Climate panel set to reiterate bleakest of messages
Greenhouse gas emissions steaming ahead at 3 per cent a year
Activists marching last year in Doha to demand action to address climate change – “Earlier this year, atmospheric carbon dioxide levels breached 400ppm, their highest levels in at least three million years.” Photograph: Mohammed Dabbous/Reuters
The Intergovernmental Panel on Climate Change is probably the largest international scientific and policy collaboration in history. Later this month the organisation, which is under the auspices of the United Nations, begins publication of its Fifth Assessment Report (AR5). More than 830 expert authors have contributed to this titanic project, with the final report running to thousands of pages.
You could, however, sum its findings up in just four words: “the world is defrosting”. This is how Prof Neville Nicholls of Monash University, Australia, put it. Human impacts, according to a leaked draft of the report, are changing the planet in ways “unprecedented in hundreds of thousands of years”.
Of course, we already know this, since its last report, issued in 2007 in a blaze of media publicity and political gesturing, set out the extreme dangers of a business-as-usual emissions trajectory for all life on Earth. Back then, the body warned the world’s leaders that we are now collectively supping at the last chance saloon.
Today, six years and a global recession later, instead of being reversed, greenhouse gas emissions are literally steaming ahead, at more than 3 per cent a year. “We’re heading rapidly in the wrong direction,” says Dr David Victor of the University of California.
Earlier this year, atmospheric carbon dioxide (CO2) levels breached 400 parts per million (ppm), their highest in at least three million years, representing an astonishing 30 per cent increase in the amount of this potent heat-trapping gas in the atmosphere in just 50 years. There is simply no historical analogue for changes on this scale happening so quickly. The time lag here is crucial. During the Pliocene epoch, fuelled by similar CO2 levels to today, global sea levels rose by a massive 20 metres.
This is only for starters. By mid-century, the world is on target to have doubled the pre-industrial levels of atmospheric CO2, to well over 500ppm. Global temperatures track CO2 levels closely, so we can expect average surface temperature rises of about two degrees by that time, with much more heating effectively “locked in” as a result of the climate system’s inertia being overwhelmed by what are known as positive feedbacks.
With this, the current 10,000-year interglacial period of generally mild, stable climate that allowed human civilisation and the agriculture that supports it to flourish will come to an abrupt end. To lock in this apocalyptic scenario requires nothing more than maintaining our present path just a short while longer. “The decisions we make in the next decade or so are decisions that will determine the fate of the planet for thousands of years,” says Prof Kerry Emanuel of MIT in Boston.
Oceans under assault
The oceans too are under assault. Acidification is “virtually certain” to increase, the organisation warns, and this “threatens the survival of entire ecosystems, from phytoplankton to coral reefs and from Antarctic systems . . . to many human food webs”. The scenario of acidified, oxygen-starved oceans teeming with jellyfish and almost nothing else is edging from science fiction to climate science fact.