DO GLOBAL WARMING AND CLIMATE CHANGE REPRESENT A SERIOUS THREAT TO OUR WELFARE
By Michael E. Mann
The subjects of "global warming" and "climate change" have become parts of both the popular lexicon and the public discourse. Discussions of global warming often evoke passionate responses and fierce debate between adherents to different views of the threat posed. Yet there are many nuances regarding global warming, climate change, and the threats they represent that are not well understood by the public. The public's conceptual under- standing hinges largely on images and paradigms within the popular culture that are often little more than caricatures of the actual, underlying scientific concepts. To appreciate the potential threat that climate change and global warming represent to human society, living things, and our environment, it is necessary that we first understand the true science underlying these phenomena.
The purpose of this essay is to assess the implications of climate change for the welfare of human society and our environment. I will first discuss the science underlying global warming, climate change, and the connec- tions between these two phenomena (Section II). I will then explore what climate changes are projected for the future under various plausible sce- narios of future human behavior (Section III), and what impacts these changes are likely to have on society, ecosystems, and our environment (Section IV). Finally, I will consider the economic, security, and ethical considerations relevant to evaluating the threat of climate change (Sec- tion V) and the steps that should arguably be taken to mitigate climate change and its impacts (Section VI). I will summarize my conclusions Section VII.
II. Scientific Background
Global warming refers to the phenomenon of increasing average surface temperatures of the Earth over the past one to two centuries. The concept is related to the more general phenomenon of climate change, which refers to changes in the totality of attributes that define climate -not only sur- face temperatures, but also precipitation patterns, winds, ocean currents, and other measures of the Earth's climate. For this reason, I will favor the doi:10.1017/S0265052509090220 © 2009 Social Philosophy & Policy Foundation. Printed in the USA. 193
use of the more general term 'climate change' throughout this essay, recognizing that global warming is simply one of the attributes of climate change. Climate change can be viewed as consisting of two components, one of which is human (i.e., anthropogenic) in origin and coincides in timing with the industrial period of the past two centuries, and the other of which is natural and has played a role in both past and current climate variability. Global warming generally refers to the anthropogenic com- ponent of climate change alone, and only the surface warming associated with it. The key scientific issues required to understand the...