star indicates one of 16 leading global climate models. The left axis ("warming") corresponds to equilibrium climate sensitivity (ECS) in degrees C, which is the amount of warming produced by each model when carbon dioxide concentrations in the atmosphere are doubled over preindustrial values. The bottom axis shows May-to-August relative humidity for a portion of the upper atmosphere between about 20,000 to 30,000 feet in height and between about 10° and 25° latitude S in the southern subtropics. Illustration adapted from Fig. 4 of Fasullo and Trenberth, courtesy AAAS.

Climate model projections showing a greater rise in global temperature are likely to prove more accurate than those showing a lesser rise, according to a new analysis by scientists at the National Center for Atmospheric Research (NCAR). The findings, published in this week's issue of Science, could provide a breakthrough in the longstanding quest to narrow the range of global warming expected in coming decades and beyond.

NCAR scientists John Fasullo and Kevin Trenberth, who co-authored the study, reached their conclusions by analyzing how well sophisticated reproduce observed relative humidity in the tropics and subtropics.

The climate models that most accurately captured these complex moisture processes and associated , which have a major influence on global climate, were also the ones that showed the greatest amounts of warming as society emits more into the atmosphere.

"There is a striking relationship between how well climate models simulate relative humidity in key areas and how much warming they show in response to increasing carbon dioxide," Fasullo says. "Given how fundamental these processes are to clouds and the overall global climate, our findings indicate that warming is likely to be on the high side of current projections."

The research was funded by .

Moisture, clouds, and heat

The world's major , numbering more than two dozen, are all based on long-established physical laws known to guide the atmosphere. However, because these relationships are challenging to translate into software, each model differs slightly in its portrayal of global climate. In particular, some processes, such as those associated with clouds, are too small to be represented properly.

The most common for comparing model projections is (ECS), or the amount of warming that eventually occurs in a model when carbon dioxide is doubled over preindustrial values. At current rates of global emission, that doubling will occur well before 2100.

For more than 30 years, ECS in the leading models has averaged around 5 degrees Fahrenheit (3 degrees Celsius). This provides the best estimate of increase expected by the late 21st century compared to late 19th century values, assuming that society continues to emit significant amounts of carbon dioxide. However, the ECS within individual models is as low as 3 degrees F and as high as 8 degrees F, leaving a wide range of uncertainty that has proven difficult to narrow over the past three decades.

The difference is important to reconcile, as a higher temperature rise would produce greater impacts on society in terms of sea level rise, heat waves, droughts, and other threats.

Clouds are one of the main sticking points, say the NCAR authors. Although satellites observe many types of clouds, satellite failure, observing errors, and other inconsistencies make it challenging to build a comprehensive global cloud census that is consistent over many years.

However, satellites perform better in measuring water vapor, and estimates of the global distribution of relative humidity have become more reliable. Relative humidity is also incorporated in climate models to generate and dissipate clouds.

Fasullo and Trenberth checked the distribution of relative humidity in 16 leading climate models to see how accurately they portray the present climate. In particular, they focused on the subtropics, where sinking air from the tropics produce very dry zones where most of the world's major deserts are located.

The seasonal drying in the subtropics and the associated decrease in clouds, especially during May through August, serve as a good analog for patterns projected by climate models.

"The dry subtropics are a critical element in our future climate," Fasullo says. "If we can better represent these regions in models, we can improve our predictions and provide society with a better sense of the impacts to expect in a warming world."

More accurate humidity yields higher future temperatures

Estimates based on observations show that the relative humidity in the dry zones averages between about 15 and 25 percent, whereas many of the models depicted humidities of 30 percent or higher for the same period. The models that better capture the actual dryness were among those with the highest ECS, projecting a global temperature rise for doubled of more than 7 degrees F. The three models with the lowest ECS were also the least accurate in depicting in these zones.

"Because we have more reliable observations for humidity than for clouds, we can use the humidity patterns that change seasonally to evaluate climate models," says Trenberth. "When examining the impact of future increases in heat-trapping gases, we find that the simulations with the best fidelity come from models that produce more warming."

The authors focused on climate models used for the 2007 assessment by the Intergovernmental Panel on Climate Change. The next-generation models being used for the upcoming 2013 IPCC assessment were found to behave in a similar fashion, as described in a preliminary analysis by the authors in a supplement to their paper.

"In addition to providing a path forward and focus for improving models, results strongly suggest that the more sensitive models perform better, and indeed the less sensitive models are not adequate in replicating vital aspects of today's climate," write the authors in the paper.

Explore further: NASA sees Typhoon Matmo making second landfall in China

More information: A Less Cloudy Future: The Role of Subtropical Subsidence in Climate Sensitivity, Science, 2012.

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User comments : 28

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Parsec
4.1 / 5 (23) Nov 08, 2012
I predict from historical models like the Luddites and the 19th century flat-earth society, that Climate Change denialists will never go away completely. Their numbers will dwindle as they die, or lose credibility from being laughed at. At some point they will become just a puzzling reference in history books.

Meanwhile, society has a serious problem. I strongly suspect that we have already passed one of many tipping points, and that in the next 10-20 years climate will change very rapidly no matter what we do about controlling CO2 emissions.
jyro
1.7 / 5 (24) Nov 08, 2012
Quit trying to control the uncontrollable. Global warming is real and as natural as Earth itself. Use resources to prepare for it.
jonnyboy
1.5 / 5 (24) Nov 08, 2012
get over yourself Parsec.........really?
mountain_team_guy
1.6 / 5 (25) Nov 08, 2012
I'm starting to hear more admission that there is very little we can do to stop the rise in CO2, or climate change itself. No **** Sherlock. How many of you readers bought the notion we were going to all jump on the carbon bandwagon and drive our economy back to the stone age? Even if everything Parsec and others "suspect" about climate change is true, and seriously, how can anyone have no skepticism, there's no point in freaking out about it. If you disagree, are you willing to put your car keys in the trash?
VendicarD
3.7 / 5 (19) Nov 08, 2012
Already done.

"are you willing to put your car keys in the trash?" - MountainTard
orsat
2.1 / 5 (14) Nov 09, 2012
The contribution of clouds to atmospheric warming requires "judgement" from the programmer based on incomplete data.
The mean of 16 guesses is still a guess.
Egleton
3.2 / 5 (18) Nov 09, 2012
Denial
Anger
Bargaining
Depression
Acceptance
Egleton
3.1 / 5 (10) Nov 09, 2012
Noo.. Please dear God, not the Car.
antialias_physorg
4.2 / 5 (15) Nov 09, 2012
I predict from historical models like the Luddites and the 19th century flat-earth society, that Climate Change denialists will never go away completely.

It's helpful to remember that 'climate denialists' are a phenomenon particular to the US. Personally I think it's from the same stock that breeds christian literalists or 'manifest destiny' types.
Accepting that something one does is wrong is hard if one believes that one is chosen by god (or somehow special).

They're 'special', all right. Short-bus special.
Shinobiwan Kenobi
3 / 5 (18) Nov 09, 2012
It's helpful to remember that 'climate denialists' are a phenomenon particular to the US. Personally I think it's from the same stock that breeds christian literalists or 'manifest destiny' types.


As a resident of a red-state (I voted blue!), I can attest that your assesment is accurate.

Accepting that something one does is wrong is hard if one believes that one is chosen by god (or somehow special).

They're 'special', all right. Short-bus special.


Nail-head, meet hammer.
Sinister1811
2.7 / 5 (14) Nov 09, 2012
It's helpful to remember that 'climate denialists' are a phenomenon particular to the US.


If only that were the case. I have seen those same types of people everywhere. In my country, this is now even more self-evident after the introduction of the Carbon Tax. This was demonstrated by a very recent Ninemsn poll, asking the question "do you believe in Climate Change" and 56% of voters voting "no". I also believe that the same [ignorant] phenomenon is prevalent in the UK. On other science websites, I've even seen people from the Philippines showing skepticism towards anthropogenic climate change. It seems that the facts are often ignored no matter how they're presented, in favour of beliefs in conspiracy theories.
88HUX88
4.3 / 5 (11) Nov 09, 2012
yes there are lots of denialists living in the UK, some of them appear on TV and are proud of their opinions, (Clarkson).

the disinformation ploy has worked well here
Sigh
3.9 / 5 (11) Nov 09, 2012
I'm starting to hear more admission that there is very little we can do to stop the rise in CO2, or climate change itself.
We could, given the political will. Guess who is getting in the way.

are you willing to put your car keys in the trash?
Done without for 25 years now, and have rarely missed it.
axemaster
4 / 5 (12) Nov 09, 2012
I only wish that AGW denialists were forced to make good on their beliefs - that they would never receive any assistance from the government for climate change induced damages. They wouldn't be so sure of themselves if they actually had any skin in the game.
rubberman
2.9 / 5 (15) Nov 09, 2012
Mountain team guy thinks that continuous pollution in the name of economic prosperity is a stable state. It is the failure of people with this mindset to recognize that they are the ones ushering in the next "stone age" with this mentality.

Only a jedi could tolerate being surrounded by this level of ignorance...well done Shinobiwan.
Dug
1.8 / 5 (16) Nov 09, 2012
While you can get a consensus of climate change direction among climate "experts," look at the graph folks. There is no consensus among climate models as to how little or how great climate change will be. Even worse, if there is a consensus that climate change is driven by anthropogenic activities, where is the plan to reduce those activities and their source? Computer modeling doesn't constitute science and for all of climate change proponents computer modeling - it still isn't science as much as it is a cult - cults of believers and cults of deniers. Sounds more like religion - which it is. Proof of point - note article simultaneous with this one below under More news stories - "Good News? Green is melting less quickly than predicted."

As a species we have far more serious and immediate problems that are going to limit our reign of ignorance on this planet long before climate change does - which also makes anthropogenic climate change a self-limiting problem.
FrankHerbert
3.5 / 5 (13) Nov 09, 2012
Denial
Anger
Bargaining
Depression
Acceptance


Actually this is wrong. Since conservatives have broken brains their steps of grief look like this.
Denial
Anger
Bargaining
Depression
Denial
Anger
Bargaining
Depression
Denial
Anger
Bargaining
Depression...
PeterD
1.4 / 5 (21) Nov 09, 2012
Exactly the same global warming that is happening now has happened many times, most recently in 800 to 1200 AD. We did not cause it then, and it is very doubtful that we are causing it now. If there are any real scientists out there, they never comment here.
axemaster
4.2 / 5 (10) Nov 09, 2012
Exactly the same global warming that is happening now has happened many times, most recently in 800 to 1200 AD. We did not cause it then, and it is very doubtful that we are causing it now. If there are any real scientists out there, they never comment here.


Huh? Last I checked, I'm a physicist.

(And before you ask, no I'm not giving you my name. I get enough crank emails from people who look me up on the university listings...)
Maggnus
3.9 / 5 (11) Nov 09, 2012
Exactly the same global warming that is happening now has happened many times, most recently in 800 to 1200 AD. We did not cause it then, and it is very doubtful that we are causing it now. If there are any real scientists out there, they never comment here.


This is the typical tripe we have all come to expect from such as you. "Real scientists" couldn't be bothered to comment on such nonsense.

Well, most anyway.

To busy gathering these amazingly resilient things called "facts".
packrat
1 / 5 (8) Nov 10, 2012
Could someone explain something to me? I'm wondering where all the numbers are for the actual HEAT we are putting into the atmosphere. All the numbers on the various gases are interesting but I never see any numbers for heat itself. A lot of those gases are being put there by us using fuel engines, lighting, home heating, cooking, burning waste, etc.... How are those numbers added into the mix? It just seems logical to me that these sources would have more to play in the mix but I almost never see anything about it here or on other science sites.
zz5555
1 / 5 (1) Nov 10, 2012
Packrat,
You can get that information here: http://skepticals...ming.htm .
Basically, that heat is about 1% of the heat added by greenhouse gases so it's negligible.
packrat
1 / 5 (7) Nov 10, 2012
Packrat,
You can get that information here: http://skepticals...ming.htm .
Basically, that heat is about 1% of the heat added by greenhouse gases so it's negligible.


Thank you for the link!

jonnyboy
1.3 / 5 (14) Nov 11, 2012
Denial
Anger
Bargaining
Depression
Acceptance


what a tard.

Actually this is wrong. Since conservatives have broken brains their steps of grief look like this.
Denial
Anger
Bargaining
Depression
Denial
Anger
Bargaining
Depression
Denial
Anger
Bargaining
Depression...

Doschx
1.4 / 5 (10) Nov 12, 2012
Let me take this stance:

I, as a climate change denier, and those like me refuse to curb our consumption and carbon footprint to our dying breath. You can do all you want to help the environment, but what can you do about US? Mock us and present us with irrefutable proof until we slowly dwindle asymptotalally towards extinction? Do you have the luxury of that much time? What, then; will you put us to the sword? Can you possibly triumph over an enemy that has no qualms playing dirty? While you strain and reach and try to get a solar powered fighter off the ground we will burn billions of gallons of jet fuel to fly squadrons of planes over your lakes, your forests, your homes, reducing each to radioactive ash.

No, the only way you can hope to save your planet is to find a way for environmentally friendly industry to out-produce all other variants. Do this and one day our people will be one and the same.
antialias_physorg
4.4 / 5 (7) Nov 12, 2012
You can do all you want to help the environment, but what can you do about US?

a) Ignore it. Try to seek action with the rest of the world.
b) Put tarrifs on products not produced in a climate friendly way.
c) Prohibit use of modes of transportation that do not conform to standards (e.g. by denying airlines the right to land or ships the entry into harbours)

the only way you can hope to save your planet is to find a way for environmentally friendly industry to out-produce all other variants

Production that does not care about its wastes and waste disposal (and which is not made to pay for subsequent damages) will always be cheaper than a production cycle that takes all of these into account. So that path is not an option. There are limits to optimization.

The only way is to get people to understand the problem. This can be done the easy way (education) or the hard way (ever more costly natural disasters)
rubberman
2.3 / 5 (9) Nov 12, 2012
"Mock us and present us with irrefutable proof until we slowly dwindle asymptotalally towards extinction?"

AP went the politically correct route, however the above is the Physorg status quo....since I am not in a position to enact the solutions AP suggests, I'll stick to the status quo.
the enviro mentalist
1 / 5 (7) Nov 14, 2012
can anyone confirm that for every 1 kg of fuel we combust, we suck approximately 3.5kg of oxygen from the atmosphere PERMANENTLY, as the carbon was originally stored underground before it bonded with this oxygen? also please confirm that we generate approximately 3kg of CO2 and 1.5kg of water as byproducts.