DAV PUBLIC SCHOOL - Climate change2

1. Presented by : Siddarth
class -5th- E
D.A.V .Public School
Sec -7 Rohini
Climate change

2. Introduction
 Climate change is a significant and lasting
change in the statistical distribution
of weather patterns over periods ranging
from decades to millions of years. It may be a
change in average weather conditions, or in
the distribution of weather around the
average conditions (i.e., more or fewer
extreme weather events). Climate change is
caused by factors that include oceanic
processes (such as oceanic circulation),
variations in solar radiation received by
Earth, plate tectonics and volcanic eruptions
, and human-induced alterations of the
natural world; these latter effects are
currently causing global warming, and
"climate change" is often used to describe
human-specific impacts.

3.  Scientists actively work to understand
past and future climate by
using observations and theoretical
models. Borehole temperature
profiles, ice cores , floral and faunal
records, glacial and per glacial
processes, stable isotope and other
sediment analyses, and sea level
records serve to provide a climate
record that spans the geologic past.
More recent data are provided by the
instrumental record. Physically
based general circulation models are
often used in theoretical approaches to
match past climate data, make future
projections, and link causes and
effects in climate change.

4. climate
change Ocean variability
 Orbital variations
 Solar output
 Volcanism
 Plate tectonics
 Global warming

5. Physical evidence for and examples of
climatic change
 Temperature measurements and proxies
The instrumental temperature record from surface
stations was supplemented byradiosonde balloons,
extensive atmospheric monitoring by the mid-20th
century, and, from the 1970s on, with global satellite
data as well. The 18O/16O ratio in calcite and ice core
samples used to deduce ocean temperature in the
distant past is an example of a temperature proxy
method, as are other climate metrics noted in
subsequent categories.
 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history and historical documents can offer insights into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.

6. Terminology
 The most general definition of climate
change is a change in the statistical
properties of the climate system when
considered over long periods of time,
regardless of cause. Accordingly,
fluctuations over periods shorter than
a few decades, such as El Niño , do not
represent climate change.
 The term sometimes is used to refer
specifically to climate change caused by
human activity, as opposed to changes
in climate that may have resulted as
part of Earth's natural processes. In
this sense, especially in the context
of environmental policy, the
term climate change has become
synonymous with anthropogenic global
warming. Within scientific
journals, global warming refers to
surface temperature increases
while climate change includes global
warming and everything else that
increasing greenhouse gas levels will

7. Effects of global warming on oceans
 Global warming in the last century has
increased sea levels worldwide, though
there are regional variations; see sea
level rise. Although global warming has
affected the volume of seawater in all
of the world’s oceans, it is important to
look at the change in sea level in
particular coastal areas, especially
throughout short periods of time (fifty
to hundred years). In order to estimate
the rise in global seawater level,
scientists combine sea level trends at
tidal stations around the world.
 There are a number of factors
affecting rising sea levels; the first one
being thermal expansion of seawater,
and the second being melting
glaciers and ice sheets ; human changes
to groundwater storage are also
detectable. With regards to thermal
expansion, the increase in the
atmosphere’s greenhouse gas content

8.  . Despite water’s high heat capacity, this
heat that is radiated into the ocean by
greenhouse gases in the atmosphere cause
water molecules to expand, thus creating
more water volume in the oceans. With
concern to melting glaciers and ice sheets,
global warming also has an enormous impact.
Higher global temperatures melt a larger mass
of sea ice, especially near Greenland and this
new source of water enters the oceans, thus
also increasing the amount of seawater. The
rise in global sea levels poses many threats.
According to the U.S. Environmental
Protection Agency (EPA), “such a rise would
inundate
coastal wetlands and lowlands, erode beaches
, increase the risk of flooding, and increase
the salinity of estuaries, aquifers, and
wetlands.”