Back in the 1980’s I came across a scientific paper by Robin Warner and Wayne Erskine in a book called ‘Fluvial Geomorphology of Australia’. Fluvial is to do with rivers – geomorphology is to do with form in landscapes. What they discovered was that rivers in eastern Australia changed form – from low energy meandering to high energy braided forms and back – every few decades. The intriguing finding implies that there are changes in rainfall that persist over decades and then switch to another state. They were dubbed flood and drought dominated regimes. Drought in the early part of the 20th century to the mid 1940’s, floods to 1976, drought to the turn of the century and a return to marginally higher rainfall since. It began a damn near 30 year odyssey – in the spirit of natural philosophy – to discover the source and import of this variability.
Source: NASA Earth Observatory
Turns out that it is a combination of conditions in the northern and central Pacific Ocean that is of immense significance. A 20 to 30 year change in the volume of frigid and nutrient rich water upwelling from the abysmal depths. A generally warmer or cooler sea surface in the northern Pacific and greater frequency and intensity of El Niño or La Niña respectively. This sets up changes in patterns of wind, currents and cloud that cause changes in rainfall, biology and temperature globally. In the cool pattern shown above – booming ecologies, drought in the Americas and Europe, rainfall in Australia, Indonesia, Africa, China and India and cooler global temperatures. The reverse in the warm phase. Warming to 1944, cooling to 1976, warming again to 1998 and – at the least – not warming since. It leads to a prediction that the La Niña currently emerging is likely to be large.
It is one of the changes in the Earth system that was characterized by the US Academy of Sciences – as long ago as 2002 – as abrupt. Abrupt climate change happens when the system is pushed past a threshold and transitions to a new state that is determined by shifts in cloud, wind, ice, currents and biology. The cause may be imperceptibly small and the change unpredictably large and rapid.
“Large, abrupt climate changes have affected hemispheric to global regions repeatedly, as shown by numerous paleoclimate records (Broecker, 1995, 1997). Changes of up to 16°C and a factor of 2 in precipitation have occurred in some places in periods as short as decades to years (Alley and Clark, 1999; Lang et al., 1999). However, before the 1990s, the dominant view of past climate change emphasized the slow, gradual swings of the ice ages tied to features of the earth’s orbit over tens of millennia or the 100-million-year changes occurring with continental drift. But unequivocal geologic evidence pieced together over the last few decades shows that climate can change abruptly, and this has forced a reexamination of climate instability and feedback processes (NRC, 1998). Just as occasional floods punctuate the peace of river towns and occasional earthquakes shake usually quiet regions near active faults, abrupt changes punctuate the sweep of climate history.” US Academy of Sciences, Abrupt climate change: inevitable surprises
Changes in the Pacific Ocean state can be traced in sediment, ice cores, stalagmites and corals. A record covering the last 12,000 years was developed by Christopher Moy and colleagues from measurements of red sediment in a South American lake. More red sediment is associated with El Niño. The record shows periods of high and low El Niño activity alternating with a period of about 2,000 years. There was a shift from La Niña dominance to El Niño dominance 5000 years ago that is associated with the drying of the Sahel. There is a period around 3,500 years ago of high El Niño activity associated with the demise of the Minoan civilisation (Tsonis et al, 2010). During this period red intensity was in excess of 200. For comparison, red intensity in the ‘extreme’ 1997/98 El Niño was 99. It shows mega-droughts and mega-floods that make those of the 20th century seem moderate in comparison. Natural El Niño–Southern Oscillation (ENSO) variability is considerably in excess of that seen in the modern period.
Tessa Vance and colleagues devised a 1000 year record from salt content in an Antarctic ice core. More salt is La Niña as a result of changing winds in the Southern Ocean. It revealed several interesting facts. The persistence of the 20 to 30 year pattern. A change in the period of oscillation between El Niño and La Niña states at the end of the 19th century. A 1000 year peak in El Niño frequency and intensity in the 20th century which resulted in uncharacteristically dry conditions since 1920.Source: Antarctic Climate and Ecosystems Cooperative Research Centre
Hence the folly of short term projections – i.e. 50 years – of temperature and rainfall and their attribution to anthropogenic climate change. It is scientific nonsense of the highest order that is inexplicable as anything but a fraud perpetuated on a public conditioned to trust science and scientists. Climate varies substantially, rapidly and frequently over all of climate history. Conditions over the 20th century have remained within – by a considerable margin – the limits of natural variability.
The longer term proxies beg the question – as all of the extreme paleoclimatic changes are entirely natural – of causality. Any answer on this is speculative but the activity of the Sun with its impact on Southern Ocean winds provides an intriguing parallel to the ENSO proxy shown above.
The isotope carbon 14 is produced by cosmic rays in the atmosphere. As the Sun dims magnetic shielding of the atmosphere is diminished and more cosmic rays reach the atmosphere. Such that low solar activity is associated with more carbon 14 and vice versa. So although correlation is not causation it appears that low solar activity is associated with La Niña dominance, higher rainfall in Australia and cooler global temperatures.
The earth.nullschool site shows surface wind conditions at almost real time – I have centred it on the Antarctic. This site is very cool if you are so inclined. The westerlies circling the sub-polar region result from planetary spin. Low solar activity sees the atmosphere above the South Pole cool both directly with less solar radiant energy and as reduced ozone warming by solar ultraviolet radiation. The cooling increases polar sea level pressure pushing the storms circling the pole into higher latitudes. As an aside – a cold and blustery winter in southern climes seems quite likely.
This pushes more cold Southern Ocean water north in the Peruvian Current. A similar process happens in the Northern Hemisphere. Low solar activity spins up the north and south Pacific gyres on decadal and much longer timescales. The cold sub-polar water displaces the warm surface layer nearer the equator and facilitates cold water upwelling on the eastern margin of the Pacific Ocean. It is speculated that this is the straw that pushes climate over thresholds. The idea is likely to remain speculative for some time given limitations to scientific knowledge of complex and dynamic systems. Failure to recognise the chaotic nature of the Earth system is, however, the root of an impossible climate certainty.
It is quite impossible to quantify natural and anthropogenic warming in the 20th century. The assumption that it was all anthropogenic is quite wrong. The early century warming was mostly natural – as was at least some of the late century warming. It seems quite likely that a natural cooling with declining solar activity – amplified through Pacific Ocean states – will counteract rather than add to future greenhouse gas warming. A return to the more common condition of La Niña dominance – and enhanced rainfall in northern and eastern Australia – seems more likely than not.
I predict – on the balance of probabilities – cooler conditions in this century. But I would still argue for returning carbon to agricultural soils, restoring ecosystems and research on and development of cheap and abundant energy supplies. The former to enhance productivity in a hungry world, increase soil water holding capacity, improve drought resilience, mitigate flooding and conserve biodiversity. We may in this way sequester all greenhouse gas emissions for 20 to 30 years. The latter as a basis for desperately needed economic growth. Climate change seems very much an unnecessary consideration and tales of climate doom – based on wrong science and unfortunate policy ambitions – a diversion from practical and measured humanitarian goals.