What the 2007 Reports of the IPCC mean

Gordon J. Aubrecht, IIOhio 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 mid-century 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 IPCCLikelihood 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

WG1The 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 land-use change providing another significant but smaller contribution.

The global atmospheric concentration of methane has increased from a pre-industrial 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 pre-industrial 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

Top Twenty-Five Annual Global Mean Temperature (°C) Rank Year 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.

WG3Adaptation is possible in some areas.

How can emissions be reduced?

Sector(Selected) Key mitigation technologies and practices currently commercially available.

BuildingsEfficient lighting; efficient appliances and air conditioning; improved insulation ; solar heating and cooling; alternatives for fluorinated gases in insulation and appliances

TransportMore fuel efficient vehicles; hybrid vehicles; biofuels; modal shifts from road transport to rail and public transport systems; cycling, walking; land-use planning

Energy Supplyefficiency; fuel switching; nuclear power; renewable (hydropower, solar, wind, geothermal and bioenergy); combined heat and power; early applications of CO2 capture and storage

WasteLandfill methane recovery; waste incineration with energy recovery; composting; recycling and waste minimization

ForestsAfforestation; reforestation; forest management; reduced deforestation; use of forestry products for bioenergy

AgricultureLand management to increase soil carbon storage; restoration of degraded lands; improved rice cultivation techniques; improved nitrogen fertilizer application; dedicated energy crops

IndustryMore 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 CO2-eq)

Median GDP reduction (%)

Range of GDP reduction (%)

Reduction of average annual GDP growth rates (percentage points)

590-710 0.2 -0.6 – 1.2 < 0.06

535-590 0.6 0.2 – 2.5 < 0.1

445-535 Not available

< 3 < 0.12

What are the macroeconomic costs in 2050?Stabilization

levels

(ppm CO2-eq)

Median GDP reduction (%)

Range of GDP reduction (%)

Reduction of average annual GDP growth rates (percentage points)

590-710 0.5 1 – 2 < 0.05

535-590 1.3 slightly negative

– 4

< 0.1

445-535 Not available

< 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.