Layout 1
The Cocktail
to Conversation Guide
Global
WarmingTM
Introduction
People discuss all sorts of topics at
cocktail parties and sometimes, perhaps
when the topics get a little boring, they
even discuss global warming and the
potential dangers it poses. President
Obama and the Congress believe it is a
serious threat that justifies severe limits
on carbon dioxide (CO2) and other
greenhouse gas (GHG) emissions.
To understand whether global warming
really is a serious threat, it is necessary
to understand some basic facts. Here are
the answers to commonly asked questions
about global warming.
Isn’t there a
of temperature data is suspect due to the location of
many temperature gauges that produce a “warm bias”
consensus of scientific
in the surface temperature record, which tends to
opinion on man-made
increase over time as natural vegetation is replaced
global warming?
by buildings and pavement.
No. Human activities, such as the burning of fossil fuels
Furthermore, surface temperature may not be the
to power our homes and businesses and changes to the
best measure of the Earth’s temperature. The oceans,
land, such as modern cities and expanded agriculture,
which represent 75% of the Earth’s surface and well
undoubtedly affect the environment, but just how
over 99% of the heat content of the climate system,
much they may be changing the climate is the subject
have only recently been monitored systematically. Those
of much debate.
measurements show little, if any, warming in recent
The so-called “consensus” typically refers to the
years. Satellite temperature records also show some
climate science assessments done every five years by
warming, but less than reported by the IPCC’s surface
the United Nations Intergovernmental Panel on Climate
temperature measurements.
Change (IPCC). A large number of scientists participate
in the detailed research reviewed by the IPCC, but the
Hasn’t the Earth’s
summaries interpreting the science are mostly guided
climate alternated
and written by government appointees. These summaries
in the past between
leave out the assumptions and uncertainties contained
ice ages and
in the longer assessment reports. The media report on
the summaries and their dramatic proclamations,
warming periods?
omitting the significant uncertainties and caveats.
Yes. Climate is always changing. During the last
10,000 years, the climate has remained relatively stable,
but temperature still has fluctuated significantly.
Is the world heating up?
A thousand years ago, when Vikings settled Greenland,
the climate was warmer than today and agriculture
How would we know?
flourished in the north of Scotland and Norway,
Not recently and not accurately. Even though GHG
where it is too cold for farming now. In spite of
emissions increased steadily in the latter half of the
considerable uncertainty as to how much climate
20th century, global surface temperatures have not
varies on decades-to-centuries time-scales or what
increased since about 1998. Since the late 1800s, the
causes changes, some scientists have simply assumed
world’s average surface temperature is believed to have
that human beings now control the climate system.
warmed about 1°F, which is, in part, a natural recovery
from the “Little Ice Age,” a period of global cooling
lasting from about 1400 to the 1800s AD. The precise
change is unknown because temperature in most parts
of the globe has not been measured accurately over a
very long period of time. Even in the U.S., the accuracy
Does man-made
How do we know
carbon dioxide (CO2)
what the climate will
contribute to global
be in the future?
warming?
We don’t. Predictions of future climate come from computer
models, which are very incomplete approximations of
Yes, but how much is uncertain. Water vapor and
the behavior of the real climate system. Models rely on
clouds account for over 90% of the natural greenhouse
assumptions about how the climate works and translate
effect. A doubling of atmospheric CO2, which could
those assumptions into mathematical representations of
be reached late in this century, would increase the
climate processes. But many of these processes, such as
greenhouse effect by only 3%. While all scientists agree
clouds and precipitation, ocean circulation and solar
the direct warming influence of this would be small,
effects, are not well understood and so cannot be
the fear is that the climate system will respond by
modeled accurately. The predictions of future climatic
decreasing cloud cover and increasing atmospheric
changes are hypotheses, not scientific facts.
water vapor, thereby greatly amplifying the warming.
IPCC scientists have argued that climate models will
This amplification is called positive feedback, and
not reproduce the temperature trends we have seen over
today it is exhibited by all 21 climate models the
the last century unless human effects are included, but
IPCC tracks.
that claim is weak. For instance, we do not have accurate
But global satellite measurements of temperature,
long-term measurements of clouds to determine
sunlight reflected from clouds, and infrared heat given
whether natural cloud changes might have caused past
off by the Earth all suggest the combined effects of water
episodes of warming and cooling. Also, in order to explain
vapor and clouds may actually reduce the small global
the last 100 years of global average temperatures, the
warming expected from CO2, not amplify it. This is
models have to be manipulated so that the cooling effect
called a negative feedback. Whether feedbacks in the
of man-made aerosols (dust, sulfates, etc. in the air) cancel
climate system are positive or negative is the most
out the warming effect of man-made carbon dioxide for
important question in global warming research today.
decades at a time — a peculiar strategy to say the least.
While humans are believed to be the main source
Simply put, climate models are research tools and ill-suited
of long-term CO2 increases, natural flows of CO2 in
for shaping public policy or the future of our economy.
and out of the Earth’s surface average about 20 times
the human contribution. Natural changes in ocean
circulation and biological activity on land and in the
Aren’t there serious
ocean are known to have just as large an impact on the
risks of increasing
year-to-year increase as human emissions do. But just
CO2 beyond certain
as some scientists assume there are no long-term
levels?
changes in cloud cover causing global warming, they
Maybe. The risks of increasing levels of CO
also assume there are no long-term natural increases
2 in the
atmosphere are not well understood, but we do know
in CO2.
that the Earth has experienced previous CO2 levels
well beyond those projected. We seldom hear about the
benefits of more CO2 in the atmosphere, even though
Are sea levels rising?
it is an element that is necessary for life to exist.
Are Greenland,
And if feedbacks in the climate system are negative,
the Arctic, and the
as satellite data suggest, then any human source of climate
Antarctic melting?
change becomes small compared to natural climate
variability. Alarmists and the media often cite climate
Yes and yes, but neither can be linked to global warming
catastrophes that are the result of model-generated
with any certainty. Sea levels have risen some, and
temperature increases on the order of 6°–10°F. A
melting is observed, but the causes are the subject of
temperature rise this great can only be caused by
much study. The oceans have not risen rapidly during
positive feedbacks in response to greenhouse gas
the past century. In the 20th century, the sea level rose
emissions. Changes of this magnitude are improbable
an average of 1.7 mm per year, but the level is still low
and merely reflect the unstable nature of trying to
compared to the last interglacial period, when it was
model a system as complex as the Earth’s climate.
about 6 meters higher than today. Between 1920 and
Uncertainty is reason to take prudent actions to
1940, the Arctic experienced a period of warming
manage risk, such as developing new energy technologies
equal to recent temperatures. That period of warming
and increasing efficiency. Presently, almost one-third
did not lead to significant sea level rise from melting
of the world’s population does not have access to fossil
of the Greenland ice sheet. The warmest year in
fuel energy. As these people begin to prosper, they will
Greenland was 1941, and the warmest decades were the
use more energy and emit more greenhouse gases.
1930s and 1940s. The Greenland Ice Sheet is melting
Achieving a higher standard of living by using energy
at the edges, but growing inland because of increased
efficiently and by developing new energy technologies
precipitation. After a twenty-year period of decline,
is essential to constraining greenhouse gas growth. But
sea ice in the Arctic Ocean is showing signs of recovery.
the world will not be able to reduce levels of greenhouse
Around Antarctica, sea ice increased over the same
gases to a level that existed more than a century ago,
period of time, contrary to expectations. The net result
despite the rhetoric of advocacy groups and politicians.
is that global sea ice area has remained nearly constant.
Population growth, economic growth, and the limits of
There is a small region around the Antarctic Peninsula
available technology all work against it.
where the highly publicized collapse of ice shelves is
attributed to global warming, but natural changes in
ocean circulation patterns in the area could be an
Can any specific event,
explanation. Like glaciers, ice shelves must ultimately
such as a drought or
break off and float away naturally. The dynamics of
a tornado, be tied to
glaciers and ice sheets are too poorly understood to
global warming?
make reasonable projections.
No. Specific weather events cannot be linked to global
Estimates of significant sea level rise assume that
warming. The effect of warming on hurricanes, tornados,
the Greenland and Antarctic ice sheets will melt at
and torrential rains is the subject of much speculation,
increasing rates, resulting from substantial warming,
but there is little evidence that a warming world has
which is possible only if our climate system is dominated
made — or will make — these events more frequent
by strongly positive feedbacks.
or more severe.
The Big Picture
While the subject of climate change is complex, there
is a common theme that runs throughout the theory
of man-made global warming: Nature was in balance
before human industrial activity began. But science does
not support this naïve and romantic view of nature.
The natural climate system is much more complex and
dynamic than is represented in model projections.
For More Information:
Although we don’t know exactly why, climate has both
Climate Issues and Questions – 3rd Edition
changed significantly over time and varies substantially
www.marshall.org/article.php?id=577
globally and regionally. Whatever the threat of climate
Climate of Extremes:
change to humanity, it is most likely to be natural — not
Global Warming Science
They Don’t Want You to Know
man-made. Observation, learning, innovation, and
by Patrick J. Michaels, Cato Institute
technology represent a human feedback cycle that has
Climate Confusion:
led to increased environmental protection and to actions
How Global Warming Hysteria
Leads to Bad Science, Pandering Politicians
that reduce the energy use and emissions related to
and Misguided Policies that Hurt the Poor
human economic activities.
by Roy Spencer,
University of Alabama – Huntsville
Natural sources of climatic change are poorly
Intergovernmental Panel
on Climate Change
understood and inadequately measured. Until science
www.ipcc.ch
better understands natural climate change, large
uncertainties will remain regarding what part of past,
current, and future climate change is due to human
activities. Until science offers clearer answers to those
questions, we are best served by actions to mitigate
emissions without sacrificing energy use and by learning
how to adapt to changing environmental conditions.
The Cocktail
to Conversation Guide
Global
WarmingTM
George C. Marshall Institute
Email: info@marshall.org
www.marshall.org
