Global climate change: Lessons from the past – policy for the future
Abstract The Intergovernmental Panel on Climate Change (IPCC) recently published its second scientific assessment of climate change. Central to the findings of this study is the statement that “the balance of evidence suggests a discernible human influence on global climate”. This statement arose from recent studies which compared the observational record over the last century with the results from numerical modelling simulations of the climatic response to increasing greenhouse gases and anthropogenic sulphate aerosols. It has profound implications for policy makers as it is the first time that IPCC has stated that global warming has been detected in the observational record. Recent modelling studies reported in the IPCC second assessment also suggest “best estimates” of 2°C warming and 50 cm sea level rise by the year 2100, relative to 1990, with amplification of the warming at high latitudes and over the interior of continents. Similar IPCC “best estimates” of emission scenarios suggest that the atmospheric concentration of carbon dioxide will continue to increase over the next few centuries. Stabilization of atmospheric carbon dioxide levels, even as high as three times the present, require emission levels significantly below those of 1990. In this paper, the observational record is briefly reviewed as are the recent modelling results which have lead to the statements above. Particular emphasis is given to the role of the oceans in climate change and climate variability. By appealing to the paleoclimatic record for analogies of a climate warmed through anthropogenic greenhouse gases, a discussion of potential climatic swings and regime changes is presented. The policy implications of this work are also addressed.