The Long Time Scales of Human-Caused Climate Warming:

0,16

MB

Further Challenges for the Global Policy Process

28

stron

2381

ID

Pew Center on Global Climate Change

2002

rok

Executive Summary

In 2001, the Intergovernmental Panel on Climate Change's (IPCC) Third Assessment

Report revealed important increases in the level of consensus concerning the reality of

human-caused climate warming. The scientific basis for global warming has thus been

sufficiently established to enable meaningful planning of appropriate policy responses to

address global warming. As a result, the world's policymakers, governments, industries,

energy producers/planners, and individuals from many other walks of life have

increased their attention toward finding acceptable solutions to the challenge of global

warming. This laudable increase in worldwide attention to this global-scale challenge

has not, however, led to a heightened optimism that the required substantial carbon

dioxide (CO2) emissions reductions deemed necessary to stabilize the global climate

can be achieved anytime soon. This fact is due in large part to several fundamental

aspects of the climate system that interact to ensure that climate change is a phenomenon

that will emerge over extensive time scales.

Although most of the warming observed during the 20th century is attributed to

increased greenhouse gas concentrations, because of the high heat capacity of the

world’s oceans, further warming will lag added greenhouse gas concentrations by

decades to centuries. Thus, today’s enhanced atmospheric CO2 concentrations have

already “wired in” a certain amount of future warming in the climate system, independent

of human actions. Furthermore, as atmospheric CO2 concentrations increase, the

world’s natural CO2 “sinks” will begin to saturate, diminishing their ability to remove CO2

from the atmosphere. Future warming will also eventually cause melting of the

Greenland and Antarctic ice sheets, which will contribute substantially to sea-level rise,

but only over hundreds to thousands of years. As a result, current generations have, in

effect, decided to make future generations pay most of the direct and indirect costs of

this major global problem. The longer the delay in reducing CO2 and other greenhouse

gas emissions, the greater the burden of climate change will be for future life on earth.

Collectively, these phenomena comprise a “Global Warming Dilemma.” On the one

hand, the current level of global warming to date appears to be comparatively benign,

about 0.6°C. This seemingly small warming to date has thus hardly been sufficient to

spur the world to pursue aggressive CO2 emissions reductions. On the other hand, the

decision to delay global emissions reductions in the absence of a current crisis is

essentially a commitment to accept large levels of climate warming and sea-level rise

for many centuries. This dilemma is a difficult obstacle for policymakers to overcome,

although better education of policymakers regarding the long-term consequences of climate

change may assist in policy development.

The policy challenge is further exacerbated by factors that lie outside the realm of science.

There are a host of values conflicts that conspire to prevent meaningful preventative

actions on the global scale. These values conflicts are deeply rooted in our very

globally diverse lifestyles and our national, cultural, religious, political, economic, environmental,

and personal belief systems. This vast diversity of values and priorities

inevitably leads to equally diverse opinions on who or what should pay for preventing or

experiencing climate change, how much they should pay, when, and in what form.

Ultimately, the challenge to all is to determine the extent to which we will be able to contribute

to limiting the magnitude of this problem so as to preserve the quality of life for

many future generations of life on earth.