“ ‘Dangerous’ has become something of a cliché when discussing climate change." — climate researchers, writing in 2006 (Schneider and Lane, 2006). “Arctic climate change [is] centrally relevant to definition of dangerous human interference." — 2007 scientific paper (Hansen, Sato et al., 2007a)

What risk is acceptable in establishing “safe" global warming goals, policies and actions? In the absence of a well-informed scientific consensus that harm would not ensue, the precautionary principle suggests that if an action (or inaction) might cause severe or irreversible harm to the public or the environment, the burden of proof falls on those advocating the action (or inaction). For nuclear power stations in the USA, the regulatory standard is that there should be no more that one-in-amillion risk of serious accident. In 2004, the chance of being killed in a commercial air crash was about one in four million. If instead the risk was one in a thousand — a 0.1% chance — we would not fly.

Yet we seem to accept much higher risks as reasonable in setting global warming targets. The talk is about a 20–30% species loss for a rise of 2°C, very likely coral reef destruction, possible ice-sheet disintegration and the prospects of economic damage “on a scale similar to those associated with the great wars and the economic depression of the first half of the 20th century" (according to Nicholas Stern) as if it were a game of chance, a poker hand where with an ounce of luck the right cards will be dealt and the Earth will “get out of jail" free.

It seems that we abide by one rule when our own personal safety is at risk, but apply a much lower standard when it comes to the planet on whose good grace our own survival rests. The precautionary principle tells us to not risk actions that could trigger an irreversible chain of climate change events or produce dangerous impacts. We cannot gamble on how far we can push the system till it breaks, and then try and unscramble the eggs. As is the case for civil aviation, climate change safety policy must allow for less than a one-in-a-million chance of catastrophic failure. Because biodiversity, our lives, and those of succeeding generations are at stake, we must not choose to accept a level of warming that creates an unacceptable risk of unacceptable impacts. We need a model of the precautionary principle that not only guides us to avoid unsustainability, but that also guides us to get back to the safe zone if we have strayed outside that zone already.

Yet risk and uncertainty have been turned on their head: “The risk-averse nature of Article 2 of the UNFCCC (UN Framework Convention on Climate Change) requires immediate and stringent reductions in emissions of all greenhouse gases… because of scientific uncertainty, not in spite of uncertainty. Uncertainty, however, has been used as a reason for delay of emission reductions, presumably on the grounds that future knowledge may show that near-term emission reductions are unnecessary" (Harvey, 2007).

The 1992 UNFCCC urges stabilisation of greenhouse gases at a level: to “prevent dangerous anthropogenic interference with the climate system"; to be achieved within a time frame “sufficient to allow ecosystems to adapt naturally to climate change; to ensure that food production is not threatened; and to enable economic development to proceed in a sustainable manner". Climate ‘code red’: The case for a sustainability emergency 25 While the concept of “dangerous" is generally cast into the future — for example, at a 2°C rise — other judges, such as the inhabitants of low-lying Pacific islands, know it is already dangerous.

Suggested metrics for dangerous climate change (Schneider and Lane, 2006) include:

• risks to unique and threatened geophysical or biophysical systems;
• risks associated with extreme weather events;
• total damages;
• temperature thresholds to large-scale events;
• risks to global and local ecosystems;
• loss of human cultures;
• ‘millions at risk’ — the additional number of millions of people placed at risk;
• the five key sustainability metrics: water, energy, health, agriculture, and biodiversity;
• impacts at a pace beyond the capacity to adapt;
• triggering of an irreversible chain of events;
• early warning dangers present in certain areas that are likely to spread and worsen over time with increased warming; and
• distributional metrics: inter-country equity, intergenerational equity, and inter-species equity.

Schneider and Lane (2006) also propose five measurements:

• market costs in dollars per tonne of carbon (C);
• human lives lost in persons per tonne C;
• species lost per tonne C;
• distributional effects (such as changes in income differentials between rich and poor) per tonne C; and
• quality of life changes, such as heritage sites lost per tonne C or refugees created per tonne C.

And they note their “strong belief that such broad-based, multi-metric approaches to impacts categorization and assessment are vastly preferable to focusing solely on market categories of damages, as is often done by traditional cost–benefit analyses. ‘One metric’ aggregations probably underestimate the seriousness of climate impacts." Pragmatically, there will be no easy agreement between nations as to what the definition of dangerous will be, nor will quantities or caps be established. But the effort must be made to get a genuinely ‘good enough’ consensus because the stakes are so high.

Of particular significance as a metric is the triggering of irreversible chains of events, or “tipping points". The climate system “is highly non-linear and is prone to abrupt changes, threshold effects and irreversible changes (in a human time frame)… very small changes in a forcing factor can trigger surprisingly large and sometimes catastrophic changes in a system… [and] propel the Earth into a different climatic and environmental state. Examples include the rapid disintegration of the large ice sheets on Greenland and Antarctica or large-scale and uncontrollable feedbacks activation of methane in the carbon cycle: activation of methane clathrates buried under the coastal seas, the rapid loss of methane from warmer and drier tundra ecosystems, increasing wildfires in the boreal and tropical zones, the conversion of the Amazon rainforest to a savannah and the release of CO2 from warming soils. Once a critical threshold was crossed and such a series of processes was triggered, no policy or management approaches could slow or reverse the process" (Steffen, 2007). An example is the “imminent peril" we now face of “initiation of dynamical and thermodynamical processes on the West Antarctic and Greenland ice sheets that produce a situation out of humanity’s control, such that devastating sea level rise will inevitably occur" (Hansen, Sato et al., 2007b).

“A tipping point occurs when the climate state is such that, because of large ‘ready’ feedbacks, small additional forcing can cause large climate change. The ready feedbacks today are provided by Arctic, the West Antarctic ice sheet, and much of the Greenland ice. Little additional forcing is needed to trigger these feedbacks because of global warming that is already in the pipeline… Casualties of passing this tipping point would include more than wildlife and indigenous ways of life in the Arctic, and the coastal environments and cities submerged by rising seas. The increased global warming Climate ‘code red’: The case for a sustainability emergency 26 would have world-wide effects via an intensified hydrologic cycle…" (Hansen, 2008). Thus “tipping points is not only a valid concept, but it is what distinguishes the global warming problem from other problems such as the (particulate) air pollution problem… the upshot is a real danger that the system will run out of our control [and] these changes will become unavoidable. As we realized years ago, we cannot ‘wait and see’ in the climate problem. We have to be smart enough to understand what is happening early on" (Hansen, 2007d).

So what does it mean to “prevent dangerous anthropogenic interference with the climate system"? We suggest the goal is a climate safe for all people and all species over “all" generations, and we should not discount knowable impacts beyond our own lifetime. The world has already overshot this goal. We have already moved beyond a safe-climate planet and global warming is now causing species extinction and taking a toll in human lives. So how much damage from climate change are we prepared to tolerate? We can only answer “the least amount possible" and certainly not levels that will overwhelm human and other species’ capacity to cope. One has only to read or watch day-by-day reports in the media to understand that dangerous climate change is already here. Looking at Darfur, the farmers along Australia’s failing Murray–Darling river system, collapsing ecosystems, the victims of the 2007 Greek and Californian mega-fires, the coral stress, the species lost, the changing patterns of the Asian monsoons, the fate of low-lying Pacific island communities and food production decline in sub-Saharan Africa, our world is already at the point of failing to cope. The United Nation’s emergency relief coordinator, Sir John Holmes, warned that 12 of the 13 major relief operations in 2007 were climate related and said this amounted to a climate change “mega disaster" (Borger, 2007). Climate change is already dangerous.

The complete report including the section on Dangerous Climate Change is available online at: Climate Code Red