Source: BBC Radio 4: Today Programme
Date: 21/10/2011
EventAn interview with BEST's Richard Muller

  • Richard Muller: Lead scientist, Berkeley Earth Surface Temperature Project
  • Justin Webb: Presenter, BBC Radio 4: Today Programme

Justin Webb: A new analysis of the Earth's temperature record over the last 50 years suggests that global warming is real. The Berkeley Earth Project was set up after the Climategate hoo-hah at the University of East Anglia to take another look at all the available data and to do so in an open manner that allows no room for doubts about information being hidden or doctored. Richard Muller is the lead scientist for the project and he is on the line now, from California. Good morning to you.

Richard Muller: Good morning.

Justin Webb: What have you found?

Richard Muller: Well, we took the issues that had been raised by the sceptics - there were four of them - that had threw [sic] some doubt on the previous analysis. We studied each one of those, carefully. We set up a whole new analysis system, using all the world's data. But in the end, our results turned out to be very similar to what the previous groups had. We see about - on the land, we see nearly a degree Celsius of global warming over the past 50 years. 

Justin Webb: And how certain can you be? I mean, with what degree of accuracy are you saying this, now?

Richard Muller: Our accuracy is actually very carefully determined. It's about 4%. So we're seeing, actually the number is 0.9 degrees Celsius plus or minus about 0.04. So it's quite accurate. What we do is we have detected, by using these thermometers - we have over 37,000 stations around the world - we've analysed five times as much data as anybody else has ever looked at. Five times as many stations. And - so we get a very good, accurate - 

Justin Webb: But - 

Richard Muller: - answer, but what we don't address is how much of this is due to humans.

Justin Webb: Ah. Yeah, okay, we'll get on to that in a second. Just on the accuracy of the data, though, we all know that one of the criticisms in the past has been that we're not always comparing like with like when we do it over time. In other words, weather stations - a) they might not exist in the same places that they were before, or there might be more of them in different places, but also, crucially, that the area where they are might have got hotter, there might be a city or an airport built nearby, and all sorts of adjustments have to be made, that make the final results pretty cloudy. And you haven't found a way around that, have you?

Richard Muller: Oh yes, we have. In fact that's what our study did. Those were precisely the things that got us into this business; this is why we studied it. The station quality was reported - I think, accurately - to be in poor locations. So one of the things we did was to analyse the stations, only those stations that were in poor locations, and compare them to the answer we got when we looked at the stations that were rated as very good. Somewhat to my surprise, I have to confess, we got the same temperature rise in both.

Justin Webb: But have you not also estimated, though, between stations? Which is going to raise people's eyebrows. 

Richard Muller: Estimated between stations?

Justin Webb: Yes, estimated what the temperature difference has been at points between stations, not just in the stations themselves.

Richard Muller: Well, we carefully looked at the correlations between stations, and we found that if you have a station that's near another station, you're very good at predicting what it is. This was - enabled us to build a correlation plot, which allows us to interpolate between stations. So we've done a very careful job on that, using well-established methods of statistics. There were 37 stations around - 37 thousand stations around the world. We really get very good coverage of the world.

Justin Webb: And have you also answered the question which is raised, again, by sceptics, about whether or not global warming has stopped in the last ten years?

Richard Muller: In our data, which was only on the land, we see no evidence of it having slowed down. Now the evidence which shows it being stopped is a combination of land and ocean data. The ocean does not heat as much as the land, just because it absorbs more of the heat. And when that data are combined with the land data, then the other groups have shown this where it does seem to be levelling off, but we have not seen that on the land data. 

Justin Webb: Mmm. And just a very final point. You've brought it up earlier, but it's a very important one. You are not, then, saying: as a result of what you’ve discovered, this is certainly due to man-made global warming.

Richard Muller: If we had seen no warming whatsoever, that would have indicated there’s no man-made global warming. If we saw twice as much, we’d be deeply concerned. But, in fact, we’re basically seeing what the other groups have reported, but we’ve made no independent assessment of how much of this is due to humans and how much is natural.

Justin Webb: Richard Muller, thank you very much.