One of my students asked me about a new article just printed in The Daily Mail, a right-wing newspaper in the U.K. The article’s title is, “Forget global warming – it’s Cycle 25 we need to worry about (and if NASA scientists are right the Thames will be freezing over again)“. Here’s a rule of thumb for you. If you ever read anything about climate change in The Daily Mail, the odds are excellent that it’s nonsense. Anyway, here is what I told my student.
Hi [Name Removed],
This is why I’ve gone all militant on these guys.
Solar activity is explicitly incorporated in climate models. It’s difficult to predict what the Sun will do in the short term, though, so projections based on the models make some assumptions about that, but at least you can incorporate measured values when you are “hindcasting” the models.
Anyway, here is the Met Office press release about the paper they are probably referring to. Now, let me show you how people like this Daily Mail reporter manipulate the public.
1. They cite a reputable source, the UK Met Office, but they don’t actually quote the paper or anyone from the Met Office. Why? Because “climate” is about long-term averages and trends, so real climatologists don’t go about announcing that “there hasn’t been any global warming in (fill in the blank with a number less than about 30) years”. The weather is a chaotic system, so in the short term you can get just about any trend you like.
2. All you have to do to get the trend you want is to “cherry-pick” the start and end dates. In this case, they pick 1997 and 2011. (They also cherry-pick the dataset, even though the press release I linked gives different results for the NASA and NOAA datasets. The one from the Met Office, HadCRUT, doesn’t include the polar regions, so it usually gives a little less steep warming trend than the others.) The problem is that the overall trend for the last 30-40 years is between about +0.15 and +0.2 °C per decade, but the interannual variability is about +/-0.2 °C PER YEAR. So you can definitely see a distinct trend if you go back far enough, but the random noise can give you all sorts of results in the short term. Let me illustrate. I calculate that the trend in the HadCRUT data from 1997-2011 is about +0.01 °C per decade, and not statistically significant. (In this case, a statistically significant result is one where the 95% confidence interval does not overlap zero.) What happens if we change the start and end dates by just one year, from 1996-2010? Then the trend is 0.10 °C/decade, and still not statistically significant. Do you see how you can use the random noise, e.g., from El Niño and La Niña oscillations, to get the trend you want in the short term?
3. Next, they launch off into their nonsense about how the flat temperature trend is all because of a decrease in solar activity, and we’re heading into a new Little Ice Age. The press release the Met Office put out just prior to the one I already mentioned was entitled, “Decline in Solar Output Unlikely To Offset Global Warming“, but the Daily Mail reporter says that these findings are “fiercely disputed by other solar experts,” and quotes Henrik Svensmark. I could name a couple other solar guys who agree with Svensmark, but that’s all. He’s definitely on the fringes. Svensmark has an interesting theory about why changes in Solar output might exert a much greater influence on climate than the models give it credit for, but the problem is that the statistics don’t pan out.
4. But wait! Just in case people didn’t buy the Solar connection, let’s completely switch gears and blame the whole thing on ocean circulation! The ridiculous thing is that the standard climate models DO incorporate ocean circulation AND variations in Solar output, and these things DO affect the temperature projections so that any given model will predict periods of several years where there might even be overall cooling. The models just differ about when these “pauses” in global warming will happen, because the system is chaotic and the timing of these things are incredibly sensitive to initial conditions and the model details.
5. If the scientific consensus doesn’t agree with what you want to hear, the Daily Mail reporter knows that you can always get some D-list fringe scientists to make it all better. E.g., take a look at Nicola Scafetta, who thinks that Jupiter and Saturn are affecting the climate to create a 60-year cycle, which Judy Curry also apparently buys into. Yep. But don’t ask Scafetta or Curry what Jupiter or Saturn are supposed to be doing that affects the climate, because they can’t give any physical mechanism. Maybe that’s why the Daily Mail calls Curry “one of America’s most eminent climate experts.” Whatever. Also, take a look at Benny Peiser, who is a social anthropologist too ignorant to properly read the scientific literature on climate change.
Now, take a step back and look at what has been done to the public. Most people have no idea about statistical cherry-picking, and even those who do wouldn’t necessarily suspect anything. Most people would have no idea that the Daily Mail is quoting a bunch of fringe scientists, and they would have no idea why the views of these scientists are dismissed by the others. It turns out that Svensmark WAS taken seriously, but his hypothesis hasn’t panned out. It turns out that Scafetta’s ideas are little better than curve-fitted astrology, at this point. It turns out that climate models DO account for ocean circulation, but there is no convincing evidence that this does much outside timescales of a few years.
Like I said, this is why I’ve gone militant on these guys. I think they are patently dishonest.
[UPDATE: The Met Office has now responded to the Daily Mail article. They said essentially the same thing I did.]