From the Pacific Northwest National Laboratory:
Earth sunblock only needed if planet warms easily
Planet’s sensitivity to greenhouse gases will determine how much shading could be needed to slow temperature rise
RICHLAND, Wash. – An increasing number of scientists are studying ways to temporarily reduce the amount of sunlight reaching the earth to potentially stave off some of the worst effects of climate change. Because these sunlight reduction methods would only temporarily reduce temperatures, do nothing for the health of the oceans and affect different regions unevenly, researchers do not see it as a permanent fix. Most theoretical studies have examined this strategy by itself, in the absence of looking at simultaneous attempts to reduce emissions.
Now, a new computer analysis of future climate change that considers emissions reductions together with sunlight reduction shows that such drastic steps to cool the earth would only be necessary if the planet heats up easily with added greenhouse gases. The analysis, reported in the journal Climatic Change, might help future policymakers plan for a changing climate.
The study by researchers at the Department of Energy‘s Pacific Northwest National Laboratory explored sunlight reduction methods, or solar radiation management, in a computer model that followed emissions’ effect on climate. The analysis shows there is a fundamental connection between the need for emissions reductions and the potential need for some sort of solar dimming.
“It’s a what-if scenario analysis,” said Steven Smith with the Joint Global Change Research Institute in College Park, Md,, a joint venture between PNNL and the University of Maryland. “The conditions under which policymakers might want to manage the amount of sun reaching earth depends on how sensitive the climate is to atmospheric greenhouse gases, and we just don’t know that yet.”
The analysis started with computer-based virtual worlds, or scenarios, that describe different potential pathways to reduce greenhouse gas emissions, which limits the amount of heat in the earth system due to greenhouse gas accumulation. The researchers combined these scenarios with solar radiation management, a type of geoengineering method that might include shading the earth from the sun’s heat by either brightening clouds, mimicking the atmospheric cooling from volcanic eruptions or putting mirrors in space.
“Solar radiation management doesn’t eliminate the need to reduce emissions. We do not want to dim sunlight over the long term — that doesn’t address the root cause of the problem and might also have negative regional effects. This study shows that the same conditions that would call for solar radiation management also require substantial emission reductions in order to meet the climate goals set by the world community,” said Smith.
How much sun blocking might be needed depends on an uncertain factor called climate sensitivity. Much like beachgoers in the summer, the earth might be very sensitive to carbon dioxide, like someone who burns easily and constantly slathers on the sunscreen, or not, like someone who can get away with SPF 5 or 10.
Scientists measure climate sensitivity by how many degrees the atmosphere warms up if the concentration of carbon dioxide doubles. Smith said if the climate has a medium sensitivity of about 3 degrees Celsius (5.4 degrees Fahrenheit) per doubling of carbon dioxide, “it’s less likely we’d need solar radiation management at all. We’d have time to stabilize the climate if we get going on reducing emissions. But if it’s highly sensitive, say 4.5 degrees Celsius (8.1 degrees Fahrenheit) per doubling, we’re going to need to use solar radiation management if we want to limit temperature changes.”
According to NOAA’s August report, the earth’s temperature has already risen about 0.62 degrees Celsius (1.12 degrees Fahrenheit) since the beginning of the 20th century as the carbon dioxide in the atmosphere has grown from 290 parts per million to 379 parts per million.
But the atmosphere hasn’t reached equilibrium yet — even if humans stopped putting more carbon dioxide into the air, the climate would still continue to change for a while longer. Scientists do not know what temperature the earth will reach at equilibrium, because they don’t know how sensitive the planet is to greenhouse gases.
Further, the study showed that, when coupled with emission reductions, the amount of solar radiation management needed could be far less than the amount generally considered by researchers so far.
“Much of the current research has examined solar radiation management that is used as the sole means of offsetting a doubling of carbon dioxide concentrations. What we showed is that when coupled with emissions reductions, only a fraction of that amount of ‘solar dimming’ will be needed. This means that potential adverse impacts would be that much lower,” said Smith. “This is all still in the research phase. We do not know enough about the impacts of potential solar radiation management technologies to use them at this time.”
The study will also help decision-makers evaluate solar reduction technologies side-by-side, if it comes to that. Smith and his coauthor, PNNL atmospheric scientist and Laboratory Fellow Phil Rasch, devised a metric to quantify how much solar radiation management will be needed to keep warming under a particular temperature change threshold. Called degree-years, this metric can be used to evaluate the need for potential sunlight dimming technologies.
Whether such technologies will be needed at all, time will tell.
This work was supported by the non-profit Fund for Innovative Climate and Energy Research.
Reference: Steven J. Smith and Philip J. Rasch, 2012. The Long-Term Policy 1 Context for Solar Radiation Management, Climatic Change, doi: 10.1007/s10584-012-0577-3. (http://www.springerlink.com/content/31674q46k61p86h7/)
Derek Sorensen says:
October 11, 2012 at 3:13 pm
I’m not at all concerned at the prospect of CO2 increases. I’m very apprehensive at the thought of geo-engineering. Given humankind’s track record of cock-ups when trying to improve on nature, I can’t see any good outcomes from this kind of exercise.
Yep, sounds like a pretty good way to trigger the next glaciation.
But there can be very little if any CO2-AGW. Also the real AGW has been the reduction of cloud albedo by Asian aerosols.
Result – geo-enginering can’t work and isn’t needed.
Philip Bradley: the UHI mechanism is the reduction of convection thereby increasing temperature so radiation can increase to maintain the sum of convective + radiative heat transfer.
All albedo increase does is to increase the temperature rise for a given radiative component.
Never in the field of human endeavour have so many got the science so diametrically wrong!
Russ R. says:
October 11, 2012 at 3:15 pm “If I read this correctly, climate scientists finally admitted 1) that they don’t know what the right value for climate sensitivity is, and 2) that increased cloud cover is a negative feedback.”
Russ, your second point seems particularly worthy of emphasis. I too am under the impression that the higher values of ‘climate sensitivity’ espoused by the climate establishment depend on increased cloud cover being a positive feedback.
Air warmed by additional atmospheric CO2 can hold more water vapour, which amplifies the primary warming effect. All the water vapour in the atmosphere (excepting that directly deposited as dew) must condense out to form clouds. More water vapour means more clouds, or thicker clouds or longer-lasting clouds. Clouds influence surface temperatures in two main ways: (1) they reflect sunlight, thus cooling the surface as compared with clear-sky conditions (negative feedback); (2) they intercept out-going longwave radiation, some of which is then re-radiated back to the surface, thus slowing down surface cooling as compared with clear-sky conditions (positive feedback). Both of these processes can be observed qualitatively without any scientific knowledge or specialised equipment. The big question which divides sceptics from warmers is whether (1) or (2) is uppermost.
If Russ’s understanding of the above press release is correct, the Pacific Northwest National Laboratory seems to have stepped out of line and to be taking up a position contrary to climate establishment orthodoxy and more in line with informed climate scepticism.
I agree with the warmists! What we need is a planet-wide solar blocking filter and this can be done very simply. If you take a look at the following solar spectra…
http://upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Solar_Spectrum.png/220px-Solar_Spectrum.png
http://butane.chem.uiuc.edu/pshapley/GenChem2/A2/SolarSpectrum.jpg
…you will realise how easy it is. The spectra illustrate how greenhouse gases block direct near infra-red radiation massively reducing radiant solar energy at the Earth’s surface. A by-eye integration and realising that E=hv suggests this is about 50W/m^2. The block is to direct radiation of course. Radiation which is absorbed in the higher layers of the atmosphere is re-radiated iso-tropicaly and most of it goes back out to space, the energy thus temporarily absorbed has a reduced residence time.
For those of you who have not quite worked it out, we can increase the efficiency of our atmospheric sun block simply by buring more fossil fuels! As most warmists attest there is a supernatural positive feedback effect which leads to greater evaporation and thus water vapour in the atmosphere so we get a subsequent multiplication in the effectiveness of our solar block.
eco-geek
These loons need locking up. The only result will be the cure being much worse than the disease.
What springs to mind here is the saying:
The road to hell is paved with good intentions…
I wonder when they will remember the concept of nuclear winter and will try for that option.
My experience of the Pacific North-West is that there is no shortage of “sun-block” for at least nine months of the year. Much like the UK… 🙂
Remember “The Matrix”. It all went awry.
So the AGW lunatics would tell us there’s a tipping point of warmth where, once reached, the temperature runs away, but there is no such cold tipping point where some colder temperature, once reached, would cause an ice age.
These people know. They know all. Bow before them.
I don’t know about you all, but I, for one, have total confidence that nothing could possibly go wrong. /sarc
Is the caption even right?
“making the sky brighter and reducing the amount of heat trapped in the atmosphere.”
It seems to me if you block the radiation going to the dark sea, you’re helping to block energy being transferred into he ocean.
Then if you have reflected energy from the cloud, it goes into the atmosphere to await its fate. It may be trapped in the atmosphere, it depends what it hits. So lets assume it hits water vapor. Most of the energy will stay there, which will cause the atmosphere to heat.
How wrong am I.
Coldish says:
”Clouds influence surface temperatures in two main ways: (1) they reflect sunlight, thus cooling the surface as compared with clear-sky conditions (negative feedback); (2) they intercept out-going longwave radiation, some of which is then re-radiated back to the surface, thus slowing down surface cooling as compared with clear-sky conditions (positive feedback). Both of these processes can be observed qualitatively without any scientific knowledge or specialised equipment. The big question which divides sceptics from warmers is whether (1) or (2) is uppermost.”
Well put.
If I could add another divisive question (at least for me) between warmists and skeptics: Since clouds, water vapor, CO2, and other GHG’s slow cooling of the surface by absorption and radiation of IR, does the addition of CO2 really make an appreciable difference in total GHE globally, especially considering the logarithmic nature of CO2 absorption/emission capacity?
As you said the process of slowing cooling can be qualitatively observed. Slightly more quantitatively, a simple temperature drop comparison between winter clear-sky night and overcast night reveals the power of clouds to slow radiant heat loss at/near the surface. Similarly, a simple comparison of overnight temperature drop in a desert to a region of high humidity reveals the ability of water vapor to slow cooling at/near the surface. Clouds and water vapor can easily increase downwelling longwave radiation from less than 100 W/m^2 to greater than 300 W/m^2 while a doubling of CO2 is purportedly to increase downwelling longwave radiation by 3.7 W/m^2. Somehow, I doubt that’s significant even in the middle of the Sahara, perhaps adding a few minutes to the cooling time, most everywhere else it seems obvious this small increase would be overwhelmed by changes in clouds and water vapor therefore hardly making a measurable difference.
http://www.asterism.org/tutorials/tut37%20Radiative%20Cooling.pdf
It never occurs to these people, or if it does they quickly file it away in the distant recesses of their minds, that more sun hitting the earth might be salutary. That the positive effects of warming would greatly outweigh and possible negative ones.
So it has even got a name – Solar Radiation Management.
God protect us from these lunatics!
“Opps” – a quote overheard at some future year when these geo-engineering types realized they just flipped us into the next ice age 500 years early
Clouds are a thermodynamically stable entity. If they gained energy over time they would dissipate. If they lost energy they would rain out. Comparing clear air convection (CAC) with cloud-forming convection (CFC), clouds form at low altitudes (perhaps 5000 ft or lower) and CAC reaches altitudes of 15,000 ft or more. So CAC requires more temperature driving force at the surface to boost air parcels to an altitude where radiation to space is important. This means that in daytime clouds provide more negative feedback than CAC. Overall, a cooling effect.
At night convection stops but the cloud still absorbs radiation from below and still radiates infrared both upward and downward, but the small amount of infrared from the sun is lost, so the cloud migrates upward and the intensity of the radiation it emits is gradually reduced. Overall, a warming effect.
Which wins out? Gray and Schwartz (2011) found that as long it isn’t raining, it is nearly a wash. But precipitation, especially in the tropics, tips the balance strongly in favor of cooling. All of the talk about cloud albedo misses the big actor – precipitation.
http://scienceandpublicpolicy.org/images/stories/papers/reprint/albedo_and_olr.pdf
This geo engineering is crazy. I agree with folks here. changing the amount of incoming solar could have many un intended consequences. They should be required to prove its safe before we let them do anything.
Sadly, we are already geo engineering the planet. We have been for quite some time. We are pouring a substance into the atmosphere that retards outgoing long wave. Murphys law says putting all this c02 in the atmosphere can’t be safe. I suggest folks who want to put c02 into the atmosphere should have to prove its safe.
hehe
Steven Mosher says:
October 12, 2012 at 12:08 pm
“Sadly, we are already geo engineering the planet. We have been for quite some time. We are pouring a substance into the atmosphere that retards outgoing long wave.”
Yes it does, Steven. But in a degree insufficient to counter whatever it is that has brought temperatures to a standstill for these past 15 years while CO2 concentrations continue to rise apace.
higley7 said ”
This is, of course, ignoring the actual Co2 during the 1940s at 440-550 ppm”
Higley7. How about some references / links for that ?
John Mason said ” “Oops” – a quote overheard at some future year when these geo-engineering types realized they just flipped us into the next ice age 500 years early”
“types” is a typo. I think you meant “Russian Roulette Players”, though “lunatics” serves just as well.
When I was working on a Masters thesis Scintillation Neutron Detector, I needed to use a laboratory pulse Amplifier, consisting of two “ring-of-three” feedback amps; and coupling high and low cutoff switchable filters for noise optimisation. The Amplifier, which hadn’t been used for years, was supposed to put out pulses up to 100 Volt peak (valves), but I couldn’t get it to more than 90 Volts peak, and it was a whole lot noisier, than the user’s manual claimed.
My mentor Prof suggested that after so long, perhaps one of the valves might have a low gm, limiting its ability to turn on higher currents. So out came the old “Tube Tester” to check the six valves in the two feedback loops.
OOoops !! maybe the Tube Tester was also on the fritz, because It would not register hardly any gm at all in in any of the six tubes, and the final power output tube, did have a bit of a blue glow inside.
A quick check with some brand new valves used in one of the lab oscilloscopes, proved that the Tube Tester was working A-OK. Those Amplifier tubes were DAADN; maybe pumping Neutrinos instead of electrons; yet the pulse amplifier seemed to be working, but not quite up to snuff.
A brand new set of valves, perked it right up again, and the noise went away, and I easily could get 115 Volt pulses out of it; and no blue glows.
It is totally amazing just what NEGATIVE FEEDBACK will do for hiding almost any kind of pestilence; including dead valves.
I dare say, the earth climate feedback system, will eventually notice Jupiter and Saturn going bass ackwards in their orbits, and maybe throw another log on the fire.
Why are Saturn and Jupiter going backwards; I thought they went around the sun in ellipses; more or less; that epicycle stuff is supposed to be bunkum !
Steven Mosher says:
October 12, 2012 at 12:08 pm
“hehe”
============
It is not Murphys law, so much as the gremlins.
AlecM says:
October 12, 2012 at 1:02 am
Philip Bradley: the UHI mechanism is the reduction of convection thereby increasing temperature so radiation can increase to maintain the sum of convective + radiative heat transfer.
In some cities reduced convection may occur, caused by reduced humidity, as less humid air is denser.
However, where I live (Perth), the urban area is more humid than surrounding rural areas and convection is greater over the city.
All albedo increase does is to increase the temperature rise for a given radiative component.
I think you mean an albedo decrease. And you phrase it like you are disproving my point, when in fact you agreeing with it. Increase albedo and you decrease temperatures.
They’ve been talking about geo-engineering for a long time. Near the beginning of the 20th century, there were plans to melt the Arctic in order to make the climate better.
Geo-engineering teeters on the looney bin. In fact, it mirrors the paranoia of conspiracy theorists and their HAARP theory that HAARP controls the weather. But since climate is full of so many variables and other things which we do not know about, geoengineering could prove impossible. They won’t change the climate; they’ll likely just spend all our taxpayer money on how they think CO2 is such a pollutant.