What does (has, will) climate change do to us?
ENVS36b, Climate Change Economics and Policy, Spring 2021
Module 3: The socio-economic consequences of climate change
- Wars, Conflicts, and the Challenge from Malthus
- PSAT
- How do we measure climate impact from different sources
“Snow in the riverlands. If it was snowing here, it could well be snowing on Lannisport as well, and on King’s Landing. Winter is marching south, and half our granaries are empty. Any crops still in the fields were doomed. There would be no more plantings, no more hopes of one last harvest. He found himself wondering what his father would do to feed the realm, before he remembered that Tywin Lannister was dead.”
-Jaime Lannister, A Feast for Crows by George R.R. Martin
Some historical note
- Little Ice Age: 1300-1850
- Medieval society, agricultural production was still dominating output in most part of the world
- Conflict with increased frequency & prolonged duration
- The Hundred Years War (1337-1453)
- The Ottoman-Habsburg War (1526-1791)
- The Li Zicheng Rebellion (1629-1645)
- The Sengoku Period (1467-1600)
The vicious cycle
- Climate change leads to decreases in agricultural yields
- There are less resources (food, productive land) to spare
- Civil unrest, conflicts, and revolts
Iyigun, Nunn and Qian (2017)
- Cold waves in the past 50 year increases chance of wars/conflicts by 0.03 standard deviation
- Two consecutive cold waves increase chance of wars/conflicts by 0.09 standard deviation
- Impacts are larger in inland places comparing to coastal places
- Economy dependent on agricultural productivity
- Trade potentially alleviates climatic impact
Think about this:
- Will the same story be applicable when we look at modern day climate change?
- If so, where? And in what fashion?
One of the Modern Day “Folk Story” (McGuirk and Nunn 2020)
- In typical years, agricultural and pastoral neighbors coexist in a symbiotic relationship due to seasonal migration
- In the rainy season, pastoralists exploit marginal lands that produce sufficient biomass for their livestock while agriculturalists farm more productive lands
- Pastoralists then migrate along well-established corridors to arrive at agricultural farmlands after the final harvest, where they remain for the dry season
When there is drought happening
- Pastoralists are forced to migrate to agricultural lands early
- Causing potential conflicts in the dual-usage of land
- Decrease in precipitation in a neighboring pastoral society increases risk of agricultural societies by 29.6%
- This impact is much greater than if the agricultural society receives a drought in their own location
- Conflict increases only in dual-use locations - suitable for both agricultural and pastorial societies
- Most conflicts are characterized by state forces (backing-up landowners) battling against internal rebels or militia from neighboring countries (backing-up nomadic groups)
Question
- What are some of the ways to alleviate this conflict?
More comprehensive evidence
- Higher temperature and excess rainfall induce:
- Inter-group conflicts: civil conflicts, wars, riots and land invasions
- Political Instability
- 1 sd change in weather -> 11% increase in conflicts
- Most evident in Sub-Saharan African (why?)
Inter-personal conflicts
- Inter-personal conflicts: assault, robbery, rape
- Extreme heat increases crime even in developed countries: USA, Australia
- Excess rainfall leads to violence in India, Philippines, Tanzania
- 1 sd change in weather -> 2% increase in interpersonal violence
Estimates on inter-personal conflict
Why?
We are not sure at this point, but here’s some suspected mechanisms:
- Agricultural productivity
- Psychological and human capital
- Income shock
- Governance Structure
Estimates on election outcome
Final story: What does climate change have to do with academic performance?
Picture yourself siting in a room, starring at the answer sheet for the PSAT. It is 95 degree outside, and the classroom does not have AC or a fan. Your face is full of sweats, and your cloth gets wet. You just want to breathe.
What do you think the exam is going to go?
“Almost all our subjects were high school dropouts, juvenile delinquents, parolees, and those awaiting the draft. When these people were subjected to high temperatures in groups of 48, there was continual arguing needling, agitating, jibing, fist-fighting, threatening, and even an attempted knifing. At lower temperatures or in small groups, this behavior diminished. However, when graduate students were similarly tested, later that fall, there was no aggressive behavior even at the highest heat-and-crowding levels.”
- F. Rohles (Psychology Today, 1967)
Park (2018)
- New York City, Regents’ exam
- Needs a 65 to pass the exam
- Exam dates and times are fixed by subject
Regents exams
Comparing to taking the test on a day of 70F, taking the test on a day of 90F will:
- Lower the test score by 0.15 standard deviation
- 1/4 of the Black-White score gap
- 3/4 of the within-school Black-White score gap
- Lower the chance of graduation by over 10%
- That particular day has a persistent effect on future academic achievement
Picture yourself in the same situation, 95 degree without AC or fan. Your professor is up there talking jibber-jabber. And you just want to take a sip of your favorite ice-cream.
Do you think you can learn anything from the class?
Goodman et al. (2019)
- PSAT exam, repeated takers
- Measures temperature up to a year from the exam
- Measures an adaptation mechanism
Results
- Extreme heat in the past year significantly decreases PSAT score
- Sustained exposures are more damaging
- Only affecting weekdays, not weekends
What could be an effective adaptation mechanism for extreme heat?
Adaptation
- AC significantly mitigates impacts from heat
- Classroom w/ AC: virtually no effect from heat days
- Classroom w/o AC: negative effects are 4 times larger than average
- No AC in classroom or home: negative effects are 6 times larger
What is similar in these cases?
- Compare individuals quantitatively
- Same individual exposed to different weather at different times
- Different individuals exposed to different weather at the same time
- Estimate the adverse effects of weather
- Impaired cognitive ability / ability to concentrate
- Diminished resource outputs that are crucial to a society
- Impacts are transmitted within human society
- Lower academic performance, later-life achievements
- Groups fighting for resources, leading to conflicts and wars
- Project that into the future
- Climate == Probability distribution of weather events
- We have: how societies are affected by some particular weather event
- Future impact = current impact * changes in the weather distribution
- Measuring adaptation if possible
- Irrigation
- Install AC in classroom, especially for under-privileged communities
- International assistance, robust local institutions
So, how do we evaluate these impacts?
- Climate Change affects many aspects of our lives
- And livelihoods of people across the planet
- At the same time, combating climate change requires efforts
- No matter it is economic costs or the use of actual resources
- No matter it is mitigation or adaptation
- There is always a marginal trade-off between
- Use resources to combat climate change
- Let climate run its course
Two paradigms in economics
- The top-down approach
- a.k.a Integrated Assessment Models
- Try to parametrize the entire state of the economy using systems of models
- These models capture the many shocks and feedback mechanisms created by climate change
Nordhaus (1980): A system of models
DICE
Two paradigms in economics
- The bottom-up approach
- Estimate damages from each individual category
- Incorporating adaptation along the way
- Aggregate them up into the overall damage
