I have to add an addendum to my last video because no sooner had it come out than the perfect example of what I was saying was splashed all over the internet. It was a headline that read, there has been no global warming since 1995, and I'm sure you've all seen it. The source for most of these stories and even the headline was an article in Britain's Daily Mail on February the 14th, but remember what I said in my last video. And out where the information comes from, is the source reliable? Does the information you've been given accurately reflect the information from the source? So instead of trusting the Daily Mail to accurately report what Phil Jones said, why don't we go to the BBC website and read the transcript and find out what he actually said. The headline in the Daily Mail was this, climate gate you turn a scientist at centre of ROW admits there has been no global warming since 1995, but that's not what Phil Jones said. If we go to the source, the BBC transcript, we find this. Phil Jones was asked if he agreed that from 1995 to the present there's been no statistically significant global warming. Yes, he said, but only just. I also calculated the trend for the period 1995 to 2009. This trend, 0.12 degrees centigrade per decade, is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. This is not the same as saying there's been no warming. Firstly, the word significant in statistics doesn't indicate how much or how important something is, but how more likely it is to have occurred by chance. It's a function of the strength of the thing you're measuring, the strength of the background noise and the size of the sample. Phil Jones and his team could measure global warming, he even gave the BBC the figure, but they couldn't be absolutely sure that this trend was real and not just a chance anomaly caused by background variations in temperature. Most researchers aim for a significance level of 95%, meaning they've got 95% confidence that a trend is real and not chance. Jones said he got close to that. I don't know what figure he reached, but just for an example, let's say it was 80%. That would mean there's an 80% probability that the warming he detected between 1995 and 2009 was an underlying trend and not a chance result caused by natural background temperature fluctuations. Of course, the greater your sample size or the longer you measure something, the more significant your results become. Let's go to the beach for an example. It's a bit like measuring waves coming onto the shore. If you mark how far each wave comes up the sand with a flag, can you tell whether the tides coming in? Over a short period of time, say half an hour, your flags might progress very slightly up the beach, which would indicate that the tides coming in, but the distance is so small that it's possible it's been distorted by one or two strong waves. To use the daily males understanding, this means there's been no movement up the sand for half an hour so the tide can't be coming in, but it doesn't. It means there has been movement up the sand, but it's not enough and the time scale is too short to say with confidence that the tide is coming in. Okay, one more example and then I'll shut up about statistical significance. God, I hate statistics. Let's say you're suspicious that a dye has been weighted in favor of falling on a six. If you roll the dye a couple of times and it comes up with sixes both times, can you say with confidence that it's been weighted? No, because you could have got those two sixes through pure chance. So you keep rolling and here's what you get. A six, a five, a six, a six, a four and two more sixes. How confident are you now? Well, it's beginning to look as though the results are because of waiting rather than chance. The significance of our results is rising, but it still could be chance if we're almost at the 95% significance level but not quite there, what would the daily male make of these results? They'd say that since the figure isn't significant, it means the dye isn't weighted. Okay, it's complicated, but this is why science is published in scientific journals, not in the tabloid press. The daily male did get the quote right in the body of the story but didn't explain what it meant. So readers were left with the impression from the headline that it meant there's been no warming. So why did Jones go on to say in the BBC interview, he was 100% confident that the climate has warmed. Well I can't speak for him and I don't think any scientist can express 100% confidence in anything. But what he was probably referring to was that the C.I.U. together with the Hadley Centre has more than just 15 years of data to draw on. Let's go back to the analogy. If we keep planting flags over a longer period of time, say an hour, the movement of flags up the beach overcomes the background noise of advancing and retreating waves and it becomes very clear that the tide is coming in. So Jones is looking at over 30 years of data, which shows the warming trend very clearly. Not surprisingly the daily male completely omitted Jones' statement that the Earth was warming. If we look at data from the other surface temperature monitoring bodies, the GISS and NOAA, the warming trend comes through more clearly, so the statistical significance is higher. This is because there are a few weather stations in the Arctic or Antarctic, so had crutt, that's the C.I.U. and the Hadley Centre's combined data, leaves these areas out. God-Arden NOAA extrapolate Arctic and Antarctic temperatures from the nearest available weather stations, so their coverage is more extensive. Since the Arctic is the fastest warming part of the planet, God-Arden NOAA show much more warming than had crutt. I showed this in my last video, has the Earth been cooling. It's not hard to spot other errors and misquotes. The daily male told us that Jones conceded the possibility that the world was warmer in medieval times than now, but that's rather like asking a climatologist who argues that the medieval warm period was warmer than today, whether it's possible it was cooler. If he's being honest, then he'd say yes, of course it's possible. That shouldn't be misconstrued as a concession or an admission that he's wrong, the geographical extent and nature of the medieval warm period is not known. In the BBC interview Jones gives a fair summary of the state of our understanding. Read it, he doesn't concede or do a U-turn on anything. The daily male goes from that to this. Skeptics said this was the first time a senior scientist working with the IPCC had admitted to the possibility that the medieval warming period could have been global and therefore the world could have been hotter than now. Of course the male doesn't say who these skeptics are. They could be the office cleaners, but they're wrong and the male didn't bother to check. Here's part of the IPCC's fourth assessment report on climate change in 2007. Section 661 has a long dissertation on the nature of the medieval warm period which includes these lines in box 64. In medieval times, as now, climate was unlikely to have changed in the same direction or by the same magnitude everywhere. In other words, the IPCC doesn't say there's no way the warm climate could have been global or that it definitely wasn't, it concludes that it's unlikely to have been global. The IPCC clearly accepts the possibility that it wasn't, but nobody at the daily male bothered to check the latest IPCC documents to substantiate the claim that it doesn't accept such a possibility. And neither did any of the scores of blogs and commentators who paraded this assertion. But then the daily male goes on to make an assumption based on what it thinks is Professor Jones doing a U-turn. This suggestion doesn't come from Jones or the BBC or anyone named by the male, it seems to come from the writer and editor at the male who put the story together. I know a lot of editors at the male and the nugget of science they understand is so small, it can be drowned in their lunchtime jins and tonics. They shouldn't be used as a credible source on this complicated aspect of science. So once again, I would urge internet lovers to be skeptical, don't believe something you read simply because it's in a tabloid newspaper. If it gives no source for the information, treat it with skepticism. If it does give a source, don't let the tabloid editors interpret it for you. Read the source yourself and check whether the interpretation you've been given is accurate.