Human and the Earth
ASTR 1420
Lecture 26
Section 10.5
Dr. Martin Luther King, Jr.
"Unlike the plagues of the dark ages or contemporary
diseases we do not yet understand, the modern plague of
overpopulation is soluble by means we have discovered and
with resources we possess. What is lacking is not sufficient
knowledge of the solution, but universal consciousness of the
gravity of the problem and the education of the billions who
are its victims."
Acceptance Speech: Margaret Sanger Award in Human Rights, 1966
World Population Growth Through History
12
Prediction
11
2100
9
Old
Stone
7 Age
Billions
8
New Stone Age
Bronze
Age
Iron
Age
6
Modern
Age
Middle
Ages
2000
5
4
1975
3
1950
2
1
Black Death —The Plague
1+ million 7000 6000 5000
years
B.C. B.C. B.C.
4000
B.C.
Exponential Growth
10
1900
1800
3000 2000 1000 A.D. A.D. A.D. A.D. A.D. A.D.
B.C. B.C. B.C.
1 1000 2000 3000 4000 5000
Source: Population Reference Bureau; and United Nations, World Population Projections to 2100 (1998).
Common misconception (or absurdity):
• All the people of the world could fit into the state of Texas, with room left
over to spare (therefore, there is no overpopulation issue).
• In the same spirit, one might say all the world’s people could easily fit into
Antarctica or the Sahara desert or into a large crater on the Moon.
Overpopulation is when the number of people can not be permanently
maintained without depleting resources and without degrading the
environment and the people's standard of living.
 Any country that cannot support its people in a sustainable fashion within
its own land area at its given per capita level of consumption is
“overpopulated”
By this standard, every country on Earth is overpopulated
Just how many of us are there?
Paul MacCready, designer of the first
solar-powered aircraft, has estimated
the total weight of all terrestrial and
avian vertebrates.
• When agriculture began (~10,000BC), we humans and our pets and livestock
together accounted for less than 0.1% of the total.
• Today, we and our domesticated animals account for 98% of the total
Tokyo Water Park Slogan
“Welcome to breathtaking Tokyo Water Park where you
can wash away the pressure and stress of the
overcrowded city and relax with your friends in the
smoothing enjoyment of sun, fun and splashing."
With its huge and still growing population and rapidly
growing per capita use of resources, China is a great threat
not only to China’s own environment, but to the world as a
whole.
Just a few specific examples:
• Endless construction of coal burning power plants
• Destruction of the world’s rainforests to supply China with food and other
resources
• Massacre of 100 million sharks a year for shark’s fin soup
• Funding of numerous environmentally and socially destructive dams worldwide
birthdearth???
Korea: 1.15 in 2009
Did something change here?
Logarithmic plot  straight line in this
plot is exponential behavior
slope indicates growth rate
1%/yr
0.035% per year
A closer look at recent trends…
green (oil) revolution
1.9%/yr
(pesticides, irrigation, fertilizers…)
industrial revolution
0.8%/yr
1.9%/yr  x2 population in every 37 years!
1950
1865
0.4%/yr
Physical implications of constant growth
• 2% growth per year in energy use, for example, doubles scale every 35
years
• But plenty of sunlight hits the land, so we’re good for a while
o With 15% efficient photovoltaic panels, we would cover all the land on earth
in 320 years at a 2% per year growth rate
• But what if we had 100% efficiency, and covered all the earth?
o We would reach the physical limit at 2% growth in 450 years
• Let’s put our solar panels in space!
o We would demand all the power the sun puts out in 1600 years (with a
manmade Dyson sphere!)
• But there are more stars in the galaxy
o We have to use all 100 billion stars in the Milky Way galaxy in 2800 years
• Lessons:
o exponentials are physically unrealistic over time
o the last 200 year period is anomalous, and may not be the best model for
anticipating our future trajectory
Global Warming
Consequences of Global Warming
• Extreme weather pattern :
o
o
o
o
o
hot/dry weather  wildfire
more freqeuent & severe storms
decreasing bio-diversity
increasing sealevel
…
Energy: Past, Present, and Future
A Physicist’s View
Tom Murphy
UCSD
Key Points
• The past few hundred years have seen an unprecedented availability of
energy resources
• Our economic framework and way of life has been built on this energy
foundation
• The future of conventional energy resources is jeopardized
• What are our options for adapting to a different future?
Global Solar Potential
Assumes 8% conversion efficiency; Black dots represent area needed to
cover ALL energy usage by humans (including all fossil fuels)
Oil: A Story of a Finite Resource
• Discovery must lead production: can’t pump what’s not found
• Global discovery peaked in ~1960
o still discovering oil, but < 10 billion barrels (bbls) per year, typically
• Production exceeded discovery in 1983
• Production must peak and then diminish—but when?
Why worry about peak oil?
• After all, oil is not the only fossil fuel
o and there are other abundant resources besides conventional oil
• Oil is the pivot for transportation
o and a global economy relies on global transportation
o from what far reaches did the parts in your cell phone originate?
• Once conventional oil is in decline, demand will likely send the price
shooting up
o and new efforts to stem the decline (with non-conventional oil) will be unlikely to
keep up with the relentless decrease of this massive-scale resource
 a 3% per year decline in oil supply would require almost one new nuclear
power plant per week of equivalent power replacement
• If a commodity as important to our economy as oil is in permanent decline,
can we expect continued growth?
o if not, what do interest rates, loans, banks even mean?
Recent global production and price
production did not budge
despite rocketing price
 maxed out?
tiny drop in demand
(from financial crisis)
resulted in huge drop
in price
 further evidence
that we were up
against the wall?
broad, flat peak?
3/12/09
25
So what do we do?
• DON’T PANIC, but Let your voice be heard!
• But we must take this seriously
o our assumptions about “business as usual” are fragile, and should be
examined
o complacency presents too great a risk
• Examples of complacency:
o
o
o
o
o
o
we always solve our big problems: our scientists will save the day
fusion/geothermal/tidal/solar/etc. will save us in time
we find more oil all the time: no worries
growth is what we do: look at the past few hundred years
we’ll be moving to Mars anyway
an event like the Great Depression can’t happen in modern times: we’re
financially smarter now (imagine this statement a couple of years ago)
Dr. Martin Luther King, Jr.
"Unlike the plagues of the dark ages or contemporary
diseases we do not yet understand, the modern plague of
overpopulation is soluble by means we have discovered and
with resources we possess. What is lacking is not sufficient
knowledge of the solution, but universal consciousness of the
gravity of the problem and the education of the billions who
are its victims.”
Acceptance Speech: Margaret Sanger Award in Human Rights, 1966
As learned men and women, we have responsibilities to remind the public.
In summary…
Important Concepts
Important Terms
•
•
•
•
• Global Warming
Overpopulation
Exponential growth
Global Warming
Consequences of Global Warming
Chapter/sections covered in this lecture : 10.5
Exam3 : the next class!!