This new paper shows what appears to be a link between Forbush descreases and terrestrial temperature change shortly afterwards. It is a short time scale demonstration of what Svensmark is positing happens on a longer climate appropriate time scale as the solar magnetic field changes with long periods. I’ve covered the topic of Forbush decreases before, and thus I’ll draw on that for a refresher.
A Forbush decrease is a rapid decrease in the observed galactic cosmic ray intensity following a coronal mass ejection (CME). It occurs due to the magnetic field of the plasma solar wind sweeping some of the galactic cosmic rays away from Earth.
Well we have that going on in a dramatic way right now [Feb 19th, 2011], it’s been going on since late yesterday. See the Oulu neutron monitor (a proxy for cosmic rays) graph:
You can monitor it live on the WUWT solar page here.
Nigel Calder reports of a new peer reviewed paper from the Institute of Physics in Belgrade, Serbia which demonstrates a link between such Forbush events and the increase in the diurnal temperature range averaged across 184 stations in Europe. It is quite compelling to read.
Europe: diurnal temperatures after Forbush decreases
A. Dragić, I. Aničin, R. Banjanac, V. Udovičić, D. Joković´, D. Maletić and J. Puzović, “Forbush decreases – clouds relation in the neutron monitor era”, Astrophysics and Space Sciences Transactions, 7, 315–318, 2011.
It was published on 31 August and the full text is available here http://www.astrophys-space-sci-trans.net/7/315/2011/astra-7-315-2011.pdf It’s typical of the pathetic state of science reporting that I still seem to have the story to myself ten days later.
The focus was on the “natural experiments” in which big puffs of gas from the Sun block some of the cosmic rays coming from the Galaxy towards the Earth. The resulting falls in cosmic ray influx, called Forbush decreases, last for a few days. The game is to look for observable reductions in cloudiness in the aftermath of these events. The results are most clearly favourable to the Svensmark hypothesis for the Forbush decreases with the largest percentage reductions in cosmic rays. Scientists keen to falsify the hypothesis have only to mix in some of the weaker events for the untidiness of the world’s weather to “hide the decline”.
The Serbs avoid that blunder by picking out the strongest Forbush decreases. And by using the simple, reliable and long-provided weather-station measurements of temperature by night and day, they avoid technical, interpretive and data-availability problems that surround more direct observations of clouds and their detailed properties. The temperatures come from 184 stations scattered all across Europe (actually, so I notice, from Greenland to Siberia). A compilation by the Mount Washington Observatory that spans four decades, from 1954 to 1995, supplies the catalogue of Forbush decreases.
The prime results are seen here in Dragić et al.‘s Figure 5. The graphs show the increase in the diurnal temperature range averaged across the continent in the days following the onset of cosmic ray decreases (day 0 on the horizontal scales). The upper panel is the result for 22 Forbush events in the range 7−10%, with a peak at roughly +0.35 oC in the diurnal temperature range. The lower panel is for 13 events greater than 10%. The peak goes to +0.6 oC and the influence lasts longer. It’s very satisfactory for the Svensmark hypothesis that the effect increases like this, with greater reductions in the cosmic rays. The results become hard (impossible?) to explain by any mechanism except an influence of cosmic rays on cloud formation.
To be candid, these results are much better than I’d have expected for observations from a densely populated continent with complex weather patterns, where air pollution and effects of vegetation confuse the picture of available cloud condensation nuclei. Svensmark’s team has emphasised the observable effects over the oceans. Now the approach taken by the Belgrade team opens the door to similar investigations in other continents. Let a march around the world’s land masses begin!
Physicist Luboš Motl also writes about the new paper:
What have they found? If they take all Forbush decreases, the effect is insignificant. However, if they compute the average of the largest Forbush decreases, they find a substantial increase of the day-night temperature difference by as much as a Fahrenheit degree around 3 days after the event [reference to Figure 5 above].
A higher day-night temperature difference indicates that the number of clouds is smaller – because clouds cool the days but heat up the nights a little bit, and thus reduce the temperature difference – which is in agreement with the cosmoclimatological expectation: the Forbush decreases makes the galactic cosmic rays disappear for some time (because of some massive, temporarily elevated activity of the Sun).
I think it’s both simple and clever to look at the day-night differences because the overall noise in the temperature is suppressed while the signal caused by the clouds is kept. Just to be sure, it’s obvious that clouds do reduce the day-time differences but that doesn’t mean that they preserve the day-night average. At typical places, they cool the days more than they heat up the nights.
For me, this paper begs replication and confirmation. The problem they have with the European data set is that it is noisy which required the averaging. Here in the USA though, there’s a dataset that may work even better, and that’s from the recently completed U.S. Climate Reference Network operated by the National Climatic Data Center. While that network is too new to be useful yet for long term climate studies, the care that was taken for station siting placement, accuracy of sensors, data resolution, and quality control make it a perfect candidate for use in replication of this effect.
These stations were designed with climate science in mind. Three independent measurements of temperature and precipitation are made at each station, insuring continuity of record and maintenance of well-calibrated and highly accurate observations. The stations are placed in pristine environments expected to be free of development for many decades. Stations are monitored and maintained to high standards, and are calibrated on an annual basis.
The data is of high quality, so any new study looking for this effect may not even need to do the DTR averaging done by Dragić et al. to see the effect if it is real.
The logged USCRN data is now available online here http://www.ncdc.noaa.gov/crn/observations.htm The February Forbush decrease event I highlighted at the beginning of this post might make a good starting point.
I see a paper on this in the near future, maybe even in Dessler record time.