0:00:00.877,0:00:04.807
I'm here to talk to you about something[br]important that may be new to you.

0:00:05.434,0:00:09.131
The governments of the world are about[br]to conduct an unintentional experiment

0:00:09.131,0:00:10.655
on our climate.

0:00:10.909,0:00:16.325
In 2020, new rules will require ships[br]to lower their sulfur emissions

0:00:16.325,0:00:18.441
by scrubbing their dirty exhaust

0:00:18.441,0:00:20.392
or switching to cleaner fuels.

0:00:20.905,0:00:23.562
For human health, this is really good,

0:00:23.562,0:00:25.952
but sulfur particles[br]in the emission of ships

0:00:25.952,0:00:28.713
also have an effect on clouds.

0:00:29.221,0:00:33.082
This is a satellite image of marine clouds

0:00:33.082,0:00:35.008
off the Pacific West Coast[br]of the United States.

0:00:35.008,0:00:38.339
The streaks in the clouds are created[br]by the exhaust from ships.

0:00:38.339,0:00:41.096
Ships' emissions include[br]both greenhouse gases,

0:00:41.096,0:00:44.050
which trap heat over long periods of time,

0:00:44.050,0:00:47.120
and particulates like sulfates[br]that mix with clouds

0:00:47.120,0:00:49.415
and temporarily make them brighter.

0:00:49.920,0:00:53.187
Brighter clouds reflect[br]more sunlight back to space,

0:00:53.187,0:00:55.619
cooling the climate.

0:00:55.619,0:00:57.741
So in fact,

0:00:57.741,0:01:01.019
humans are currently running[br]two unintentional experiments

0:01:01.019,0:01:01.968
on our climate.

0:01:01.968,0:01:06.102
In the first one, we're increasing[br]the concentration of greenhouse gases

0:01:06.102,0:01:07.793
and gradually warming the Earth System.

0:01:07.793,0:01:11.372
This works something like a fever[br]in the human body.

0:01:11.372,0:01:14.535
If the fever remains low,[br]its effects are mild,

0:01:14.535,0:01:18.037
but as the fever rises,[br]damage grows more severe

0:01:18.037,0:01:20.020
and eventually devastating.

0:01:20.020,0:01:22.654
We're seeing a little of this now.

0:01:22.654,0:01:24.351
In our other experiment,

0:01:24.351,0:01:26.736
we're planning to remove[br]a layer of particles

0:01:26.736,0:01:29.970
that brighten clouds and shield us[br]from some of this warming.

0:01:30.546,0:01:33.470
The effect is strongest[br]in ocean clouds like these

0:01:33.470,0:01:39.433
and scientists expect the reduction[br]of sulfur emissions from ships next year

0:01:39.433,0:01:42.284
to produce a measurable increase[br]in global warming.

0:01:43.633,0:01:45.595
Bit of a shocker?

0:01:45.595,0:01:50.034
In fact, most emissions contain sulfates[br]that brighten clouds:

0:01:50.034,0:01:53.880
coal, diesel exhaust, forest fires.

0:01:53.880,0:01:58.112
Scientists estimate that the total[br]cooling effect from emission particles,

0:01:58.112,0:02:00.964
which they call aerosols[br]when they're in the climate,

0:02:00.964,0:02:05.839
may be as much as all of the warming[br]we've experienced up until now.

0:02:06.068,0:02:08.989
There's a lot of uncertainty[br]around this effect,

0:02:08.989,0:02:13.387
and it's one of the major reasons[br]why we have difficulty predicting climate,

0:02:13.387,0:02:17.396
but this is cooling that we'll lose[br]as emissions fall.

0:02:18.185,0:02:21.917
So to be clear, humans[br]are currently cooling the planet

0:02:21.917,0:02:26.778
by dispersing particles into[br]the atmosphere at massive scale.

0:02:26.778,0:02:29.810
We just don't know how much,[br]and we're doing it accidentally.

0:02:30.387,0:02:32.179
That's worrying,

0:02:32.179,0:02:36.195
but it could mean that we have[br]a fast-acting way to reduce warming,

0:02:36.195,0:02:39.763
emergency medicine for[br]our climate fever if we needed it,

0:02:39.763,0:02:42.540
and it's a medicine[br]with origins in nature.

0:02:43.768,0:02:47.340
This is a NASA simulation[br]of Earth's atmosphere

0:02:47.340,0:02:50.168
showing clouds and particles[br]moving over the planet.

0:02:50.168,0:02:54.508
The brightness is the Sun's light[br]reflecting from particles of clouds,

0:02:54.508,0:03:01.643
and this reflective shield[br]is one of the primary ways

0:03:01.695,0:03:03.165
that nature keeps the planet[br]cool enough for humans

0:03:03.838,0:03:04.278
and all of the life that we know.

0:03:04.278,0:03:08.754
In 2015, scientists assessed possibilities[br]for rapidly cooling the climate.

0:03:08.964,0:03:11.408
They discounted things[br]like mirrors in space,

0:03:11.408,0:03:14.255
ping-pong balls in the ocean,[br]plastic sheets on the Arctic,

0:03:14.255,0:03:19.783
and they found that[br]the most viable approaches

0:03:19.783,0:03:23.850
involved slightly increasing[br]this atmospheric reflectivity.

0:03:24.606,0:03:28.990
In fact, it's possible that reflecting[br]just one or two percent more sunlight

0:03:28.990,0:03:30.650
from the atmosphere

0:03:30.650,0:03:34.348
could offset two degrees Celsius[br]or more of warming.

0:03:35.800,0:03:39.459
Now, I'm a technology executive,[br]not a scientist.

0:03:39.459,0:03:42.007
About a decade ago,[br]concerned about climate,

0:03:42.007,0:03:46.432
I started to talk with scientists about[br]potential countermeasures to warming.

0:03:47.251,0:03:50.130
These conversation grew[br]into collaborations that became

0:03:50.130,0:03:54.810
the Marine Cloud Brightening Project,[br]which I'll talk about momentarily,

0:03:54.810,0:03:58.863
and the non-profit policy organization[br]Silver Lining, where I am today.

0:03:59.723,0:04:03.192
I work with politicians, researchers,

0:04:03.192,0:04:05.294
members of the tech industry and others

0:04:05.294,0:04:07.433
to talk about some of these ideas.

0:04:08.239,0:04:11.445
Early on, I met British[br]atmospheric scientist John Latham,

0:04:11.445,0:04:14.301
who proposed cooling the climate[br]the way that the ships do,

0:04:14.301,0:04:16.775
but with a natural source of particles:

0:04:16.775,0:04:19.132
sea salt mist from seawater

0:04:19.585,0:04:23.232
sprayed from ships into areas[br]of susceptible clouds over the ocean.

0:04:23.583,0:04:26.453
The approach became known[br]by the name I gave it then,

0:04:26.453,0:04:28.251
marine cloud brightening.

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Early modeling studies suggested[br]that by deploying marine cloud brightening

0:04:32.526,0:04:36.267
in just 10 to 20 percent[br]of susceptible ocean clouds,

0:04:36.267,0:04:41.191
it might be possible to offset[br]as much as two degrees Celsius of warming.

0:04:41.400,0:04:45.052
It might even be possible[br]to brighten clouds in local regions

0:04:45.052,0:04:48.962
to reduce the impacts caused[br]by warming ocean surface temperatures.

0:04:48.962,0:04:51.760
For example, regions[br]such as the Gulf Atlantic

0:04:51.760,0:04:54.299
might be cooled in the months[br]before a hurricane season

0:04:54.299,0:04:56.766
to reduce the force of storms.

0:04:56.766,0:05:00.754
Or, it might be possible to cool waters[br]flowing onto coral reefs

0:05:00.754,0:05:03.219
overwhelmed by heat stress,[br]like Australia's Great Barrier Reef.

0:05:03.219,0:05:07.090
But these ideas are only theoretical,

0:05:07.090,0:05:10.878
and brightening marine clouds[br]is not the only way

0:05:10.878,0:05:14.263
to increase the reflection[br]of the sunlight from the atmosphere.

0:05:14.263,0:05:19.756
Another occurs when large volcanoes[br]release material with enough force

0:05:19.756,0:05:22.985
to reach the upper layer[br]of the atmosphere, the stratosphere.

0:05:22.985,0:05:25.550
When Mount Pinatubo erupted in 1991,

0:05:25.550,0:05:28.775
it released material into[br]the stratosphere including sulfates

0:05:28.775,0:05:33.212
that mix with the atmosphere[br]to reflect sunlight.

0:05:33.212,0:05:36.498
This material remained[br]and circulated around the planet.

0:05:36.498,0:05:41.299
It was enough to cool the climate[br]by over half a degree Celsius

0:05:41.299,0:05:44.282
for about two years.

0:05:44.282,0:05:50.399
This cooling led to a striking increase[br]in Arctic ice cover in 1992,

0:05:50.399,0:05:54.327
which dropped in subsequent years[br]as the particles fell back to the Earth,

0:05:54.327,0:05:58.391
but the volcanic phenomenon[br]led Nobel Prize Winner Paul Crutzen

0:05:58.391,0:06:01.970
to propose the idea that dispersing[br]particles into the stratosphere

0:06:01.970,0:06:06.557
in a controlled way might be[br]a way to counter global warming.

0:06:06.557,0:06:09.988
Now, this has risks[br]that we don't understand,

0:06:09.988,0:06:11.867
including things like[br]heating up the stratosphere

0:06:11.867,0:06:14.209
or damage to the ozone layer.

0:06:14.209,0:06:17.487
Scientists think that there[br]could be safe approaches to this,

0:06:17.487,0:06:20.958
but is this really where we are?

0:06:20.958,0:06:22.807
Is this really worth considering?

0:06:22.807,0:06:24.865
This is a simulation

0:06:24.865,0:06:27.810
from the US National Center[br]for Atmospheric Research

0:06:27.810,0:06:31.754
Global Climate Model showing[br]Earth surface temperatures through 2100.

0:06:31.754,0:06:36.163
The globe on the left visualizes[br]our current trajectory,

0:06:36.163,0:06:39.428
and on the right, a world where particles[br]are introduced into the stratosphere

0:06:39.428,0:06:41.393
gradually in 2020

0:06:41.393,0:06:43.315
and maintained through 2100.

0:06:43.315,0:06:47.134
Intervention keeps surface temperatures[br]near those of today,

0:06:47.134,0:06:53.144
while without it temperatures rise[br]well over three degrees.

0:06:53.144,0:06:56.514
This could be the difference[br]between a safe and an unsafe world.

0:06:57.554,0:07:01.885
So, if there's even a chance[br]that this could be close to reality,

0:07:01.885,0:07:06.039
is this something[br]we should consider seriously?

0:07:06.039,0:07:09.661
Today, there are no capabilities

0:07:09.661,0:07:11.618
and scientific knowledge[br]is extremely limited.

0:07:11.618,0:07:15.822
We don't know whether these types[br]of interventions are even feasible,

0:07:15.822,0:07:19.152
or how to characterize their risks.

0:07:19.152,0:07:22.004
Researchers hope to explore[br]some basic questions

0:07:22.004,0:07:24.365
that might help us know

0:07:24.365,0:07:26.307
whether or not these might be real options

0:07:26.307,0:07:28.404
or whether we should rule them out.

0:07:28.404,0:07:31.990
It requires multiple ways[br]of studying the climate system

0:07:31.990,0:07:36.002
including computer models[br]to forecast changes,

0:07:36.002,0:07:37.785
analytic techniques like machine learning,

0:07:37.785,0:07:40.954
and many types of observations.

0:07:40.954,0:07:42.377
And though it's controversial,

0:07:42.377,0:07:46.907
it's also critical that researchers[br]develop core technologies

0:07:46.907,0:07:51.275
and perform small-scale[br]real world experiments.

0:07:51.275,0:07:57.117
There are two research programs[br]proposing experiments like this.

0:07:57.117,0:08:00.715
At Harvard, the SCoPEx experiment[br]would release very small amounts

0:08:00.715,0:08:04.059
of sulfates, calcium carbonate, and water[br]into the stratosphere with a balloon

0:08:04.059,0:08:09.776
to study chemistry and physics effects.

0:08:09.776,0:08:11.139
How much material?

0:08:11.139,0:08:14.544
Less than the amount released[br]in one minute of flight

0:08:14.544,0:08:15.747
from a commercial aircraft.

0:08:15.747,0:08:17.806
So this is definitely not dangerous,

0:08:17.806,0:08:21.386
and it may not even be scary.

0:08:21.386,0:08:23.974
At the University of Washington,

0:08:23.974,0:08:27.312
scientists hope to spray[br]a fine mist of salt water into clouds

0:08:27.312,0:08:30.503
in a series of land an ocean tests.

0:08:30.503,0:08:32.776
If those are successful,[br]this would culminate in experiments

0:08:32.776,0:08:36.371
to measurably brighten[br]an area of clouds over the ocean.

0:08:37.018,0:08:40.400
The marine cloud brightening effort[br]is the first to develop any technology

0:08:40.400,0:08:45.067
for generating aerosols for atmospheric[br]sunlight reflection in this way.

0:08:45.067,0:08:48.489
It requires producing[br]very tiny particles --

0:08:48.489,0:08:52.614
think about the mist that comes[br]out of an asthma inhaler --

0:08:52.614,0:08:55.814
at massive scale -- so think[br]of looking up at a cloud.

0:08:56.533,0:08:58.937
It's a tricky engineering problem.

0:08:58.937,0:09:04.065
So this one nozzle the developed generates[br]three trillion particles per second,

0:09:04.065,0:09:06.012
80 nanometers in size,

0:09:06.012,0:09:08.515
from very corrosive saltwater.

0:09:08.515,0:09:12.652
It was developed by a team[br]of retired engineers in Silicon Valley --

0:09:12.652,0:09:14.083
here they are --

0:09:14.083,0:09:19.314
working full time for six years[br]without pay for their grandchildren.

0:09:19.645,0:09:22.273
It will take a few million dollars[br]and another year or two

0:09:22.273,0:09:26.748
to develop the full spray system[br]they need to do these experiments.

0:09:26.748,0:09:30.617
In other parts of the world,[br]research efforts are emerging,

0:09:30.617,0:09:34.262
including small modeling programs[br]at Beijing Normal University in China,

0:09:34.262,0:09:37.287
the Indian Institute of Science,

0:09:37.287,0:09:42.050
a proposed center for climate repair[br]at Cambridge University in the UK,

0:09:42.050,0:09:44.231
and the ?? Fund,

0:09:44.231,0:09:46.904
which sponsors researchers[br]in Global South countries

0:09:46.904,0:09:50.026
to study the potential impacts[br]of these sunlight interventions

0:09:50.026,0:09:52.090
in their part of the world.

0:09:52.090,0:09:54.337
But all of these programs,

0:09:54.337,0:09:56.203
including the experimental ones,

0:09:56.203,0:09:58.801
lack significant funding.

0:09:58.801,0:10:01.736
And understanding these[br]interventions is a hard problem.

0:10:01.736,0:10:04.182
The Earth is a vast, complex system

0:10:04.182,0:10:07.125
and we need major investments[br]in climate models, observations

0:10:07.125,0:10:08.444
and basic science

0:10:08.444,0:10:12.127
to be able to predict climate[br]much better than we can today

0:10:12.127,0:10:16.945
and manage both our accidental[br]and any intentional interventions.

0:10:16.945,0:10:19.387
And it could be urgent.

0:10:19.387,0:10:24.328
Recent scientific reports predict[br]that in the next few decades

0:10:24.328,0:10:26.892
Earth's fever is on a path to devastation:

0:10:26.892,0:10:29.278
extreme heat and fires,

0:10:29.278,0:10:33.139
major loss of ocean life,

0:10:33.139,0:10:35.996
collapse of Arctic ice,

0:10:35.996,0:10:39.832
displacement and suffering[br]for hundreds of millions of people.

0:10:40.477,0:10:44.139
The fever could even reach tipping points[br]where warming takes over

0:10:44.139,0:10:46.462
and human efforts are no longer enough

0:10:46.462,0:10:50.104
to counter accelerating changes[br]in natural systems.

0:10:50.104,0:10:52.339
To prevent this circumstance,

0:10:52.339,0:10:55.007
the UN's International Panel[br]on Climate Change predicts

0:10:55.007,0:10:59.081
that we need to stop[br]and even reverse emissions by 2050.

0:10:59.081,0:11:03.896
How? We have to quickly and radically[br]transform major economic sectors,

0:11:03.896,0:11:08.618
including energy, construction,[br]agriculture, transportation and others.

0:11:08.618,0:11:13.667
And it is imperative that we do this[br]as fast as we can.

0:11:13.667,0:11:15.739
But our fever is now so high

0:11:15.739,0:11:17.945
that climate experts say[br]we also have to remove

0:11:17.945,0:11:20.607
massive quantities of CO2[br]from the atmosphere,

0:11:20.607,0:11:24.047
possibly 10 times all of[br]the world's annual emissions,

0:11:24.047,0:11:26.801
in ways that aren't proven yet.

0:11:26.801,0:11:32.184
Right now, we have slow-moving solutions[br]to a fast-moving problem.

0:11:32.184,0:11:34.350
Even with the most optimistic assumptions,

0:11:34.350,0:11:37.268
our exposure to risk[br]in the next 10 to 30 years

0:11:37.268,0:11:40.377
is unacceptably high in my opinion.

0:11:40.826,0:11:44.764
Could interventions like these[br]provide fast-acting medicine if we need it

0:11:44.764,0:11:48.308
to reduce the Earth's fever while we[br]address its underlying causes?

0:11:48.821,0:11:51.446
There are real concerns about this idea.

0:11:51.446,0:11:54.708
Some people are very worried[br]that even researching these interventions

0:11:54.708,0:11:59.100
could provide an excuse to delay efforts[br]to reduce emissions.

0:11:59.100,0:12:01.875
This is also known as a moral hazard.

0:12:01.875,0:12:04.118
But like most interventions,

0:12:04.118,0:12:07.399
interventions are more dangerous[br]the more that you do,

0:12:07.399,0:12:13.118
so research actually tends to draw out[br]the fact that we absolutely positively

0:12:13.118,0:12:15.937
cannot continue to fill up[br]the atmosphere with greenhouse gases,

0:12:15.937,0:12:18.305
that these kinds of alternatives are risky

0:12:18.305,0:12:23.388
and if we were to use them we would need[br]to use as little as possible.

0:12:24.946,0:12:27.211
But even so,

0:12:27.211,0:12:29.728
could we ever learn enough[br]about these interventions

0:12:29.728,0:12:31.328
to manage the risk?

0:12:31.328,0:12:35.434
Who would make decisions[br]about when and how to intervene?

0:12:35.434,0:12:40.937
What if some people are worse off,

0:12:40.937,0:12:43.181
or they just think they are?

0:12:43.181,0:12:44.550
These are really hard problems.

0:12:44.550,0:12:46.497
But what really worries me

0:12:46.497,0:12:48.696
is that as climate impacts worsen,

0:12:48.696,0:12:52.424
leaders will be called on to respond[br]by any means available.

0:12:53.036,0:12:55.890
I for one don't want them to act[br]without real information

0:12:55.890,0:12:58.958
and much better options.

0:12:58.958,0:13:00.996
Scientists think it will take[br]a decade of research

0:13:00.996,0:13:03.370
just to assess these interventions

0:13:03.370,0:13:06.299
before we ever were[br]to develop or use them.

0:13:06.299,0:13:10.892
Yet today, the global level of investment[br]in these interventions

0:13:10.892,0:13:13.463
is effectively zero.

0:13:13.463,0:13:17.246
So, we need to move quickly

0:13:17.246,0:13:20.040
if we want policymakers[br]to have real information

0:13:20.040,0:13:22.244
on this kind of emergency medicine.

0:13:24.369,0:13:26.737
There is hope!

0:13:26.737,0:13:29.834
The world has solved[br]these kinds of problems before.

0:13:29.834,0:13:33.085
In the 1970s, we identified[br]an existential threat

0:13:33.085,0:13:35.336
to our protective ozone layer.

0:13:35.336,0:13:38.628
In the 1980s, scientists,[br]politicians and industry

0:13:38.628,0:13:42.697
came together in a solution to replace[br]the chemicals causing the problem.

0:13:43.137,0:13:46.623
They achieved this with the only[br]legally binding environmental agreement

0:13:46.623,0:13:48.878
signed by all countries in the world,

0:13:48.878,0:13:50.611
the Montreal Protocol.

0:13:50.842,0:13:52.876
Still in force today,

0:13:52.876,0:13:55.684
it has resulted in[br]a recovery of the ozone layer

0:13:55.684,0:13:58.468
and is the most successful[br]environmental protection effort

0:13:58.468,0:14:00.080
in human history.

0:14:01.074,0:14:03.827
We have a far greater threat now,

0:14:03.827,0:14:08.177
but we do have the ability[br]to develop and agree on solutions

0:14:08.177,0:14:09.703
to protect people

0:14:09.703,0:14:12.535
and restore our climate to health.

0:14:12.741,0:14:16.095
This could mean that to remain safe,

0:14:16.095,0:14:17.863
we reflect sunlight for a few decades

0:14:17.863,0:14:20.681
while we green our industries[br]and remove CO2.

0:14:21.896,0:14:24.717
It definitely means we must work now

0:14:24.717,0:14:29.804
to understand our options[br]for this kind of emergency medicine.

0:14:29.804,0:14:31.594
Thank you,

0:14:31.594,0:14:35.909
(Applause)