Download General Information on Global Warming

General Information on Global Warming
What is the Greenhouse Effect?
How is it related to Greenhouse Warming and Global Warming?
The Greenhouse Effect is a term that describes how water vapor, carbon dioxide, and other gases
in the atmosphere help maintain the temperature at the Earth's surface? The atmosphere
approximates the function of a greenhouse by first letting sunlight (solar or short wave radiation)
pass through to warm the Earth, while absorbing much of the heat (thermal or long wave
radiation) radiated up from the surface of the Earth.
Life on Earth would be very different without the Greenhouse Effect. The Greenhouse Effect
serves to keep the long term annual average temperature of the Earth approximately 32°C higher
than the Earth's temperature would be without the Greenhouse Effect. It is reasonable to expect
that the Earth should warm as concentrations of greenhouse gases in the atmosphere increase
above natural levels, much like what happens when the windows of a greenhouse are closed on a
warm, sunny day. This additional warming is commonly referred to as Greenhouse Warming.
Greenhouse Warming is global warming due to increases in atmospheric greenhouse gases (e.g.,
carbon dioxide, methane, chlorofluorocarbons, etc.), whereas Global Warming refers only to the
observation that the Earth is warming, without any indication of what might be causing the
warming.
Global Warming is accepted as fact by most of the scientific community. However, Greenhouse
Warming is more controversial because it implies that we know what is causing the Earth to
warm. Although it is known for certain that atmospheric concentrations of these greenhouse gases
are rising dramatically due to human activity, it is less well known exactly how increases in these
greenhouse gases factor in the observed changes of the Earth's climate and global temperatures.
The glass walls and roof of a greenhouse allow most of the sun's light in, but do not allow most of
the heat to escape. This causes the temperature inside the greenhouse to be warmer than outside.
The earth's atmosphere, and in particular carbon dioxide (CO2) and water vapor (H2O), acts like a
greenhouse, trapping heat and making the earth warmer. This is one of the earth's natural
processes, without which the earth would be an icy 32°C colder! However, human activity is
adding more CO2 to the atmosphere, possibly enhancing the greenhouse effect and potentially
resulting in global warming.
The burning of fossil fuels, like oil, coal and natural gases, are sources of energy that release CO 2
into the atmosphere. CO2 is one of the primary greenhouse gases in the atmosphere which actually
traps outgoing heat and warms the earth. Scientists can measure the amount of CO2 in the earth's
atmosphere and have discovered that amounts of the gas are increasing. With this increase in
mind, there is the possibility that more CO2 will lead to an enhancement of the greenhouse effect.
The graph clearly shows that CO2 has increased in the atmosphere over time. The graph also has a
sawtooth shape, rising and falling slightly each year.
Why the rise and fall of carbon dioxide each year?
Plants absorb CO2 during photosynthesis, and there are more plants in the northern hemisphere
than in the southern, simply because there is more land north of the equator. Each year in northern
summers, plants absorb more CO2 than people produce. When the growing season ends in the
northern hemisphere, the CO2 content of the atmosphere resumes its growth then from fossil fuel
burning.
Atmospheric CO2 concentrations in parts per million, Mauna Loa, Hawaii. Source: C.D. Keeling
& T.P. Whorf, Scripps Institute of Oceanography. Data available from the Carbon Dioxide
Information Analysis Center (CDIAC).
What is "Global Warming?"
The term Global Warming refers to the observation that the atmosphere near the Earth's surface is
warming, without any implications for the cause or magnitude. This warming is one of many
kinds of climate change that the Earth has gone through in the past and will continue to go
through in the future.
Temperature increases will have significant impacts on human activities: where we can live, what
food we can grow and how or where we can grow food, and where organisms we consider pests
can thrive. To be prepared for the effects of these potential impacts we need to know how much
the Earth is warming, for how long the Earth has been warming, and the cause of the warming.
Answers to these questions provide us with a better basis for making decisions related to issues
such as water resource management and agricultural planning.
How do we study "Global Warming?"
There are several ways that scientists study how the Earth's temperature is changing. Although
each method has some uncertainties, they all suggest a similar story - that the Earth has warmed
dramatically over the last 140 years and that the Earth is now warmer than it has been in the last
600 years.
Some scientists look to satellites to reveal something about the Earth's changing climate. Although
the satellite record is very short (ca. 20 years) and hard to interpret due to changes in instruments
and orbits, the latest satellite studies confirm the same story - the globe is warming.
The record of instrumental temperature measurements, extending back to the 19th century,
provides one clear indication: that the mean annual surface air temperatures of the earth have risen
approximately 0.5oC since 1860.
Paleoclimatic data provides an independent confirmation of this recent warming, and also places
the 19th to 20th century (1860 to present day) warming in the context of the last several centuries
to millennia. The paleoclimatic record not only allows us to look at global temperature fluctuations
over the last several centuries, it also permits scientists to examine past climate even further back
in time. This perspective is an important capability in our quest to understand the possible causes
of the 20th century global warming. We can look at hypothesized warm periods in the distant past
(e.g., 1,000; 6,000; 125,000; and even 165,000,000 years ago) to see if they provide clues for
natural processes that could be causing the global warming we are now experiencing. So far,
paleoclimatologists have been unable to find any natural climatic explanations for our present-day
warming.
Other Scientific Views
One of the problems in understanding global warming is that scientists have different theories as to
what is causing it. Some scientists think that the amount of greenhouse gases in the air is so small
that all of the temperature change we have recently seen is just the result of natural cycles of
climate change.
It seems like the nothing could be more predictable than the seasons, but in fact, the seasons have
changed. Thousands of years ago, the earth was much colder than what it is now. Glaciers came as
far down as middle America. This was when the wooly mammoth used to roam the earth. Then,
the earth got warmer. We know this because of the science of Paleoclimatology. Paleoclimatology
is really useful in the debate around global warming because it allows us to look back in time and
investigate previous climate shifts. This way we can look the global warming that took us out of
the ice age and then compare it to what is happening now. Many scientists look at the history of
climate change and believe that the same thing is happening now, and that mankind's effects on the
climate are negligible.
These two charts show that the percentage of greenhouse gas in the
atmosphere is exceptionally small. It is so small that some scientists doubt if
it could have the warming effects that we have noticed.
Is the earth getting warmer because we are dumping tons of greenhouse gases into the air? Are we
just starting a natural climate change that may or may not end soon? Is it both? What about neither?
Make sure that you are aware that everything about global warming is a puzzle.