How does the carbon cycle operate to maintain planetary health?
Long-term biogeochemical cycles
Key word:
Biogeochemical
Key word: Carbon stores or sinks
Photosynthesis of cyanobacteria 3 billion years ago
removed CO2 from the atmosphere and added O2 to it.
The present carbon cycle balance came about 290mya
Key word: Movement of carbon between its
forms is the 'carbon pathway'
Largest stores are atmosphere, hydrosphere and lithosphere
Sedimentary carbonate rocks
Limestone rocks formed of
calcium carbonate and marine
creatures / shells / corals
Remains on seabed for long periods of
time --> compacted ooze and
cementation (approx. 100m under
seabed) --> deeper = fewer spaces
Formation of crude oil
Biological degradation --> cementation
(100m) --> diagenesis at 40 degrees --> crude
oil and natural gas (Approx. 2500m)
Geological carbon release
Several geological processes release
carbon into the atmosphere or into
the rock cycle over millions of years
Tectonic forces bring carbon-rich sedimentary
rocks into contact with extreme heat which
causes chemical changes and releases CO2
Key word: Out-gassing
Volcanic activity releases approx. 300 million tonnes of CO2 each year
e.g. Chemical weathering of limestone
Short-term biological processes
Surface and deep ocean waters
Significant fluxes due to respiration and
photosynthesis. Phytoplankton in surface waters
use sunlight to turn carbon into organic matter and
carbon enters the food web via other organisms
that use carbon to make their shells and skeletons
Key term: Biological carbon pump
Starting at the surface, carbon is able to make its way
deeper in the ocean through the food chain
Since colder water has less pressure it can hold more gas e.g.
Southern Ocean around Antarctica is a massive carbon sink
Key word: thermohaline circulation
Southern Ocean accounts for more than 25%
of the ocean-atmosphere exchange
Terrestrial primary producers and soils
Plants absorb CO2 through photosynthesis --> one of
the significant stores and fluxes of carbon
Seasonal pattern: winter CO2 concentrations are generally higher
Despite seasonal differences, PPM of CO2 is
increasing steadily and is currently approx. 402ppm
Earth systems and human activities
The NATURAL greenhouse effect
As the Sun's energy enters the atmosphere, the
clouds reflect some of it back so that only about half
reaches the Earth's surface and lower atmosphere
Short wavelength means the energy is able to pass in and out of the atmosphere
Without greenhouse gases e.g. methane, water vapour we would
have an average global temperature of -6 deg Celsius
Until approx 1750, natural geological and biological
processes controlled greenhouse gases but increasing CO2
has altered fluxes and sinks
Oceanic and terrestrial photosynthesis
Implications of fossil fuel consumption
Chemistry of the atmosphere has been changed by burning of fossil
fuels with CO2 levels at their highest for possibly longer than 800,000 years
Going to be a lag period as between 15 and 40% of CO2 remains in the atmosphere for up to 2000 years
Possible implications for the climate, ecosystems
and hydrological cycle of a 2 degrees temp increase
Flashcards
What are the consequences for people and the environment of our increasing demand for energy?
Energy security
Consumption patterns and energy mix
Energy mix is the proportion of each
primary energy resource in a year on a
national, global or local level
Global energy mix largely dominated by
non-renewables namely crude oil and coal
Switch from fossil fuels to renewable energy is being driven
by developed countries, however the change is slow
Key term: renewable switching
Energy pathways are
hard to break because of
geo-political links
New
technologies
need to be
developed and
improved
Key term: primary energy
Key term: secondary energy
Access to energy resources
The energy mix of a country depends on many factors
Real or perceived needs
of the country
Changing consumption patterns,
perhaps linked to population growth
Cultural and historical
legacies regarding
geopolitical links
Accessability of primary
resources outside the country
Availability of
primary
resources
The financial costs of each energy option
Benefits and problems of supplying
non-renewable energy e.g. crude oil
PROS
Large worldwide
demand --> $$$
Support industry --> jobs
Easy to transport
More money for
public infrastructure
Wealth
Oil money can be invested
in new energy resources
CONS
Increased global warming
Burning --> acid rain
Oil spills e.g. Exxon Valdez
Wars have been fought
Dependency on oil
Finite resource
Middle East
Energy players
World Energy Council
Energy players have three objectives: ensuring
that energy supply meets current and future
demand, ensuring accessible and affordable
energy for all and ensuring efficient use of energy
to move towards lower greenhouse gas emissions
State-owned TNC's such as Gazprom (Russia)
or Saudi Aramco (Saudi Arabia)
CS: State-controlled energy companies
The Organisation
of Petroleum
Exporting
Countries (OPEC)
Fossil fuels and economic development
Energy pathways
Pathways
between
consumers
and producers
may be
complex e.g.
Trans-Alaskan
pipeline across
the tundra
Natural obstacles include vast
distances as well as difficult terrain
CS: Trans-Alaskan pipeline
Political tensions can also affect pathways
E.g. Russian/ Ukraine
disputes, Somalian pirate
activity or South China Sea
Socio-economic reasons
Economic sanctions / embargos e.g. Russian
sanctions for invading Crimea in 2014
Supply and demand
Emerging economies like India
and the other BRIC's are
responsible for increased
energy consumption since 2000
Oil was in slow decline, however,
China recently overtook the USA as
the world's largest importer
In 2014, the EU's energy consumption
fell to its lowest level since 1985
Unconventional fossil fuels
Tar sands
Where: Canada
CS:
Canadian
tar sands
Annotations:
GOOD EXAMPLE OF HOW IT CAN BE DONE RIGHT:
- In Alberta, Canada there are 166 billion barrels of oil in tar sand reserves.
- Production increased from 0.1 million barrels a day in 1980 to 2.3 million barrels in 2014
- 151,000 jobs created
- Regulated by national bodies which set a target of 20% reduction in greenhouse emissions in Alberta by 2017
Oil shale
Where: Colorado, USA
Little commercial
development anywhere
Significant environmental
impacts e.g. releases
greenhouse gases when burnt
Deep-water oil
Where: Gulf of Mexico
63 deep-water
rigs in 2014
compared to 14
rigs in 2010
CS: Deepwater Horizon
Lots of new regulations are in place e.g.
robots that can heal leaks in 45 seconds
Shale gas
Where: USA
Carbon footprint of shale
gas is half of that of coal
Fracking
Possible contamination of
groundwater and surface water
Still a fossil fuel
Alternative energy resources
Renewable and recyclable energy
IPCC said that in order to reduce
enhanced climate change,
renewable energy needs to treble
Wind power
Annotations:
Exponential technology that has seen an incredible plunge in prices
The price of wind power has plunged since 1980 by 30 times.
Wind energy is now the cheapest power you can buy in some places around the world.
New technologies: fraction of time that wind turbines are producing energy is increasing all the time
South Africa has the world's best wind resources offshore and onshore
Offshore wind in the last four years has dropped in half in price
Wind power as a source globally has
grown by 700% in the last decade
Solar energy
Annotations:
In the last 40 years the price of solar power has plunged. In 1977 to buy one Watt of solar power cost about $77. Now it costs $0.30, meaning a 250 times reduction in price.
Solar power around the world has grown by 50 times in the last decade
Prices fall --> tap into new markets --> demand rises --> prices fall
Exponential growth growing at 45% per year with no sign of it slowing yet
Solar energy is increasing very fast (38.2%
in 2014) compared to wind and HEP
South Africa could become a solar superpower
The growth of biofuels
biomass is the term for substances which
have grown from animal or vegetable matter
Europe's largest renewable energy source
Not actually carbon-neutral due to lag period caused
by deforestation (small trees absorb less carbon)
Biofuel is suitable for small-scale rather
than large-scale operations
Future?
The use of biofuels continues to grow slowly,
mainly in the USA, Mexico, Brazil and Argentina
Seen as step
backwards
Agave and hemp plants (super-oily)
Radical technologies
Hydrogen fuel cells
Annotations:
Hydrogen fuel cells
Could replace natural gas for heating or petrol for transport
Only waste product is waterIt is more efficient than petrol engine
Needs to be separated to be in its pure form and this requires a lot of energy and may emit large amounts of greenhouse gases
Not a primary energy source and hydrogen tanks need to be strong enough to withstand impacts
Electric vehicles
Annotations:
The distances an electric car can travel without a recharge are relatively short compared with petrol cars, however this is changing.
Lack of charging points especially in the UK where 19.2% are located in London
Zero carbon emissions and nearly no noise pollution, however some people have complained that they are too quiet and pedestrians fail to hear them coming
Carbon capture
Annotations:
Carbon capture and storage
Collects CO2 emissions from power plants and transports it to a suitable geological structure underground to make sure none of it is released into the atmosphere
Nuclear fusion
How are the carbon and water cycles linked to the global climate system?
Threats to the carbon cycle and water cycle
The growing demand for resources
Between 1990 and 2015 the world
energy use increased by 54% whilst the
population increased 36%
This shows that whilst population increases
energy use, it is economic development and
prosperity that account for most of the demand
Higher population means more food production
--> deforestation --> less carbon absorption
IPCC predicts that in 2013, 24% of
greenhouse gas emissions came from
agriculture and land-use change, such as
biomass burning, deforestation
IPCC recommends that people switch from eating
meat to plants or other meat-substitutes and eating
generally less so that we eat no more than is required
Ocean acidification
As the sea absorbs more CO2 via
ocean-atmosphere exchange the pH has
decreased by 0.1pH (26% more acidic)
Higher acidic concentrations will increase
chemical weathering at the coast especially
where there are limestone rocks
Key term: tipping point
Behaviour patterns of marine organisms
are expected to change -
Annotations:
Phytoplankton and microalgae might benefit from increased photosynthesis and some fish may be less sensitive
Higher acidity may affect the ability of some organisms to build shells and skeletons, creating thinner or smaller shells in molluscs and reducing the size of coral reefs
Despite a rise in the population of
primary producers there will likely be a
decline in ecosystem productivity
Shifting climates
Global weather patterns may be shifting resulting in
permanent changes making the world wetter and drier
CS: Droughts in Amazonia, South America
Annotations:
Drought usually occurs once every ten years in the Amazon
Research by UNEP showed that the trees absorb less CO2 during droughts and it was estimated that the 2005 drought emitted 5 billion tonnes of CO2
In the future, the Amazonian tropical rainforest may cease to be a carbon sink and instead become a carbon source with increasingly frequent wildfires and decomposition
Example of positive feedback
where an increase in CO2 -->
drought --> increase in CO2
Implications for human wellbeing
Increased temperature and evaporation rates
CS: Changes in the Arctic water cycle
Largest global increase in temperature is in the Arctic
Higher temperatures are drying up Arctic ponds
Permafrost thawing rates will increase
Arctic lakes will freeze later, with earlier break-up and thinner ice in winter
Arctic Ocean could be ice-free by 2037 especially as oceans warm
and reduced sea ice will provide increased evaporation and snowfall
Threats to ocean health
Ocean acidification is having a massive
negative impact on marine life and as a
result for humans
The ocean is a huge food supply
Coral reefs becoming smaller and
bleached --> less suitable ecosystems for
marine wildlife --> less food for humans
Bleaching is predicted to
affect half of all coral reefs
by 2050
CS: Great Barrier Reef
Annotations:
If the CO2 levels remain at this current rate of increase, ocean acidity will increase by 150% by 2100.
Coral reefs have important environmental impacts e.g. they are a natural barrier against tropical storms and destructive waves and they protect marine life from predators whilst providing them with a nutrient-rich environment.
The Great Barrier Reef in Australia is the size of Germany and has significant economical benefits: it generates $1.5bn per annum for Australia's economy.
Coral reefs also provide humans with food and in return jobs!
Also a loss of leisure
opportunities e.g. Great Barrier
Reef
Forest loss
Forest fires - 2017 Californian fires
Respiratory issues
2 deaths
19 critically injured
200,000 evacuated
Kuznets Curve
Responses to large-scale carbon release
Natural and human
factors and feedback
mechanisms
In 2014, the IPCC identified 7 possible 'tipping points'
"an abrupt, possibly
irreversible,
large-scale change
over a few decades
or less"
Dieback of boreal forest
Drought stress may lead to the collapse of boreal forest. Arctic
ecosystems are vulnerable to thawing permafrost, shrubs
spreading in the tundra and an increased number of pests as
temperatures rise
Unpredictable over large area
Arctic Ocean free of ice in the summer
Higher air temperatures met sea ice. However, thinner
ice cover may also increase albedo and cooling
This negative feedback is not fully understood
Long-term droughts
Collapse of monsoon climate circulation
More intense precipitation occurs during the
monsoon wet season because of the transport
of more evaporated moisture in warmer air
A sudden collapse is unpredictable
Dieback of tropical rainforest
Forests e.g. Amazonia could change to a less carbon-dense, drought
and fire-adapted ecosystem as a result of longer dry seasons
Unpredictable over large area
Seabed methane release
Methane hydrates could be released as methane gas as a result of global warming
Unlikely
Atlantic thermohaline circulation collapse
Increased volumes of freshwater could
alter thermohaline circulation
Climate models disagree
If emissions were stopped,
some effects of greehouse
gases would immediately be
reduced, however some would
remain for possibly centuries
Around 20% of CO2 could
remain in the atmosphere
for hundreds of years
Adaption strategies
Solar-radiation management
Flood-risk management
Water conservation
In China, water saving irrigation
has been introduced - between
2007 and 2009 China saved up to
11.8% of its previous consumption
Resilient agricultural systems
Land-use planning
Rebalancing the carbon cycle
CS: The Paris Agreement 2015
Annotations:
The Kyoto Protocol of 1997 set out to reduce global CO2 emissions but it wasn't a truly global agreement.
The Paris Agreement of 2015 was signed by 195 countries who all promised to reduce their greenhouse gas emissions to almost zero by 2065. The USA has since pulled out of the agreement under President Trump and this has led to many tensions, with France blocking all trade with the US until they rejoin.
However, there is little force making countries work towards their targets and progress reporting could be tampered with or plainly innaccurate.
Science suggests that the target of limiting temperature rise to 1.5 degrees above pre-industrial levels is unlikely as we have already seen a 1 degree rise in 2016.