Volcanoes didn't do-in the dinosaurs

Over the past 40 years, the exact cause of the death of the dinosaurs has been hotly debated. Some favour the theory that a massive meteor hit the Earth and changed the climate, while others argue that a sequence of huge volcanic eruptions also contributed to the mass extinction. Research this week from Leeds University has poured cold water on the latter theory, suggesting that the impacts of these volcanoes would have been relatively small. Georgia Mills spoke to lead researcher Anja Schmidt to find out how they investigated a mystery 60 million years old...

Anja - I'm running climate models and, what I did is, I gathered all the information we have about this volcanism that happened 65-66 million years ago. So we needed to know, how long were these eruptions, how much volcanic gases were emitted and then once we had all this information, we put that in a very sophisticated computer model, and then we could simulate what these omissions would do to the environment, but also to climate.

Georgia - And what did you find out when you ran these simulations?

Anja - Some researchers, previously, actually suggested that, because of these volcanic eruptions, temperatures on earth would drop really drastically and they call this a so called "volcanic winter".  Just imagine, really, really cold surface temperatures.  But what we find actually when running this climate model with all the information we gathered, we find that temperatures didn't drop that drastically.  So the situation wasn't as grim as previously suggested by some scientists.  So with our work, we actually find that because there is a drop in temperature, but it would probably be okay for most animals and plants, so they would have been able to cope with these temperature changes.

Georgia - Why would a volcano erupting cause a drop in temperature in the first place?

Anja - So, volcanos emit a lot of gases, and one of the most prominent gases is sulphur dioxide and, once sulphur dioxide is in the atmosphere, it actually gets chemically converted to form very, very small particles - you can't see them with your bare eye.  But these particles, they basically  reduce the amount of energy that comes down to the surface from the Sun.  So less energy reaches the surface and, therefore, you end up with the cooling of the Earth's surface. We're really sure that depending on how long this eruption lasted.  So if they lasted, for example, a decade we find that the surface temperatures returned back to normal very quickly, within a couple of decades. So, as quickly as 50 years, for example, and that's just a normal process.  Basically there's a big kick to the Earth's system because of these volcanic emissions and these particles in the atmosphere, so they reduce the energy but, all of these particles eventually fall out of the atmosphere, and the Earth's temperatures can basically return back to normal.

Georgia - Is it just the cooling temperatures that volcanos could have impacted?

Anja - No.  Actually some scientists actually thought about the fact that, following a volcanic eruption, the atmosphere gets very, very acidic and you get what we call "acid rain."  Acidic rain can actually damage vegetation, so we also assess this in our model, and what we actually find is rather surprising.  We find that in some parts of the world, vegetation would indeed have died off because of the acid rain but, this effect, we don't see it on a global scale.  So we can't explain a global scale mass extinction with acid rain due to volcanism.

Georgia - In your paper you mentioned that this simulation would be accurate provided that climate feedback systems, so the way the climate worked in the past, was the same as it is today.  Do we have any reason to suspect that it was the same?

Anja - We don't know for sure because we are really talking about many million years ago.  So we had to make this assumption, that was the best assumption we could make at the time, but it could well be that the climate feedbacks would actually be very different in ancient times, but we still don't know. So that's another area of research, to understand climate feedbacks.  So how does the climate react to a volcanic forcing, as we call it, so if the system is kicked by a big volcanic eruption - how does it react?

Georgia - Why should we care what killed the dinosaurs that happened 60 million years ago?  It's probably not going to happen again.  Why research this?

Anja - So, I think one thing is dinosaurs are really, really fascinating.  Young and old are fascinated by creatures that are not around anymore.  They were really, really powerful; they also looked a bit weird didn't they with their head gear, some had really nice colours and even feathers, and I think it's fascinating and they were so powerful and we still don't understand what actually killed them.  So that's one reason to study that, and in terms of volcanic eruptions, I think it's very important to understand what volcanic eruptions can do to climate and the environment because, for sure, there may be another eruption in our lifetime.  Completely different than the eruption I was talking about in my study, but you may also know that now people are talking about ways to mitigate global warming, and one of these is called geoengineering.  So people propose to put in tiny particles into the atmosphere; very similar to what we have after a volcanic eruption.  So my work can also help to understand the consequences of doing this kind of geoengineering.