ANAKHA MOHAN ACADEMY OF CLIMATE CHANGE EDUCATION AND RESEARCH KAU

1. NATURAL AND ANTHROPOGENIC
RADIATIVE FORCING
IPCC AR5
Anakha mohan
2014-20-123
Academy Of Climate Change
Education And Research, KAU
Vellanikkara
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2.  The intergovernmental panel on climate change
 International body for assessing the science related to
climate change
 Was set up in 1988
 By the World Meteorological Organization (WMO) and United
Nations Environment Programme (UNEP)
IPCC
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3. The IPCC's headquarters in Geneva, Switzerland
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4.  Working Group I assesses the scientific aspects of the climate system and
climate change ·
 Working Group II addresses the vulnerability of socio- economic and natural
systems to climate change, negative and positive consequences of climate
change, and options for adapting to it·
 Working Group III assesses options for limiting greenhouse gas emissions
and otherwise mitigating climate change
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5. Radiative forcing or climate forcing is defined as the difference of
insolation (sunlight) absorbed by the Earth and energy radiated back
to space.
Anthropogenic forcing is a change in the Earth’s energy
balance due to human activities.
Natural and anthropogenic radiative forcing
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6.  The planet was in radiative balance with space before the industrial
revolution. Human activities have altered this balance. The net impact of
any perturbation can be quantified via a net power input into the planet,
This is its radiative forcing.
 Positive forcing warm the planet
 AR5 recognises this for the first time, and designates the total forcing
including these effects as the effective radiative forcing.
Cont’d
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7.  Human influence on the climate system is clear, and recent anthropogenic
emissions of greenhouse gases are the highest in history. Recent climate
changes have had widespread impacts on human and natural system
 Which driven atmospheric concentrations of carbon dioxide, methane and
nitrous oxide to levels that are unprecedented in at least the last 800,000
years, leading to an uptake of energy by the climate system.
 Radiative forcing quantifies the perturbation of energy into the Earth
system caused by these drivers. Radiative forcing larger than zero lead to
a near-surface warming, and radiative forcing smaller than zero lead to a
cooling.
Cont’d
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8.  Atmospheric concentrations of GHGs are at levels that are unprecedented
in at least 800,000 years. Concentrations of carbon dioxide (CO2), methane
(CH4) and nitrous oxide (N2O) have all shown large increases since 1750
(40%, 150% and 20%, respectively)
Cont’d
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9. 9
For example,

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11. Natural forcing only would have cooled
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12. Anthropogenic with natural forcing fit
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13.  The radiative forcing from aerosols, which includes cloud adjustments, is
better understood and indicates a weaker cooling effect than in AR4. The
aerosol radiative forcing over 1750–2011 is estimated as –0.9 W/m2
(medium confidence).
 There is high confidence that the global mean total aerosol radiative forcing
has counteracted a substantial portion of radiative forcing from well mixed
GHGs. Aerosols continue to contribute the largest uncertainty to the total
radiative forcing estimate.
The radiative forcing from aerosols
About 5 out of 10 chance About 8 out of 10 chance
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14. Human activities affecting emission drivers
 About half of the cumulative anthropogenic CO2 emissions between 1750 and
2011 have occurred in the last 40 years (high confidence).
 About 40% of these anthropogenic CO2 emissions have remained in the
atmosphere since 1750. The rest was removed from the atmosphere by sinks,
and stored in natural carbon cycle reservoirs
 Total annual anthropogenic GHG emissions have continued to increase over
1970 to 2010 with larger absolute increases between 2000 and 2010 (high
confidence)
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17.  CO2 emissions from fossil fuel combustion and industrial processes
contributed about 78% to the total GHG emission increase between 1970
and 2010, with a contribution of similar percentage over the 2000–2010
period (high confidence).
 Total annual anthropogenic GHG emissions have increased by about 10
GtCO2 between 2000 and 2010. This increase directly came from the
energy (47%), industry (30%), transport (11%) and building (3%) sectors
(medium confidence). Accounting for indirect emissions raises the
contributions by the building and industry sectors (high confidence).
Cont’d
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18.  Globally, economic and population growth continue to be the most
important drivers of increases in CO2 emissions from fossil fuel
combustion. The contribution of population growth between 2000
and 2010 remained roughly identical to that of the previous three
decades, while the contribution of economic growth has risen
sharply (high confidence)
Cont’d
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20.  Estimated present-day radiative forcing is higher than in AR4 due to:
larger estimates of black carbon forcing, smaller estimate of aerosol
cloud-mediated cooling effect, and increased greenhouse gases since
2007.
 CO2 overwhelms other forcing, in most future scenarios.
 Natural forcing only would have cooled, Anthropogenic with natural
forcing fit to current observations
In a nut shell
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21. REFERENCE
IPCC fourth assessment report; WGII; chapter 2; Changes in
Atmospheric Constituents and in Radiative Forcing; page no. 131-
217
IPCC Fifth assessment report; WGII; chapter 8; Anthropogenic and
Natural Radiative Forcing; page no.661-731
IPCC Climate Change 2014 Synthesis Report page no.39-48
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22. Think now and decide here….
Thankyou22