4.4 Climate Change

Arguments Against:

Cutting greenhouse emissions may delay economic growth in developing countries, increasing poverty It is difficult to achieve global consensus on action and even harder to police No guarantee that human intervention will be sufficient to alter global climate patterns Restrictions imposed by carbon reduction schemes may prevent the development of beneficial future technologies Carbon reduction schemes will likely result in significant job losses from key industries, requiring retraining of unemployed workers

While greenhouse gases occur naturally, man is increasing greenhouse gas emission via a number of activities, including:

Deforestation - the removal of trees means that less carbon dioxide is removed from the atmosphere via photosynthesis Increased farming / agriculture - this involves land clearing for cattle grazing, also ruminant cattle produce methane

Greenhouse gases absorb and emit long-wave (infrared) radiation, thereby trapping and holding heat within the atmosphere

Greenhouse gases collectively make up less than 1% of the Earth's atmosphere

Many claims have been made regarding the impact of human activities on climate change - not all are supported by evidence

Many arguments are not backed by reliable scientific data or are made by entities with vested interests (e.g. oil companies)

Actions on Climate Change Arguments For:

Risks of inaction are potentially severe (e.g. more droughts, floods, rising sea levels) Higher temperatures will increase the spread of vector-borne diseases Loss of habitat will result in the extinction of some species (loss of biodiversity) Climate changes may affect food production, resulting in famines Climate changes could destroy certain industries which countries rely on (e.g. fishing), leading to poverty These factors would increase economic burdens and competition for resources, creating international tensions

Rising levels of atmospheric carbon dioxide are causing a decrease in the pH of ocean water (ocean acidification)

Since the start of the industrial revolution ocean pH has dropped from ~8.2 to ~8.1 (roughly a 30% increase in acidity) It is predicted that if current conditions continue, oceanic pH could fall to roughly 7.8 by the turn of the century (2100)

The industrial revolution introduced new manufacturing processes which significantly increased mankind's use of fossil fuels

The burning of fossil fuels releases carbon dioxide as a by-product, leading to a steady increase in its atmospheric concentration

Data collected from the Vostok ice core demonstrates that:

There is a strong positive correlation between carbon dioxide concentrations and temperature (↑ CO2 levels ∝ ↑ temperature) There have been fluctuating cycles of CO2 concentrations which appear to correlate with global warm ages and ice ages Current concentrations of CO2 are higher than at any time recorded in the last 400,000 years

The greenhouse gases which have the largest warming effect within the atmosphere are water vapor (clouds) and carbon dioxide

Water vapor is created via evaporation of water bodies (e.g. oceans) and transpiration - it is removed via precipitation (rain) Carbon dioxide is made by cell respiration and burning fossil fuels - it is removed via photosynthesis and absorption by oceans

The precautionary principle is

effectively the reverse of the 'burden of proof', which advocates inaction until cause is proven

Water vapour is the most abundant greenhouse gas in the atmosphere, but

is not produced as a product of human activity

Efforts to reduce a carbon footprint of an individual, household or company usually involves

reducing, reusing and recycling

The water (hydrologic) cycle describes

the continuous movement of water on, above and below the surface of the Earth

A carbon footprint is therefore the sum of all CO2 emissions that were induced by a person's activity within a given timeframe:

All fossil fuel consumption (including petrol, electricity, natural gas) All transportation (besides human-powered activities like walking and cycling) All emissions associated with consumables (e.g. the production of a cheeseburger can result in ~ 3 kg of CO2 emissions)

The decrease in ocean pH is predicted to threaten the survival of marine organisms that require calcium carbonate

An increase in the concentration of H+ ions means there are less free carbonate ions available for calcification Shells and coral exoskeletons are also likely to begin to dissolve when ocean conditions are more acidic Experiments have shown that increasing water acidity correlates with the significant thinning of shells over several weeks Corals, sea urchins and shelled molluscs do not exist in regions with high levels of dissolved CO2 (e.g. near hydrothermal vents)

Greenhouse gases play a pivotal role in determining global temperatures and climate patterns due to their capacity to retain heat

As these gases trap heat, increases in greenhouse gas concentrations should correlate with an increase in global temperature Long term weather patterns (climate) may also be influenced by greenhouse gas concentrations

The oceans are a major carbon sink and absorb roughly a third of all human produced (anthropomorphic) CO2 emissions

CO2 solubility is temperature dependent (more soluble when cooler), so less CO2 will be absorbed as temperatures rise

When oceans absorb atmospheric CO2, some of it will remain dissolved in a gaseous state but most will be chemically modified:

Carbon dioxide will combine with water to form carbonic acid, which dissociates into hydrogen ions and hydrogen carbonate H+ ions will lower the ocean pH (acidification) and will also combine with free carbonate ions to form more hydrogen carbonate With less free carbonate ions in the water, marine organisms are less able to produce calcium carbonate (via calcification) Calcium carbonate is used to form the hard exoskeleton of coral and is also present in the shells of certain molluscs Hence increasing concentrations of dissolved carbon dioxide threatens the viability of coral reefs and certain molluscs

There are many proposed environmental consequences associated with an enhanced greenhouse effect, including:

Disease spread - More temperate climates will increase the prevalence and spread of pathogenic vectors (e.g. mosquitos) Ice caps melting - Higher temperatures are melting ice caps and reducing permafrosts, releasing detritus trapped in ice Extreme weather conditions - Climate change is linked to an increase in extreme weather (e.g. cyclones, tropical storms) Extinction - Changing climate will increase competition, leading to a loss of biodiversity and extinction events Acidification of oceans - Rising atmospheric CO2 levels contribute to an increase in the acidification of oceans Rising sea levels - Global warming is associated with rising sea levels, leading to the displacement of communities Temperature increases - Greenhouse gas emissions are linked to an increase in average global temperatures Habitat destruction - Changing climate conditions will lead to the destruction of habitats and expansion of temperate species

This movement of water involves several different processes, including:

Evaporation - Water is converted to vapor by the sun and transferred from the Earth's surface to the atmosphere Transpiration - Water vapor is released by plants and soil into the atmosphere Condensation - Water vapor is transformed into liquid water droplets in the air (creating clouds and fog) Precipitation - Water vapor in the atmosphere condenses into liquid (rain) or solid (snow) and returns to the Earth Infiltration - The flow of water from the ground surface into the soil Runoff - The variety of ways water moves along the ground Subsurface Flow - The flow of water underground (will eventually drain into oceans or return to the surface via springs)

The link between global temperatures and carbon dioxide concentrations was established by analysing data over a long time period

Ice cores taken from the Vostok station in Antarctica provide evidence of the environmental conditions at the time of freezing The Vostok ice core is one of the longest drilled, reaching back 420,000 years and covering the past four glacial cycles By analyzing the gas bubbles trapped in ice, historical CO2 levels and air temperatures (via oxygen isotopes) can be deduced

The greenhouse effect functions to trap heat within the atmosphere and hence prevent rapid temperature fluctuations

Incoming radiation from the sun is shorter wave radiation (ultraviolet radiation and the visible spectrum) The surface of the Earth absorbs short wave radiation and re-emits it at a longer wavelength (i.e. infra-red / heat) Greenhouse gases absorb and re-radiate this longer wave radiation and hence retain the heat within the atmosphere

A carbon footprint is defined as the total amount of greenhouse gases produced to directly and indirectly support human activity

It is usually expressed in equivalent tons of carbon dioxide (CO2)

An increase in ocean acidification as a result of elevated anthropomorphic CO2 emissions could have several consequences:

The disappearance of coral reefs could result in a loss of shoreline protection and habitat, altering coastal ecosystems The loss in revenue from tourism and food industries is predicted to cost economies upwards of $1 trillion by 2100 Increasing the dissolved CO2 levels in oceans would cause invasive species of algae to flourish (more photosynthesis)

It is argued that the enhanced greenhouse effect requires precautionary measures because:

The global climate is a complex phenomena with many emergent properties that are difficult to predict or control Climatic changes are based on time frames well beyond human lifespans, making it difficult to gather scientific evidence If global warming continues to escalate unchecked, the consequences to mankind as a species are potentially life threatening

The greenhouse effect is a natural process whereby the atmosphere behaves like a greenhouse to trap and retain heat

This ensures the Earth maintains the moderate temperatures needed by organisms to maintain life processes (homeostasis) Without a greenhouse effect, Earth's temperatures would drop significantly at night in the absence of direct sunlight

The precautionary principle states that when a human-induced activity raises

a significant threat of harm to the environment or human health, then precautionary measures should be taken even if there is no scientific consensus regarding cause and effect

There are two factors which determine how much of an the impact a greenhouse gas will have in warming the atmosphere:

1. Ability to absorb long-wave radiation Gases that have a greater capacity to absorb long-wave radiation will have a greater warming impact (per molecule) 2. Concentration within the atmosphere The greater the concentration of a gas, the greater its warming impact will be within the atmosphere The concentration of a gas will be determined by both its rate of release and persistence within the atmosphere

The overall impact of a greenhouse gas will be determined by the combination of both these factors

Methane has a larger capacity to absorb long-wave radiation than carbon dioxide, but is significantly less abundant Water vapor enters the atmosphere rapidly but only remains for short periods, while carbon dioxide persists for years Human activity is increasing the amount of greenhouse gases (except water vapor) and hence increasing their impact

Other greenhouse gases include methane and nitrogen oxides - these have less impact on the overall warming effect

Methane is emitted from waterlogged habitats (like marshes) and landfills - it is also a gaseous waste produced by ruminants Nitrogen oxides are released naturally by certain bacteria and also is emitted in the exhaust by certain vehicles

Scientists predict that increases in greenhouse gas concentrations will lead to an enhanced greenhouse effect, resulting in:

More frequent extreme weather conditions (e.g. heat waves, cyclones, more powerful tropical storms, etc.) Some areas to become more drought affected, while other areas become more prone to periods of heavy rainfall Changes to circulating ocean currents - which may cause longer El Nino (warming) and La Nina (cooling) events

When fuel emissions, atmospheric CO2 concentrations and global temperatures are compared, the following trends are revealed:

There is a strong positive correlation between increasing fossil fuel emissions and rising atmospheric concentrations of CO2 Atmospheric CO2 concentrations have increased ~38% since pre-industrial times (1800: ~ 280 ppm ; 2010: ~ 380 ppm) About 40% of CO2 emissions have remained in the atmosphere, the rest has been absorbed by carbon sinks (mainly oceans) This increase in atmospheric carbon dioxide concentration correlates with an increase in average global temperature While correlation does not equal causation, there is mounting evidence to suggest that CO2 emissions are linked to global temperature changes (although other factors likely also contribute)

The greenhouse gas that is increasing most rapidly in the atmosphere is carbon dioxide and the main cause is combustion

When fossil fuels (e.g. coal, oil, gas) are combusted to release energy, carbon dioxide gas is released as a by-product The increased reliance on fossil fuels following the industrial revolution has resulted in ~38% increase in CO2 levels There are now efforts to reduce our reliance on fossil fuels by exploiting alternative energy sources (e.g. solar power)

According to the precautionary principle, the onus for action falls on those contributing to the enhanced greenhouse effect

This makes action on climate change a global issue - involving governments, industries, communities and the individual