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Climate change

 

 

 

 

 

 

 

Prepared by:
Sana Salah Abdulkareeem

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Date of Submission:  
Jan 16, 2018

 

 

 

Contents
Introduction. 3
Causes. 4
Internal forcing mechanisms. 4
External forcing
mechanisms. 6
Physical evidence. 9
Temperature
measurements and proxies. 9
Ice cores. 9
Animals. 10
Arctic sea ice
loss. 10
Historical and
archaeological evidence. 11
Vegetation. 11
Pollen analysis. 12
Sea level change. 12
What can we do to stop
climate change?. 13
Conclusion. 14
References. 15
 

 

Introduction

Climate change is a change in the statistical
distribution of weather patterns when this change lasts for extended
period of time (i.e., decades to millions of years). Climate change may refer
to a change in average weather conditions, or in the time variation of weather
within the context of longer-term average conditions. Climate change is caused
by factors such as biotic processes, variations in solar radiation received by Earth, plate tectonics, and volcanic
eruptions. Certain
human activities have been identified as primary causes of ongoing climate
change, often referred to as global warming.1

Scientists actively work to know and understand
past and future climate by using observations and theoretical models. A climate
record—extending deep into the Earth’s past—has been assembled, and continues
to be built up, based on geological evidence from borehole temperature profiles, cores removed from deep accumulations of ice, floral and faunal records, glacial and periglacial processes, stable-isotope and other
analyses of sediment layers, and records of past sea levels. More recent data
are provided by the instrumental record. General
circulation models, based on
the physical
sciences, are often
used in theoretical approaches to match past climate data, make future projections,
and link causes and effects in climate change.

Weather
and climate are not the same thing. weather is what is happening outside your
window right now. Weather is short term, limited area, can change rapidly, difficult
to predict.

 

Climate
is the average of many years of weather observation. Climate is long term, wide
area, seasonal change, measured over long spans of time.

Causes

 

Factors that can shape climate are called climate
forcings or “forcing mechanisms”.

Forcing
mechanisms can be either “internal” or “external”. Internal
forcing mechanisms are natural processes within the climate system itself
(e.g., the thermohaline circulation). External forcing mechanisms can be either
natural (e.g., changes in solar output, the earth’s orbit, volcano eruptions)
or anthropogenic (e.g. increased emissions of greenhouse gases and dust).

 

 

Internal forcing mechanisms

 

Scientists generally define the five
components of earth’s climate system to include atmosphere, hydrosphere, cryosphere, lithosphere (restricted
to the surface soils, rocks, and sediments), and biosphere. Natural changes in
the climate system (“internal forcings”) result in internal
“climate variability

 

1.Ocean-atmosphere
variability

The ocean
and atmosphere can work together to spontaneously generate internal climate
variability that can persist for years to decades at a time. These variations can affect global average surface
temperature by redistributing heat between the deep ocean and the atmosphere and/or
by altering the cloud/water vapor/sea ice distribution which could affect the
total energy budget of the earth.

 

2.Life

Life affects
climate through its role in the carbon and water cycles and through such mechanisms
as albedo, evapotranspiration, cloud formation, and weathering.23 Examples of how life may have
affected past climate include:

glaciation 2.3 billion years ago
triggered by the evolution of oxygenic photosynthesis, which depleted the atmosphere
of the greenhouse gas carbon dioxide and introduced free oxygen. 4
another glaciation 300 million
years ago ushered in by long-term burial of decomposition-resistant detritus of vascular land-plants
(creating a carbon
sink and forming coal) 4
termination of the Paleocene-Eocene Thermal Maximum 55 million years ago by
flourishing marine phytoplankton5
reversal of global warming 49
million years ago by 800,000 years of arctic azolla
blooms5
global cooling over the past 40 million
years driven by the expansion of grass-grazer ecosystems6

 

 

 

 

 

 

 

 

External forcing mechanisms

 

1.Orbital variations

Slight
variations in Earth’s motion lead to changes in the seasonal distribution of
sunlight reaching the Earth’s surface and how it is distributed across the
globe. There is very little change to the area-averaged annually averaged
sunshine; but there can be strong changes in the geographical and seasonal
distribution. The three types of kinematic change are variations in
Earth’s eccentricity, changes in the tilt angle of Earth’s axis of
rotation, and precession of Earth’s axis. Combined
together, these produce Milankovitch
cycles which have
an impact on climate and are notable for their correlation to glacial and interglacial
periods, their
correlation with the advance and retreat of the Sahara, and for their appearance in the stratigraphic record.7

 

2. Solar output

The Sun was
the predominant source of energy input to the Earth. Other
sources include geothermal energy from the Earth’s core,
tidal energy from the Moon and heat from the decay of radioactive compounds.
Both long- and short-term variations in solar intensity are known affect global
climate. 7

 

 

 

 

 

3.Volcanism

The eruptions considered to be large enough
to affect the Earth’s climate on a scale of more than 1 year are the ones that
inject over 100,000 tons of SO2 into the stratosphere. This is due to the optical
properties of SO2 and sulfate aerosols, that strongly absorb or
scatter solar radiation, creating a global layer of sulfuric acid haze. On average, such
eruptions occur several times per century, and cause cooling (by partially
blocking the transmission of solar radiation to the Earth’s surface) for a
period of a few years. 8

 

4.Plate
tectonics

Over the
course of millions of years, the motion of tectonic plates reconfigures global
land and ocean areas and generates topography. This can affect both global and
local patterns of climate and atmosphere-ocean circulation.

 

The position
of the continents determines the geometry of the oceans and therefore
influences patterns of ocean circulation. The locations of the seas are
important in controlling the transfer of heat and moisture across the globe,
and therefore, in determining global climate. 8

 

5.Human
influences

In the
context of climate variation, anthropogenic factors are human activities which influence
the climate. The scientific consensus on climate change is “that climate is
changing and that these changes are in large part caused by human
activities,” and it “is largely irreversible.” 8

 

6.Greenhouse
gas

Greenhouse
gases are those that absorb and emit infrared radiation in the wavelength
range emitted by Earth.8 In order, the most abundant
greenhouse gases in Earth’s atmosphere are:

Water vapor (H2O)
Carbon dioxide (CO2)
Methane (CH4)
Nitrous oxide (N2O)
Ozone (O3)
Chlorofluorocarbons (CFCs)
Hydrofluorocarbons (incl. HCFCs and HFCs)

 

Atmospheric
concentrations of greenhouse gases are determined by the balance between
sources (emissions of the gas from human activities and natural systems) and
sinks (the removal of the gas from the atmosphere by conversion to a different
chemical compound). The proportion of an emission remaining in the
atmosphere after a specified time is the “airborne fraction” (AF). The annual airborne
fraction is the ratio of the atmospheric increase in a given year to that
year’s total emissions. As of 2006 the annual airborne fraction for CO2 was
about 0.45. The annual airborne fraction increased at a rate of
0.25 ± 0.21% per year over the period 1959–2006.8

 

 

 

Physical
evidence

 

Temperature measurements and proxies

 

The instrumental temperature record from surface stations was
supplemented by radiosonde
balloons, extensive
atmospheric monitoring by the mid-20th century, and, from the 1970s on,
with global satellite data as well. Taking the record as a whole, most of the 20th
century had been unprecedentedly warm, while the 19th and 17th centuries were
quite cool.9

 

Glaciers

Glaciers are among the most sensitive
indicators of climate change. Their size is determined by a mass balance between snow input and melt
output. As temperatures warm, glaciers retreat unless snow precipitation
increases to make up for the additional melt; the converse is also true.
9

 

Ice cores

 

Analysis of
ice in a core drilled from an ice sheet such as the Antarctic
ice sheet, can be
used to show a link between temperature and global sea level variations. The
air trapped in bubbles in the ice can also reveal the CO2 variations
of the atmosphere from the distant past, well before modern environmental
influences. 9

 

 

Animals

 

Remains
of beetles are common in freshwater and
land sediments. Different species of beetles tend to be found under different
climatic conditions. Given the extensive lineage of beetles whose genetic
makeup has not altered significantly over the millennia, knowledge of the
present climatic range of the different species, and the age of the sediments
in which remains are found, past climatic conditions may be inferred. The
studies of the impact in vertebrates are few mainly from developing countries,
where there are the fewest studies; between 1970 and 2012, vertebrates declined
by 58 percent, with freshwater, marine, and terrestrial populations declining
by 81, 36, and 35 percent, respectively. 10

 

 

Arctic sea ice loss

 

The decline
in Arctic sea ice, both in extent and thickness, over the last several decades
is further evidence for rapid climate change. Sea ice is frozen seawater
that floats on the ocean surface. It covers millions of square kilometers in
the polar regions, varying with the seasons. In the Arctic, some sea ice remains year after
year, whereas almost all Southern Ocean or Antarctic sea ice melts away
and reforms annually. Satellite observations show that Arctic sea ice is now
declining at a rate of 13.2 percent per decade, relative to the 1981 to 2010
average. 10

 

 

Historical and archaeological evidence

 

Climate
change in the recent past may be detected by corresponding changes in
settlement and agricultural patterns. Archaeological evidence, oral history and historical
documents can
offer insights into past changes in the climate. Climate change effects have
been linked to the collapse of various civilizations.9

 

Vegetation

 

A change in
the type, distribution and coverage of vegetation may occur given a change in
the climate. Some changes in climate may result in increased precipitation and
warmth, resulting in improved plant growth and the subsequent sequestration of
airborne CO2. A gradual increase in warmth in a region will lead to
earlier flowering and fruiting times, driving a change in the timing of life
cycles of dependent organisms. Conversely, cold will cause plant bio-cycles to
lag.9

 

Forest genetic resources

 

Even though this is a field with
many uncertainties, it is expected that over the next 50 years climate changes
will have an effect on the diversity of forest genetic
resources and thereby on the
distribution of forest tree species and the composition of forests. Diversity
of forest genetic
resources enables the potential for a
species (or a population) to adapt to climatic changes and related future
challenges such as temperature changes, drought, pests, diseases and forest
fire.

 

Pollen analysis

 

Palynology is the study of contemporary
and fossil palynomorphs, including pollen. Palynology is used to infer the
geographical distribution of plant species, which vary under different climate
conditions. Different groups of plants have pollen with distinctive shapes and
surface textures, and since the outer surface of pollen is composed of a very
resilient material, they resist decay. Changes in the type of pollen found in
different layers of sediment in lakes, bogs, or river deltas indicate changes
in plant communities. 9

 

 

Sea level change

 

Global sea
level change for much of the last century has generally been estimated
using tide gauge measurements collated over long
periods of time to give a long-term average. More recently, altimeter measurements — in
combination with accurately determined satellite orbits — have provided an
improved measurement of global sea level change. To measure sea levels
prior to instrumental measurements, scientists have dated coral reefs that grow near the surface of
the ocean, coastal sediments, marine terraces, ooids in limestones, and nearshore archaeological
remains. The predominant dating methods used are uranium
series and radiocarbon, with cosmogenic radionuclides being sometimes used to date terraces that have
experienced relative sea level fall. 10

 

What can we do to stop climate change?

 

1.Reduce
fossil fuel use

Burning fossil fuels increases the
levels of greenhouse gases in the atmosphere.

 

2.Plant Trees

Because carbon dioxide is the most
important greenhouse gas, planting trees and other plants can slow or stop
global warming. Plants take in carbon dioxide and release oxygen.

 

3.Reduce Waste

The production of garbage
contributes to global warming both directly and indirectly. Decomposing waste
in landfills produces methane and other greenhouse gases.

 

4.Conserve Water

Cities consume significant amounts
of energy when purifying and distributing water, which contributes to
greenhouse gas emissions. Saving water reduces the amount of energy used.

 

 

 

 

Conclusion

 

–      Climate change is a change which is attributed directly or
indirectly to human activity.

 

–       It caused by internal and
external forcing mechanism.

 

–      Evidence of climate change comes from different source such as
increase of temperature, move of animals and arctic sea ice loss.

 

–      There are several ways to stop climate change like reduce fossil
fuel use, plant trees, reduce waste and conserve water.

 

References

 

1-   
America’s
Climate Choices: Panel on Advancing the Science of Climate Change; National
Research Council (2010).

2-   
 Christner, B.
C.; Morris, C. E.; Foreman, C. M.; Cai, R.; Sands, D. C. (2008). “Ubiquity
of Biological Ice Nucleators in
Snowfall”. Science. 319 (5867): 1214. 

3-   
Schwartzman,
David W.; Volk, Tyler (1989). “Biotic enhancement of weathering and the
habitability of Earth”. Nature. 340 (6233): 457–460. 

4-   
Kasting,
J. F.; Siefert, JL (2002). “Life and the Evolution of Earth’s
Atmosphere”. Science. 296 (5570): 1066–8.

5-   
Zachos,
J. C.; Dickens, G. R. (2000). “An assessment of the biogeochemical
feedback response to the climatic and chemical perturbations of the
LPTM”. GFF. 122: 188–189. 

6-   
Retallack,
Gregory J. (2001). “Cenozoic Expansion of Grasslands and Climatic
Cooling”. The Journal of Geology. 109 (4): 407–426. 

7-   
Gale,
Andrew S. (1989). “A Milankovitch scale for Cenomanian
time”. Terra Nova. 1 (5): 420–425. 

8-   
Miles,
M. G.; Grainger, R. G.; Highwood, E. J. (2004). “The significance of volcanic
eruption strength and frequency for climate” (pdf). Quarterly Journal of the Royal Meteorological
Society. 130 (602): 2361–2376.

9-   
Demenocal,
P. B. (2001). “Cultural
Responses to Climate Change During the Late Holocene” (PDF). Science. 292 (5517): 667–673. 

10-
 Hughes,
Malcolm K.; Swetnam, Thomas W.; Diaz, Henry F., eds. (2010). Dendroclimatology:
progress and prospect. Developments
in Paleoenvironmental Research. volume 11. New York: Springer Science &
Business Media. ISBN 978-1-4020-4010-8.

 

 

 

 

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