Ana - Lecture 2: Climate Change Flashcards
What is climate and what is climate change?
Climate: Averages of precipitation, temp, humidity, sunshine, wind velocity, phenomena such as fog, frost and hail storms, and other measures of the weather that occurs over a long period in a particular place (usually at least 30 years) -> diff to weather in that it is an average of weather conditions over a certain period.
Anthropogenic climate change is an accelerated change of global climate that can be directly correlated to human activity. This is the reason why some experts are suggesting we have entered a new geological epoch: the anthropocene (officially still in holocene).
Carbon cycle
- Main sinks
- Pressures since Industrial revolution
Main carbon sinks:
- reserves of fossil fuels - carbon stored in forests, vegetation, etc - seas and oceans in the form of carbonates and carbonic acid - sediment below water bodies (mineralisation of decaying organic matter) - the atmosphere
One of the pressures since the industrial revolution is our reliance on fossil fuels. This causes an additional release of greenhouse gases such as CO2 into the atmosphere, increasing the conc of such gases has knock on effects on all the other carbon sinks and fluxes. E.g an increase in the amount of atmospheric CO2 conc increases the amount of CO2 dissolved in oceans, increasing the the conc of carbonic acid and hence increasing the oceanic pH. Another example is that by increasing atmospheric greenhouse gases conc, the Earth’s natural radiative balance is perturbed. More IR radiation reflected from the Earth’s surface is absorbed in the atmosphere and therefore average temperatures will increase which, depending on climatic conditions, might increase the rate of vegetation growth or might further accentuate drought conditions leading to desertification.
Earth’s radiation balance
341 W/m^2 average solar radiation flux incident on outer atmosphere. Approx 50% of this is absorbed by Earth’s surface which is partly re-radiated at longer wavelength. Some of this is absorbed by gases in the atmosphere and re-radiated back to Earth (greenhouse effect). The surface temp is largely determined by the amount of radiation captured by these gases. Particulates in the atmosphere have a cooling effect by reflecting away sunlight (volcanic dust, sulfate aerosols, clouds). More UV to surface due to ozone depletion contributes to increase in amount of radiation reaching Earth’s surface. Atmospheric compositions, land reflectivity, solar output, geographical conditions all variables.
The greenhouse effect
Atmospheric gases
Absorption and re-emission of IR radiation by certain molecules (H2O, CO2, CH4 etc). IR absorption happens via bond distortion (stretching, bending, twisting)
O2, N2 and noble gases do not absorb IR. Water vapour is one of the compounds responsible for absorbing much of the energy reflected back to Earth as it is able to absorb IR radiation in a very large spectrum. Oxygen and ozone are able to absorb radiation in the UV spec.
H2O: natural, changes w climate
CO2: natural, burning fossil fuels
CFCs: propellants, refrigerants
CH4: bio-decay (sewage, landfill, cows)
N2O: burning fossil fuels, fertilisers
Radiative forcing
A measure of the influence that a factor has in altering the balance of incoming and outgoing energy in the Earth’s atmosphere system and is an index of the importance of the factor as a potential climate change mechanism. Positive forcing tends to warm the surface, whilst negative forcing cools it.
Global warming potential
The relative radiative forcing resulting from a unit mass emission of a greenhouse gas over a time period compared to a reference compound (CO2). High GWP: - low conc - broad IR absorption bands - long atmospheric lifetime (CFCs) Low GWP: - atmosphere is already saturated - little IR absorption - short atmospheric lifetime Difficult to apply to gases that are very unevenly distributed in the stratosphere, difficult to apply to short-lived gases. Still best metric that is used in decision making and predicting climate change scenarios.
Main cause of climate change
Increase in cumulative total anthropogenic emissions of CO2 since the industrial revolution (1820-1870), which has led to an increase in the global atmospheric conc of CO2.
Effects of climate change
Main effect is global average surface temp change. Some countries might suffer higher temp increase than others depending on their geographical and climatic conditions. Other effects include: sea-level rise due to melting ice and water expansion, flooding, local climatic changes affecting flora (e.g arable crops) and fauna (e.g animal habitats, extreme and unpredictable weather, ocean acidification.
IPCC
Inter-governmental panel on climate change. Is the greatest entity driving climate change research and action. Est in 1988 by UNEP and world meteorological organisation (WMO).
Aims:
- scientific info - human-induced climate change impacts - options for adaptation and mitigation
Global policy cooperations
- UN framework convention on climate change (UNFCCC) 1992: stipulates the common agreement to stabilise greenhouse gas emissions to 1990 levels by 2000. This is the framework under which 195 countries can then discuss and decide or not to join the international treaty called the Kyoto Protocol. UNFCCC meets yearly since 1995 in an event called the conference of parties (COP). Countries might join the UNFCCC and then decide not to ratify the protocol (e.g US). Kyoto Protocol (1997): entered into force in 2005, places a heavier burden on developed nations under the principle of 'common but differentiated responsibilities'. Its first commitment period had the goal to lower overall emissions from 6 greenhouse gases - CO2, methane, nitrous oxide, sulfur hexafluroide, HCFs, and PFCs - calculated as an average over the five year period of 2008-2012. The protocol sets diff targets for diff countries depending on their economic and industrial capabilities. These targets are binding under international law. 2012: Doha amendment: for a period of 2013-2020, parties committed to reducing their GHG emissions by at least 18% below 1990 levels. However, the list of the parties for the Doha amendment is much lower than the initial group of parties of the Kyoto protocol. A greater consensus has been reached around the Paris agreement 2015 - a more flexible and voluntary agreement where more than 160 countries have agreed to limit the temp increase to well below 2 degrees and possibly within 1.5 degrees.
EU policy cooperations
2020 climate and energy package and 2030 climate and energy framework is a set of binding legislation to ensure the EU meets its climate and and energy targets for the year 2020. Sets out three key targets:
- 20% cut in greenhouse gas emissions from 1990 levels
- 20% of EU energy from renewables
- 20% improvement in energy efficiency
UK policy
Climate change Act provides a target of reducing by 2050 80% of greenhouse gas emissions in comparison to levels in 1990.
Climate change mitigation
Refers to any activity that can lead to overall reduction of the causes of climate change i.e greenhouse gas atmospheric concentrations. This can mean reducing the emissions or finding solutions to (re-) capture GHGs. Mitigation examples are promoting renewable energies, making older equipment more energy efficient, or changing management practices or consumer behaviours.
- energy efficiency
- decarbonisation: renewable energy
- stabilising or even increasing carbon sinks (re-forestation)
- carbon capture and storage
Carbon capture and storage
The injection of supercritical CO2 into deep saline formations. It has the potential to reduce CO2 emissions at the scale of ten of MtCO2Pa (megaton CO2 per annum) per project. UK has included CCS as part of its strategy to reduce emissions and meet targets in the Climate Change Act (White Rose and Peterhead CCS projects). However, since Nov 2015, the gov has reduced its investments in CCS.
Norway has one of the largest and most successful CCS projects: the Sleipner offshore (16 Mt Pa)
- below 800 m
- <1% release in 100 years
- sandstone (or limestone) capped by cap rock
- porosity and permeability
- extensive characterisation and monitoring plan
Climate change adaptation
Adaptation measures are as important as mitigation measure (equal financial investment). This is recognised by governments and IPCC and special funds are being made available, including via the Paris agreement or Kyoto Protocol to fund adaptation measures.
- Urban planning
- flood/draught prevention
- rainwater collection
- extreme weather events
- agriculture and forestry planning
