ADPA March 2007

Global Warming 2007

With secondary data taken mostly

from the IPCC report February 2007

ADPA March 2007

Contents

The Greenhouse Effect

The Enhanced Greenhouse

Empirical Evidence

Deduction

Summary of Temperature Records

Greenhouse Gases

Models and Feedbacks

Predictions

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The Greenhouse EffectThe concept of the global greenhouse effect

was proposed in 1824 by Joseph Fourier.

It is a natural phenomenon associated with the various green house gases (GHGs) in the atmosphere, that trap heat radiation emitted from the planet.

Carbon Dioxide, Methane and Water Vapour are all naturally occuring GHGs that help to keep the planet around 17 degrees warmer than without.

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Enhanced Greenhouse EffectHuman activities release additional greenhouse

gases into the atmosphere – anthropogenic source. It seems likely that this will increase the power of the greenhouse – in other words cause an “Enhanced Greenhouse Effect”.

This idea is not particularly new either first proposed by British physicist John Tyndall in 1859. In the 1880’s Swedish physicist Svante Arrhenius predicted that a doubling of Carbon Dioxide would lead to a global temperature rise of 5 degrees Celsius.

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Empirical Evidence

There is plenty of good empirical evidence for all of the following.

Anthropogenic GHG emissions have increased and continue to increase.

Due to the warming GHG emissions are increasing from a number of sources

Temperatures are rising rapidly.

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Deduction and Debate

It is a matter of scientific deduction as to whether anthropogenic emissions are causing global warming, and consequently it is an area of debate amongst scientists and politicians.

The IPCC report stated: “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.”

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Is the word getting hotter?

Evidence from historical records back over the last 100 years and from ice cores that record temperature

over the last 650,000 years (four glacial/interglacial cycles) show that we are currently experiencing a

hotter average temperature.

Eleven of the last twelve years (1995 -2006) rank among the 12 warmest years in the instrumental record of global surface temperature (since 1850).

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Historical Records

Line – Decade Average

Circles – Yearly

Shaded Area – Margins of Uncertainty

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Ice Core Data

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Foramiferan Indicator Species Data

This figure shows the climate record of Lisiecki and Raymo (2005) [1] constructed by combining measurements from 57 globally distributed deep sea sediment cores. The measured quantity is oxygen isotope fractionation in benthic foraminifera, which serves as a proxy for the

total global mass of glacial ice sheets.

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Models

Climate Scientists use complex computer models to generate predictions on warming.

One complication are the large number of both positive and negative feedbacks in that influence climate.

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Negative Feedbacks

Feedbacks in the global ecosystem can be negative, leading to a controling effect and an amelioration of warming. For example the warming is predicted to increase precipitation in polar areas as snow, increasing albedo (reflectivity of surface) leading to a cooling effect.

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Positive Feebacks

There are many positive feedbacks that may increase warming, possibly resulting in a runaway greenhouse.

For example the solubility of Carbon Dioxide in sea water decreases with increasing temperature leading more to be released and further increasing the temperatures.

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Feedbacks – are these positive or negative?1. Thawing of permafrost leads to a release of methane from

waterlogged soils.2. Rate of photosynthesis in plants increases more carbon

dioxide is therefore removed from the atmosphere.3. Ice cover melts, exposing soil or water and albedo decreases4. Increased evaporation produces more clouds increase

tropospheric albedo, reflecting more light away from Earth5. As Earth warms, organic matter in soil is decomposed faster

more carbon dioxide is released

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Runaway Greenhouse Effect

This has been a suggestion since the earlier work of the IPCC. Scientists such as Steven Schneider hypothesised that we may pass a tipping point when positive feedbacks in the greenhouse effect become more powerful than the negative. This would lead to an accelerating warming and could give the Earth a Venusian climate system on a short time scale.

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Summary of GHG Changes Global atmospheric concentrations of carbon dioxide,

methane and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years.

Direct measurements of carbon dioxide since the 1960’s at Mauna Loa in Hawaii show a steady increase to the present day.

The global increases in carbon dioxide concentration are due primarily to fossil fuel use and land-use change, while those of methane and nitrous oxide are primarily due to agriculture.

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GHG Sources, Warming Potential and Significance

Gases and Source Significance

Carbon Dioxide from any combustion, decomposition or respiration.

No. 1 cause of Global Warming GW Potential 1, Atmospheric

concentration – 360ppm and increasing rapidly

Methane from anaerobic respiration and decomposition in rice fields swamps. Landfill sites and flatulent cows.

No. 2 cause of Global WarmingGW Potential 21, atmospheric

concentration - 1.72ppm – major stores under arctic permafrost.

Nitrogen Oxides formed from atmospheric nitrogen in the internal combustion engines.

No. 3 cause, GW Potential = 206.Atmospheric concentration= 0.31

Chlorofluorocarbons (CFCs) from fridge coolants and aerosol cans.

Most potent greenhouse gas per molecule GWP = 3500-7000 times carbon dioxide, but due to low levels less significant than the other gases. Also depletes ozone in stratosphere

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Carbon Dioxide - The Last 10,000 years

Measurements are shown from ice cores (symbols with different colours for different studies) and atmospheric samples

(red lines).

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Mauna Loa Carbon Dioxide Measurements

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Methane the Last 10,000 years

Measurements are shown from ice cores (symbols with different colours for different studies) and atmospheric samples

(red lines).

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Nitrous Oxide the Last 10,000 years

Measurements are shown from ice cores (symbols with different colours for different studies) and atmospheric samples

(red lines).

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Carbon Dioxide

Carbon dioxide is the most important anthropogenic greenhouse gas. 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 carbondioxide 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.

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Predictions

The following slides show a series of graphs and maps that predict climate change against a number of scenarios described in the slides at the end of the presentation.

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IPCC Scenarios

A1

A1B

A2

B1

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Predicted Warming against the IPCC ScenariosB1A1T B2 A1B A2A1F1

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Isotherm Maps of Predicted Warming

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The Emission Scenarios of the IPCC Sp ecial Report on Emission Scenarios

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.

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A1 Family of Scenarios

The A1 scenario family develops into three groups that describe alternative directions of technological change in the energy system. The three A1 groups are distinguished by their technological emphasis: fossil intensive (A1FI), non-fossil energy sources (A1T), or a balance across all sources (A1B) (where balanced is defined as not relying too heavily on one particular energy source, on the assumption that similar improvement rates apply to all energy supply and end use technologies).

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A1

A1 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.

Major underlying themes are convergence among regions, capacity building and increased cultural and social interactions, with a substantial reduction in regional differences in per capita income.

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2A . The A2 storyline and scenario family describes a ver

y 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.

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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. The emphasis is on global solutions to economic, social and environmental sustainability, including improved equity, but without additional climate initiatives.

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2B The B2 storyline and scenario family describes a wo

rld 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. While the scenario is also oriented towards environmental protection and social equity, it focuses on local and regional levels.

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The Consequences of Global Warming Cause biomes to shift their distribution patterns

(How could this occur with fragmented, isolated habitats moving across urban areas, agricultural systems, transport networks? Could it happen at the speeds of temperature change given?)

Change the location of crop growing areas (what would be the geopolitical consequences of this?)

Change Weather Patterns (Cyclones increase in frequency and intensity)

Cause Coastal Flooding ( Predicted sea level rise would swamp low-lying areas)

Cause a change in the distribution of diseases limited by temperature (Such as Malaria)

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Further Reading

http://www.ipcc.ch/

http://www.unep.org/

http://www.climatecrisis.net/

www.funnyweather.org