News Section
Stories from Climate Central's Science Journalists and Content Partners

Reducing Sunlight by Geoengineering Will Not Cool Earth

By Tim Radford, Climate News Network

LONDON – Two German scientists have just confirmed that you can’t balance the Earth’s rising temperatures by simply toning down the sunlight. It may do something disconcerting to the patterns of global rainfall.

Two biogeochemists found that water simply doesn’t respond to atmospheric heat and solar radiation in the same way.
Credit: Annett Junginger, EurekAlert

Earlier this year a U.S.-led group of scientists ran sophisticated climate models of a geoengineered world and proposed the same thing. Now Axel Kleidon and Maik Renner of the Max Planck Institute for Biogeochemistry in Jena, Germany, have used a different theoretical approach to confirm the conclusion, and explain why it would be a bad idea.

The argument for geoengineering goes like this: the world is getting inexorably warmer; governments show no sign of drastically reducing greenhouse gas emissions, so why not control the planetary thermostat by finding a way to filter, block, absorb or reflect some of the sunlight hitting the Earth?

Such things can be done by pumping soot or aerosols into the stratosphere to dim the skies a fraction, or even floating mirrors in Earth orbit to reflect some of the sunlight back into space.

Either way, the result is the same: you have global temperature control, tuned perhaps to the average at the beginning of the last century, and you can then go on burning as much petrol or coal as you like.

But now the two biogeochemists at Jena report in the journal Earth System Dynamics that they used a simple energy balance model to show that the world doesn’t work like that. Water simply doesn’t respond to atmospheric heat and solar radiation in the same way.

No Simple Fix

If you make the atmosphere warmer, but keep the sunlight the same, evaporation increases by 2 percent per degree of warming. If you keep the atmosphere the same, but increase the levels of sunlight, evaporation increases by 3 percent  per degree of warming.

Monsoon in Mumbai: Geoengineering would risk disturbing weather systems.
Credit: PlaneMad, Wikimedia Commons via Climate News Network

Kleidon uses the simple analogy of a saucepan on a kitchen stove. “The temperature in the pot is increased by putting on a lid, or by turning up the heat – but these two cases differ by how much energy flows through the pot,” he says.

A stronger greenhouse effect would act as a kind of tighter-fitting atmospheric lid. In the kitchen a lid keeps the water from escaping from the saucepan and at the same time reduces the energy cost. But planetary energetics are not really comparable to kitchen economics.

That is because evaporation itself, and the traffic of water vapor around the planet, plays a powerful role in the making of climate. To change the pattern and degree of evaporation would inevitably disturb weather systems and disrupt agriculture, with unpredictable and potentially catastrophic consequences.

The authors say: “An immediate consequence of this notion is that climate geoengineering cannot simply be used to undo global warming.” 

Tim Radford is a reporter for Climate News Network. Climate News Network is a news service led by four veteran British environmental reporters and broadcasters. It delivers news and commentary about climate change for free to media outlets worldwide.

Comments

By Terry Mock
on December 27th, 2013

You are right to state that ” you can’t balance the Earth’s rising temperatures by simply toning down the sunlight”, however, not all geoengineering practices are saddled “with unpredictable and potentially catastrophic consequences”.

Please don’t throw the baby out with the bath water!...

Sustainable Land Development Goes Carbon Negative – “If we’re serious about halting the rise of – and eventually lowering – CO2 concentration in the atmosphere, biochar could prove the best way. It also allows us to more sustainably manage organic waste from municipalities, croplands, wastewater treatment plants, and a certain amount of residues from forests. The problem, as with all other climate-mitigation approaches, comes with reaching scale. Can biochar be produced to a large enough scale to make a measurable impact? The answer lies in the triple-bottom-line perspective. In other words, the only way this will happen is if it can be produced in ways that meet the needs of people, planet and profit.” http://www.triplepundit.com/2010/09/sldi-project-carbon-negative/

Champion Trees, and an Urgent Plan to Save the Planet – “It’s amazing for one layman to come up with the idea of saving champion trees as a meaningful way to address the issues of biodiversity and climate change. This could be a grass roots solution to a global problem. A few million people selecting and planting the right trees for the right places could really make a difference.” http://www.triplepundit.com/2012/07/man-planted-trees-lost-groves-champion-trees-urgent-plan-save-planet/

Reply to this comment

By dan_in_illinois
on December 27th, 2013

Okay, thanks for the news, I guess.  In fact, the AGW “storyline” seems to be just about dead (see, for example, http://www.climatecentral.org/news/why-the-globe-hasnt-warmed-much-for-the-past-decade-15788).  The truth is that, whether the globe heats up or cools down in the future, there’s not much humans can do to change it.  That includes inadvertent change from CO2 or whatever the latest “catastrophic” gas that is claimed to be causing terrible climate change.

Reply to this comment

By kermit
on December 30th, 2013

Curious position to take, given the evidence. Why do you link to a story that refutes your claim?

And if we humans are causing global warming (which we are), then it is obvious that we can stop it. Sadly, we have to decide this collectively, and greed and ignorance are carrying us inexorably to disaster.

Reply to this comment

By Bob Wiley (Powell River BC, Canada)
on January 8th, 2014

Geo-engineering - mitigating climate change - can be done while conserving biodiversity and increasing food security through organic farming and perennial grass restoration

Reply to this comment

By Dave (Basking Ridge, NJ 07920)
on December 27th, 2013

In order to work well, massive Geo-E schemes require and assume that there is a climate change pathway that can be traced out reversibly by manipulation of a key control so that we can potentially sort of back peddle the planet into some kind of livable safe zone.

Instead, many scientists believe that the premise underlying such schemes is dangerously naïve. This is because the Earth’s climate and eco-systems are not at all that simple and are therefore very unlikely to all respond in a nice, orderly, well behaved or as-intended way to such ‘controls’. The interesting thing about this new study is that it actually puts numbers on the degree of lack of reversibility of global precipitation patterns under massive solar radiation management. There is quite a difference. Obviously that’s an estimate but it is further warning. So let’s not do the actual experiment to confirm it.

BTW: the title misses the point altogether.

Reply to this comment

By Lewis Cleverdon (Wales)
on December 27th, 2013

“The argument for geoengineering goes like this: the world is getting inexorably warmer; governments show no sign of drastically reducing greenhouse gas emissions, so why not control the planetary thermostat by finding a way to filter, block, absorb or reflect some of the sunlight hitting the Earth?
Such things can be done by pumping soot or aerosols into the stratosphere to dim the skies a fraction, or even floating mirrors in Earth orbit to reflect some of the sunlight back into space.
Either way, the result is the same: you have global temperature control, tuned perhaps to the average at the beginning of the last century, and you can then go on burning as much petrol or coal as you like.”

Quite why Climate Central should choose to publish such journalistic tosh is obscure.
The strawman proposed above as being “The argument for geoengineering” has been used as the basis of perhaps a score of articles by opponents of Geo-E in the last two years, often with the deceit of implying that sulphate aerosols Are geoengineering, and almost always with the deceit of pretending that geo-engineering means ‘solar radiation management’ [SRM], as above.

Have tracked developments in Geo-E over the last two decades, it is worth noting that I’ve never yet seem a serious proposal of SRM as an alternative to global emissions control. Not once.

Even the USA’s ‘Bipartisan Policy Committee’ has been at pains to make clear that none of its participants see SRM as anything more than a potentially useful addition to emissions control. At the other end of the spectrum, the UK’s ‘Royal Society’ (that predates all other national academies of science) has made crystal clear in a formal study that both modes of Geo-E (SRM and Carbon Recovery) may have roles to play as accessories to emissions control and should therefore be researched, but that they have no role as an alternative to emissions control.

The actual conclusions reported above “that climate geoengineering cannot simply be used to undo global warming” is thus merely repeating extant science provided by the Royal Society and others. Yet the manner of the reporting gives an impression that this is a damning condemnation of Geo-E as an option, which is wholly untrue and misleading.

Given that the US govt has yet to ‘pledge’ more than a 3.67% cut of CO2 output by 2020 off the legal 1990 baseline, it is obvious that international rivalry is dangerously obstructing the timely mitigation of the climate threat. Numerous highly reputable scientists have affirmed the the value of holding Geo-E capacities as a ‘backstop option’ should the negotiations fail to provide a timely effective treaty. 

Yet a still more pressing concern is that eight potentially major positive feedbacks are already observed to be accelerating, and that all are linked by multiple interactive reinforcement couplings. (For example, Albedo Loss in the form of the decline of arctic sea ice is sending warmer winds over the tundra where their signature is observed in the advance of Permafrost Melt up to 1,500kms inland). This means that the feedbacks are not only accelerated by AGW and, after the timelag of ocean thermal inertia by each one’s warming outputs advancing AGW and thus all the feedbacks; they are also being accelerated by their current interactions via the couplings, thus multiplying the warming they’ll impose after the timelag. This level of integration means that in effect they form a single organic system with a high potential for the rapid escalation of its outputs.

The IPCC’s proposed mitigation under RCP2.6 offers a 2 in 3 chance of respecting a 2.0C ceiling of warming, but this is calculated without the inclusion of the seven major non-linear feedbacks - and so must logically be seen as describing only a fraction of the warming that the best-case of emissions control would impose over the next ~75 years of warming.

From this perspective, both modes of geoengineering will be required to avoid the untenable outcomes of passing 2.0C in terms of the onset of serial global crop failures and terminal ocean acidification, and the stringently supervised research of both modes is the primary factor of their availability. By publishing articles such as that by Radford that give the impression that geoengineering research is pointless and potentially malign, Climate Central is plainly not supporting the application of science to the climate predicament. It would be helpful if someone could explain why it has done so.

Regards,

Lewis

 

Reply to this comment

By Stephen Salter (Edinburgh EH9 3JL)
on December 28th, 2013

Another bit of the Max Planck Institute published a paper in October 2013 which confirms the Kleidon Renner finding for high altitude reductions to the solar input but also showed that this did not apply to low level cooling caused by marine cloud brightening.  This has at least eight possible effects on precipitation working in opposing directions.  Two are quite strong.  Firstly cooling the sea but not the land gives stronger monsoons moving more humid air ashore.  Secondly making drops in marine clouds smaller reduces the chance of rain over the sea and so leaves more to fall when an air mass reaches land. The net effect is shown figure 7 of Niemeier et al.  in doi: 10.1002/2013JD020445.  The reduction in precipitation due to marine cloud brightening is strongly concentrated in reductions over the sea and that there are useful increases in precipitation over several drought-stricken regions.
A computer model run by Bala and Caldeira reported in Climate Dynamics doi: 10.1007/s00382-010-0868-1 showed that the very small reduction in precipitation over the Indian sub-continent was more than offset by reduced evaporation leading to an increase in river run off of 7.52 +- 0.87% despite correcting the thermal effects of double CO2.
A 2013 PhD Thesis by Ben Parkes at Leeds University tested a technique to get an everywhere-to-everywhere transfer function of marine cloud brightening.  We may be able to control precipitation in both directions in many places.
I hope that Kleidon and Renner will try a replication.

Reply to this comment

By judi woolworth donahue (cc ca 95531)
on December 29th, 2013

Geoengineering is a must.Solar dimming happens naturally every time in the instance of a super volcano.Aerosols *technically acid rain droplets* are created higher in the stratosphere,,,where with winds they actually encompass earth entirely+ in stratosphere instead of falling back they stay up years.Those droplets are highly solar reflective + act like millions of mirrors that reflect away incoming heat + radiation which in turn drops temps rapidly to a volcanic winter ice age.The phenomena has happened over 12 times in earths history..If smaller volcanoes created the strato mirror every time we would be in a perp[etual ice age…but smaller volcanoes its rare to get debris + gas high enough..Last instance was Pinatubo 1991 which created a volcanic mist mirror around earth, stayed up 2 years + cooled globally .05 degrees or such which is ALOT….Pinatubo also PROVES geoengineering WILL work to cool…its natural, tried + true + one last thing…The pyramid of giza was created mirror like, religious sects removed the casing,,IF you restore the highly solar reflective casing you SEE a pictogram of smaller volcanic buildings making the big one a super volcanic building,,,coated in mirror it becomes a perfect pictogram of the volcanic mirror phenomena which stops the end of world as ancients predicted, its in their language, it works,,, and no matter what language you speak EVERYONE SEES the same visual…a super volcanic mirror in middle of desert…only one thing in nature + it saves a world

....so even they from the time of Moses they sent the suggestion to geoengineer the most awesome phenomena known to man + save ourselves…..remember no matter how many scientists try to disprove it, God himself used Pinatubo as absolute proof…..but we still need to reduce the co2….

Reply to this comment

By kermit
on December 30th, 2013

Judi, what are you talking about? Pinatubo-sized eruptions have happened dozens of times just in my lifetime. Are you talking about supervolcanos, perhaps? I can’t tell what you mean by “buildings” here. There is no indication that eruptions happen at opportune times. They also have repercussions - the acidity of the oceans is a big problem, and volcanic eruptions do not help there. Nor is it clear that they would be conducive to reliable farm harvests. In any event, we cannot call them up on demand.

The problem is too much of several greenhouse gases, not to much sunlight. This is why for example biochar sequestration is a good idea, although nowhere near a complete solution in itself. It reduces the atmospheric GHG directly, and therefore has few if any undesirable side-effects.

Reply to this comment

By EVsRoll (Carson City, NV, 89703)
on December 31st, 2013

Everybody commenting on this story should be actively participating in GHG reduction by making wise transport choices. We need a grass roots effort here folks. It is all of us, not just Governments and corporations.

Ride a bike, walk, eBike, EV, take transit or car share whenever possible.

Reply to this comment

By Matthias Honegger (Zurich)
on January 6th, 2014

The heading is flat out wrong. Deployment of solar radiation management would in fact cool the earth. It cannot equally compensate for changes in precipitation and temperature, but it can cool. Finding an intermediate level of such interventions could partly compensate warming and would simultaneously reduce global average precipitation (and its distribution). So it is correct to say that solar radiation management cannot perfectly compensate for changes in temperature AND precipitation at the same time.

Reply to this comment

By Clare Swinney (Whangarei, NZ 0110)
on February 27th, 2014

The article left out mention of the elephant in the living room. We have a completely engineered climate system now.  Geoengineering is being used globally, already. The BBC has reported a reduction of about 20% of sunlight under the heading “global dimming.”  Get educated, get rainwater samples tested for the heavy metals they use in their aerosols and help to shine a light on the crimes of climate engineering. Once we reach a critical mass of awareness, the corrupt entities which keep these programs in operation will start to fall. Visit Geoengineeringwatch.org for further information and watch the documentary: Why In The World Are They Spraying? (2012).

Reply to this comment

Name (required):
Email (required):
City/State/Zip:
Enter the word "climate" in the box below:

[+] View our comment guidelines.

Please note: Comment moderation is enabled. Your comment will not appear until reviewed by Climate Central staff. Thank you for your patience.