I am John Christy, Professor of Atmospheric Science and Director of the
Earth System Science Center at the University of Alabama in Huntsville or
UAH. I am also Alabama’s State Climatologist and recently served as a Lead
Author of the U.N.’s Intergovernmental Panel on Climate Change.
The concentration of carbon dioxide (CO2) is increasing in the atmosphere due primarily to
the combustion of fossil fuels. Fortunately (because we produce so much of
it) CO2 is not a pollutant. In simple terms, CO2 is the lifeblood of the planet. The vegetation we see
around us would disappear if not for atmospheric CO2.
This green world largely evolved during a period when the atmospheric
CO2 concentration was many times what it is today.
Indeed, numerous studies indicate the present biosphere is being
invigorated by the human-induced rise of CO2. In and
of itself, therefore, the increasing concentration of CO2 does not pose a toxic risk to the planet. In other words,
carbon dioxide means life itself. CO2 is not a
As an aside, it is clear that other emissions may be called pollutants,
e.g. sulfur oxides, nitrogen oxides and mercury. Controlling these is a
completely separate issue from controlling emissions of CO2 and so will
not be discussed here.
It is the secondary impact of increasing CO2 that
may present challenges to human life in the future. It has been proposed
that CO2 increases could cause climate change of a
magnitude beyond what naturally occurs in the climate system so that
costly adaptation or significant ecological stress might occur. For
example, enhanced sea level rise and/or reduced rainfall would be two
possible effects likely to be costly to those regions so affected. Data
from the past and projections from climate models are employed to provide
insight on these concerns.
Will increases in CO2 affect the climate
significantly? Are significant changes occurring now? Climate models
suggest the answer is yes, real data suggests otherwise. Climate models
attempt to describe the ocean/atmospheric system with equations which
approximate the processes of nature. No model is perfect because the
natural system is incredibly complex. One modest goal of model simulations
is to describe and predict the evolution of the ocean/atmospheric system
in a way that is useful to discover possible environmental hazards which
lie ahead. The goal is not to achieve a perfect forecast for every type of
weather in every unique geographic region, but to provide information on
changes in large-scale features. If in testing models one finds conflict
with even the observed large scale features, this would suggest that at
least some fundamental processes, for example heat transfer, are not
adequately described in the models.
A common feature of climate model projections with CO2 increases is a rise in the global surface temperature as
well as an even more rapid rise in the layer up to 30,000 feet called the
Over the past 24+ years various calculations of surface temperature
indeed show a rise of about 0.7 °F. This is roughly half of the total rise
observed since the 19th century. In the lower troposphere, however,
various estimates which include the satellite data Dr. Roy Spencer of UAH
and I produce, show much less warming, about 0.3 °F – an amount less than
half that observed at the surface. The real world shows less warming in
the atmosphere, not more as models predict. Are these data reliable?
A new version of the microwave satellite data has been produced, but
not yet published, by Remote Sensing Systems or RSS of California. Two
weeks ago a paper was published in Science magazine’ electronic
edition which used a curious means of testing our UAH version against
RSS. The paper cited climate
model results which agreed more with RSS, because RSS data showed about
0.4°F more warming than UAH’s data for this same layer called the
mid-troposphere. UAH’s total warming for this layer was about 0.05°F.
(This layer is higher in the atmosphere than the lower
troposphere mentioned earlier with its 0.3°F warming.) The strong
implication of the paper was that since RSS was more consistent with the
model output, it was likely a more accurate dataset than ours.
That same week, with much less fanfare, my latest paper appeared in the
Journal of Atmospheric and Oceanic Technology. Unlike the paper in Science
magazine, I performed several rigorous tests to estimate the potential
error of our UAH satellite data. I used real observations from balloon
datasets created by independent organizations, some with data from as many
as 400 different balloon stations. Our UAH satellite data and the balloon
data corroborated each other with remarkable consistency, showing only a
slow warming of the bulk of the atmosphere. This evidence indicates that
the projected warming of the climate model had little consistency with the
real world. This is important because the quantity examined here, lower
tropospheric temperature, is not a minor aspect of the climate system.
This represents most of the bulk mass of the atmosphere, and hence the
climate system. The inability of climate models to achieve consistency on
this scale is a serious shortcoming and suggests projections from such
models be viewed with great skepticism.
Changes in surface temperature have also been a topic of controversy.
The conclusion in IPCC 2001 that human induced global warming was clearly
evident was partly based on a depiction of the Northern Hemisphere
temperature since 1000 A.D. This depiction showed little change until
about 1850, then contains a sharp upward rise, suggesting that recent
warming was dramatic and linked to human effects. Since IPCC 2001, two important papers have shown
something else. Using a wider
range of information from new sources these studies now indicate large
temperature swings have been common in the past 1000 years and that
temperatures warmer than today’s were common in 50-year periods about 1000
years ago. These studies suggest that the climate we see today is not
unusual at all.
WEATHER EXTREMES AND CLIMATE CHANGE
I want to encourage the committee to be suspicious of media reports in
which weather extremes are given as proof of human-induced climate change.
Weather extremes occur somewhere all the time. For example, in the year
2000 the 48 conterminous states, the U.S. experienced the coldest combined
November and December in 106 years. We’ve just again witnessed a colder
than average winter in the Eastern US with some record snowfalls here and
there, while the California mountains had one of the coldest and snowiest
April’s ever. However, looking at these events does not prove the country
is experiencing global cooling any more than a hot July represents global
Has hot weather occurred before in the US? In my region of Alabama, the
19 hottest summers of the past 108 years occurred prior to 1955. In the
midwest, of the 10 worst heatwaves, only two have occurred since 1970, and
they placed 7th and 8th . Hot weather has happened before and will happen
again. Such events do not prove climate change is occurring.
Similar findings appear from an examination of destructive weather
events. The intensity and frequency of hurricanes have not increased. The
intensity and frequency of tornadoes have not increased. The same is true
for thunderstorms and hail. (Let me quickly add that
we now have more people and much more wealth in the paths of these
destructive events so that the losses have certainly risen, but that is
not due to climate change but to progress.) Droughts and wet spells
have not statistically increased or decreased. In a paper published last
year I demonstrated from a rigorously constructed temperature dataset for
North Alabama that summer temperatures there have actually declined since
the 19th century. Similar
results have been found within states from California to Georgia.
One century is a relatively short time in terms of climate time scales.
When looking at proxy records of the last 2000 years for drought in the
Southwest, the record suggests the worst droughts occurred prior to 1600.
The dust bowl of the 1930’s appears as a minor event on such a time scale.
This should be a warning that with or without any human influence on
climate we should be prepared for a significant, multi-year drought. (Low cost energy would help mitigate the costs of
transporting water to the stricken areas.)
When considering information such as indicated above, one finds it
difficult to conclude the climate change is occurring in the US and that
it is exceedingly difficult to conclude that part of that change might
have been caused by human factors.
In the past 150 years, sea level has risen at a rate of 6 in. ± 4 in.
(15 cm ± 10 cm) per century and is apparently
not accelerating. Sea level also rose in the 17th and 18th centuries,
obviously due to natural causes, but not as much. Sea level has been
rising naturally for thousands of years (about 2 in.
per century in the past 6,000 years). If we look at ice volumes of
past interglacial periods and realize how slow ice responds to climate, we
know that in the current interglacial period (which
began about 11,000 years ago) there is still more land ice
available for melting, implying continued sea level rise with or without
One of my duties in the office of the State Climatologist is to inform
developers and industries of the potential climate risks and rewards in
Alabama. I am very frank in pointing out the dangers of beach front
property along the Gulf Coast. A sea level rise of 6 in. over 100 years,
or even 50 years is minuscule compared with the storm surge of a powerful
hurricane like Fredrick or Camille. Coastal areas threatened today will be
threatened in the future. The sea level rise, which will continue, will be
very slow and thus give decades of opportunity for adaptation, if one is
able to survive the storms.
The main point I stress to state and local agencies as well as
industries is that they invest today in infrastructure that can withstand
the severe weather events that we know are going to continue. These
investments include extending flood way easements, improvements in storm
water drainage systems and avoiding hurricane-prone coastal development,
among other actions. There are ways to reduce our vulnerabilities (i.e. enhancing our resilience) by increasing the
investment today in the proper infrastructure or by avoiding future
disasters with common sense building regulations. Our economy is affected
much more by these extreme events which arrive every few years or decades
versus whatever slow changes may occur due to human-induced climate
change. The economic payoff would be tangible for such investments. The
payoff for restricting energy use and economic activity for an unknown
(and likely unknowable) future based on climate
change scenarios is much less profitable for all concerned.
KYOTO’S IMPACT ON CLIMATE AND ECONOMY
One week ago today, the BBC published a report noting that the European
Union has again exceeded their annual carbon dioxide targets under the
Kyoto agreement. So, in countries with apparently strong motivation for
reducing carbon dioxide the treaty is failing. But that really is not a
problem. (Under the Kyoto Treaty the U.S. was asked to
reduced CO2 emissions 7% below 1990
There have been many proposals to reduce CO2
emissions, some in this country, both more and less harsh than the Kyoto
Protocol. In one way or another, each proposal seeks to limit energy usage
through direct or indirect increases of the cost over market prices. A
fundamental fact that our nation needs to understand is that any of these
proposals if implemented, will have an effect on the climate so small that
we would not be able to detect it. This is something I can speak to as my
work focuses on precise measures of climate quantities. The evidence
convinces me that none of these proposals would change to a noticeable
degree whatever the climate is going to do. Raising the cost of energy
with no detectable result generally falls into the category of a waste of
I am decidedly an optimist about this situation. Our country is often
criticized for producing 25% of the world’s anthropogenic CO2. However, we are rarely recognized and applauded for
producing, with that same CO2, 31% of what the world
wants and needs; it’s food, technology, medical advances, defense of
freedom, and so on. Today this
is done primarily with the burning of carbon, but in the future will come
from other inexpensive and efficient sources. For example, the US produces
a unit of GDP using about 55% of the energy required to produce the same
unit in 1970. The U.S. is decarbonizing its economy and this will
continue. Even though carbon dioxide is not a pollutant, and energy from
carbon allows people to live better lives, we can look forward to new
sources of energy as the genius of America works on the next source of
I often mention that early in my career I served as a missionary in
Africa. I lived upcountry with people who did not have access to useful
energy. Put simply, access to energy means life, it means a longer and
better life. I watched as women walked in the early morning to the forest
edge, often several miles away, to chop wet green wood for fuel. They
became beasts of burden as they carried the wood on their backs on the
return trip home. Wood and dung are terrible sources of energy, with low
useful output while creating high pollution levels. Burning wood and dung
inside the homes for cooking and heat created a dangerously polluted
indoor atmosphere for the family. I always thought that if each home could
be fitted with an electric light bulb and a microwave oven electrified by
a coal-fired power plant, several good things would happen. The women
would be freed to work on other more productive pursuits, the indoor air
would be much cleaner so health would improve, food could be prepared more
safely, there would be light for reading and advancement, information
through television or radio would be received, and the forest with its
beautiful ecosystem could be saved. Access to inexpensive, efficient
energy would enhance the lives of the Africans while at the same time
enhance the environment.
There are parallels in this country. Any of the proposals to reduce
energy consumption by mandate (promoted in the state
legislatures and the Congress) would do nothing measurable to
reduce the climate impacts of CO2. However, they would
cause increases in energy costs (i.e. taxes).
These additional taxes would fall disproportionately on the poor, who buy
gasoline and home-heating at the same rate as everyone else. Their lives
would be made more precarious as a result.
In Hearings such as this we are often asked at the close, "If you were
a congressman for a day, what would you do on this issue? " My answer is
two fold. First, I would do no harm, I would not force energy prices up
and thereby hurt the U.S. economy in general and the poor in
particular. Second, I would
help America do what the innovative people of this nation do the best,
help scientists and engineers discover the next source of low carbon
energy, while building up our resilience to weather events, like floods,
droughts, tornadoes, hurricanes that we know are going to continue,
climate change or not.
 Santer, B., et al., 2003. Influence of Satellite Data Uncertainties
on the Detection of Externally-Forced Climate Change. ScienceExpress,
Christy, J.R. et al., 2003. Error
estimates of Version 5.0 of MSU-AMSU bulk atmospheric temperatures.
Journal of Atmospheric and Oceanic Technology,
 Mann, M.E., R. S. Bradley, and M.K. Hughes, 1999:
Northern Hemisphere temperatures during the past millennium: Inferences,
uncertanties, and limitations. Geophys. Res. Lett., 26,
 Soon, W. and S. Baliunas, 2003: Proxy climatic and
environmental changes of the past 1000 years. Clim. Res., 23, 89-110.
Esper, J. E.R. Cook, F.H. Schweingruber, 2002: Low-frequency signals in
long tree-ring chronologies for reconstructing past temperature
variability. Science 295, 2250-2253.
 Christy, J.R., 2002: When
was the hottest summer? A State Climatologist struggles for an answer.
Bull. Amer. Meteor. Soc. 83, 723-734.
 World Development
Indicators, World Bank 2001 (for year 2000), US is $9,388B, World is
 Energy Information Administration, Impacts of the
Kyoto Protocol on U.S. Energy and Economic Activity (Washington D.C.: U.S.
Department of Energy), http://www.eia.doe.gov/neic/press/press109.htmll. Costs
estimated for a reduction of CO2 by 3 % (not Kyoto’s 7 %) below 1990
emissions are between $125 and $280 billion per year of an economy of
$9,425 billion, or about 1 to 3