Fears of Freezing: The 1970s are calling; They want their climate policies back

August 26, 2014 12:13 pm3 comments

A top economic advisor to the Australian Government recently suggested in an op-ed published by the national daily The Australian that one scenario we should be prepared for is global cooling due to a possible change in solar activity. Certain reports in the U.S. media have also suggested cooling may already be upon us because of the sun. What is one to make of this?

Should we be prepared for global cooling driven by changes in solar output?

Dr. Will Howard

Dr. Will Howard

There is much to be learned about the sun’s role in climate. However, best estimates suggest the sun’s variability over recent decades has played a small role in observed climate change] (footnote 1). Though it is still difficult to predict changes in the sun, modeled projections suggest even a return to the “Maunder Minimum” (footnote 2) would provide only minor compensation for anticipated greenhouse-gas warming.

The attention on the sun serves as a reminder that modern climate science arose, in part, from efforts to address societal concerns over global cooling, setting the stage for advances in climate science over the past forty years. There was concern among some policy makers that the decades of cooling from the mid-1940s through the mid 1970’s represented the onset of a new ice age.

In the 1970s the Little Ice Age, and the “Year Without a Summer” following the 1815 Tambora eruption, were known. So the dangers of a cold climate were perhaps more current in peoples’ minds than the dangers of warming, and historically people have been more worried about being too cold than too warm. 
The idea of an impending ice age did feature in some media pieces.

Ice Age

Headline from the Melbourne Age, February 16, 1979.

The role of the earth’s orbit in climate (footnote 3) was being confirmed. These long-term changes in the distribution of solar radiation over the seasons and latitudes were discovered to be imprinted upon the record of climate, leading to the suggestion that, all else being equal, the earth might be headed towards an ice age. Some scientists did suggest another ice age might be on the way (footnote 4), but it was not clear when. It was known by then the earth was in an “interglacial” stage, and these warm stages were relatively short excursions in the generally cool Pleistocene epoch (footnote 5).

Another “cold climate” worry came from the fear of “nuclear winter,” and also drove the development of climate models.

All these concerns drove an examination of scientific understanding about climate in the 1970s. The scientific community said they were not in a position to confidently predict which way climate would go from that point. Would the long slow orbital changes plus anthropogenic aerosol emissions cool the planet? Or would greenhouse gases become the dominant forcing? [See Spencer Weart’s “The Discovery of Global Warming” for a thorough and comprehensive treatment of the history of climate science.]

A 1975 U.S. National Academy of Sciences report on climate change is blunt about the state of understanding of the climate system at the time:

“We do not have a good quantitative understanding of our climate machine and what determines its course. Without the fundamental understanding, it does not seem possible to predict climate. … The climates of the earth have always been changing, and they will doubtless continue to do so in the future. How large these future changes will be, and where and how rapidly they will occur, we do not know.”

The report also notes that:

“There seems little doubt that the present period of unusual warmth will eventually give way to a time of colder climate, but there is no consensus with regard to either the magnitude or rapidity of the transition. The onset of this climatic decline [i.e. cooling] could be several thousand years in the future, although there is a finite probability that a serious worldwide cooling could befall the earth within the next hundred years.”

Some commentators have seized upon statements like the latter as evidence there was a “consensus” among scientists about a coming ice age. But actually there was not a clear sense which way the climate would go in the coming decades. Climate scientists were already aware of the potential of global warming from carbon dioxide emissions, but when and by how much would their influence be felt?

A report to the US Johnson Administration in 1965 (footnote 6) is prescient, and predicts correctly, a rise in the CO2 concentration of the atmosphere. It also anticipates some of the effects of that rise, including warming of the atmosphere and ocean, sea-level rise, and melting of ice caps. The authors also envision the possibility of deliberate manipulation of the climate system, what we would now call “geoengineering“:

“The climatic changes that may be produced by the increased CO2 content could be deleterious from the point of view of human beings. The possibilities of deliberately bringing about countervailing climatic change therefore need to be thoroughly explored.”

In 1975 paleoclimatologist Wally Broecker (also an author of the NAS report) made a bold prediction of warming (footnote 7):

“… a strong case can be made that the present cooling trend will, within a decade or so, give way to a pronounced warming induced by carbon dioxide. By analogy with similar events in the past, the natural climatic cooling which, since 1940, has more than compensated for the carbon dioxide effect, will soon bottom out. Once this happens, the exponential rise in the atmospheric carbon dioxide content will tend to become a significant factor and by early in the next century will have driven the mean planetary temperature beyond the limits experienced during the last 1000 years.”

Broecker predicted that by 2010 global temperatures would have risen 1.1 C (above a late 19th Century baseline) and atmospheric CO2 content would be at 403 ppm. Not bad.

Pioneers like Svante Arrhenius in the late 1800’s and Mikhail Budyko (footnote 8) in the 1960s had already anticipated the warming effect of greenhouse gases, though they saw global warming as beneficial.

Climate science has evolved. We now see the warming effects of accumulating greenhouse gases as a greater risk than global cooling. We also recognize a broader spectrum of impacts than warming alone, such as the acidification of the ocean due to its absorption of CO2.

New studies of climate variability have provided timely reminders that we need to be able to adapt to climate changes, no matter what drives them.

Footnotes:

1. Lean, J. L. (2010), Cycles and trends in solar irradiance and climate, Wiley Interdisciplinary Reviews: Climate Change, 1(1), 111-122, doi:10.1002/wcc.18.

2. A 17th Century low in solar activity associated with the “Little Ice Age;” Feulner, G., and S. Rahmstorf (2010), On the effect of a new grand minimum of solar activity on the future climate on Earth, Geophys. Res. Lett., 37(5), L05707, doi:10.1029/2010gl042710.

3. Hays, J. D., J. Imbrie, and N. J. Shackleton (1976), Variations in the Earth’s orbit: Pacemaker of the ice ages, Science, 194(4270), 1121-1132, doi:10.1126/science.194.4270.1121.

4. Kukla, G. J., and R. K. Matthews (1972), When Will the Present Interglacial End?, Science, 178(4057), 190-202, doi:10.1126/science.178.4057.190.

5. Tzedakis, P. C., E. W. Wolff, L. C. Skinner, V. Brovkin, D. A. Hodell, J. F. McManus, and D. Raynaud (2012), Can we predict the duration of an interglacial?, Clim. Past, 8(5), 1473-1485, doi:10.5194/cp-8-1473-2012.

6. Environmental Pollution Panel (1965), Restoring the Quality of Our Environment, 133 pp, President’s Science Advisory Committee, Washington D.C..

7. Broecker, W. S. (1975), Are We on the Brink of a Pronounced Global Warming?, Science, 189(4201), 460-463, doi:10.1126/science.189.4201.460.

8. Budyko, M. I. (1969), The effect of solar radiation variations on the climate of the Earth, Tellus, 21(5), 611-619, doi:10.1111/j.2153-3490.1969.tb00466.x.

 

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THE FORUM'S COMMENT THREAD

  • In the 1970s, the first comprehensive analysis of oxygen isotopes in sediments from cores taken from the sea floor established for the first time that the timing of the Ice Ages was linked to subtle changes in the Earth’s orbit around the Sun as suggested long ago by Serbian mathematician Milutin Milankovitch. In the context of orbital changes with cycles of tens to hundreds of thousands of years, this meant that IF ALL ELSE REMAINED CONSTANT, Earth’s climate would inevitably cool toward another Ice Age over the next 100,000 years or so.

    This is still true, but 100,000 years is a very long time. Note that it’s not at all inconsistent to expect very rapid warming over the next 300 years and still be at the beginning of a 100,000 year cooling trend due to orbital variations.

    More to the point, we know quite well, just as we did in the 1970’s that ALL ELSE IS NOT CONSTANT. In particular, we know that the rapid economic development in China and (soon) India will create an enormous increase int eh demand for energy, and that if this demand is met primarily through combustion of carbon that atmospheric CO2 will rise to between 3 and 4 times preindustrial concentrations. And we know in great quantitative detail how many Watts of outgoing heat this extra CO2 will absorb. And we know much better now than we did 40 years ago how sensitive the Earth’s climate is to each Watt of absorbed heat.

    The ironic thing is that the huge climate swings (Ice Ages) associated with subtle changes in Earth’s orbit are the strongest evidence we have of the sensitive of Earth’s climate in degrees per Watt. The fact that the ice melted at the end of the last Ice Age shows that if China and India industrialize with coal, the Earth’s climate will warm a similar amount in response. After all, a Watt of extra heat from CO2 is the same as a Watt of extra heat from the Sun.

    The fact of previous climate change due to “natural cycles” is probably the strongest evidence we have that adding the same amount of heat will warm future climate about as much as the warming following the last Ice Age. The difference is that 5 Celsius of global warming after the last Ice Age took about 10,000 years, whereas politicians’ Plan A is to add the same amount of heat over the next couple of centuries.

    The great irony is that politicians and their cheerleaders (see Dr J on here) don’t even understand the fundamental logical contradiction of their positions. The arrogance of big government indeed!

    • Scott, your comments are very pertinent. And perhaps an expanded future post could explore this issue in more detail.

      Some cite the Quaternary climate cycles as an example of “this has all happened before.” The “logical contradiction” is that these cycles are a source of our understanding of the role of greenhouse gases as powerful feedbacks, and of other feedback processes (e.g. albedo, among other short- and long-time scale processes) that mediate subtle changes in the distribution of incoming solar radiation into large-scale climate changes. Our emissions of GHGs are taking what likely operated as a feedback during the Quaternary cycles and making it a primary forcing of the Earth’s radiative balance (or imbalance in this case).

      There is often misunderstanding of the effect of orbital cycles on the distribution of incoming solar radiation. The Croll-Milankovitch orbital cycles operate independently of changes in the Sun’s output. What the orbital cycles mainly do is change the latitudinal and seasonal distribution of incoming solar energy. But, averaged over the year, or over the whole globe, there’s little difference between “ice growth” and “ice decay” orbital geometries. In high orbital eccentricity geometries (varying in ~400,000 and ~100,000-year cycles), precessional (“wobble”) cycles (~23,000 year cycles) shift the season of perihelion.

      In intervals in which the earth is farthest from the Sun in boreal summer, with low tilt, the “canonical” C-M hypothesis would say there’s more chance of high-latitude Northern Hemisphere snow cover persisting through summer.

      The earth’s orbital obliquity (tilt) varies on a ~ 40,000 year cycle between ~ 22 degrees from the ecliptic to ~ 25 degrees (it’s now 23.5). In intervals of lower obliquity those high latitudes are not tilted towards the sun in summer as much as in high tilt intervals, creating a situation (in the C-M theory) conducive to summer persistence of snow cover. It is of course persistent and ongoing accumulation of snow that ultimately results in a glacier or ice sheet.

  • Thanks for the interesting post, Will.

    It is sad that people who deliberately distort science have so much influence in politics and public media. The only good thing is that once warming of surface temperatures resumes, which I expect to happen soon, those people will all be completely discredited.

    Another interesting projection was the 1981 Science paper by Jim Hansen et al., (http://pubs.giss.nasa.gov/docs/1981/1981_Hansen_etal_1.pdf) who also predicted warming and that by the end of the century the signal of global warming would be detectable given the “noise” of natural climate variability, both of which turned out to be pretty much true. http://www.realclimate.org/index.php/archives/2012/04/evaluating-a-1981-temperature-projection/

    Here a link to Andre Berger and M. F. Loutre’s note on the next ice age: ftp://ftp.soest.hawaii.edu/engels/Stanley/Textbook_update/Science_297/Berger-02.pdf

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PUBLIC COMMENT THREAD

  • http://biocycle.atmos.colostate.edu/ Scott Denning

    In the 1970s, the first comprehensive analysis of oxygen isotopes in sediments from cores taken from the sea floor established for the first time that the timing of the Ice Ages was linked to subtle changes in the Earth’s orbit around the Sun as suggested long ago by Serbian mathematician Milutin Milankovitch. In the context of orbital changes with cycles of tens to hundreds of thousands of years, this meant that IF ALL ELSE REMAINED CONSTANT, Earth’s climate would inevitably cool toward another Ice Age over the next 100,000 years or so.

    This is still true, but 100,000 years is a very long time. Note that it’s not at all inconsistent to expect very rapid warming over the next 300 years and still be at the beginning of a 100,000 year cooling trend due to orbital variations.

    More to the point, we know quite well, just as we did in the 1970’s that ALL ELSE IS NOT CONSTANT. In particular, we know that the rapid economic development in China and (soon) India will create an enormous increase int eh demand for energy, and that if this demand is met primarily through combustion of carbon that atmospheric CO2 will rise to between 3 and 4 times preindustrial concentrations. And we know in great quantitative detail how many Watts of outgoing heat this extra CO2 will absorb. And we know much better now than we did 40 years ago how sensitive the Earth’s climate is to each Watt of absorbed heat.

    The ironic thing is that the huge climate swings (Ice Ages) associated with subtle changes in Earth’s orbit are the strongest evidence we have of the sensitive of Earth’s climate in degrees per Watt. The fact that the ice melted at the end of the last Ice Age shows that if China and India industrialize with coal, the Earth’s climate will warm a similar amount in response. After all, a Watt of extra heat from CO2 is the same as a Watt of extra heat from the Sun.

    The fact of previous climate change due to “natural cycles” is probably the strongest evidence we have that adding the same amount of heat will warm future climate about as much as the warming following the last Ice Age. The difference is that 5 Celsius of global warming after the last Ice Age took about 10,000 years, whereas politicians’ Plan A is to add the same amount of heat over the next couple of centuries.

    The great irony is that politicians and their cheerleaders (see Dr J on here) don’t even understand the fundamental logical contradiction of their positions. The arrogance of big government indeed!

    • http://scholar.google.com.au/citations?user=msXM0dkAAAAJ Will Howard

      Scott, your comments are very pertinent. And perhaps an expanded future post could explore this issue in more detail.

      Some cite the Quaternary climate cycles as an example of “this has all happened before.” The “logical contradiction” is that these cycles are a source of our understanding of the role of greenhouse gases as powerful feedbacks, and of other feedback processes (e.g. albedo, among other short- and long-time scale processes) that mediate subtle changes in the distribution of incoming solar radiation into large-scale climate changes. Our emissions of GHGs are taking what likely operated as a feedback during the Quaternary cycles and making it a primary forcing of the Earth’s radiative balance (or imbalance in this case).

      There is often misunderstanding of the effect of orbital cycles on the distribution of incoming solar radiation. The Croll-Milankovitch orbital cycles operate independently of changes in the Sun’s output. What the orbital cycles mainly do is change the latitudinal and seasonal distribution of incoming solar energy. But, averaged over the year, or over the whole globe, there’s little difference between “ice growth” and “ice decay” orbital geometries. In high orbital eccentricity geometries (varying in ~400,000 and ~100,000-year cycles), precessional (“wobble”) cycles (~23,000 year cycles) shift the season of perihelion.

      In intervals in which the earth is farthest from the Sun in boreal summer, with low tilt, the “canonical” C-M hypothesis would say there’s more chance of high-latitude Northern Hemisphere snow cover persisting through summer.

      The earth’s orbital obliquity (tilt) varies on a ~ 40,000 year cycle between ~ 22 degrees from the ecliptic to ~ 25 degrees (it’s now 23.5). In intervals of lower obliquity those high latitudes are not tilted towards the sun in summer as much as in high tilt intervals, creating a situation (in the C-M theory) conducive to summer persistence of snow cover. It is of course persistent and ongoing accumulation of snow that ultimately results in a glacier or ice sheet.

  • http://ceoas.oregonstate.edu/profile/schmittner/ Andreas Schmittner

    Thanks for the interesting post, Will.

    It is sad that people who deliberately distort science have so much influence in politics and public media. The only good thing is that once warming of surface temperatures resumes, which I expect to happen soon, those people will all be completely discredited.

    Another interesting projection was the 1981 Science paper by Jim Hansen et al., (http://pubs.giss.nasa.gov/docs/1981/1981_Hansen_etal_1.pdf) who also predicted warming and that by the end of the century the signal of global warming would be detectable given the “noise” of natural climate variability, both of which turned out to be pretty much true. http://www.realclimate.org/index.php/archives/2012/04/evaluating-a-1981-temperature-projection/

    Here a link to Andre Berger and M. F. Loutre’s note on the next ice age: ftp://ftp.soest.hawaii.edu/engels/Stanley/Textbook_update/Science_297/Berger-02.pdf

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