DAV PUBLIC SCHOOL - Climate change2


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DAV PUBLIC SCHOOL - Climate change2

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DAV PUBLIC SCHOOL - Climate change2

  1. 1. Presented by : Siddarth class -5th- E D.A.V .Public School Sec -7 Rohini Climate change
  2. 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. 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. 4. climate change Ocean variability  Orbital variations  Solar output  Volcanism  Plate tectonics  Global warming
  5. 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 Archaeological evidence, oral history and historical documents can offer insights into past changes in the climate.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. 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. 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. 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.”