Climate Modification Schemes
If human activities could change climate, why not change it
on purpose, to suit us better? From 1945 into the 1970s, much effort went
into studies of weather modification. American entrepreneurs tried cloud-seeding
to enhance local rainfall, Russian scientists offered fabulous schemes
of planetary engineering, and military agencies secretly explored "climatological
warfare." The hopes and fears promoted basic research on climate change
by raising large sums of government money and a few provocative ideas.
In the mid 1970s the visionary projects were mostly abandoned. Research turned
instead to controversial "geoengineering" schemes for interventions
that might restrain global warming if it started to become unbearable.
|"Intervention in atmospheric and climatic
matters . . . will unfold on a scale difficult to imagine at present.
. . . this will merge each nation’s affairs with those of every
other, more thoroughly than the threat of a nuclear or any other war
would have done." J. von Neumann(1)
| At the close of the Second World War, a few American scientists
brought up a troublesome idea. If it were true, as some claimed, that
humans were inadvertently changing their local weather by cutting
down forests and emitting pollution, why not try to modify the weather
on purpose? For generations there had been proposals for rainmaking,
based on folklore like the story that cannonades from big battles
brought rain. Now top experts began to take the question seriously.
Perhaps they were inspired by the almost unimaginable technical powers
demonstrated in the war's gigantic bomber fleets and the advent of
nuclear weapons. Whatever the impulse, at the end of 1945 a brilliant
mathematician, John von Neumann, called other leading scientists to
a meeting in Princeton, where they agreed that modifying weather deliberately
might be possible. They expected that could make a great difference
in the next war. Soviet harvests, for example, might be ruined by
creating a drought. Some scientists suspected that alongside the race
with the Soviet Union for ever more terrible nuclear weapons, they
were entering an equally fateful race to control the weather.
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| As the Cold War got underway, U.S. military
agencies devoted significant funds to research on what came to be
called "climatological warfare."(2) Much of this lay behind a curtain of secrecy,
although enough hints were published for attentive members of the
public to see that human manipulation of climate could become a serious
issue. For scientists like von Neumann, the main research thrust was
plain: the nation needed computer modeling of weather systems. For
the chief difficulty in figuring out how to change climate lay in
predicting just how the atmosphere might respond to a given type of
intervention. The only hope for answering that (aside from trying
it out) was with computer models.
| Meanwhile, far more visibly, the famous scientist Irving Langmuir
and his associates at the General Electric company were exploring
a new proposal for rainmaking. Their idea was to "seed" clouds with
a smoke of particles, such as silver iodide crystals, that could act
as nuclei for the formation of raindrops. Langmuir quickly won support
from military agencies, and claimed success in field experiments.
A small but energetic industry of commercial "cloud seeders" sprang
up with even more optimistic claims. Controversy followed, polarizing
scientists, exciting the public and catching the attention of politicians.
As soon as some community attempted to bring rain on themselves, people
downwind would hire lawyers to argue that they had been robbed of
their own precipitation. Concern climbed to high levels of government,
and in 1953 a President's Advisory Committee on Weather Control was
established to pursue the idea. In 1958, the U.S. Congress acted directly
to fund expanded rainmaking research. Large-scale experimentation
was also underway, less openly, in the Soviet Union.(3)
|Military agencies in the U.S. (and presumably in the Soviet Union) supported
research not only on cloud seeding but on other ways that injecting
materials into the atmosphere might alter weather. Although much of
this was buried in secrecy, the public learned that climatological
warfare might become possible. In a 1955 Fortune magazine
article, von Neumann himself explained that "Microscopic layers of
colored matter spread on an icy surface, or in the atmosphere above
one, could inhibit the reflection-radiation process, melt the ice,
and change the local climate." The effects could be far-reaching,
even world-wide. "What power over our environment, over all nature,
is implied!" he exclaimed. Von Neumann foresaw "forms of climatic
warfare as yet unimagined," perhaps more dangerous than nuclear war
itself. He hoped it would force humanity to take a new, global approach
to its political problems.(4)
| Through the 1960s, plans for cloud seeding
and other interventions remained active and controversial. A review
by the U.S. National Academy of Sciences tentatively supported some claims
of success. Government agencies launched competing programs and conducted
several large-scale field trials. The costly research programs were
perpetually on the brink of proving something, but never got truly
convincing results. Many academic meteorologists came to disdain the
whole subject, infested as it was with unfulfilled promises and commercial
hucksters.(5) Despite these misgivings, the U.S.
government spent more than twenty million dollars a year on weather
modification research in the early 1970s.
|The Soviet Union was determined not to be
left behind in any grandiose technology. Little is known of what studies
the Soviets undertook on climatological warfare, but some novel ideas
did become public. One starting-point was a Russian legacy of hydraulic
engineering fantasies, notably an old scheme to divert Siberian rivers.
Why not take the water flowing uselessly into the Arctic Ocean, and
send it south to turn the parched soils of central Asia into farmlands?
The plans were reported in the early 1950s, catching the attention
of the public and scientists in the West, although a decade would
pass before Soviet scientists examined the details in open publications.
These scientists pointed out that the diversion of fresh water would
make the surface layers of the Arctic Ocean more salty. Therefore
much of the ice pack might not form in winter. Wouldn't that mean increased
warmth, a boon to Siberians? A few Russian meteorologists questioned
the scheme, even though Communist authorities frowned upon anyone
who cast doubt over potential engineering triumphs. O.A. Drozdov,
in particular, used weather records to empirically check what could
happen around the Arctic in years of less ice, and reported there
had been serious changes in precipitation.
| An even more gargantuan proposal aimed directly at climate. Around
1956, Soviet engineers began to speculate that they might be able
to throw a dam across the Bering Strait and pump water from the Arctic
Ocean into the Pacific. This would draw warm water up from the Atlantic.
Their aim was to eliminate the ice pack, make the Arctic Ocean navigable,
and warm up Siberia. The idea attracted some notice in the United
States presidential candidate John F. Kennedy remarked that
the idea was worth exploring as a joint project with the Soviets,
and the discussion continued into the 1970s. Such giant engineering
projects were in line with traditional American technological optimism,
and still more with the Communist dogma that "man can really be the
master of this planet." As the title of an enthusiastic Russian publication
put it, the issue was "Man versus Climate." However, it was hard to
tell whether giant projects such as a Bering Dam made sense. Mikhail
I. Budyko, the most prominent Russian climate expert, pointed out
that the effects of such interventions would be unpredictable, and
he advised against them.(6)
| A more feasible scheme would be to spread
particles in the atmosphere, or perhaps directly on the ground. Beginning
around 1961, Budyko and other scientists speculated about how humanity
might alter the global climate by strewing dark dust or soot across
the Arctic snow and ice. The soot would lower the albedo (reflection
of sunlight), and the air would get warmer.(7)
Spreading so much dust year after year would be prohibitively expensive.
But according to a well-known theory, warmer air should melt some
snow and sea-ice and thus expose the dark underlying soil and ocean
water, which would absorb sunlight and bring on more warming. So once
dust destroyed the reflective cover, it might not re-form.
| Russian scientists were not sure whether this would be wise, and
scientists elsewhere were still more dubious. In 1971 a group of American
experts said that "deliberate measures to induce arctic sea ice melting
might prove successful and might prove difficult to reverse should
they have undesirable side effects."(8*)
As the respected British climate expert Hubert Lamb suggested, before
taking any action it seemed like "an essential precaution to wait
until a scientific system for forecasting the behavior of the natural
climate... has been devised and operated successfully for, perhaps,
a hundred years."(9)
time, the early 1970s, feelings about human relations with the natural
environment had undergone a historic shift. Many technologies now
seemed less a triumph of civilized progress than wicked transgressions.
If it were true, as some scientists claimed, that human emissions
were inadvertently changing the entire global climate, the chief result
seemed to be droughts and other calamities. As for deliberate rain-making
attempts, if they were successful (which remained far from proven)
they might only be "stealing" the rain from farmers downwind
who would have gotten it instead. Such projects might even harm the
very people who got the rain. For example, a 1972 U.S. government
rain-making operation in South Dakota was followed by a disastrous
flood, and came under attack in a class-action lawsuit. One cloud-seeding
airplane was even shot at. An increasing number of people objected
in principle to any such meddling with natural processes. The idea
of changing the weather had shifted from a benign dream of progress
to a nightmare of apocalyptic risk. Between 1972 and 1975 the U.S.
government dramatically cut its budget for weather modification.(10)
(Attempts persisted here and there; for example, the Chinese government pursued rainmaking extensively in the early 21st century.)
| Meanwhile the U.S. government
had secretly been spending many millions of dollars on a grand experiment
in actual climatological warfare. The Department of Defense directed
extensive cloud-seeding over the Ho Chi Minh Trail, hoping to increase
rainfall and bog down the North Vietnamese Army's supply line in mud.
Hints about the program were leaked in 1971, but the public did not learn the full extent of the effort until 1974, two years after it wound down in failure. Many people were dismayed when they learned
of the experiment. There followed a series of resolutions, in bodies
from the U.S. Senate to the General Assembly of the United Nations,
outlawing climatological warfare. The movement culminated in a 1976
international convention that foreswore hostile use of "environmental
| Of course we were already modifying the world's atmosphere with
quantities of polluting aerosols and greenhouse gases vastly beyond
anything the most aggressive warrior had imagined. If that raised
a risk of damage to climate, some thought we were obliged to prepare
a remedy. Now when scientists discussed steps to melt arctic snows
or the like, it was not to craft utopian weather, but with the aims
implied in the title that Lamb gave a 1971 review article: "Climate-engineering
schemes to meet a climatic emergency."(12)
| Already back in 1965,
a Presidential advisory panel had suggested that if greenhouse effect
warming by carbon dioxide gas (CO2) ever became a problem, the government
might take countervailing steps. The panel did not consider curbing
the use of fossil fuels. They had in mind what later came to be called "geoengineering" schemes
spreading something across the ocean waters to reflect more sunlight,
perhaps, or sowing particles high in the atmosphere to encourage the
formation of reflective clouds. Some back-of-the-envelope arithmetic
suggested such steps were feasible, and indeed could cost less than
many government programs.(13)
In 1974, Budyko calculated that if global warming ever became a serious
threat, we could counter it with just a few airplane flights a day
in the stratosphere, burning sulfur to make aerosols that would reflect
| For a few years in the
early 1970s, new evidence and arguments led many scientists to suspect
that the greatest climate risk was not warming, but cooling. A new
ice age seemed to be approaching as part of the natural glacial cycle,
perhaps hastened by human pollution that blocked sunlight. Technological
optimists suggested ways to counter this threat too. We might spread
soot from cargo aircraft to darken the Arctic snows, or even shatter
the Arctic ice pack with "clean" thermonuclear explosions.
| Whether we used technological ingenuity against
global cooling or against global warming, Budyko pointed out that
any action would change climate in different ways for different nations.
Attempts at modification, he insisted, "should be allowed only after
the projects have been considered and approved by responsible international
organizations and have received the consent of all interested countries."
The bitter fighting among communities over cloud-seeding would be
as nothing compared with conflicts over attempts to engineer global
climate. Moreover, as Budyko and Western scientists alike warned,
scientists could not predict the consequences of such engineering
efforts. We might forestall global warming only to find we had triggered
a new ice age.(14)
| Such worries revived the U.S. military's interest in artificial climate
change on a global scale. A group at the RAND corporation, a defense
think tank near Los Angeles, had been working with a computer climate
model that originated at the University of California, Los Angeles.
This was normal scientific research, funded by the civilian National
Science Foundation. Around 1970, however, with opponents of the Vietnam
war attacking anything that smelled of militarism, the NSF backed
out of funding work with overt military connections. The RAND group
had to scramble to find support elsewhere. They turned to the Advanced
Research Projects Agency of the Department of Defense. ARPA was meanwhile
on the lookout for computing projects that could justify the funds
it had lavished on its ILLIAC supercomputer. The menace of Soviet
climate engineering schemes gave a plausible rationale. ARPA awarded
the project millions of dollars, a secret classification, and a code
name, NILE BLUE. The money supported a variety of large-scale computer
studies and even some work on ancient climates. Nothing of obvious
military significance turned up, but the program's results proved
useful for other climate scientists. After a few years the program
was demilitarized. The NSF took over funding as work with the RAND
model migrated to the University of Oregon, where it contributed to studies of global warming.(15)
| As environmental concerns grew more widespread and sophisticated,
experts and the public alike demanded a cautious approach to any intervention.
A 1977 National Academy of Sciences report looked at a variety of grand schemes we might
use to reduce global warming, should it ever become dangerous—for
example, massive planting of forests to soak up CO2 from the atmosphere. The experts
could not muster much optimism for any of these schemes. The panel
thought that a turn to renewable energy resources seemed a more practical
| People nevertheless continued to come up with
projects we might pursue if greenhouse warming made us desperate enough.
To cite another of the many ideas, we could collect CO2 from the furnaces where coal was burned, compress it into a liquid,
and inject it into the depths of the Earth or the oceans. That sounded
like an engineer's fantasy, but studies indicated it might in fact
be done at reasonable cost.(17) Another fantastic yet perhaps feasible
proposal was to fertilize barren tracts of the oceans with trace minerals.
In the 1990s, calculations and field trials suggested that an occasional
tanker load of iron compounds could induce massive blooms of plankton.
The creatures would absorb carbon and take it to the ocean bottom
when they died. However, scientists could not be sure whether in the
end that really would lower the total of greenhouse gases in the
|Dozens of other schemes for mitigating the
greenhouse effect were published, ranging from modest practical improvements
in energy systems (for example, energy-efficient light bulbs) to futuristic
visions (vast mirrors in space to reflect sunlight!?). When a National Academy of Sciences
panel convened in 1991 to catalog the options, the members got into
a long and serious debate over whether to include the grand "geoengineering"
ideas. Might hopes of a future fix just encourage people to avoid
the work of restricting greenhouse gas emissions? The panel reluctantly
voted to include every idea, so that preparations could start in case
the climate deteriorated so badly that radical steps would be the
lesser evil. Their fundamental problem was the one that had bedeviled
climate science from the start if you pushed on this intricate
system, nobody could say for sure what the final consequences might
|"Weather modification," a participant had written ruefully back
in 1974, "is based on sound physical principles that cannot be applied
precisely in the open atmosphere because several processes are interacting
together in a manner difficult to predict." Moreover, attempts to
change the weather "are superimposed upon natural processes acting,
perhaps indistinguishably, to the same or opposite effect.... Therefore
it should not be surprising that the history of weather modification
is one of painfully slow progress."(20) Much the same could be said of research on climate modification.
|As the levels of global temperature and greenhouse gases continued
to climb in tandem, the debate dragged on, largely below the level
of public awareness. In 1997 the famous nuclear-bomb expert Edward
Teller caught some attention with an essay in the Wall Street
Journal, claiming that it would cost only a billion dollars
a year to put a sun-screen in the stratosphere. He argued that "if
the politics of global warming require that 'something must be done',"
America should devote its technical prowess to preparing such a
response. Most people who followed the debate distrusted that kind
of high-technology vision (which Teller represented only too well,
as chief proponent of a multi-billion-dollar "Star Wars"
project that had ignominiously failed to invent lasers that could
shoot down ballistic missiles).(21) Others continued to insist that the world should prepare
to take emergency action, just in case. But few were willing to
plunge into studies, and still fewer wanted to fund them.
|As the world began to visibly suffer from global warming, scientists revisited the issue. In 2004 a group gathered at a symposium in Cambridge, England to review the possibilities for climate "Macro-Engineering". Wider attention converged on the issue in 2006 after Paul Crutzen, widely respected
for his Nobel Prize-winning work on ozone, sent the leading journal Climatic Change an article that called for more research
on climate engineering. "Given the grossly disappointing international
political response" to calls to restrict greenhouse emissions,
Crutzen argued that such research should no longer be "tabooed."
His submission roused passionate opposition from some senior colleagues,
who insisted it would be irresponsible to publish the article. Eventually
they accepted a compromise that gave them space for counter-arguments.
|Suppose the climate turned so bad that some nation insisted on launching a geoengineering project? Crutzen and
his supporters argued that it would be best to have research on hand
in advance to point out the true possibilities and pitfalls. Another respected senior climate scientist followed up with calculations reaffirming that it was economically feasible to spread sulfate particles in the stratosphere to hold back warming. Yet Crutzen
himself admitted there was a risk that hopes for a cheap technical
fix would be used "to justify inadequate climate policies." (22*)
|Over the next few years the hope that geoengineering would solve the problem of global warming was indeed taken up by people who opposed government regulation of greenhouse gases. The debate grew intense. Not only a single nation, but even a private group, could engage in climate engineering. Two companies were founded that proposed to fertilize the oceans and get paid for offsetting carbon emissions elsewhere. Sea trials failed to prove that the results would be beneficial, and legal battles erupted, exposing the lack of any framework of international law to deal with such initiatives. In 2008 an international agreement declared a moratorium on large-scale ocean fertilization experiments. But pressure for studies of every option persisted. In 2021 the National Academy of Sciences called for a substantial research program on ocean fertilization, along with related ideas such as large-scale seaweed farming (the marine equivalent to planting forests).(23)
|Ocean fertilization was only one approach to what was coming to be called "Carbon capture and storage" (CCS). Capturing CO2 as it was emitted from power plants was probably feasible at a cost of perhaps a fifth of the plant's energy production. The gas could be stored underground or deep in the oceans, although it would be hard to guarantee it would stay there. CCS could only affect a fraction of CO2 emissions and did not touch the other greenhouse gases.
|It was also possible to extract CO2 from the atmosphere itself biologically, through better management of forests, agricultural soils, and the like. The gas could also be removed directly by combining it with calcium or through some other chemical or physical process. Entrepreneurs pursued dozens of ideas, hoping for a technological breakthrough that would make massive carbon removal economically and politically feasible. Indeed the commitment that nations made in the 2015 Paris Agreement to keep the global temperature rise well below2°C could not be met without such "negative emissions." Only the most sanguine imagined that would actually happen. Certainly it was good to plant trees and so forth. But to offset a large amount of emissions would mean rapidly building land-management or industrial systems on a scale approaching the global coal industry.(23a*)
|Computer modelers and experimenters, collaborating under the auspices of the World Climate Research Program, meanwhile continued to explore "solar radiation management," that is, blocking sunlight. Ideas ranged from promoting cloudiness to enhancing the reflectivity of the oceans, but sulfates remained the most plausible method. Any intervention was bound to produce winners and losers, as in the old fights over rainmakers "stealing" precipitation from folks downwind. Preliminary computer studies suggested, for example, that spreading sulfates in the atmosphere might shut down the Asian monsoon. Would India and China stand idly by while drought starved their populations? Still more worrisome, once an intervention began it would have to continue for centuries, regardless of economic disruption or wars. For if the program paused, global temperatures would snap to a hotter level with catastrophic speed. As one team explained, "Coming generations would have to live with the danger of this 'Sword of Damocles' scenario, the abruptness of which has no precedent in the geologic history of climate." Most ominous of all was the likelihood of unexpected consequences. Computer models, tasked with atmospheric physics and chemistry never seen on a planetary scale, could scarcely guess how a given intervention might change weather patterns.
|Some of the scientists who advocated research on climate engineering wanted to be prepared in case cataclysmic climate changes forced a last-ditch attempt to save civilization. Others expected that their findings would persuade people that an intervention was too risky to attempt. In any case it would be far safer and far easier to negotiate restrictions on greenhouse gas emissions now than to deal with the international repercussions of an intervention during a climate crisis.(24)
|The problem was not only means, but ends: whose goals would climate engineering serve? Even the nightmare of climatological warfare could
stalk back into history, strengthened by scientific advances. As a
historian asked, "Who would have the wisdom to dispense drought,
severe winters, or the effects of storms... If, as history shows,
fantasies of weather and climate control have chiefly served commercial
and military interests, why should we expect the future to be different?"(25) The technical, political and ethical problems raised by deliberately
influencing the global climate remained at least as great as the problems
raised by our ongoing unintended influence.
Government: The View from Washington
1. von Neumann (1955),
p. 41 of reprint. BACK
2. For this and all the following see Fleming
(2006); Fleming (2010); Hamblin (2013). Kwa (2001); Kwa (1994); Keith (2000), p.
252; Fleming (2007a), pp. 54-57; A. Spilhaus,
interview by R. Doel, Nov. 1989, AIP. BACK
3. Lambright and Changnon
(1989); Byers (1974); Soviet: Keith (2000), p. 250-51.
4. von Neumann (1955), pp.
5. National Academy of Sciences
(1966); Lambright and Changnon (1989); Byers (1974).
6. Lamb (1971); Lamb (1977), pp. 660-61; for Soviet and other conquest
of nature ideology see Josephson (2002). I
have not seen Lamb's Russian-language references, which include: for diversion,
Adabashev (1966); Drozdov
(1966); for dam, Borisov (1962) ; Budyko (1962);
inadvisable: Budyko (1977), pp. 237-38; for
U.S. reaction, see e.g., National Academy of Sciences
(1966), vol. 2, p. 61; for the whole story, Ponte
(1976), pp. 220-29; Keith (2000), p. 251,
quoting "master of this planet" from Rusin and
Flit (1960). BACK
7. For discussion and references, see Lamb (1977), pp. 46, 660-61, 676, 797; I have not checked his
Russian references, which include Budyko (1961); Budyko (1962); Rakipova (1966);
1966 Rakipova reports in English translation are cited by Sellers
(1969). See Fleming (2010) p. 236-37.
8. Donn and Shaw (1966) (without
reference to Budyko); Fletcher (1966); Sellers (1969) however calculated a temperature rise of
only 7°C if the ice pack were destroyed, probably insufficient to
keep ice from re-forming; Wilson and Matthews (1971), quote p. 182.
9. Lamb (1971), quote p. 95.
10. Ponte (1976), pp.
(2001); on all the foregoing, Fleming (2006). BACK
11. For the public acknowledgment, see New York
Times, May 19, 1974, p. 1, also Shapley (1974).
Indications were already published in 1971 in a Jack Anderson column in
the Washington Post, 18 March 1971, and in the "Pentagon Papers," see
Seymour Hersh, "Weather as a weapon of war," New York Times,
July 9, 1972, p. IV:3; for background and response, see Ponte
(1976), ch. 11; Fleming (2006), pp. 13-14. Convention on the Prohibition of Military or any Other
Hostile Use of Environmental Modification Techniques, UN Treaty Ser. 1108:151.See Harper (2017) for the US government and weather control 1950-1980 in general. BACK
12. Lamb (1971).
13. President's Science Advisory
Committee (1965), estimated cost $500 million per year, p. 127; see National Academy of Sciences (1966), vol. 2, pp. 60-62. The term "geoengineering" may have first appeared in Marchetti (1977) but only became common in the 1990s.
14. Budyko (1977), p. 240; Budyko and Korol (1975),
p. 469; see Fleming (2010), pp. 241ff.; Landsberg (1970), p. 1268. He cites
1968-69 RAND Corp. reports by J.O. Fletcher; for spreading smog from supersonic
transports, see Wilson and Matthews (1971), p. 9; a summary with warnings
is Kellogg and Schneider (1974), pp. 169-70.
15. Hecht and Tirpak (1995),
p. 375; personal communication from John Perry, 2001, and Rapp
16. National Academy of Sciences
(1977); for discussion of Academy reports, see Keith
17. Notably Marchetti (1977).
18. Coate et al. (1996); Chisholm (2000).
19. Schneider (2001), p. 418; National Academy of Sciences (1992). BACK
20. Byers (1974), p.
21. Teller, “The Planet Needs a
Sunscreen,” Oct. 17, 1997. Teller’s 2002 technical paper on
the subject is here.
22. Crutzen (2006);
see the entire Climatic Change special issue on geoengineering,
with commentaries by Cicerone, M.G. Lawrence and others (vol. 77
nos. 3-4, Aug. 2006). On Crutzen see the
essay on other greenhouse gases. Sulfate calculations:
Wigley (2006); a more recent calculation that "solar radiation management" would be easy and cheap:Smith and Wagner (2018). Press reports include Kerr
(2006) and William J. Broad, New York Times, June 27, 2006. For the
history see also Morton (2007). BACK
23. A good summary: Strong (2009). Debate: e.g., the best-selling Levitt and Dubner (2009) and a report issued by Lomborg's center, Bickel and Lane (2009). Good discussions include Inman (2010), Blackstock and Long (2010), Keith et al. (2010), all three published in the same month. National Academies of Sciences (2021). BACK
23a. To fully restore the climate it would not suffice to remove all the extra CO2 that is in the atmosphere. Roughly half of our emissions have been absorbed in the oceans, plants and soil, and it would take centuries to capture this as it returned to the atmosphere, Cao and Caldeira (2010). BACK
24. One computer model: Jones et al. (2010), see Eastham et al. (2021). Damocles: Brovkin et al. (2009), p. 255. For post-1965 history in general see Caldeira and Bala (2017). For the Geoengineering Model Intercomparison Project (GeoMIP) see their site. One broad overview of geoengineering ideas: Boettcher and Schäfer (2017). BACK
25. Fleming (2007), p. 60. BACK
© 2003-2022 Spencer Weart & American Institute of Physics