Hello and welcome to more or less on the BBC World Service.

We're your weekly guide to the numbers all around us in the news and in life, and I'm Tim Halford.

While lockdown was in place in many parts of the world, everything seemed pretty quiet.

There were fewer cars on the road, fewer planes flying overhead, workplaces and factories were closed.

How much impact did that have on the climate?

Dr Zeke Housefather is the directs who have climate and energy at the Breakthrough Institute.

Carbon dioxide emissions have fallen as GDP has gone down, as industrial activities have ceased, as people aren't driving anymore.

How much it will go down for the full year of 2020 really depends on what happens with the virus.

We're already seeing Chinese emissions going back up to close to where there were before the pandemic, as industrial activity increases there.

Well, let's start with China then.

Do we have any sense of how sharp and how much the fallen emissions was during the shutdown in China?

So we don't have precise numbers for emissions.

We just have these other indicators that are related to emissions like coal use, like GDP.

What we do know is that Chinese GDP fell by about 10% in the first quarter of 2020, which is a huge number,

especially when you consider that for much of the first month, January, China wasn't shut down.

So the drop in February, March, was even larger than that.

We presume a similar fall in CO2 use or CO2 emissions.

So we actually saw a larger drop in coal use, which is our main proxy for CO2.

There's about a 20% drop for a large period of February and the first half of March.

So overall for Q1, we're probably looking at somewhere around 10 to 20% drop in CO2 when all things are considered.

OK, so a substantial blip, but a blip nonetheless.

What about air travel?

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