Hello and welcome to the Intelligence on Economist Radio. I'm your host, Jason Palmer.

Every weekday, we provide a fresh perspective on the events shaping your world.

The red line on Chicago's metro system traverses a demographic as well as a geographic distance.

The journey from one stop to another might represent a sharp drop in life expectancy.

Our correspondent rides the rails to learn more about the city's inequality.

And you can't go anywhere in Turkey without being offered a glass, not a cup, of tea.

Now there's a government-sponsored push to go organic, and it's not clear whether Turkish tea drinkers are willing to pay up.

But first, in these early days of the new year, we take a step away from the news to look at a necessary front in the fight against climate change.

The science of what needs to be done to tackle climate change is well known.

Lower the amount of gases such as carbon dioxide in the environment that are warming the planet.

But the practice of it has proven to be a thornier problem.

As so many times before, at the UN's annual climate meeting last month in Madrid,

governments struggled to find solutions that were seen as equitable for all countries.

We can't accept paragraph 30 and would insist on its deletion.

While the headlines remain on reducing emissions, that almost certainly won't be enough

to keep the world from some of the worst effects of climate change.

So if merely reducing the slope of the emissions curve won't suffice,

engineers are going to have to

figure out how to reverse it.

Negative carbon dioxide emissions means rather than putting CO2 or another greenhouse gas

into the atmosphere, you remove it from the atmosphere.

Katrina Bragg is the economist's environment editor.

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