Howard Burton - Solar Impact: Climate and the Sun: A Conversation with Joanna Haigh

Meteorology is a hard field.

To understand whats happening with our climate you need to understand a wide smattering of physics, from mechanics to electrodynamics to thermodynamics, to get a general picture of the underlying processes at play, many of which interact with each other in far from straightforward ways. But thats only the beginning.

Once you get to the stage of building models, their success will naturally depend on a clear understanding of what is happening both now and in the past, which in turn necessitates the incorporation of a staggering array of meticulous observations of the atmosphere, oceans and ice cores over a long period of time.

Of course, in order to somehow process all this data, you need nothing less than a mind-boggling amount of computing power; but even once you manage to get a hold of that youll find yourself suddenly facing the aptly named complexity framework of nonlinear dynamics where each run-through will be subjected to the so-called butterfly effect, ensuring that you perform at least a few thousand separate simulations before you can begin to have real confidence in the value of the outputs.

Hopeless, then?

Far from it.

Joanna Haigh, Emerita Professor of Atmospheric Physics and former Co-Director of the Grantham Institute at Imperial College London was studying the complex interaction between the physics of the stratosphere and the chemistry in the ozone layer when she came across a claim promoting a particularly intriguing correspondence.

There was a paper published by somebody who showed these graphs; one was the temperature in the Northern Hemisphere and the other, a measure of solar variabilityit wasnt actually solar irradiance, it was something to do with the sunspot cyclesand in these two graphs the lines almost precisely overlaid each other. The article was in Science, a very reputable journal, and I thought, Thats interestingthere must be something in that .

This was at a time when people were starting to take an increased interest in climate change, and there were people who were saying, Well, its all due to the sun . And if you looked at these graphs, thats exactly what you might think. So I said to myself, Ill take a closer look at that .

As you might imagine by now, taking a closer look was hardly straightforward. First you have to understand what solar variability really is and what is producing it, and then you have to understand how the authors of the paper had produced their results.

So it was complicated. But eminently feasible.

It became clear that the people who had analyzed the data hadwell, lets just say that their analysis techniques left a little bit to be desired. In fact, if you do it properly, solar variability doesnt go up at the same rate as the temperature, so actually, it was quite flawed.

However, that paper was usedquite shamelessly and for many years thereafterby people who wanted to say that climate change was due to the sun. Its actually only stopped recently, so it had a big impact.

Welcome to the world of highly politicized scientific research. Yet another complication.

Meanwhile Joanna, having turned her attention to the question of solar variability, began to look more carefully and rigorously at what its precise effects might be.

The radiation that is important in the stratosphere for ozone and so forth is ultraviolet, which is why my ears pricked up when I initially heard about this business of solar variability, because the UV variation is much largerwell, its only a few percent, but thats much larger than 0.1% for the total radiationwhich made me think, Well, that could do something . So, I started looking at how changes in the UV spectrum could influence the climate.

Not surprisingly, what happens is that the temperature in the stratosphere goes up and down quite a lotby a few degreesand thats being measured by satellites and its fairly well understood in general. So, you might say, Well, changes in the stratosphere, thats all very interesting for people working on stratospheric chemistry and the ozone layer, but does it have any effect on us living on the earths surface? Thats what Ive spent some time working on.

Meanwhile, of course, the question of climate change became increasingly present in the public consciousness. Was it really happening? To what extent? How confident could we be that the causes were man-made?

And once more, a common argument invoked by climate-change sceptics was one of complexity. There was, they claimed, simply no way of knowing for sure what was going on. There were all these different modelssome people said this and others said that and nobody could know for sure what was actually going on.

But it turns out thats not actually true. A very strong scientific consensus has emerged that theres no way to explain the increase in global temperatures without anthropocentric factors being taken into account.

You could perhaps get away with it until about 1960 or something, but you cannot get global warming without increased greenhouse gases or some magical factor that nobodys thought of. And I think its unlikely to be that because if we do the physics and we put all the other factors that we know about into the big models, we can reproduce the temperature change fairly well.

So yes, its complicated. Very complicated, even. But shouldnt that be a cause for celebration that weve actually been able to truly figure some things out?

Youd certain think so, particularly when such things have a tremendous impact on so many peoples lives around the planet.

So why are people so slow to take meaningful global action? Why do so many climate-change sceptics exist despite all the strong scientific evidence to the contrary? Why are so many convinced that global warming has nothing to do with human activity?

Well, some questions might well actually be impossible to answer.

But climate change isnt one of them.