Is the New UN Global Warming Report Too Conservative?
by Brett Clark and John Bellamy Foster
There is now a strong consensus among climate scientists that human
activities are the primary forces responsible for the observed warming
of the earth's atmosphere. The recently released fourth
assessment report, Climate Change 2007: The Physical Science Basis, of
the United Nations Intergovernmental Panel on Climate Change (IPCC)
notes that warming is "unequivocal" and human activities are
the cause. Global average temperature has risen by 0.74°C
(1.3°F) since 1906. The IPCC projects a further increase of
0.4°C (0.7°F) in warming during the next two decades, and an
increase (best estimate) of 1.8-4.0°C (3.3-7.1°F) in global
average temperature during this century.
Not surprisingly, this new report, which was the product of hundreds
of scientists (150 lead authors with 450 contributing authors) and had
to be unanimously approved by 154 governments, including the United
States and other major oil-producing countries, is shrouded in
controversy. However, rather than arising from global warming
naysayers, the principal challenge to the report this time comes from
leading climatologists themselves, who view this new IPCC report as
too conservative, underestimating the risks of global climate
Commenting on the IPCC's record with climate change projections, James
Hansen, Director of the NASA Goddard Institute for Space Studies and
widely considered to be the world's foremost climatologist, explained
that the "IPCC has not overstated or overestimated those
changes. The changes of carbon dioxide have been very accurate.
Temperatures actually increased somewhat faster than projections.
And sea level has increased notably faster than the prior estimates by
IPCC" ("Gorilla of Sea Level Rise," Living on Earth,
February 2, 2007). Yet, if the IPCC has in no way erred by
overestimating the dangers, the same cannot be said with respect to
underestimating them. Hansen and other leading climatologists
insist that the new IPCC report fails to provide projections of sea
level rise that are consistent with rising global temperature.
As the ocean warms due to increasing global temperature, it also
expands, causing the sea level to rise. Melting glaciers and ice
sheets are also increasing the volume of water. Destabilization
of the ice sheets in Greenland and Antarctica would result in big
increases -- to be measured in feet rather than inches -- in sea
level. Nonetheless, the new IPCC report estimates an increase in
sea level of only 18 to 59 centimeters (0.6-1.9 feet) this century --
an estimate even lower than in its 2001 report. Some experts
have voiced strong dissent regarding these calculations (see
"Experts Slam Upcoming Global Warming Report," CNN.com).
Hansen points out that the IPCC center point of 3°C (5.4°F)
increase in global average temperature is "inconsistent with the
numbers that they gave for sea level," because they do not take
into account the contribution of melting ice sheets ("Gorilla of
Sea Level Rise").
In an article in Science (January 19, 2007), Stefan Rahmstorf
"connects global sea-level rise to global mean surface
temperature." In establishing this relationship, Rahmstorf
projects a "sea-level rise in 2100 of 0.5 to 1.4 meters [1.6-4.6
feet] above the 1990 level." Hansen and his colleagues at
the Goddard Institute observed in an article entitled "Global
Temperature Change" published in the Proceedings of the National
Academy of Sciences on September 26, 2006, that the temperature of the
earth is now at the Holocene maximum and within approximately 1°C
(1.8°F) of the maximum temperature of the last million years when
the sea level was maybe as much as 5 meters (16 feet) higher than
today. At a time when the earth's temperature was 2-3°C
(3.6-5.4°F) warmer than today in the Middle Pliocene three million
years ago, the sea level was 25-35 meters (80 feet or more) higher.
As Hansen notes, based on this and other research:
We do have a lot of information available to us both from
paleoclimate; the history of the earth and how ice sheets responded in
the past and also the new data from satellites, and on surface
measurements on the ice sheets which shows that there are processes
beginning to happen there, exactly the processes that we're afraid
will accelerate. The last time a large ice sheet melted sea
level went up at a rate of five meters per century. That's one
meter every 20 years. And that is a kind of sea level rise, a
rate which the simple ice sheet models available now just cannot
produce because they don't have the physics in them to give you the
rapid collapse that happens in a very nonlinear system ("Gorilla
of Sea Level Rise").
Larsen BIn "A Worrying Trend of Less Ice, Higher Seas,"
published in the March 24, 2006, issue of Science, Richard A. Kerr,
explained that the melting of the ice sheets and glaciers in Greenland
and Antarctica has accelerated in the last ten years. Ice
shelves are moving rapidly toward the sea and melting. For
example, when the 1,255-square-mile Larsen B ice shelf broke off of
Antarctica in 2002, it only took 35 days for it to disappear.
As the temperature increases, a chain reaction is set in motion,
amplifying warming tendencies. The ice caps melt and pools of
water are formed. Rather than reflecting solar radiation, like
the white ice does, the blue water absorbs the heat, further
accelerating the rate of melting of the adjacent ice cap. This
water also heats the ice below, driving deep holes of warm water
within an ice shelf. The water from melting ice over land, such
as in Antarctica and Greenland, sinks deep into the ice, cutting
tunnels, known as "moulins." When it reaches the land
beneath the ice, it both warms the ice underneath and serves as a
lubricant that could lead massive amounts of ice to shift and fall
into the sea. The melting of just Greenland could raise the
worldwide sea level 20 feet. These positive feedback loops can
start out slow, but accelerate in time.
In contemplating such changes and increases in the global temperature,
James Hansen points out "if you start talking two or three
degrees Celsius, then you're really talking about a different planet
from the one we know" ("Gagged Climate Expert," Living
on Earth, February 3, 2006).
In part, the critique offered by Hansen and other leading
climatologists of the new IPCC report stems from the urgency of the
matter at hand. "We have," Hansen says, "at most
ten years -- not ten years to decide upon action, but ten years to
alter fundamentally the trajectory of global greenhouse emissions"
-- if we are to prevent such disastrous outcomes from becoming
inevitable ("The Threat to the Planet," New York Review of
Books, July 13, 2006). One crucial decade, in other words,
separates us from irreversible, nonlinear processes that could set in
motion the conditions for an entirely new geological age leading to
the extinction of a majority of species on the earth and threatening
The severity of the situation is amplified if we consider the full
range of ecological consequences (droughts, flooding, severe storms,
loss of biodiversity, etc.) of global climate change, not to mention
the array of environmental problems that are emerging as every
ecosystem is threatened with collapse. The scale of ecological
destruction -- as well as the ongoing nuclear threat -- caused the
Bulletin of Atomic Scientists recently to move its symbolic
"doomsday clock" to five minutes to midnight, two minutes
forward from where it was -- and twelve minutes closer to cataclysm
than in the early 1990s.
In reality, the threat to the planet from the environmental crisis is
even more serious than natural-scientific reports suggest (see
"Ecology of Destruction," Monthly Review, February 2007).
This is because there is much more than mere political inertia, as
commonly supposed, preventing the world from radically changing course
and initiating an alternative scenario to business as usual.
Capitalism is by its very nature an unceasing treadmill of
production. As Karl Marx put it in the nineteenth century:
"The division of labor is necessarily followed by greater
division of labor, the application of machinery by still greater
application of machinery, works on a large scale by work on a still
larger scale. That is the law [driven by competition] which
again and again throws bourgeois production out of its old course and
which compels capital to intensify the productive forces of labor,
because it has intensified them . . . the law which gives capital no
rest and continually whispers in its ear 'Go on! Go on!'"
(Wage Labor and Capital). There is no conceivable alternative
scenario within such a runaway-train system that leads toward a
sustainable relation to the environment, much less a just society.
What is needed is a worldwide revolution in our relation to nature,
and thus of global society itself.
Brett Clark is a frequent contributor to Monthly Review. He
has also published articles in Organization & Environment, Theory
and Society, and the Sociological Quarterly. John Bellamy Foster
is professor of sociology at the University of Oregon, author of
Marx's Ecology, Ecology against Capitalism, The Vulnerable Planet, and
Naked Imperialism, and editor of Monthly Review.