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Monday, March 9, 2015

Dr. Soon's latest paper on natural climate variability published in Nature Geoscience

A paper published today in the journal Nature Geoscience studies changes in the intertropical convergence zone (ITCZ) over the western Pacific during the Little Ice Age. The paper is co-authored by skeptics Willie Soon and Robert M. Carter, and is yet another example of the high quality, peer-reviewed work on natural climate variability and potential solar-climate relationships being published in highly respected journals by CAGW skeptics such as Dr. Soon.

Unable to attack on a scientific basis anything Dr. Soon has published in peer-reviewed journals, smear-mongerer Gavin Schmidt of NASA/GISS instead told the NYT, “The science that Willie Soon does is almost pointless.” Schmidt thus claims it is "pointless" to study natural variability, solar-climate relationships, and hundreds of potential solar amplification mechanisms published in the peer-reviewed literature, effectively because Schmidt & his falsified climate models have already made their mind up that man-made CO2 is the climate control knob & the sun plays a "pointless" role in climate.

Note: Other papers have linked shifts in the ITCZ to solar activity and the bipolar seesaw theory of (natural) climate change.

UPDATE:

http://e2014.ieexa.cas.cn/research/researchprogress/201503/t20150310_145086.html

Fingerprints of the Sun on Asia-Australia Summer Monsoon Rainfalls during the Little Ice Age

author： source: Time: 2015-03-10

A new paper has been published in Nature Geoscience entitled ‘Dynamics of the intertropical convergence zone over the western Pacific during the Little Ice Age ’ by Hong Yan of the Institute of Earth Environment, Chinese Academy of Sciences and an international team of co-authors from the Alfred Wegener Institute (Wei Wei), Harvard-Smithsonian Center for Astrophysics (Willie Soon), Institute of Earth Environment (Zhisheng An, Weijian Zhou and Yuhong Wang), University of Hong Kong (Zhonghui Liu) and Institute of Public Affairs (Robert M. Carter). The results of the research indicate that both the East Asia Summer Monsoon and the Northern Australia Summer Monsoon retreated synchronously during the recent cold Little Ice Age in response to external forcings such as solar irradiance variation and possibly large volcanic eruptions.

The Asia-Australia monsoon covers the world’s most populated areas, and therefore understanding the factors that control monsoon-belt climatic variation through time is important for response-planning for healthy social-economic development for the globe. Many previous studies have focused on the past climate changes in the Asia-Australia monsoon area, often proposing that the western Pacific Intertropical Convergence Zone (ITCZ) or the associated rainbelt should have migrated southward during cold climate episodes, such as the Little Ice Age (AD 1400-1850). Such migrations should be associated with the occurrence of a weaker East Asian Summer Monsoon and a stronger Australian Summer Monsoon, with opposing rainfall variations between the two hemispheres.

However, hydrological records from the Asia-Australia summer monsoon area, analysed by Professor Hong Yan and his coauthors, show that southward migration of the ITCZ did not occur during the cold Little Ice Age. Instead, the hydrological data support the operation of a new dynamic mechanism named ‘ITCZ/Rainbelt contraction’ in the Western Pacific region during the Little Ice Age.

Prima facie, a southward migration of the ITCZ should result in less precipitation in the East Asia Summer Monsoon area but more rainfall in Australia Summer Monsoon area. In contrast, the Synthesis of a large set of palaeoclimatological records from across the monsoonal area establishes that the precipitation in both continental East Asia and northern Australia decreased synchronously during the Little Ice Age. The unusual spatial variation in paleoclimate records therefore documents a distinctly different rainfall pattern that violates the former expectation of ITCZ southward migration. Furthermore, comparison of these results with solar records indicates that a relationship exists between the rainfall changes and Total Solar Insolation.

To explain these changes, the scientists propose an alternative dynamic scenario which they have tested using process-based climate modeling. Rather than strict north-south migration, the multi-decadal to centennial change for the western Pacific Intertropical Convergence Zone can excitingly be shown to have contracted or expanded in parallel with solar irradiance variations. This new understanding clearly adds to the richness of mechanisms by which the Earth climate system can vary naturally and significantly over periods between a few decades and up to a century in length.

Pattern of rainfall within the East Asia Summer Monsoon (left) and Australia Summer Monsoon (right) area during the LIA. Locations of proxy-hydrology records in the Asia-Australia monsoon area are indicated. Locations that were dry, without apparent change and wet during the LIA are marked in red, purple and blue, respectively. The decreased rainfall in East Asia continent and northern Australia suggested the synchronous retreat of the East Asian Summer Monsoon and the Australian Summer Monsoon during the Little Ice Age (Image by Dr YAN Hong).

How climate models dismiss the role of the Sun in climate

How climate models dismiss the role of the Sun in climate change [Part 3]

How climate models dismiss the role of the Sun in climate change [Part 4]

Thursday, November 13, 2014

New paper finds another non-hockey-stick in Brazil

A new paper published in Palaeogeography, Palaeoclimatology, Palaeoecology reconstructs climate in NE Brazil over the past 2,400 years from lake sediments and finds another non-hockey-stick with lake levels and temperatures higher during the Medieval Warm Period than at the end of the record in the year 2000.

The paper also reconstructs the South American Summer Monsoon (SASM) and shows greater dryness of the SASM during the Medieval Warm Period than at the end of the record in 2000.

The data demonstrates nothing unusual, unprecedented, or unnatural about the present-day hydrological cycle, South American Summer Monsoon, NE Brazil lake levels, or temperatures in comparison to the past 2,400 years.

Note second graph from bottom by Michael Mann et al, therefore extreme caution indicated. Bottom graph shows Ljungqvist's non-hockey-stick temperature reconstruction for comparison. Lake levels were highest during the Medieval Warm Period [MCA] in comparison to the Little Ice Age [LIA] and the current warm period.

Lake levels were highest during the Medieval Warm Period [MCA] in comparison to the Little Ice Age [LIA] and the current warm period.

•: We studied sediments from Boqueirão Lake, Northeast Brazil (sensitive to ITCZ).
•: Diatom-based transfer function showed the lower water level between 400 BC and AD 400.
•: Medieval Climate Anomaly presented lake levels reaching its maximum.
•: Little Ice Age was a dryness period with low lake levels in the last 1000 years.
•: ITCZ seasonal shifts were larger during the MCA and tighter during the LIA.

Abstract

Lake level fluctuations and environmental changes during the late Holocene were inferred from changes in sedimentology, bulk and isotope organic geochemistry, and a diatom based transfer function in a sediment core from Boqueirão Lake, northeast Brazil. The age-depth model was established using fifteen AMS ¹⁴C dates. Lake water level began increasing about AD 400, and reached its maximum during the Medieval Climate Anomaly (MCA), AD ~ 900–1100. Low lake water level was recorded during the Little Ice Age (LIA), AD ~ 1400–1820, which allowed macrophyte development in the littoral zone that was recorded by high C_org/N_total ratios. Considerable lake level variability was evident during the Current Warm Period (CWP). Humid/dry conditions in northeast Brazil during MCA/LIA, respectively, are related to the southward shift of Inter-Tropical Convergence Zone (ITCZ) during austral summer and fall. Those conditions contrast with records of a decrease/increase in the South American Summer Monsoon (SASM) during these periods. This observation also contrasts with paleoclimate inferences from the circum-Caribbean region indicating a northward shift of the ITCZ northern hemisphere summer position during the MCA and a southward shift during the LIA. We suggest that these shifts in ITCZ seasonality were higher during the MCA and smaller during the LIA. Our aim was to answer whether the zonal atmospheric circulation cell between the Amazon and northeast Brazil was responsible for antiphasing with the SASM. A strong monsoon over South America during the LIA reinforced convection upon Amazon, increasing the northeast low in the upper troposphere and large-scale subsidence over northeast Brazil and the Atlantic Ocean leading to a northward repositioning of the South Atlantic Subtropical Anticyclone. These factors in combination may have limited the southward seasonal shift of ITCZ, and they must have been responsible for drier conditions in northeast Brazil during the LIA.

Tuesday, September 16, 2014

New paper links intensification of El Niño & La Niña to solar activity

A paper published today in Earth and Planetary Science Letters reconstructs the "El Niño-Southern Oscillation (ENSO) [which] represents the largest perturbation to the climate system on an inter-annual time scale" from a 10,000 year Holocene proxy in the Galapagos Islands.

According to the authors,

"Periods of strong or frequent El Niño tended to occur during peaks in solar activity and during extended droughts in the United States Great Plains linked to La Niña. These changing modes of ENSO activity at millennial and multi-centennial timescales may have been caused by variations in the seasonal receipts of solar radiation associated with the precession of the equinoxes and/or changes in solar activity, respectively.

El Niño and La Niña events are coupled in the Holocene

Intensification of both ENSO phases [El Nino & La Nina] broadly coincided with peaks in solar activity.

Our data from the core of the ENSO region thus calls into question earlier studies that reported a lack of El Niño activity in the early Holocene. In agreement with other proxy evidence from the tropical Pacific, the mid-Holocene (5600–3500 yr BP) was a time of consistently weak El Niño activity, as were the Early Middle Ages (∼1000–1500 yr BP). El Niño activity was moderate to high during the remainder of the last 3500 years."

The paper joins many others in the scientific literature finding solar activity is the main driver of ENSO, as well as other ocean oscillations. Thus, solar influence on ENSO, "the largest perturbation to the climate system on an inter-annual time scale," is another of many solar amplification mechanisms described in the literature.

El Niño evolution during the Holocene revealed by a biomarker rain gauge in the Galápagos Islands

•: Changes in El Junco log (bot) and biomarker δD reveal the evolution of El Niño.
•: Alternating extremes in El Niño events characterize the early Holocene.
•: Our data refute earlier studies on lack of El Niño activity in the early Holocene.
•: El Niño and La Niña events are coupled in the Holocene.
•: Intensification of both ENSO phases broadly coincided with peaks in solar activity.

Abstract

The El Niño-Southern Oscillation (ENSO) represents the largest perturbation to the climate system on an inter-annual time scale, but its evolution since the end of the last ice age remains debated due to the lack of unambiguous ENSO records lasting longer than a few centuries. Changes in the concentration and hydrogen isotope ratio of lipids produced by the green alga Botryococcus braunii, which blooms during El Niño rains in the Galápagos Islands, indicate that the early Holocene (9200–5600 yr BP) was characterized by alternating extremes in the intensity and/or frequency of El Niño events that lasted a century or more. Our data from the core of the ENSO region thus calls into question earlier studies that reported a lack of El Niño activity in the early Holocene. In agreement with other proxy evidence from the tropical Pacific, the mid-Holocene (5600–3500 yr BP) was a time of consistently weak El Niño activity, as were the Early Middle Ages (∼1000–1500 yr BP). El Niño activity was moderate to high during the remainder of the last 3500 years. Periods of strong or frequent El Niño tended to occur during peaks in solar activity and during extended droughts in the United States Great Plains linked to La Niña. These changing modes of ENSO activity at millennial and multi-centennial timescales may have been caused by variations in the seasonal receipts of solar radiation associated with the precession of the equinoxes and/or changes in solar activity, respectively.

__________________________________________

Also published today, a companion paper to the above paper showing El Nino strength peaked around 700-800 years ago and at the end of the record [left side of graph] was in the mid-range of the past 3000 years, i.e. not unprecedented or unusual:

Separating ITCZ- and ENSO-related rainfall changes in the Galápagos over the last 3 kyr using D/H ratios of multiple lipid biomarkers

Alyssa R. Atwood ^,,
Julian P. Sachs

•: Novel proxies for tracking hydrologic changes of El Junco Lake, Galápagos.
•: Based on molecular and isotopic biomarkers from several types of plants and algae.
•: Proxies used to infer past changes in mean rainfall and El Niño-related rainfall over last 3 kyr.
•: Novel method used to infer changes in ITCZ-related rainfall during select periods.

Abstract

We present a 3000-yr rainfall reconstruction from the Galápagos Islands that is based on paired biomarker records from the sediment of El Junco Lake. Located in the eastern equatorial Pacific, the climate of the Galápagos Islands is governed by movements of the Intertropical Convergence Zone (ITCZ) and the El Niño-Southern Oscillation (ENSO). We use a novel method for reconstructing past ENSO- and ITCZ-related rainfall changes through analysis of molecular and isotopic biomarker records representing several types of plants and algae that grow under differing climatic conditions. We propose that δD values of dinosterol, a sterol produced by dinoflagellates, record changes in mean rainfall in El Junco Lake, while δD values of C₃₄botryococcene, a hydrocarbon unique to the green alga Botryococcus braunii, record changes in rainfall associated with moderate-to-strong El Niño events. We use these proxies to infer changes in mean rainfall and El Niño-related rainfall over the past 3000 yr. During periods in which the inferred change in El Niño-related rainfall opposed the change in mean rainfall, we infer changes in the amount of ITCZ-related rainfall. Simulations with an idealized isotope hydrology model of El Junco Lake help illustrate the interpretation of these proxy reconstructions. Opposing changes in El Niño- and ITCZ-related rainfall appear to account for several of the largest inferred hydrologic changes in El Junco Lake. We propose that these reconstructions can be used to infer changes in frequency and/or intensity of El Niño events and changes in the position of the ITCZ in the eastern equatorial Pacific over the past 3000 yr. Comparison with El Junco Lake sediment grain size records indicates general agreement of inferred rainfall changes over the late Holocene.

___________________________________________________

On the other hand, climate models and the IPCC have no consensus on ENSO due to climate change, likely because climate models do not consider any possible direct or indirect solar influence upon ENSO [from NOAA]:

ENSO in climate models

When climate models are tasked with answering this question, they have struggled to give a consistent prognostication (Vecchi and Wittenberg 2010). For example, in Figure 2, the y-axis refers to ENSO variability (how frequently events occur) while the x-axis refers to the pattern of SST change (whether it looks more like El Niño or La Niña). While most climate models show a tendency towards more SST warming in central/eastern Equatorial Pacific than western (i.e. points located on the right side of the plot), there is no consensus on what that actually means for ENSO variations (i.e. points placement on the y-axis). Some models show decreasing variability (i.e. points in the bottom half), increasing variability (i.e. points in the upper half), or remains nearly the same (i.e. points in the middle). The point near the origin (center) would be if that bratty child in the dining room adjusted the switches but the total amount of light never changed.

Figure 2. Projections by 21 global climate models of changes in the mean state of sea level pressure of the tropical Pacific Ocean (x-axis) and ENSO variability (y-axis). When climate projections of the mean state of the tropical Pacific resemble something that looks like El Niño, points are greater than 0 along the x-axis and vice-versa for La Niña (points less than 0). When ENSO variability increases, points are located greater than 1 along the y-axis and vice versa for a decrease in ENSO variability (points less than 1). We see here that most climate models project a trend towards an El Niño-like average state of the tropical Pacific Ocean but there is considerable model-to-model disagreement regarding whether ENSO variability will increase, decrease, or remain the same in the future. Adapted from IPCC AR4 (2007).

What does the Intergovernmental Panel on Climate Change (IPCC) say?

It’s not surprising then that the IPCC report issued in 2013 takes a measured approach. The IPCC has LOW confidence in exactly what will happen to ENSO in the future even while they have HIGH confidence that ENSO itself will continue (IPCC, 2013).

Even though we are not sure how ENSO will change in the future, the impacts of ENSO will probably be affected. In a warming world, rainfall variability is expected to increase. Wet areas will likely get wetter, while dry areas get drier. Combined with a future ENSO event, climate change could strengthen or weaken the typical weather patterns associated with ENSO.

For instance, during El Niño events, below-average rain usually occurs across Indonesia. However, according to climate models, average annual rainfall will increase in the same area. So, during future El Niño events, dry conditions in Indonesia may not be as dry as today. Similarly, La Niña events are associated with a drying of southwestern North America and so are impacts from climate change. So drying during future La Niñas may be enhanced (Vecchi and Wittenberg 2010).

This is a very brief overview of the potential impact of climate change on ENSO and on how the atmosphere and ocean might change in the next hundred years or more. But remember, just because we do not have high confidence on how ENSO might change in the future does not mean that it won’t. It just means scientists have more work to do.

Sunday, March 30, 2014

New paper supports the bipolar seesaw theory of abrupt climate change

A paper published today in Nature finds "clear" evidence of a "hydrologic seesaw in which latitudinal migrations of the Intertropical Convergence Zone (ITCZ) produce simultaneous wetting (increased precipitation) in one hemisphere and drying in the other." According to the authors, these shifts can have "serious effects on temperate climate systems. Furthermore, our result implies that insolation-driven ITCZ dynamics may provoke water vapour and vegetation feedbacks in northern mid-latitude regions and could have regulated global climate conditions throughout the late Quaternary ice age cycles."

The paper provides additional, "clear" evidence supporting the "bipolar seesaw theory of abrupt climate change." "Theoretical models and observational data have long suggested that the Northern and Southern Hemisphere climates behave in a seesaw-like fashion: when the northern ocean warms, the southern ocean cools and vice versa."

Glacials and interglacials on the northern and southern hemisphere somehow do not seem to correspond. This has led to a ‘thermal bipolar seesaw theory,’ whereby an off-mode in the thermohaline circulation leads to an ice age in Europe, but excess heat storage down south.

Given that ice cores show a lag between Arctic and Antarctic climate changes of 300-1500 years, it begs the question given that Antarctic sea ice is at record highs and Arctic sea ice has declined during the satellite era, whether this may represent part of a natural seesaw pattern, shifting heat via the thermohaline circulation from the Southern Hemisphere to the Northern Hemisphere and explaining why less warming has been observed in the Southern Hemisphere since 1850.

Mid-latitude interhemispheric hydrologic seesaw over the past 550,000 years

Nature advance online publication 30 March 2014. doi:10.1038/nature13076

Authors: Kyoung-nam Jo, Kyung Sik Woo, Sangheon Yi, Dong Yoon Yang, Hyoun Soo Lim, Yongjin Wang, Hai Cheng & R. Lawrence Edwards

An interhemispheric hydrologic seesaw—in which latitudinal migrations of the Intertropical Convergence Zone (ITCZ) produce simultaneous wetting (increased precipitation) in one hemisphere and drying in the other—has been discovered in some tropical and subtropical regions. For instance, Chinese and Brazilian subtropical speleothem (cave formations such as stalactites and stalagmites) records show opposite trends in time series of oxygen isotopes (a proxy for precipitation variability) at millennial to orbital timescales, suggesting that hydrologic cycles were antiphased in the northerly versus southerly subtropics. This tropical to subtropical hydrologic phenomenon is likely to be an initial and important climatic response to orbital forcing. The impacts of such an interhemispheric hydrologic seesaw on higher-latitude regions and the global climate system, however, are unknown. Here we show that the antiphasing seen in the tropical records is also present in both hemispheres of the mid-latitude western Pacific Ocean. Our results are based on a new 550,000-year record of the growth frequency of speleothems from the Korean peninsula, which we compare to Southern Hemisphere equivalents. The Korean data are discontinuous and derived from 24 separate speleothems, but still allow the identification of periods of peak speleothem growth and, thus, precipitation. The clear hemispheric antiphasing indicates that the sphere of influence of the interhemispheric hydrologic seesaw over the past 550,000 years extended at least to the mid-latitudes, such as northeast Asia, and that orbital-timescale ITCZ shifts can have serious effects on temperate climate systems. Furthermore, our result implies that insolation-driven ITCZ dynamics may provoke water vapour and vegetation feedbacks in northern mid-latitude regions and could have regulated global climate conditions throughout the late Quaternary ice age cycles.

The north–south climate seesaw [Nature 2009]

Theoretical models and observational data have long suggested that the Northern and Southern Hemisphere climates behave in a seesaw-like fashion: when the northern ocean warms, the southern ocean cools and vice versa. So far, however, the data have indicated a much muted response in Antarctic climate compared to the Arctic. An analysis of new records from an ocean core from the South Atlantic — including planktonic foraminifera assemblages, Mg/Ca ratios, temperature and ocean productivity data — shows that the South Atlantic cooled essentially instantaneously with the warming in the North Atlantic during the last deglaciation. This first concrete evidence of an immediate seesaw connection also provides a link between the rapid warming in the North Atlantic and the more gradual Antarctic response, and suggests a mechanism potentially driving rapid Northern Hemisphere deglaciation.

NEWS AND VIEWS:Climate change: Southern see-saw seen

The bipolar see-saw hypothesis provides an explanation for why temperature shifts in the two hemispheres were out of phase at certain times. The hypothesis has now passed a test of one of its predictions.

Jeffrey P. Severinghaus

doi:10.1038/4571093a

Full Text | PDF (1,313K)

ARTICLE:Interhemispheric Atlantic seesaw response during the last deglaciation

Stephen Barker, Paula Diz, Maryline J. Vautravers, Jennifer Pike, Gregor Knorr, Ian R. Hall & Wallace S. Broecker

doi:10.1038/nature07770

Abstract | Full Text | PDF (626K) | Supplementary information

Thursday, September 18, 2014

Arctic & Antarctic sea ice extent demonstrates the bipolar seesaw theory of climate

Sunshine Hours has posted today a "mirror graph" of Arctic and Antarctic sea ice which illustrates the bipolar seesaw theory of abrupt climate change in action. It is well known that glaciation and deglaciation of the North and South poles are not synchronous and frequently out of phase or in opposite phases, similar to the "mirror graph" below of Arctic and Antarctic sea ice trends since 1979. This is entirely consistent with Milankovitch theory, the 1000-1500 year Atlantic Meridional Overturning Circulation [AMOC] and other shorter-term ocean oscillations [e.g. the AMO], and the 1st law of thermodynamics which allows for relatively constant solar energy input to be shifted in location while conserving energy.

Further, the seesaw theory of abrupt climate change is far more plausible than the ludicrous, stretched-thin theory that global warming is causing record-high levels of Antarctic sea ice and more record-high levels of snow and cold. In fact, climate models robustly predicted the opposite of what has caused the recent record-cold US weather.

Schematic of the bipolar seesaw. North Atlantic temperature changes are mirrored by equal amplitude South Atlantic changes of opposite sign. Southern Ocean temperatures are relaxed toward this South Atlantic temperature. Source: Modeling the Bipolar Seesaw.

The seesaw theory of climate is also entirely consistent with conservation of energy, unlike Trenberth's theory of "missing heat" from man-made CO2 "hidden" somewhere within in the climate system.

Seesaw theory in action:

Arctic/Antarctic Mirror Graph Day 260

For those who say Antarctic Sea Ice Extent increases are small and have nothing in common with Arctic losses:

Mirror Sea Ice Extent for Day 260 From 1978

Repost:

Sunday, March 30, 2014New paper supports the bipolar seesaw theory of abrupt climate change

A paper published today in Nature finds "clear" evidence of a "hydrologic seesaw in which latitudinal migrations of the Intertropical Convergence Zone (ITCZ) produce simultaneous wetting (increased precipitation) in one hemisphere and drying in the other." According to the authors, these shifts can have "serious effects on temperate climate systems. Furthermore, our result implies that insolation-driven ITCZ dynamics may provoke water vapour and vegetation feedbacks in northern mid-latitude regions and could have regulated global climate conditions throughout the late Quaternary ice age cycles."

The paper provides additional, "clear" evidence supporting the "bipolar seesaw theory of abrupt climate change." "Theoretical models and observational data have long suggested that the Northern and Southern Hemisphere climates behave in a seesaw-like fashion: when the northern ocean warms, the southern ocean cools and vice versa." 

Glacials and interglacials on the northern and southern hemisphere somehow do not seem to correspond. This has led to a ‘thermal bipolar seesaw theory,’ whereby an off-mode in the thermohaline circulation leads to an ice age in Europe, but excess heat storage down south.

Given that ice cores show a lag between Arctic and Antarctic climate changes of 300-1500 years, it begs the question given that Antarctic sea ice is at record highs and Arctic sea ice has declined during the satellite era, whether this may represent part of a natural seesaw pattern, shifting heat via the thermohaline circulation from the Southern Hemisphere to the Northern Hemisphere and explaining why less warming has been observed in the Southern Hemisphere since 1850.

Mid-latitude interhemispheric hydrologic seesaw over the past 550,000 years

Nature advance online publication 30 March 2014. doi:10.1038/nature13076

Authors: Kyoung-nam Jo, Kyung Sik Woo, Sangheon Yi, Dong Yoon Yang, Hyoun Soo Lim, Yongjin Wang, Hai Cheng & R. Lawrence Edwards

An interhemispheric hydrologic seesaw—in which latitudinal migrations of the Intertropical Convergence Zone (ITCZ) produce simultaneous wetting (increased precipitation) in one hemisphere and drying in the other—has been discovered in some tropical and subtropical regions. For instance, Chinese and Brazilian subtropical speleothem (cave formations such as stalactites and stalagmites) records show opposite trends in time series of oxygen isotopes (a proxy for precipitation variability) at millennial to orbital timescales, suggesting that hydrologic cycles were antiphased in the northerly versus southerly subtropics. This tropical to subtropical hydrologic phenomenon is likely to be an initial and important climatic response to orbital forcing. The impacts of such an interhemispheric hydrologic seesaw on higher-latitude regions and the global climate system, however, are unknown. Here we show that the antiphasing seen in the tropical records is also present in both hemispheres of the mid-latitude western Pacific Ocean. Our results are based on a new 550,000-year record of the growth frequency of speleothems from the Korean peninsula, which we compare to Southern Hemisphere equivalents. The Korean data are discontinuous and derived from 24 separate speleothems, but still allow the identification of periods of peak speleothem growth and, thus, precipitation. The clear hemispheric antiphasing indicates that the sphere of influence of the interhemispheric hydrologic seesaw over the past 550,000 years extended at least to the mid-latitudes, such as northeast Asia, and that orbital-timescale ITCZ shifts can haveserious effects on temperate climate systems. Furthermore, our result implies that insolation-driven ITCZ dynamics may provoke water vapour and vegetation feedbacks in northern mid-latitude regions and could have regulated global climate conditions throughout the late Quaternary ice age cycles.

Related:

The north–south climate seesaw [Nature 2009]
Theoretical models and observational data have long suggested that the Northern and Southern Hemisphere climates behave in a seesaw-like fashion: when the northern ocean warms, the southern ocean cools and vice versa. So far, however, the data have indicated a much muted response in Antarctic climate compared to the Arctic. An analysis of new records from an ocean core from the South Atlantic — including planktonic foraminifera assemblages, Mg/Ca ratios, temperature and ocean productivity data — shows that the South Atlantic cooled essentially instantaneously with the warming in the North Atlantic during the last deglaciation. This first concrete evidence of an immediate seesaw connection also provides a link between the rapid warming in the North Atlantic and the more gradual Antarctic response, and suggests a mechanism potentially driving rapid Northern Hemisphere deglaciation.

NEWS AND VIEWS:Climate change: Southern see-saw seen
The bipolar see-saw hypothesis provides an explanation for why temperature shifts in the two hemispheres were out of phase at certain times. The hypothesis has now passed a test of one of its predictions.

Jeffrey P. Severinghaus

doi:10.1038/4571093a

Full Text | PDF (1,313K)

ARTICLE:Interhemispheric Atlantic seesaw response during the last deglaciation
Stephen Barker, Paula Diz, Maryline J. Vautravers, Jennifer Pike, Gregor Knorr, Ian R. Hall & Wallace S. Broecker

doi:10.1038/nature07770

Abstract | Full Text | PDF (626K) | Supplementary information