Confronting the Climate Change Crisis

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Confronting the Climate Change Crisis

Confronting the

Climate

Change

Crisis

28

Healthy coral reefs support many

species, but they now are dying

off at unprecedented rates, largely

due to rising ocean temperatures.

What Is the

Evidence,

and What Can

We Do About It?

www.solartoday.org SOLAR TODAY


CHUCK KUTSCHER

By Chuck Kutscher

Energy efficiency and renewable energy

technologies will play major roles in

addressing global warming.

While the media finally appear to be sounding

the alarm for global warming, climate

scientists who publish in the peer-reviewed

literature have agreed for years that

mankind is changing the climate. Yet polls

show that many Americans believe it is

simply a natural variation. What evidence has scientists so

convinced that we are to blame, and what can we do about it?

Examining the Science

Since the early 1800s, we have known that various atmospheric

gases, acting like the glass in a greenhouse, transmit incoming

sunlight but absorb outgoing infrared radiation, raising the average

air temperature at the Earth’s surface. Although these socalled

greenhouse gases are present in very small amounts,

without them the average temperature would be about 33°C

(60°F) colder than it is today. Other atmospheric constituents

like aerosols — suspended particles in the air — released by fossil-fueled

power plants, tend to lower the temperature by

blocking sunlight. Climate scientists compare the effects of

these gases and constituents in terms of radiative “forcings,”

or how much they change the net heat flux (the difference

between incoming solar radiation and the outgoing infrared

radiation) on the Earth’s surface. Figure 1 shows the radiative

forcings in watts per square meter as determined by the Intergovernmental

Panel on Climate Change (IPCC), an international

collaborative of scientists and government representatives

established to study global warming.

Carbon dioxide (CO2), a major byproduct of fossil fuel

combustion, is the most influential greenhouse gas. Although

methane (CH4) is about 20 times as powerful a greenhouse gas

on an equal volume basis, it is present in lesser amounts, is

shorter-lived when added to the atmosphere, and thus is less

important than carbon dioxide.

The most compelling evidence for climate change lies

in the so-called paleoclimatic data. In the 1980s scientists

began drilling for ancient ice-core samples in Greenland and

Antarctica. Seasonal depositions of snow leave distinct lines

in the ice, which, much like tree rings, serve as a time scale.

By analyzing air bubbles trapped in the ice when it formed,

scientists can determine the content of greenhouse gases and

even the average temperature at each point in time. The data

(figure 2 on page 30) show that over the past 420,000 years, the

temperature and greenhouse gas content of the atmosphere

has varied in 100,000-year cycles between about 180 parts per million

(ppm) by volume to a maximum of about 290 ppm. (This

is due to changes in the distribution of solar radiation associated

with natural variations in the Earth’s orbit.) And the

Earth’s temperature has closely tracked the greenhouse gas

concentration. Other techniques, such as the study of ocean fossils,

reinforce the ice-core data.

Around 1850, when the CO2 level was still stable at about 280

ppm, the level began to spike. It has now reached the unprecedented

value of 380 ppm — a 36 percent increase over the preindustrial

value — and is rising at about 2 ppm per year. In figure

2, the time scale from 1850 to the present has been expanded

to reveal the shape of the trend, but if plotted on the time scale

of the rest of the chart, the rises in greenhouse gases and temperature

would appear as vertical lines. Scientists now know that an

increase in temperature can release CO2 from the ground and seawater,

and, conversely, a rise in greenhouse gases will cause a rise

in temperature, so the two effects reinforce each other.

Not only has fossil-fuel burning released greenhouse gases, but

it has created air pollution in the form of aerosols like sulfur

dioxide. To some extent, these have counterbalanced greenhouse

heating by reflecting some sunlight away, and models show that

this explains a slight decline in the Earth’s temperature between

1940 and about 1970. Air pollution continues to block some

sunlight. However, with tighter air-quality standards and rapidly

increasing amounts of greenhouse gases, the greenhouse effect

July/August 2006 29


Confronting the Climate Change Crisis | What Is the Evidence?

is now the dominant net effect of fossil fuel combustion. In the

last 30 years, the average temperature at the Earth’s surface has

risen at the rate of 0.2°C (0.36°F) per decade.

If one considers all the heat flux that human activities have

added to the planet since 1850, it amounts to about 1.6 watts per

square meter over the Earth’s surface. The ice-core data reveal that

this amount of heating will increase the Earth’s temperature by

1.2°C (2.2°F). The temperature thus far has risen by about 0.7°C

(1.3°F) since the Industrial Revolution. So even if we stop adding

any more greenhouse gases, another 0.5°C (0.9°F) temperature rise

is already built in.

In actuality we are emitting even more greenhouse gases,

meaning that the radiation imbalance will grow and the temperature

will continue to rise at an increasing pace. The year 2005 was

the warmest year ever recorded — slightly higher than the previous

record year of 1998 (see figure 3). The high temperature in

2005 is especially significant because, unlike 1998, 2005 had no

El Niño to boost the temperature.

Weighing the Consequences

Since the last ice age, the Earth has been in a warm period

for about 8,000 years, which is relatively rare in our planet’s history.

It is only during this extended warm period that civilization

has blossomed. Clearly, however, an exploding human

population burning more and more fossil fuels now has a greater

effect on the climate than do natural mechanisms. The atmosphere

can no longer be viewed as an infinite sink into which we

can dump our wastes.

What are the consequences of not addressing our carbon emissions?

The IPCC has identified the potential impacts, and many

can already be observed. They include sea-level rise and earlier

spring runoffs in many areas, resulting in increased summer

drought in some regions. Drought conditions are expected to

become worse in Africa, where millions already face famine.

Storm severity will increase due to the additional energy in the

atmosphere. A new study indicates that the high intensity of

recent hurricanes cannot be explained by the normal 75-year

cycle of hurricane activity. Low-lying coastal areas like the Florida

and Gulf coasts will be more prone to storm surge.

Ninety-eight percent of mountain glaciers are shrinking, and

their disappearance will result in severe water shortages for millions

worldwide. Global warming is also expected to increase the

strength of El Niño events that warm the Pacific, resulting in more

so-called “super El Niños” like those that occurred in 1983 and

1997-98. These extreme El Niños are associated with severe weather-related

events, including floods, heat waves, mudslides,

drought, wildfires and famine.

Plants, animals and humankind will find it difficult to adapt

because the changes are occurring so quickly. Because different

species will react to the changing conditions differently, the food

chain will be interrupted. The projected additional 3°C rise in temperature

this century would place the Earth’s temperature very close

to levels that existed during mass extinctions when more than 50

percent of species were lost. One study has indicated that up to onethird

of the Earth’s species could become extinct by the year 2050

as a result of climate change. Already global warming has been

blamed for outbreaks of a fungus that has resulted in the extinction

30

of dozens of colorful frog species in Central and South America.

In many cases, insects and germs will spread beyond their current

boundaries; we are now seeing insect-borne diseases of the

tropics, like West Nile Virus, appearing in northern climates.

Coral reefs, which provide sea life critical to the economies of

island nations and which offer a promising source of life-saving

drugs, can survive only in a narrow temperature band. They show

unprecedented die-off largely due to warming oceans. Reports

from the U.S. Virgin Islands indicate that during a recent fourmonth

period of elevated sea temperatures, as much as one-third

of the coral has died.

We now know that the climate has many “positive feedback”

mechanisms, which reinforce changes and can result in “tipping

points” beyond which irreversible changes occur. It is because of

positive feedback that the Arctic is the region hardest hit by climate

change. As the ice melts, the resulting darker water and

ground absorb more sunlight, exacerbating the warming. The average

air temperature in Alaska has risen 2.8°C (5°F) in just the last

50 years. This warming has caused permafrost to melt, undermining

building foundations and even forcing the relocation of

entire villages.

Unlike an ice cube melting slowly on a countertop, the destruction

of ice sheets is a highly dynamic, nonlinear (i.e., with positive

feedback) process. The melt water flows like a river, causing

rapid heat transfer and erosion. The melt water also lubricates the

www.solartoday.org SOLAR TODAY


How much do we need to reduce carbon emissions? The key is to decide

what additional temperature rise can be tolerated.

base of ice sheets, causing them to move faster. Scientists in

Greenland have found that these positive feedback mechanisms

have greatly accelerated the melting of the ice sheets. To make

matters worse, methane and carbon dioxide are released from

newly exposed soil as it heats up, promoting still more greenhouse

warming.

Tackling the Problem

According to the Energy Information Administration, 82 percent

of U.S. greenhouse gas emissions (about 1.6 billion metric

tons of carbon, or GtC, per year) are in the form of carbon dioxide

resulting from the burning of fossil fuels. (One metric ton is

1,000 kilograms.) That represents 23 percent of the world’s total

CO2 emissions — a large proportion considering that we have only

5 percent of the world’s population. Electricity production

accounts for 42 percent of our total carbon emissions, and the

burning of transportation fuels accounts for 32 percent. So targeting

electricity generation and transportation fuels will address

about three-quarters of our CO2 emissions.

How much do we need to reduce carbon emissions? The key is

to decide what additional temperature rise can be tolerated. Studies

show that if no action is taken, the most probable rise in the

average air temperature at the Earth’s surface by the end of this century

is about 3°C (5.4°F) above the year 2000 value; much higher

increases are possible. Sea level will rise due to both the thermal

expansion of the oceans and the melting of land-based ice sheets.

The last time the Earth’s temperature was that high was 3 million

years ago, when sea level ultimately reached 25 meters (82 ft)

higher than today. Estimates of how quickly sea level may reach

such a height vary. The latest measurements of rapid melting in

Greenland suggest that the IPCC’s model-based projection for a

maximum rise of 0.9 m (3 ft) by 2100 may be too conservative.

NASA climate scientist Jim Hansen has suggested that once the

temperature reaches 2°C to 3°C above the year 2000 value, the disintegration

of ice sheets would be irreversible and sea level could

rise 6 m (20 ft) within a century. That could reshape the world’s

coastlines, with dire consequences for the world’s large coastal

populations. Hansen has argued that we must aim to keep the

additional temperature rise to less than 1°C (1.8°F) above the 2000

value to ensure that the sea-level rise will be less than 1 m and to

minimize the loss of species. He has argued that a target CO2 level

of 475 ppm could be sufficient to limit the temperature rise to 1°C

if we simultaneously reduce methane emissions by a factor of two.

Stephen Pacala and Robert Socolow of Princeton have

described a simplified scenario that would allow the CO2 to level

out at 500 ppm. It involves limiting world CO2 emissions to the

current rate of 7 GtC per year for 50 years, followed by substantial

emissions reductions. The amount of carbon emissions that

would be displaced over the next 50 years can be represented

roughly by the difference between the rising business-as-usual

level of emissions and the current level, which Pacala and

Socolow approximate with a triangle on a graph of emissions versus

time (see figure 4 on page 32). The triangle has an area of 175

GtC. Because that is an immense amount of carbon emissions,

Pacala and Socolow divide the triangle into seven smaller

“wedges,” each having an area of 25 GtC. They then hypothesize

various possible mechanisms that can each displace 25 GtC.

The mechanisms fall into five categories: energy conservation/efficiency,

renewable energy, enhancing natural sinks (such as

smarter land use), nuclear energy, and management of fossil

energy (capturing and storing carbon and switching from coal to

natural gas).

What does this mean for the United States? World carbon

emissions are split roughly evenly between developed and developing

countries. If the developing countries limit their increase

in emissions to 60 percent between now and 2050, we in the

industrialized countries will need to reduce our emissions at the

same rate to keep world emissions constant. Accounting for a projected

business-as-usual 1.2 percent U.S. carbon-growth rate, this

will require the United States to displace about 55 GtC, or about

two wedges, of carbon emissions over the next 50 years. This

means an average carbon displacement rate of about 1 GtC per

July/August 2006 31


Confronting the Climate Change Crisis | What Is the Evidence?

year, which is two-thirds of our current emission rate. To put this

amount of carbon-free energy in perspective, it is approximately

equivalent to displacing a typical 500-megawatt (MW) U.S. coal

plant every week for the next 50 years. (Even with such large carbon

reductions, our per capita emissions, now at five times the

world average, would still be twice the world average.)

So how can we achieve such large decreases in emissions?

The first priority is to address opportunities to improve energy efficiency,

especially at the point of use. In the buildings sector,

energy-efficient appliances, windows, lighting, air conditioners

and insulation have already made a big impact, and these measures

hold great promise to further reduce our electricity consumption.

In the transportation sector, expanded deployment of

32

public transportation and the use of lightweight materials and

improved aerodynamics can significantly reduce carbon emissions.

In the industrial sector, more efficient motors and piping systems

and the use of heat recovery offer significant opportunities. The

Rocky Mountain Institute has estimated that a combination of

these measures could save 0.7 GtC per year by 2025 at costs of less

than 6 cents per kilowatt-hour of saved energy. This represents

more than half of the U.S. carbon reduction needed.

But we must also address energy supply. Consider first electricity.

Coal- and natural gas-burning plants are responsible for most

emissions from electricity generation. Coal is the bigger problem

because it is more widely used, contains more carbon and is

burned in plants with lower overall efficiencies. It is also likely to

remain less expensive than imported liquid natural gas. To produce

electricity, we have three alternatives to coal- and gas-burning:

1) capturing the carbon emissions and storing them, 2)

expanding our usage of nuclear power, and 3) switching to renewable

sources (wind, solar, biomass and geothermal).

Carbon capture and sequestration offers promise. By gasifying

coal, it is possible to create hydrogen fuel and capture the carbon

dioxide. This carbon dioxide can then be pumped at high pressure

into geologically stable reservoirs. However, even tiny leakage

rates of CO2 into the atmosphere could defeat the whole

purpose (and be deadly to nearby populations). So sequestration

must first be demonstrated to work safely on a large scale, and several

demonstration projects are under way. The environmental

issues associated with mining the coal would remain, however.

Nuclear power is essentially carbon-free. Nuclear fusion offers hope

for the distant future, but presents an enormous technical challenge.

Fission is the only viable nuclear option in the near term. However,

the electricity from new nuclear power plants would be relatively

expensive, and nuclear faces significant obstacles. The biggest

challenges are interrelated: the disposal of radioactive waste and, for

international development, the threat of nuclear proliferation (as

underscored by current concerns with Iran’s program). New U.S.

plants also require long licensing times, so it would be at least a decade

before any additional nuclear power could be brought to bear on the

climate-change problem, even if the obstacles can be overcome.

Some have proposed limiting U.S. nuclear power to simply building

new plants on current sites as the existing plants are retired.

Of the three electricity-generation alternatives, only renewable

energy causes no additional environmental problems, can be

applied immediately to mitigating the crisis and is completely sustainable.

The major challenges are cost, intermittency of supply

(necessitating some form of storage), and the transmission distance

between the resources and the end use.

A recent study by the Western Governors’ Association demonstrated

how much electricity could be produced in the West by

solar, wind and geothermal sources. For example, in the case of

solar energy, prime sites for concentrating (parabolic trough)

solar power plants could provide 200 gigawatts of electricity in California,

Nevada, Arizona and New Mexico at estimated costs

ranging from 7 to 16 cents per kilowatt-hour. That is approximately

twice the current electric-generating capacity of the region

(20 percent of national demand) and would provide about 10 percent

of the U.S. carbon reduction needed (assuming the plants

have six hours of thermal storage).

www.solartoday.org SOLAR TODAY


To reach targeted carbon-emissions reductions,

the United States will need to displace the equivalent of

a typical 500-megawatt U.S. coal plant every week for the next 50 years

While centralized concentrating solar power and geothermal

electric plants are primarily limited to the Southwest, every part

of the United States has access to some form of renewable energy

(see figure 5). Based on the latest estimates by researchers at the

National Renewable Energy Laboratory, a combination of wind,

concentrating solar power, biomass and rooftop photovoltaics

could de-carbonize the U.S. electric grid, assuming dispatchability

and transmission issues can be adequately addressed. How fast

this may occur depends on many factors, including manufacturing

scale-up rate, materials-supply issues and policy measures.

What about transportation fuels? They represent the most rapidly

growing source of carbon emissions. Burning a gallon of gasoline

in a vehicle results in the emission

of about 3 kilograms (6.6 lb) of

carbon (accounting for both fuel

production and combustion). Thus

an average car emits more than a

ton of carbon per year.

Hybrid vehicles represent an

important advance. Interest in the

development of flexible-fuel, plugin

hybrids is growing, largely

because of the recognized need to

reduce our oil imports. A hybrid

electric vehicle with enough battery

storage to cover a distance of

10 to 20 miles in electric-only

mode and the ability to be plugged

into the grid to be recharged

overnight would result in a gas

mileage of greater than 100 mpg.

At today’s gasoline and electricity

prices, such a vehicle would also be

much cheaper to operate. The batteries

provide distributed storage,

which makes the electric grid more

secure and helps address the dispatchability

issue associated with wind power. The use of biofuel

blends with plug-in hybrids would result in further reductions

in net carbon emissions.

The Next Step

We face a daunting challenge. We will have to adapt to a certain

amount of environmental damage resulting from our carbon

emissions to date, while aggressively reducing our emissions to

avoid the worst consequences. Unwilling to wait for a federal commitment,

leaders in state and city governments have forged ahead

to address climate change. Regional carbon cap-and-trade initiatives,

a national coalition of mayors and renewable portfolio

standards that now exist in 22 states, all will have an impact.

However, only a comprehensive, bipartisan federal effort

that is initiated very soon can help us avoid a dangerous tipping

point in the climate. The longer we wait to act, the more

difficult the problem becomes. As was the case with the ozone

problem, a well-informed public will likely play a key role in

spurring action.

History shows that intelligent regulation works faster than

volunteer programs. For example, a legislated cap on sulfur dioxide

emissions with provision for tradable allowances has greatly

reduced air pollution and acid rain in the United States

through market forces. A similar national carbon cap-and-trade

policy could stimulate carbon reduction. Other measures such as

increased CAFE standards for vehicles, more rigorous appliance

standards and various federal policy incentives can also have a

large impact.

Although some business groups have expressed concern

about the potential impact on our economy, corporations

such as DuPont and IBM have reduced their carbon emissions

and improved their profitability in the process. We

must consider the enormous costs of environmental damage

if we do not begin to address the problem and focus on the

economic opportunities that carbon mitigation offers. If we

have learned anything from Hurricane Katrina, it is that the

cost of preventing environmental disaster pales in comparison

to the cost of recovering from it. As Pacala and Socolow

note, it will require a combination of approaches to solve

this problem. Energy efficiency and renewable energy will

play major roles. ●

Dr. Chuck Kutscher (ckutscher@ases.org) is general chair of the

SOLAR 2006 conference, taking place July 7-13 in Denver with the

theme, “Renewable Energy: Key to Climate Recovery.” Top climate

change scientists including NASA’s Jim Hansen, NCAR’s Warren

Washington, Princeton Professor Robert Socolow and NYU Professor

Emeritus Marty Hoffert will describe the latest science on this global

threat. Experts in renewable energy and energy efficiency will

discuss how these technologies can help reduce U.S. carbon emissions.

The various theme-related presentations will be published by the

American Solar Energy Society in a special postconference report.

July/August 2006 33

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