Climate Change Economics Berkeley C176

Previous IPCC on equilibirum climate sensitivity (ECS)**

"High confidence that ECS is extremely unlikely to be less than 1C and medium confine that ECS is likely to be between 1.5-4.5 C and very unlikely greater than 6" ar5 "Most likely value of about 3 degrees c" AR4 Have been able to narrow down more Hard to rule out extremely large numbers

ON EXAM OFFICIAL LATEST IPCC WORD on equilibirum climate sensitivity (ECS)

"The AR6 best estimates of ECS is 3 degrees C, the likely range is 2.5-4 C and the very likely range is 2-5 degrees and altogether it is virtually certain that ECS is larger than 1.5 C, but currently is not possible to rule out ECS values above 5C"

IPCC transient climate sensitivity **numbers on exam**

"The best estimate of TCR is 1.8 degrees C, the likely range is 1.4-2.2 c AND THE VERY LIKELY RANGE IS 1.2-2.4 c. there is high level of agreement among the different lines of evidence" AR6

transient climate sensitivity

"The surface temperature response for the hypothetical scenario in which co2 increases at 1% yr^-1 from pre-industrial to the time of a double of atmospheric CO2 concentration" increasing 1% per year implies doubling of co2 by 70 years transient climate sensitivity is more relevant for policy implications than equilibrium climate sensitivity correlation between ocean heat up-take and climate sensitivity 1.2-1.4 C

converting co2 and C

co2=1 carbon, 2 oxygen atmomic mass=44 (carbon=12, oxygen=16) 1 ton co2 = 12/44 tons c

watts

flow unit of energy per unit of time How much energy is flowing per unit of time onto the earth

Electromagnetic waves

Energy is transported by electromagnetic radiation, can happen at different wavelengths Different wavelengths have different characteristics important for the climate problem Correspond to radiation, one type is just light (visable), ultraviolet, x-ray, gamma ray etc, infrared, microwave, radio, etc.. infrared=heat, visible=light Transport energy through space (temperature of objects at which this radiation is the most intense wavelenght emitted aka sun super hot more energy?) (sun emits wavelengths has light and different frequency bands of energy can penetrate earths atmosphere or not)

Paris Agreement (2015)

Agreement made between the United Nations countries to cut down on the emissions of greenhouse gases in an attempt to slow down global warming. More wealthy and producing countries have to cut down more agreed on tmperature targets aim for 1.5 otherwise 2 no more annex 1 countries, everyone covered no agreed binding emission targets and instead each country is required to put forward their best efforts

projections

Anything going forward: like bout future temperature, like global average temperature at the end of this century models can only do a conditional prediction (you have to first make predictions about emissions to make predictions about temp) IPCC and natural scienitists very hesitant about making emissions predictions so IPCC moved to scenario approach

SRES B2

B scenarios are more wishful thinking not taken seriously in analyist world world more divided but more ecologically friendly Continuously increasing population, but at a slower rate than A2 Emphasis on local rather than global solutions to economic, social and environmental stability Intermediate levels of economic development Less rapid and more fragmented technological change than in A1 and B1

SRES B1

B scenarios are more wishful thinking not taken seriously in analyist world world more integrated and more ecoogically friendly Rapid economic growth as in A1, but with rapid changes towards a service and information economy Population rising to 9 billion in 2050 and then declining as in A1 Reductions in material intensity and the introduction of clean and resource efficient technologies An emphasis on global solution to economic, social and environmental stability

albedo

fraction of light that a surface reflects Albedo estimates for different earth covers Percentage of incomihng energy reflected back to space Snow can reflect more than 80% back, water can reflect less than 10%, some never hits earth surface because it reflected by clouds Deforestation play major role in albedo and reflectiveness of earths surface

co2 historic observations

ice cores dating back 750,000 years learn about emperature, precipitation, atmospheric conditions, volcanci activity, wind patterns trees (only works in places with seasons since trees grow then so tropics can't measure those trees) (so can only learn about summer temperatures co2 and methane both increasing around 100k years back when civilization started to take off last 150 craziness changes in northern hemipshere sea level and snow coverage starting 150 years back very clear relationship in observations of historic temperatures

impulse response function

measures what happens if you put one unit of a certain gas in the atmosphere and measure what happens over time to that one unit of gas co2 has initial drop, but after 300 years still up a lot while methane atmospheric lifecycle is only 50 years, after 12 years 1/2 gone important for policy implications since methane 10x more potent

SRES A2

more divided world A world of independently operating, self-reliant nations Continually increasing population 15 billion by end of centruy (big increase from today) Regionally oriented economic development

SRES A1

more integrated world Rapid economic growth A global population that reaches 9 billion in 2050 and then gradually declines The quick spread of new and efficient technologies A convergent world Income and way of life converge between regions Extensive social and cultural interactions worldwide big assumption about income growth saying average world gdp will be $70,000 in 2005 dollars by the end of century

SRES Summary

never meant to serve for cba of climate policy (but US gov did and treated each of having same likely proability, which is not what scenarios and major problem with this) we want probalistic forcasts so we can do cba (scenarios only show plausible outcomes) need probailistic forecast then for GDP, population, etc...

energy properties

oject absoribng some energy must emit that same energy out Doesn't have to emit at the same wavelenghts frequency tho, but the two energy flows have to be the same quantity

IPCC scenarios

side project report of emission sceario reports each scenario characterizes different quanities that are important for climate change all are BAU--no explicit climate policy enacted, just reflects population, economic growth, technology, but not climate policy all scenarios have same radiative forcings but give out different temeratures

earth surface cover

Different types of surface covers on earth have different types of reflective properties for light Think arctic with snowcover = super reflective, water/soil dark wet/forest absorbs a lot

ghg effect

makes earth habitable and traps heat inside the atmsophere

Assessment reports IPCC

4 total important and compromised of 3 distinct major reports and a synthesis report. Working group 1: Climate Change 2021: The Physical Science Basis (Natural scientists are working group 1, ⅔ rely on insights from working group 1). WG 2: Climate Change 2022: Impacts, Adaption and Vulnerability (Studies what will it cause, what are the effects on agricultural, sea level rise, how societies can adapt, etc.). WG 3: Climate Change 2022: Mitigation of Climate Change (Where do emissions come from, economic activities that lead to emissions, assessment and trends of emissions, cost and options of reducing emissions). AR6 Synthesis Report: Climate Change 2023 (More digestible for policy makers)

IPCC Publications

Assessment Reports" that are published at regular intervals, most recent 6th edition,.A variety of other publications Special reports on specific topics: metholdolgoy reports, technical papers, upporting papers, main outcome are the assessment reports

How do we estimate the climate sensitivity

Diagnosed from large climate models (Use large computer models that simulates the basic laws of physics (eg thermodynamic). Run model with doubling of co2 concentrations => see what temperature does in the model => climate sensitivity. Lots of models from chemistry, earth system models, etc.. Problem is that they are very slow to run these models. Typical run just once can take months on super computers. Can't get sense of uncertainty since takes months to run. Not very useful trying ot figure PDF for climate sensitivity might be Fit simple models to observations (We fit the model by calibrating the climate system parameter. Very simple models. Simple model => compare model output with historic observations => tweak parameter => parameter: climate sensitivity => simple model. Can run in split second on normal laptop. Thus can run many times and much better at quantifying uncertainties because you can rerun them with different parameters. Can run and rerun to figure otu PDF Run simple models millions and millions of times tweaking the parameter values each time and how this matches are our observation => give more weight to parameter computations that match historical data better

Percentage contribution to greenhouse effect by gas

Different gases have different levels of heat trapping 26% co2, 4,4% methane, 8% ozon, water vapor/couds 60%, n20 1.5% Don't directly control ozon, but humans still changing it. Humans control n20 directly too

Earth Roundness and Climate Change Science

Earth is round important, if flat then radiation would be much higher We are a rotating sphere Some parts of sphere not facing the sun all the time Flat disk= 1368 w/m^2 verses 342 as a sphsere Incoming enery we receive from the sun ^

History/Impact IPCC

Founded in 1988 by UNEP and WMO The main authoritative source on climate change science research, wildly accepted => huge success Published 6 major assessment reports (FAR 1990, SAR 1995, TAR 2001, AR4 2007, AR5 2013/4, AR6 2022/3) Established themselves as the voice of what is the state of climate research Won noble peace for their work in 2007 Input into pretty much any and all climate policy discussions Economics not seen as part of consevation in 1990s, but economics have found other ways into the policy making process besides the IPC

IPCC Representative Concentration Pathways (RCP)

different radiative forcing scenarios for SRES before used to use BAU now don't look like BAU in any shape or form named by the radiative forcing they hit at the end of the century and characetized by radiative forcing they correspond with RCP 8.5 hits 8.5 W/m^2 at the end of the century A2 is basically RCP 8.5 Biggest change is the low emission scarios and they con't correspond to SRES scenarios

Earth Incoming Solar Radiation

Incoming shortwave solar radiation (light) 342 => reflected by atmosphere, clouds and aerosols 77 watts => reflected by surface 30 watts => 67 absorbed by atmosphere => 168 absorbed by surface Thinking about two different objects absorbing energy: atmosphere and earth surface Some radiation never makes it earth surface since reflected by atmosphere or absorbed by the atmosphere 168 radiated by surface => radiated into the atmosphere => outgoing longwave radiation from surface 492 radiated by surface => 452 radiated into the atmosphere => outgoing longwave radiation from surface 40 => outgoing longwave radiation from atmosphere and clouds 195 Greenouse effect 324 back radiation from atmosphere absorbed by surface Radiating some back as heat to the surface then energy balance has to balance this out Total absorbed by earth is 168 + 324 = 492 (incoming energy absorbed by earth) Total outgoing is 492 radiated by surface Atmosphere in balance: 67 absorbed by incoming solar radiation, and 452 radiated into the atmoshere = radiates 195 into space and greenhouse effect radiates 324 back into earth 67+452=324+195

relationship co2 and radiative forcing

Increase co2 => increase radiative forcing (but not linear relationship) radiative forcing => temp change (radiative forcing has no impact on our lives while temperature does)

4 most important feedbacks as temperature increases

Increased water vapor 1.8 w/m^2 Less snow and ice 0.26 w/m^2 Change in cloudiness 0.7 w/m^2 Change in vertical temperature profile -0.84 w/m^2

IPCC

Intergovernmental panel on climate change is the UN body for assessing the science related to climate change

UNFCCC (United Nations Framework Convention on Climate Change)

International environmental tratly from 1992 (after first IPPCC assessment report) entered affect 1994 when enough countries signed by 2015 197 parties basically the whole world signed GOAL: "Stablize ghg concentrations in the atmosphere at a level that would rprvent dangerous antrhopogenci inteference with the climate system" Framework under which almost all international climate policy ever since has happened Created after IPCC report was created Common by differentiated responsabilities (developed countris should take the lead and have better ability to create change) annex 1 (developed countries, 43, industralized, 14 economices in transition (aka fomrer soviet union) non-annex 1: low-income developing countries, rest of world results: everyone agrees on problem, but doesn't set limits or how much should be reduced by who, no enforecment mechanisms, established a process and sturcture for future meetings

kaya identity

Kaya Identity Emissions = pop*(income/population)*(energy/income)*(emessions/energy) (income/population)=per capita income (energy/incom)=energy intensity (emissions/carbon itnesity)=carbon intensity

primary sources of methane and regulation challenges

Livestock, rice cultivation, landfils/waste in general, fossil fuels (natural gas is methane and comes out in leaks) hard to regulate since comes from every individual cow, landfill, rice field, etc... so much more disperse and doesn't go through central bottlenecks like co2 methane emissions are spread out while co2 molecules pass through a few easy regulatable points permfrost has large reserves of methane and scientists worried about that when they melt its released into the atmosphere and would be big problem for increasing feedback lops more varied and complicated story than co2 since react in atmsophere and turn into different compounds

atmospheric composition

Major gases for dry air by share of mass: Nitrogen 78%, Oxygen 21%, Argon 1%, Trace gases 0.4% (Hydrgeen, neon, helium, methane, krypton, carbon dioxide) co2= 0.038% in atmosphere so small, but has huge effect on our atmosphere Nitrogen and oxygen do not contribute to greenhouse effect Heat trapping gases are the trace gases: Methane, co2, and others Wet air, water vapor is about 0.25% and it is a heat trapping element in the atmosphere. Water vapor important contrbiuter for this greenhouse effect

methane

Methane reacts in the atmosphere, it doesn't stay as one individual methane molecule. It chemcialy reacts with the chemicals in the atmsopehre => very different type of cycle High level takeaway is its harder to regulate methane emissions than co2 (reality of how methane emissions are produced) burning biomass important cause--wildfires, changes in landcover indirectly cuased by human activity

emissions verses concenrations

emissions more difficult since gases have different atmospheric lifetimes and gases have different radiative forcings solution: pick a time T, look at the ratio of cummulative radiativing forcing caused by non-co2 gas during that tiem tothe cumulative radiative forcing by co2 over that time

radiative forcing

Positive forcing=more energy is coming out than in Negative forcing=more energy is leaving the earth's atmosphere than is coming in Disturbance of energy balance "Radiative forcing is what happens when the amount of energy that enters the Earth's atmosphere is different from the amount of energy that leaves it" MIT Climate Portal

cooling effects

Reflect energy back into space Like albedo, more reflective => less energy for earth to observe Ice+snow, barren land, volcanic eruptions (spits out lots of aersols will blanket sky over volcano and less sunlight can get through), fores fires (biomass burning) => pump out a lot of aerosols and block out sunlight => relative cooling dessert/dust from sand storm When burning coal/oil pumping suflate (aersols) into atmosphere and have reflective properties => redaitvie forcing (thus Cleaning up suflates from dirty coal plants => less reflective shield) Cooling factors: white upper side of clouds, volcanic eruptions, biomass burning (forest fires), desserts and dust from sandstroms, burning of coal and oil, barren lands, ice and snow

Frequentists probability

Relative frequency of occurrence Not talking about this one doesn't fit as well int othe climate picture, this is what is in traditional state classes, like likelihood of a die

transient climate response

Temperature change at the of co2 doubling Response on shorter time scales, before the deep oceans have had time to equilibrate (more relevant for changes we will see in 21st century smaller response than equlibirum, due to uncertitanity

SRES (socio-economic emission scenarios)

Socio-economic and emissions scenarios developed jointly Population, economy, technology, energy, land-use, agriculture 5 different aspects for different regions of the world over time Set of timeseries for each of these quaniteis over time in different parts of

Bayesian probability

State of knowledge Degree of belief We haven't figured out what true climate sensitivity, there is just one true value and we would observe that if we added double carbon Statement about our state of mind not about the world We think the probability of climate sensitivity is x% Statement about our belief and strength of our scientific evidence

Probability density function (PDF)

Tells us the probabilities we have that a certain variable will take on a certain valuable All possible values on x axis and figure shows which range within this story is how likely. Area between a and b relativity to the area of the probability density function Probability density functiohn will give you a number between 0 and 1 Climate scientists pretty confident that value are most liekle in middle, but still can't rule out the extreme values ***One problem with climate sensitivity that the range of possible values is quite large. Difficulty lies in quanitfiying the size of these feedbacks

Kyoto Protocol (1997)

The main international treaty on global warming agreed in 1997, which entered into effect in 2005 and mandates cuts in carbon emissions. Almost all the world's major countries, except the United States, are participants since clinton signed but senate never ratified (senate objected since didn't contain any emission reduction obligations for developing coutnries) problem: no enforcement mechanism not successful only showed reduction because end of soviet union only annex 1 countries 3 flexible mechanism to reduce GHG: (goal to lower cost of achieving these targets) international emission trading (handed permits that applied to targets and coutnries could trade them) clean development mechansim (if there was an opportuntiy in a non-annex 1 country could an annex 1 country could pay to get them to reduce, basically developed country invests in a project in the developing world and gets credit for that reduction) joint implementation mechanism canada, japan, russia left 2011

climate sensitivity

The response of the climate system to a given radiative forcing Delta T=lambda * delta F Lambda factor = 0.3 Anthropogenic forcing (c02 doubling ) => delta F = 3.7 w^m2 => climate sensitivity => delta T 1.1 C How much warming would we see in equilibrium for a doubling of CO2 concentrations from pre-industrial times=1.1 degrees C delta f=anthrogpenic fourcing

aersols

Tiny particles of liquid or dust suspended in the atmosphere (Most important anthropogenic aerosols is the suphate produced for So2) Aerosol direct effect=reflect or absorb sunlight Indirect effect=create more and smaller cloud droplets aersols are short lived => mask long-term problems as shield effect will disspiate 1 year after truning off a dirty coal plant (while co2 will stay for 100s of years)

role of oceans

We warm up surface temperature, but then some is taken up by the oceans, so that moderates the increase in warming we see at the surface Exchange of energy between atmosphere and ocean, slows down the increase in surface temperatures we observe

well mixed ghg verses short lived gases/aerosols

Well mixed: stay in atmosphere so long that it doesn't matter where you emit it (Aka co2 doesn't mater if emitted in china or california it is distributed across the whole globe equally) Location of emission is irrelevant for the greenhouse effect they cause Most of policy debagte is worreid about this, in particular co2 C02 is biggest change in radiative forcing Methane emissions are second most driver. Halo-carbons we emit them into the atmosphere, their chemical reactions occur => some will have cooling effect, but in net the warming effect is larger than the cooling effect N20 increases warming in atmsophere Short-lived gases and aerosols: Stay in atmosphere at most or dissolve or fall down, so not long enough to evenly distribute across the globe, So matters where it is emitted. location-specific effects like PM5, aerosols radiative forcing on net most potent

as co2 atmosphere go up then land will...

absorb more co2, since plants feed on co2 If biopshere didn't prefer better as a sink then all co2 would stay in the atmosphere and there would be more warming Same is true for ocean!! with phytoplankton!! These two feedbacks from the problem of climate change point of view a good thing, they help mitigate

IPCC SRES scenarios emissoins

continuing to rise with A2 A1 peaking mid century then falls a little B scenarios emissoins seem implausable People used to think real world was most like A2 emissions. Now that people see that is pessimistic and think we are on a path lower than A2 scenarios all assume world with no climate policy

detection vs attribution

detection=seeing we've made an observation that the climate has changed attribution=assigning why the climate has changed aka man made emissions

EU emissions trading scheme

one way EU tried to comply with Kyoto worlds first and largest ghg emissoin permit trading scheme covers all 28 member states + norway, iceland, liechestin covers 45% of EU emissons CO2 for power and heat generation, energy-intensive industries, n20 for producton processes, PFCs from alumnium smaller plants excluded for competivity and transporation sector Every covered entity needs emissions allowance for all its emissions Total number of allowance is caped by the regulator and less than what firms would use if they were unregulated. Market participants can trade emissoin allowances on a permit market. Like stock exchange market

EU emission trading scheme history

phase 1 (2005-2007): test phase, most allowanes given out for free, grandfathered in, failed be price collapsed since too many permits were given out phase 2: (2008-2012): 3 non-eu states joined, domestic aviation included, price more stable but fell during recession phase 3: (2013-2020): single EU cap rather than national caps, auctioning now default method for allocating allowances (economists like this better than grandfathering since windfall profits) phase 4: (2021-2030): giving out allowances free to industires in difficult international compeitive positions, more measures to keep price stable (but still has been violate which idsn't good), adjusts cap over time

prediction verses scenario approaches

prediction: I think x is the most likely outcome, probalisist forecast scenario: do not make any probalisiti statement, explictly saying not giving an probabilites on the scenarios just saying the scenarios are plausible---all scenarios are plausible but don't need an opinion on the likelihood of the scenario

Role of IPCC

publishes reports that review and synethezie scientific literature on CC--main idea is review it doesn't conduct orginial research or collect/monitor data, lags a bit behind other scienfic report. They are "policy relevant, policy nuetra and never policy prescriptive"

converting co2 into radiative fordccings

raditive forcing (concentraton co2)= 5.35ln(conceration co2/ concentration co2 pre industrial)

EU emission trading scheme conclusion

rocky start but now considered successful and good tool to reduce emissons at low cost phase 1: barely measurable reductions phase 2: 8% lower by end of phase 2 compared to starting point phase 3: -21% compared to 2005 levles phase 4: -43% compared to 2005 levels problems: over-allocation early days, prie violitivity, windfall prfits, weird fraud scheme, double regulation (german feed in laws (german renewable energy subsidies pushed coal plants out but these plants just sold their permits))

global warming potentials

standard conversion factors to express things as co2 equivilents time horizon dependnet (like there is a GWP for methane for 25 years and a differnet for methane for 100 years economic dislike conversoion factors like GWP since hard for economic analysis since depends completely on the T and can have an infinate amount of conversion factors on what time horizon you choose mkaing it very arbitrary

how attribution is done

take models run with and without anthrogpgoenic forcing Thus prove that these antrhogoenic forcings explain the observed temperature over the last 100 years or so

increase in temperature changes strenghts of fluxes

temp rises => land emits more co2 bad for climate change because biosphere act less as a buffer same is true for the oceeans but on a lesser degree

Conference of the Parties (COP)

the decision-making body responsible for monitoring and reviewing the implementation of the United Nations Framework Convention on Climate Change. It brings together the 197 nations and territories - called Parties - that have signed on to the Framework Convention. meets yearly, one country one vote, all decisions must be unanimous big cops: 1997 Kyoto, 2015 Paris

equilibrium climate sensitivity

the sustained change in mean global temperature that occurs if atmospheric carbon dioxide is held at double preindustrial values or 550 ppm the number we will eventually reach, taking centuries and long timehorzions due to lag tells us where the system is headed in the long run 2-5C