Misc on January 22, 2013
It’s been a bit of a tradition to start a new Climate Radio series with a programme about the science. The idea is simply to give a foundation to everything that follows. It’s not always easy to look the science straight in the face and see what it’s telling us. The scale of the challenge can lead to denial and a sense of disempowerment. But unless we correctly assess the problem we face, we will continue to come up with inadequate solutions.
Our two guides to what’s happening in the Arctic are Professor Peter Wadhams, Head of the Polar Ocean Physics Group at Cambridge University and Professor Timothy Lenton, the award-winning Chair in Climate Change and Earth Systems Science at University of Exeter.
The Arctic: The Canary in the Climate Coal Mine
In the absence of urgent action on climate change, there may be a number of tipping points in climate-driven systems in the Arctic, which threaten to rapidly escalate the danger for the whole planet. A collapse of summer sea-ice, increased methane emissions from thawing permafrost, runaway melting of the Greenland ice-sheet, and a collapse of the thermo-haline circulation, may all be approaching in the Arctic and will have disastrous consequences for global climate and sea levels. These together comprise a wake-up call to reinvigorate efforts to tackle climate change. A lack of consensus on precisely how fast any tipping points are approaching in the Arctic should not be used as an argument for inaction. (Environment Audit Committee, Protecting The Arctic, September 2012, p.21).
Arctic Sea Ice
The Arctic is warming between two and four times the global average (Lenton, Feb 2012) and new data from the CryoSat 2 satelliteconfirms that Arctic sea ice is declining faster than most climate models predicted.
Initial analysis of the data in August 2012 by the late Professor Seymour Laxon suggested that there was a 50% decrease in volume from 2003-2011 (EAC, p.16), while analysis of ice thicknes data obtained by from submarine sonar measurements by Professor Wadhams suggests that the volume of sea ice has declined by about 70% over the past 30 years.
Professor Wadhams has predicted that the Arctic could be free of sea-ice in the summer as soon as 2015. The Environment Audit Committee (EAC) concluded that there was “new evidence that the ice-cap is thinning faster than previously thought [and that therefore] the general view that the ice-cap is not at risk of summer collapse in the next few years may need to be revisited and revised” (EAC, p.16).
The government in its response said that “the Arctic may become essentially sea-ice free for some days or weeks in most summers” as early as 2030 (HC 858, p.2). Is the trend in volume decline turning exponential or are recent observations just anomalies waiting to be explained? See the ongoing work on this by PIOMAS. Lenton’s research indicates that Arctic Sea Ice passed a tipping point in 2007.
As the sea ice retreats it increases warming regionally, as the open water absorbs more heat than the former ice cover.
Greenland Ice Sheet
Greenland ice sheet melt is a crucial tipping point in the climate system which has the potential to both accelerate local and global warming and eventually add 6-7 metres of sea level rise globally. Work published in 2012 indicates we are now within the estimated range (0.8C-3.2C of global average warming) for tipping the Greenland ice sheet into irreversible meltdown – although a 2008 assessment suggested this process itself could take hundreds of years to complete.
Observations show that the Greenland ice sheet has been losing mass at a rate that is accelerating. In 2012, in an event unprecedented in 30 years of satellite observation, “an estimated 97 percent of the ice sheet surface thawed at some point in mid-July.” In July also, an area “twice the size of Manhattan” broke away from Greenland’s Petermann glacier.
The dynamics of Greenland ice sheet melt have been poorly understood and inadequately dealt with by computer climate models.
Atlantic Thermohaline Circulation
New evidence appears to suggest that freshwater from Greenland ice melt may be weakening the Atlantic thermohaline circulation – the ocean current which includes the Gulf Stream and brings warm water to the Arctic (EAC, p.20), although it may not “switch off” completely for several decades.
Methane is around 23 times more potent a greenhouse gas than carbon dioxide, though it has a shorter lifespan in the atmosphere.
There are several potential sources of methane in the arctic: on-shore permafrost (which turns into wetland as it melts); subsea permafrost on coastal shelves; and methane hydrates which are locked up on the deep ocean floor.
Wadhams says that about one third of the Arctic is continental shelf. He says satellite measurements show this shallow water is warming up to seven degrees in the summer and that this has the potential to melt the sub-sea permafrost and release a large amount of methane. This already appears to be happening. Parts of Arctic Siberia are releasing ten times more carbon into the atmosphere than previously thought, from sources that are tens of thousands of years old and contain twice as much carbon as is currently in the atmosphere as CO2.
Arctic Warming, The Jet Stream and Extreme Weather
New evidence is emerging of the possible link between Arctic warming and extreme weather in the mid Northern latitudes. As the Arctic warms faster than the global average, the temperature difference between the Arctic and the equator decreases and this appears to be slowing atmospheric currents known as Rossby waves and destabilising the associated Jet Stream. This could be linked to extreme and prolonged weather patterns in the mid Northern latitudes such the heat waves, drought, flooding and cold spells. SeeFrancis & Vavrus, 2012. Climate scientists are always more confident if they have a set of observations spanning a longer time frame – something not possible when a new, unforeseen trend starts to emerge and when there is a large degree of annual variability – so there is inevitably some debate around this.
According to the Arctic Council, the effects on marine animals and birds of a warming Arctic are likely to be “profound”. For a discussion of these impacts see EAC, p.11-13. The EAC does not discuss the impact on the region’s four million human inhabitants. Listen to this two-part Climate Radio special from 2009 on how Arctic First Nations peoples are finding their traditional lifestyles increasingly difficult to follow, and have been at the forefront in the struggle to stop oil and gas development in their territories, winning many important victories.
Most of the Arctic systems discussed above contribute to accelerated warming both locally and globally . The slowing down of the Atlantic Thermohaline Circulation on the other hand will contribute to a regional cooling.
Peter Wadhams assertion that we would be committed to 2C of average global warming (relative to pre-industrial times) even if we stopped burning fossil fuels tomorrow is not immediately borne out by the two 2005 studies that he says were his reference. These say we would be committed to adding 0.5C to the 0.8C of warming that we’ve already seen. But if we bear in mind that these studies are now seven years old (over which time we have continued to increase the amount of CO2 in the atmosphere) and that the processes and rates of change we are now seeing in the Arctic (and probably elsewhere in the global climate system) are not likely to be well accounted for in their models, then it is conceivable that the authors might be revising their results upwards if they ran their experiments today.
If you know about more recent papers on “committed warming” please get in touch or leave a comment.
Tim Lenton makes the point that the definition of ”dangerous” warming probably lies below 2C.
The 2007 IPCC report (regarded as the mainstream science and used to guide international policy discussions under the UNFCCC) already noted that dangerous impacts were more likely to happen at lower temperatures than assumed by their previous report in 2001. A graphic representation of this information was included in the draft 2007 report but, according to the New York Times, was kept out of the final report by various government officials. The missing “embers” diagram was later published as a peer-reviewed paper in PNAS where it is easy to compare against the version included in the 2001 report.
In this Climate Radio programme of August 2009 , you can hear IPCC Vice Chair, Jean-Pascal van Ypersele urging the European Commission to review the 2C targret (already 13 years old at that point) in the light of the 2007 IPCCC report. He asks the same question towards the end of his power-point presentation.
Lenton – in his 2012 evidence to the EAC – says that the Arctic is already fulfilling the five criteria that the IPCC have listed for defining ”dangerous climate change” (EAC, p.95).
Time for Geoengineering?
If we are already at a level of average global warming that is dangerous, and the concentration of greenhouse gases in the atmosphere commits us to a further 0.5C or more – even if we stopped burning fossil fuels tomorrow – is it time to consider geoengineering?
Two days after this programme was originally broadcast, Professor Wadhams and the Arctic Methane Emergency Group submittedfurther written evidence to the EAC urging the government to
“adopt a precautionary approach by funding the preparation of equipment for cooling action to slow the melt of sea ice this summer, should the sea ice show signs of decline with respect to 2012, as we expect and fear. Apart from field trials, we suggest that no significant deployment need be considered until the evidence is clear that such deployment is necessary to halt a further decline in sea ice … The most favoured technique involves the brightening of clouds using cloud condensation nuclei produced by spraying very fine droplets of sea water into the air from ships or islands. There do not appear to be any downsides to this technique except that it is not yet proven to be effective as may be required. The readiness to deploy a combination of several techniques is most desirable, to maximise the chances of success.”
Neither Lenton, the EAC nor the government were convinced that geo-engineering is an appropriate solution at this point, although Lenton sees a need for some form of enhanced action and is arguing for removal of CO2 from the atmosphere by planting trees or by chemical means, and for taking action on reducing soot pollution (also known as black carbon). These options in themselves beg further questions.
This show is dedicated to the late Professor Seymour Laxon who died tragically on New Year’s Eve 2012. Our thoughts are with his family and friends.