Science under attack

I had planned another subject for todays blog, but having watched the recent Horizon programme on science under attack on BBC iplayer (still available for those with a British IP address) I thought it tied in rather neatly with why I decided to start this blog.

In the first place the idea came to me to start a blog as a way of practicing my own writing skills. Then secondly I thought I might have something interesting to say. When people find out I’m a climate scientist I often get all sorts of questions about climate change ranging from the basic (is it really happening?) to the more nuanced and complex (how do models work?) to, unfortunately, yet another repetition of the usual climate myths (see below). This blog should be a small window on the world where I write about things that interest me and hopefully are interesting to others.

Cartoon from the Union of Concerned Scientists

As I looked in to the world of blogging, and in particular into blogging on climate related themes, a huge number of blogs came up. Unfortunately, many of them are rather weak on science and very overtly political. In fact a quick scan of the google hits brings up rather more blogs and websites by what might (kindly) be called “sceptics” (or otherwise known as “deniers”) than blogs created by scientists. There is some really good material on the web dealing with climate related issues, for example the excellent blog but in many other places there is a lot of dross and the same empty myths endlessly recycled and repeated (for example, “it’s the little ice age”, “it was warmer in the Medieval period”, “it’s sun spots” etc etc), largely I’m afraid due to lazy and/or politically motivated journalism. All of these common myths have been explained over and over again, usually by people far better qualified, and far more skilled in writing than I, yet somehow they seem to persist.

As the Horizon documentary made clear, this is a source of immense frustration to many in the climate field, including myself, so I feel the time has come to stick my head above the parapet so to speak and start broadcasting my own opinions. At least I hope it will be a small addition to the counterbalancing work done by people like Real Climate and maybe it will help open some minds.

The same documentary blamed scientists for being poor communicators and I would tend to agree with that, it’s hard to talk about uncertainties in models for examples when even the word uncertainty is used very differently in science than in everyday life. On the other hand, this article on communication in the journal Nature by Tim Radford suggests that in fact scientists can be good communicators and he cites such luminaries as Carl Sagan, E.O. Wilson, Stephen Jay Gould and even Richard Dawkins (although I fear the latter has alienated a large part of the audience with his agressive approach to atheism). These are all great examples of great communicators of science, and though I fear I couldn’t possibly get close to their talent, I hope that this blog will help to develop my skills further.

One further point, Ben Goldacre, the Guardian’s excellent bad science columnist is a witty, knowledgeable and hard working advocate of good science who works tirelessly against vested interests, quackery, big pharma and other ‘enemies of reason’. In this post about the Copenhagen climate summit he explores the psychology of climate science and why it is so difficult to communicate. He points out that

‘climate science is difficult. We could discuss everything you needed to know about MMR and autism in an hour: the experimental techniques of epidemiology and other disciplines, how they’ve been misrepresented, the results, strengths, and weaknesses of the key studies. Climate change will take two days of your life, for a relatively superficial understanding: if you’re interested, I’d recommend the IPCC website itself, where they have a series of three executive summaries for policy makers, which are perfectly good pieces of humourless popular science writing.’

This is very true and I am certainly not going to use this blog to explain all issues related to climate change research. In fact, I aim to produce pieces about all sorts of scientific curiosities, natural wonders and society’s response to these. I have imposed two other conditions on myself. Firstly, I should not spend more than an hour on any one post and secondly, I want to post at least twice a week. I’ve broken the latter already, but thanks to my friend Heather I’ve been inspired to try again.


Forecasting the weather part 1: Differences between forecasts

This is the first part of an occasional series that I intend to write about why it’s so difficult to forecast the weather. In the UK the forecast can be notoriously wrong but it seems to me that most people have no idea how difficult it is to make a good forecast, especially in a maritime climate with air masses coming from all sides. This first piece is based on something I wrote for an online forum when another forumite complained that there were two different forecasts for their area that never seemed to agree.

The divergence between two weather forecasts for the same area over the same period can actually come from a whole range of differences between the different forecasters. In Europe most forecasters use the same observational dataset provided by the European Centre for Medium Range Weather Forecasting (ECMWF). This cuts out one set of problems as weather is famously chaotic and very small changes in starting conditions can lead to big changes in outcome, otherwise known as the butterfly effect. The famous storm of 1987 which destroyed millions of trees in southern England and caused millions of pounds of damage but which was not forecast accurately turns out to have been a super unpredictable event as shown in this talk given at the American Geophysical Union in San Francisco in December 2010. However, chaos theory is fascinating in it’s own right so perhaps I’ll give it a post to itself another time.

In day to day forecasts, the biggest difference is probably in the resolution of the model (if you imagine that an area, say the UK, is divided up into little squares, the computer model solves a whole lot of equations for each square).
If the square is 5km by 5km in size then some processes, and a lot of the topography will be smoothed out, but if the square is 500m by 500m then a lot more will be captured. Imagine a hill of 1000m rising out of a flat plain only 100m high in a particular location. The elevation of the square is the average of the whole elevation. In the 5km by 5km model, the entire hill and an equal area of plain is captured so in the square the average elevation may be 500m, but in the 500m by 500m model it may need 4 squares to accurately cover the hill alone and each square will have a different elevation.

Temperatures typically go down as you go higher, and rain will fall as the air cools, so if the hill isn’t “resolved” in the model the prediction may be unrealistically warm and dry. This is why forecasters like high resolution models, but that resolution comes at a high cost, because you need to increase the vertical resolution (the number of squares in the atmosphere) and reduce the length of time between each calculation as the horizontal resolution increases.

Another source of difference are the actual equations solved in the model. These can be formulated in different ways and with different approximations and are often “tuned” so a model that works really well in Scotland is unlikely to be so successful in the Sahara (where I imagine forecasting is actually pretty easy – it’ll be hot and sunny). That’s not to say the models are “wrong” just that they perform better in some circumstances than others and are designed for different purposes often.

Finally, a further important difference is the updating of the model with real time observations and at the boundaries. Most models are not run for the whole wold, but only a small portion (the whole world can be run at a resolution of about 20km nowadays, but it takes a lot of very expensive computer power). More effective is running a small section (say the UK), and telling the computer what is happening at the edges of the box based on satellite and ground observations. These can also be fed in to the area within the model to nudge it in the right direction. In practice as I mentioned earlier, in Europe most national agencies get this information from a single source, the ECMWF. Also, the models tend to be “better” than the observations (as measurements can go wrong, instruments might be wrongly calibrated etc), so at any given moment a weighting of about 40% is applied to observations and 60% for the model, depending on what in particular you’re looking at.

So the accuracy of any forecast depends on where you live and also how far in the future you need your weather to be reliable. Most forecasts aren’t bad up to 3 days in advance in general terms but the specifics can change quickly. Beyond that to 5 days is more tricky and depends on the large scale situation, for example is there a stable high pressure dominating or a series of storms and which way will a weather system move. Beyond a week to 10 days the forecasters are basically just guessing (at least in a maritime climate like the UK) and this why the met office has recently discontinued seasonal forecasts as they can be very unhelpful.