by Jack Rosebro
|Global 2ºC maximal warming limit as compared to past and present temperatures, as well as temperatures projected for various IPCC reference emissions scenarios, 2000—2100. Inset box represents instrumental records. Source: WGBU. Click to enlarge.|
From the opening day of the United Nations Framework Convention on Climate Change (UNFCCC) climate negotiations in Copenhagen, also known as Conference of Parties (COP) 15, the relevance of a key threshold metric—the 2 °C maximal warming limit, or “guardrail”—has repeatedly been called into question by delegates of COP member states which are particularly vulnerable to climate change. The dispute has contributed to a significant split among the primary bloc of developing countries, and has highlighted an increased focus on climate adaptation strategies, in addition to emissions reductions, during the talks.
The prevailing position up to now is that society may be able to avoid the most catastrophic effects of climate change by limiting average warming of the Earth’s lower atmosphere to no more than 2 ºC (3.6 ºF) above pre-industrial temperatures. A maximum concentration of 450 ppm carbon dioxide (~550 ppm CO2 equivalent) in the Earth’s atmosphere is commonly cited as the limit at which average temperatures can be held at 2 ºC, and many emissions reduction proposals are based upon these two “upper bounds” targets.
The >2 Degree Target
The 2 ºC maximal warming limit was cited at the UN Conference on the Human Environment in Stockholm in 1972, and revisited several decades later, in 1995, by the Wissenschaftlicher Beirat Globale Unweltveränderungen (WGBU), Germany’s national advisory council on climate change. The Council of European Ministers adopted the limit as policy on behalf of the European Union in 1996, and the Intergovernmental Panel on Climate Change (IPCC) subsequently employed the limit as context in its Third Assessment Report (TAR), published in 2001. 
|“We [need to] wonder whether the sum of all likely fossil fuel demands in the early decades of the [21st] century might not greatly increase the emission of CO2 into the atmosphere, and by doing so bring up average surface temperature uncomfortably close to that rise of 2 °C, which might set in motion the long-term warming-up of the planet.”|
—Barbara Ward, René Dubos, Only One Earth, UN Conference on the Human Environment, 1972
While the IPCC had acknowledged by 2001 that historical greenhouse gas emissions had likely already committed some ecosystems to irreversible changes, the predominant view was that a 2 ºC warming limit would limit such changes to acceptable levels in most parts of the world, and that the collapse of large-scale ecosystems, now known as tipping elements, would be unlikely unless warming rose by 3 to 4 degrees.
However, a literature review of recent climate research, as well as the most recent IPCC climate assessment report (2007 Fourth Assessment Report, or AR4) , indicates that at least some of the rationale for a 2 ºC guardrail, or warming limit, as well as a peak atmospheric concentration limit of 450 ppm CO2, has failed to take into account key drivers of climate change, resulting in an underestimation of its potential effects at a given temperature.
The AR4 Synthesis Report acknowledged in 2007, for example, that “based on current understanding of climate-carbon cycle feedbacks, model studies suggest that stabilizing CO2 concentrations at, for example, 450 ppm could require cumulative emissions over the 21st century to be less than ~1800 [1370 to 2200] GtCO2, which is about 27% less than the ~2460 [2310 to 2600] GtCO2 determined without consideration of carbon cycle feedbacks.” [italics added]  A significant body of research subsequent to AR4, especially with respect to the resilience of natural carbon sinks, has suggested that carbon cycle feedbacks may be more potent than previously thought.
Yet the most significant issue surrounding the 2 ºC warming limit may be the perception among some negotiators that it represents the upper bounds of warming at which disruption of ecosystems and societies would be minimal. Such perception is at odds with most projections; for example, the International Scientific Congress on Climate Change suggested in March that while some societies might be able to cope with a “two-degree world” through aggressive adaptive strategies, impacts could be “significant” even below 2 ºC.
|Projected regional warming, assuming an average 2º C rise in worldwide temperatures, as compared to pre-industrial temperatures. Source: Met Office UK. Click to enlarge.|
Above that, climate-induced changes “will be difficult for contemporary societies to cope with, and are likely to cause major societal and environmental disruptions”, with capacities for adaptation rapidly declining, and the likelihood of social disruption increasing via food insecurity, water shortages, and health impacts. 
But no climate model projects a uniform warming of the Earth; a mean global warming of two degrees is likely to result, for example, in localized warming as low as 0.5 ºC in some areas, and as high as 6 ºC in polar regions. Research, projections, and observations also indicate that 2 ºC of warming could be much more detrimental, on average, to the ocean’s ecosystems than to those on land.
Yesterday UN Secretary General Ban Ki-moon, whose evening speech signified the beginning of high-level talks in Copenhagen, reignited frustrations among delegates from developing countries when he made it clear that he supported the 2 ºC target and no other, saying that “we may not be able to agree on anything” if multiple warming targets were to be seriously considered. 
|“The immediacy and scale of the reductions necessary to avoid anything below 4°C, and indeed the human and ecosystem implications of living with 4°C, are beyond anything we have been prepared to countenance.”|
—4 Degrees And Beyond Rationale Statement
Notwithstanding the two-degree focus in Copenhagen, many scientists have been researching the potential effects of an average 4 ºC (7.2 ºF) warming, which could lead to a 10-16 ºC warming at the Earth’s polar regions. Earlier this year, a “4 Degrees And Beyond” climate conference focused on such issues, the first conference to do so (earlier post).
The “4 Degrees And Beyond” conference was the second synthesis conference on climate change sponsored by the UK government in the present decade. The first conference, “Avoiding Dangerous Climate Change”, was held in 2005 at the Met Office in Exeter, and focused on pathways to climate stabilization at or below 2 degrees Celsius.
|Projected regional warming, assuming an average 4 ºC rise in worldwide temperatures, as compared to pre-industrial temperatures. Source: Met Office UK Click to enlarge.|
The > 1.5 Degree Target: Small Island States Take On The US, The UNFCCC, And The UK’s Met Office
The acceleration of warming indicators following the IPCC’s release of the Fourth Assessment Report three years ago has spurred calls from both science and policy circles to forgo the two degree guardrail in favor of emissions reduction strategies that would yield an even more stable climate. The most popular maximal warming target to date has been 1.5º C or less, most prominently promoted by the 350.org website.
In the political arena, the 1.5 ºC target has been advanced by the Alliance of Small Island States (AOSIS), which passed a September declaration  calling on UNFCCC member states to adopt emissions cuts in Copenhagen that would peak greenhouse gas concentrations by 2015 and then stabilize them at 350 ppm CO2 equivalent by mid-century, requiring an effective decarbonization of developed countries by 2050.
|“My guess is that if the same European Ministers who decided, thirteen years ago, that the target ought to be 2 °C would look at the evidence in the last IPCC report, they would have to conclude that a lower target, probably 1.5 °C, is warranted.”|
—Jean-Pascal van Ypersele, Professor of Climatology and Environmental Sciences, Université Catholique de Louvain (Belgium), Vice-Chair of the IPCC
On Tuesday, 8 December, just a day after the Copenhagen talks had commenced, journalists attending an informal briefing in Copenhagen reported that US deputy special climate change envoy Jonathan Pershing—who served as a lead author of the IPCC’s Fourth Assessment Report—had dismissed calls to stabilize atmospheric carbon dioxide levels at 350 ppm, or about ten percent below current levels, indicating that such a target may already be out of reach. Quipping “We’re stuck”, Pershing forecast that world governments would instead have to adopt aggressive climate adaptation strategies. 
The next day, Tuvalu, a nine-atoll country with a population of about twelve thousand, briefly took the spotlight in session when it called for a suspension of negotiations after COP President Connie Hedegaard refused to accept an amendment that would seek to stabilize greenhouse gases at the levels laid out in September’s AOSIS declaration—essentially, the levels that Pershing had rejected.
Although conference leaders soon found a workaround and suspended only the agenda point in question, the proposed amendment split the normally unified G77 + China bloc of developing countries, with least developed countries supporting the amendment and emerging economies firmly against it.
|“Madame President, this is not an ego trip for me. I am merely a humble and insignificant employee of the environment department of the government of Tuvalu... We’ve had our proposal [for an agreement that would bind all countries to emissions cuts in service of a 1.5º C warming limit target] on the table for six months. Not the last two days.”|
—Tuvalu delegate Ian Fry, addressing Connie Hedegaard, Danish Environment Minister and President of COP 15
A BBC article  upped the stakes on Thursday the 9th with an article on carbon emissions that characterized “the lower target of 1.5 ºC favored by some developing countries” as “virtually impossible”, according to Met Office (UK) research. The article was countered the next day by an AOSIS statement that its proposed mitigation path would be expected to temporarily result in average temperatures of slightly more than 1.5 ºC at peak, yet stabilize them at the target by the end of the century.
By Saturday, however, an emotional but fruitless plea from Tuvalu delegate Ian Fry to President Hedegaard reflected the lack of support among member states for an agreement which would require all signatory countries to curb emissions.
“Reasons For Concern” About Climate Adaptation
Discussions of practical or appropriate emissions targets at COP 15 have been further complicated by the difficulty of assessing society’s ability to adapt to the effects of climate change. Research on human responses to climate change has so far been largely focused on efforts to mitigate the amount of future emissions, as opposed to adaptive actions.
In an essay published in the current issue of Environment and Planning A, researchers W. Neil Adger and Jon Barnett lay out four “reasons for concern about adaptation” to climate change, to counter “what we perceive to be a widespread belief that adaptation will be smooth, cheap, and easy to implement.”
Opportunities to adapt to the effects of climate change may be limited. “The scale of change and interconnectedness of impacts”, write the authors, “may be such that the window of opportunity for adaptation is smaller than previously imagined.” Given the failure of international GHG emissions reduction frameworks such as the Kyoto Protocol to produce meaningful results, as well as the projected rise of greenhouse gases in the future, “there will have to be a major turnaround in policy, planning, and behavior to avoid an atmospheric concentration that poses a significant risk of global mean warming of 2 ºC or beyond.”
Required rates of decarbonization with the potential to achieve a maximal average 2 ºC rise in worldwide temperatures, assuming peak years of 2011, 2015, and 2020. Source: WGBU. Click to enlarge.
Adding to the challenge is the envisioned rate of reduction of global greenhouse gas emissions after they peak, projected to be “many times greater in scale” than historical emissions reductions associated with economic downturns or technological breakthroughs. Although there has been a sharp uptick in research on the potential impacts of a global mean warming of 4 ºC or more, this “new realism about climate change... has yet to pervade thinking about adaptation.”
Adaptive capacities do not guarantee adaptation to climate change. Although developed countries are generally considered to have more resilience in the face of climate change as compared to developing countries, the apparent inability of developed countries to leverage existing adaptive capacity in the face of climate change, as indicated by their historical response to natural disasters, has been noted by researchers. Robert Repetto of the Yale School of Forestry and Environmental Studies argues in the seminal 2008 paper The Climate Crisis And The Adaption Myth  that adaptive responses to the effects of climate change can be either anticipatory or reactive, with anticipatory responses having the potential to mitigate the cost of adaptation.
“Unfortunately,” Repetto observes, “experience shows that in the United States, responses to disaster are mainly reactive, often characterized by inattention beforehand and over-response afterwards.” Reactive adaptation “would be likely to lag persistently behind the emerging risks”, with the resulting adaptive gap dependent in part on the rate at which temperature changes occurred.
Public and private bodies charged with adaptation have often failed, in Repetto’s assessment, to deal with present risks and emerging future risks. In storm preparedness, for example, New York City’s building codes and flood risk maps are based on historical and existing risks rather than projected future risks. Given that flood risks were clearly inadequate in Louisiana and New Orleans when Hurricane Katrina made landfall in August 2005, Repetto concludes that “to say that the United States can adapt to climate change does not imply that the United states will adapt”.
“Adaptation to climate risks may be punctuated, messy, more costly than we are willing to pay, and at odds with legitimate values and strongly held conviction concerning place and identity. The future will be a testing time.”
—W. Neil Adger and Jon Barnett, Tyndall Centre For Climate Change Research
However, some planning departments are incorporating adaptive measures into their recommendations. In Australia, for example, the Victorian Coastal Strategy of 2008  has recommended a policy of planning for sea-level rise of not less than 0.8 meters by 2100, and that policy be revised as needed.
“There are three adaption options: protect, accommodate, or retreat.”
—Victorian Coastal Council, 2008
Adaptive capacities may be undermined by unsustainable actions. Actions which are already in place, yet which are not sustainable, may well lead to “maladaptation”: a policy, for example, which secures water supply inefficiently, leading to the unnecessary production of greenhouse gases, when more efficient policies could be implemented.
Support for climate adaptation policies may be difficult to secure. Adger and Barnett reason that the relative success, failure, and trade-offs of adaptation to climate change can only be measured within a social context; policy which appears to be sound as an adaptive response may be rejected by those for whom it is designed to benefit.
“For example”, they point out, “the widely held idea that relocating populations from islands can save them from the likely impacts of climate change on morbidity and mortality must be set alongside the significance of islands and their local cultures to their inhabitants.”
Such issues have already been rendered acute in the Pacific island nation of Kiribati, which lost two uninhabited islets, Tebua Tarawa and Abanuea, to sea-level rise in 1999. Some of Kiribati’s water wells have become brackish with seawater, and one village has already been abandoned, delegation chief Betarim Rimon recently told the Associated Press. In addition to short-term measures such as seawall construction, he said, the nation has a midterm plan to consolidate its population of 110,000, now spread across 32 atolls, on three islands that would be raised up if international aid could be secured.
“Nobody in this room would want to leave their homeland,” Kiribati’s foreign secretary Tessie Lambourne, commented last week at a side event in Copenhagen. “It is our spiritual connection to our ancestors. We do not want to leave our homeland.” 
 Jean Pascal van Ypersele, Climate Change Reality : 1.5 or 2 degrees Celsius? Life or death for Tuvalu? 13 December 2009
 Richard Black: UK Met Office Warns Carbon Emissions Must Peak By 2020. BBC, 10 December 2009