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I'm here to talk about climate change,
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but I am not really and environmentalist.
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In fact, I've never really
thought of myself as a nature person.
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I have never gone camping,
never gone hiking,
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never even owned a pet.
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I've lived my whole life in cities,
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actually just one city.
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And while I like to take trips
to visit nature,
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I always thought it was something
that was happening elsewhere,
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far away,
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with all of modern life
a fortress against its forces.
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In other words,
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like just about everybody I knew,
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I lived my life complacent
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and deluded
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about the threat from global warming.
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Which I took to be happening slowly,
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happening at a distance,
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and representing only a modest threat
to the way that I lived.
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In each of these ways
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I was very, very wrong.
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Now most people, if they were telling you
about climate change,
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will tell you a story about the future.
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If I was doing that, I would say,
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according to the UN,
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if we don't change course
by the end of the century,
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we're likely to get about four
degrees Celsius of warming.
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That would mean, some scientists believe,
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twice as much war,
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half as much food,
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a global GDP possibly 20 percent smaller
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than it would be without climate change.
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That's an impact that's deeper
than the great depression,
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and it would be permanent.
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But the impacts are actually happening
a lot faster than 2100.
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By just 2050, it's estimated,
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many of the biggest cities
in South Asia and the Middle East
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will be almost literally
unlivably hot in summer.
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These are cities that today
are home to 10, 12,
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15 million people.
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And in just three decades
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you wouldn't be able
to walk around outside in them
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without risking heat stroke
or possibly death.
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The planet is now
1.1 degrees Celsius warmer
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than it was before industrialization.
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That may not sound like a lot,
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but it actually puts us entirely
outside the window of temperatures
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that enclose all of human history.
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That means that everything
we have ever known as a species,
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the evolution of the human animal,
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the development of agriculture,
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the development
of rudimentary civilization
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and modern civilization
and industrial civilization.
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Everything we know about ourselves
as biological creatures,
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as social creatures,
as political creatures,
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all of it is the result
of climate conditions
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we have already left behind.
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It's like we've landed
on an entirely different planet,
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with an entirely different climate.
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And we now have to figure out
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what of the civilization
that we've brought with us
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can endure these new conditions,
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and what can't.
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And things will get worse from here.
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Now for a very long time,
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we were told that climate change
was a slow saga.
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It started with the industrial revolution,
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and it had fallen to us
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to clean up the mess
left by our grandparents
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so our grandchildren
wouldn't be dealing with the results.
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It was a story of centuries.
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In fact, half of all of the emissions
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that have ever been produced
from the burning of fossil fuels
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in the entire history of humanity,
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have been produced
in just the last 30 years.
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That's since Al Gore published
his first book on warming.
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It's since the UN established
its IPCC climate change body.
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We've done more damage since then
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than in all the centuries,
all the millennia before.
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Now I'm 37 years old,
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which means my life contains
this entire story.
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When I was born,
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the planet's climate seemed stable.
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Today,
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we are on the brink of catastrophe.
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The climate crisis is not the legacy
of our ancestors.
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It is the work of a single generation.
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Ours.
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This may all sound like bad news.
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Which it is, really bad news.
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But it also contains, I think,
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some good news,
at least relatively speaking.
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These impacts are terrifyingly large.
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But they are also, I think, exhilarating.
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Because they are ultimately a reflection
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of how much power we have
over the climate.
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If we get to those hellish scenarios,
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it will be because
we have made them happen,
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because we have chosen
to make them happen.
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Which means we can choose
to make other scenarios happen too.
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Now that may seem too rosy to believe
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and the political obstacles
are in fact, enormous.
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But it is a simple fact,
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the main driver of global warming
is human action:
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How much carbon we put
into the atmosphere.
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Our hands are on those levers.
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And we can write the story
of the planet's climate future ourselves.
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Not just can, but are.
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Since inaction is a kind of action,
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we'll be writing that story ourselves
whether we like it or not.
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This is not just any story,
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all of us holding the future
of the planet in our hands.
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It's the kind of story
we used to recognize only in mythology
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and theology.
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A single generation
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that has brought the future
of humanity into doubt
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now tasked with securing a new future.
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So what would that look like?
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It could mean solar arrays
barnacling the planet
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really everywhere you looked.
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It could mean
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if we developed batter technology,
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we wouldn't even need
to deploy them that broadly,
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because it's been estimated
that just a sliver of the Sahara desert
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absorbs enough solar power
to provide all the world's energy needs.
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But we'd probably need
a new electric grid.
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One that doesn't lose
two thirds of its power to waste heat,
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as is today the case in the US.
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We could use some more
nuclear power, perhaps,
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although it would have to be an entirely
different kind of nuclear power
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because today's technology
simply isn't cost-competitive
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with renewable energy
whose costs are falling so rapidly.
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We'd need a new kind of plane,
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because I don't think
it's particularly practical
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to ask the entire world
to give up on air travel,
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especially as so much of the global South
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is for the very first time
able to afford it.
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We need planes that won't produce carbon.
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We need a new kind of agriculture.
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Because we probably can't ask people
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to entirely give up one meat and go vegan.
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It would mean a new way of raising beef.
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Or perhaps an old way,
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since we already know
that traditional pasturing practices
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can turn cattle farms
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from what are called carbon sources,
which produce CO2,
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into carbon sinks, which absorb them.
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If you prefer a techno solution,
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maybe we can grow
some of that mean in the lab.
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Probably we could also feed
some real cattle seaweed
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because that cuts their methane emissions
by as much as 95 or 99 percent.
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Probably we'd have to do
all of these things
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because as with every aspect
of this puzzle,
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the problem is simply
too vast and complicated
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to solve in any single silver-bullet way.
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And no matter how many
solutions we deploy,
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we probably won't be able
to decarbonize in time.
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That's the terrifying math that we face.
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We won't be able to beat climate change.
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Only live with it and limit it.
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And that means we'd probably need
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some amount of what are called
negative emissions,
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which take carbon
out of the atmosphere as well.
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Billions of new trees,
maybe trillions of new trees.
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And whole plantations
of carbon-capture machines.
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Perhaps an industry
twice or four times the size
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of today's oil and gas business,
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to undo the damage that was done
by those businesses in past decades.
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We would need a new kind
of infrastructure,
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poured by a different kind of cement,
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because today, if cement were a country,
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it would be the world's
third biggest emitter.
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And China is pouring as much cement
every three years
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as the US poured
in the entire 20th century.
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We would need to build
sea walls an levies,
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to protect those people
living on the coast,
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many of whom are too poor
to build them today,
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which is why it must mean an end
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to a narrowly nationalistic geopolitics
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that allows us to define the suffering
of those living elsewhere in the world
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as insignificant,
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when we even acknowledge it.
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This better future won't be easy.
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But the only obstacles are human ones.
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That may not be much of a comfort,
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if you know what I know
about human brutality and indifference,
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but I promise you,
it is better than the alternative.
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Science isn't stopping us
from taking action,
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and neither is technology.
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We have the tools we need today to begin.
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Of course, we also have the tools we need
to end global poverty,
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epidemic disease,
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and the abuse of women as well.
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Which is why more than new tools,
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we need a new politics,
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a way of overcoming
all those human obstacles,
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our culture, our economics,
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out status quo bias,
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our disinterest in taking seriously
anything that really scares us.
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Our shortsightedness.
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Our sense of self-interest.
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And the selfishness of the world's
rich and powerful
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who have the least incentive
to change anything.
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Now they will suffer too.
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But not as much as those with the least,
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who have the least to produce warming,
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and have benefited the least
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from the processes that have brought us
to this crisis point,
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but will be burdened most
in the decades ahead.
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A new politics
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would make the matter
of managing that burden,
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where it falls and how heavily,
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the top priority of our time.
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No matter what we do
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climate change will transform modern life.
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Some amount of warming
is already baked in and is inevitable.
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Which means probably some amount
of additional suffering is too.
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And even if we take dramatic action
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and avoid some of these
truly terrifying worst-case scenarios,
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it would mean living on an entirely
different planet.
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With a new politics, a new economics,
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a new relationship to technology,
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and a new relationship to nature,
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a whole new world.
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But a relatively livable one.
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Relatively prosperous.
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And green.
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Why not choose that one?
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Thank you.
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(Applause)