Current Climate Mitigation Efforts not adequate
Radiative forcing is a measure of the influence a factor (say, a change in greenhouse gas concentrations) has in altering the balance of incoming and outgoing energy in the Earth-atmosphere system and is an index of the importance of the factor as a potential climate change mechanism.
A Very Inconvenient Truth
In their article ‘A Very Inconvenient Truth’ Charles H. Greene, D. James Baker and Daniel H. Miller discuss the reasons why the evaluation of the risks of climate change due to human activities by the Intergovernmental Panel on Climate Change (IPCC) is prone to underestimating the threats of global climate change.
According to Charles et al., the IPCC process is based on consensus building and the final reports are intended to inform rather than shape policy. Because of the conservative nature of this consensus-building process these reports can lead scientists and policymakers to underestimate the structural uncertainties and risks associated with several important but poorly understood threats to the Earth system.
The IPCC process tends to formalize the approaches employed by both climate and socio-economic modelers so that the discussions of scientists and policymakers frequently become fixated on certain numerical values. A fixation on numerical values, especially ones arrived at without a clear explanation of the uncertainties involved, can lead to policy discussions that overlook important aspects of risk. For example, in the attempts to regulate emissions to achieve a particular global green house gas (GHG) stabilization level, there is still considerable uncertainty about how to include a number of nonlinear processes in models that are important in determining climate sensitivity. In addition, even when one is satisfied with projections of the average global temperature increase, there remains considerable uncertainty in assessing the vulnerabilities of various natural and human systems to that increase. Without a better understanding of these vulnerabilities, it is difficult to assess potential climate threats quantitatively, especially those most relevant to risk management.
Current Climate Mitigation Efforts not adequate
In their article Charles et al., also point out that, based on the scientific findings listed below, scientists are of the opinion that climate mitigation efforts that focus only on reducing GHG emissions may be placing society on the hazardous path of having to adapt to dangerous climate change that mitigation efforts fail to prevent:
1) Warming in the pipeline: Warming in the pipeline corresponds to the growing gap between the observed value of average global temperature and the expected equilibrium value once various feedback mechanisms are taken into account. Based on this concept the scientists have arrived at the conclusion that, even if GHG emissions were to drop precipitously and concentrations were to stabilize at today’s levels (in fact GHG emissions have been increasing more rapidly during recent years), there will be an average global temperature increase of 2.4°C by the end of the century, a warming in excess of the European Union’s threshold for dangerous climate change which is 2.0°C.
2) Because there are physical limits on the rate at which new, low-carbon energy technologies can be deployed, even assuming that the proper financial incentives are adopted, emissions are unlikely to be reduced substantially for several decades. Therefore, we can anticipate that GHG concentrations will continue to rise for at least the first half of the twenty-first century before eventually stabilizing. Because of CO2’s long residence time in the atmosphere, the overall GHG concentration in the absence of anthropogenic sequestration efforts will stabilize for the next thousand years at a level that is approximately 40% of its peak enhancement over the pre-industrial period.
3) Researchers also conclude that the climate warming induced by elevated GHG concentrations is largely irreversible. Once atmospheric temperature reaches equilibrium at a certain peak-overall GHG concentration, it will not drop markedly for the next thousand years even as GHG concentrations decline. This irreversibility comes about because the atmosphere’s loss of heat to the ocean is even more gradual than its loss of CO2. The thermal inertia of the ocean, which is delaying the rate of climate warming today, will delay the rate of climate cooling in the future.
4) According to scientists the climate system is less resilient to GHG radiative forcing than was previously thought. Greater climate sensitivity to GHG radiative forcing makes the system less resistant to warming, while the ocean’s thermal inertia makes that warming essentially irreversible for the next thousand years.
Proposed Solution
If society is to avoid dangerous climate change, then the policy debate must transition from discussions of mitigation strategies focused almost exclusively on reducing GHG emissions to discussions of mixed strategies that include combinations of reducing GHG emissions and employing geoengineering approaches that extract CO2 from the atmosphere and/or reduce the level of incoming solar radiation reaching Earth’s surface.
Charles H. Greene is Director, Ocean Resources and Ecosystems Program, Department of Earth and Atmospheric Sciences, Cornell University.
D. James Baker is Director, Global Carbon Measurement Program, The William J. Clinton Foundation.
Daniel H. Miller is Managing Director, The Roda Group, Berkeley, CA, USA
Source: http://www.tos.org/oceanography/issues/issue_archive/issue_pdfs/23_1/23-1_greene.pdf
February 23, 2010