A stellar revision of the story of life

Climate Change: News and Comments and The Svensmark Hypothesis

Svensmark’s Cosmic Jackpot

Visible to the naked eye as the Seven Sisters, the Pleiades are the most famous of many surviving clusters of stars that formed together at the same time. The Pleiades were born during the time of the dinosaurs, and the most massive of the siblings would have exploded over a period of 40 million years. Their supernova remnants generated cosmic rays. From the catalogue of known star clusters, Henrik Svensmark has calculated the variation in cosmic rays over the past 500 million years, without needing to know the precise shape of the Milky Way Galaxy. Armed with that astronomical history, he digs deep into the histories of the climate and of life on Earth. Image ESA/NASA/Hubble

Today the Royal Astronomical Society in London publishes (online) Henrik Svensmark’s latest paper entitled “Evidence of nearby supernovae affecting life on Earth”. After years of effort Svensmark shows how the variable frequency of stellar explosions not far from our planet has ruled over the changing fortunes of living things throughout the past half billion years. Appearing in Monthly Notices of the Royal Astronomical Society, It’s a giant of a paper, with 22 figures, 30 equations and about 15,000 words. See the RAS press release athttp://www.ras.org.uk/news-and-press/219-news-2012/2117-did-exploding-stars-help-life-on-earth-to-thrive

By taking me back to when I reported the victory of the pioneers of plate tectonics in their battle against the most eminent geophysicists of the day, it makes me feel 40 years younger. Shredding the textbooks, Tuzo Wilson, Dan McKenzie and Jason Morgan merrily explained earthquakes, volcanoes, mountain-building, and even the varying depth of the ocean, simply by the drift of fragments of the lithosphere in various directions around the globe.

In Svensmark’s new paper an equally concise theory, that cosmic rays from exploded stars cool the world by increasing the cloud cover, leads to amazing explanations, not least for why evolution sometimes was rampant and sometimes faltered. In both senses of the word, this is a stellar revision of the story of life.

Here are the main results:

The long-term diversity of life in the sea depends on the sea-level set by plate tectonics and the local supernova rate set by the astrophysics, and on virtually nothing else.

The long-term primary productivity of life in the sea – the net growth of photosynthetic microbes – depends on the supernova rate, and on virtually nothing else.

Exceptionally close supernovae account for short-lived falls in sea-level during the past 500 million years, long-known to geophysicists but never convincingly explained..

As the geological and astronomical records converge, the match between climate and supernova rates gets better and better, with high rates bringing icy times.

Presented with due caution as well as with consideration for the feelings of experts in several fields of research, a story unfolds in which everything meshes like well-made clockwork. Anyone who wishes to pooh-pooh any piece of it by saying “correlation is not necessarily causality” should offer some other mega-theory that says why several mutually supportive coincidences arise between events in our galactic neighbourhood and living conditions on the Earth.

An amusing point is that Svensmark stands the currently popular carbon dioxide story on its head. Some geoscientists want to blame the drastic alternations of hot and icy conditions during the past 500 million years on increases and decreases in carbon dioxide, which they explain in intricate ways. For Svensmark, the changes driven by the stars govern the amount of carbon dioxide in the air. Climate and life control CO2, not the other way around.

By implication, supernovae also determine the amount of oxygen available for animals like you and me to breathe. So the inherently simple cosmic-ray/cloud hypothesis now has far-reaching consequences, which I’ve tried to sum up in this diagram.

Cosmic rays in action. The main findings in the new Svensmark paper concern the uppermost stellar band, the green band of living things and, on the right, atmospheric chemistry. Although solar modulation of galactic cosmic rays is important to us on short timescales, its effects are smaller and briefer than the major long-term changes controlled by the rate of formation of big stars in our vicinity, and their self-destruction as supernovae. Although copyrighted, this figure may be reproduced with due acknowledgement in the context of Henrik Svensmark's work.

By way of explanation

The text of “Evidence of nearby supernovae affecting life on Earth” is available via  ftp://ftp2.space.dtu.dk/pub/Svensmark/MNRAS_Svensmark2012.pdf The paper is highly technical, as befits a professional journal, so to non-expert eyes even the illustrations may be a little puzzling. So I’ve enlisted the aid of Liz Calder to explain the way one of the most striking graphs, Svensmark’s Figure 20, was put together. That graph shows how, over the past 440 million years, the changing rates of supernova explosions relatively close to the Earth have strongly influenced the biodiversity of marine invertebrate animals, from trilobites of ancient times to lobsters of today. Svensmark’s published caption ends: “Evidently marine biodiversity is largely explained by a combination of sea-level and astrophysical activity.” To follow his argument you need to see how Figure 20 draws on information in Figure 19. That tells of the total diversity of the sea creatures in the fossil record, fluctuating between times of rapid evolution and times of recession.

The count is by genera, which are groups of similar animals. Here it’s shown freehand by Liz in Sketch A. Sketch B is from another part of Figure 19, telling how the long-term global sea-level changed during the same period. The broad correspondence isn’t surprising because a high sea-level floods continental margins and gives the marine invertebrates more extensive and varied habitats. But it obviously isn’t the whole story. For a start, there’s a conspicuous spike in diversity about 270 million years ago that contradicts the declining sea-level. Svensmark knew that there was a strong peak in the supernova rate around that time. So he looked to see what would happen to the wiggles over the whole 440 million years if he “normalized” the biodiversity to remove the influence of sea-level. That simple operation is shown in Sketch C, where the 270-million-year spike becomes broader and taller. Sketch D shows Svensmark’s reckoning of the changing rates of nearby supernovae during the same period. Let me stress that these are all freehand sketches to explain the operations, not to convey the data. In the published paper, the graphs as in C and D are drawn precisely and superimposed for comparison.

This is Svensmark's Figure 20, with axes re-labelled with simpler words for the RAS press release. Biodiversity (the normalized marine invertebrate genera count) is in blue, with vertical bars indicating possible errors. The supernova rates are in black.

There are many fascinating particulars that I might use to illustrate the significance of Svensmark’s findings. To choose the Gorgon’s story that follows is not entirely arbitrary, because this brings in another of those top results, about supernovae and bio-productivity.

The great dying at the end of the Permian

Out of breath, poor gorgon? Gasping for some supernovae? Named after scary creatures of Greek myth, the Gorgonopsia of the Late Permian Period included this fossil species Sauroctonus progressus, 3 metres long. Like many of its therapsid cousins, near relatives of our own ancestors, it died out during the Permo-Triassic Event. Source: http://en.wikipedia.org/wiki/Gorgonopsia

Luckiest among our ancestors was a mammal-like reptile, or therapsid, that scraped through the Permo-Triassic Event, the worst catastrophe in the history of animal life. The climax was 251 million years ago at the end of the Permian Period. Nearly all animal species in the sea went extinct, along with most on land. The event ended the era of “old life”, the Palaeozoic, and ushered in the Mesozoic Era, when our ancestors would become small mammals trying to keep clear of the dinosaurs. So what put to death our previously flourishing Gorgon-faced cousins of the Late Permian? According to Henrik Svensmark, the Galaxy let the reptiles down.

Forget old suggestions (by myself included) that the impact of a comet or asteroid was to blame, like the one that did for the dinosaurs at the end of the Mesozoic. The greatest dying was less sudden than that. Similarly the impressive evidence for an eruption 250 million years ago – a flood basalt event that smothered Siberia with noxious volcanic rocks covering an area half the size of Australia – tells of only a belated regional coup de grâce. It’s more to the point that oxygen was in short supply – geologists speak of a “superanoxic ocean”. And there was far more carbon dioxide in the air than there is now.

“Well there you go,” some people will say. “We told you CO2 is bad for you.” That, of course, overlooks the fact that the notorious gas keeps us alive. The recently increased CO2 shares with the plant breeders the credit for feeding the growing human population. Plants and photosynthetic microbes covet CO2 to grow. So in the late Permian its high concentration was a symptom of a big shortfall in life’s productivity, due to few supernovae, ice-free conditions, and a lack of weather to circulate the nutrients. And as photosynthesis is also badly needed to turn H2O into O2, the doomed animals were left gasping for oxygen, with little more than half of what we’re lucky to breathe today.

When Svensmark comments briefly on the Permo-Triassic Event in his new paper, “Evidence of nearby supernovae affecting life on Earth,” he does so in the context of the finding that high rates of nearby supernovae promote life’s productivity by chilling the planet, and so improving the circulation of nutrients needed by the photosynthetic organisms.Here’s a sketch from Figure 22 in the paper, simplified to make it easier to read. Heavy carbon, ¹³C, is an indicator of how much photosynthesis was going on. Plumb in the middle is a downward pointing green dagger that marks the Permo-Triassic Event. And in the local supernova rate (black curve) Svensmark notes that the Late Permian saw the largest fall in the local supernova rate seen in the past 500 million years. This was when the Solar System had left the hyperactive Norma Arm of the Milky Way Galaxy behind it and entered the quiet space beyond. “Fatal consequences would ensue for marine life,” Svensmark writes, “if a rapid warming led to nutrient exhaustion … occurring too quickly for species to adapt.”

One size doesn’t fit all, and a fuller story of Late Permian biodiversity becomes subtler and even more persuasive. About 6 million years before the culminating mass extinction of 251 million years ago, a lesser one occurred at the end of the Guadalupian stage. This earlier extinction was linked with a brief resurgence in the supernova rate and a global cooling that interrupted the mid-Permian warming. In contrast with the end of the Permian, bio-productivity was high. The chief victims of this die-off were warm-water creatures including gigantic bivalves and rugose corals.

Why it’s tagged as “astrobiology”

So what, you may wonder, is the most life-enhancing supernova rate? Without wanting to sound like Voltaire’s Dr Pangloss, it’s probably not very far from the average rate for the past few hundred million years, nor very different from what we have now. Biodiversity and bio-productivity are both generous at present.

Svensmark has commented (not in the paper itself) on a closely related question – where’s the best place to live in the Galaxy?

“Too many supernovae can threaten life with extinction. Although they came before the time range of the present paper, very severe episodes called Snowball Earth have been blamed on bursts of rapid star formation. I’ve tagged the paper as ‘Astrobiology’ because we may be very lucky in our location in the Galaxy. Other regions may be inhospitable for advanced forms of life because of too many supernovae or too few.”

Astronomers searching for life elsewhere speak of a Goldilocks Zone in planetary systems. A planet fit for life should be neither too near to nor too far from the parent star. We’re there in the Solar System, sure enough. We may also be in a similar Goldilocks Zone of the Milky Way, and other galaxies with too many or too few supernovae may be unfit for life. Add to that the huge planetary collision that created the Earth’s disproportionately large Moon and provided the orbital stability and active geology on which life relies, and you may suspect that, astronomically at least, Dr Pangloss was right — “Everything is for the best in the best of all possible worlds.”

Don’t fret about the diehards

If this blog has sometimes seemed too cocky about the Svensmark hypothesis, it’s because I’ve known what was in the pipeline, from theories, observations and experiments, long before publication. Since 1996 the hypothesis has brought new successes year by year and has resisted umpteen attempts to falsify it.

New additions at the level of microphysics include a previously unknown reaction of sulphuric acid, as in a recent preprint. On a vastly different scale, Svensmark’s present supernova paper gives us better knowledge of the shape of the Milky Way Galaxy.

A mark of a good hypothesis is that it looks better and better as time passes. With the triumph of plate tectonics, diehard opponents were left redfaced and blustering. In 1960 you’d not get a job in an American geology department if you believed in continental drift, but by 1970 you’d not get the job if you didn’t. That’s what a paradigm shift means in practice and it will happen sometime soon with cosmic rays in climate physics.

Plate tectonics was never much of a political issue, except in the Communist bloc. There, the immobility of continents was doctrinally imposed by the Soviet Academy of Sciences. An analagous diehard doctrine in climate physics went global two decades ago, when the Intergovernmental Panel on Climate Change was conceived to insist that natural causes of climate change are minor compared with human impacts.

Don’t fret about the diehards. The glory of empirical science is this: no matter how many years, decades, or sometimes centuries it may take, in the end the story will come out right.

Roll up, roll up, for the paradigm shift

Climate Change News and Comments

The dawn of the cosmic ray era in climate science?

Roy Spencer, formerly of NASA, is an outstanding investigator of climate change using satellites. Yesterday he posted on his website this article about cosmic rays: http://www.drroyspencer.com/2011/05/indirect-solar-forcing-of-climate-by-galactic-cosmic-rays-an-observational-estimate/ It starts:

“While I have been skeptical of Svensmark’s cosmic ray theory up until now, it looks like the evidence is becoming too strong for me to ignore.” And he concludes:

“The results, I must admit, are enough for me to now place at least one foot solidly in the cosmic ray theory camp.”

One swallow doesn’t make a summer, nor one Spencer a scientific revolution. But as I recall real revolutions during my lifetime as a science reporter – black holes, plate tectonics, etc, etc. — I recognise this as a sample of what a paradigm shift looks like. One by one, prominent experts and daring young researchers begin to join a new club. At first they’re counted on fingers, but eventually by faculties.

“Consensus” is a dirty word for climate sceptics, because of its misuse for 20 years by warmist scientists and their political and journalistic chums to try to stifle research and public debate. In that regard, the lack of agreement among sceptical physicists about what’s really going on has been virtuous. But the time for free-ranging and competitive hypotheses about natural climate change is drawing to an end. Some widely accepted theory of the mechanisms has to replace the computer games of the Intergovernmental Panel on Climate Change.

Since Henrik Svensmark explained his hypothesis concerning cosmic rays and clouds, over a lunch of marinated herrings and lager in Copenhagen in 1996, I’ve written two books about it and helped Lars Oxfeldt Mortensen with TV films featuring Henrik. But the three of us have now waited 15 years for some kind of denouement. Ten to twenty years is a typical timescale for a paradigm shift, so maybe Henrik’s breakthrough is coming at last.

Sun still sulks

Pick of the pics and Climate Change: News and Comments

The Sun still sulks

Two magnetograms from the ESA-NASA SOHO spacecraft contrast the Sun’s liveliness of exactly 10 years ago (20 June 2000) on the left with its feeble performance today (20 June 2010) on the right. In these images made with Stanford’s Michelson Doppler Interferometer, north magnetic polarity is white, south magnetic polarity is black.

Solstice sunrise over Stonehenge 2005. Credit: User: Solipsist.

As many thousands flock to Stonehenge for tomorrow’s summer solstice, this is a moment to ask for the umpteenth time what the Sun is up to. The mean sunspot number in June 2000 was 119, today it is 28, with the spots clustered in the northern region showing most magnetic activity. Since 2004 there have been 803 days with no sunspots at all (35 in 2010, 260 in 2009). During a typical sunspot minimum there are fewer than 500 spotless days.

In the current issue of the Royal Astronomical Society’s magazine Astronomy and Geophysics, Nigel Weiss of Cambridge considers the long-term variability of the Sun and alternative theories about it, especially concerning “grand maxima” in activity like that in the 20th Century, and “grand minima” like the Maunder Minimum of 300 years ago associated with the Little Ice Age. Weiss’s conclusion is that there’s a 40 % chance the current grand maximum will be followed by a grand minimum.

As for the climatic implications, Weiss and I agreed to differ some years ago. Although we both say that the Intergovernmental Panel on Climate Change underestimates the influence of the Sun, Weiss thinks it can’t compete with man-made global warming. His article ends:

Even if the Sun does enter a new Maunder-like grand minimum, any cooling effect will be small compared with the warming produced by anthropogenic greenhouse gases.

Contrast that with Henrik Svensmark’s conclusion in an article for the Danish newspaper Jyllands-Posten.

That the Sun might now fall asleep in a deep minimum was suggested by solar scientists at a meeting in Kiruna in Sweden two years ago. So when Nigel Calder and I updated our book The Chilling Stars, we wrote a little provocatively that “we are advising our friends to enjoy global warming while it lasts.”

In fact global warming has stopped and a cooling is beginning. Mojib Latif from the University of Kiel argued at the recent UN World Climate Conference in Geneva that the cooling may continue through the next 10 to 20 years. His explanation was a natural change in the North Atlantic circulation, not in solar activity. But no matter how you interpret them, natural variations in climate are making a comeback.

The outcome may be that the Sun itself will demonstrate its importance for climate and so challenge the theories of global warming. No climate model has predicted a cooling of the Earth – quite the contrary. And this means that the projections of future climate are unreliable. A forecast saying it may be either warmer or colder for 50 years is not very useful, and science is not yet able to predict solar activity.

So in many ways we stand at a crossroads. The near future will be extremely interesting. I think it is important to accept that Nature pays no heed to what we humans think about it. Will the greenhouse theory survive a significant cooling of the Earth? Not in its current dominant form. Unfortunately, tomorrow’s climate challenges will be quite different from the greenhouse theory’s predictions. Perhaps it will become fashionable again to investigate the Sun’s impact on our climate.

References

N. Weiss, “Modulation of the Sunspot Cycle”, Astronomy and Geophysics, Vol. 51, pp. 3.9-3.15, 2010

H. Svensmark: “While the Sun sleeps” (in Danish), Jyllands-Posten, 9 September, 2009

For a related post on this blog see https://calderup.wordpress.com/2010/05/12/puzzling-sun/

Postscript on the Song of the Sun

I see that Sheffield solar physicists now generate music from observations of the magnetic coronal loops. Read about it (and hear it): http://www.telegraph.co.uk/science/space/7840201/Music-of-the-sun-recorded-by-scientists.html

For an earlier Song of the Sun, using its internal vibrations seen by SOHO’s MDI, click on the second item here (but beware – it’s about 18 MB with visuals) http://www.esa.int/esaSC/SEMLAJWO4HD_index_0.html

Soil H2O from space

Pick of the pics & Climate Change: News and Comments

Soil moisture around the Amazon, gauged from space

A plot of microwave “brightness temperatures” measures the water content of the soil around the lower Amazon. This is an early result from Europe's Soil Moisture and Ocean Salinity satellite, SMOS, launched in November 2009 and formally operational since late May 2010. It's a sample of what is now becoming available globally every 3 days, and SMOS should help to fill a huge gap in human knowledge of the water cycle. Credit: ESA/SMOS.

Despite repeated claims that the weather system is known well enough for making multi-decade forecasts of the changing climate, the ignorance can be truly profound. The global water cycle is a key theme where understanding is poor and reliable data are notoriously scanty. The Intergovernmental Panel on Climate Change avoids forthright language that might dismay those who want to treat its findings as gospel, yet in relevant parts of Working Group I’s 2007 report there are hints of desperation. See Section 3.3: “Changes in Surface Climate: Precipitation, Drought and Surface Hydrology”, available here: http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch3s3-3.html

Soil moisture is crucial

• as a climate factor in its own right, vital for natural and cultivated plant growth, and for the management of water resources
• as a strong influence on the global carbon cycle by its contribution to terrestrial photosynthesis
• as a way station in the hydrological system’s non-stop traffic between rainfall, evaporation, transpiration from plants, and run-off into streams and rivers.

If you want ever to model the water cycle accurately, you really must know the soil moisture content. The European Space Agency claims for SMOS an accuracy of 4%, “comparable to detecting one teaspoon of water mixed into a handful of soil” from an altitude of 760 km. A calculation gives the water content in soil to a depth of 1-2 metres – the root zone.

How’s it done? The presence of water affects the electromagnetic behaviour of soil, and hence the intensity of radio microwaves that it radiates. But the long wavelength, about 20 cm, of the most useful microwaves implies that you need a large radio telescope in space to observe them well.

SMOS, pictured by ESA

The L-band radiometer on SMOS, called MIRAS, uses the radio astronomers’ technique of aperture synthesis. It simulates a much bigger antenna with 69 small antennas strung out along three arms arranged in a Y, and so resolves areas 50 km wide within a hexagon on the Earth’s surface about 1000 km across.

The same instrument on SMOS gauges the saltiness of sea water, using the electromagnetic contrast between pure water and salty water – hence “Ocean Salinity” in the mission’s name. But that’s another story.

Good luck to mission manager Susanne Mecklenburg, mission scientist Matthias Drusch, and all the SMOS team.

Climate Change intro

CLIMATE CHANGE – Introduction

This section of Calder’s Updates is unavoidably a battleground, but within reason it will stick to the physics and dodge the propaganda that surrounds climate research.

Headings in this section

• News and Comments watching developments
• The Svensmark Hypothesis outlining the science
• Falsification Tests digging deeper into the physics
• Updating The Chilling Stars with evolving stories

In 1997 The Manic Sun by Nigel Calder was the first book to describe a new wonder of Nature – namely Henrik Svensmark’s discovery that the effect of cosmic rays on clouds amplifies the influence of the Sun on the Earth’s climate. Ten years of progress with the physics led to a second book The Chilling Stars in 2007, co-authored with Svensmark.I was also a script consultant to Mortensen Film for the TV programme about Svensmark’s work, “The Cloud Mystery”.

Despite plenty of time to re-consider the story, if it had turned out to be foolish, the evidence looks better and better as the years pass. Yet most climate scientists still ignore or reject Svensmark’s findings from observations of the real world, physics experiments, and theoretical analyses. Scoffing or vehement objections come from supporters of the man-made global warming hypothesis, who realise that the Svensmark hypothesis offers the strongest challenge to the assumptions in their climate models that predict climatic catastrophe.

The customary give-and-take arguments among experts, about which scientific theory fits the facts better, would be fair enough. But since climate physics became a political issue, the involvement of governments, funding agencies, scientific journals and the media in propagating a particular view of climate change has made rational debate difficult. Here’s a comment from Svensmark in an interview by Discover magazine, July 2007.

Question: In 1996, when you reported that changes in the Sun’s activity could explain most or all of the recent rise in Earth’s temperature, the chairman of the United Nations Intergovernmental Panel [on Climate Change] called your announcement “extremely naive and irresponsible”. How did you react?

Svensmark: I was just stunned. I remember being shocked by how many thought what I was doing was terrible. I couldn’t understand it because when you are a physicist, you are trained that when you find something that cannot be explained, something that doesn’t fit, that is what you are excited about. If there is a possibility that you might have an explanation, that is something that everybody thinks is what you should pursue. Here was exactly the opposite reaction. It was as though people were saying to me, “This is something that you should not have done.” That was very strange for me, and it has been more or less like that ever since.

To me (Calder) as a reporter of major discoveries that went on to win Nobel prizes in several different fields, the contrast between flimsy conjecture and creative brainpower backed by real evidence is fairly obvious. Being a generalist, rather than a specialist reporter of climate science, also helps to keep me objective, but I’m not inexperienced or ignorant in this field. It can be irritating when “warmist” journalists and campaigners with no relevant training of their own try to question my competence. Hey, I’ve even published a couple of formal scientific papers of my own.

Calder’s writing and editing on climate-related subjects

2007 (updated 2008) book: The Chilling Stars: A New Theory of Climate Change. Joint author with Henrik Svensmark

2003 book: Magic Universe: The Oxford Guide to Modern Science. Topics Include Biosphere from space, Carbon cycle, Climate change, Cosmic rays, Cryosphere, Earthshine, Earth system, El Niño, Ocean currents, Solar wind, and Volcanic explosions

1999 scientific paper: ‘The Carbon Dioxide Thermometer’, Energy & Environment, 1999, Vol. 10, pp. 1-18, on how CO₂ seems to respond to climate change rather than the other way around.

1997 book: The Manic Sun: Weather Theories Confounded about the Sun & climate, including Svensmark’s initial discovery about cosmic rays and clouds

1991 book and related TV series: Spaceship Earth about Earth observation, Including space observations of clouds, storms, temperatures, ice, oceans, bioproductivity, land use, and deforestation.

1990 book: Scientific Europe (editor, for Foundation Scientific Europe). It includes climate articles by Hermann Flohn, Bert Bolin, Paul Crutzen, and Lennart Bengtsson.

1983 book: Timescale: An Atlas of the Fourth Dimension. Among many other topics it traces climate change from the first ice ages 2300 million years ago to the Little Ice Age ending in 1850.

1974 book and related 2-hour TV programme: The Weather Machine. These included the first public reports of the confirmation of the Milankovitch ice-age hypothesis. Participants on TV include Hubert Lamb, Nicholas Shackleton, John Imbrie, Willi Dansgaard, George Kukla, Syukuro Manabe and Bert Bolin.

1974 scientific paper: ‘The Arithmetic of Ice Ages’, Nature, Vol. 252, pp. 216-18, with the first formal confirmation of the Milankovitch Effect. (Done with a pocket calculator, to legitimize what we were saying in The Weather Machine.)

1973 book: Nature in the Round: A Guide to Environmental Science (editor). Includes articles on climate change by L.P. Smith and Grahame Clark.

1968 book: Unless Peace Comes (editor). Includes Gordon MacDonald on weather and climate modification as weapons of war

1965 book: The World in 1984 (editor, for New Scientist). Among about 100 commissioned 20-yr forecasts, contributions on weather & climate came from Graham Sutton, Fred Singer, D.A. Davies & Roger Revelle

Calder has often spoken about climate change in lectures and on TV and radio, including an interview (2007) for The Great Global Warming Swindle, WagTV’s production for Channel 4. He has published articles on the subject since 1961.