Essay by sammika November 2014

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By Michael E. Mann

I. Introduction

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


© 2009 Social Philosophy & Policy Foundation. Printed in the USA.


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 behavior of

the Earth


s climate system are discussed below, and include the notion of

energy balance,

which governs how the climate system works, the


house effect

(including the special case of the





house effect), which is necessary to understanding surface temperatures

on Earth, and so-called


which can amplify the magnitude of

climate changes. Other essential aspects of the science of climate change

are the construction and use of theoretical

climate models

to investigate the

behavior of the climate system, an understanding of the factors that have

governed past climate, and, finally, the inferences that can be drawn

through a comparison of model simulation predictions and available obser-

vations in the assessment of the human impact on climate.