GLOBAL WARMING Dr.Charu Khosla Gupta Department of Botany Acharya

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GLOBAL WARMING Dr.Charu Khosla Gupta Department of Botany Acharya Powered By Docstoc

Dr.Charu Khosla Gupta
Department of Botany
Acharya Narendra Dev College
University of Delhi

  The Climate of the Earth is always changing. In the past it has
  altered as a result of natural causes. Nowadays, however, the
  term climate change is generally used when referring to changes
  in our climate which have been identified since the early part of
  the 1900's. The changes we've seen over recent years and those
  which are predicted over the next 80 years are thought to be
  mainly as a result of human behavior rather than due to natural
  changes in the atmosphere.
  The Greenhouse effect is very important when we talk about
  climate change as it relates to the gases which keep the Earth
  warm. It is the extra greenhouse gases which humans have
  released which are thought to pose the strongest threat.

Global means surface temperatures have increased over last several
years especially in last 20 years. The Land and Oceans have
warmed up drastically and even the Sea Levels have risen.
An increasing body of observations gives a collective picture of a
warming world and other changes in the climate system. It is
observed that the Global-average surface temperature increased by
about 0.6 ºC over 20th century. 1990s was the warmest decade and
1998 warmest year in last 1000 years in Northern Hemisphere.
Over last 50 years night-time minimum temperatures increased by
about 0.2 ºC per decade and there has been nearly 10% reduction
in snow cover ice since late 1960s. Also there has been a reduction
of about two weeks in annual duration of lake and river ice over
20th century. Mountain glaciers have retreated drastically during
the 20th century. Also, the Northern Hemisphere spring and
summer sea-ice extent decreased by 10-15% since 1950s.
Scientists have observed a 40% decline in Arctic sea-ice thickness
in recent decades. There has been a Global-average sea level
increase by 10-20 cm during 20th century. Moreover, 0.5-1% per
decade increase in precipitation has taken place during 20th
century and 2-4% increase in frequency of heavy precipitation
events in Northern Hemisphere mid- and high-latitudes over latter.
Are we responsible for this change in climate? We hear about
Glaciers are retreating all over the world. The South Cascade
glacier retreated dramatically in the 20th century. Who is
responsible for all this? The main causes of tjis warming of the
Earth’s surface are:
      • Carbon dioxide gas released by burning of fossil fuels in
          cars, factories and electricity
      • Methane released from land fills and agriculture
      • Nitrous oxides released by over use from fertilizers
      • Gases used for refrigeration and other purposes
      • Loss of forest cover.
Human activities have changed the composition of the atmosphere
since the pre- industrial era. We have just seen how these gases are
effecting our environment. If we compare the warmth caused by
each of these gases in the atmosphere, then we see that carbon di
oxide is responsible for minimum warming, keeping the
concentrations same. See figures below:
   • Carbon dioxide                     1
   • Methane                            20
   • Nitrous oxide                      300
   • CFC’s                              1000
   But the concentration of Carbon di Oxide is very high compared
   to all other gases in the atmosphere at any given time. How is
   this Warming impacting us! There has been a rise in global
   temperatures by about 0.74C. Sea levels have risen by about
   3mm a year. All major glaciers are retreating. The frequency of
   Droughts and floods have increased. Also there has been
   Diminishing food supply and agriculture in last few decades.
   Rise in sea levels lead to flooding of nearby fertile areas and the
  fertility is lost because of salt water. At given point of time,
  once there would be flooding after which we shall lose all our
  fresh waters. This warming is also a threat to migratory birds,
  Loss of mangroves, biodiversity, coral reefs, threat to Polar
  bears with melting arctic etc. Developing countries are the most
  vulnerable to climate change as here the Impacts are worse – as
  there are already more floods and areas are drought prone
  and a large share of the economy is in climate sensitive
  sectors. They have Lower capacity to adapt because of a lack
  of financial, institutional and technological capacity and
  access to knowledge. Climate change is likely to impact
  disproportionately upon the poorest countries and the poorest
  persons within countries, exacerbating inequities in health
  status and access to adequate food, clean water and other
  resources. Net market sector effects are expected to be negative
  in most developing countries.

A recent paper in Nature says that Carbon in the atmosphere is
forever. It takes hundreds of years to negate the effects of
What happens to Carbon dioxide that we emit?
   • Soaked by the ocean by a few hundred years. First being
     absorbed by surface waters and eventually into deeper
   • On a much longer time scale of several thousand years, most
     of the remaining carbon dioxide gets taken up, as the gas
     dissolves into the ocean and reacts with chalk in ocean
   • Weathering of rocks during which atmospheric carbon
     dioxide reacts with water to form a weak acid that dissolves
     rocks. This creates minerals such as Magnesium carbonate
     that lock away the green house gases.

 Recently, there has been an awareness about leaning the
environment as clean development mechanism.
‘The Clean Development Mechanism’ or the CDM is a system in
which the participating countries can meet some of the Greenhouse
gas emissions by buying certified carbon credits from projects in
Developing countries that reduce emissions. This has set a market
for ‘CARBON OFFSETTING’ after the Kyoto Protocol in 2001.
Tree plantations are the most sought after Method of Carbon
Offsetting. This is also referred to as a green investment as we are
investing in plants.

Green Investment
    • Carbon offsetting: A carbon offset is a credit that an
      individual or organization can purchase to negate a carbon
      footprint. When the number of carbon offsets obtained is
      equal to an individual or organization's carbon footprint, that
      person or organization is carbon neutral.
    • Carbon sequestration: A process whereby trees and other
      plants remove carbon dioxide from the atmosphere and
      through photosynthesis, turn it into plant material.
If the civilization is able to develop ways of scrubbing Carbon
dioxide out of the atmosphere, it is possible that we could reverse
the Carbon dioxide hangover

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