How do volcanoes and farts impact climate change?

Thanks to UCL's Mark Maslin for the answers!

Will - We've got a double feature this time round, both concerning certain emissions effects on climate change. We'll get to the unusual one in a moment. But the first question was sent in by listener Ranjith who asked, I've been seeing some claims that volcanoes produce a huge amount of CO2 in relation to humans. Could you clarify the situation? So we have tapped up the expertise of UCL's Mark Maslin.

Mark - So scientists have been measuring the amount of CO2 and other gases coming out of volcanoes for decades, and it looks like both land and submarine volcanoes, because of course there are volcanoes under the ocean. They emit about 0.13 gigatons to about 0.4 gigatons per year. Now that sounds like a huge amount, but if we compare it with all human carbon dioxide emissions, that's about 41 billion tons or gigatons of carbon. So humans emit about a hundred to 400 times the amount of CO2 coming from volcanoes.

Will - It feels like we've put the debate then to bed between humans and volcanoes. But correct me if I'm wrong, volcanoes also spit out a few things that stop as much of the sunlight hitting the earth as well.

Mark - We also know that volcanoes can have a negative effect on warming. So Pinatubo that erupted in 1991 spewed a lot of aerosols, mainly sulphur dioxide into the atmosphere, and that for one year reflected a little bit of sunlight and cooled the planet down just for a 12 month period. However, as scientists, we know that in the 1980s and the early 1990s, the amount of sulphur dioxide getting into the atmosphere because of industry, those aerosols were causing a little bit of cooling. So for us, the actual global warming was being masked by our pollution. Now, of course, we've cleaned up that air pollution because it's so bad for human health. And of course what we see is the underlying trend of global warming getting faster since then.

Will - And to finish this off, I must ask you the rather indelicate question coming in from listener Ben, who has asked about how much greenhouse gas does human flatulence emit.

Mark - Human farts are negligible in terms of the amount of methane the world produces. What we should be worried about is our cattle, which produce methane from both ends. And I'll give you a really big stat. We take the weight of land mammals on the planet. 30% are humans, but 67% of that weight is our livestock and our pets. That's a huge number. So only 3% of the mammals on the land surface are actually wild animals that David Attenborough goes and films for our enjoyment on a Sunday night on the sofa. So there are huge numbers of cattle producing huge amounts of methane. But add into that when we are actually producing huge amounts of wet rice from around the world, that produces lots of methane as well. So compared with this, our minuscule little farts are just irrelevant compared with the farts and burps of cattle, the actual amount of methane produced by our artificial wetlands, which are producing rice to feed the world.

Will - So don't think so much about volcanoes or your farts. Think about your diet. Thank you so much to Ranjith and Ben for their questions. And Mark Maslin for the answers. Next week we're answering this question sent in by listener, David.

David - I suffer from post viral chronic pain and fatigue and often joke that I need a body transplant. Is it possible to keep a head alive and fully functioning? I'd love to know the answer, but not really keen on being the first one to go our transplant

Will - And if you think you know the answer or have a question of your own, do send it in. The email address is 5livescience@bbc.co.uk.