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Laschamps-ing at the bit

Filed under: — gavin @ 26 February 2021

A placeholder to provide some space to discuss the paper last week (Cooper et al, 2021) on the putative climate consequences of the Laschamps Geomagnetic Excursion, some 42,000 yrs ago.

There was some rather breathless reporting on this paper, but there were also a lot of sceptical voices – not of the main new result (a beautiful new 14C dataset from a remarkable kauri tree log found in New Zealand), but of the more speculative implications – both climatically and anthropologically.

On twitter there were some good threads covering multiple aspects of the paper (and the lead author):

But let me make a couple of different points. We have occasionally discussed the Laschamps event here as a counter-example to the notion that changes in galactic cosmic rays have a major impact on climate. A reversal or near-reversal of the geomagnetic field would be expected to greatly increase the GCR getting to the lower atmosphere – in far greater amounts than over a solar cycle, or grand solar minimum (like the Maunder Minimum). So if people want to postulate a big role for GCR there, they needed to explain why there wasn’t a much bigger signal at 42kya too. These authors are thus not the only people to have looked for significant climate impacts at this time. They are perhaps the first to claim to have found them…

To be clear, the modeling that was done in this paper was good (if extreme) and suggested that the geomagnetic event combined with a severe grand solar minimum (much bigger than the Maunder minimum) would cause significant depletion of the ozone layer and some shifts in the annular modes. But the ozone depletion is less than we’ve seen due to anthropogenic ozone depletion since the 1980s, and the surface climate changes don’t seem very significant at all – especially compared to the massive variability exhibited in the ice cores throughout the last ice age (particularly in Marine Isotope Stage 3 – the Dansgaard-Oeschgar events). At best these are nuanced and subtle climate effects, and certainly not anything apocalyptic (despite Stephen Fry’s dulcet tones).

Finally, it should be called the Laschamps event (with a final, and etymologically correct, ‘s’) after the village in the Auvergne where it was first identified. There is unfortunately 50 years of legacy references to the “Laschamp” excursion, but hopefully it isn’t too late to fix!

References

  1. A. Cooper, C.S.M. Turney, J. Palmer, A. Hogg, M. McGlone, J. Wilmshurst, A.M. Lorrey, T.J. Heaton, J.M. Russell, K. McCracken, J.G. Anet, E. Rozanov, M. Friedel, I. Suter, T. Peter, R. Muscheler, F. Adolphi, A. Dosseto, J.T. Faith, P. Fenwick, C.J. Fogwill, K. Hughen, M. Lipson, J. Liu, N. Nowaczyk, E. Rainsley, C. Bronk Ramsey, P. Sebastianelli, Y. Souilmi, J. Stevenson, Z. Thomas, R. Tobler, and R. Zech, "A global environmental crisis 42,000 years ago", Science, vol. 371, pp. 811-818, 2021. http://dx.doi.org/10.1126/science.abb8677

The NASA data conspiracy theory and the cold sun

Filed under: — stefan @ 16 January 2017

When climate deniers are desperate because the measurements don’t fit their claims, some of them take the final straw: they try to deny and discredit the data.

The years 2014 and 2015 reached new records in the global temperature, and 2016 has done so again. Some don’t like this because it doesn’t fit their political message, so they try to spread doubt about the observational records of global surface temperatures. A favorite target are the adjustments that occur as these observational records are gradually being vetted and improved by adding new data and eliminating artifacts that arise e.g. from changing measurement practices or the urban heat island effect. More about this is explained in this blog article by Victor Venema from Bonn University, a leading expert on homogenization of climate data. And of course the new paper by Hausfather et al, that made quite a bit of news recently, documents how meticulously scientists work to eliminate bias in sea surface temperature data, in this case arising from a changing proportion of ship versus buoy observations. More »

Record heat despite a cold sun

Filed under: — stefan @ 14 November 2016

Global temperature goes from heat record to heat record, yet the sun is at its dimmest for half a century.

For a while, 2010 was the hottest year on record globally. But then it got overtopped by 2014. And 2014 was beaten again by 2015. And now 2016 is so warm that it is certain to be once again a record year. Three record years in a row – that is unprecedented even in all those decades of global warming.

Strangely, one aspect of this gets barely mentioned: all those heat records occur despite a cold sun (Figs. 1 and 2). The last solar minimum (2008-2010) was the lowest since at least 1950, while the last solar maximum (2013-2015) can hardly be described as such. This is shown, among others, by the sunspot data (Fig. 1) as well as measurements of the solar luminosity from satellites (Fig. 2). Other indicators of solar activity indicate cooling as well (Lockwood and Fröhlich, Proc. Royal Society 2007).

herdsoftwidget

Fig. 1 Time evolution of global temperature, CO2 concentration and solar activity. Temperature and CO2 are scaled relative to each other according to the physically expected CO2 effect on climate (i.e. the best estimate of transient climate sensitivity). The amplitude of the solar curve is scaled to correspond to the observed correlation of solar and temperature data. (Details are explained here.) You can generate and adapt this graph to your taste here, where you can also copy a code with which the graph can be embedded as a widget on your own website (as on my home page). Thus it will be automatically updated each year with the latest data. Thanks to our reader Bernd Herd who programmed this. More »

Ice-core dating corroborates tree ring chronologies

Filed under: — group @ 5 August 2015

Guest commentary from Jonny McAneney

You heard it here first…

Back in February, we wrote a post suggesting that Greenland ice cores may have been incorrectly dated in prior to AD 1000. This was based on research by Baillie and McAneney (2015) which compared the spacing between frost ring events (physical scarring of living growth rings by prolonged sub-zero temperatures) in the bristlecone pine tree ring chronology, and spacing between prominent acids in a suite of ice cores from both Greenland and Antarctica. The main conclusion was that ice core dates, in particular those ice cores relied upon the Greenland Ice Core Chronology 2005 (GICC05), such as the NEEM S1 core, were too old by approximately seven years during the 6th and 7th centuries AD.

Last month, in an excellent piece of research (Sigl et al., 2015) by a collaboration including Earth scientists, dendrochonologists, and historians, the chronology of the Greenland North Eemian Ice Drilling core (NEEM) has been reassessed and re-dated, confirming that such an offset does indeed exist in the GICC05 timescale below AD 1000. The clinching evidence was provided by linking tree-ring chronologies to ice cores through two extraterrestrial events…
More »

References

  1. M.G.L. Baillie, and J. McAneney, "Tree ring effects and ice core acidities clarify the volcanic record of the first millennium", Climate of the Past, vol. 11, pp. 105-114, 2015. http://dx.doi.org/10.5194/cp-11-105-2015
  2. B.M. Vinther, H.B. Clausen, S.J. Johnsen, S.O. Rasmussen, K.K. Andersen, S.L. Buchardt, D. Dahl-Jensen, I.K. Seierstad, M. Siggaard-Andersen, J.P. Steffensen, A. Svensson, J. Olsen, and J. Heinemeier, "A synchronized dating of three Greenland ice cores throughout the Holocene", Journal of Geophysical Research, vol. 111, 2006. http://dx.doi.org/10.1029/2005JD006921
  3. M. Sigl, J.R. McConnell, L. Layman, O. Maselli, K. McGwire, D. Pasteris, D. Dahl-Jensen, J.P. Steffensen, B. Vinther, R. Edwards, R. Mulvaney, and S. Kipfstuhl, "A new bipolar ice core record of volcanism from WAIS Divide and NEEM and implications for climate forcing of the last 2000 years", Journal of Geophysical Research: Atmospheres, vol. 118, pp. 1151-1169, 2013. http://dx.doi.org/10.1029/2012JD018603
  4. M. Sigl, M. Winstrup, J.R. McConnell, K.C. Welten, G. Plunkett, F. Ludlow, U. Büntgen, M. Caffee, N. Chellman, D. Dahl-Jensen, H. Fischer, S. Kipfstuhl, C. Kostick, O.J. Maselli, F. Mekhaldi, R. Mulvaney, R. Muscheler, D.R. Pasteris, J.R. Pilcher, M. Salzer, S. Schüpbach, J.P. Steffensen, B.M. Vinther, and T.E. Woodruff, "Timing and climate forcing of volcanic eruptions for the past 2,500 years", Nature, vol. 523, pp. 543-549, 2015. http://dx.doi.org/10.1038/nature14565

The Soon fallacy

Filed under: — gavin @ 24 February 2015

As many will have read, there were a number of press reports (NYT, Guardian, InsideClimate) about the non-disclosure of Willie Soon’s corporate funding (from Southern Company (an energy utility), Koch Industries, etc.) when publishing results in journals that require such disclosures. There are certainly some interesting questions to be asked (by the OIG!) about adherence to the Smithsonian’s ethics policies, and the propriety of Smithsonian managers accepting soft money with non-disclosure clauses attached.

However, a valid question is whether the science that arose from these funds is any good? It’s certainly conceivable that Soon’s work was too radical for standard federal research programs and that these energy companies were really taking a chance on blue-sky high risk research that might have the potential to shake things up. In such a case, someone might be tempted to overlook the ethical lapses and conflicts of interest for the sake of scientific advancement (though far too many similar post-hoc justifications have been used to excuse horrific unethical practices for this to be remotely defendable).

Unfortunately, the evidence from the emails and the work itself completely undermines that argument because the work and the motivation behind it are based on a scientific fallacy.
More »

The most popular deceptive climate graph

Filed under: — stefan @ 8 December 2014

The “World Climate Widget” from Tony Watts’ blog is probably the most popular deceptive image among climate “skeptics”.  We’ll take it under the microscope and show what it would look like when done properly.

So called “climate skeptics” deploy an arsenal of misleading graphics, with which the human influence on the climate can be down played (here are two other  examples deconstructed at Realclimate).  The image below is especially widespread.  It is displayed on many “climate skeptic” websites and is regularly updated.

Watts_world_climate_widget

The “World Climate Widget” of US “climate skeptic” Anthony Watts with our explanations added.  The original can be found on Watts’ blog

What would a more honest display of temperature, CO2 and sunspots look like? More »

Simple physics and climate

Filed under: — rasmus @ 12 November 2013

No doubt, our climate system is complex and messy. Still, we can sometimes make some inferences about it based on well-known physical principles. Indeed, the beauty of physics is that a complex systems can be reduced into simple terms that can be quantified, and the essential aspects understood.

A recent paper by Sloan and Wolfendale (2013) provides an example where they derive a simple conceptual model of how the greenhouse effect works from first principles. They show the story behind the expression saying that a doubling in CO2 should increase the forcing by a factor of 1+log|2|/log|CO2|. I have a fondness for such simple conceptual models (e.g. I’ve made my own attempt posted at arXiv) because they provide a general picture of the essence – of course their precision is limited by their simplicity.

More »

References

  1. T. Sloan, and A.W. Wolfendale, "Cosmic rays, solar activity and the climate", Environmental Research Letters, vol. 8, pp. 045022, 2013. http://dx.doi.org/10.1088/1748-9326/8/4/045022

A review of cosmic rays and climate: a cluttered story of little success

Filed under: — rasmus @ 25 December 2012

A number of blogs were excited after having leaked the second-order draft of IPCC document, which they interpreted as a “game-changing admission of enhanced solar forcing”.

However, little evidence remains for a link between galactic cosmic rays (GCR) and variations in Earth’s cloudiness. Laken et al. (2012) recently provided an extensive review of the study of the GCR and Earth’s climate, from the initial work by Ney (1959) to the latest findings from 2012.

More »

References

  1. B.A. Laken, E. Pallé, J. Čalogović, and E.M. Dunne, "A cosmic ray-climate link and cloud observations", Journal of Space Weather and Space Climate, vol. 2, pp. A18, 2012. http://dx.doi.org/10.1051/swsc/2012018

Curve-fitting and natural cycles: The best part

Filed under: — rasmus @ 15 December 2011


It is not every day that I come across a scientific publication that so totally goes against my perception of what science is all about. Humlum et al., 2011 present a study in the journal Global and Planetary Change, claiming that most of the temperature changes that we have seen so far are due to natural cycles.

They claim to present a new technique to identify the character of natural climate variations, and from this, to produce a testable forecast of future climate. They project that

the observed late 20th century warming in Svalbard is not going to continue for the next 20–25 years. Instead the period of warming may be followed by variable, but generally not higher temperatures for at least the next 20–25 years.

However, their claims of novelty are overblown, and their projection is demonstrably unsound.

More »

References

  1. O. Humlum, J. Solheim, and K. Stordahl, "Identifying natural contributions to late Holocene climate change", Global and Planetary Change, vol. 79, pp. 145-156, 2011. http://dx.doi.org/10.1016/j.gloplacha.2011.09.005

AGU 2011: Day 2

Filed under: — group @ 7 December 2011

(Day 1)

Tuesday


There were two interesting themes in the solar sessions this morning. The first was a really positive story about how instrumental differences between rival (and highly competitive) teams can get resolved. This refers to the calibration of measurements of the Total Solar Irradiance (TSI). As is relatively well known, the different satellite instruments over the last 30 or so years have shown a good coherence of variability – especially the solar cycle, but have differed markedly on the absolute value of the TSI (see the figure). In particular, four currently flying instruments (SORCE, ACRIM3, VIRGO and PREMOS) had offsets as large as 5W/m2. However, the development of a test-facility at NASA Langley the
University of Colorado, Laboratory for Atmospheric and Space Physics in Boulder
Colorado – an effort led by Greg Kopp’s group – has allowed people to test their instruments in a vacuum, with light levels comparable to the solar irradiance, and have the results compared to really high precision measurements. This was a tremendous technical challenge, but as Kopp stated, getting everyone on board was perhaps a larger social challenge.

The facility has enabled the different instrument teams to calibrate their instruments, and check for uncorrected errors, like excessive scattering and diffusive light contamination in the measurement chambers. In doing so, Richard Wilson of the ACRIM group reported that they found higher levels of scattering than they had anticipated, which was leading to slightly excessive readings. Combined with a full implementation of an annually varying temperature correction, their latest processed data product has reduced the discrepancy with the TIM instrument from over 5 W/m2 to less than 0.5 W/m2 – a huge improvement. The new PREMOS instrument onboard Picard, a french satellite, was also tested before launch last year, and they improved their calibration as well – and the data that they reported was also very close to the SORCE/TIM data: around 1361 W/m2 at solar minimum.

The errors uncovered and the uncertainties reduced as a function of this process was a great testament to the desire of everyone concerned to work towards finding the right answer – despite initial assumptions about who may have had the best design. The answer is that space borne instrumentation is hard to do, and thinking of everything that might go wrong is a real challenge.

The other theme was the discussion of the spectral irradiance changes – specifically by how much the UV changes over a solar cycle are larger in magnitude than the changes in the total irradiance. The SIM/SOLSTICE instruments on SORCE have reported much larger UV changes than previous estimates, and this has been widely questioned (see here for a previous discussion). The reason for the unease is that the UV instruments have a very large degradation of their signal over time, and the residual trends are quite sensitive to the large corrections that need to be made. Jerry Harder discussed those corrections and defended the SIM published data, while another speaker made clear how anomalous that data was. Meanwhile, some climate modellers are already using the SIM data to see whether that improves the model simulations of ozone and temperature responses in the stratosphere. However, the ‘observed’ data on this is itself somewhat uncertain – for instance, comparing the SAGE results (reported in Gray et al, 2011) with the SABER results (Merkel et al, 2011), shows a big difference in how large the ozone response is. So this remains a bit of a stumper.

The afternoon sessions on water isotopes in precipitation was quite exciting because of the number of people looking at innovative proxy archives, including cave records of 18O in calcite, or deuterium in leaf waxes, which are extending the coverage (in time and space) of this variable. Even more notable, was the number of these presentations that combined their data work with interpretations driven by GCM models that include isotope tracers that allow for more nuanced conclusions. This is an approach that was pioneered decades ago, but has taken a while to really get used routinely.

(Days 3&4)(Day 5 and wrap up)

References

  1. L.J. Gray, J. Beer, M. Geller, J.D. Haigh, M. Lockwood, K. Matthes, U. Cubasch, D. Fleitmann, G. Harrison, L. Hood, J. Luterbacher, G.A. Meehl, D. Shindell, B. van Geel, and W. White, "SOLAR INFLUENCES ON CLIMATE", Reviews of Geophysics, vol. 48, 2010. http://dx.doi.org/10.1029/2009RG000282
  2. A.W. Merkel, J.W. Harder, D.R. Marsh, A.K. Smith, J.M. Fontenla, and T.N. Woods, "The impact of solar spectral irradiance variability on middle atmospheric ozone", Geophysical Research Letters, vol. 38, pp. n/a-n/a, 2011. http://dx.doi.org/10.1029/2011GL047561
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