The concept of irreversibility in the context of climate change is semantically ambiguous in that it has a different meaning in scientific and public policy discourse. In scientific discourse, the question of irreversibility depends on the different observed phenomena and on the time scale of observation. The current prevalent estimate is that global-scale warming will persist for thousands of years, depending on the level of CO2 emissions while the sea level rise associated with the warming will persist even longer. Compared to the time scales on which societies plan and conceive information, this time scale could be said to be effectively irreversible.
Solomon et al., define irreversibility in the following way: “Future carbon dioxide emissions in the 21st century will hence lead to adverse climate changes in both short and long time scales that would be essentially irreversible (where irreversible is defined here as a time scale exceeding the end of the millennium in year 3000.”
In public discourse, the concept of irreversibility, together with attributes such as catastrophic, abrupt, tipping point, point of no return, etc. is used as a rhetorical device to express a sense of urgency and to stimulate the advance of particular policies. It is, in effect, a risk communication strategy that aims to transform public perception of the long term processes of climate change (usually equivalent to low risk perception) into signaling immediate danger and consequently increasing public risk perception and influencing behavior. In scientific discourse, while rapidity and abruptness of change is acknowledged in events such as glacier retreat or melting Arctic ice, irreversibility is emphasized as likely but not considered definitive.
Not all public discourse is unanimous when it comes to the message of irreversibility for the purpose of defining a threshold for danger. Proponent arguments maintain that there is a lack of suitable sense of urgency in public opinion on the issue of climate change, which leads to a dangerous false sense of security. Those who argue against the so called alarmist rhetoric of irreversibility claim that it leads to fatalism and cynicism, manufacturing anxiety over the possibility that climate change could pose problems outside of human control or incapable of human solution. This, in turn, has been used to justify a comparison between the proponents camp and an un-scientific, religious “cultification “of the climate change debate. In reviewing the recent December 2009 Copenhagen summit, Caroline May – policy analyst for the National Center for Public Policy Research in the US – writes: “Faith is belief without verifiable evidence. This unquestioned adherence to the theory of Global Warming bears all the markings of what traditionally would be recognized as a religion. Complete with sin (the emitting of carbon dioxide), scriptures (Intergovernmental Panel on Climate Change assessment reports), commandments (drive a Prius, use Compact Florescent Light bulbs, do not eat meat etc.), indulgences (carbon offsets), proselytism, prophets (Al Gore), priests (scientists), prophecy and apocalypse (floods, hurricanes, dead polar bears), infidels (Warming skeptics), and salvation (the halting of carbon emitting industrial progress) the religion of Global Warming fits the mold.”
The concept of irreversibility is clearly laden with moral, political and psychological implications – areas traditionally in the realm of social debate. But as can be seen from the above Biblical analogy, it has also succeeded in bringing to the table the age-old dichotomy between science and religion, showing that in debates involving natural phenomena and natural hazards, God is far from having said his last word. This brings us back to the point of the role of science in the discourse of irreversible climate change. The question then arises should scientific writing use words such as irreversible, catastrophic, urgent and chaotic to denote climate change phenomena and some of their key impacts to avoid getting bad press with the popular press, and if not what are appropriate ways of communicating information about the degree of threat or changes in the public understanding of the threat without obscuring the message in scientific jargon that is inaccessible to non-scientists. The establishment of some standard criteria in the language of risk communication on (irreversible) climate change is, therefore, an important preliminary step in the concrete discussion on how we deal with the problem and its consequences as well as implications for policy. Failing the ability to find a common discourse, the climate change debate risks the doom of silence as the fallen tower of Babel.
In the paper “Irreversible climate change due to carbon dioxide emissions” Solomon et al. offer a quantitative analysis of carbon dioxide concentrations that have already occurred or could occur in the coming century, implying that dangers related to climate change are already irreversible (according to their scale) and argue that policies about discount rates of economic trade-offs are not a sufficient mitigation mechanism precisely because they ignore the issue of irreversibility. They make a similar claim with regard to the efficacy in trading greenhouse gases on the basis of 100-year estimated climate changes, pointing to the significantly longer term effects of carbon dioxide. Yet while exposing these alleged policy shortcomings, they stop short of offering different policy recommendations.
As an economic problem, it is important to consider implications of climate change on national and international policy decisions about the control of greenhouse gas emissions or investment in measures to reduce the cost of change. The main policy response options for climate change are mitigation or adaptation. Mitigation usually refers to action that reduces the cost of an event thereby implying action before the event. Adaptation, on the other hand, may involve actions taken before, during or after the event, and usually implies actions that reduce the expected damage (e.g. adoption of building standards that minimize earthquake damage), but it also includes actions that pool or transfer the risk of an event (e.g. insurance). Perrings argues that action as a result of a mitigation policy is only possible under the assumption that mitigation will affect the probability of climate change, i.e. the acknowledgment that anthropogenic emissions of green house gases significantly contribute to climate change and that consequent reductions in their concentration would yield a favorable outcome. Examples of mitigation policies include carbon and other energy taxes, energy policies to reduce dependence on fossil fuels, multilateral environmental agreements to reduce emissions (FCCC, Kyoto), and actions to increase absorption of CO2 (afforestation).
Adaptation, on the other hand, is a defensive strategy of reducing the cost of climate change if it happens. Examples of adaptation include construction of coastal and estuarine defenses to adapt to sea-level rise; strengthening or relocation of infrastructure and industrial, commercial or domestic structures to adapt to the increased threat of storm damage; the relocation of threatened populations; and the use of financial instruments to spread the risks of climate change through insurance, securitize the risks (e.g. catastrophe bonds) or reduce the cost of adaptation.
According to Perrings, the optimal balance between mitigation and adaptation as response options to the prospect of climate change depends on their relative costs and benefits. While adaptation is shown to substantially lower the cost of climate change at the global level, it may not be an affordable strategy for many low-income countries which are disproportionally affected by extreme climatic events such as hurricanes, cyclones, storms, floods and droughts not so much because of their geographic location as their limited coping capacity and poor or non-existent infrastructure.
Another policy strategy of consideration, which is particularly salient under conditions of uncertainty, potential irreversibility and generally unknown outcomes, is the so called precautionary approach. Essentially, it advocates the commitment of resources to safeguard against low probability high impact events while ‘buying time’ for the decision-makers until further evidence becomes available. A characteristic of such low probability high impact events is that they often lack historical precedents, which makes it difficult to back up decisions by quantitative analysis. Identifying knowledge gaps is, therefore, a preliminary task of a precautionary approach.
Finally, it should be acknowledged that the choice of strategy for policy-makers is dependent on political circumstances at national, regional and international levels. National policy responses tend to focus on adaptation measures. Under conditions of higher uncertainty and more abrupt climate change and extreme events, the pressure might increase to put more focus on mitigation or at least precautionary strategies. However, since mitigation of climate change is a global issue, a successful implementation of a mitigation strategy will necessitate global cooperation. As demonstrated at the Copenhagen summit in December 2009, such global cooperation is at present a mirage; hence adaptation remains the only current realistic alternative.