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I have heard countless times the perils of global warming and how we should all do our fair share to save the Earth for future generations.

Here is but one example from an NPR article: "Global Warming is Irreversible, says Study"

"People have imagined that if we stopped emitting carbon dioxide that the climate would go back to normal in 100 years or 200 years. What we're showing here is that's not right. It's essentially an irreversible change that will last for more than a thousand years," Solomon says. [in an interview regarding a study published in the Proceedings of the National Academy of Sciences]

Makes trying to improve the state of affairs sound rather hopeless, doesn't it?

Others think that mitigating or reversing the effects of global warming might be possible:

At the US Department Of Energy's Ask a Scientist website (which I realize pales on peer review compared to PNAS...), some creative solutions are offered by a visitor and the scientists who reply:

Visitor: If we do not do enough to thwart Global Warming, and the oceans start to rise, could we use the effects of Nuclear Winter to offset global warming? Of course we would have to be careful about radiation and radioactive contamination by using the cleanest possible nuclear devices.

Reply by Marc Frenau: This is a good question, but fortunately you do not have to use nuclear bombs to put the dust and particles in the atmosphere. The idea is to reflect sunlight back to space and you could do this by putting lots of sulfur particles into the atmosphere. You do not need dust from nuclear explosions, you could just use rockets or supersonic transports or whatever to get the sulfate particles up to the correct height in the atmosphere....

Reply by Don Libby: Actually, some scientists (e.g. Reid Bryson at the University of Wisconsin) believe that there is sufficient dust in the atmosphere already to effectively counter any global warming effect from C02...I wonder if we could not provide the shade with less potential harm than nuclear explosions would cause, such as putting a huge tarpaulin into earth orbit to create a solar eclipse.

While I'm not sure I'd bet on manufacturing a tarp to blot out the sun, is it scientifically reasonable to doubt the irreversibility of global warming?

Couldn't there be some present or future technological countermeasure to global warming that would make it reversible, not irreversible?

DJClayworth
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Paul
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  • or the carbon taxes could raise the money for the technological countermeasure... – Paul Apr 11 '12 at 08:59
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    carbon taxes are in trillions of dollars, while putting sulfur into troposphere might cost as little as 100 million. – vartec Apr 11 '12 at 09:00
  • Paul, this claim seems unfalsifiable. What sort of evidence could be provided that would persuade you that NO future technology could counter global warming? – Oddthinking Apr 11 '12 at 09:05
  • @Oddthinking The claim being challenged is "global warming is irreversible." That can be falsified if someone presents a credible technology countermeasure. Ideally one reviewed in a scientific publication. – Paul Apr 11 '12 at 09:24
  • @Oddthinking as to challenging "global warming could be reversible", that claim might be problematic. However, evidence that it could not be reversed without killing everyone or expending more controlled energy than is readily available planetwide or more uncontrolled energy than is in the world nuclear arsenal would be reasonable evidence that it is irreversible. – Paul Apr 11 '12 at 09:27
  • @Oddthinking Another way to prove that no **future** technology can be used as a countermeasure would be to show that any such technology violates a well known physical law. Something like one of the laws of thermodynamics, or one of the conservation laws. – Paul Apr 11 '12 at 09:41
  • It is also worth asking whether it is worth reversing warming for two reasons. It is not completely obvious that a warmer world is a *worse* world (we are not far off an ice age which is very bad for life). Also, the cost of preventing warming may be far higher than the cost of adapting to it (even if it is bad). – matt_black Apr 11 '12 at 09:41
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    @matt_black I agree that is an interesting and worthwhile question. You might post "Is a warmer world necessarily worse?" as a question but you'd need to document it a bit. The question I've posted is merely whether it is irreversible or not. – Paul Apr 11 '12 at 09:58
  • @Paul: putting sulfur dioxide into troposphere does not require huge amount of energy, nor would it kill anyone. Irreversibility of global warming is based on warmists' faith, not on mainstream science. – vartec Apr 11 '12 at 09:58
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    http://en.wikipedia.org/wiki/Stratospheric_sulfate_aerosols_%28geoengineering%29 – vartec Apr 11 '12 at 10:07
  • How do you reverse something that is not going forward? Ohh you want to change the natural course of nature... that seems anti green though. – Chad Apr 11 '12 at 12:35
  • @Chad: question is about GW, not AGW. – vartec Apr 11 '12 at 14:14
  • @vartec - I know... I just get frustrated with questions that assume that global warming is something we should want to stop, and generally at the same time assume we are creating it. The funny thing is this question could be asked as is global warming man made? – Chad Apr 11 '12 at 14:34
  • @Paul I did post the question a while ago! http://skeptics.stackexchange.com/questions/7499/could-global-warming-be-good-for-life – matt_black Apr 11 '12 at 15:28
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    There might be different answers here depending on timescale: human or geological. Since we are currently (despite human emissions) at a geologically low CO2 point, it seems obvious that the long term answer is yes. But what works on a human history timescale might be different or might not matter. – matt_black Apr 11 '12 at 15:32
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    "Makes trying to improve the state of affairs sound rather hopeless, doesn't it?". Well if you find yourself driving at high speed towards a brick wall, the fact that you are going too fast to stop in time would be a pretty daft reason not to put the brakes on anyway, one would at least hope that taking your foot off the gas might be a good idea. Geoengineering would be a very costly exercise compared to more modest spending on mitigation/adaption. If society is unwilling to pay the costs of mitigation, they are unlikely to pay the much greater cost of geoengineering. ... –  Mar 22 '14 at 17:41
  • The technical problem involved is big, but it is smaller than the socioeconomic problem with geoengineering. –  Mar 22 '14 at 17:41
  • @matt_black so when were CO2 concentrations higher in, say, the last million years? You only have to go back a few tens of thousands of years to get to a time when they were about half present levels. Saying that we are at a "geological low CO2 point" is a rather nuanced presentation of the situation. We have evolved both as a species and a civilisation where CO2 levels were never above about 300pmm. –  Mar 23 '14 at 16:06
  • @DikranMarsupial True-ish. A million years is short term by geological standards. And, moreover, the question of whether humanity thrives in warmer or colder climates is not obviously addressed by the short time we've been around. There isn't enough evidence and the little we have doesn't clearly support the idea that cold is better. Unless you have evidence to the contrary, which would be useful. – matt_black Mar 24 '14 at 23:35
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    But why are geological timescales more relevant than biological ones - we have only existed as a species for about 250,000 years? You are also missing the point about climate change, it is the **change** that causes the need for adaption. Our agriculture for instance is quite highly adapted to the climate conditions we currently have, and it will be difficult to feed the worlds population as we adapt, given that we are already having difficulty feeding everybody as it is. This is especially true in developing countries with high population densities, such as Bangladesh. –  Mar 25 '14 at 09:31
  • Warming scam is over. That's why they call it change instead. It's all about Sun cycles. 11 years, 88 years, 12k years. The COLD ERA is coming and it is inevitable. And no sponsored science said it, it is something directly observable if you look at the Sun. – Overmind Mar 11 '19 at 13:10

2 Answers2

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There isn't much scientific controversy about geoengineering by injecting SO2 into stratosphere being effective in stopping (or even reversing) global warming. However, the opponents of geoengineering call it intentional pollution, argue that results are "hard to predict".

Some peer reviewed references:

"A Combined Mitigation/Geoengineering Approach to Climate Stabilization" T. M. L. Wigley

Abstract

Projected anthropogenic warming and increases in CO2 concentration present a twofold threat, both from climate changes and from CO2 directly through increasing the acidity of the oceans. Future climate change may be reduced through mitigation (reductions in greenhouse gas emissions) or through geoengineering. Most geoengineering approaches, however, do not address the problem of increasing ocean acidity. A combined mitigation/geoengineering strategy could remove this deficiency. Here we consider the deliberate injection of sulfate aerosol precursors into the stratosphere. This action could substantially offset future warming and provide additional time to reduce human dependence on fossil fuels and stabilize CO2 concentrations cost-effectively at an acceptable level.

"Global and Arctic climate engineering: numerical model studies" Ken Caldeira and Lowell Wood

Abstract

We perform numerical simulations of the atmosphere, sea ice and upper ocean to examine possible effects of diminishing incoming solar radiation, insolation, on the climate system. We simulate both global and Arctic climate engineering in idealized scenarios in which insolation is diminished above the top of the atmosphere. We consider the Arctic scenarios because climate change is manifesting most strongly there. Our results indicate that, while such simple insolation modulation is unlikely to perfectly reverse the effects of greenhouse gas warming, over a broad range of measures considering both temperature and water, an engineered high CO2 climate can be made much more similar to the low CO2 climate than would be a high CO2 climate in the absence of such engineering. At high latitudes, there is less sunlight deflected per unit albedo change but climate system feedbacks operate more powerfully there. These two effects largely cancel each other, making the global mean temperature response per unit top-of-atmosphere albedo change relatively insensitive to latitude. Implementing insolation modulation appears to be feasible.

"Transient climate–carbon simulations of planetary geoengineering" H. Damon Matthews and Ken Caldeira

[...] Proposed schemes to reduce incoming solar radiation (e.g., ref. 3) have drawn on the climatic effect of large volcanic eruptions (e.g., Mt. Pinatubo in 1991), which inject sulfate aerosols into the stratosphere and generate global cooling of a few tenths of a degree for several years after an eruption (7). By extension, it is possible that deliberate (and repeated) injection of aerosols into the stratosphere would affect a long-term cooling that could compensate for some (or perhaps all) of the climate warming induced by anthropogenic greenhouse gases. [...]

Mad Scientist
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vartec
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    While such geoengineering schemes address the "overall global temperature" aspect, it's worth pointing out that they would not address increased ocean acidification and would be unlikely to eliminate climate disruption (that is, global rainfall patterns, farmlands, etc.). So while they may address the question-as-stated, if it were reworded to "is global climate change irreversible?" the answer would have to be less optimistic. – Larry OBrien Apr 12 '12 at 18:23
  • @LarryOBrien: but oceans acidification isn't quite the "doomsday threat", so highly unlikely that ppl would accept trillions of dollars in taxes with excuse of preventing it. – vartec Apr 13 '12 at 09:07
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    @vartec Actually ocean acidification is pretty serious. It has huge consequences for oceanic ecosystems which are the basis of most biogeochemical cycles which we rely on to keep the planet habitable. – bon Mar 15 '17 at 23:51
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Global warming due to manmade excess CO2 emissions is reversible, although if species become extinct in the meantime that's not reversible.

Left to nature, the excess CO2 will be removed from the atmosphere via the Carbonate–silicate cycle; however, at the natural rate, this will take a few million years.

Instead, although not without consequences, silicate rocks can be quarried and crushed to artificially enhance the rate of this process (converting silicates to carbonates).

See A Guide to CO2 Sequestration Science Vol. 300, pp. 1677-1678 :

serpentine or olivine rocks rich in magnesium silicates can be mined, crushed, milled, and reacted with CO2. Estimated mining and mineral preparation costs of less than $10 per ton of CO2 seem acceptable, adding 0.5 to 1¢ to a kilowatt-hour of electricity.

DavePhD
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