select search filters
briefings
roundups & rapid reactions
Fiona fox's blog
Research suggested a new model by which cosmic rays may interact with atmospheric aerosols during cloud formation.
Prof Mike Lockwood, Professor of Space Environment Physics at the University of Reading, said:
“The main thing is that when you look at something in a new way, to unprecedented resolution and standards (in this case of cleanliness) you discover new things. The CERN scientists have done this – they have used their know-how on running really clean vacuum experiments to do something new. It is like working in space, any material that can outgas contaminants will do so and so has to be eliminated. This they have done to a degree that is better than any previous experiments by a huge and significant margin.
“There are a number of results in here. The one that will get climate change sceptics excited is that they have found that through the influence of sulphuric acid, ionisation can enhance the rate of water droplet growth at the temperatures characteristic of middle troposphere. Does this mean that cosmic rays can produce cloud? – No. There are two issues that mean the results fall a long way short of that. Firstly, the ion-induced aerosols only grew to about 2 nm (nanometers) and to influence incoming or outgoing radiation to Earth, droplets must be of order 100 nm. The growth rates would be really slow from 2 to 100nm because there simply isn’t enough sulphuric acid in the atmosphere. Nevertheless, it seems that air ions generated by cosmic rays can help get them started, and that is something that has been often talked about but hasn’t been seen unambiguously before. The second caveat is that as yet the experiment is not reproducing the true mix of constituents in the mid troposphere. There are a great many arguments as to why the cosmic ray cloud effect is not a major driver of climate change and these results do not yet impinge on those arguments.
“For me, much more exciting are their results simulating the higher-temperature boundary layer. Here we can see the real benefits of the lack of contaminants. The authors have shown results from previous experiments were greatly influenced by, in particular, unrealistic ammonia. When they reduce this effect by removing this contaminant to an unprecedentedly low level they show that aerosol production rates are much, much lower than in the real atmospheric boundary layer. This means something else, as yet unknown, is helping enhance the nucleation rates there. Depending on its source, this could even be an unexpected additional anthropogenic climate forcing or feedback.
“I have always been a big supporter of the CLOUD experiment because I believe it will generate data of greater precision and realism and, given time, should answer some important questions in an area where real information is sorely lacking. These first data illustrate that it really can deliver new understanding but they certainly do NOT prove the cosmic ray cloud hypothesis!”
Prof Piers Forster, Professor of Climate Change at the University of Leeds, said:
“This work addresses the uncertain aerosol-driven aspects of climate which is additional to the well-established effects of greenhouse gases. The press release puts too much emphasis on the cosmic ray findings from the paper, the work does indeed confirm that cosmic rays help produce aerosol particles but it also clearly shows that they are not a major contributor in the lower atmosphere.
“This makes it extremely unlikely that they can affect low clouds anywhere other than cold and pristine marine environments. This paper is also very much only a first step in the quantification of the climate effect of cosmic rays, so it would certainly be wrong to conclude that cosmic rays are a major driver of climate change. Intriguingly the paper suggests that other substances are also affecting aerosol formation in the lower atmosphere. These substances could be organic molecules which would leave the door open for a biological feedback on clouds and climate, pleasing proponents of Gaia theory.”
Prof Sir Arnold Wolfendale FRS, Emeritus Professor of Physics at Durham University, said:
“The impending publication of work on cloud nucleus production by man-made ‘cosmic rays’ at CERN has focused attention on the possibility – favoured by some – that Global Warming is somehow due to cosmic rays. Having spent much of the last 4 years studying this question from a variety of standpoints I feel justified in making a considered statement on the problem; this is that their effect is very small.
“The idea of a link between cosmic rays and climate is at least 60 years old, the argument being that cosmic rays produce ‘ions’ (electric charges) as they pass through the atmosphere and these act as ‘condensation centres’ for clouds. Since the cosmic rays vary in number somewhat on all sorts of time scales, clouds should do likewise; in turn, since clouds affect the climate—and ground level temperature –the potential is there for a Global Warming link.
“A decade or so ago the idea received a boost with the demonstration of a correlation (i.e. a proportionality) of low cloud cover and cosmic ray intensity, the cloud data coming from satellite data and the cosmic ray numbers coming from a world-wide set of reliable ‘neutron monitors’. Over an 11-year ‘solar cycle’, when the number of sunspots was high–and the cosmic ray intensity was low– the low cloud cover was low. Since there has been a slow fall in cosmic ray intensity over the past century the low cloud cover would fall and the ground level temperature would rise. Voila: Global Warming.
“Detailed analysis shows many problems, however. These can be numbered:
1. A ‘correlation’ does not necessarily mean cause and effect. Both could be due to a third effect. In this case it could be the solar output itself that is the culprit. The size of the British Empire correlates (negatively) with the number of British homes having central heating but one does not cause the other.
2.,Only the low cloud cover correlates. Middle and high cloud does not. This is bad news for the hypothesis since the variations in cosmic ray intensity are bigger at the higher altitudes.
3.,The more recent 11-year solar cycle showed an inferior correlation.
4.,The correlation should vary with position on the Earth’s surface in a particular way, due to the Earth’s magnetic field. It does not.
5.,Certain types of cloud should show the correlation more so than others; they do not.
6.,High energy cosmic rays produce ‘showers’ of secondaries in the atmosphere which should produce ‘cigar-shaped clouds’. They do not.
7.,Physicists love energy arguments. The energy involved in sunlight is some 100 million times that in cosmic rays and even the long– term sunlight change effects are hard to discern. It would be quite remarkable if cosmic rays were to be so much more efficient.
8.,At the detailed level, over the past 50 years the averaged cosmic ray rate has ceased to fall but the Global temperature has increased at an accelerated rate. In fact the increase mirrors that in CO2, but that’s another story.
“Checks on the cosmic ray hypothesis are possible using other sources of ‘ions’. We have examined three, as follows.
1.,Natural radioactivity. Some areas have very high levels and we have examined one such: South-west India. We find no extra cloud.
2.,The Chernobyl disaster. There are data on the fall-out pattern and the cloud cover. There is no correlation
3.,Nuclear Bomb tests. There is a wealth of data on the effect of ‘atomic bombs’ on ‘weather’. Apart from the mushroom cloud, and other very local effects, there is none.
“Turning to the data expected from CERN, inevitably there will be some effect of ions on the atmosphere .The question is ‘how much’ compared to other effects. Many processes contribute to cloud droplet formation. The CERN results show that ions add one more and a small one at that.
“In conclusion we know of no evidence favouring a cosmic ray effect on climate at more than a few percent (10% at the maximum over the last 150 years). However, the Earth’s atmosphere is such a complex entity that it would be unwise to let up on efforts to understand it–whether it be at CERN or elsewhere.”
‘Role of sulphuric acid, ammonia and galactic cosmic rays in atmospheric aerosol nucleation’, Jasper Kirkby et al, published in Nature on Wednesday 24 August.