1. Global Warming
National Oceanic and Atmospheric Administration
National Climatic Data Center
Global Warming
What is Global Warming?
Global Warming is the increase of Earth's average surface temperature due to effect of
greenhouse gases, such as carbon dioxide emissions from burning fossil fuels or from
deforestation, which trap heat that would otherwise escape from Earth. This is a type
ofgreenhouse effect.
Is global warming, caused by human activity, even remotely plausible?
Earth's climate is mostly influenced by the first 6 miles or so of the atmosphere which
contains most of the matter making up the atmosphere. This is really a very thin layer if
you think about it. that on this short journey he had traveled a distance equal to that of
the layer of the atmosphere where almost all the action of our climate is contained. In
fact, if you were to view Earth from space, the principle part of the atmosphere would
only be about as thick as the skin on an onion! Realizing this makes it more plausible to
suppose that human beings can change the climate. A look at the amount of greenhouse
gases we are spewing into the atmosphere makes it even more plausible.
What are the Greenhouse Gases?
The most significant greenhouse gas is actually water vapor, not something produced
directly by humankind in significant amounts. However, even slight increases in
atmospheric levels of carbon dioxide (CO2) can cause a substantial increase in
temperature.
Why is this? There are two reasons: First, although the concentrations of these gases are
not nearly as large as that of oxygen and nitrogen (the main constituents of the
atmosphere), neither oxygen or nitrogen are greenhouse gases. This is because neither
has more than two atoms per molecule (i.e. their molecular forms are O 2 and N2,
respectively), and so they lack the internal vibrational modesthat molecules
with more than two atoms have. Both water and CO2, for example, have these "internal
vibrational modes", and these vibrational modes can absorb and reradiate infrared
radiation, which causes the greenhouse effect.
Secondly, CO2 tends to remain in the atmosphere for a very long time (time scales in the
hundreds of years). Water vapor, on the other hand, can easily condense or evaporate,
depending on local conditions. Water vapor levels therefore tend to adjust quickly to the
prevailing conditions, such that the energy flows from the Sun and re-radiation from the
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2. Earth achieve a balance. CO2 tends to remain fairly constant and therefore behave as
a controlling factor, rather than a reacting factor. More CO2 means that the balance
occurs at higher temperatures and water vapor levels.
How much have we increased the Atmosphere's CO2 Concentration?
Human beings have increased the CO2 concentration in the atmosphere by about thirty
percent, which is an extremely significant increase, even on inter-glacial timescales. It is
believed that human beings are responsible for this because the increase is almost
perfectly correlated with increases in fossil fuel combustion, and also due other
evidence, such as changes in the ratios of different carbon isotopes in atmospheric
CO2 that are consistent with "anthropogenic" (human caused) emissions. The simple
fact is, that under "business as usual" conditions, we'll soon reach carbon dioxide
concentrations that haven't been seen on Earth in the last 50 million years.
Combustion of Fossil Fuels, for electricity generation, transportation, and heating, and
also the manufacture of cement, all result in the total worldwide emission of about 22
billion tons of carbon dioxide to the atmosphere each year. About a third of this comes
from electricity generation, and another third from transportation, and a third from all
other sources.
This enormous input of CO2 is causing the atmospheric levels of CO2 to rise
dramatically. The following graph shows the CO2 levels over the past 160
thousand years (the upper curve, with units indicated on the right hand side of the
graph). The current level, and projected increase over the next hundred years if we do
not curb emissions, are also shown (the part of the curve which goes way up high, to the
right of the current level, is the projected CO2 rise). The projected increase in CO2 is
very startling and disturbing. Changes in the Earth's average surface temperature are
also shown (the lower curve, with units on the left). Note that it parallels the CO 2 level
curve very well.
Is the Temperature Really Changing?
Yes! As everyone has heard from the media, recent years have consistently been the
warmest in hundreds and possibly thousands of years. But that might be a temporary
fluctuation, right? To see that it probably isn't, the next graph shows the average
temperature in the Northern Hemisphere as determined from many sources, carefully
combined, such as tree rings, corals, human records, etc.
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3. These graphs show a very discernable warming trend, starting in about 1900. It might
seem a bit surprising that warming started as early as 1900. How is this possible? The
reason is that the increase in carbon dioxide actually began in 1800, following the
deforestation of much of Northeastern American and other forested parts of the world.
The sharp upswing in emissions during the industrial revolution further added to this,
leading to a significantly increased carbon dioxide level even by 1900.
Thus, we see that Global Warming is not something far off in the future - in fact it
predates almost every living human being today.
How do we know if the temperature increase is caused by anthropogenic
emissions?
Computer models strongly suggest that this is the case. The following graphs show that
1) If only natural fluctuations are included in the models (such as the slight increase in
solar output that occurred in the first half of the 20th century), then the large warming
in the 20th century is not reproduced. 2) If only anthropogenic carbon emissions are
included, then the large warming is reproduced, but some of the variations, such as the
cooling period in the 1950s, is not reproduced (this cooling trend was thought to be
caused by sulfur dioxide emissions from dirty power plants). 3) When both natural and
anthropogenic emissions of all types are included, then the temperature evolution of the
20th century is well reproduced.
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4. Is there a connection between the recent drought and climate change?
Yes. A recent study by the National Oceanic and Atmospheric Administration gives
strong evidence that global warming was a major factor.
Who studies global warming, and who believes in it?
Most of the scientific community, represented especially by the Intergovernmental
Panel on Climate Change (IPCC - www.ipcc.ch), now believes that the global warming
effect is real, and many corporations, even including Ford Motor Company, also
acknowledge its likelihood.
Who are the IPCC?
In 1998, the Intergovernmental Panel on Climate Change (IPCC) was established by the
World Meteorological Organization (WMO) and the United Nations Environment
Programme (UNEP), in recognition of the threat that global warming presents to the
world.
The IPCC is open to all members of the UNEP and WMO and consists of several
thousand of the most authoritative scientists in the world on climate change. The role of
the IPCC is to assess the scientific, technical and socio-economic information relevant
for the understanding of the risk of human-induced climate change. It does not carry
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5. out new research nor does it monitor climate related data. It bases its assessment
mainly on published and peer reviewed scientific technical literature.
The IPCC has completed two assessment reports, developed methodology guidelines for
national greenhouse gas inventories, special reports and technical papers. Results of the
first assessment (1990--1994): confirmed scientific basis for global warming but
concluded that ``nothing to be said for certain yet''. The second assessment (1995),
concluded that `` ...the balance suggests a discernable human influence on global
climate'', and concluded that, as predicted by climate models, global temperature will
likely rise by about 1-3.5Celsius by the year 2100. The next report, in 2000, suggested,
that the climate might warm by as much as 10 degrees Fahrenheit over the next 100
years, which would bring us back to a climate not seen since the age of the dinosaurs.
The most recent report, in 2001, concluded that "There is new and stronger evidence
that most of the warming observed over the last 50 years is attributable to human
activities".
Due to these assessments, debate has now shifted away from whether or not global
warming is going to occur to, instead, how much, how soon, and with what impacts.
Global Warming Impacts
Many of the following "harbingers" and "fingerprints" are now well under
way:
1. Rising Seas--- inundation of fresh water marshlands (the everglades), low-lying
cities, and islands with seawater.
2. Changes in rainfall patterns --- droughts and fires in some areas, flooding in
other areas. See the section above on the recent droughts, for example!
3. Increased likelihood of extreme events--- such as flooding, hurricanes, etc.
4. Melting of the ice caps --- loss of habitat near the poles. Polar bears are now
thought to be greatly endangered by the shortening of their feeding season due to
dwindling ice packs.
5. Melting glaciers - significant melting of old glaciers is already observed.
6. Widespread vanishing of animal populations --- following widespread
habitat loss.
7. Spread of disease --- migration of diseases such as malaria to new, now
warmer, regions.
8. Bleaching of Coral Reefs due to warming seas and acidification due to
carbonic acid formation --- One third of coral reefs now appear to have been
severely damaged by warming seas.
9. Loss of Plankton due to warming seas --- The enormous (900 mile long)
Aleution island ecosystems of orcas (killer whales), sea lions, sea otters, sea
urchins, kelp beds, and fish populations, appears to have collapsed due to loss of
plankton, leading to loss of sea lions, leading orcas to eat too many sea otters,
leading to urchin explosions, leading to loss of kelp beds and their associated fish
populations.
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6. Where do we need to reduce emissions?
In reality, we will need to work on all fronts - 10% here, 5% here, etc, and work to phase
in new technologies, such as hydrogen technology, as quickly as possible. To satisfy the
Kyoto protocol, developed countries would be required to cut back their emissions by a
total of 5.2 % between 2008 and 2012 from 1990 levels. Specifically, the US would have
to reduce its presently projected 2010 annual emissions by 400 million tons of CO2 .
One should keep in mind though, that even Kyoto would only go a little ways towards
solving the problem. In reality, much more needs to be done.
The most promising sector for near term reductions is widely thought to be coal-fired
electricity. Wind power, for example, can make substantial cuts in these emissions in the
near term, as can energy efficiency, and also the increased use of high efficiency natural
gas generation.
The potential impact of efficiency should not be underestimated: A 1991 report to
Congress by the U.S. National Academy of Sciences, Policy Implications of Greenhouse
Warming, found that the U.S. could reduce current emissions by 50 percent at zero cost
to the economy as a result of full use of cost-effective efficiency improvements.
Discussing Global Climate Change:
Here is a useful list of facts and ideas:
1. Given the strong scientific consensus, the onus should now be on
the producers of CO2 emissions to show that there is not a problem, if they still
even attempt to make that claim. Its time to acknowledge that we are, at very
least, conducting a very dangerous experiment with Earth's climate.
2. A direct look at the data itself is very convincing and hard to argue with. Ask a
skeptical person to look at the data above. The implications are obvious. The best
source of data is probably the IPCC reports themselves.
3. The recent, record-breaking warm years are unprecedented and statistically
significant. It is a fact that they are very statistically unlikely to be a fluctuation
(and now we can point to specific side effects from those warm temperatures that
appear to have induced recent worldwide drought).
4. Lastly, but perhaps most importantly, whether or not you believe in global
warming per se, the fact remains that the carbon dioxide levels are rising
dramatically --- there is no debate about this. If we continue to use fossil fuels in
the way we presently do, then the amount of carbon we will release will soon
exceed the amount of carbon in the living biosphere. This is bound to have very
serious, very negative effects, some of which, such as lowering the pH of the
ocean such that coral cannot grow, are already well known.
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7. Response of Government: Develop "Carbon Sequestration" Technology
Many government agencies around the world are very interested in maintaining fossil
fuel use, especially coal. It should be noted that US energy use, which is enormous, is
increasing, not decreasing. Furthermore, we are not going to run out of coal in the near
term (oil may begin to run low sometime after 2010). Methods for reducing carbon
emission levels while still burning coal are now investigation by government and
industry, as we now discuss.
We believe that a major increase in renewable energy use should be achieved to help
offset global warming. While there are some US government programs aimed in this
direction, there is simply not enough money being spent yet to achieve this goal in a
timely manner. A primary goal of many new programs is not to increase renewables, but
rather, is to find ways to capture the extra CO2 from electricity generation plants and
"sequester" it in the ground, the ocean, or by having plants and soil organisms absorb
more of it from the air.
Possible Problems with Carbon "Sequestration"
One of the Carbon sequestration approaches under investigation is the possibility of
depositing CO2 extracted from emission streams in large pools on the Ocean bottom. It
is possible that such pools will not be stable, and may either erupt to the surface, or
diffuse into the ocean and alter the oceans pH.
Another scheme under investigation is the idea of stimulating phytoplankton growth on
the ocean surface by dusting the surface with iron (the limiting nutrient). This will cause
an increased uptake of carbon by the plankton, part of which will find its way to the
ocean bottom. Fishing companies are considering using this to increase fish harvests
while simultaneously getting credit for carbon sequestration. Serious ecological
disruptions could occur, however, especially if this approach is conducted on a
sufficiently large scale.
Another idea is to stimulate Earth's terrestrial ecosystems to take up more carbon
dioxide. While the impacts here are more difficult to ascertain, an important point to
note is that these systems are not thought to be able to completely absorb all the extra
CO2 . At best, they may be sufficient to help the US stabilize carbon emission rates for a
few decades, but even if this is achieved, stabilization of rates are not likely to return the
Earth to pre-industrial carbon levels. Worse, biological feedbacks to global warming,
such as forest fires, drying soils, rotting permafrost, etc, may actually greatly accelerate
carbon emissions, i.e. we may experience massive carbon de-sequestration.
Another major approach under consideration is to pump CO2 into old oil and gas wells.
While seemingly attractive, it must be kept in mind that for this to be truly effective, it
would have to be done on a world wide scale, include many sources of CO2 , including
many sources which are presently small and widely distributed (such as car emissions,
and not just coal plant emissions). All of this CO2 would need to be captured,
transported, injected into old wells, and then the wells would need to be sealed and
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8. monitored. It is not clear that this would be affordable at all, and that there would be
adequate capacity or assurance that CO2 would not leak out in massive quantities.
In the worst case scenario, carbon sequestration efforts may simply fail, but also end up
being a political tool that is used to seriously delay a transition to renewable energy
sources, and also possibly create many new environmental problems problems while
prolonging old ones.
In the best case scenario, given the truly enormous amount of CO2 we are presently
emitting, some sequestration approaches may serve as a useful bridge to curbing
emissions while the transition to renewables is being made.
Introduction
One of the most vigorously debated topics on Earth is the issue of climate change, and
the National Environmental Satellite, Data, and Information Service (NESDIS) data
centers are central to answering some of the most pressing global change questions that
remain unresolved. The National Climatic Data Center contains the instrumental and
paleoclimatic records that can precisely define the nature of climatic fluctuations at time
scales of a century and longer. Among the diverse kinds of data platforms whose data
contribute to NCDC's resources are: Ships, buoys, weather stations, weather balloons,
satellites, radar and many climate proxy records such as tree rings and ice cores.
TheNational Oceanographic Data Center contains the subsurface ocean data which
reveal the ways that heat is distributed and redistributed over the planet. Knowing how
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9. these systems are changing and how they have changed in the past is crucial to
understanding how they will change in the future. And, for climate information that
extends from hundreds to thousands of years, paleoclimatology data, also available from
the National Climatic Data Center, helps to provide longer term perspectives.
Internationally, the Intergovernmental Panel on Climate Change (IPCC), under the
auspices of the United Nations (UN), World Meteorological Organization (WMO), and
the United Nations Environment Program (UNEP), is the most senior and authoritative
body providing scientific advice to global policy makers. The IPCC met in full session in
1990, 1995, 2001 and in 2007. They address issues such as the buildup of greenhouse
gases, evidence, attribution, and prediction of climate change, impacts of climate
change, and policy options.
Listed below is information based upon common questions addressed to climate
scientists (based on IPCC reports and other research) in common, understandable
language. This list will be periodically updated, as new scientific evidence comes to light.
Topics
Green House Effect Cryosphere
Green House Gases Climate Variability and Extremes
Global Temperatures Historical Context
El Niño Natural Variability
Ocean Heat Content U.S. Climate
Sea Level Rise Future Climate Projections
Hydrological Cycle Additional Resources
The Greenhouse Effect
The greenhouse effect is unquestionably real and helps to regulate the temperature of
our planet. It is essential for life on Earth and is one of Earth's natural processes. It is
the result of heat absorption by certain gases in the atmosphere (called greenhouse
gases because they effectively 'trap' heat in the lower atmosphere) and re-radiation
downward of some of that heat.Water vapor is the most abundant greenhouse gas,
followed by carbon dioxide and other trace gases. Without a natural greenhouse effect,
the temperature of the Earth would be about zero degrees F (-18°C) instead of its
present 57°F (14°C). So, the concern is not with the fact that we have a greenhouse
effect, but whether human activities are leading to an enhancement of the greenhouse
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10. effect by the emission of greenhouse gases through fossil fuel combustion and
deforestation.
Increase of Greenhouse Gases
Human activity has been increasing the concentration of greenhouse gases in the
atmosphere (mostly carbon dioxide from combustion of coal, oil, and gas; plus a few
other trace gases). There is no scientific debate on this point. Pre-industrial levels of
carbon dioxide (prior to the start of the Industrial Revolution) were about 280 parts per
million by volume (ppmv), and current levels are greater than 380 ppmv and increasing
at a rate of 1.9 ppm yr-1 since 2000. The global concentration of CO2 in our atmosphere
today far exceeds the natural range over the last 650,000 years of 180 to 300 ppmv.
According to the IPCC Special Report on Emission Scenarios (SRES), by the end of the
21st century, we could expect to see carbon dioxide concentrations of anywhere from 490
to 1260 ppm (75-350% above the pre-industrial concentration).
Global Temperatures
Global surface temperatures have increased about 0.74°C (plus or minus 0.18°C) since
the late–19thcentury, and the linear trend for the past 50 years of 0.13°C (plus or minus
0.03°C) per decade is nearly twice that for the past 100 years. The warming has not been
globally uniform. Some areas (including parts of the southeastern U.S. and parts of the
North Atlantic) have, in fact, cooled slightly over the last century. The recent warmth
has been greatest over North America and Eurasia between 40 and 70°N. Lastly, seven
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11. of the eight warmest years on record have occurred since 2001 and the 10 warmest years
have all occurred since 1995.
Recent analyses of temperature trends in the lower and mid- troposphere (between
about 2,500 and 26,000 ft.) using both satellite and radiosonde (weather balloon) data
show warming rates that are similar to those observed for surface air temperatures.
These warming rates are consistent with their uncertainties and these analyses reconcile
a discrepancy between warming rates noted on the IPCC Third Assessment Report (U.S.
Climate Change Science Plan Synthesis and Assessment Report 1.1).
An enhanced greenhouse effect is expected to cause cooling in higher parts of the
atmosphere because the increased "blanketing" effect in the lower atmosphere holds in
more heat, allowing less to reach the upper atmosphere. Cooling of the lower
stratosphere (about 49,000-79,500 ft.) since 1979 is shown by both satellite Microwave
Sounding Unit and radiosonde data (see previous figure), but is larger in the radiosonde
data likely due to uncorrected errors in the radiosonde data.
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12. Relatively cool surface and tropospheric temperatures, and a relatively warmer lower
stratosphere, were observed in 1992 and 1993, following the 1991 eruption of Mt.
Pinatubo. The warming reappeared in 1994. A dramatic global warming, at least partly
associated with the record El Niño, took place in 1998. This warming episode is reflected
from the surface to the top of the troposphere.
There has been a general, but not global, tendency toward reduced diurnal temperature
range (DTR: the difference between daily high or maximum and daily low or minimum
temperatures) over about 70% of the global land mass since the middle of the
20th century. However, for the period 1979-2005 the DTR shows no trend since the
trend in both maximum and minimum temperatures for the same period are virtually
identical; both showing a strong warming signal. A variety of factors likely contribute to
this change in DTR, particularly on a regional and local basis, including changes in
cloud cover, atmospheric water vapor, land use and urban effects.
El Niño and Global Warming
El Niños are not caused by global warming. Clear evidence exists from a variety of
sources (including archaeological studies) that El Niños have been present for
thousands, and some indicators suggest maybe millions, of years. However, it has been
hypothesized that warmer global sea surface temperatures can enhance the El Niño
phenomenon, and it is also true that El Niños have been more frequent and intense in
recent decades. Whether El Niño occurrence changes with climate change is a major
research question.
A rather abrupt change in the El Niño - Southern Oscillation behavior occurred around
1976/77. Often called the climatic shift of 1976/77, this new regime has persisted. There
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13. have been relatively more frequent and persistent El Niño episodes rather than the cool
episode La Niñas. This behavior is highly unusual in the last 130 years (the period of
instrumental record). Changes in precipitation over the tropical Pacific are related to
this change in the El Niño - Southern Oscillation, which has also affected the pattern
and magnitude of surface temperatures. However, it is unclear as to whether this
apparent change in the ENSO cycle is related to global warming.
Ocean Heat Content
The figure on the right shows the time series of seasonal (red dots) and annual average
(black line) of global upper ocean heat content for the 0-700m layer since 1955. More
information:BAMS State of the Climate in 2008. While ocean heat content varies
significantly from place to place and from year-to-year (as a result of changing ocean
currents and natural variability), there is a strong trend during the period of reliable
measurements. Increasing heat content in the ocean is also consistent with sea level rise,
which is occurring mostly as a result of thermal expansion of the ocean water as it
warms.
Rising Sea Level
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14. Global mean sea level has been rising at an average rate of 1.7 mm/year (plus or minus
0.5mm) over the past 100 years, which is significantly larger than the rate averaged over
the last several thousand years. Depending on which greenhouse gas increase scenario is
used (high or low) projected sea-level rise is projected to be anywhere from 0.18 (low
greenhouse gas increase) to 0.59 meters for the highest greenhouse gas increase
scenario. However, this increase is due mainly to thermal expansion and contributions
from melting alpine glaciers, and does not include any potential contributions from
melting ice sheets in Greenland or Antarctica. Larger increases cannot be excluded but
our current understanding of ice sheet dynamics renders uncertainties too large to be
able to assess the likelihood of large-scale melting of these ice sheets.
Hydrological Cycle (evaporation and precipitation) impacts
Globally-averaged land-based precipitation shows a statistically insignificant upward
trend with most of the increase occurring in the first half of the 20 thcentury.
Furthermore, precipitation changes have been spatially variable over the last century.
On a regional basis increases in annual precipitation have occurred in the higher
latitudes of the Northern Hemisphere and southern South America and northern
Australia. Decreases have occurred in the tropical region of Africa, and southern Asia.
Due to the difficulty in measuring precipitation, it has been important to constrain these
observations by analyzing other related variables. The measured changes in
precipitation are consistent with observed changes in stream flow, lake levels, and soil
moisture (where data are available and have been analyzed).
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15. Clouds are also an important indicator of climate change. Surface-based observations of
cloud cover suggest increases in total cloud cover over many continental regions. This
increase since 1950 is consistent with regional increases in precipitation for the same
period. However, global analyses of cloud cover over land for the 1976-2003 period
show little change.
The Cryosphere
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16. Indirect indicators of warming such as borehole temperatures, snow cover, and glacier
recession data, are in substantial agreement with the more direct indicators of recent
warmth. Evidence such as changes in glacial mass balance (the amount of snow and ice
contained in a glacier) is useful since it not only provides qualitative support for existing
meteorological data, but glaciers often exist in places too remote to support
meteorological stations. The records of glacial advance and retreat often extend back
further than weather station records, and glaciers are usually at much higher altitudes
than weather stations, allowing scientists more insight into temperature changes higher
in the atmosphere. Glaciers have been retreating worldwide for at least the last century;
the rate of retreat has increased in the past decade. Only a few glaciers are actually
advancing (in locations that were well below freezing, and where increased precipitation
has outpaced melting). The progressive disappearance of glaciers has implications not
only for a rising global sea level, but also for water supplies in certain regions of Asia
and South America.
Large-scale measurements of sea-ice have only been possible since the satellite era, but
through looking at a number of different satellite estimates, it has been determined that
September Arctic sea ice has decreased between 1973 and 2007 at a rate of about -10%
+/- 0.3% per decade. Sea ice extent for September 2007 was by far the lowest on record
at 4.28 million square kilometers, eclipsing the previous record low sea ice extent by
23%. Sea ice in the Antarctic has shown very little trend over the same period, or even a
slight increase since 1979. Though extending the Antarctic sea-ice record back in time is
more difficult due to the lack of direct observations in this part of the world.
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17. The chart to the left shows the average of monthly snow cover extent anomalies over
Northern Hemisphere lands (including Greenland) since Nov 1966. Image
from BAMSState of the Climate in 2008 report. Northern Hemisphere snow cover
extent has consistently remained below average since 1987, and has decreased by about
10% since 1966. This is mostly due to a decrease in spring and summer snow extent over
both the Eurasian and North American continents since the mid-1980s. Winter and
autumn snow cover extent have shown no significant trend for the northern hemisphere
over the same period. This pattern is consistent with warmer global temperatures.
Climate Variability and Extremes
Examination of changes in climate extremes requires long-term daily or even hourly
data sets which until recently have been scarce for many parts of the globe. However
these data sets have become more widely available allowing research into changes in
temperature and precipitation extremes on global and regional scales. Global changes in
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18. temperature extremes include decreases in the number of unusually cold days and
nights and increases in the number of unusually warm days and nights. Other observed
changes include lengthening of the growing season, and decreases in the number of frost
days.
Global temperature extremes have been found to exhibit no significant trend in
interannual variability, but several studies suggest a significant decrease in intra-annual
variability. There has been a clear trend to fewer extremely low minimum temperatures
in several widely-separated areas in recent decades. Widespread significant changes in
extreme high temperature events have not been observed. There is some indication of a
decrease in day-to-day temperature variability in recent decades.
In areas where a drought or excessive wetness usually accompanies an El Niño or La
Niña, these dry or wet spells have been more intense in recent years. Further, there is
some evidence for increasing drought worldwide, however in the U.S. there is no
evidence for increasing drought. In some areas where overall precipitation has increased
(ie. the mid-high northern latitudes), there is evidence of increases in the heavy and
extreme precipitation events. Even in areas such as eastern Asia, it has been found that
extreme precipitation events have increased despite total precipitation remaining
constant or even decreasing somewhat. This is related to a decrease in the frequency of
precipitation in this region.
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19. Many individual studies of various regions show that extra-tropical cyclone activity
seems to have generally increased over the last half of the 20th century in the northern
hemisphere, but decreased in the southern hemisphere. Furthermore, hurricane activity
in the Atlantic has shown an increase in number since 1970 with a peak in 2005. It is not
clear whether these trends are multi-decadal fluctuations or part of a longer-term trend.
Conditions in Historical Context
Paleoclimatic data are critical for enabling us to extend our knowledge of climatic
variability beyond what is measured by modern instruments. Many natural phenomena
are climate dependent (such as the growth rate of a tree for example), and as such,
provide natural 'archives' of climate information. Some useful paleoclimate data can be
found in sources as diverse as tree rings, ice cores, corals, lake sediments (including
fossil insects and pollen data), speleothems (stalactites etc), and ocean sediments. Some
of these, including ice cores and tree rings provide us also with a chronology due to the
nature of how they are formed, and so high resolution climate reconstruction is possible
in these cases. However, there is not a comprehensive 'network' of paleoclimate data as
there is with instrumental coverage, so global climate reconstructions are often difficult
to obtain. Nevertheless, combining different types of paleoclimate records enables us to
gain a near-global picture of climate changes in the distant past.
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20. For Northern Hemisphere temperature, recent decades appear to be the warmest since
at least about 1000AD, and the warming since the late 19th century is unprecedented
over the last 1000 years. Older data are insufficient to provide reliable hemispheric
temperature estimates. Ice core data suggest that the 20th century has been warm in
many parts of the globe, but also that the significance of the warming varies
geographically, when viewed in the context of climate variations of the last millennium.
Large and rapid climatic changes affecting the atmospheric and oceanic circulation and
temperature, and the hydrological cycle, occurred during the last ice age and during the
transition towards the present Holocene period (which began about 10,000 years ago).
Based on the incomplete evidence available, the projected change of 3 to 7°F (1.5 - 4°C)
over the next century would be unprecedented in comparison with the best available
records from the last several thousand years.
Natural Variability
Since our entire climate system is fundamentally driven by energy from the sun, it
stands to reason that if the sun's energy output were to change, then so would the
climate. Since the advent of space-borne measurements in the late 1970s, solar output
has indeed been shown to vary. With now 28 years of reliable satellite observations
there is confirmation of earlier suggestions of an 11 (and 22) year cycle of irradiance
related to sunspots but no longer term trend in these data. Based on paleoclimatic
(proxy) reconstructions of solar irradiance there is suggestion of a trend of about +0.12
W/m2 since 1750 which is about half of the estimate given in the last IPCC report in
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21. 2001. There is though, a great deal of uncertainty in estimates of solar irradiance beyond
what can be measured by satellites, and still the contribution of direct solar irradiance
forcing is small compared to the greenhouse gas component. However, our
understanding of the indirect effects of changes in solar output and feedbacks in the
climate system is minimal. There is much need to refine our understanding of key
natural forcing mechanisms of the climate, including solar irradiance changes, in order
to reduce uncertainty in our projections of future climate change.
In addition to changes in energy from the sun itself, the Earth's position and orientation
relative to the sun (our orbit) also varies slightly, thereby bringing us closer and further
away from the sun in predictable cycles (called Milankovitch cycles). Variations in these
cycles are believed to be the cause of Earth's ice-ages (glacials). Particularly important
for the development of glacials is the radiation receipt at high northern latitudes.
Diminishing radiation at these latitudes during the summer months would have enabled
winter snow and ice cover to persist throughout the year, eventually leading to a
permanent snow- or icepack. While Milankovitch cycles have tremendous value as a
theory to explain ice-ages and long-term changes in the climate, they are unlikely to
have very much impact on the decade-century timescale. Over several centuries, it may
be possible to observe the effect of these orbital parameters, however for the prediction
of climate change in the 21st century, these changes will be far less important than
radiative forcing from greenhouse gases.
21

22. United States Climate
The image to the right shows the annual surface temperatures for the contiguous U.S.
compared to the 20th Century (1901-2000) average. Calculated from the U.S. Historical
Climatology Network (USHCN version 2). More information:U.S. Surface Temperature
Data, USHCN v2. Surface temperatures averaged across the U.S. have also risen. While
the U.S. temperature makes up only part of the global temperature, the rise over a large
area is not inconsistent with expectations in a warming planet. Because the U.S. is just a
fraction of the planet, it is subject to more year-to-year variability than the planet as a
whole. This is evident in the U.S. temperature trace.
Annual Climate Extremes Index (CEI) value for the contiguous United States. Larger
numbers indicate more acive climate extremes for a year. More information: CEI. One
way climate changes can be assessed is by measuring the frequency of events considered
extreme (among the most rare of temperature, precipitation and storm intensity values).
The Climate Extremes Index (CEI) value for the contiguous United States is an objective
way to determine whether extreme events are on the rise.
22

23. The figure to the left shows the the number of extreme climate events (those which place
among the most unusual of the historical record) has been rising over the last four
decades.
Future Climate Projections
Due to the enormous complexity of the atmosphere, the most useful tools for gauging
future changes are 'climate models'. These are computer-based mathematical models
which simulate, in three dimensions, the climate's behavior, its components and their
interactions. Climate models are constantly improving based on both our understanding
and the increase in computer power, though by definition, a computer model is a
simplification and simulation of reality, meaning that it is an approximation of the
climate system. The first step in any modeled projection of climate change is to first
simulate the present climate and compare it to observations. If the model is considered
to do a good job at representing modern climate, then certain parameters can be
changed, such as the concentration of greenhouse gases, which helps us understand how
the climate would change in response. Projections of future climate change therefore
depend on how well the computer climate model simulates the climate and on our
understanding of how forcing functions will change in the future.
The IPCC Special Report on Emission Scenarios determines the range of future possible
greenhouse gas concentrations (and other forcings) based on considerations such as
population growth, economic growth, energy efficiency and a host of other factors. This
leads a wide range of possible forcing scenarios, and consequently a wide range of
possible future climates.
According to the range of possible forcing scenarios, and taking into account uncertainty
in climate model performance, the IPCC projects a best estimate of global temperature
increase of 1.8 - 4.0°C with a possible range of 1.1 - 6.4°C by 2100, depending on which
emissions scenario is used. However, this global average will integrate widely varying
regional responses, such as the likelihood that land areas will warm much faster than
ocean temperatures, particularly those land areas in northern high latitudes (and mostly
in the cold season). Additionally, it is very likely that heat waves and other hot extremes
will increase.
23

24. Precipitation is also expected to increase over the 21st century, particularly at northern
mid-high latitudes, though the trends may be more variable in the tropics, with much of
the increase coming in more frequent heavy rainfall events. However, over mid-
continental areas summer-drying is expected due to increased evaporation with
increased temperatures, resulting in an increased tendency for drought in those regions.
Snow extent and sea-ice are also projected to decrease further in the northern
hemisphere, and glaciers and ice-caps are expected to continue to retreat.
24

25. Global warming and construction industry / real estate
Global Warming Threat: Construction industry in Australia is wasteful and needs to
change radically.
Despite efforts to be more efficient, Australia’s emissions of carbon dioxide have risen at
almost twice the world average rate over the last 20 years - to more than 100 million
tons a year. That’s 5 tons for every person. With only 0.32% of world population,
Australia produces 1.43% of global emissions.
While huge savings can be made by generating electricity from carbon more efficiently,
or by using alternative power sources, there is also urgent need to cut energy use – and
to reduce peak demand.
A key target for energy saving has to be the construction industry. 40% of Australia’s
energy is used to heat, light or cool buildings, build them or knock them down. Most
buildings in Australia were designed for a different era where electricity, coal, oil and
water were cheap, and the greatest challenge is going to be refitting them for the third
millennium.
Many of the most inefficient buildings are offices and factories. The lazy option is to pull
them down and start again but this is really costly for the environment. If a building
only survives 30 years before demolition, up to 40% of all the energy used in its lifetime
will be spent building it, destroying it and carrying away the rubble.
That’s why we can expect huge efforts to retrofit older buildings - but we need to take
great care to get it right, or more refits will be needed every decade as regulations and
needs change. Compliance with today’s standards is a fast way to waste billions of
dollars. You’ll have to upgrade again tomorrow, and the week after.
That’s why we need bold, radical, long term vision. We need to get ready for a future
where energy is twice as expensive as today when carbon taxes are added. A world where
energy saving has become a global obsession.
Retrofitting old commercial buildings can be an expensive nightmare – particularly as
many of them are near the end of their original design life. It is a wasteful scandal that
most office blocks built in the last 30 years were only intended to be lived in for three
decades.
We need a radical change in mindset of architects, planners, developers, builders and
property investors. New commercial buildings should be designed with at least 50 years
in mind. That will require government action: big changes in building regulations and
far stricter planning standards. Without these things there will always be a temptation
25

26. to cut building costs and go for the short term.
You cannot imagine such short-sightedness when building private homes. Who wants to
buy a new family house that is almost guaranteed to auto-destruct by 2040? Developers
who try to build such trash for the domestic market will land up in prison – but in the
commercial sector they are regarded as heroes: fast build, low cost and who cares about
the future.
We have a moral duty to build for the longer term. Not just to save carbon emissions.
There are huge numbers of other environmental benefits in terms of reduced demand
for steel, copper, wood, reduced landfill and many manufactured items that can be
conserved.
This is not just about more efficient air conditioning, better insulation, saving water or
making buildings more intelligent. Such steps are only a small part of the answer.
Expect nothing less than a total rethink about the kind of world we want future people
to live in.
We are literally building the future: of communities, neighbourhoods, working places,
leisure and home environments, places of learning and of healing. Great buildings pass
on a legacy for many generations, and should last hundreds of years.
Building long term means it really matters what the construction looks like. Tomorrow’s
world will expect many more landmarks of quality, which endure not only in their
materials, but in the affections of those who use them. The Sydney Opera House is a
wonderful example of design, harmony in location, and emotional attachment. We don’t
build Opera Houses to knock them down a couple of decades later – so why do we
tolerate such short-termism and poor quality elsewhere?
The technologies we need are already available for next generation buildings. Take
geothermal heating and cooling. These systems use up to 50% less energy than
alternative systems. 45% of new homes in New Zealand have them, 70% in Sweden and
30% in Switzerland. They work like refrigerator pumps, heating or cooling pipes laid a
metre below ground. Systems pay for themselves in 15 years. The global market for
geothermal installations could be more than US $40bn a year.
The gold standard will be zero emission buildings: where on-site power generation from
solar, wind or other sources is more than enough to meet all heat, light and cooling
needs. We are already seeing demands in Europe by governments that builders create
carbon-neutral homes. It’s just the beginning. We can expect zero-emission new
buildings to be forced on the industry in many parts of the world over the next decade.
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27. And as that happens, the gap will grow even wider between new and old building
efficiencies.
Government regulations and subsidies can set up national industries to seize these new
markets. Look what’s happened in Germany where government action has resulted in
the country buying 70% of all solar cells made in the world every month – and German
solar cell manufacturers are dominating globally.
So we can expect aggressive and radical changes in the way buildings run. But we can
also expect a major rethink about how much energy is used in actually building them in
the first place.
A key target for attack will be the concrete industry which is responsible for 5-7% of all
global carbon emissions. Concrete is a bulky, low value, two-thousand-year-old
commodity which uses massive amounts of energy in a wasteful way. We urgently need
an alternative – and there is one.
Expect widespread use in future of geoplymers such as E-crete, a product using power
station waste, developed by Jannie Van Deventer, a chemical engineer at the University
of Melbourne, and founder of Zeobond. If we replaced half the world’s concrete
production with e-crete it would save a billion tons of carbon dioxide in the next decade
alone.
E-crete is just one of thousands of examples of new innovation we can expect over the
next five to ten years.... representing tens of thousands of new business opportunities,
and billions of dollars of new revenues.
But the transformations we need will only happen as the construction industry pulls in a
younger generation of highly talented, innovative and creative business leaders,
designers, architects, engineers, surveyors and developers. It is often hard for these
sectors to compete with more glamorous and well paid careers in industries such as
banking, marketing, computing or telecommunications. So how will it happen?
The best talent will only be drawn into the construction industry when a younger
generation see huge, exciting opportunities for new highly-profitable business
innovation and creative action, and a chance quite literally to help build a better future,
driven not just by commercial pressures but also a mission to help save the world.
27

28. The Role of Building Construction Materials on Global Warming
Lessons for Architects
Abstract
The world today has encountered with global warming and climate change. Besides
other contributors, extraction of natural resources as building materials itself consume
energy, cause environmental degradation and contribute to global warming. Buildings
are the largest energy consumers and greenhouse gases emitters, both in the developed
and developing countries. Urgent changes are therefore required relating to energy
saving, emissions control, production and application of materials. Immediate
suggestion related to use of renewable resources, and to recycling and reuse of building
materials is necessary. This paper describes how much a typical building is contributing
to global warming by releasing the carbon dioxide emission. And how the architects and
building designers can decrease the amount of carbon footprint emitted from the
building materials. As a case study a 3-story
building made of commonly used materials; concrete, brick, stone and glass has been
selected. Total quantity of carbon emission is estimated and finally suggestions are given
to reduce carbon dioxide emission.
Keywords: Global warming, Green House Gases, Carbon footprint, Construction and
Building materials.
Introduction
The United Nation’s Inter-governmental Panel on Climate Change states that the Global
Warming was caused by greenhouse gases due to human activities. The composition of
green house gases is 76% carbon dioxide CO2, 13% methane, 6% nitrogen oxide and 5%
fluorocarbons. Therefore, CO2 is a significant contributor for increasing the global
temperature. Researches show that there are eight major sectors which are annually
releasing considerable amount of Green House Gases thereby CO2 into the air, causing
global warming. They are viz. power station (21.3%), industrial processing (16.8%),
transportation fuels (14.0%), agricultural by-products (12.5%), fossil fuel retrieval
processing & distribution (11.3%), commercial & other sectors (10.3%), land use &
biomass burning (10.0%) and waste disposal & treatment (3.4%). In this paper, we are
discussing the emission of CO2 from building industry which shares around 80% of
emissions from industrial processing. Every year millions of new buildings are being
constructed and on the name of modernity new construction materials are being
introduced. One of the biggest blunders of the modernity was to throw most of the
traditional knowledge away. In architecture, with the advent of new materials,
the older materials were abandoned. But, many of these traditional materials and
techniques are a work of many generations, perfecting the techniques with experiments,
so that the technologies that have evolved have withstood the test of time. Hence, it
would be stupidity to disregard this rich heritage that we have inherited. Instead, now it
is time to access all the materials, be it new or old, and give all the materials a proper
place in the building. For example, in places where there is a shortage of space,
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29. one goes for burnt bricks. But, where there is no shortage of space, it seems sensible to
go for traditional walls because; though thicker they would allow retention of heat
within the house, an important aspect for comfortable living in colder climates.
However, invariably new materials are being introduced due to pressure of perceived
necessity. These new materials need much of processing before they come into use.
Significant embodied energy consumed in the production of energy intensive building
materials
and also the recurring energy consumption for cooling and heating of indoor
evironment.
Co2 emission is a result of human activities such as raw material extraction;
manufacture and distribution, therefore, Co2 emission can be used as one of the relative
measures of the environmental friendliness of a building product and help determine its
sustainability and desirability in construction. To demonstrate the same, we selected a
typical building and estimated its CO2 emission. For the purpose of this study, concrete
building in humid climatic environment is selected. All the materials used in this
building are evaluated. Embodied energy of each material is calculated in its lifecycle.
Finally, the CO2 emission has been estimated to find the degree of sustainability of the
building and its effect on global warming.
Building & Building Materials
Three story reinforced concrete residential building built in 1999 is selected for the
study. The total building area is 95m2. Structure is made of RC frames withbrick
masonry infill. External surfaces arecovered with gypsum plaster. Wood work isused for
wardrobes inside three bedroomsand kitchen. Aluminum is used as the frameof
windows and the bathroom doors. Table1shows the quantities of each material used
inbuilding. From the table it can be understood
Elevation that wide variety of processed materials are put in use.
Embodied Energy
Table 2 describes the embodied energy of different materials used in construction. It can
be clearly seen that the highest embodied energy is related to Stone which is around
7800 GJ. Steel, gypsum plaster and concrete are between 400 to 500 GJ. The embodied
energy of brick is around 170 GJ while ceramic tile and aluminum have around 100 GJ
only. The energy needed for manufacturing and transporting the mosaic and wood for
the case study is between 20 and 40 Giga Joule. The lowest embodied energy in this
building is of painting, cement mortar and glass which are lower than 10 GJ. The
embodied energy in a product comprises the energy to extract, transport and refine the
raw materials and then to manufacture components and assemble the product. The
energy consumed directly at each phase is clearly definable and measurable. However,
the energy required indirectly to support the main processes is less obvious and more
difficult to measure. This includes the energy embodied in other outputs of goods and
services and the machinery used to support these processes. The total embodied energy
comprises the direct energy purchased to support the process under consideration plus
the indirect energy embodied in inputs to the process. In the initial stage of construction
of buildings, the direct energy is the energy purchased by contractors on-site or off-site
to facilitate any construction, pre-fabrication, administration and transport activities
under their control.
29

30. The indirect energy of construction comprises mainly the
energy embodied in building materials. Together, these amounts of energy constitute
the initial embodied energy of the building. However, during a building’s life, embodied
energy is added through goods and services used in maintenance and refurbishment.
This are typically modeled by assuming replacement rates for items in the buildings (for
example, paint) and is known as the recurrent embodied energy.
Embodied Energy Analysis Method
In order to understand the total Co2 emission from a building, it is necessary to access
the emission from each material independently. Initially all the quantities of the
building are Table 2. Embodied Energy of Materials of Case Study evaluated using
centre line method. And later volume of Co2 emission from each material is estimated
by using the formula given below:
Amount of Co2 emission (Kg)=VxDxC
Where, V= Volume of Building Material Used (m3)
D=Density of Building Materials (Kg/m3)
C= Embodied Carbon Emission (Kg Co2 /Kg)
Table 3 describes the amount of carbon dioxide emitted by various materials used in the
building. It can be seen that the highest amount of carbon dioxide is releasing from
Steel, Aluminum, Stone, Glass and Concrete. The Co2 emission of Brick and Timber
wood almost are same. Between all of the used materials just ceramic tile and cement
mortar have the minimum level of carbon dioxide emission. Having a look at the total
Co2 released gas, it will be perceived that a considerable amount of carbon dioxide is
emitting from this building during its construction period, 442175 ton which is a
noticeable amount.
Impact on Global Warming: Concern
Technology development paves way to all-round growth. Although this fact is
undisputable, e.g., invention of motor vehicle, plastic carry bags were treated as a
triumph and technology marvel; looking it at a different angle, an aspect of maintaining
technology to the contemporary needs and its sustainability is often ignored. The
menace which these technologies are creating in terms of carbon emissions is in leaps
and bounds. India predominantly lives in rural areas. It is pointed out that in the decade
1990, 70% use to live in rural areas and gradually percentage of urban housing is
increasing in the decade of 2000 (Ref 14). The materials used for house roofing during
1990's clearly shows that the usage of natural materials is very high and on the contrary
the percentage of cement usage is around 12% only. However, as in one decade i.e,
during 2000's usage of cement has nearly doubled. This trend is seen both in rural as
well as urban areas. This has direct impact on percentage emission of Co2. Table 3. CO2
Emission of Materials of Case Study There is significant increase of natural disasters in
recent times compared to older times.
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31. Main contributor for it to happen is increased global temperatures; resulting in uneven
seasonal changes. Therefore, finding proper replacements for the materials which have a
big proportion in contributing Carbon Dioxide is necessary to reduce the amount of Co2
emission in order to prevent the increase in global temperature.
Discussion & Suggestion
Table 4 describes some alternative materials in place of commonly used material. As
large amount of carbon dioxide is coming out of steel and aluminum, they can be
replaced by other materials with low carbon footprint. It can be seen that Co2 emission
can be reduced upto 35%. And by using cullet glass 50 % of Co2 emission can be
reduced. Therefore, the best option for cutting down the carbon dioxide emission in the
building construction is; 1. Use recyclable materials as much as possible, 2. Use locally
available materials for decreasing the fuel used for transporting of materials in order to
reduce Co2 gas emission, 3. Using vernacular architecture, 4. Using eco-friendly
building materials and 5. Designing the buildings with respect to the nature for having
better ventilation and using natural day light.
Conclusions
Embodied energy and Co2 emission in a reinforced concrete building as a case study has
been discussed in this paper. The paper only focuses on the building materials used in
construction and not on the functions of the building. Initially volume of each building
material is estimated and later carbon dioxide emission due to each material is
evaluated. It is observed that stone, steel, concrete and Gypsum plaster are the highest
energy consumer materials among the all materials used for construction. Finally
suggestions are given to reduce the carbon foot print from a typical building.
END
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