For a Future to be Possible
James Hansen / Nafeez Ahmed:
Fossil fuel addiction could trigger runaway global warming
Without full decarbonisation by 2030, our global emissions pathway guarantees a new era of catastrophic climate change
Triggering a runaway greenhouse effect
The world is currently on course to exploit all its remaining fossil fuel resources, a prospect that would produce a "different, practically uninhabitable planet" by triggering a "low-end runaway greenhouse effect." This is the conclusion of a new scientific paper by Prof James Hansen, the former head of NASA's Goddard Institute for Space Studies and the world's best known climate scientist. The paper, published by Philosophical Transactions of the Royal Society focuses less on modelling than on empirical data about correlations between temperature, sea level and CO2 going back up to 66 million years.
A planet mostly uninhabitable by humans
Given that efforts to exploit available fossil fuels continue to accelerate, the paper's principal finding - that "conceivable levels of human-made climate forcing could yield the low-end runaway greenhouse effect" based on inducing "out-of-control amplifying feedbacks such as ice sheet disintegration and melting of methane hydrates" - is deeply worrying. The paper desribes how global average temperatures under such a scenario could eventually reach as high as between 16°C and 25°C over a number of centuries. Such temperatures "would eliminate grain production in almost all agricultural regions in the world", "diminish the stratospheric ozone layer", and "make much of the planet uninhabitable by humans." Hansen et al. state:
Estimates of the carbon content of all fossil fuel reservoirs including unconventional fossil fuels such as tar sands, tar shale, and various gas reservoirs that can be tapped with developing technology imply that CO2 conceivably could reach a level as high as 16 times the 1950 atmospheric amount.
They calculate that there is "more than enough available fossil fuels" to generate emissions capable of unleashing "amplifying feedbacks" that could trigger a "runaway" greenhouse effect "sustained for centuries." Even if just a third of potentially available fossil fuel resources were exploited, calculations suggest, this scenario would still be guaranteed, meaning decisions we make this century will determine the fate of generations to come. Hansen continues:
Governments are allowing and encouraging fossil fuel companies to go after every conceivable fuel, which is an obtuse policy that ignores the implications for young people, future generations and nature. We could make substantial parts of the Earth uninhabitable.
Hansen's stark conclusions
Most remaining fossil fuel carbon is in coal and unconventional oil and gas. Thus, it seems, humanity stands at a fork in the road. As conventional oil and gas are depleted, will we move to carbon-free energy and efficiency - or to unconventional fossil fuels and coal? ... It seems implausible that humanity will not alter its energy course as the consequences of burning all fossil fuels become clearer. Yet strong evidence about the dangers of human-made climate change have so far had little effect. Whether governments continue to be so foolhardy as to allow or encourage development of all fossil fuels may determine the fate of humanity.
The Hansen paper is just the latest confirming that we are on the verge of crossing a tipping point into catastrophic climate change. Other recent scientific studies show that the current global emissions trajectory could within three years guarantee a 2ºC rise in global temperatures, in turn triggering irreversible and dangerous amplifying feedbacks.
More emerging scientific evidence
According to another scientific paper given at the Geological Society of London this year, climate records from Siberian caves show that temperatures of just 1.5ºC generate "a tipping point for continuous permafrost to start thawing", according to lead author Prof Anton Vaks from Oxford University's Department of Earth Sciences. Conventional climate models suggest that 1.5ºC is just 10-30 years away. Permafrost thawing releases sub-ice undersea methane into the atmosphere - a greenhouse gas twenty times more potent that carbon dioxide. In June, NASA's new five-year programme to study the Arctic carbon cycle, Carbon in Arctic Reservoirs Vulnerability Experiment declared:
If just one percent of the permafrost carbon released over a short time period is methane, it will have the same greenhouse impact as the 99% that is released as carbon dioxide.
Yet another new paper suggests that conventional climate modelling is too conservative due to not accounting for complex risks and feedbacks within and between ecosystems. The paper just published in the premier journal Nature finds that models used to justify the 2ºC target as a 'safe' limit focus only on temperature rise and fail to account for impacts on the wider climate system such as sea level rise, ocean acidification, and loss of carbon from soils. It concludes that the 2°C target is insufficient to avoid dangerous climate change.
The problem is that our current global emissions trajectory already commits us to a 2ºC rise anyway. Papers published by the Royal Society two years ago showed that emissions pledges would still put the world on track for warming anywhere between 2.5ºC and 5ºC. Amongst them, a UK Met Office study concluded that strong amplifying feedbacks - such as the oceans' reduced ability to absorb atmospheric carbon dioxide leading to further warming - could see us reach 4ºC as early as 2060. As Hansen explained in a recent interview:
"Four degrees of warming would be enough to melt all the ice... you would have a tremendously chaotic situation as you moved away from our current climate towards another one. That's a different planet. You wouldn't recognise it... We are on the verge of creating climate chaos if we don't begin to reduce emissions rapidly."
The conservative mainstream institution, the International Energy Agency (IEA) has found that with current climate policies in place, we are locked into a rise of between 2°C and 5.3°C. Two years ago, the IEA concluded that we had five years left to implement urgent energy reforms; after which we would no longer be able to avoid dangerous climate change. We are now three years away from that point-of-no-return.
Policymakers riding blind
To make matters worse, the IPCC's forthcoming Fifth Assessment Report, like its predecessors, will specifically exclude the permafrost carbon feedback from its projections. The implication is that policymakers are riding blind: we do not really know how close we are to a tipping point into catastrophe. But there is a solution. According to Hansen, we need to focus on a maximum target of 1°C:
"The goal of keeping warming close to 1ºC is to keep climate close to the Holocene range, thus avoiding any major amplifying feedbacks. The 1°C goal requires rapid phase out of fossil fuel emissions, which would require a rising carbon fee. To continue to burn every fuel that can be found is the opposite approach - they are day and night."
This kind of rapid fossil fuel phase-out was proposed to the British Parliamentary Environment Audit Committee last year in the form of complete decarbonisation of power by 2030. Unfortunately, a UK bill to that effect was narrowly defeated in the House of Commons this year. There is still hope - the bill is currently up for consideration by the House of Lords. If it eventually passes, Britain might still play a leading role in heralding the energy revolution that could help save the planet, while saving the UK itself up to £100 billion.
◊ Dr Nafeez Ahmed is executive director of the Institute for Policy Research & Development & author of A User's Guide to the Crisis of Civilisation, & How to Save It.
Publ. here 16.7.2013.