Monday, November 17, 2014

Today's Global Warming is Well Within Historic Range !

''Today's global warming is well within historic range''         
  • US President Barak Obama vows action on climate change with the declaration "none can avoid the devastating impact of raging fires and crippling drought and more powerful storms".  
It was an appeal using rhetoric and not science because the most severe impacts of these natural disasters come from the challenge of managing increased population or changed population demands, not changes in the events per se.

Great fires are a regular feature of North American and Australian landscapes, and their human impact is worst when they reach housing or infrastructure built among trees, on the edge of bushland that has not been cleared by "cool" burn-offs.

Civilisations have been hit by droughts since the Nile delta drought of 4200 years ago destroyed Egypt's old kingdom, leaving the pyramids as witness. As global citizens, we still have much to learn about the management of water, it seems, whether in our Murray-Darling backyard or in the Sahel of Africa.

The term "powerful storms" summons up graphic images of Hurricane Sandy, which devastated New York - except it was no longer hurricane-strength when it, like a dozen others in written history, it struck.  But the Manhattan area it flooded contained huge areas of high-density development on reclaimed swamps, ponds and what was riverbed before civilisation drained, dozed and filled it to provide for the population of one of the world's greatest cities. When New York has absorbed the lessons from this, it will be able to pass on advice and technology to places such as Bangladesh.

In an antipodean antithesis of current political comment in Australia, London Mayor Boris Johnson mused in Britain's The Telegraph last week on the run of five cold snowy winters in London, and contemplated the theories of solar cycles as drivers of climate advanced by maverick astrophysicist Piers Corbyn, (photo left) and said he "wonders whether it might be time for government to start taking seriously the possibility, however remote, that Corbyn is right".

It is worth looking at some recent peer-reviewed science that points in such a direction.
A growing number of mainstream scientists agrees there is evidence for such cycles as drivers of climate change, although debate on causes and mechanisms is strong. By way of example, I note three recent papers that find evidence for long-term cycles influencing the Earth's climate.
Weichao Wu of the Peking University and colleagues studied sea-surface temperature records preserved in deep-sea sediments near Okinawa in the Pacific Ocean, and found evidence for multiple cyclic temperature variations over the past 2700 years.

The most interesting temperature peaks correspond to medieval, Roman and possibly Minoan warming periods of about 900, 1800 and 2500 years ago. The paper is significant in that it concludes that the current rate of global temperature change lies in the same range as that of those historical warming periods.

This suggests we have evidence that challenges current climate orthodoxy on two grounds, first by suggesting that such warming events were global not local European phenomena, and second that current warming is not unprecedented in the historical record.

While we read many claims by oceanographers of an increasing rate of rise in sea-levels associated with increased atmospheric carbon dioxide, an alternative interpretation of observed data is made in a recent analysis by Don Chambers (photo right) of the University of South Florida and colleagues. Chambers "Is there a 60-year oscillation in sea-level?" and shows evidence that the answer is probably yes.
poses the question:

I read his data and find it is arguable that the upswing of that oscillation is responsible for about half of the current 3mm/year rate of rise, leaving the background rate of rise at about 1.7mm, where it has been for 110 years.

Intergovernmental Panel on Climate Change lead author Stefan Rahmstorf, writing in the climate scientists' blogsite Real Climate this month, commented on whether the data supports an interpretation of cycles, or non-cyclic shifts associated with changes in aerosols and current increases in greenhouse gases. Rahmstorf concludes in favour of the latter but ends with the objective and open-minded comment "if the system (is cyclic), we'd expect the opposite. In 30 years' time we will know for sure."

Offering considered alternative interpretations on the significance of a carefully constructed set of observational data is the essence of scientific debate; either may be right and I would add that if Chambers is right, the accelerating rate of increase in sea-levels has topped out about now, and the 10mm a year rises needed to reach the feared "1 metre rise by 2100" are not going to happen.

A third work that may eventually prove immensely important in understanding cycles in climate change is a study by J.A. Abreu of the prestigious Swiss university ETH, with co-authors including Ken McCracken, Australia's 1995 Australia Science Prize winner  . Abreu reconstructs a history of solar sunspot cycles over the past 10,000 years from elemental isotopes created by cosmic rays impinging on the atmosphere, subsequently preserved in Greenland ice-core records.
Australia's 1995 Australia Science Prize winner

These records show a series of cycles ranging from 88 years to 504 years with longer cycles of 974 and 2300 years evident in later work now accepted for publication (subject to minor changes). Thus
we see that sun-spot cycles, which have been understood for centuries to influence our climate on an 11-year cycle, also have predictable longer-period cycles in the hundreds and thousands of years, and present a mechanism to explain observational data of the type given by Wu and colleagues.
The mechanisms of sun-spot, solar magnetic field and cosmic ray interactions are complex and will be intensely studied, but the associations illustrated here demand consideration when we seek to model our future climate.

The devastating impacts of extreme climate events of which Obama speaks have always been with us, and we have to expect that the human tragedies they bring will be exacerbated by growth in global population.

The Way I See It.....cycles in climate change imply our efforts should be targeted at mitigation of effects, not changing the climate. Spending billions of taxpayers money to reduce temperature by one or two degrees is a fools errand and starves an nation's economy for decades. The eradication of Green ideology and money spent on mitigation will be more fruitful.

It is my hope that scientists advising our politicians will include the rich literature represented here in their briefings to politicians - or alternatively, that politicians will demand it. And may there be a quorum of politicians who will say as does Boris Johnson (photo right) while contemplating the exceptional snow and icicles in Trafalgar Square: "I have an open mind."


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