Andrew Glikson, earth and palaeoclimate scientist at the Australian National University, writes: Professor Hans Joachim Schellnhuber, chief climate science advisor of the German government and keynote speaker at the Four Degrees or More? Australia in a hot world conference held this week in Melbourne, made a point on Lateline that even the least-informed should be able to understand: “Our body temperature is about 37 degrees. If you increase it by two degrees, 39, you have fever. If you add four degrees, it is 41 — you are dead, more or less. And you have to think about the body temperature of our planet, which has been brought about through many, many processes over many, many millions of years.”
Global emission reduction targets — ranging from Germany’s 40% aim relative to 1990 to Australia’s 5% aim relative to 2000 — would still allow mean global temperatures to rise to +3 and 4 degrees Celsius later in the century, driving a major shift in climate zones. Schellnhuber emphasizes the non-linear nature of climate change where, once critical temperature thresholds are crossed, warming is amplified by feedbacks from melting ice, opening of water surfaces, release of methane from permafrost and from polar sediments, leading to tipping points.
According to projections by NASA scientists James E. Hansen and Makiko Sato: “… goals of limiting human-made warming to 2°C and CO2 to 450 ppm are prescriptions for disaster. They continue: “Deglaciation, disintegration of ice sheets, is nonlinear, spurred by amplifying feedbacks… Gravity satellite data, although too brief to be conclusive, are consistent with a doubling time of 10 years or less, implying the possibility of multi-meter sea level rise this century.” As their abstract concludes, “Rapid reduction of fossil fuel emissions is required for humanity to succeed in preserving a planet resembling the one on which civilization developed.”
The disruption of the carbon and oxygen cycles, which act as the ‘lungs of the biosphere’, has raised CO2 and other greenhouse gases to levels close to that of 16 million years ago — The Mid-Miocene — and is proceeding at a rate of ~2 ppm per year, unprecedented in geological history, with the exception of global volcanic and asteroid impact events which led to mass extinction of species.
The extreme rise rate of greenhouse gases retards the ability of species to adapt to fast changing environments, threatening a mass extinction of species, not least in the oceans.
A fundamental change in the global climate regime ensues in a permanent state of the El-Nino, such as existed before 3 million years ago. At that stage the cessation of polar-sourced cold currents results in a stable equatorial warm pool and the demise of the La-Nina phase. An intensification of the hydrological cycle leads to extreme weather events, increasing around the world.
An acceleration in the rate of sea level rise from the current rate of near-3.5 mm per year is projected by increase melt rate of Greenland and Antarctic ice sheets. Research by polar scientists states: “If this trend continues, ice sheets will be the dominant contributor to sea level rise in the 21st century.”
According to leading Intergovernmental Panel on Climate Change (IPCC) authors the “climate change that takes place due to increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop.”
Whereas a ceiling on the rise in mean global temperature to 2 degrees Celsius is currently discussed, temperatures are already committed to a +2.3 degrees C rise, had it not been for the masking effect of sulfur aerosols and the transient cooling effect of the oceans.
The focus on economic considerations ignores the consequences for the economy of +3 to +4 degrees global temperature rise, the shift in climate zones, indicated by CSIRO research. A dumbing down of the political and media discussion to the dollar price of carbon reflects years of cover-up on the essential evidence. Had the science been afforded full publicity in the Australian media, the current fury regarding the price of carbon would be seen in its true perspective, namely in terms of the future of the atmosphere-ocean system.
In a world bent on extracting all available carbon resources — coal, oil, oil shale, tar sand, gas, a phony discourse has ensued between those willing to undertake only symbolic action and those who deny the science altogether. The window of opportunity to turn the climate trend would close unless a coordinated global effort is made to reduce emissions and a technological breakthrough is made to draw-down atmospheric CO2.
According to Schellnhuber “We are simply talking about the very life support system of this planet.” What is required is what has never been done before in human history — a plan for the future.