Yogi Berra, a US baseball player
and philosopher, said,

"If we don't know where we're going,
we might not get there."

Accumulating scientific knowledge
is giving us greater insights,

greater clarity into what our future
might look like in a changing climate

and what that could mean for our health.

I'm here to talk about a related aspect

on how our emissions of greenhouse gases
from burning of fossil fuels

is reducing the nutritional
quality of our food.

We'll start with the food pyramid.

You all know the food pyramid.

We all need to eat a balanced diet.

We need to get proteins.

We need to get micronutrients.
We need to get vitamins.

And so this is way for us
to think about how to make sure

we get what we need every day

so we can grow and thrive.

So we eat not just because we need to,

we also eat for enjoyment.

Bread, pasta, pizza,

there's a whole range of foods

that are culturally important.

We enjoy eating these.

And so they're important for our diet,

but they're also important
for our cultures.

Carbon dioxide has been increasing since
the start of the Industrial Revolution,

increasing from about
280 parts per million to over 410 today,

and it continues to increase.

The carbon that plants need to grow
comes from this carbon dioxide.

They bring it into the plant,
they break it apart

into the carbon itself,

and they use that to grow.

They also need nutrients from the soil.

And so yes, carbon dioxide is plant food.

And this should be good news,
of rising carbon dioxide concentrations,

for food security around the world,

making sure that people
get enough to eat every day.

About 820 million people in the world
don't get enough to eat every day.

So there's a fair amount written
about how higher CO2

is going to help with
our food security problem.

We need to accelerate our progress
in agricultural productivity,

to feed the nine to 10 billion people
who will be alive in 2050

and to achieve the Sustainable
Development Goals,

particularly the Goal Number 2,

that is on reducing food insecurity,

increasing nutrition,

increasing access to the foods
that we need for everyone.

We know that climate change
is affecting agricultural productivity.

The Earth has warmed
about one degree Centigrade

since pre-industrial times.

That is changing local temperature
and precipitation patterns,

and that has consequences
for the agricultural productivity

in many parts of the world.

And it's not just local changes
in temperature and precipitation,

it's the extremes,

Extremes in terms of heat waves,
floods and droughts

are significantly affecting productivity.