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The Science of Global Climate Change
Michael MacCracken
Climate Institute
Washington DC
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This is a summary of the key points of a talk by the author at the National
Catholic Rural Life Conference in Washington DC, 19 February 2005. The
views expressed are those of the author, drawing on the findings of major
national and international scientific assessment reports that have
undergone extensive expert review. |
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Introduction
The Earth is changing. An astronomer on some remote planet would be amazed
at what is happening, and how rapidly. First came mankind’s changing of the
Earth’s vegetation cover, altering the Earth’s reflectivity and local weather. Next
came depletion of the stratospheric ozone layer and the "Antarctic Ozone Hole."
And over recent decades has come accelerating modification of the composition
of the atmosphere and climate change, often referred to as "global warming."
Quite clearly, the natural course of Earth’s evolution is being affected.
Although the details can get complicated, the science of climate change is quite
straightforward, and can be summarized in six key points that rest on
fundamental physics that have slowly been solidified since the possibility of such
an effect was first raised over one hundred years ago.
1. Human Activities Are Changing Atmospheric Composition
A wide variety of observational and analytical evidence provides convincing
evidence that human activities are changing the composition of the atmosphere.
Observations at locations around the world indicate that the atmospheric
composition of carbon dioxide (CO2) has increased by about 20% since careful
measurements began in 1957. Concentrations in air bubbles in glacial ice
document about a 36% increase in the CO2 concentration over the past few
centuries. There are even some suggestions that the forest clearing resulting
from the settling down of nomadic tribes about 8000 years ago caused an
increase in the CO2 concentration above what would have been its natural level.
Figure 1 (courtesy of the US National Assessment) shows a reconstruction of the
CO2 concentration for the past 1000 years, indicating the very unusual nature of
the recent increase.
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Figure 1: Record of the CO2 concentration (in parts per million by
volume) over the past 1000 years, reconstructed from ice cores up to
1957 and then from observations. Figure courtesy of the US National
Assessment.
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Two types of human activities are mainly responsible for the sharp increase. The
first is carbon resulting from changes in use of the land, including the clearing of
forests, the plowing of the land, and the growing of crops. As shown in Figure 2,
these changes are currently responsible for the ongoing release of 1-2 billion
tonnes of carbon (GtC) each year, mainly in the form of carbon dioxide . The
second, and most important, source of CO2 emission is the combustion of coal,
oil, and natural gas. These fuels are together referred to as fossil fuels because
they are derived from the fossilized remains of plants and animals. Basically, we
are injecting back into the atmosphere carbon that was stored away by natural
processes over periods of tens to hundreds of millions of years—all in the time
span of a couple of centuries. There is no doubt that it is these human activities
that are changing atmospheric composition.
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Figure 2: Reconstruction of past emissions of CO2, in gigatonnes of
carbon (GtC, billions of metric tons). Figure from US National Assessment.
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The land use contribution is shown in maroon in Figure 2, being the increment
above the fossil fuel emissions. Many official compilations of emissions present
the amounts as the mass of carbon dioxide rather than of carbon. This has the
effect of counting as emissions the mass of the oxygen molecules that are
already in the atmosphere, so is a bit misleading. However, it does make the
numbers bigger. To make the conversion, multiply the amount of carbon released
by the relative molecular weights, so 44/12, or about 3.7, to get the mass of
carbon dioxide released.
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Compilations of all the fossil fuels combusted each year indicate that the
international use of these fuels is leading to the injection of 6-7 billion tonnes of
carbon into the atmosphere—roughly one tonne each year for every man,
woman, and child on the planet. So, how much is this? A ton of carbon as
gasoline provides a range of roughly 10,000 miles . The 8 billion tonnes of
carbon emitted each year due to fossil fuel combustion and land use change are
about equivalent to the net amount of carbon that the Northern Hemisphere’s
growing vegetation pulls out of the atmosphere each year from spring through
summer—that is, the net amount of carbon taken up by new leaves, grasses, and
trees each year. Even though about a quarter of these emissions are taken up by
the ocean and another quarter by the growth of new vegetation, as long as
substantial emissions occur, about half will remain in the atmosphere for periods
of centuries.
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[NOTE: A gallon of gasoline (e.g., octane) weighs about 6 pounds and is about 80%
carbon. Thus a ton of carbon is equivalent to roughly 400 gallons of gas, which at 25
miles per gallon would give a range of 10,000 miles.]
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2. Changing Atmospheric Composition Can Warm the Earth
The second key finding from scientific research, and this has been recognized for
over 100 years, is that this type of change in the atmospheric composition will
warm the planet by enhancing the Earth’s natural greenhouse effect. Common
wisdom is that it is the Sun that keeps us warm, and it is true that it is the Sun
that is the fundamental source of energy for our planet. However, it is really the
atmosphere that keeps us warm—without the atmosphere it is estimated that the
Earth would be some 33°C (or 60°F) colder than it is.
Averaged over the surface of the Earth, twice as much energy is coming down to
the surface in the form of heat energy (technically, infrared radiation—the kind
that a hot stove gives off) as is coming down from the light of the Sun. As
illustrated in Figure 3, what is happening is that the Sun warms the surface a bit;
then, as a result, the surface, like any warm body, emits infrared radiation. As
this radiation tries to escape from the planet, water vapor, CO2, and other gases
in the atmosphere absorb about 90% of it. These gases give up some of this
energy to the surrounding oxygen and nitrogen molecules, warming the air, but
they also radiate some of this energy away—both upwards and downwards. The
upward radiation may escape to space or be absorbed by gases higher up in the
atmosphere. The downward radiation warms the surface, causing more upward
radiation. This process goes on multiple times and gets pretty complicated
because certain molecules absorb and emit energy only in certain wavelengths,
but the net result is that roughly 80% of the energy radiated upward by the
surface is radiated back to it by the atmosphere, creating the natural greenhouse
effect that keeps the world from freezing. Actually, of course, a lot more is going
on, with much of the energy that is radiated back to the surface being used to
enhance the natural cycle of evaporation and precipitation.
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Figure 3: Schematic diagram of the Earth’s energy balance. The width of
the arrows is proportional to the amount of energy. Figure from US
National Assessment.
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That this natural greenhouse effect exists is evident in our everyday lives—or
rather our every-night lives; if you go out on a cloudy or humid night, you will feel
much warmer than if you go out on a clear or very dry night—when water vapor
(or droplets) are present, including as clouds, the effect of the natural
greenhouse can readily be experienced.
When we add gases such as CO2 and other similarly acting gases and particles
to the atmosphere, a higher fraction of the energy emitted from the surface is
returned to the surface, intensifying the natural greenhouse effect.
Analyzing how the climate has changed in the past, how planetary climates work,
and carrying out laboratory and modeling studies, all our scientific understanding
indicates that a doubling of the CO2 concentration will, over several decades,
cause a global warming of about 3°C (about 5°F), plus or minus roughly 50%.
This estimate of the climate sensitivity has been quite widely agreed to for about
25 years, and is only a little less than the value first estimated over 100 years
ago by the Swedish scientist Svante Arrhenius.
All this concern over a few degree global warming, Although we all experience
large changes in temperature from day to day, season to season, and place to
place, a few degree global warming has the potential to be very significant. For
reference, the global average warming from the peak of the last ice age some
20,000 years ago to the present was only about 5°C (8°F), so doubling the CO2
concentration is equivalent to about half of that warming. We already have had
more than a 35% increase in the CO2 concentration and projections indicate that
a doubling is very likely to occur by the end of the 21st century unless stringent
control measures are invoked over coming decades.
3. Human-induced Climate Change is Evident in the Climate Record
In that this CO2 increase has been going on for 150 years or so, we should be
expecting to see the climate changing in response. Indeed, there are an
increasing variety of observations indicating that the climate is changing. For
example, Figure 4 shows that the annual mean global average temperature
increased by about 0.6ºC (about 1ºF) over the 20th century, with both land and
ocean temperatures rising markedly over the past few decades.
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Figure 4: Globally averaged departures of annual average surface air
temperature from their long-term mean. Figure courtesy of NOAA National
Climatic Data Center.
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Observations also indicate that upper ocean waters are warming and that many
glaciers around the world are melting. Both of these processes tend to cause sea
level to rise, and indeed, this is being observed. There are also many other
indicators that the climate is changing; perhaps most troubling is that shifts in the
ranges of various plants and animals are being observed, and the large majority
of these changes are consistent with what would be expected as a result of
changes in the climate, even more so than other human-induced changes in the
landscape.
Determining if these changes are due to human activities is complicated by the
fact that other factors are also causing the climate to fluctuate. These other
factors include fluctuations in solar radiation, injection of aerosols into the
stratosphere by major volcanic eruptions, injection of sulfate and soot aerosols
into the atmosphere from combustion of coal, and just the chaotic interaction of
the atmosphere with the oceans, as occurs, for example, with an El Niño.
Although the limited records do indicate that volcanic eruptions and changes in
solar radiation are likely to have played a role in past fluctuations in the climate,
these factors have not changed in a way consistent with recent warming over the
past several decades, so the recent warming does not appear to be due to these
natural factors. On the other hand, warming appears to be evident before the
greenhouse gases started rising rapidly, so it may well be natural influences that
caused the warming in the early 20th century.
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[NOTE: While the prevailing view is that the early 20th Century warming was mainly
natural in origin, this is mainly a circumstantial conclusion. Interestingly, some
indications are starting to emerge that at least some of that warming may have been
induced by the combined influence of the increases in greenhouse gases and in
aerosols.] |
As indicated in Figure 5, the best explanation of recent changes in temperature
(and also of the observed changes in other variables) is that they are due to the
combined effects of increasing the concentration of CO2 and other greenhouse
gases and increasing the atmospheric loading of the particulate matter that also
results from combustion of fossil fuels. Not all indicators are in full accord,
however, and, because the case is largely circumstantial, there are, and need to
be, ongoing efforts to try to prove otherwise. However, the preponderance of
observations and analyses indicate we are undergoing changes in the climate
due to human activities.
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Figure 5: Comparison of model simulations of the globally averaged
change in annual mean surface air temperature with observations of the
same quantity assuming (a) only natural forcing by changes in solar and
volcanic effects; (b) only human-generated forcing by greenhouse gases
and aerosols; and (c) the combined effects of both natural and human-
generated forcing. Figure from IPCC Third Assessment Report.
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4. Climate Change Will Accelerate During the 21st Century
So, what lies ahead? At present, each year’s fossil fuel use by the 6-plus billion
people on the planet is leading to the emission of 6-plus billion tonnes of carbon
to the atmosphere; this is an average of one tonne of carbon per person per
year. The distribution of the emissions is, however, quite varied, as shown in
Figure 6. In the underdeveloped countries, the emissions are of order half a
tonne per person; in China, the level is approaching 1 tonne per person; in
Europe it is about 3 tonnes per person; and in the US and a few other countries,
it is over 5 tonnes per person. When the climate change statement by the US
Catholic Bishops spoke about issues of equity, they were referring, in part, to this
unequal use of fossil fuels and, therefore, about the unequal contribution of
different peoples to the problem.
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Figure 6: The height of the bar indicates the per capita rate of use; the
width of the bar is proportional to population. Therefore, the area of the
bar indicates total usage by region. The bars are shaded to indicate usage
of coal, oil, and natural gas, and emissions due to changes in the
biosphere (e.g., deforestation).
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Figure 7: A mid range population projection for the 21st century. Figure courtesy
of the Office of Science and Technology Policy.
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For the future, the world population looks likely to increase to at least 8 billion
and possibly reach over 10 billion by the end of the century. As shown in Figure
7, most of the future growth in population is expected to occur in the developing
world. While the birth rates are dropping in many of these countries, their
populations are projected to grow significantly as average life span is extended
and the age distribution comes into equilibrium.
In the absence of restraints on fossil fuel use that might arise because of concern
about climate change, emissions of CO2 can be expected to rise dramatically. In
particular, China and India appear likely to make extensive use of their low-cost
coal reserves to provide the energy needed to enhance overall living standards,
although problems of air pollution and acid rain may lead to some limits. In
addition, with the coming depletion of oil later this century, the need for liquid
fuels may need to be met by deriving such fuels from coal. Because this
conversion process requires additional energy, such an energy path would
lead to emission of much more carbon per useful unit of fossil energy.
The Intergovernmental Panel on Climate Change (IPCC), representing the
collective efforts of about 180 countries, has developed scenarios of plausible
societal and emission paths. Considering current trends and future possibilities,
emissions could increase significantly by the end of the century. The IPCC’s
most ambitious scenario envisions virtually all additional energy coming from
alternative energy sources; in its most pessimistic, in a climate sense, most of
the additional energy would come from coal. The emissions scenario shown in
Figure 8, in which the rate of emissions triples, is roughly a mid-range case. Note
that most of the emissions increase is projected to occur from countries currently
considered to be developing, a point raised by policymakers in the developed
countries who seem to forget that because there are several times more people
in developing countries, their per capita levels, which are perhaps a measure of
relative equity, are still well below the per capita level in developed countries.
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Figure 8: Mid-range projection of CO2 emissions, based on a scenario
from the IPCC Second Assessment Report. |
Accepting the IPCC emissions scenarios as representing a plausible range of
what could happen, the CO2 concentration would, by 2100, be expected to rise
from its current level of about 35% above the preindustrial level to between 100%
to 300% above its preindustrial level; that is, the CO2 concentration would be
roughly 2 to 4 times its preindustrial concentration. The Earth has not
experienced such high a CO2 concentration in tens of millions of years, and
unless the emissions were to be cut to about 75% below current levels, which
will be very difficult given the higher population and the rising overall standard of
living, the CO2 concentration in the atmosphere will still be rising into the 22nd
century.
So, what will this mean for the climate? Unfortunately, we can’t construct physical
models of the Earth in the laboratory to test things out, and there is no simple
algebraic way to represent the Earth’s climate. While paleoclimatic analogs
provide some hint of what could happen, our data are pretty limited and the
change in atmospheric composition is occurring much, much more rapidly than
has ever been the case in the past. As a result, we are forced to rely on
theoretical models of the Earth system that are constructed in supercomputers
using the fundamental equations and principles of physics, chemistry, and
ecology to simulate the world’s atmosphere, oceans, and land. As illustrated
schematically in Figure 9, these computerized global climate models attempt to
represent the effects of all of the important processes governing the climate
system. The level of confidence that can be placed in the models is then
determined by testing, revising, and retesting the models to improve their ability
to simulate how the climate of the Earth has worked in the past and is working
today.
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Figure 9: Schematic diagram of processes represented in global climate
models. Figure from US National Assessment
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In general, the models reasonably represent the large-scale, time-averaged
behavior of the Earth system, generally reproducing the seasons, the monsoons,
and the geographic distribution of the climate. When examined closely, however,
the model simulations do much less well in representing the details, particularly
in regions of sharp terrain. In addition, the models do not yet simulate the natural
chaotic behavior of the system as well as is needed to project changes in the
frequency and intensity of extreme events. As Stanford scientist Steve Schneider
has commented, the models represent a usable, but somewhat hazy, crystal ball.
Ideally, one would wait until all the various weaknesses in models had been
resolved before applying them, but the Earth system is arguably the most
complex system science is investigating and a perfect model is an illusory goal.
Thus, the decision comes down to whether or not to use the models to try to
carefully derive at least some insights about how the future is likely to evolve.
There can be legitimate discussion about the remaining uncertainties and
limitations, but totally rejecting model results, as some of the noisier critics argue,
would be failing to use of the unique human capability for contemplating what
coming decades may bring.
Presuming that future emissions of carbon are within the bounds of IPCC’s
scenarios, the models project an increase in the global average temperature of
about 2 to 5ºC (about 3 to 10ºF) during the 21st century as compared to an
increase of about 0.6ºC (about 1ºF) over the 20th century—so several times as
much. The range is about equally a result of uncertainties in how emissions will
change and uncertainties in how the climate will respond. Figure 10 shows the
IPCC’s projections of future change for a range of emissions scenarios (each
indicated by a different color line), with B1 having the least emissions and A1F1
having the highest emissions.
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Figure 10: Model projections of the increase in global average surface air
temperature from 1990 to 2100 for various emissions scenarios. Figure
from IPCC Third Assessment Report. |
All of the various models developed by groups around the world, each making
their own attempt to best match the behavior of the real world, project that the
warming will be greater over land areas than over the oceans and greater in mid
to high latitudes than in lower latitudes. The US meets both criteria. Over the US,
the warming would be more or less like changing the climate of the northern tier
of states to the climate of the central tier, and of the central tier to the southern
tier. And if you live in the southern tier now, well, plan to spend summers inside,
as the heat index will increase substantially. So, New England’s climate would
become like that of the Washington DC area; the Washington DC area like
Atlanta, and so forth.
Associated with the warming, there will be other changes. Periods subject to frost
will shorten, and summers will have more unusually hot days. Temperatures will
not cool down so much at night. Rainstorms are likely to come with more
intensity, with periods of heavy rain increasing in intensity the most. With
evaporation occurring more rapidly, drying will occur faster, and so moisture
stress will occur more rapidly. Basically, wet periods will be wetter, and drought
periods drier. Mountain glaciers and likely the Greenland and West Antarctic ice
sheets will be melting back more rapidly, adding water to the oceans; ocean
warming, which will cause ocean waters to expand, will also contribute to sea
level rise. Much less certainly, there is the possibility that some sort of abrupt
change might occur, a change that might lock in some unusual atmospheric or
oceanic circulation for a period of time. As Dr. Wallace Broecker, a chemical
oceanographer at the Lamont-Doherty Earth Observatory, has commented, we
are poking a capricious beast (e.g., a sleeping bear) with a very sharp stick—the
effect may be gradual, or it may not. Continuing on the present path, the world
faces unprecedented climatic change and quite possibly some surprises along
the way.
5. Climate Change Will Affect the Environment, Natural Resources,
Communities and People
So, why should we care that the climate is changing? To provide an initial
evaluation, hundreds of scientists from around the country, working with local
experts, governmental representatives, and the public, participated in the US
National Assessment of the potential consequences of climate variability and
change, which took place from 1997 to 2001. Through a series of workshops and
assessments, the most important issues were identified for the various regions of
the country and for key sectors of the economy. A comprehensive set of reports
emerged that is available over the Web at www.usgcrp.gov/usgcrp/nacc/default.htm.
A federal advisory committee, also composed of experts, then summarized and
integrated the findings. Their report was released in late-2000 and summarized
their key findings for the US as follows:
1. Assuming continued growth in world greenhouse gas emissions, temperatures
in the US are projected to rise 5-9ºF (3-5ºC) on average in the next 100 years,
although a wider range of outcomes is possible.
2. Climate change and the potential impacts of climate change will vary widely
across the nation. [See TABLE]
3. Many ecosystems are highly vulnerable to the projected rate and magnitude of
climate change. A few, such as alpine meadows in the Rocky Mountains and
some barrier islands, are likely to disappear entirely in some areas. Others, such
as forests of the Southeast, are likely to experience major species shifts or break
up into a mosaic of grasslands, woodlands, and forests. The goods and services
lost through the disappearance or fragmentation of certain ecosystems are likely
to be costly or impossible to replace.
4. Water is an issue in every region, but the nature of the vulnerabilities varies.
Drought is an important concern in every region. Floods and water quality are
concerns in many regions. Snowpack changes are especially important in the
West, Pacific Northwest, and Alaska.
5. At the national level, the agriculture sector is likely to be able to adapt to
climate change. Overall, US crop productivity is very likely to increase over the
next few decades, but the gains will not be uniform across the nation. Falling
prices and competitive pressures are very likely to stress some farmers, while
benefiting consumers.
6. Forest productivity is likely to increase over the next several decades in some
areas as trees respond to higher carbon dioxide levels. Over the longer term,
changes in larger-scale processes such as fire, insects, droughts, and disease
will possibly decrease forest productivity. In addition, climate change is likely to
cause long-term shifts in forest species, such as sugar maples moving north out
of the US.
7. Climate change and the resulting rise in sea level are likely to exacerbate
threats to buildings, roads, powerlines, and other infrastructure in climatically
sensitive places. For example, infrastructure damage is related to permafrost
melting in Alaska, and to sea-level rise and storm surge in low-lying coastal
areas.
8. A range of negative health impacts is possible from climate change, but
adaptation is likely to help protect much of the US population. Maintaining our
nation’s public health and community infrastructure, from water treatment
systems to emergency shelters, will be important for minimizing the impacts of
water-borne diseases, heat stress, air pollution, extreme weather events, and
diseases transmitted by insects, ticks, and rodents.
9. Climate change will very likely magnify the cumulative impacts of other
stresses, such as air and water pollution and habitat destruction due to human
development patterns. For some systems, such as coral reefs, the combined
effects of climate change and other stresses are very likely to exceed a critical
threshold, bringing large, possibly irreversible impacts.
10. Significant uncertainties remain in the science underlying regional climate
changes and their impacts. Further research would improve understanding and
our ability to project societal and ecosystem impacts, and provide the public with
additional useful information about options for adaptation. However, it is likely
that some aspects and impacts of climate change will be totally unanticipated as
complex systems respond to ongoing climate change in unforeseeable ways.
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[National Assessment Synthesis Team, 2000, Climate Change Impacts on the United
States: The Potential Consequences of Climate Variability and Change: Overview
Report, U. S. Global Change Research Program, Cambridge University Press,
Cambridge UK, 154 pp., and Foundation Report, 612 pp.
Viewable on-line at www.usgcrp.gov/usgcrp/nacc/default.htm] |
The National Assessment effort did not attempt to come to a bottom line,
believing that a net economic analysis would not be meaningful because the
impacts are varied and intimately tied to how we think about ourselves and our
regions. As a result, questions arise about how one would weigh impacts on
people of different wealth; how to account for those experiencing significant
impacts versus those experiencing small or even positive impacts; how to weigh
impacts that will affect future generations compared to the present generation;
etc. The sense was that having some national entity attempt to convert all of the
various impacts to the single metric of a dollar would be misleading for the public
and for decision makers.
For the rest of the world, the situation is likely even more challenging. This is
especially the case for the developing countries with their less diversified
economies and scanter resources for moderating and adapting to adverse
consequences. In some areas, such as island nations, sea level rise will be most
important, causing serious inundation during storms and exacerbating erosion
problems; for other countries, the shifting boundaries of moist and dry regions
are likely to seriously impact agricultural production; in other areas, the increase
in temperature and absolute humidity is likely to make urban living life miserable;
and in some areas the most important consequences are likely to arise from the
spread of disease vectors and worsened problems of air and water quality.
While there have been attempts to sum up impacts nationally and globally, it is
not at all clear how to properly and fairly compare different impacts. For example,
are the effects of hotter, more humid days on the millions of people in New York
more or less important than the potential flooding of the Marshall Islands and
dislocation of thousands of people 50 to 100 years hence? In considering such
consequences, the Bishops statement on climate change suggests that a simple
economic analysis is not the basis on which to have the discussion. Rather, as
will be discussed more in the accompanying talks, issues of equity and fairness
need to be considered, perhaps even be at the forefront of the public discussion
about what to do.
6. Making the Problem Go Away is Difficult
Even if emissions were to be cut to zero, there would be no further changes in
the climate. Because of the emissions that have already occurred, the world is
likely to experience as much warming in the 21st century as in the 20th century,
partly from the continuing effects of the greenhouse gases and partly as a result
of halting the emissions of the sulfur dioxide that creates the light-colored, sun-
reflecting haze over and downwind of industrial areas. This further climatic
change, however, would not be the most devastating consequence. Because
fossil fuels provide roughly 80% of the world’s energy, the world cannot
immediately give up this source of energy without causing global economic
collapse—a point made often by the major oil and coal companies.
In that doubling the preindustrial concentration of CO2 is likely to cause a global
warming of roughly a few degrees, which would be likely, for example, to cause
the death of most of the world’s coral ecosystems and to initiate melting and the
deterioration of major parts of Greenland and West Antarctic ice sheets, staying
below that concentration level is considered by many to be necessary to avoid
"dangerous anthropogenic interference with the climate system," as called for in
the UN Framework Convention on Climate Change (UNFCCC). Accomplishing
this, however, would require that average per capita emissions worldwide remain
at about the current level of one tonne of carbon per person, averaged over the
21st century. While there can be growth in energy generation and use per capita
above this level by deriving energy from sources other than fossil fuels, coal is at
present the least expensive fuel in many developing countries, so getting energy
from other sources would require diverting money needed for basic survival
needs such as water purification to generation of non-fossil energy. And to
accommodate the growth in carbon emissions for those in the developing world
while limiting the growth in the atmospheric concentration of CO2, there would
need to be sharp cutbacks in the average emission of carbon by those in the
developed world. In that the population of the developing world is several times
as large as that of the developed world, per capita cutbacks in the developed
world would need to be several times as large as the gains of those in the
developing world—each of us would need to cut back enough to allow for the
gain by several others living in the developing world.
Given present trends and emission levels, the world id on a path to considerably
higher emissions than at present—up to 3 to 4 times as much as at present
unless there are much more rapid breakthroughs in non-fossil energy generation
than has been the case. A course with only minimal controls on emissions will
push the world ultimately toward CO2 levels closer to those during the
Cretaceous period of over 65 million years ago, when there was semi-tropical
vegetation at high latitudes and sea level was as much as 200 feet higher due to
the melting of the Greenland and Antarctic ice sheets. While life itself would not
be threatened and dinosaurs would not be expected to return (at least naturally),
the world would be a very different place.
It is this prospect of very significant global warming that led the nations of the
world in 1992 to negotiate the UN Framework Convention on Climate Change,
which set as its objective stabilizing the concentration of CO2 (and some other
gases)—that is, halting the rise. The US Senate nearly unanimously approved
this Convention in 1992, and the US Bishops’ statement supports the need for
such efforts by calling for the stewardship of our environmental heritage.
With the Framework Convention agreed to, the Kyoto Protocol process has
become the first stage in its implementation, taking effect this week, although
importantly without the participation of the US and Australia. Accomplishing the
actual stabilization of the atmospheric concentration of CO2, now or in the future,
however, will require that the entire world population emit no more carbon per
year than the US does today—and the US represents only about 5% of the world
population. In such a case, if everyone were assumed to have the same right to
emissions, we in the US would need to cut our per capita emissions by about
95%. The Kyoto Protocol would have required those in the US to take a major
step in this direction, requiring about a 30% per capita cutback in emissions over
20 years, but that would be only a first step toward the ultimate goal.
In explaining why the US would not sign the Kyoto Protocol, President Bush did
not focus on the challenge of making such a large cut in the per capita
emissions, instead rather disingenuously blaming developing countries for not
participating by cutting their relatively low emissions and complaining how this
cutback would slightly reduce projected economic growth in the US from its near
world-leading position. [When it was first negotiated, the way in which the effect
of the cutback on the US was going to be eased was through an increase in
carbon sequestration and through purchase of carbon emissions permits from
other countries that could less expensively reduce emissions through
mprovements in efficiency. In the later negotiation process, however, these
approaches were either eliminated or tightly restricted, forcing the very large
cutbacks to be made virtually entirely within the US.]
The political posturing about total emissions by country or total emissions by the
developed and developing worlds, is really raising a fundamental ethical issue. It
is said, for example, that emissions by China will soon increase so that their
emissions are larger than those of the US. What is not added in these
explanations is that the population of China is roughly 4 times the population of
the US, so their per capita emissions are about 25% of those in the US. The US
Bishops’ statement takes a different perspective, calling for issues of equity to be
considered along with total emissions, standard of living, and other factors.
At present, the US is really not doing very much; emissions are rising, miles per
gallon has been dropping due to the preferences for small trucks and SUVs, and
few companies and individuals are making strong individual commitments. An
additional challenge is the continuing growth of the US population, which was not
accounted for in the Kyoto Protocol. With the need to meet the energy needs of
the increased number of Americans, the demand for energy is increasing
significantly even while per capita usage is only slowly changing. Much of our
population growth today is due to immigration, and stemming it would run into
a range of other considerations, traditions and outside pressures. However, the
situation could be greatly helped by setting much higher efficiency standards, as,
for example, California has done, and more aggressively pursuing technological
improvements.
The situation in Europe, however, is quite different. Because the European
population is not growing much, and is projected to start declining in some
countries, technological improvements can potentially meet European
requirements under the Kyoto Protocol, in some cases actually also reducing
their costs and improving their energy security. In my opinion, the failure of the
US Administration to adequately explain, and probably even understand, the
differences in the situations facing the US and Europe has been an important
factor in contributing to the misunderstandings about the Kyoto process in the US
and around the world. In addition, the failure of the US to propose a serious
alternative to the commitment to moving forward has seriously exacerbated the
situation, and needs to be remedied.
It is important to remember, however, that the Kyoto Protocol, even if
implemented, will not achieve stabilization of the CO2 concentration in the
atmosphere—in pursuit of that objective, to which we and the world are legally
committed by the UN Framework Convention on Climate Change, the Protocol is
only a first step if the heritage we leave to our grandchildren is going to be
something other than a rapidly warming world.
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