This is the fourth lesson titled 'Attributions of climate change' of the course ' Climate Change and Global environment' conducted at the Faculty of Social Sciences and Humanities of the Rajarata University of Sri Lanka.

1. Climate Change & Global
Environment
Department of Environmental Management
Rajarata University of Sri Lanka
BA (Special) in Environmental Management
EMGT 4234
Lesson 4 - Attribution of climate change
P.B. Dharmasena
0777 613234, 0717 613234
dharmasenapb@ymail.com , dharmasenapb@gmail.com
https://independent.academia.edu/PunchiBandageDharmasena
https://www.researchgate.net/profile/Punchi_Bandage_Dharmasena/contributions
http://www.slideshare.net/DharmasenaPb

2. What is Attribution?
Attribution: The process of evaluating the relative contributions of
multiple causal factors to a change or an event with an assignment of
statistical confidence
Understanding how climate change works
Effort of identifying mechanisms responsible for recent climate changes on
Earth, commonly known as 'global warming'.
The dominant mechanisms are anthropogenic, i.e., the result of human activity.
They are:
• increasing atmospheric concentrations of greenhouse gases
• global changes to land surface, such as deforestation
• increasing atmospheric concentrations of aerosols.

3. Detection vs. attribution
• Detection of a climate signal does
not always imply significant
attribution.
• Detection of a signal requires
demonstrating that an observed
change is statistically
significantly different from that
which can be explained by
natural internal variability. That
process is called ‘Attribution’.

5. Plausible - possible

9. So far …………………….
• Climate and weather
• Climate variability and climate change
• Factors affecting climate
• Natural (sun, volcanoe, ocean currents, atmospheric circulation,
sea ice, land covers)
• Human factors
• (GHGs – water vapour, aerosols, CO2, CH4, N2O, O3)
• Land use change
• Climate and AE regions of Sri Lanka (24 zones, 49 sub zones)
• Climate change - increase in variance and mean
• Some human-induced environmental changes relevant to climate
• Impact on ecosystems
• Climate change situation in Sri Lanka
• Earth systems – human systems interaction
• Drivers of climate change – natural divers, important GHGs,
contribution of anthropogenic drivers
• Detection and attributions

10. Key attributions of Climate Change
• Greenhouse gases
• Water vapour
• Land use
• Livestock and land use
• Aerosols

11. Greenhouse gases
• Carbon dioxide is the primary greenhouse gas that is contributing to recent climate
change.
• CO2 is absorbed and emitted naturally as part of the carbon cycle, through animal
and plant respiration, volcanic eruptions, and ocean-atmosphere exchange.
• Human activities, such as the burning of fossil fuels and changes in land use (see
below), release large amounts of carbon to the atmosphere, causing CO2
concentrations in the atmosphere to rise.
• Along with CO2, methane and nitrous oxide are also major forcing contributors to
the greenhouse effect. The Kyoto Protocol lists these together with
hydrofluorocarbon (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride
(SF6), which are entirely artificial (i.e. anthropogenic) gases, which also
contribute to radiative forcing in the atmosphere.
• The chart (next slide) attributes anthropogenic greenhouse gas emissions to eight
main economic sectors, of which the largest contributors are power stations (many
of which burn coal or other fossil fuels), industrial processes, transportation fuels
(generally fossil fuels), and agricultural by-products (mainly methane from enteric
fermentation and nitrous oxide from fertilizer use)

13. Water vapour
• Water vapour is the most abundant greenhouse gas and also the most
important in terms of its contribution to the natural greenhouse effect,
despite having a short atmospheric lifetime (about 10 days).
• Some human activities can influence local water vapour levels.
However, on a global scale, the concentration of water vapour is
controlled by temperature, which influences overall rates of
evaporation and precipitation.
• Therefore, the global concentration of water vapour is not substantially
affected by direct human emissions.

14. Land use
Climate change is attributed to land use for two main reasons.
• Between 1750 and 2007,
• about two-thirds of anthropogenic CO2 emissions were produced from burning
fossil fuels, and
• about one-third of emissions from changes in land use, primarily deforestation.
Deforestation both reduces the amount of carbon dioxide absorbed by
deforested regions and releases greenhouse gases directly, together with
aerosols, through biomass burning that frequently accompanies it.
• A second reason that climate change has been attributed to land use is
that the terrestrial albedo is often altered, which leads to radiative
forcing. This effect is more significant locally than globally.
Albedo - the proportion of the incident light or radiation
that is reflected by a surface (0-1)

15. Livestock and land use
• Worldwide, livestock production occupies 70% of
all land used for agriculture, or 30% of the ice-free
land surface of the Earth.
• More than 18% of anthropogenic greenhouse gas
emissions are attributed to livestock and livestock-
related activities such as deforestation and
increasingly fuel-intensive farming practices.
• Specific attributions to the livestock sector
include:
• 9% of global anthropogenic carbon dioxide emissions
• 35–40% of global anthropogenic methane emissions
(chiefly due to enteric fermentation and manure)
• 64% of global anthropogenic nitrous oxide emissions,
chiefly due to fertilizer use.[2

16. Aerosols
• Aerosols are small particles or droplets
suspended in the atmosphere.
• Key sources to which anthropogenic
aerosols are attributed include:
• biomass burning such as slash-and-burn
deforestation. Aerosols produced are
primarily black carbon.
• industrial air pollution, which produces soot
and airborne sulfates, nitrates, and
ammonium.
• dust produced by land use effects such as
desertification

17. Global Warming: Attribution
 How do we identify
humanity’s contribution
to climate?
 First, we know there is a
strong correlation
between global
temperature and CO2
concentration, but on a
VERY long time-scale
(tens of thousands of
years)

18. Global Warming: Attribution
The rate of CO2 increase
has been steady up to the
early 2000’s, although there
is some evidence it is
dropping.

19. Global Warming: Attribution
 We can “fingerprint”
CO2 concentrations
by it’s mass (ratio of
various isotopes) and
there is no doubt that
some of the increase
in CO2 is generated
by humans (industry)

20. Model Projections
 Climate models project an
increase in global temperature
of 1.5o – 12o F by the year 2100.
 This has brought worries about:
 Increased heat waves
 Droughts
 Floods
 Hurricanes
 Storminess
 Habitat loss
 Etc…….

21. Natural climate variability: (Dr. Roy Spencer, NASA)
~100 Year Periods of Warming and Cooling have been Common Over the Last 2,000 Years. If recent
warming is caused by CO2, then what caused all the other periods Medieval Warm Period of warming
and cooling?
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
0 200 400 600 800 1000 1200 1400 1600 1800 2000
YEAR (AD)
TemperatureAnomaly(deg.C)
Vikings
arrive in
Greenland
End of Viking
colonization of
Greenland
Medieval Warm Period
Little Ice Age
Climate change: The case against?

22. Global Warming: The case against?
 Volcanism – scientists
have shown that
Volcanic forcing tends
to cool climate, and
the last 150 years have
been relatively quiet!

23. What has been observed?
 In Missouri……. (Missouri Climate Center)

24. Climate, Climate Change & Hurricanes
 Is global warming increasing the hurricane numbers?
g
j
yh
j
Y
j
1940 1950 1960 1970 1980 1990 2000
0
5
10
15
a) All Hurricanes
Years
AllHurricanes

25. 200
400
600
800
1000
1200
1400
1600
1800
2000
1905 1915 1925 1935 1945 1955 1965 1975 1985 1995 2005
Year
September - December rainfall at Mahailluppallama

26. Is Global Warming Happening Now?

27. Temp, Sea Level, Snow Cover
Temperature (surface not stratosphere)
11 of last 12 years (1995-2006) rank among
the 12 warmest years in record of global
surface temperature since 1850
100 yr (1906-2005) = + 0.74 ± 0.18 C/century
50 yr (1956-2005) = + 1.3 ± 0.3 C/century
Sea Level (tide gauges blue, satellites red)
1961-2003 = + 1.8 ± 0.5 mm/yr
1993-2003 = + 3.1 ± 0.7 mm/yr
57% from ocean expansion
28% melting glaciers and ice caps
15% melting polar ice sheets
N. Hemisphere Snow (March-April)
1978-2005 = −2.7 ± 0.6 % per decade
drop in average Arctic sea ice extent
IPCC Fourth Assessment Report 2007
Synthesis Report, page 31
changes relative to means 1961-1990
curves are decadal averages
shaded regions are uncertainties

28. Global Temperatures
pollution cooling?

29. Continental Temperature Curves
Surface Temperatures
6 out of 7 landmasses
temperatures up 1906-2005
simulations include
blue natural = Sun + volcanoes
red natural + anthropogenic
IPCC Fourth Assessment Report 2007
Synthesis Report, page 40

30. Global Sea Levels
University of Colorado at Boulder
website update of TOPEX/Poseidon & Jason satellite data, 2008

31. Arctic Ice Melt
Stroeve et al. 2007, Geophysical Research Letters
National Center for Atmospheric Research (NCAR)
University of Colorado National Snow and Ice Data Center (NSIDC), NASA QuikScat and IceSAT satellites
30 years ahead of predictions
satellite observations since 1979
6 most recent years 2004-2009
are the lowest 6 since 1979
seasonal thin ice in 2008 was 70%
was 40-50% in 1980s/1990s
EARTH ALBEDO CHANGING

32. IPCC Conclusion
“Warming of the climate system is unequivocal
(clear), as is now evident from observations of
increases in global average air and ocean
temperatures, widespread melting of snow and ice
and rising global average sea level.”
IPCC Fourth Assessment Report, page 72

33. Definitive Proof