The 2 Degree Target is
Far Too High
A global warming limit of 2°C has become an almost
universally accepted "target," aimed for by national and international policy. A 2 degree target is disastrously high and is an invitation to global climate catastrophe. Wide degrees of uncertainty call for wide margins of safety.
And certainly a 450 parts per million (ppm) target for carbon dioxide is too high if we want to stay below the 2 degree target.
It is now generally acknowledged that anything above 350 ppm is a formula for a catastrophic temperature increase above 2 degrees.
Climate safety, therefore, is below 350 ppm (James Hansen et al, 2008) and is probably under 300 ppm, which has been the upper limit for atmospheric carbon dioxide over the past 800,000 years (according to the ice core data). To achieve climate safety, we might need to get back down to the pre-industrial CO2 level of 280 ppm (Hans Schellnhuber, 2008).
The oft stated goal to keep global warming less than 2ºC is a recipe for global disaster, not salvation.
— Dr. James Hansen, 2008
Why is the 2 Degree Target Too High?
The Earth's climate system is far more sensitive than we imagine. As marine biologist Donal Manahan explains, "If I heat up my body temperature by a couple of degrees, it's called a fever. And once it gets beyond a few degrees, I go into a coma." Indeed, a temperature increase of 0.78 in an infant or frail person could be cause for concern. Certainly a fever of +2ºC means something's wrong, and an increase of +5ºC or more can be fatal.
It is obviously vital to the future of humanity that we do not heat up the planet to temperatures that risk the catastrophes we know could happen.
And if (as is the case, we are sadly discovering) it is too late to avoid that risk, we must know what safe temperature we have to aim for and what safe atmospheric greenhouse gas level would get us there. Knowing what we know now, a 2 degree target is dangerously high.
The risks for worst-case outcomes amplify much more quickly than the risks for most likely outcomes. For an early and rapid decline in emissions, the worst-case outcome is around 0.7ºC higher than the most likely temperature rise. With much slower action taken much later, the difference between the most likely and worst-case outcome is almost twice as wide, at 1.2ºC. This takes a worst-case temperature rise of less than 3ºC to one just above 5ºC by the end of this century, bringing with it significant risk of dangerous impacts to our environment, society and economy.
A major reason for this amplification is the so-called 'carbon cycle effect'. Plants, soils and oceans currently absorb about half of the carbon dioxide emitted by human activities, limiting rises in atmospheric CO2 and slowing global warming. As temperatures increase, this absorption is very likely to decrease. For example, plant matter in the soil breaks down more quickly at higher temperatures, releasing carbon more quickly, and amplifying the warming trend. Methane released from the thawing of permafrost will add to the warming. This methane release is currently not included in the calculations, and becomes more of a risk for larger temperature rises.
Hence, the risks of dangerous climate change will not increase slowly as greenhouse gases increase. Rather, the risks will multiply if we do not reduce emissions fast enough.
— Dr. Vicky Pope, Head of Climate Change Advice, Hadley Centre, UK Met Office, October 2008
Where Did the 2 Degree Target Come From?
The 2ºC "target" is a politically (not scientifically) set target from the European Union (EU) that goes back to the mid 1990s.
Since then, although the weight of scientific evidence has increasingly shown that a globally averaged 2ºC temperature increase will be disastrous for humanity and much of life on Earth, the figure has stuck.
A safe limit was established at +1ºC even before 1990 (Villach Conference, 1987). The Avoiding Dangerous Climate Change conference in Exeter (2005) arrived at a limit of 1ºC (although acknowledging that dangerous climate change for developing countries is below 1ºC).
Many papers have been published over the years saying that 2ºC is too dangerous, and the precautionary weight of evidence is 1ºC to 1.5ºC. (These figures are now superseded by actual changes in the Arctic.)
The EU now acknowledges that a 2ºC global warming is not safe.
"[...] overall global annual mean surface temperature increase should not exceed 2°C above pre-industrial levels in order to limit high risks, including irreversible impacts of climate change; RECOGNISES that 2°C would already imply significant impacts on ecosystems and water resources. [...]" (2610th Council Meeting, Luxembourg, 14 October 2004)
At a 2005 meeting in Buenos Aires, the European Union addressed the question of what is dangerous climate change under the United Nations Framework Convention on Climate Change (UNFCCC). They came to the conclusion that dangerous global warming lies between 1.0ºC to 1.5ºC, thereby giving a safe limit of 1ºC.
The United Nations Environment Program (UNEP) has published a danger level of 1.5ºC based on 2007 IPCC data.
But these new figures have not been noticed, and the 2 degree target remains virtually the only limit cited in mass media and many scientific media.
What Has Been the Result of the 2 Degree Target?
This 2ºC target has helped to allow the delay in mitigation for so long that recent research now shows that we cannot avoid going over 2ºC.
It is now too late to get under a 2ºC global warming — without achieving virtual zero carbon emissions and embarking on artificial carbon sinking.
This adds to the imperative of the international emergency response. We have to plan for the next generations to be able to minimize the planet’s exposure to a 2ºC warming.
Return from 2 Degree Target to Climate Change Emergency Homepage