Summary

Many scientists from around the world have participated in a project for the United Nations, to work out what the global temperature is likely to be by the end of this century.

The outcomes depend entirely on what we decide to do in the next few decades.

• If we work together locally and globally, the likely temperature increase is +1.1°C to +2.9°C.
• If we don’t do much and just go about our business as usual, the likely temperature increase is +2.4°C to +6.4°C.

In order to work out what kind of action should be taken on global warming, the United Nations Intergovernmental Panel on Climate Change (IPCC), created a forecast on what the climate conditions will be like by the end of the century. This forecast was called the Special Report on Emissions Scenarios (SRES).

It recognised that what happens in the future, depends greatly on what we do now, so six options, or scenarios, were created that takes into account the following:-

• Population growth
• Economic activity
• International co-operation
• The use of carbon energy (coal, gas & oil) or renewable energy sources

Each of the scenarios listed below, look at different choices we can make now:-

A1 : The A1 scenarios are of a world more integrated

• Rapid economic growth
• A global population that reaches 9 billion in 2050 and then gradually declines
• The quick spread of new and efficient technologies
• A convergent world - income and way of life converge between regions. Extensive social and cultural interactions worldwide

There are subsets to the A1 family based on their technological emphasis:

A1FI: An emphasis on fossil-fuels
A1B : A balanced emphasis on all energy sources
A1T : Emphasis on non-fossil energy sources

A2 : The A2 scenarios are of a world more divided

• A world of independently operating, self-reliant nations
• Continuously increasing population
• Regionally oriented economic development
• Slower and more fragmented technological changes and improvements to per captia income

B1 : The B1 scenarios are of a world more integrated, and more ecologically friendly

• Rapid economic growth, but with rapid changes towards a service and information economy
• Population rising to 9 billion in 2050 and then declining
• Reductions in material intensity and the introduction of clean and resource efficient technologies
• An emphasis on global solutions to economic, social and environmental stability

B2 : The B2 scenarios are of a world more divided, but more ecologically friendly

• Continuously increasing population, but at a slower rate than in A2
• Emphasis on local rather than global solutions to economic, social and environmental stability
• Intermediate levels of economic development
• Less rapid and more fragmented technological change than in B1 and A1

The above are summaries for the SRES scenarios, for the exact wording click here.

The report forecast a temperature increase and range for each of the scenarios, as seen in the table below:

TABLE 1: SRES Temperature forecasts

Case	Temperature increase Best estimate to 2100	Temperature increase Likely range to 2100
B1 scenario	+1.8	+1.1 – 2.9
A1T scenario	+2.4	+1.4 – 3.8
B2 scenario	+2.4	+1.4 – 3.8
A1B scenario	+2.8	+1.7 – 4.4
A2 scenario	+3.4	+2.0 – 5.4
A1FI scenario	+4.0	+2.4 – 6.4

On the surface a few degrees warmer doesn’t sound that bad. However, we have already experienced a large number of negative climate effects from only .7 C increase in global warming.

The Australian CSIRO (Commonwealth Scientific and Industrial Research Organisation) did a study of a number of reports on global warming. This study looked at what the authors of each report proposed as a threshold for "dangerous anthropogenic interference".

In English, anthropogenic means caused by human activity. Therefore the table below looks at the levels of temperature and Carbon Dioxide that would be thresholds for dangerous climate change, caused by human activity.

What is disturbing is that the average temperature of these reports for dangerous climate change is a 1.5 C increase. If you look at the table above, even the most optimistic scenario (+1.8 C) is above this threshold.

TABLE 2: Proposed temperature and/or CO2 concentration thresholds for "dangerous anthropogenic interference"

Source	Global Mean Temperature Change (°C) (a)	Atmospheric CO2 Stabilisation Level (ppmv)
Azar and Rodhe (1997) (4)	1.4	375
Climate Options for the Long-Term (2002) (5)	1.5	450
Climate Taskforce (2005) (6)	1.4	400
Environmental Systems Analysis Group (2005) (7)	0.9
European Climate Forum (2004) (8)	1.9 (b)
European Union (1996) (9)	1.4	550
Hansen et al. (2005) (10)	1.0	475
Klimatkommittén (2000) (11)		550
Mastrandrea and Schneider (2004) (12)	2.9 (c)
O’Neill and Oppenheimer (2002) (13)	2.0	450
Rijsberman and Swart (1990) (14)	1.4
Royal Commission on Environmental Pollution (2003) (15)		550
Wissenschaftlicher Beirat der Bundesregierung (1995) (16)	1.3
Wissenschaftlicher Beirat der Bundesregierung (2003) (17)	1.4
Average	1.5	475
Table notes: (a) Relative to 1990, assuming 0.6°C of warming occurred between the industrial revolution and 1990 (b) "Critical limits" estimated as 1.4-2.5°C; midpoint of this range used here (c) Median estimate of the threshold for "dangerous anthropogenic interference"

Cause for Concern

Many politicians in Australia, the United States and around the world are not acting to address the problem of Global Warming seriously. Therefore it is unlikely, that the most optimistic scenario (B1 where the world works together and becomes more ecologically focused) is the one that will turn out.

More likely is the A1B scenario, which has a best estimate of 2.8 C increase in temperature, with a possible maximum of +4.4 C. This is much higher than the 1.5 C increase in temperature suggested as a threshold for dangerous climate change.

The Diagram below shows historical temperature levels for the last 1000 years. Each of the Special Report on Emissions Scenarios (SRES) are shown on the right-hand side, as projections of the temperature into the future.

Added to the diagram is the average proposed level for dangerous climate change and the highest historical temperature level for the last 400,000 years.

Two alarming points to notice about the diagram:-

• All of the Special Report on Emissions Scenarios best estimates for temperature increases cross over the "Danger" level.
• The temperature range for the A1B Scenario, (which seems to be the most likely scenario unless we take more serious action) crosses over the 400,000 year high-point.

The CSIRO study also showed an average of 475 ppmv (parts per million by volume) as a maximum concentration of Carbon Dioxide as a threshold for dangerous climate change.

There are three reasons 475 ppmv is an alarming figure:-

1. 475 ppmv is higher than at any time in the last 400,000 years

The highest Carbon Dioxide levels have reached in the last 400,000 years is 300 ppmv and it only did this once. This can be seen in the graph below, which shows Carbon Dioxide and temperature levels from the Vostok ice core.

2. We are already half-way to 475 ppmv

"Since pre-industrial times (around 1750), carbon dioxide concentrations have increased by just over one third from 280 parts per million (ppm) to 380 ppm today." STERN Part I, p.2

The current level of 380 ppmv is higher than the historical level (280 ppmv) and there is no sign of carbon dioxide output decreasing.

The graph below shows;

(A) The proposed level of dangerous climate change caused by human activity.

(B) The highest level of Carbon Dioxide levels for the last 400,000 years.

(C) The current level of 380 ppmv.

(D) Future projections of Carbon Dioxide in the atmosphere.

3. The projections are much higher than even the threshold for dangerous climate change

"Without action to combat climate change, atmospheric concentrations of greenhouse gases will continue to rise. In a plausible ‘business as usual’ scenario, they will reach 550ppm CO2e by 2035, then increasing at 4½ppm per year and still accelerating." STERN Part III, p.1

"If annual greenhouse gas emissions remained at the current level, concentrations would be more than treble pre-industrial levels by 2100, committing the world to 3 – 10°C warming, based on the latest climate projections." STERN Part I, p.1

The pre-industrial levels were 280 ppmv (see point 3) and three times that is 840 ppmv, which is so high it’s not even on the graph.

There are a number of additional changes in the climate which are not included in most climate models, because their effects are only just beginning to be understood.

The danger is that the because most of the climate models do not include these effects, the current predictions underestimate the speed and severity of Global Warming and the range impacts on the environment, the world economy and all life on this planet.

Release of Methane from Peat Deposits, Wetlands and Thawing Permafrost:

Methane is an important greenhouse gas, because it has a Global Warming Potential (GWP) 21 times higher than carbon dioxide. It also stays in the atmosphere for approximately 12 years, which means that it can accumulate.

“Substantial thawing of permafrost has already begun in some areas; methane emissions have increased by 60% in northern Siberia since the mid-1970s. Studies of the overall scale and timing of future releases are scarce, but initial estimates suggest that methane emissions (currently 15% of all emissions in terms of CO2 equivalent) may increase by around 50% by 2100.” Stern Report, Part I, p.10

Not only is there methane trapped in the melting permafrost, but carbon dioxide as well. One set of estimates suggests that wetlands store equivalent to around 1600 Billion tonnes of carbon dioxide and permafrost soils store a further 1500 Billion tonnes.

"Together these stores comprise more than double the total cumulative emissions from fossil fuel burning so far." "Models suggest that up to 90% of the upper layer of permafrost will thaw by 2100". Stern Report, Part I, p.11

The figure below shows the infrastructure at risk due to permafrost thaw. It gives a good picture of the large area of thawing and how serious it is.

Infrastructure at Risk by 2050 Due to Permafrost Thaw

The map shows hazard potential by risk level for buildings, roads, and other infrastructure due to permafrost thaw by the middle of this century, calculated using the Hadley climate model with the moderate B2 emissions scenario. Hazard potential is partitioned into areas with high, moderate, and low susceptibility to thaw-induced settlement. Areas of stable permafrost, which are not likely to change, are also shown. A zone in the high and moderate risk category extends discontinuously around the Arctic Ocean, indicating high potential for coastal erosion. Also within these bands are population centers (Barrow, Inuvik) and river terminals on the Arctic coast of Russia (Salekhard, Igarka, Dudinka, Tiksi). Transportation and pipeline corridors traverse areas of high hazard potential in northwestern North America.

The area containing the Nadym-Pur-Taz natural gas production complex and associated infrastructure in northwest Siberia also falls in the high-risk category. Large parts of central Siberia, particularly the Sakha Republic (Yakutia), and the Russian Far East show moderate or high hazard potential. Within these areas are several large population centers (Yakutsk, Noril'sk, Vorkuta), an extensive road network, and the Trans-Siberian and Baikal-Amur Mainline Railroads. The Bilibino nuclear power plant and its grid occupy an area of high hazard potential in the Russian Far East.

"The amount of carbon dioxide absorbed by the oceans is likely to weaken in the future through a number of chemical, biological and physical changes. For example, chemical uptake processes may be exhausted, warming surface waters will reduce the rate of absorption and CO2 absorbing organisms are likely to be damaged by ocean acidification."

Stern Report, Part I, p.11