And that might seem a bit surprising because

my full-time work at the foundation is mostly about vaccines and seeds,

about the things that we need to invent and deliver

to help the poorest two billion live better lives.

But energy and climate are extremely important to these people,

in fact, more important than to anyone else on the planet.

The climate getting worse, means that many years their crops won't grow.

There will be too much rain, not enough rain.

Things will change in ways

that their fragile environment simply can't support.

And that leads to starvation. It leads to uncertainty. It leads to unrest.

So, the climate changes will be terrible for them.

Also, the price of energy is very important to them.

In fact, if you could pick just one thing to lower the price of,

to reduce poverty, by far, you would pick energy.

Now, the price of energy has come down over time.

Really, advanced civilization is based on advances in energy.

The coal revolution fueled the industrial revolution,

and, even in the 1900's we've seen a very rapid decline in the price of electricity,

and that's why we have refrigerators, air-conditioning,

we can make modern materials and do so many things.

And so, we're in a wonderful situation with electricity in the rich world.

But, as we make it cheaper -- and let's go for making it twice as cheap --

we need to meet a new constraint,

and that constraint has to do with CO2.

CO2 is warming the planet,

and the equation on CO2 is actually a very straightforward one.

If you sum up the CO2 that gets emitted,

that leads to a temperature increase,

and that temperature increase leads to some very negative effects.

The effects on the weather and, perhaps worse, the indirect effects,

in that the natural ecosystems can't adjust to these rapid changes,

and so you get ecosystem collapses.

Now, the exact amount of how you map

from a certain increase of CO2 to what temperature will be

and where the positive feedbacks are,

there's some uncertainty there, but not very much.

And there's certainly uncertainty about how bad those effects will be,

but they will be extremely bad.

I asked the top scientists on this several times,

do we really have to get down to near zero?

Can't we just cut it in half or a quarter?

And the answer is that, until we get near to zero,

the temperature will continue to rise.

And so that's a big challenge.

It's very different than saying we're a 12 ft high truck trying to get under a 10 ft bridge,

and we can just sort of squeeze under.

This is something that has to get to zero.

Now, we put out a lot of carbon dioxide every year,

over 26 billion tons.

For each American, it's about 20 tons.

For people in poor countries, it's less than one ton.

It's an average of about five tons for everyone on the planet.

And, somehow, we have to make changes

that will bring that down to zero.

It's been constantly going up.

It's only various economic changes that have even flattened it at all,

so we have to go from rapidly rising

to falling, and falling all the way to zero.

This equation has four factors.

A little bit of multiplication.

So, you've got a thing on the left, CO2, that you want to get to zero,

and that's going to be based on the number of people,

the services each person's using on average,

the energy on average for each service,

and the CO2 being put out per unit of energy.

So, let's look at each one of these

and see how we can get this down to zero.

Probably, one of these numbers is going to have to get pretty near to zero.

Now that's back from high school algebra,

but let's take a look.

First we've got population.

Now, the world today has 6.8 billion people.

That's headed up to about nine billion.

Now, if we do a really great job on new vaccines,

health care, reproductive health services,

we could lower that by, perhaps, 10 or 15 percent,

but there we see an increase of about 1.3.

The second factor is the services we use.

This encompasses everything,

the food we eat, clothing, TV, heating.

These are very good things,

and getting rid of poverty means providing these services

to almost everyone on the planet.

And it's a great thing for this number to go up.

In the rich world, perhaps the top one billion,

we probably could cut back and use less,

but every year, this number, on average, is going to go up,

and so, over all, that will more than double

the services delivered per person.

Here we have a very basic service.

Do you have lighting in your house to be able to read your homework,

and, in fact, these kids don't, so they're going out

and reading their school work under the street lamps.

Now, efficiency, E, the energy for each service,

here, finally we have some good news.

We have something that's not going up.

Through various inventions and new ways of doing lighting,

through different types of cars, different ways of building buildings.

there are a lot of services where you can bring

the energy for that service down quite substantially,

some individual services even, bring it down by 90 percent.

There are other services like how we make fertilizer,

or how we do air transport,

where the rooms for improvement are far, far less.

And so, overall here, if we're optimistic,

we may get a reduction of a factor of three to even, perhaps, a factor of six.

But for these first three factors now,

we've gone from 26 billion to, at best, maybe 13 billion tons,

and that just won't cut it.

So let's look at this fourth factor --

this is going to be a key one --

and this is the amount of CO2 put out per each unit of energy.

And so the question is, can you actually get that to zero?

If you burn coal, no.

If you burn natural gas, no.

Almost every way we make electricity today,

except for the emerging renewables and nuclear, puts out CO2.

And so, what we're going to have to do at a global scale,

is create a new system.

And so, we need energy miracles.

Now, when I use the term miracle, I don't mean something that's impossible.

The microprocessor is a miracle. The personal computer is a miracle.

The internet and its services are a miracle.

So, the people here have participated in the creation of many miracles.

Usually, we don't have a deadline,

where you have to get the miracle by a certain date.

Usually, you just kind of stand by, and some come along, some don't.

This is a case where we actually have to drive full speed

and get a miracle in a pretty tight time line.

Now, I thought, how could I really capture this?

Is there some kind of natural illustration,

some demonstration that would grab people's imagination here?

I thought back to a year ago when I brought mosquitos,

and somehow people enjoyed that.

(Laughter)

It really got them involved in the idea of,

you know, there are people who live with mosquitos.

So, with energy, all I could come up with is this.

I decided that releasing fireflies

would be my contribution to the environment here this year.

So here we have some natural fireflies.

I'm told they don't bite, in fact, they might not even leave that jar.

(Laughter)

Now, there's all sorts gimmicky solutions like that one,

but they don't really add up to much.

We need solutions, either one or several,

that have unbelievable scale

and unbelievable reliability,

and, although there's many directions people are seeking,

I really only see five that can achieve the big numbers.

I've left out tide, geothermal, fusion, biofuels.

Those may make some contribution,

and if they can do better than I expect, so much the better,

but my key point here

is that we're going to have to work on each of these five,

and we can't give up any of them because they look daunting,

because they all have significant challenges.

Let's look first at the burning fossil fuels,

either burning coal or burning natural gas.

What you need to do there, seems like it might be simple, but it's not,

and that's to take all the CO2, after you've burned it, going out the flue,

pressurize it, create a liquid, put it somewhere,

and hope it stays there.

Now we have some pilot things that do this at the 60 to 80 percent level,

but getting up to that full percentage, that will be very tricky,

and agreeing on where these CO2 quantities should be put will be hard,

but the toughest one here is this long term issue.

Who's going to be sure?

Who's going to guarantee something that is literally billions of times larger