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I'm here to talk to you about something
important that may be new to you.
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The governments of the world
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are about to conduct
an unintentional experiment
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on our climate.
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In 2020, new rules will require ships
to lower their sulfur emissions
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by scrubbing their dirty exhaust
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or switching to cleaner fuels.
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For human health, this is really good,
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but sulfur particles
in the emission of ships
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also have an effect on clouds.
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This is a satellite image of marine clouds
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off the Pacific West Coast
of the United States.
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The streaks in the clouds
are created by the exhaust from ships.
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Ships' emissions include
both greenhouse gases,
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which trap heat over long periods of time,
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and particulates like sulfates
that mix with clouds
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and temporarily make them brighter.
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Brighter clouds reflect
more sunlight back to space,
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cooling the climate.
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So in fact,
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humans are currently running
two unintentional experiments
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on our climate.
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In the first one, we're increasing
the concentration of greenhouse gases
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and gradually warming the earth system.
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This works something like a fever
in the human body.
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If the fever remains low,
its effects are mild,
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but as the fever rises,
damage grows more severe
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and eventually devastating.
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We're seeing a little of this now.
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In our other experiment,
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we're planning to remove
a layer of particles
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that brighten clouds and shield us
from some of this warming.
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The effect is strongest
in ocean clouds like these,
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and scientists expect the reduction
of sulfur emissions from ships next year
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to produce a measurable increase
in global warming.
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Bit of a shocker?
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In fact, most emissions contain sulfates
that brighten clouds:
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coal, diesel exhaust, forest fires.
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Scientists estimate that the total
cooling effect from emission particles,
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which they call aerosols
when they're in the climate,
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may be as much as all of the warming
we've experienced up until now.
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There's a lot of uncertainty
around this effect,
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and it's one of the major reasons
why we have difficulty predicting climate,
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but this is cooling that we'll lose
as emissions fall.
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So to be clear, humans
are currently cooling the planet
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by dispersing particles
into the atmosphere at massive scale.
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We just don't know how much,
and we're doing it accidentally.
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That's worrying,
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but it could mean that we have
a fast-acting way to reduce warming,
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emergency medicine
for our climate fever if we needed it,
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and it's a medicine
with origins in nature.
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This is a NASA simulation
of earth's atmosphere,
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showing clouds and particles
moving over the planet.
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The brightness is the Sun's light
reflecting from particles in clouds,
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and this reflective shield
is one of the primary ways
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that nature keeps the planet
cool enough for humans
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and all of the life that we know.
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In 2015, scientists assessed possibilities
for rapidly cooling climate.
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They discounted
things like mirrors in space,
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ping-pong balls in the ocean,
plastic sheets on the Arctic,
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and they found
that the most viable approaches
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involved slightly increasing
this atmospheric reflectivity.
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In fact, it's possible that reflecting
just one or two percent more sunlight
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from the atmosphere
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could offset two degrees Celsius
or more of warming.
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Now, I'm a technology executive,
not a scientist.
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About a decade ago,
concerned about climate,
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I started to talk with scientists about
potential countermeasures to warming.
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These conversations grew
into collaborations
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that became the Marine
Cloud Brightening Project,
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which I'll talk about momentarily,
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and the nonprofit policy organization
SilverLining, where I am today.
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I work with politicians, researchers,
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members of the tech industry and others
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to talk about some of these ideas.
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Early on, I met British
atmospheric scientist John Latham,
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who proposed cooling the climate
the way that the ships do,
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but with a natural source of particles:
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sea-salt mist from seawater
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sprayed from ships into areas
of susceptible clouds over the ocean.
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The approach became known
by the name I gave it then,
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"marine cloud brightening."
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Early modeling studies suggested
that by deploying marine cloud brightening
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in just 10 to 20 percent
of susceptible ocean clouds,
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it might be possible to offset
as much as two degrees Celsius's warming.
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It might even be possible
to brighten clouds in local regions
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to reduce the impacts caused
by warming ocean surface temperatures.
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For example, regions
such as the Gulf Atlantic
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might be cooled in the months
before a hurricane season
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to reduce the force of storms.
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Or, it might be possible to cool waters
flowing onto coral reefs
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overwhelmed by heat stress,
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like Australia's Great Barrier Reef.
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But these ideas are only theoretical,
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and brightening marine clouds
is not the only way
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to increase the reflection
of the sunlight from the atmosphere.
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Another occurs when large volcanoes
release material with enough force
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to reach the upper layer
of the atmosphere, the stratosphere.
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When Mount Pinatubo erupted in 1991,
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it released material
into the stratosphere,
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including sulfates that mix
with the atmosphere to reflect sunlight.
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This material remained
and circulated around the planet.
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It was enough to cool the climate
by over half a degree Celsius
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for about two years.
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This cooling led to a striking increase
in Arctic ice cover in 1992,
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which dropped in subsequent years
as the particles fell back to earth.
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But the volcanic phenomenon
led Nobel Prize winner Paul Crutzen
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to propose the idea that dispersing
particles into the stratosphere
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in a controlled way might be
a way to counter global warming.
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Now, this has risks
that we don't understand,
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including things like
heating up the stratosphere
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or damage to the ozone layer.
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Scientists think that there could be
safe approaches to this,
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but is this really where we are?
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Is this really worth considering?
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This is a simulation
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from the US National Center
for Atmospheric Research
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global climate model showing,
earth surface temperatures through 2100.
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The globe on the left visualizes
our current trajectory,
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and on the right, a world where particles
are introduced into the stratosphere
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gradually in 2020,
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and maintained through 2100.
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Intervention keeps surface temperatures
near those of today,
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while without it, temperatures rise
well over three degrees.
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This could be the difference
between a safe and an unsafe world.
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So, if there's even a chance
that this could be close to reality,
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is this something
we should consider seriously?
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Today, there are no capabilities,
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and scientific knowledge
is extremely limited.
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We don't know whether these types
of interventions are even feasible,
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or how to characterize their risks.
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Researchers hope to explore
some basic questions
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that might help us know
whether or not these might be real options
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or whether we should rule them out.
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It requires multiple ways
of studying the climate system,
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including computer models
to forecast changes,
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analytic techniques like machine learning,
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and many types of observations.
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And though it's controversial,
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it's also critical that researchers
develop core technologies
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and perform small-scale,
real-world experiments.
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There are two research programs
proposing experiments like this.
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At Harvard, the SCoPEx experiment
would release very small amounts
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of sulfates, calcium carbonate and water
into the stratosphere with a balloon,
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to study chemistry and physics effects.
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How much material?
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Less than the amount released
in one minute of flight
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from a commercial aircraft.
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So this is definitely not dangerous,
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and it may not even be scary.
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At the University of Washington,
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scientists hope to spray
a fine mist of salt water into clouds
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in a series of land and ocean tests.
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If those are successful,
this would culminate in experiments
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to measurably brighten
an area of clouds over the ocean.
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The marine cloud brightening effort
is the first to develop any technology
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for generating aerosols for atmospheric
sunlight reflection in this way.
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It requires producing
very tiny particles --
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think about the mist that comes
out of an asthma inhaler --
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at massive scale -- so think
of looking up at a cloud.
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It's a tricky engineering problem.
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So this one nozzle they developed
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generates three trillion
particles per second,
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80 nanometers in size,
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from very corrosive saltwater.
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It was developed by a team
of retired engineers in Silicon Valley --
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here they are --
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working full-time for six years,
without pay, for their grandchildren.
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It will take a few million dollars
and another year or two
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to develop the full spray system
they need to do these experiments.
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In other parts of the world,
research efforts are emerging,
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including small modeling programs
at Beijing Normal University in China,
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the Indian Institute of Science,
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a proposed center for climate repair
at Cambridge University in the UK
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and the DECIMALS Fund,
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which sponsors researchers
in global South countries
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to study the potential impacts
of these sunlight interventions
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in their part of the world.
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But all of these programs,
including the experimental ones,
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lack significant funding.
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And understanding
these interventions is a hard problem.
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The earth is a vast, complex system
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and we need major investments
in climate models, observations
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and basic science
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to be able to predict climate
much better than we can today
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and manage both our accidental
and any intentional interventions.
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And it could be urgent.
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Recent scientific reports
predict that in the next few decades,
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earth's fever is on a path to devastation:
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extreme heat and fires,
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major loss of ocean life,
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collapse of Arctic ice,
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displacement and suffering
for hundreds of millions of people.
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The fever could even reach tipping points
where warming takes over
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and human efforts are no longer enough
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to counter accelerating changes
in natural systems.
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To prevent this circumstance,
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the UN's International Panel
on Climate Change predicts
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that we need to stop
and even reverse emissions by 2050.
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How? We have to quickly and radically
transform major economic sectors,
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including energy, construction,
agriculture, transportation and others.
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And it is imperative that we do this
as fast as we can.
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But our fever is now so high
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that climate experts say
we also have to remove
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massive quantities of CO2
from the atmosphere,
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possibly 10 times
all of the world's annual emissions,
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in ways that aren't proven yet.
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Right now, we have slow-moving solutions
to a fast-moving problem.
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Even with the most optimistic assumptions,
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our exposure to risk
in the next 10 to 30 years
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is unacceptably high, in my opinion.
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Could interventions like these
provide fast-acting medicine if we need it
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to reduce the earth's fever
while we address its underlying causes?
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There are real concerns about this idea.
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Some people are very worried
that even researching these interventions
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could provide an excuse to delay efforts
to reduce emissions.
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This is also known as a moral hazard.
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But, like most medicines,
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interventions are more dangerous
the more that you do,
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so research actually
tends to draw out the fact
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that we absolutely,
positively cannot continue
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to fill up the atmosphere
with greenhouse gases,
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that these kinds of alternatives are risky
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and if we were to use them,
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we would need to use
as little as possible.
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But even so,
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could we ever learn enough
about these interventions
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to manage the risk?
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Who would make decisions
about when and how to intervene?
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What if some people are worse off,
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or they just think they are?
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These are really hard problems.
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But what really worries me
is that as climate impacts worsen,
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leaders will be called on to respond
by any means available.
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I for one don't want them to act
without real information
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and much better options.
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Scientists think it will take
a decade of research
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just to assess these interventions,
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before we ever were
to develop or use them.
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Yet today, the global level of investment
in these interventions
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is effectively zero.
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So, we need to move quickly
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if we want policymakers
to have real information
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on this kind of emergency medicine.
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There is hope!
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The world has solved
these kinds of problems before.
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In the 1970s, we identified
an existential threat
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to our protective ozone layer.
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In the 1980s, scientists,
politicians and industry
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came together in a solution to replace
the chemicals causing the problem.
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They achieved this with the only
legally binding environmental agreement
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signed by all countries in the world,
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the Montreal Protocol.
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Still in force today,
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it has resulted in a recovery
of the ozone layer
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and is the most successful
environmental protection effort
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in human history.
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We have a far greater threat now,
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but we do have the ability
to develop and agree on solutions
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to protect people
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and restore our climate to health.
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This could mean that to remain safe,
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we reflect sunlight for a few decades,
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while we green our industries
and remove CO2.
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It definitely means we must work now
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to understand our options
for this kind of emergency medicine.
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Thank you,
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(Applause)