Cities are driving climate change. Here's how they can fix it

Cities pump out 70 percent of all global carbon emissions -- which means they also have the greatest opportunity to lower CO2 levels and energy consumption. Climate and data scientist Angel Hsu shares how cities around the world are leading the response to climate change by innovating new, low-carbon ways of living.

What would the world look like
if extreme climate change becomes reality?

Well, here's just one example.

If temperatures were to rise
by three more degrees Celsius,

Shanghai, a city
of 24 million people in China,

will be wiped off the map.

And it's not just the only coastal city

that's at risk of disappearing
beneath rising sea levels.

Globally, 2019 was the second
hottest year on record.

Cities all throughout the world

experienced record-setting
summer temperatures.

In June 2019, temperatures
in Churu, India,

exceeded 120 degrees Fahrenheit,

to the point that
the government warned citizens

to avoid drinking coffee, tea and alcohol
out of fear of overheating.

Heat waves are becoming more severe
and commonplace due to climate change,

projected to lead to deaths at the same
rate as all infectious diseases combined.

This map here

shows the increase in the severity
and prevalence of heat waves

if the world follows
a moderate warming scenario.

By 2050, summertime highs
of 95 degrees Fahrenheit,

or 35 degrees Celsius,

will become the new normal
in nearly 1,000 cities,

triple the number of cities that currently
experience these sweltering temperatures.

But the irony is that cities
are not just affected by climate change,

they're also causing it.

Cities consume between 60 and 80 percent
of global energy resources

and account for approximately 70 percent
of global carbon dioxide emissions.

As we can see here in this map,

the light blue and the yellow areas

correspond to those
with the highest fossil fuel-based

carbon dioxide emissions

and also correspond
to major urban centers.

Aside from cities' energy consumption,

growing urban areas
convert the planet's green surfaces

to buildings and pavement,

and these can absorb
more of the sun's energy

than the natural grasslands and forests
that they've replaced,

making urban areas hotter
than their surrounding environments.

This phenomenon is called
the "urban heat island effect."

Here in Singapore, downtown neighborhoods
can be as much as seven degrees Celsius,

or 13 degrees Fahrenheit,

hotter than the rainforests
that were once here.

While it's true that cities
are contributing to climate change,

they're also key actors in forging
low carbon emission pathways.

In dense cities like New York City
and Tokyo, for instance,

the average resident

is responsible for over two tons
of carbon dioxide emissions per capita.

This is less than a single
passenger car emits

in a single year in the United States.

Cities around the world are stepping up
to tackle climate change,

with ambitious policies

that often exceed the requirements
of national governments.

Take Copenhagen, for example.

It's committed to become
carbon neutral by 2025,

and Glasgow in Scotland also plans
to become carbon neutral by 2030.

Today, there are more than 10,000 cities
all around the world

that are committing
to their own ambitious climate actions,

plans that include
emissions reduction targets,

clean energy and sustainable
transit projects,

and also energy efficiency policies

that can save people and cities
money, energy and emissions.

Recent analysis shows
that just 6,000 cities,

combined with regions and companies,

are undertaking climate initiatives
that can reduce global emissions

by up to two gigatons
of carbon dioxide equivalent in 2030.

That's roughly four percent
of the world's total annual emissions

on top of what national
governments have pledged.

And this is just the start.

Imagine what could happen
if 20,000 cities were to band together

to curb climate change.

While this potential for cities' climate
action sounds really promising,

cities must work to make sure

that these policies
are implemented fairly and equitably.

Where you live in a city,
your income, your race --

research is showing

that these factors can determine
your access to environmental benefits

like green space and sustainable transit,

and they can also determine
your share of environmental burdens

like air pollution and climate change.

We observe these
neighborhood-level disparities

particularly clearly in these
side-by-side images of Los Angeles,

comparing income on the left
and tree cover on the right.

The darkest green neighborhood
has an average annual income

of over 100,000 US dollars per person.

And over 70 percent of it has tree cover.

The blue neighborhoods
towards the bottom of the map

only have a third of the income per person

and less than five percent tree cover.

Seventy percent versus five.

This disparity has real consequences.

Green spaces are often public spaces,

and they're known to be associated
with social and economic well-being.

They can also reduce crime
and foster social cohesion.

Trees also can help
to filter harmful air pollution

and provide evaporative cooling and shade

and relief for some
of these high temperatures.

So not only are those poorer neighborhoods

at a greater disadvantage
from access to green space,

but they're also more vulnerable
to air pollution and climate change.

We can observe particularly
pronounced disparities

in urban heat according to race.

Our latest research shows that 97 percent
of major urban areas in the United States

are exposing Black populations
and people of color

to a full degree Celsius
higher of urban heat

than their white counterparts.

Take a look at this map of my hometown
of Greenville, South Carolina.

Unlike the name suggests
it is not green for everyone.

The hottest areas of the county
shown on the map in red

correspond with the highest percentages
of Black and poor populations.

And we're seeing similar patterns
throughout cities

all across the United States.

To address these inequalities,

cities are starting
to strategize and develop plans

that can ensure that climate benefits

are provided to all
of their citizens equally.

Take Bogotá, the capital city
of Colombia, for example.

It has one of the most
extensive bike networks

in all of Latin America,

connecting people to jobs,
education centers

and recreational opportunities.

A new bike highway project can allow
for around 42,000 daily bicycle trips

and potentially avoid 270,000 tons
of greenhouse gas emissions.

In Africa, where many cities
lack universal access to electricity,

mini-grids are providing
approximately 73 million households

with clean electricity.

So as we can see from these examples,

tackling climate change
has to start in cities.

Many cities are starting
to flip the script on climate change,

proving to be part of the solution
and not just the problem,

and bringing the kind
of innovative solutions that we need

for a more just and sustainable world.

Thank you.