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New research may well point to the fact that recent warming has produced more reliable vintages but if we look at some of the indicators of what the rest of this century really heralds then the forecast for many regions, including Britain, becomes much less rosy.

Retrospective analysis: 1600 - 2000

Looking back at 400 yrs of wine harvest records may seem like a longtime and certainly enough to base a study of viticulture on, however, we know that for the last ten thousand years we have been in a relatively stable climate period with a certain range of temperature variability that we have not strayed outside of. Whenever we have come close to the boundary of that variability, it has represented great hardships and often death for many people.

 

spratt holocene variability opt
Scientists now tell us that we are leaving the stable ten thousand year period (called the ‘holocene’) and entering a new era driven by manmade climate, called the ‘anthropocene’. The great definer of this new epoch is the rising global mean temperature driven by the concentrations of greenhouse gases such as carbon dioxide, methane etc. that are the waste output from our industrial civilisation.

Prof Schellnhuber stillProfessor Schellnhuber talks about PIK's latest research proving we are in the 'Anthropocene': age of human driven climate

The Anthropocene: a new temperature epoch

Most of the reporting around this new paper on wine and climate change asserts that “if” temperatures continue to rise then there will be negative effects on viticulture. This “if” leaves the story somewhat open ended.

The scientific research that is looking at the rates of change and the projected temperature analysis point to dramatically higher temperatures. The IPCC have created what they call ‘Representative Concentration Pathways’ (RCP’s) which are scenarios that give an indication of temperature rise based on levels of CO2 emissions from human civilisation.

rcps slideChart showing IPCC 'Representative Concentration Pathways' (RCP's) and the current RCP of 8.5 that we are on

Currently we are on the highest and most dangerous RCP 8.5, with carbon emissions totalling around 40 billion tonnes each year. The recent news that global emissions actually stabilised in 2015 is terrific, but we still have to consider that CO2 is a long-lived greenhouse gas that takes over a thousand years to breakdown. This means that historic emissions give us a human contribution of about 1 trillion extra tonnes of greenhouse gases emitted from civilisation since the beginning of the industrial revolution.

We also have to add to this that the Earth’s climate takes a few decades to show signs of change as the huge carbon absorbing sinks, such as the world’s oceans and forests, are slow to respond at first, but once they pass a tipping point, are liable to flip from acting as a store of carbon, to being a carbon source. 

Once this happens the rate of atmospheric carbon emitted is amplified from non-human sources and, like turning a thermostat up, the world heats much faster.

IPCC Europe 2100SRES
IPCC Scenario (SRES A2) for temperature rise by 2100

Interrelated change - a different set of ‘key performance indicators’

Climate model data showing projected temperature rise for the rest of this century are known to be conservative in their forecasts, as they don’t include many complex amplifying feedbacks that occur when one change in the Earth system (manmade or otherwise) sets off another.

For example, there is a huge threat of amplified warming from the loss of Arctic sea ice, caused when the reflective frozen white ice cap thaws and is replaced with dark heat absorbing ocean. Given the size of the Arctic ocean and it’s global position in relation to exposure to the sun, the potential for heat absorption is comparable alone to the warming caused by greenhouse gas emissions.

There is also a threat of methane release both on land and from the shallow ocean, already witnessed in the Arctic region, that will further accelerate global heating.

Another is sea-level rise, already conservatively estimated to be 1metre by the end of this century but, as I have been told by a leading glaciologist, it could be double that, or even as high as 4metres, we just don’t know. 

Any global mean temperature rise over 2.5ºC has been shown by scientists to trigger a collapse of the planets forests. Dying forests mean more carbon released to the atmosphere, further amplifying warming, and also the end of one of our main sources of oxygen.

This graphic below clearly shows how global mean temperature over the last few decades has already shifted to a warmer world outside of the boundary of the natural distribution curve. To stop the temperature from continually rising there would need to be some countervailing force. Emissions reductions are often cited as being that countervailing force but they are just a step in the right direction, certainly not enough to stop temperatures rising in the succeeding decades.

hansen variability

As this distribution of summer temperature anomalies keeps moving to the right, the number of extreme weather events will continue to rise with a wide range of interrelated impacts. None of which will benefit wine growers or the rest of society at large.

Old world, new world - Growing wine in a vacuum

wine on its head turkey
A rise in temperature, combined with even 1metre of sea-level rise would exacerbate the stresses that are already placed upon the interrelated system of human civilisation, from the global economy right down to our own individual prospects. 

Despite such realities and the mounting evidence for what is occurring, it is always amazing to me that so many people in the wine world believe that viticulture will continue in a vacuum, barely scathed by the challenges that will engulf the rest of the world.

It is as if there is an idealised view that we’ll be popping corks of bubbly in Sussex, oblivious to food shortages due to the collapse in supply chains that will expose Britain’s shortfall and unpreparedness for what lies ahead.

This may all seem extreme but it is exactly the consequences we face from the trajectory of carbon emissions we have long ago set ourselves on. Those who say “we must cease emissions to stop global warming” conveniently forget the existing burden of 1 trillion tonnes of carbon that will continue to warm the planet over the succeeding decades (and centuries). Amplifying feedbacks are what many scientists fear we are close to, or perhaps are on the brink of triggering. Setting these in motion means temperature changes will be distinctly non-linear.

So I will end by reiterating one final point: analysing the last 400 years of wine harvest records maybe very interesting, but it would be wise to acknowledge that this time period represents less than 5% of a climatically stable period in the Earth’s recent history. The growing mass of climate data clearly show that the next 400 years will be nothing like it.

Nick Breeze has been interviewing climate scientists since 2010 and posting about wine since 2005. This article does not state viable human responses to climate change impacts because it is only intended as a response to the general reporting on the research paper, ‘Climate change decouples drought from early wine grape harvests in France’ published by Benjamin I. Cook & Elizabeth M. Wolkovich in the Nature Climate Journal, 2016. http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2960.html

List of graphics / rich media:

1. Spratt - chart of holocene variability
2. Schellnhuber interview - ‘Anthropocene’
3. RCP’s relating to temperature rises
4. IPCC 2000 - 2100 temperature rise graphic (European)
5. Hansen’s recent demonstration of a shift in climate variability over recent decades



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