DARGAN M. W. FRIERSONDEPARTMENT OF ATMOSPHERIC SCIENCES

DAY 19 : 06 /01 /2010

ATM S 111, Global Warming: Understanding the Forecast

Assignments

Finish the book for next time! Read second half of “What You Can Do,” p.349-356

Final HW due Friday at 11:59 PMFinal exam: Wednesday 6/9 at 4:30 PMBring a #2 pencil for course evaluations next

class

Student Question on Solar Energy

Solar panels are dark: do they affect planetary albedo? Quote from Superfreakonomics:

“The problem with solar panels is that they’re black, because they are designed to absorb light from the sun. But only about 12 percent gets turned into electricity, and the rest is reradiated as heat -- which contributed to global warming.” – Nathan Myhrvold, Intellectual Ventures

Wrong! The albedo change is small and results in a negligible amount of heating.This is not a problem.

Solar Energy and Albedo

All the electricity in the world could be generated by solar panels covering an area of the black box below Total extra absorbed

radiation if panels are above desert: 0.01 W/m2

(compare with 4 W/m2 for doubling CO2)

Solar panels can also be installed on dark roofs

Other Types of Waste Heat

All electricity is inefficient and creates waste heat, which warms the planet a tiny amount Coal power plants create approximately the same

amount of waste heat as solar panels per unit energy output

These are all tiny compared with current climate forcing from greenhouse gases

This mistake in Superfreakonomics was quickly corrected by Ray Pierrehumbert on the realclimate.org blog One of the best sites on the web for quick, scientific

responses to inaccuracies about climate science in the mainstream media

One More Energy Topic: The Bad Ones…

We discussed alternative energies…What are the new technologies that would be

very bad for greenhouse gas emissions? Tar sands (AKA oil sands): extremely large quantities

in Canada and Venezuela Oil shale: major deposits in the USA

Tar Sands

Mixtures of sand, water & a dense form of petroleumHarmful to the environment

Strip mining destroys large amounts of forests Conversion process requires lots of water and energy

2-5 barrels of water needed to make a single barrel of oil 2 tonnes of raw sands per barrel of oil Up to 5 times as much CO2 emissions in extraction/refinement

Well-to-pump has 30-70% more emissions on average

44% of Canadian production is from tar sands (esp. in Alberta) Will become #1 source of US crude oil imports in 2010 (around

10% of total imports) Projected to be 20-30% of imports by 2030

Oil Shale

Carbonate rock rich in “kerogen” which is usually refined to convert fuels

Environmental concerns with this as well: Open-pit mining & waste

management issues 1-5 barrels of water used per

barrel (in relatively dry areas) CO2 emissions similar to worst

forms of coal

Climate engineeringAKA geoengineering

“The deliberate modification of Earth’s environment on a large scale ‘to suit human needs and promote habitability.’” [wikipedia.org]

“The intentional, large-scale manipulation of theenvironment.” [David Keith]

Geoengineering • Brief history

• Why consider it? – Large and unforeseen changes ahead

• Can we reduce impacts of global warming without reducing CO2 emissions by climate engineering? – Take CO2 out of the atmosphere (unlikely)

– Reduce sunlight to counter increased CO2 due to human activity

• Political and legal issues

• General pros and cons of climate engineering

Geoengineering: a brief history• 1974: Mikhail Budyko proposed injecting sulfur dioxide in the

stratosphere to create sulfate droplets that would scatter sunlight and cool the earth (like volcanoes);

• Early 1990’s: Edward Teller (father of the H-bomb, principal architect of “Star Wars” Defense Initiative, inspiration for Dr. Strangelove) and collaborators proposed putting designer (nanotech) particles into the stratosphere to deflect sunlight.

• 1992: The National Academy of Sciences issues a detailed study on geoengineering options for avoiding climate change, which includes evaluation of the science and a cost-benefit analysis for each option.

• 2006: Paul Crutzen (Nobel Prize winner for his work on the Ozone

Hole) re-discovers Budyko’s plan. He argues that the scope and speed of climate changes due to increasing CO2 -- coupled with the lack of any progress on mitigation -- requires this geoengineering solution be seriously considered.

Geoengineering: a brief history• 2009: The Blackstock report - An influential group of US scientists

write a prototype plan for geoengineering research and development, testing and deployment and deliver it to the Pentagon. The UK Royal Society writes an influential report outlining the state of the issue.

• 2009: The wildly popular Superfreakonomics book has a chapter about climate cooling that is (according to Joe Romm) “simultaneously skeptical of global warming science, critical of all mitigation measures, but certain that geoengineering using sulfate aerosols is the answer”.

Goal of Geoengineering

Basic idea: reduce shortwave radiation that gets to the surface If the radiative forcing decrease from this equals the

radiative forcing increase from CO2, the global temperature change should be close to zero

Remember energy balance equation?

Goal of geoengineering: decrease energy in from the Sunto make energy balance happen (& stop warming)

Energy out is decreased by moregreenhouse effect (from CO2)

Can Dimming the Skies Perfectly Cancel CO2?

No! Solar radiation and greenhouse gases have different effects

Remember attribution of global warming? Greenhouse gases have a different signature than

solar forcingGreenhouse gases warm nights more

Geoengineering would cool days more

Other Problems with Dimming the Skies

Precipitation has a different sensitivity to solar vs greenhouse gases Geoengineering should dry out the climate more

(solar radiation helps evaporate more water vapor from the surface)

Ocean acidification would continue Large effects on marine life not prevented

Effects on plant growth? They need sunlight

Other Problems with Dimming the Skies

We would have to do it forever (almost) If somehow we weren’t able to continue the scheme,

Earth would experience very rapid warming New estimates suggest 2-4o C warming within 10 years

Even after emissions go to zero (i.e., once we run out of fossil fuels), we’ll have to continue to do this until CO2 returned to a safe level (1000 years?)

With these problems in mind, let’s take a look at some proposed schemes

The basic strategy: Block enough sunlight to cancel radiative forcing due to increasing CO2

• Solar reflectors placed in outer space at a point where the gravitational field from the earth cancels that from the sun

• Mirrors orbiting the earth to reflect sunlight

• Make more clouds or more reflective clouds

• Place/shoot tiny particles in the stratosphere that reflect visible sunlight but don’t absorb infrared radiation

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• Designed to imitate volcano eruptions

• Inject a sulfate aerosol precursor (such as sulfur dioxide SO2) into the stratosphere that then forms sulfuric acid solutions & eventually small particles.

• These aerosols increase earth’s albedo by reflecting solar radiation back to space.

• When injected really high up & if the particles remain small, they take a long time to fall out (months).

• Cheap compared to some estimates of mitigation costs, 10-20 billion $US/year

Stratospheric Sulfur Injections

Cloud modification

• Shoot a very fine spray of sea water into the air: makes cloud droplets smaller and thus more reflective of sunlight

• Works best in pristine (ocean) areas. Need thousands of ships

• Downside: clouds are the weakest link in understanding climate change

Controlled enhancement of the albedo and longevity of low-level maritime clouds

Cheap: 2-4 billion $US/year

May be able to offset global temperature rise but since it’s not the same kind of forcing it’s impossible to exactly cancel.

For example, these schemes alter precipitation too:

Stratospheric aerosols tend to dry the tropics

Sea spray-cloud brightening over ocean preferentially cools the ocean, causing land-sea temperature gradients that tend to strengthen summer monsoons

Timeline of research,

development, testing and deployment

(stratospheric aerosols)

Blackstock et al 2009

Today8yr 15yr 25yr 300yr

1000yr

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Possible (unproven) options for getting 10Mt of sulfur aerosols in stratosphere each year

• Artillery: shooting barrels of particles into stratosphere with 16” Iowa Class naval guns– Three guns firing twice per minute for 300 yrs– “…surprisingly practical” (NAS 1992)

Blackstock et al 2009

Possible (unproven) options for getting 10Mt of sulfur aerosols in stratosphere each year

• High-altitude transport aircraft (e.g., Modified Proteus or White Knight Two, with a cargo bay)

100 planes; 800 flights per day for 300 yrs

Some downsides of the stratospheric aerosol sunshade solution

• Large uncertainty to how much/how often you have to inject sulfur into the stratosphere to cancel warming effect of increased CO2

• Not clear injecting SO2 works, recent study

suggests injecting sulfuric acid instead!

• Sulfur chemicals in the stratosphere may destroy

ozone in the protective ozone layer. So we might try nanoteched particles (may be difficult or impossible to remove).

Dr. Lowell Wood (aka Dr. Evil)

"Human beings are like cockroaches," Wood says with typical black humor. "It's fairly easy to kill the first ten percent of the population. And if you try really hard, you might even get the next ten percent. But no matter what you do, you'll never get that last ten percent. We will find a way to survive."

Profound and unaddressed issues associated with geoengineering

• Who decides if it should be deployed, and at what level? Who decides if it should be stopped?• What if one country decides to do it on its own, even

though it harms another country?

• There are important cultural, legal, political, and economic implications of geoengineering. How will they be balanced?

• Moral hazard: • If we have a possible solution to global warming, will we

be less inclined to reduce carbon emissions?

• We can’t rule out unanticipated harmful and perhaps irreversible consequences (e.g., ozone hole)

Final Comments on Geoengineering• CLIMATE ENGINEERING IS NOT NECESSARY

– We have the technology and innovation (but not the commitment of government incentives) to halt the increase emissions of CO2, reasonably fast and even reduce emissions greatly.

– Progress has been (still is) too slow to stem the tide however:

• Lack of public resolve• Lack of leadership and commitment in business and government.

Final Comments on Geoengineering• WILL CLIMATE ENGINEERING HAPPEN?

– It is incredibly easy and (in the short term) inexpensive compared with reducing emissions and transitioning to a non-carbon emission economy

• Cost is maybe only ~$10B/yr compared to ~$200B/yr to reduce carbon emissions (lots of uncertainty in these estimates though)

• Cost is less than 0.1% GDP for US, less than 2%for about 30 countries

– Players who are currently influential and have a lot to lose if greenhouse gas emissions are limited/reduced (oil and gas companies, libertarians) don’t lose from climate engineering

– Whoever holds the contract for the solution has huge profits guaranteed for a millennium

• E.g., initial work is largely funded by defense contractors and venture capitalists, including some of the richest people in the world

– Will we develop and deploy this technology?