What the 2007 Reports of the
IPCC mean
Gordon J. Aubrecht, II
Ohio State University
Talk presented at the AAPT Summer Meeting,
Greensboro, NC, July 2007
Abstract: The Intergovernmental Panel on Climate Change (IPCC)
subgroups are releasing reports this year. Already, the February Summary
for Policymakers has generated intense opposition by industry shills who
are being paid to place anti-IPCC op-ed pieces. This talk will discuss the
major recommendations from the subgroups that will have been released
by July and the enduing controversies.
All of us live on this precious jewel of a planet.
How many of us have not been moved to see the
photographs of Earth from space?
But now there are more than 6.5 billion of
us here, and nearly half of them must live
on under $2 a day.
The poorest people live in a world shaped
by the rich countries.
This talk addresses the Fourth Assessment Report of the
Intergovernmental Panel on Climate Change (IPCC).
Many of you have heard of the IPCC. For those of you who
have not, it is run by the UN and the World Meterological
Organization and is made up of scientific experts who comb
through what is known in the scientific literature and
summarize the findings. Diversity of views is solicited. About
one-third of the scientists in the first assessment participated in
the second, about one-third who were in the second participated
in the third, and so on. Governments (180 members) vote line
by line on the Summaries for Policymakers. (You may have
heard of the resistance of the US and China to these reports,
which do reflect their objections.
Here is an extremely condensed summary of
the results:
1990 First Assessment Report
“The unequivocal detection of the
enhanced greenhouse effect from
observations is not likely for a decade
or more.”
1995 Second Assessment Report
“The balance of evidence suggests a
discernable human influence on global
climate.”
2001 Third Assessment Report
“There is new and stronger evidence that
most of the warming observed over the last
50 years is attributable to human activities.”
2007 Fourth Assessment Report
“Most of the observed increase in globally
averaged temperatures since the mid-20th
century is very likely due to the observed
increase in anthropogenic greenhouse gas
concentrations.”
The entire IPCC report actually
comes from amalgamation of
results from three separate
Working Groups: the scientific
basis (WG1); impacts, adaptation,
and vulnerability (WG2); and
mitigation of climate change
(WG3).
IPCC Special Report on Emission Scenarios
(
SRES)
A1. The A1 storyline and scenario family
describes a future world of very rapid
economic growth, global population that
peaks in mid-century and declines
thereafter, and the rapid introduction of new
and more efficient technologies.
A2. The A2 storyline and scenario family
describes a very heterogeneous world.
The underlying theme is self reliance and
preservation of local identities. Fertility
patterns across regions converge very
slowly, which results in continuously
increasing population. Economic
development is primarily regionally
oriented and per capita economic growth
and technological change more
fragmented and slower than other
storylines.
B1. The B1 storyline and scenario family
describes a convergent world with the
same global population, that peaks in midcentury and declines thereafter, as in the
A1 storyline, but with rapid change in
economic structures toward a service and
information economy, with reductions in
material intensity and the introduction of
clean and resource efficient technologies.
B2. The B2 storyline and scenario family
describes a world in which the emphasis
is on local solutions to economic, social
and environmental sustainability. It is a
world with continuously increasing global
population, at a rate lower than A2,
intermediate levels of economic
development, and less rapid and more
diverse technological change than in the
B1 and A1 storylines.
An illustrative scenario was chosen for each of
the six scenario groups A1B, A1FI, A1T, A2,
B1 and B2. All should be considered equally
sound.
The SRES scenarios do not include additional
climate initiatives, which means that no
scenarios are included that explicitly assume
implementation of the United Nations
Framework Convention on Climate Change or
the emissions targets of the Kyoto Protocol.
One of Tony Auth’s cartoons (published in the The
Philadelphia Inquirer on 10 April 2007) gives a slightly
scary view of the Fourth Assessment Report:
Terminology used by the IPCC
Likelihood of the occurrence / outcome
Virtually certain >99% probability of occurrence
Very likely
90 to 99% probability
Likely
66 to 90% probability
About as likely as not
33 to 66% probability
Unlikely
10 to 33% probability
Very unlikely
1 to 10% probability
Exceptionally unlikely <1% probability
WG1
The global atmospheric concentration of carbon dioxide has increased from a
pre-industrial value of about 280 ppm to 379 ppm in 2005. The atmospheric
concentration of carbon dioxide in 2005 exceeds by far the natural range over
the last 650,000 years (180 to 300 ppm) as determined from ice cores. The
annual carbon dioxide concentration growth rate was larger during the last 10
years (1995–2005 average: 1.9 ppm per year), than it has been since the
beginning of continuous direct atmospheric measurements (1960–2005
average: 1.4 ppm per year) although there is year-to-year variability in
growth rates.
The primary source of the increased atmospheric concentration of carbon
dioxide since the pre-industrial period results from fossil fuel use, with landuse change providing another significant but smaller contribution.
The global atmospheric concentration of methane has increased from a preindustrial value of about 715 ppb to 1732 ppb in the early 1990s, and was
1774 ppb in 2005. The atmospheric concentration of methane in 2005
exceeds by far the natural range of the last 650,000 years (320 to 790
ppb) as determined from ice cores.
The global atmospheric nitrous oxide concentration increased from a preindustrial value of about 270 ppb to 319 ppb in 2005. The growth rate has
been approximately constant since 1980. More than a third of all nitrous
oxide emissions are anthropogenic and are primarily due to agriculture.
The combined radiative forcing due to increases in carbon dioxide,
methane, and nitrous oxide is +2.30 [+2.07 to +2.53] W m–2, and its rate of
increase during the industrial era is very likely to have been unprecedented
in more than 10,000 years.
“Warming of the climate system is
unequivocal, 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.”
“At continental, regional and ocean basin
scales, numerous long-term changes in
climate have been observed. These include
changes in arctic temperatures and ice,
widespread changes in precipitation
amounts, ocean salinity, wind patterns and
aspects of extreme weather including
droughts, heavy precipitation, heat waves
and the intensity of tropical cyclones.”
“Palæoclimatic information supports the
interpretation that the warmth of the last
half century is unusual in at least the
previous 1300 years. The last time the polar
regions were significantly warmer than
present for an extended period (about
125,000 years ago), reductions in polar ice
volume led to 4 to 6 m of sea level rise.”
Temperature reconstructions for the last millennium of M. E. Mann, R. S.
Bradley, and M. K. Hughes, “Global-scale temperature patterns and climate
forcing over the past six centuries,” Nature 392, 779 (1998) and T. J.
Crowley, “Causes of climate change over the past 1000 years,” Science 289,
270 (2000). The zero line is set for the interval from 1961 to 1990.
[Crowley, Figure 1]
Overview of temperature reconstructions for the past two millennia. The
zero line is set for the interval from 1961 to 1990. The shaded area
represents the range of uncertainty in the reconstructions. (Figure 8 from P.
D. Jones and M. E. Mann, “Climate over past millennia,” Rev. Geophys.
42, RG2002 (2004). ©2004 American Geophysical Union.)
“Most
of the observed increase in global
average temperatures since the mid-20th
century is very likely due to the observed
increase in anthropogenic greenhouse gas
concentrations. This is an advance since the TAR’s
conclusion that “most of the observed warming over the last
50 years is likely to have been due to the increase in
greenhouse gas concentrations”. Discernible human
influences now extend to other aspects of climate, including
ocean warming, continental-average temperatures,
temperature extremes and wind patterns.”
“For the next two decades, a warming of about 0.2
°C per decade is projected for a range of SRES
emission scenarios. Even if the concentrations of
all greenhouse gases and aerosols had been kept
constant at year 2000 levels, a further warming of
about 0.1 °C per decade would be expected.”
“There is now higher confidence in projected
patterns of warming and other regional-scale
features, including changes in wind patterns,
precipitation and some aspects of extremes and of
ice.”
“Anthropogenic warming and sea level rise
would continue for centuries due to the time
scales associated with climate processes and
feedbacks, even if greenhouse gas
concentrations were to be stabilized.”
20% - 30% of plants and animals at high
risk of extinction if T ~ 1.5 °C - 2.5 °C
Rank
Year
Top Twenty-Five Annual Global Mean Temperature (°C)
Combined
Year
Land
Year
Ocean
1
1998
14.53
1998
9.48
1998
16.57
2
2005
14.48
2005
9.41
2003
16.54
3
2002
14.46
2002
9.40
2005
16.54
4
2003
14.46
2003
9.35
2004
16.52
5
2004
14.44
2004
9.33
1997
16.51
6
2001
14.41
2001
9.29
2002
16.51
7
1997
14.37
1999
9.22
2001
16.49
8
1990
14.30
1995
9.18
1987
16.41
9
1995
14.30
1990
9.13
1990
16.39
10
1999
14.28
1997
9.12
1995
16.39
11
2000
14.27
2000
9.10
1991
16.38
12
1991
14.24
1994
9.02
2000
16.37
13
1987
14.23
1991
9.00
1944
16.36
14
1988
14.22
1988
8.98
1945
16.35
15
1994
14.21
1983
8.92
1983
16.35
16
1983
14.2
1981
8.91
1996
16.35
17
1996
14.18
1987
8.89
1988
16.34
18
1944
14.14
1996
8.87
1999
16.34
19
1989
14.14
1989
8.85
1994
16.33
20
1993
14.11
1993
8.79
1989
16.29
21
1992
14.1
1938
8.76
1958
16.28
22
1981
14.09
1992
8.75
1992
16.28
23
1958
14.08
1973
8.72
1993
16.28
24
1945
14.06
1980
8.71
1969
16.27
25
1980
14.06
1953
8.70
1941
16.26
WG2
Observational evidence from all continents and
most oceans shows that many natural systems
are being affected by regional climate changes,
particularly temperature increases.
A global assessment of data since 1970 has
shown it is likely that anthropogenic warming
has had a discernible influence on many
physical and biological systems.
Other effects of regional climate changes on
natural and human environments are emerging,
although many are difficult to discern due to
adaptation and non-climatic drivers.
More specific information is now available
across a wide range of systems and sectors
concerning the nature of future impacts,
including for some fields not covered in
previous assessments.
Lake Chad
Magnitudes of impact can now be estimated more
systematically for a range of possible increases in
global average temperature.
Impacts due to altered frequencies and intensities of
extreme weather, climate, and sea level events are
very likely to change.
Some large-scale climate events have the potential to
cause very large impacts, especially after the 21st
century.
Impacts of climate change will vary regionally but,
aggregated and discounted to the present, they are
very likely to impose net annual costs that will
increase over time as global temperatures increase.
Some adaptation is occurring now, to observed and
projected future climate change, but on a limited
basis.
Adaptation will be necessary to address impacts
resulting from the warming which is already
unavoidable due to past emissions.
A wide array of adaptation options is available, but
more extensive adaptation than is currently occurring
is required to reduce vulnerability to future climate
change. There are barriers, limits and costs, but these
are not fully understood.
Vulnerability to climate change can be exacerbated by
the presence of other stresses.
WG3
Adaptation is possible in some areas.
How can emissions be
reduced?
Sector
(Selected) Key mitigation
technologies and practices
currently commercially
available.
Buildings
Efficient lighting; efficient appliances and air conditioning; improved
insulation ; solar heating and cooling; alternatives for fluorinated gases
in insulation and appliances
Transport
More fuel efficient vehicles; hybrid vehicles; biofuels; modal shifts
from road transport to rail and public transport systems; cycling,
walking; land-use planning
Energy Supply
efficiency; fuel switching; nuclear power; renewable (hydropower,
solar, wind, geothermal and bioenergy); combined heat and power; early
applications of CO2 capture and storage
Waste
Landfill methane recovery; waste incineration with energy recovery;
composting; recycling and waste minimization
Forests
Afforestation; reforestation; forest management; reduced deforestation;
use of forestry products for bioenergy
Agriculture
Land management to increase soil carbon storage; restoration of
degraded lands; improved rice cultivation techniques; improved nitrogen
fertilizer application; dedicated energy crops
Industry
More efficient electrical equipment; heat and power recovery; material
recycling; control of non-CO2 gas emissions
What are the macroeconomic
costs in 2030?
Stabilization
levels
(ppm CO2eq)
590-710
535-590
445-535
Median
GDP
reduction
(%)
Range of
GDP
reduction
(%)
0.2
-0.6 – 1.2
0.6
0.2 – 2.5
Not
<3
available
Reduction of
average
annual GDP
growth rates
(percentage
points)
< 0.06
< 0.1
< 0.12
What are the macroeconomic
costs in 2050?
Stabilization
levels
(ppm CO2eq)
Median
GDP
reduction
(%)
Range of
GDP
reduction
(%)
Reduction of
average annual
GDP growth
rates
(percentage
points)
590-710
535-590
0.5
1.3
< 0.05
< 0.1
445-535
Not
available
1–2
slightly
negative
–4
< 5.5
< 0.12
Hadley Centre Climate Model
Results
Hadley Centre Climate Model
Results
Change is coming ...
Can we ameliorate or adapt?
It’s up to us.