Download Global Warming - Department of Geology UPRM

Calentamiento Global
“Mito o realidad”
Hernán Santos
Departamento de Geologia
UPR-Mayagüez
G eM
Geology Museum
¿Que es el Calentamiento Global?
• Calentamiento Global
se refiere al aumento
de la temperatura
promedio en los
océanos y en la
superficie de nuestro
planeta durante las
pasadas décadas.
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(0 en esta grafica representa la temperatura promedio entre
1961 y 1990, IPCC, Global Warming Art)
• La temperatura del aire en la superficie
aumento 1.3+/-0.32 ºF en el ultimo siglo.
• ONU-ICPP (Intergovernmental Panel on
Climate Change) concluyo que este
aumento se debe al aumento de gases de
invernadero en nuestra atmósfera como
resultado de actividades antropogénicas.
¿Que son los gases de
invernadero?
• Los gases de invernadero son componentes de
nuestra atmósfera que contribuyen al efecto de
casa de invernadero.
• Algunos ocurren de forma natural en nuestra
atmósfera mientras que otros son el resultado de
actividades humanas como la quema de
combustibles fósiles (carbón, petróleo y gas
natural).
• Los gases de invernadero son: vapor de agua,
bióxido de carbono, metano, oxido nitroso y ozono.
¿Qué es el efecto de Casa de Invernadero?
• Cuando los rayos del sol llegan a la superficie de la tierra algunos
son reflejados al espacio y otros son absorbidos por los gases de
invernadero calentando la misma.
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Este proceso es importante ya que mantiene la temperatura de
nuestro planeta. Sin el efecto de casa de invernadero,la temperatura
de nuestra planeta seria cerca de 20º C por debajo de la temperatura
actual.
(-6.6 º F)
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Gases de invernadero
naturales
• Vapor de agua (sin nubes) causa 36-70% del
Efecto de Casa de Invernadero (ECI)
• Bioxido de carbono 9-26% ECI
• Metano 4-9% ECI
• Ozono 3-7% ECI
• Oxigeno (O2) y nitrogeno (N2), los gases mas
abundantes en la atmosfera no producen ECI.
Gases de invernadero
originados por el ser humano
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• La concentracion de Gases
de invernadero ha
amunetado mayormente
por la liberacion de CO2.
Principalmente por la
quema de combustible
fosil y deforestacion
• Metano ha aumentado por
la ganaderia y sembradios
de arros. Tambien por los
vertederos.
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www.grida.no/ climate/vital/19.htm
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This map depicts the unequal distribution of industry in the world. The significant part of
carbon dioxide emissions comes from energy production, industrial processes and
transport. The industrialised countries consequently must bear the main responsibility of
reducing emissions of carbon dioxide.
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Emissions of carbon dioxide due to changes in land use mainly come from the cutting
down of forests and instead using the land for agriculture or built-up areas,
urbanisation, roads etc. When large areas of rain forests are cut down, the land often
turns into less productive grasslands with considerably less capacity of storing CO2.
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Volume of GHG calculated per nation and per capita. The rich countries of the world historically has emitted
most of the anthropogenic greenhouse gases since the start of the industrial revolution in the latter half of
the 1700s. Per capita, the significant emissions still are produced by the OECD countries.- A major issue of
debate is the sharing of responsibility. Non-industrialised countries strive to increase their population's
standard of living, thereby also increasing their emissions of greenhouse gases, since economic
development is closely associated with energy production. The volume of GHG thus will probably increase
despite the efforts to reduce emissions in industrialised countries. China has the second biggest emissions
of GHG in the world. However, per capita the Chinese emissions are very low compared to the no. 1 on the
list, the USA.
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The global carbon cycle shows the carbon reservoirs in
GtC (gigatonne= one thousand million tonnes) and fluxes
in GtC/year. The indicated figures are annual averages
over the period 1980 to 1989. The component cycles are
simplified and the figures present average values. The
riverine flux, particularly the anthropogenic portion, is
currently very poorly quantified and is not shown here.
Evidence is accumulating that many of the fluxes can
fluctuate significantly from year to year. In contrast to the
static view conveyed in figures like this one, the carbon
system is dynamic and coupled to the climate system on
seasonal, interannual and decadal timescales.
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The amount of aerosols in the air has direct effect on the amount of solar radiation hitting the Earth's surface.
Aerosols may have significant local or regional impact on temperature. Water vapour is a greenhouse gas,
but at the same time the upper white surface of clouds reflects solar radiation back into space. Albedo reflections of solar radiation from surfaces on the Earth - creates difficulties in exact calculations. If e.g. the
polar icecap melts, the albedo will be significantly reduced. Open water absorbs heat, while white ice and
snow reflect it.
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The figure shows the combined land-surface air and sea surface temperatures (degrees Centigrade) 1861 to
1998, relative to the average temperature between 1961 and 1990.The mean global surface temperature has
increased by about 0.3 to 0.6°C since the late 19th century and by about 0.2 to 0.3°C over the last 40 years,
which is the period with most reliable data. Recent years have been among the warmest since 1860 - the
period for which instrumental records are available.Warming is evident in both sea surface and land-based
surface air temperatures. Urbanization in general and desertification could have contributed only a small
fraction of the overall global warming, although urbanization may have been an important influence in some
regions. Indirect indicators such as borehole temperatures and glacier shrinkage provide independent support
for the observed warming. It should also be noted that the warming has not been globally uniform. The recent
warming has been greatest between 40°N and 70°N latitude, though some areas such as the North Atlantic
Ocean have cooled in the recent decades.
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Precipitation has increased over land at high latitudes of the Northern Hemisphere, especially during the
cold season. Decrease in precipitation occurred in steps after the 1960s over the subtropics and the tropics
from Africa to Indonesia. These changes are consistent with available data analyses of changes in stream
flow, lake levels and soil surface. Precipitation averaged over the Earth's land surface increased from the
start of the century up to about 1960, but has decreased since about 1980. There is a lack of data on
precipitation over the oceans. (Source:WG I SAR, TS p.28)
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Using the IS92 emission scenarios, projected global mean temperature changes relative to
1990 were calculated up to 2100. Climate models calculate that the global mean surface
temperature could rise by about 1 to 4.5 centigrade by 2100. The topmost curve is for
IS92e, assuming constant aerosol concentrations beyond 1990 and high climate sensitivity
of 4.5 °C. The lowest curve is for IS92c and assumes constant aerosol concentrations
beyond 1990 and a low climate sensitivity of 1.5 °C. The two middle curves show the
results for IS92a with "best estimate" of climate sensitivity of 2.5 °C: the upper curve
assumes a constant aerosol concentration beyond 1990, and the lower one includes
changes in aerosol concentration beyond 1990. (It is assumed that the Greenhouse effect
is reduced with increased aerosols.)Note: In IPCC reports, climate sensitivity usually refers
to the long- term or equilibrium, change in global mean surface temperature following a
doubling of CO2-equivalent atmospheric concentrations. More generally, it refers to the
equilibrium change in surface air temperature following a unit change in radiative forcing
(°C/Wm-2)
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Using the IS92 emission scenarios, projected global
mean sea level increases relative to 1990 were
calculated up to 2100. Taking into account the ranges
in the estimate of climate sensitivity and ice melt
parameters, and the full set of IS92 emission
scenarios, the models project an increase in global
mean sea level of between 13 and 94 cm.During the
fist half of the next century, the choice of emission
scenario has relatively little effect on the projected
sea level rise due to the large thermal inertia of the
ocean-ice-atmosphere climate system, but has
increasingly larger effects in the later part of the next
century. In addition, because of the thermal inertia of
the oceans, sea level would continue to rise for many
centuries beyond 2100 even if concentrations of
greenhouse gases were stabilized at that time.
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Some reports suggest that increase in climate variability or extremes has taken place in recent decades.
However, there are inadequate data to determine whether such global changes have occurred
consistently over the 20th century. On regional scales there is clear evidence of changes in some
extremes and climate variability indicators - for example, fewer frosts in several widespread areas; and an
increase in the proportion of rainfall from extreme events over the contiguous states of the USA. It can
also be seen that the economic damages from weather related disasters have increased dramatically,
although much of this may be attributed to a greater number of people living in vulnerable areas..
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ea-ice draft is the thickness of the
part of the ice that is submerged
under the sea. Comparison of seaice draft data acquired on
submarine cruises between 1993
and 1997 with similar data acquired
between 1958 and 1976 indicates
that the mean ice draft at the end
of the melt season has decreased
by about 1.3 m in most of the deep
water portion of the Arctic Ocean,
from 3.1 m in 1958-1976 to 1.8 m
in the 1990s. In summary: ice draft
in the 1990s is over a meter thinner
than two to four decades earlier.
The main draft has decreased from
over 3 meters to under 2 meters,
and the volume is down by some
40%.
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The global conveyor belt thermohaline circulation is driven primarily by the formation and sinking of deep
water (from around 1500m to the Antarctic bottom water overlying the bottom of the ocean) in the
Norwegian Sea. This circulation is thought to be responsible for the large flow of upper ocean water from
the tropical Pacific to the Indian Ocean through the Indonesian Archipelogo. The two counteracting
forcings operating in the North Atlantic control the conveyor belt circulation: (1) the thermal forcing (highlatitude cooling and the low-latitude heating) which drives a polar southward flow; and (2) haline forcing
(net high-latitude freshwater gain and low-latitude evaporation) which moves in the opposite direction. In
today's Atlantic the thermal forcing dominates, hence, the flow of upper current from south to north.When
the strength of the haline forcing increases due to excess precipitation, runoff, or ice melt the conveyor belt
will weaken or even shut down. The variability in the strength of the conveyor belt will lead to climate
change in Europe and it could also influence in other areas of the global ocean. The North Atlantic
atmosphere-ocean-cryosphere system appears to have natural cycles of many timescales in switching the
conveyor belt. Periodic movement of excessive ice from the Arctic into the Greenland Sea appears to be
responsible for the interdecadal variability of the conveyor belt. There is no evidence yet that the influx of
interdecadal switching extends beyond the North Atlantic Ocean.
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The Nile Delta is one of the oldest intensely cultivated areas
on earth. It is very heavily populated, with population densities
up to 1600 inhabitants per square kilometer. The low lying,
fertile floodplains are surrounded by deserts. Only 2,5% of
Egypt's land area, the Nile delta and the Nile valley, is suitable
for intensive agriculture. Most of a 50 km wide land strip along
the coast is less than 2 m above sea-level and is protected
from flooding by a 1 to 10 km wide coastal sand belt only,
shaped by discharge of the Rosetta and Damietta branches of
the Nile. Erosion of the protective sand belt is a serious
problem and has accelerated since the construction of the
Aswan dam.
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Rising sea level would destroy weak parts of the sand
belt, which is essential for the protection of lagoons and
the low-lying reclaimed lands. The impacts would be
very serious: One third of Egypt's fish catches are made
in the lagoons. Sea level rise would change the water
quality and affect most fresh water fish. Valuable
agricultural land would be innundated. Vital, low-lying
installations in Alexandria and Port Said would be
threatened. Recreational tourism beach facilities would
be endangered and essential groundwater would be
salinated. Dykes and protective measurements would
probably prevent the worst flooding up to a 50 cm sea
level rise. However, it would cause serious groundwater
salination and the impact of increasing wave action
would be serious.
Greenhouse effectThe "greenhouse effect" is the warming that happens when certain gases in Earth's atmosphere trap heat.
These gases let in light but keep heat from escaping, like the glass walls of a greenhouse.First, sunlight shines onto the Earth's
surface, where it is absorbed and then radiates back into the atmosphere as heat. In the atmosphere, “greenhouse” gases trap
some of this heat, and the rest escapes into space. The more greenhouse gases are in the atmosphere, the more heat gets
trapped.Scientists have known about the greenhouse effect since 1824, when Joseph Fourier calculated that the Earth would be
much colder if it had no atmosphere. This greenhouse effect is what keeps the Earth's climate livable. Without it, the Earth's
surface would be an average of about 60 degrees Fahrenheit cooler. In 1895, the Swedish chemist Svante Arrhenius discovered
that humans could enhance the greenhouse effect by making carbon dioxide, a greenhouse gas. He kicked off 100 years of climate
research that has given us a sophisticated understanding of global warming.Levels of greenhouse gases (GHGs) have gone up
and down over the Earth's history, but they have been fairly constant for the past few thousand years. Global average
temperatures have stayed fairly constant over that time as well, until recently. Through the burning of fossil fuels and other GHG
emissions, humans are enhancing the greenhouse effect and warming Earth.Scientists often use the term "climate change" instead
of global warming. This is because as the Earth's average temperature climbs, winds and ocean currents move heat around the
globe in ways that can cool some areas, warm others, and change the amount of rain and snow falling. As a result, the climate
changes differently in different areas.Aren’t temperature changes natural?The average global temperature and concentrations
of carbon dioxide (one of the major greenhouse gases) have fluctuated on a cycle of hundreds of thousands of years as the Earth's
position relative to the sun has varied. As a result, ice ages have come and gone.However, for thousands of years now, emissions
of GHGs to the atmosphere have been balanced out by GHGs that are naturally absorbed. As a result, GHG concentrations and
temperature have been fairly stable. This stability has allowed human civilization to develop within a consistent
climate.Occasionally, other factors briefly influence global temperatures. Volcanic eruptions, for example, emit particles that
temporarily cool the Earth's surface. But these have no lasting effect beyond a few years. Other cycles, such as El Niño, also work
on fairly short and predictable cycles.Now, humans have increased the amount of carbon dioxide in the atmosphere by more than
a third since the industrial revolution. Changes this large have historically taken thousands of years, but are now happening over
the course of decades.Why is this a concern?The rapid rise in greenhouse gases is a problem because it is changing the climate
faster than some living things may be able to adapt. Also, a new and more unpredictable climate poses unique challenges to all
life.Historically, Earth's climate has regularly shifted back and forth between temperatures like those we see today and
temperatures cold enough that large sheets of ice covered much of North America and Europe. The difference between average
global temperatures today and during those ice ages is only about 5 degrees Celsius (9 degrees Fahrenheit), and these swings
happen slowly, over hundreds of thousands of years.Now, with concentrations of greenhouse gases rising, Earth's remaining ice
sheets (such as Greenland and Antarctica) are starting to melt too. The extra water could potentially raise sea levels
significantly.As the mercury rises, the climate can change in unexpected ways. In addition to sea levels rising, weather can become
more extreme. This means more intense major storms, more rain followed by longer and drier droughts (a challenge for growing
crops), changes in the ranges in which plants and animals can live, and loss of water supplies that have historically come from
glaciers.Scientists are already seeing some of these changes occurring more quickly than they had expected. According to the
Intergovernmental Panel on Climate Change, eleven of the twelve hottest years since thermometer readings became available
occurred between 1995 and 2006.
www.climatechange.umaine.edu/.../ html/09.html
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