Paul

‘Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature’

There’s nothing really new in this paper, which is a review partly written in response to the controversial Wag TV documentary ‘The Great Global Warming Swindle.’ Not good news from the point of view of being objective, and I doubt that it’s a coincidence that the paper has found it’s way into the same journal that published Svensmark’s cosmic ray-cloud experiment. The Royal Society are very excited too: ‘Global warming: A Proceedings A paper shows that the Sun is not a factor in recent climate change!’

The Abstract states:

“There is considerable evidence for solar influence on the Earth’s pre-industrial climate and the Sun may well have been a factor in post-industrial climate change in the first half of the last century. Here we show that over the past 20 years, all the trends in the Sun that could have had an influence on the Earth’s climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures.”

An extract from the paper says:

“…it is possible that the decline seen since 1985 marks the beginning of the end of the recent grand maximum in solar activity and the cosmogenic isotope record suggests that even if the present decline is interrupted in the near future, mean values will decline over the next century. This would reduce the solar forcing of climate, but to what extent this might counteract the effect of anthropogenic warming, if at all, is certainly not yet known.”

The paper concludes:

“There are many interesting palaeoclimate studies that suggest that solar variability had an influence on pre-industrial climate. There are also some detection–attribution studies using global climate models that suggest there was a detectable influence of solar variability in the first half of the twentieth century and that the solar radiative forcing variations were amplified by some mechanism that is, as yet, unknown. However, these findings are not relevant to any debates about modern climate change. Our results show that the observed rapid rise in global mean temperatures seen after 1985 cannot be ascribed to solar variability, whichever of the mechanisms is invoked and no matter how much the solar variation is amplified.”

L&F are therefore supportive of a past and relatively recent solar influence on climate, with an ‘unknown’ amplification mechanism. Furthermore, they acknowledge that the ‘grand maximum’ of solar activity seems to be coming to an end, which raises the possibility of global cooling, long predicted by the likes of Fairbridge and Shirley (1987).

Let’s take a look at some of the contentious points relating to L&F and TGGWS :

1. Solar cycle length v temperature

The use of the 1991 Friis-Christensen and Lassen graph of solar cycle length plotted against mean surface temperature attracted much criticism because the correlation diverged after the paper was published. The graph was lifted directly from F-C & L in order to demonstrate a solar link to climate.

The sunspot cycle length data finishes after 1980 – at least 1985 – the graph just looks like it finished in 1980 because the dots are plotted in the centre of the cycle.

Additionally, cosmic ray data goes back to the 1950’s, so Lockwood is the one ignoring data that doesn’t suit him by starting the graphs at 1975 which we know was a turning point in temperature.

2. Smoothing and sunspot cycle length

When Lockwood smoothes his graph to expose the long-term trends, he basically averages the readings over the length of one sunspot cycle. Like F-C & L, he plots the result in the MIDDLE of the data range. So each point on his graph is a combination of the previous 5 years’ data with the 5 years in the FUTURE. This is the same as the FC& L graph, but Lockwood uses it to make it look like the solar activity started to fall away long before it actually did.

3. The data itself

There are several different sets of data used:

a. Total solar irradiance TSI – amount of energy arriving from sun – correlated with sunspot cycle.

(There has been some debate about the preference for Frohlich’s own PMOD data set over the ACRIM data, and the adjustment to the Lean TSI reconstruction data 2 months before the publication of the L & F paper, but I don’t intend to dwell on that here!)

b. Number of sunspots observed – averaged over a month

c Length of sunspot cycle (varies 9-11.5 years)

d Direct measurements of cosmic rays – cosmic rays are lower when sunspots higher because the solar magnetic field blocks them.

(N.B. The Berrylium10 proxy for cosmic ray flux is formed by 1 GeV cosmic rays, whereas it is 10 GeV cosmic rays that are of interest and responsible for atmospheric ionisation. Ion chambers are sensitive to very high cosmic ray energies of 10’s of GeV.)

Comparing Lockwood’s paper with Lassen’s, the main difference is that Lassen’s stops in the late 1980s whereas Lockwood’s includes one more sunspot cycle peaking in 2001.

The sunspot cycle peaks grow higher through the 1970, 1980 and 1990 peaks, which are all very large in the context of the last 150 years, and 2001 is considerably lower.

Equally, the minima in cosmic ray flux (measured at the edge of space by Lockwood) get deeper up to 1990, but the 2001 one is shallower again – about the same as 1980.

So any divergence between the solar record and the temperature record only begins in the last ten years or so, even failing to allow for the “middle of cycle plot” – not in the last 20 like Lockwood says.

L & F says that “Earth’s surface air temperature does not respond to the (11 year) solar cycle…..(due to)…long thermal time constants associated with……the oceans”

In other words, 10 years is far too short a time to show any effect from long-term solar changes. Interestingly, the temperature graph seems to level off around 2003 – as you would expect if there were a lag.

However, a new GRL paper by Camp and Tung, published 18th July 2007, claims that: “By projecting surface temperature data (1959–2004) onto the spatial structure obtained objectively from the composite mean difference between solar max and solar min years, we obtain a global warming signal of almost 0.2°K attributable to the 11-year solar cycle. The statistical significance of such a globally coherent solar response at the surface is established for the first time.”

Summary:

The ‘science’ is far from ‘settled.’

Solar activity is higher than it has been for at least 1000 years.

IPCC AR4 rates the ‘level of scientific understanding’ of ‘solar irradiance’ as ‘low,’ other solar factors have a LOSU of ‘very low.’ The emphasis is always on irradiance rather than eruptivity, which I believe is much more important.

Small solar changes seem to have a much larger influence on climate than expected, suggesting an unknown amplification mechanism.

Global mean surface temperatures have levelled off since the 1998 El Nino, and there has been little or no ocean warming for the past 5 years according to the ARGO network.

Solar cycle length, sunspots, irradiance, are general indicators of solar activity. Nir Shaviv sees no reason why the length of the solar cycle should be related to solar activity – it could be a coincidence, and it is largely a phenomenon of the Northern Hemisphere. That said, the correlation between solar cycle length and a long mean surface temperature series has also been observed at Armagh Observatory in Northern Ireland.

There is also an interesting paper from 2005, by Hengyi Weng entitled ‘The influence of the 11 yr solar cycle on the interannual-centennial climate variability.’ There is also a summary here entitled ‘Influence of the 11-year solar cycle more significant than previously thought.’

The full paper is here:

http://tinyurl.com/94dtf

Any hypothesis involving correlations between 2 variables out of many is likely to diverge at some point. The attempted 20th century correlation of CO2 and temperature diverged from the 1940’s to 1970’s, yet the hypothesis wasn’t abandoned. Instead cooling due to sulphate aerosols was touted as an explanation. A cue for another blog post perhaps!

Paul Biggs

It has become common practice in climate science for a press release reporting the findings of a new paper to precede the publication in the journal concerned. Thus, the Lockwood and Frohlich paper ‘Recent oppositely directed trends in solar climate forcings and the global mean surface air temperature’ (M. Lockwood and C. Fröhlich Proc. R. Soc. A doi:10.1098/rspa.2007.1880; 2007, 10th July) was announced in the 5th July edition of the journal Nature under the headline ‘No solar hiding place for greenhouse sceptics.’

It came as no surprise that Real Climate’s Stephan Rahmstorf was first out of the woodwork:

“This paper is the final nail in the coffin for people who would like to make the Sun responsible for present global warming,” says Stefan Rahmstorf, a climate scientist at the Potsdam Institute for Climate Impact Research in Germany.

Normally papers are published because there is new research to report, but not this time it seems:

Mike Lockwood, says he was “galvanized” to carry out the comprehensive study by misleading media reports. He cites ‘The Great Global Warming Swindle’, a television programme shown in March by Britain’s Channel 4, as a prime example.

But wait! There’s more:

Ken Carslaw, an atmospheric scientist at the University of Leeds, UK, points out that solar effects might still be possible. They might have acted to cool the climate in recent decades, but been overwhelmed. If so, the climate could be more sensitive to greenhouse gases than is generally thought, and future temperature increases might be greater than expected if a countervailing solar effect comes to an end.

Lockwood was “galvanised” again in response to criticism of his paper in the UK’s Daily Telegraph:

“I am one of the authors of the Royal Society global warming paper that you say is simple and fundamentally flawed (Comment, July 15). Simple? The idea was to present a straightforward demonstration, without recourse to complex climate models. Flawed? None of the three academic referees the paper was subjected to found any flaws.

Climate change is by far the greatest threat to everyone’s standard of living. Unlike political parties, companies, media stars, works of art, consumer products and even social trends and national economies, a scientific reality is immune to spin.”

(Prof) Mike Lockwood, Southampton University

Meanwhile, Piers Corbyn of Weather Action, who appeared in The Great Global Warming Swindle, had a letter published in The Guardian:

In desperate attempts to shore up their crumbling doctrine of man-made climate change, Professor Lockwood and Henry Davenport (Letters, July 14) themselves cherry-pick data. Prof Lockwood’s “refutation” of the decisive role of solar activity in driving climate is as valid as claiming a particular year was not warm by simply looking at the winter half of data. The most significant and persistent cycle of variation in the world’s temperature follows the 22-year magnetic cycle of the sun’s activity. So what does he do? He “finds” that for an 11-year stretch around 1987 to 1998 world temperatures rose, while there was a fall in his preferred measures of solar activity. A 22-year cycle and an 11-year cycle will of necessity move in opposite directions half the time.

The problem for global warmers is that there is no evidence that changing CO2 is a net driver for world climate. Feedback processes negate its potential warming effects. Their theory has no power to predict. It is faith, not science. I challenge them to issue a forecast to compete with our severe weather warnings – made months ago – for this month and August which are based on predictions of solar-particle and magnetic effects that there will be periods of major thunderstorms, hail and further flooding in Britain, most notably July 22-26, August 5-9 and August 18-23. These periods will be associated with new activity on the sun and tropical storms. We also forecast that British and world temperatures will continue to decline this year and in 2008. What do the global warmers forecast?

Piers Corbyn
Weather Action

The BBC’s verdict was ‘No Sun link’ to climate change.

In Part 2 I’ll take a closer look at some of what the L& F paper did, and didn’t say.

Check it out. It could be an interesting discussion piece.

Helen

“Dirty snow may warm Arctic as much as greenhouse gases”

Helen is referring to Black Carbon, covered by Pielke Sr recently:

A New Paper That Highlights the First-Order Radiative Forcing Of Black Carbon Deposition

Having seen Ian Mott’s note on land change, I though I would post this paper suggesting that climate models and therefore the IPCC underestimate the effects of land use change on climate:

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, D09117, doi:10.1029/2006JD007505, 2007

Observational estimates of radiative forcing due to land use change in southwest Australia

Abstract

Radiative forcing associated with land use change is largely derived from global circulation models (GCM), and the accuracy of these estimates depends on the robustness of the vegetation characterization used in the GCMs. In this study, we use observations from the Clouds and Earth’s Radiant Energy System (CERES) instrument on board the Terra satellite to report top-of-the-atmosphere (TOA) radiative forcing values associated with clearing of native vegetation for agricultural purposes in southwest Australia. Over agricultural areas, observations show consistently higher shortwave fluxes at the TOA compared to native vegetation, especially during the time period between harvest and planting. Estimates using CERES observations show that over a specific area originally covered by native vegetation, replacement of half the area by croplands results in a diurnally averaged shortwave radiative forcing of approximately −7 W m−2. GCM-derived estimates for areas with 30% or more croplands range from −1 to −2 W m−2 compared to observational estimate of −4.2 W m−2, thus significantly underestimating radiative forcing due to land use change by a factor of 2 or more. Two potential reasons for this underestimation are incorrect specification of the multiyear land use change scenario and the inaccurate prescription of seasonal cycles of crops in GCMs.

Received 12 May 2006; accepted 22 November 2006; published 15 May 2007.

Keywords: Australia; land use change; radiative forcing.

http://www.agu.org/pubs/crossref/2007/2006JD007505.shtml

I have previously posted comments about this paper, published in the Journal of Quaternary Science that provides evidence for the generally cooler period known as the Little Ice Age being a global phenomenon rather than being limited to the Northern Hemisphere:

Five centuries of climate change in Australia: the view from underground

Henry N. Pollack 1 *, Shaopeng Huang 1, Jason E. Smerdon 2
1Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, USA
2Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA

Published Online: 27 Sep 2006

Keywords
palaeoclimate • borehole temperatures • Australia

Summary and conclusions

We have analysed 57 borehole temperature profiles from across Australia to reconstruct a ground surface temperature history for the past five centuries. The five-hundred-year reconstruction is characterised by a temperature increase of approximately 0.5 K, with most of the warming occurring in the 19th and 20th centuries. The 17th century was the coolest interval of the five-century reconstruction, perhaps representing a muted expression of the Little Ice Age widely observed in the Northern Hemisphere. Because most of the boreholes were logged prior to 1976, the observed subsurface temperatures do not show the strong warming experienced by Australia in the last two decades of the 20th century. Comparison of the geothermal reconstruction to the high-quality Australian annual SAT (Surface Air Temperature) time series in their period of overlap shows excellent agreement. The full geothermal reconstruction also shows excellent agreement with the low-frequency component of dendroclimatic reconstructions from Tasmania and NewZealand. The warming of Australia over the past five centuries has been about two-thirds that experienced by southern Africa, and only about half that experienced by the continents of the Northern Hemisphere in the same time interval.

This paper provides evidence for different regional responses to global climate change and illustrates the fact that the world has warmed since the end of the LIA, with half of the warming occurring in the 20th century.