How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

Little Ice Age (Regional: Australia/New Zealand) -- Summary
Climate alarmists generally contend that the Little Ice Age was localized to countries bordering the North Atlantic Ocean, because if there had been a global Little Ice Age, there would have had to have been a global Medieval Warm Period to help define it; and if there was a global Medieval Warm Period that was as warm as, or warmer than, the Current Warm Period, there would be no valid reason for claiming that the warmth of the modern era is the result of anthropogenic CO2 emissions, for the air's CO2 concentration during both the Little Ice Age and Medieval Warm Period was fairly constant and fully 100 ppm less than what it is today, which suggests that since something other than a rise and fall in the air's CO2 content was responsible for producing both medieval warmth and subsequent Little Ice Age cold, that same something else may well have been - and likely was - responsible for the warming of the past century that brought us out of the Little Ice Age.  Hence, we continuously scan the scientific literature for evidence related to this topic; and we here report what we have learned about the subject from studies conducted in Australia and New Zealand.

Wilson et al. (1979) derived a 14C-dated 18O/16O profile from a stalagmite found in a New Zealand cave, from which they developed a proxy temperature record that was broadly similar to the climate record of England.  This record exhibited a period in the early part of the past millennium that was about 0.75C warmer than it was in the mid-20th century.  In addition, the temperature near the latter part of the 17th century was about 0.75C cooler than it was in the middle of the 20th century.  In discussing the significance of these findings, they say that one of their objectives was to compare the temperature record from New Zealand - which they emphasize is "in the Southern Hemisphere and a region meteorologically unrelated to Europe" - with the English climate curve.  Their conclusion?  "The temperature curve for New Zealand is apparently broadly similar to England and such climatic fluctuations as the Medieval Warm Period and Little Ice Age are not just a local European phenomenon."

Nearly a quarter of a century later, Hendy et al. (2002) reconstructed a 420-year sea surface temperature (SST) history based on Sr/Ca measurements of several coral cores taken from massive Porites colonies in the central portion of Australia's Great Barrier Reef.  The earliest part of this temperature history, from 1565 to about 1700, corresponds to the coldest period of the Little Ice Age; and five-year blocks of mean SSTs during this South Pacific cold period were sometimes 0.5 to 1.0C or more below the region's long-term mean.  Over the following century, however, South Pacific SSTs were much warmer, as were temperatures in the Northern Hemisphere, as per the original IPCC temperature history of that half of the globe, which we believe to be considerably more realistic than the infamous hockeystick history of Mann et al. (1999).  In the South Pacific, in fact, SSTs during this period were consistently as warm as - and many times even warmer than - those of the early 1980s, where the coral record ended.  Then, during the late 1800s, the South Pacific once again experienced colder conditions that coincided with the "last gasp" of the Little Ice Age in the Northern Hemisphere, after which the Modern Warm Period made its presence felt in both regions.

These observations do two important things.  First, the largely synchronous temperature trends of the South Pacific Ocean and Northern Hemisphere lend credence to our belief that the Little Ice Age was a truly global phenomenon and not - as climate alarmists are prone to claim - a minor regional anomaly of lands bordering on the North Atlantic Ocean.  Second, the fact that the data of Hendy et al., as well as the data of Linsley et al. (2000), portray mid-18th century South Pacific SSTs as being equally as warm as - or even warmer than - the latter part of the 20th century lends credence to our belief that the climate of the modern world is in no way unusual.

Enlarging on this thought, we note that the mid-18th century warmth of the tropical and subtropical South Pacific Ocean occurred at essentially the same time as the significant peak in Northern Hemispheric temperature that is strikingly evident in the data of Jones et al. (1998).  This observation suggests to us that if the data of Hendy et al. and Linsley et al. are representative of the great expanse of Southern Hemispheric ocean, the mid-18th century mean temperature of the entire globe may well have been about the same as it is now, but at a time when the air's CO2 concentration was hovering somewhere in the vicinity of only 280 ppm, or nearly 100 ppm less than what it is today.

Returning to New Zealand, Williams et al. (2004) revised and built upon results that had previously been presented by Williams et al. (1999) based on stable isotope stratigraphy from caves at Waitomo, which is located at 38.3S latitude about 35 km from the west coast of the central North Island of New Zealand.  Specifically, they enhanced three existing speleothem records "by adding another chronology, increasing the subsample resolution of existing records, and by much improving the temporal control of all chronologies by basing it entirely on uranium series TIMS dating."  The resulting speleothem master chronologies reveal a warmer-than-present late-Holocene warm peak between 0.9 and 0.6 ka BP that they equate with the Medieval Warm Period in Europe, while they note that in New Zealand this time interval "coincided with a period of Polynesian settlement (McGlone and Wilmshurst, 1999)."  Thereafter, they report that temperatures "cooled rapidly to a trough about 325 years ago," which they say "was the culmination of the 'Little Ice Age' in Europe."

Rounding out our review of Australia/New Zealand studies, Winkler (2004) decided "to test whether the chronology of the 'Little Ice Age' in the Southern Hemisphere is similar to that of the Northern Hemisphere" by using lichenometric dating techniques to establish the time of expression of the maximum Little Ice Age as revealed by the behaviors of the Eugenie, Hooker, Mueller and Tasman Glaciers in Mt Cook National Park, Southern Alps, New Zealand.  This work revealed, in his words, "a 'Little Ice Age' maximum during the mid-eighteenth century (around AD 1725-1740)."  Then, he says that "after a slow but constant retreat during the second half of the eighteenth and the first half of the nineteenth centuries, the glaciers experienced major readvances during the second half of the nineteenth century (around 1860 and 1890/95)."  Winkler also reports that "the timing of the 'Little Ice Age' maximum of the study glaciers agrees with a major advance of the Fox and Franz Josef Glaciers west of the main divide in the Southern Alps and with the 'Little Ice Age' maximum in southern and northern Norway," citing in this regard the studies of Erikstad and Sollid (1986), Bickerton and Matthews (1993), Winkler (1996) and Winkler et al. (2003) relative to southern Norway and the studies of Innes (1984) and Winkler (2001, 2003) relative to northern Norway.

In conclusion, we suggest that for climate alarmists who claim the Little Ice Age was a less-than-global phenomenon restricted to lands bordering the North Atlantic Ocean, it must be embarrassing to see research papers, such as this ones above, that document the existence of this multi-century cold spell in lands as far away as New Zealand, and to additionally learn that the Little Ice Age was largely synchronous in both the Northern and Southern Hemispheres.  One would think, therefore, that it would do them good to admit the obvious about this matter; but they can't.  Why?  Because it is the Little Ice Age that makes 20th-century global warming look so dramatic, and which allows them to claim it must be unnatural and caused by anthropogenic CO2 emissions, when in reality it is but the recovery of the planet from perhaps the coldest period of the current interglacial to a level of warmth that has been experienced several times before, such as during the Medieval Warm Period of a thousand years ago and the Roman Warm Period of two thousand years ago, when there was 100 ppm less CO2 in the air than there is currently.

Bickerton, R.W. and Matthews, J.A.  1993.  'Little Ice Age' variations of outlet glaciers from the Jostedalsbreen ice-cap, southern Norway: a regional lichenometric-dating study of ice-marginal moraine sequences and their climatic significance.  Journal of Quaternary Science 8: 45-66.

Erikstad, L. and Sollid, J.L.  1986.  Neoglaciation in South Norway using lichenometric methods.  Norsk Geografisk Tidsskrift 40: 85-100.

Hendy, E.J., Gagan, M.K., Alibert, C.A., McCulloch, M.T., Lough, J.M. and Isdale, P.J.  2002.  Abrupt decrease in tropical Pacific sea surface salinity at end of Little Ice Age.  Science 295: 1511-1514.

Innes, J.L.  1984.  Lichenometric dating of moraine ridges in northern Norway: some problems of application.  Geografiska Annaler 66A: 341-352.

Jones, P.D., Briffa, K.R., Barnett, T.P. and Tett, S.F.B.  1998.  High-resolution palaeoclimatic records for the last millennium: interpretation, integration and comparison with general circulation model control-run temperatures.  The Holocene 8: 455-471.

Linsley, B.K., Wellington, G.M. and Schrag, D.P.  2000.  Decadal sea surface temperature variability in the subtropical South Pacific from 1726 to 1997 A.D.  Science 290: 1145-1148.

McGlone, M.S. and Wilmshurst, J.M.  1999.  Dating initial Maori environmental impact in New Zealand.  Quaternary International 59: 5-16.

Williams, P.W., King, D.N.T., Zhao, J.-X. and Collerson, K.D.  2004.  Speleothem master chronologies: combined Holocene 18O and 13C records from the North Island of New Zealand and their palaeoenvironmental interpretation.  The Holocene 14: 194-208.

Williams, P.W., Marshall, A., Ford, D.C. and Jenkinson, A.N.  1999.  Palaeoclimatic interpretation of stable isotope data from Holocene speleothems of the Waitomo district, North Island, New Zealand.  The Holocene 9: 649-657.

Wilson, A.T., Hendy, C.H. and Reynolds, C.P.  1979.  Short-term climate change and New Zealand temperatures during the last millennium.  Nature 279: 315-317.

Winkler, S.  1996.  Fruhrezente und rezente Gletscherstandsschwankungen in Ostalpen und West-/Zentralnorwegen.  Trier: Geographische Gesellschaft Trier, Trierer Geographische Studien 15.

Winkler, S.  2001.  Untersuchungen zur Klima- und Morphodynamik in skandinavischen Gebirgsregionen wahrend des Holozin - ein Vergleich ihrer Wechselwirkungen und Prozessysteme im uberregionalen Kontext kaltgemassigter maritimer Gebirgsregionen.  Unpublished 'Habilitationsschrift,' University of Trier.

Winkler, S.  2003.  A new interpretation of the date of the 'Little Ice Age' maximum at Svartisen and Okstindan, northern Norway.  The Holocene 13: 83-95.

Winkler, S.  2004.  Lichenometric dating of the 'Little Ice Age' maximum in Mt Cook National Park, Southern Alps, New Zealand.  The Holocene 14: 911-920.

Winkler, S., Matthews, J.A., Shakesby, R.A. and Dresser, P.O.  2003.  Glacier variations in Breheimen, southern Norway: dating Little Ice Age moraine sequences at seven low-altitude glaciers.  Journal of Quaternary Science 18: 395-413.

Last updated 9 November 2005