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Climate Change: Causes, Impacts & Mitigation Efforts

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Before 2023, CO2 concentration below 300 ppmv;
In 2023: 400 ppmv
1. energy consumption greatly increase after 1950
2. fossil fuel is still the main source of greenhouse gas
Intergovernmental Panel on Climate Change
Scientific concerns about global warming grew during 1980s
• In 1988, the World Meteorological Organization (WMO)
and the United Nations Environment Programme (UNEP)
established IPCC to investigate and report on scientific
evidence on climate change and possible international
responses to climate change
• IPCC‘s first assessment report (in 1990) fed into the drafting
of the United Nations Framework Convention on Climate
Change (UNFCCC) in 1991. 166 nations signed at the Earth
Summit in Rio de Janeiro in 1992 and came to force in 1994.
• An objective of stabilizing the climate to prevent dangerous
anthropogenic interference with the climate system in a
timeframe that allow natural systems to adapt without major
damage to food systems and economic development.
Kyoto Protocol
• In the 1997 Conference of Parties (COP) meeting in Kyoto,
Japan, delegates agreed on Kyoto Protocol
• The protocol required Annex I countries to reduce
emissions but exempted other countries.
• The participants agreed to reduce their CO2 and other GHG
emissions to a level 7% below the 1990 total, with the
agreement to take force during 2008–2012
Copenhagen Summit
• Establish a replacement for the Kyoto Protocol
• Failed its key goal of establishing binding emissions limits
after 2012.
• Adopted a target temperature limit for climate policy
• Countries recognized “the scientific view that the increase
in global temperature should be below 2 degrees Celsius.”
Paris Agreement:
adopted 12 Dec 2015 at COP21, came into force 4 Nov 2016;
ratified 179/197; with Nationally Determined Contributions—
country determine how to meet the emission target; increase
global average temp below 2ºC & pursue efforts to limit temp
increase to 1.5ºC
California
• Ambitious Emissions Targets: California has set rigorous
greenhouse gas (GHG) reduction goals (e.g., aiming for carbon
neutrality by 2045)
• Clean Vehicle Policies: California leads nation in zero
emission vehicle (ZEV) adoption with incentives and mandates
to transition car manufacturers toward EV production.
• Renewable Energy: Renewables Portfolio Standard (RPS)
requires utilities to derive 60% of electricity from renewables
by 2030, aiming for 100% carbon-free power by 2045.
tribal sovereignty.
• Regulatory Stance: State officials often push back on
federal regulations aimed at reducing methane leaks or
emissions from oil and gas operation
European Union
• The EU has generally been a global frontrunner in setting
binding climate targets and implementing legislation to curb
greenhouse gas (GHG) emissions.
• Key initiatives include the European Green Deal, targeting
climate neutrality by 2050, and a series of interim targets (e.g.
reducing net emissions by at least 55% by 2030 compared to
1990 levels.)
•The EU Emissions Trading System (ETS) is one of the world’s
largest carbon markets and a central policy tool
Bodily subsystems: immune systems-->the person-->fam
social groups-->society-->species-->biospecies
South America
• Many South American nations, including Brazil, Chile,
Colombia have submitted NDCs under Paris Agreement.
• Efforts include protecting and managing natural carbon
sinks (Amazon rainforest), transitioning to renewable energies,
and implementing adaptation strategies for agriculture
• Challenges include balancing economic development and
deforestation pressures, as well as political and economic
instability in some regions.
Middle East
• Oil-producing countries in the Gulf Cooperation Council
(GCC), such as Saudi Arabia and the United Arab Emirates,
have begun diversifying their economies with varying degrees
of commitment to renewables, green hydrogen, and other
low-carbon strategies (e.g., Saudi Green Initiative, UAE’s
Net Zero by 2050 pledge).
•Many Middle Eastern countries face water scarcity and
extreme heat, driving adaptation measures. However,
dependence on fossil fuel exports remains a significant
challenge for deep decarbonization
1. Everything is connected to everything else. Systems Think
embraces Loop Structure Thinking
Event oriented thinking: everything is explained by casua
chains of events. Root causes are the events starting the
chains of cause and effects,
Systems thinking: systems behavior emerges from struct
of feedback loops. Root causes are not individual nodes b
forces emerging from particular feedback loops
2. The whole is greater than the sum of the parts
The most critical feature is the interconnections or
relationships, between the elements
Elements involved in wildfires: forest, drought, bark beet
wildfire, climate change, lightening, human activities
Drought:
• Drought conditions reduce the water availability for tre
stressing them and weakening their immune systems.
• A stressed tree is less able to produce sap, which acts a
natural defence against bark beetles.
Bark Beetles & Forest Health:
• In a healthy forest, trees can usually defend themselves
from these beetles by producing sap to push them out.
• However, in times of drought, trees may not have enou
sap to fend off the beetles, leading to higher infestation r
and widespread tree mortality, particularly in conifer fore
• Combination of drought stress and bark beetle infestat
can lead to large-scale tree mortality. When many trees d
creates fuels for wildfire
Climate Change:
• Climate change exacerbates all of these interactions.
• Increased temperatures and altered precipitation patter
can make droughts more frequent and severe
• Create conditions that allow bark beetles to spread eas
1. Faster development 2. Extended range 3. Easier surviv
cold seasons
3.Systems are dynamic and their behavior is emergent
Prescribed fires are used to reduce the accumulation of ris
1. Reducing Fuel Loads: preventing the buildup of large
amounts of flammable material, which fuel more intense f
2. Creating Firebreaks: areas where fuel has already been
removed or burned, making it harder for a wildfire to sprea
3. Reducing Tree Density: create more space between tre
making it more difficult for fires to spread rapidly.
4. Promoting Fire-Resilient Landscapes: help promote m
fire-resilient landscape by encouraging the growth of fire
resistant plants and trees. Healthy, fire-resilient landscape
less likely to burn at high intensity
Higher the resilience, lower the vulnerability
Interconnected negative feedback loops -> system resilien
Planck feedback: relation between radiative energy and te
• Higher temp, emit more energy by radiation
Atmosphere, ocean, land warm up, radiation strengthens a
help avoid accumulation of energy
Higher GDP, higher CO2 emission
North Dakota
• Fracking Boom: The Bakken Formation made North Dakota
a major U.S. oil producer. Hydraulic fracturing (fracking)
operations expanded rapidly.
• Pipeline Infrastructure: The state supports pipelines such as
the Dakota Access Pipeline to transport shale oil, despite legal
challenges and protests related to environmental risks and
China
• China is the world’s largest emitter; but it plans to peak CO₂
emissions before 2030 & achieve carbon neutrality by 2060.
• Investments in renewable energy (solar and wind) are
significant, and China leads the world in total installed
renewable capacity (10 x in 10 yr)
• Policy measures include national carbon trading scheme,
though challenges in transparency, enforcement, and
balancing economic growth with climate goals
Troposphere is most important layer of atmosphere, whe
weather systems exist and 70% of mass of the atmosphe
System is an interconnected set of elements, organized in a
way that achieves sth (a distinct function or purpose) and
produces its own pattern of behaviour over time. Systems can
be ‘nested’ within other systems. We are all made of, part of,
and surrounded by systems.
• Global warming potential: amount of warming one ton of gas
would create relative to one ton of CO2 over a 100-year scale
CO2: 1 (74.4%) CH4: 27-30 (17.3%)
N2O: 273 (6.2%) F gas: 1000-10000 (2.1%)
• Desert Climate: the Mojave Desert (e.g. Palm Springs) have
arid, desert climate, extremely hot summers and cold winters
Due to rain shadow effect
Agriculture
• Agriculture, forestry & other land use (AFOLU): ¼% of GH
Bottom to top & equator to pole drive temperature gradients
• Warm air rise and cold sink, so have convection in the tropics
Electromagnetic spectrum
• increasing frequencies/decreasing energy: radio waves->
microwaves -> infrared -> visible light -> UV -> X rays -> gamma
rays
Energy Budget: global energy flow diagram for Earth system
Unit: W/m²
Oceanic process influence
• carbon cycle (photosynthesis of phytoplankton: bacteria,
protists, most are single cell plants)
e.g. cyanobacteria, dinoflagellates, green algae
• weather (set bottom boundary condition)
•climate change (absorb >90% of the heat)
California Climate
• Mediterranean Climate: Most of coastal California (LA and
San Francisco) Hot, dry summers and mild, wet winters
• Mountain Climate
Sierra Nevada, cold, snowy winter and mild to warm summer
Santa Ana wind: high wind speed, warm temp, low humidity
Climate prediction is hard: scenario + physics uncertainty
Climate scientists compute climate:
1. Need to know the governing equations first, if possible
2. Atmosphere and oceans are divided to small grid cells
(discretization)
3. They need to use approximations for small scale processes
(parameterization)
4. Societal impacts need to be computed to help with
policymaking (integrated assessment model)
e.g. climate impacts, socioeconomic development, energy &
land use, emissions, climate change
Solar and terrestrial radiation
• Earth emit radiation at longer wavelength (5-25 um)
• Sun emits radiation at wavelength less than 2 um
Cause of greenhouse effect: Atmosphere is transparent to
solar radiation. Terrestrial radiation is absorbed and remit in its
upward passage through atmosphere
Why greenhouse gas has greenhouse effects?
• Oxygen and nitrogen absorb energy with tightly packed
wavelengths of around 200 nanometres or less
• CO2 absorb energy at 2000-15000um, overlap with infrared’s
Greenhouse gas concentration
• CO2, CH4 (methane), N2O, Fluorinated gas/synthetic
greenhouse gas/ F-gas (HFCs, PFCs, SF6, NF3)
CO2
• Enter atmosphere through burning fossil fuels, solid waste,
trees, biological material, chemical reaction (produce cement)
• Removed from atmosphere when is absorbed by plants as
part of biological carbon cycle
Other use of fossil fuels
• cement and steel industry generate greenhouse gas
Making things (cement, steel, plastic): 31% Plugging in
(electricity): 27% Growing things (plants, animals): 19%
Transport (plane, truck, cargo ship): 16% Maintaining temp
(heating, warming, refrigeration): 7%
Cement
• CO2 is emitted as a by-product of clinker production, which
CaCo3 is calcinated and converted to Lime (CaO), main
component of cement
• Emitted during cement production by fossil fuel combustion
• World use of cement lead to 8% of global CO2 emission
• Concrete -> timber place pressure on beleaguered forest
Steel
• Emission from iron and steel: 7.2%
• Melt iron at 1700C with oxygen and coke
Transportation
• Global transportation emission: 14% USA emission: 30%
• Growth of transport GHG emission is in developing countries
• Passenger vehicles are responsible for about half
Buildings
• Heating is essential in high latitude regions and seasons when
solar is not reliable
Strategy: electrify what we can, no natural gas water heater
and furnace, develop clean fuels, improve building efficiency
Efficiency strategy: Appliance-based efficiency (increase
efficiency of space, water heating equipment) Design based
efficiency (High performance window, insulation, sealants)
Example: I-village (District cooling strategy, precast facade
modules with thermal insulation, centralised hot water system
with solar thermal, heat pump system,PV panel & BVPI system)
Methane
• Emitted during production & transport of coal, natural gas, oil
• Result from livestock and agricultural practice, land use
• By decay of organic waste in municipal solid waste landfill
Ruminant livestock have microbes in rumen called
methanogens., which produce methane then belched out
Nitrous oxide
Population growth
• Norman Borlaug develop first semi-dwarf wheat, corn, ric
• Yuan Longping develop first hybrid rice varieties
Culprit in AFOLU
• Major GHG are CH4, N2O, 28 and 265 times higher warm
potential than CO2
• Population growth and when ppl is richer, they consume
meat and dairy products
• Enteric fermentation in ruminants produce methane,
contribute to about 2 Gt CO2e
• Animal manure contain nitrous oxide, methane, sulfur,
ammonia, which is 2nd biggest emission
Fertilizer
• Contain nitrogen, phosphorus, potassium
• Population will be 40-50% smaller without fertilizer
• Plants cannot produce nitrogen but absorb anomia in so
• Perihelion (Jan 3) Aphelion (July 4)
• Each Jan, 6.8% more solar radiation than July, max diff: 23%
• Cycle span about 100000 years
Obliquity
• Greater the Earth axial tilt angle, more extreme season
• Larger tilt angle favour deglaciation: higher latitude has larger
solar radiation than equator
• Angle is slowly decreasing
Precession
• As earth rotate, it wobbles slightly upon its rotational axis, due
to tidal forces by gravitational influence of Sun and Moon that
cause Earth bulge at equator
• Axial precession: direction of wobble relative to fixed position
of stars
• Season contrasts extreme in one hemisphere than other
Eon: Hadean (4.54-4 bil), Archean (4-2.5 bil), Proterozoic (2.5
bil-541 mil), Phanerozoic (541 mil-present)
Epoch: Quaternary period = Holocene + Pleistocene
Anthropocene is also a potential new epoch
Deforestation
• 30% of AFOLU come from deforestation
• Bc of carbon sink removal -> emission from plants and soil
• Driven by animal farms and crop growing
• Terrestrial sequestration of CO2 does not work
Eon->Era->Period->Epoch
Proxy data: preserved charactestics of environment that stand
in for direct measurement
Mass Fractionization
Water with heavy isotope evaporate less readily and condense
more readily. The colder, more vapour is removed by
condensation, and the lighter the sample.
O18 can measure past global ice volume. When climate cool
and ice sheet grow, more precipitation in cold region is
enriched in lighter isotopes (O18). Ocean is enriched in O18.
Marine organisms incorporate oxygen from seawater in their
shell. Higher O18 suggest larger global ice volume.
• Puzzle like fit: coastline of South America and Africa
• Fossil Distribution: identical fossils
• Rock & Mountain Distribution: similar rock formation
• Paleoclimate indicator: coal deposit and glacial striation in
tropical or temperate regions
• HK geology is formed by igneous rock from volcanic eruption
Warmer past climate
• High atmospheric CO2: volcanic activity and limited
terrestrial vegetation cause higher greenhouse gas
• Continental configuration: supercontinents influence
oceanic and atmospheric circulation, major landmass near
equator, cause more solar heating and reduce albedo
• Limited polar ice caps: minimal polar ice
Snowball Earth
• Glaciers present near equator at low altitudes
• Deposit produced by a glacier within 10 degrees of equator
• Carbon 13 spikes in ocean sediments, photosynthetic life is
surpassed
• Banded iron deposit is anoxic
Chemical weathering
• Land mass is key in a process
• Rain/snow fall on silicate rock, react and take Co2 out of
atmosphere
• Negative feedback: Hot climate, easier chemical weathering
• During snowball earth, volcanic activity injects CO2 into
atmosphere. When land and ocean covered by ice, no chemical
weathering, Greenhouse effect is so strong that ice begins to
melt. Melting proceeds rapidly.
Milankovitch Cycle
• Link between orbital cycle and glacial-interglacial period
• How ice-albedo, CO2, ocean circulation affect orbital change
• Unknown why glacial cycle shift from 41k to 100k ~ 1mil year
• Assume changes in radiation at 65N latitude & in summer are
most important
• Cold summer (low tilt, North hemisphere summer at
aphelion, moderate eccentricity) favor glaciation
• Obliquity affect insolation in north latitude in summer
Eccentricity
• Pull of gravity from Jupiter & Saturn, vary from circle to
elliptical. So, seasons have diff lengths.
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