A&O SCI 1 Lecture Notes - Lecture 21: Human Enhancement, Ed Markey, Cloud Albedo
8 Jun 2018
School
Department
Course
Professor
Policies Part II
RECALL….
• UNFCCC international treaty was negotiated in Rio in 1992
o Outlines how specific international treaties can be negotiated to set binding limits on gg
emissions
o Paris agreement was adopted unanimmously by members of COP on 12 Dec 2015
o Nov 2016, 193 UNFCCC members signed treaty, 115 have ratified it so far
▪ USA signed 19 oct 2016
o The agreement went into effect on 4 nov 2016
• The Paris Agreement withdrawal
o Article 28 establishes procedure
o Can be done no earlier than 3 years after agreement
▪ Goes into effect 1 year after the notification is received by the depositary
o Alternatively, a country can rescind participation in UNFCC automatically withdrawing from
agreements
▪ However, agreement does not stipulate any consequences or provisions for countries
that do not comply with it
o United States has set verbal notice that it is going to withdrawal…
Paris Agreement outlook
• Even ambitious emissions reductions from Paris pledges are not enough to stay under 2oC
warming target
• Current pledges bring to 3.5oC (-1 from business as usual)
• Much more dramatic reduction in emissions will have to be negotiated (every 5 years) to meet 2oC
o These will have dramatic costs and is not clear whether it is actually feasible w current
technologies
o 1.5oC goal seems already impossible, unless some unforeseen technological development
allows negative emission technologies at a massive scale
Negative Emissions Technologies
Negative emission tech removes carbon from atmosphere to store in other parts of Earth System
• Carbon Capture and Storage is an example (lect 16)
• Other examples include growth of biomass on land to produce energy
o Bioenergy production can be couples to CCS to provide a permanent carbon sink
Different paths to 2oC is possible
• 1 strategy immediately slashes fossil-fuel use while ramping up renewable-energy use
o Implies staying positive emission
• Another strategy continues use of fossil fuels with an increasing share from bioenergy sources
o Carbon from bioenergy is captured and stored, driving emissions below zero
o Implies going negative emissions
______________________________________________________________________________
TECHNOLOGICAL SOLUTIONS
Proposals to counteract anthropogenic cc with other types of human interference in climate system are
known as geoengineering
• Human interventions in local climate have been proposed to adapt to cc, such as painting roofs
white to cool cities
o However, geoengineering generally refers to interventions at the planetary scale
• These proposals have been taken increasingly seriously in recent years, and currently significant
research resources devoted to them
• These schemes can be divided into 2 categories:
o Solar radiation management (albedo modification)
o Carbon Dioxide Removal
1. Solar Radiation Management schemes seek to increase the effective albedo of the planet, so as to
counteract the elvated trapping of terrestrial radiaiton by the enhanced gg effect
A. Artificial Reflection by Aerosols: sulfate particles that are injected into the stratosphere all
over the globe on a continuous basis to produce a negative radiative forcing
B. Cloud albedo enhancement: seeding clouds all over the world with aerosols that could
serve to enhance the number of water droplets in clouds and hence the clouds' albedo
Relatively inexpensive and could be deployed quickly. However, there are some flaws:
o They do nothing to address ocean acidification, since pH of the ocean is determined by
atmospheric CO2 levels
o They must be applied continuously to be effective. If for some reason they were stopped,
there would be a catastrophic abrupt warming, as climate would be subjected to the shock
of entire human enhancement of gg effect all @ once
2. Carbon dioxide Removal schemes seek to remove CO2 from atmosphere
A. Ocean Fertilization: nutrients are added to ocean wher they are naturally scare, to stimulate
phytoplankton blooms, growth of fish population, and enhanced drawdown of carbon to the
deep ocean
B. Carbonate Addition: huge quantities of ground limestone are dumped in ocean to increase
ocean's alkalinity. The reduction in acidity would make CO2 more soluble in sea water, and
accelerate the natural oceanic carbon sink
Do address most cc impacts; however, they share common problems:
o Generally expensive and difficult to bring to scale
▪ Mutual nation agreement is rare
▪ Break international laws
o They have unknown consequences for ecosystems, especially those involving perturbations
to the marine biosphere
Document Summary
Different paths to 2oc is possible: 1 strategy immediately slashes fossil-fuel use while ramping up renewable-energy use. Implies staying positive emission: another strategy continues use of fossil fuels with an increasing share from bioenergy sources, carbon from bioenergy is captured and stored, driving emissions below zero. However, there are some flaws: they do nothing to address ocean acidification, since ph of the ocean is determined by atmospheric co2 levels, they must be applied continuously to be effective. The reduction in acidity would make co2 more soluble in sea water, and accelerate the natural oceanic carbon sink. In early 2015, the nas released two reports on geoengineering, one on solar radiation management and one on carbon dioxide removal. Solar radiation management at climate-altering scales should not be pursued. Solar radiation research should continue, but a governance strucutre should be created to oversee such research.
