Chapter 16:Future Climate

Part 3—Economicsand energy policy

• Reminder (point also made in An Inconvenient Truth):

Stabilizing atmospheric CO2 is extremely difficult! It requires huge cuts in emissions

Target goals for atmospheric CO2 and associated emission scenarios

The Earth System (2010), Fig. 16-8

• We need to cut CO2 emissions in half (3 Gt C/yr) just to limit ourselves to 750 ppmv of CO2

• Stabilizing at today’s CO2 level would require negative emissions, i.e., net

CO2 uptake

1990emissions

Cost-Benefit Analysis

• When evaluating whether or not a particular project, e.g. building a dam, makes sense economically, economists often employ cost-benefit analysis– Evaluate the economic costs of the project– Weigh these against the economic benefits

• This same type of analysis can be applied to global warming

The “DICE” Model

• DICE model = Dynamic Integrated Climate-Economy model– Developed by William Nordhaus at Yale

University– Weighs the projected economic damages

from global warming against the costs of mitigation

(spending power)

DICE model results

W. D. Nordhaus, Science 258, 1315, 1992

2CO2

• The discount rate, , is a key factor• Nordhaus assumes a discount rate of 3%/yr

• Recently, the issue of discounting, and of global warming policy in general, has been revisited in a British study called the Stern Review– These authors recommended using much

lower discount rates– Consequently, they suggested that we

should cut back much more sharply on CO2 emissions

Projected CO2 emissions and concentrations for different strategies

The Challenge of Global Warming: Economic Models and Environmental Policy,William Nordhaus, July 24, 2007

(See Figures 16-12 and 16-13 in The Earth System, ed. 3)

Carbon emissions CO2 concentrations

Businessas usual

Kyoto

Nordhaus

SternGore

Nordhaus

Stern

Businessas usual

Practical carbon policy implications

Nordhaus• $30/ton of carbon,

rising to $200/ton in 200 yrs. The initial tax is equivalent to– 9¢/gal on gas– 1¢/kWh on electricity

(~10% of current price)

• Stern– $100/ton initially, rising

to $950/ton in 100 yrs

Optimal carbon tax

The Challenge of Global Warming: Economic Models and Environmental Policy,William Nordhaus, July, 2007

Stern

Nordhaus

(Fig. 16-12a in The Earth System, ed. 3)

• Moral of this story:

How one decides to discount future costs and damages is very important to the decision making process. Considerations of intergenerational equity suggest that the discount rate should be low

Strategies for coping with global warming

• Reduce greenhouse gas emissions, especially CO2

– Energy conservation can help– Requires development of alternative energy

sources (solar, wind, nuclear, geothermal, etc.)

• Scrub the CO2 out of the atmosphere, or out of smokestack emissions, and bury it somewhere (carbon sequestration)

• Direct geoengineering of the climate

Energy-efficient cars

Toyota Prius• Should we pass regulations, e.g., the CAFÉ (Corporate Automobile Fleet Efficiency) standards, requiring cars to get better gas mileage?• Alternatively, should we impose a stiff gas tax, or better yet, a carbon tax, to encourage car buyers to purchase fuel-efficient vehicles?

Wind power

T. Boone Pickens

Wind is one form of alternative,and renewable, energy for producing electricity

Ground-based solar power plant

http://bp1.blogger.com/_n6urvItzBdQ/RfGjte8V1_I/AAAAAAAAGkc/rnAthBDsnRw/s1600-h/Image9.jpg

Two distinctly different types of plants:1) Photovoltaic2) Solar thermal power

High-voltage direct current (HVDC)

• For either wind or solar power, the best sources of power are often located far from where the power is needed

• HVDC is the best way to transmit power over long distances– Losses: ~3%/1000 km

• Hence, transmission from Arizona to New York (~2000 mi. or 3000 km) would involve losses of only ~10%

Long distance HVDC lines carrying hydroelectricity from Canada's Nelson river to this station where it is converted to AC for use in Winnipeg's local grid [Image and caption from Wikipedia]

“War of Currents” (late 1880’s)

Thomas Edison favored a systemdesigned around direct current

Westinghouse

Tesla

George Westinghouse and Nikola Teslafavored a system based on alternatingcurrent. They obviously won..

Existing and planned HVDC links

Xiangjiaba Dam to Shanghai(2000 km, in operation)

Amazonas region to Sao Paulo(2500 km, starting in 2015)

Satellite solar power

Image from Wikipedia

• Satellites could be placed in geosynchronous orbit• One might also be able to do this from the Moon (David Criswell, University of Houston)

Nuclear power plant

• Nuclear power is a known, but potentially dangerous means of producing electricity

• Waste disposal is an issue, if not a problem

• Reserves of fissionable 235U are limited need breeder reactors if you want this to last a long time. (Breeders convert 238U to fissionable 239Pu, i.e., plutonium)

The Susquehanna Steam Electric Station (image from Wikipedia)

Nuclear accidents

• Public acceptance of nuclear power is a big issue

• Accidents like those at Chernobyl (Ukraine), Three-Mile Island (Pennsylvania), and Fukushima (Japan) do little to increase confidence

• Are the dangers acceptable, or, alternatively, can they be minimized?

Satellite image on 16 March of the four damaged reactor buildings at Fukushima,Japan[Image from Wikipedia]

Nuclear waste disposal

• Disposing of nuclear waste is also a huge issue

• Currently, all of our spent nuclear fuel is stored on-site at power plants in ponds

• Opening of the nuclear waste repository at Yucca Mountain, Nevada, ~100 mi. north of Las Vegas, has been postponed indefinitely– Funding was terminated in

2009 by the Obama administration, for political (not technical) reasons

Picture of Yucca Mountain[From Wikipedia]

Carbon sequestration

• Klaus Lackner at Columbia University is a pioneer in this field

• One strategy: React coal with steam and produce hydrogen

CH2O + H2O CO2 + 2 H2

Then sequester the CO2 in deep underground aquifers, the deep ocean, or possibly in subglacial Antarctic lakes

Subglacial lakes

• Lake type--subglacial rift lake

• Max length--250 km• Max width--50 km• Surface area--15,690

km²• Average depth--344 m• Max depth--1,000 m• Water volume--5,400

km³• Residence time

(of lake water)--1,000,000 yrs

Lake Vostok circled in redImage and information from Wikipedia

Diagram of Lake Vostok

http://www.nsf.gov/news/news_images.jsp?cntn_id=109587&org=GEO

• Liquified CO2 would be pumped down into the lake • CO2 would form a clathrate, which would remain stable as long as the ice remained above it

Possible subglacial lake system

http://www.nsf.gov/news/news_images.jsp?cntn_id=109587&org=GEO

• Lake Vostok is one of as many as 50 subglacial lakes lying beneath the Antarctic ice cap• Lake Vostok alone has the volume of Lake Michigan

Geoengineering solutions

• Alternatively, we may wish to forget about the CO2 and simply try to compensate for the expected climate change– Need to worry about ocean pH!

• Different ideas for doing this

Stratospheric aerosol injection

• One geoengineering strategy is to intentionally inject sulfate aerosols into the stratosphere, mimicking a large volcanic eruption

• But, the resulting uneven distribution of particles could result in massive weather disruption

Mt. Pinatubo, Philippines, 1991

Seawater spray solution

http://www.treehugger.com/files/2009/09/wind-powered-yachts-sea-salt-climate-change.php

• Fleets of seawater sprayers could create additional tropospheric aerosol particles that could cool the Earth by increasing its albedo

The solar shield: Lagrange points in the Earth-Sun system

• It is theoretically possible to build a solar shield at the (unstable) L1 Lagrange point. (One has to actively adjust its position because this is an unstable saddle point in the gravitational potential field.)

The solar shield

• Rather than building a single large mirror, it is more practical to fly about one trillion smaller (2-ft. diameter) lenses (Roger Angel, PNAS, 2006)

• Technically, this is called a Fresnel lens

• Offsetting one CO2 doubling would require deflecting about 2% of the incident sunlight

uanews.org (Univ. of Arizona)

• In my opinion, none of the geoengineering solutions are advisable, although we may need to resort to them if other measures fail

• Energy conservation and renewable energy sources (including biomass fuels) must be part of the solution

• Nuclear energy should not be ruled out as an option

• The best way to make all this happen is to impose a gradually increasing tax on CO2 emissions, i.e. a carbon tax

Your professor’s opinions

Take-home lessons from this class

• We need to preserve our environment, as Earth is the only habitable planet that we know of

• Global warming is a real problem with which we will someday have to deal—and the sooner, the better!

• There may well be other Earth-like planets around other stars. Looking for them, and looking for signs of life on them, is a scientific endeavor that is well worth undertaking