We estimate:

• 0.1 pounds of CO2e per kilowatt hour from wind and solar, mostly manufacture and placement
  
• 0.3 from nuclear, mostly fuel processing
• 1.0 from hydroelectricity, mostly vegetation in reservoirs decaying to methane (3 to 11 for reservoirs in forests)
  
• 1.8 average from US grid (or see "Nations" tab for over 100 other countries)
• Spreadsheet shows the steps of the calculations

Hydroelectric reservoirs convert some of the carbon in the area they flood to methane. Methane has 25 times as much global warming effect as CO2, so hydroelectricity which converts carbon to methane can have major global warming effects.

Methane forms when plant matter decays in the absence of oxygen (anaerobic or anoxic). This decay often happens in reservoirs. The bottom of tropical reservoirs is often low in oxygen because surface waters are warm, stay on top, and mix little with the bottom. The bottom of northern reservoirs is often low in oxygen when the surface is frozen. Oxygen is low in any climate when a reservoir suffers eutrophication: blooms of algae, whose decay uses up the oxygen in the water.

One source of methane is the decay of the original plants and carbon in the soil, which were flooded when a reservoir was created.

A second source of methane is that reservoirs convert to methane some of the carbon continuously arriving from detritus, branches and leaves falling in tributaries.

Third, every year plants grow on the sides of reservoirs when water levels drop, and then are covered and decay when water levels rise again.

Any of this annual carbon which is released as CO2 does not contribute to global warming, since it was recently captured from an equal amount of CO2 in the atmosphere, so there is no net effect. But any which is converted to methane has a large global warming effect, since methane is 72 times as powerful as CO2 in the first 20 years, and 25 times as powerful over 100 years.

Introductions to the issues are in New Scientist, Scitizen, and International Rivers. The best detailed overview is by Farrer. She explains clearly where the CO2 and methane come from and go, citing a range of studies. Larger wood of many species does not decay under water; 42% does decay. The highest greenhouse gas emissions per kilowatt hour of hydroelectricity are from shallow reservoirs which flood and decay and drain large areas relative to the power generated.

The studies treat methane as causing 21 or 25 times as much as an equal weight of CO2, which are estimates for the relative effect over 100 years. Over 20 years, IPCC says the multiplier would be 72, since most of methane's effect is immediate. If one is concerned about the next 20 years, the larger multiplier would be appropriate and hydroelectricity would be seen as much worse.

Hydroelectric emissions in the CO2List footprint calculator are based on the average of nine reservoirs reported by Farrer in Brazil in various ecosystems: savanna, Atlantic forest and rainforest. The data for the nine reservoirs did not include emissions at the spillway and turbines, for which we had a choice of two multipliers, 1.9 from the Petit Saut dam in French Guiana rainforest, which has been more intensively studied, or 15 from a study of Tucurui, a large dam in Brazilian rainforest. We chose the smaller adjustment. The individual reservoirs would have estimates of 0.03 to 11.3 pounds CO2e per kilowatt hour (excluding distribution losses). The average of the various ecosystems, with more or less plant matter to decay, is 1 pounds per kilowatt hour. The calculator increases this for transmission losses in each country.

A study by the University of California-Berkeley had an overlapping range of estimated emissions, from 5.9 pounds/kwh in tropical forests to 4.5 in temperate forests, 2.9 in boreal forests, and 0.8 in woodland/shrubland, 0.2 in grassland and 0.1 in desert scrub, all omitting the decay from annual detritus arriving. They cite IPCC's 2003 Guidance for the original carbon content of the flooded areas, including soils.

The 1 pound/kwh which the calculator uses, is at the low end, since it represents an average of ecosystems. When hydroelectric reservoirs are known to be in forests, the Berkeley estimates would be better. Though incomplete, they are internally consistent, they are comparable to more specific local studies, and they reflect the large amount of plant matter in forests.

The Tucurui dam in Brazil was estimated to have total emissions of 2.3-3.4 pounds/kwh. Petit Saut in French Guiana is estimated at 5.9 pounds/kwh, total. A study of two large reservoirs in boreal forests in Finland yields a figure of 5.0 pounds/kwh, omitting emissions at the turbines, spillway and downstream, as well as methane bubbles in the reservoir from soil decay. A study by Hydro Quebec and the University of Quebec measured only emissions from the reservoir surface, not the turbines, spillway, or downstream, and compared them to natural lakes, rather than to pre-existing land use.

One study of nitrous oxide from reservoirs finds its net effect is less than 10% of other gases, so it has not been included.

Greenhouse gases are also released from quarrying, earthmoving, concrete manufacture, and building the turbines, though the only study in the spreadsheet shows construction is not as significant as greenhouse gases from reservoirs.

Hydropower Studies Summarized by IPCC. IPCC's Special Report in 2011 summarizes some studies about greenhouse gas emissions from hydroelectricity. However they excluded from their summary results any estimate of land use change (Annex 2 Methodology, p.14), which is one of the two biggest sources of hydroelectric emissions, along with leaves and twigs arriving from tributaries to decompose into methane in the bottom of reservoirs.

They included studies which had numbers on any two stages in the life cycle (p.13), and treated the results as if each study were a total of all stages of the life cycle. Some of the older studies omitted emissions from the reservoir, looking mostly at construction We tried to avoid this incompleteness problem by combining, from different studies, the strongest results for each stage of the life cycle.

A surprising number of studies of reservoirs show tonnes of emissions, but not electricity generated, so one cannot calculate emissions per kilowatt hour; IPCC did not seek electricity figures from public records and did not use those studies.

The following are the studies used for the IPCC Special Report's quantitative estimates. Special Report on Renewable Energy Sources and Climate Change Mitigation (Annex 2 Methodology, pp.25-6) May 2011 http://srren.ipcc-wg3.de/report/

Barnthouse, L.W., G.F. Cada, M.-D. Cheng, C.E. Easterly, R.L. Kroodsma, R. Lee, D.S. Shriner, V.R. Tolbert, and R.S. Turner (1994). Estimating Externalities of the Hydro Fuel Cycles. Report 6. Oak Ridge National Laboratory, Oak Ridge, TN, USA, 205 pp. http://www.osti.gov/energycitations/servlets/purl/757384-22LKCY/webviewable/757384.pdf

Omits all emissions from decay of the original flooded carbon, annual detritus, annual shoreline growth, reservoir surface, turbines, spillway and downstream. It was done in 1994 before those gaps were well-researched.

Denholm, P., and G.L. Kulcinski (2004). Life cycle energy requirements and greenhouse gas emissions from large scale energy storage systems. Energy Conversion and Management, 45(13-14), pp. 2153-2172.

Dones, R., T. Heck, C. Bauer, S. Hirschberg, P. Bickel, P. Preiss, L.I. Panis, and I. De Vlieger (2005). Externalities of Energy: Extension of Accounting Framework and Policy Applications: New Energy Technologies. ENG1-CT-2002-00609, Paul Scherrer Institute (PSI), Villigen, Switzerland, 76 pp. http://gabe.web.psi.ch/pdfs/externe_pol/WP6_Technical_Report_Release_2.pdf

Summarizes an early version of the data in the 2007 report from the same principal author (below), and less complete than the 2007 study. No data given on emissions from decay of the original flooded carbon, annual detritus, annual shoreline growth, reservoirs, turbines, spillways and downstream, and less explanation given in general than the limited amount in the 2007 report.

Dones, R., C. Bauer, R. Bolliger, B. Burger, T. Heck, A. Roder, M.F. Emenegger, R. Frischknecht, N. Jungbluth, and M. Tuchschmid (2007). Life Cycle Inventories of Energy Systems: Results for Current Systems in Switzerland and Other UCTE Countries. Ecoinvent Report No. 5, Paul Scherrer Institute, Swiss Centre for Life Cycle Inventories, Villigen, Switzerland, 185 pp. Available at: www.ecolo.org/documents/documents_in_english/Life-cycle-analysis-PSI-05.pdf.

Omits emissions from turbines, spillway and downstream. Emissions from reservoir surface largely based on natural lakes (p.101) without adjustment, though natural lakes do not have recently flooded carbon decomposing under the water. Furthermore, reservoirs are designed to have more outflow than most natural lakes, to drive turbines, so reservoirs have more inflow and thus more detritus arriving and decaying into methane in the reservoirs.

The report is dated 2007, but all data on reservoir emissions come from 2000 or before except a 2002 study from the Swedish power company, which also omits most reservoir emissions. They are aware of the newer Brazilian and Finnish studies, which measure reservoirs rather than lakes, but say they are not finished yet.

They do document how much cement, concrete and steel are in the dams, but no figures on how much CO2e they allocate to these sources (proprietary).

They use a 150-year time frame for dams, with no evidence, rather than the normal 100-year IPCC planning period. The main effect of the 150 years is to allocate a third of the construction emissions out of the IPCC time frame, even though they are emitted at the beginning, not the end.

They also have useful information on distribution losses for 26 European countries, ranging from 3.8% stated for Finland to 18.2% in Croatia (p.168)

Horvath, A. (2005). Decision-making in Electricity Generation Based on Global Warming Potential and Life-cycle Assessment for Climate Change. University of California Energy Institute, Berkeley, CA, USA, 16 pp. Available at: repositories.cdlib.org/ucei/devtech/EDT-006 http://escholarship.org/uc/item/8jh5x7z4

Report on hydroelectricity from Lake Powell on the Colorado River in the Utah desert.

Omits CO2e released immediately from arriving detritus as it decomposes in the water, not trapped in sediment.

Otherwise the lake is a relatively low emitter of CO2e, since not much biomass was flooded, and limited amounts arrive each year from the sparsely vegetated lower basin. However detritus does arrive from the upper basin of the Colorado River, which includes the western and southern slopes of the Rocky Mountains in Colorado, Wyoming and Utah.

Even omitting all detritus arriving, the report estimates 49 grams of CO2e per kilowatt hour for this site in desert scrub (0.1 pounds/kwh), and estimates emissions for the same type of dam (p.9) would be 2,696 g/kwh in tropical forests (5.9 pounds/kwh), 2,053 in temperate forests (4.5) and 1,296 in boreal forests (2.9).

The IPCC Special Report does not include those higher estimates.

In addition to these numbers the report says 4.6 g CO2e per kilowatt hour accumulate in bottom sediments, to be released when the dam is decommissioned (p.10).

For dam construction, the report uses the most complete input-output analysis (p.2), which includes indirect emissions from all the suppliers to the dam.

It also counts foregone carbon capture as an emission (p.9).

Another aspect of desert reservoirs is evaporation of water vapor, which is also a greenhouse gas. It is not clear if the atmosphere holds more water because of Lake Powell than it would if the river continued unhindered to the Sea of Cortez and Pacific.

IEA (1998). Benign Energy? The Environmental Implications of Renewables. International Energy Agency, Paris, France, 128 pp.

Pacca, S. (2007). Impacts from decommissioning of hydroelectric dams: A life cycle perspective. Climatic Change, 84(3-4), pp. 281-294.

Rhodes, S., J. Wazlaw, C. Chaffee, F. Kommonen, S. Apfelbaum, and L. Brown (2000). A Study of the Lake Chelan Hydroelectric Project Based on Life-cycle Stressor-effects Assessment. Final Report. Scientific Certification Systems, Oakland, CA, USA, 193 pp. Rhodes http://www.chelanpud.org/relicense/study/refer/4841_1.PDF

Report done to support relicensing, omits influx of detritus, which is now the main source of emissions, since the dam was built in 1926. The reservoir is bordered by wooded hills in Washington State, about 100 miles from Seattle and Puget Sound. The report also does not explain how it allocates carbon between methane and CO2.

Ribeiro, F.d.M., and G.A. da Silva (2009). Life-cycle inventory for hydroelectric generation: a Brazilian case study. Journal of Cleaner Production, 18(1), pp. 44-54.

Vattenfall (2008). Vattenfall AB Generation Nordic Certified Environmental Product Declaration EPD® of Electricity from Vattenfall´s Nordic Hydropower. Report No. S-P-00088, Vattenfall, Stockholm, Sweden, 50 pp. http://www.environdec.com/reg/epd88.pdf and http://www.environdec.com/reg/088/dokument/08_waterEPD.pdf

Swedish electric company reporting on their own operations. They omit ongoing arrival of detritus, and most details on their calculations, saying the information is proprietary. They say their land was cleared before flooding, removing emissions from the reservoir, but do not address the decay of the removed vegetation or the remaining leaf litter decaying under water and they identify a quarter as much soil carbon as given in the source they say they used. Further discussion.

Zhang, Q., B. Karney, H.L. MacLean, and J. Feng (2007). Life-Cycle Inventory of Energy Use and Greenhouse Gas Emissions for Two Hydropower Projects in China. Journal of Infrastructure Systems, 13(4), pp. 271-279.

The USA releases 44,000 pounds of CO2 per person per year. This is four times the world average (11,000). This world average is triple the 3,700 pounds needed to limit warming to 3.6F (2C) above pre-industrial levels.

Reducing from 44,000 to 3.700 pounds is a 92% reduction. President Obama (like most other candidates) promised and expects an 80% reduction by 2050. Thus the 92% reduction discussed here is close to mainstream. The World Wildlife Fund and others have calculated a plan to reduce UK emissions 80%, starting from a level already half as much as the US.

The present 44,000 pounds per person per year in the US is net. It includes CO2 in the products we import, excludes our exports, and gives credit for almost 4,000 pounds per person per year of reforestation.

China releases 7,000 pounds per person per year, and India releases 2,400 pounds, both on the same basis as the US, net of imports, exports and reforestation.

The UN Development Program (UNDP) estimates that limiting emissions to 1.5 trillion metric tonnes of CO2 in this century will stabilize the atmosphere and limit global warming to 2C, which they think the world can handle (2007-8 Human Development Report, pp.46-47 in chapter 1 at hdr.undp.org/en/reports/global/hdr2007-2008/chapters/). They divide the century's 1.5 trillion metric tonnes by 100 years, to give an average 15 billion tonnes of CO2 released worldwide per year, or 32 trillion pounds.

With 8.8 billion people in the world on average this century (6.9 billion in 2010, annual data are in population tab of worldpath spreadsheet), the 32 trillion pound target for CO2 would allow 3,700 pounds CO2 per person per year, if we could switch to that immediately. In the long term no country can expect to use more than the average.

UNDP estimates that the above limits will stabilize the atmosphere at 450 parts per million (ppm), and may limit the increase in average world temperature to 2C (3.6F) above pre-industrial levels. Their estimates are based on modeling done for them by the Potsdam Institute for Climate Impact Research. Their estimates only address CO2, since they say releases of other greenhouse gases are balanced by releases of aerosols (dust, etc) which cool the earth (p.199, notes 29-30, quoting International Panel on Climate Change).

The International Energy Agency's World Energy Outlook 2008 agrees that 450 ppm would provide a 2C (3.6F) increase, and says 550 ppm would provide 3C (5.4F) increase above pre-industrial levels.

World average temperature has already risen about 0.8C (1.4F) above pre-industrial levels, so a goal of 2C means 1.2C warmer than now (2.2F). (p.6 of the 4th Assessment's summary for policy makers at ipcc-wg1.unibe.ch/publications/wg1-ar4/wg1-ar4.html). The 1.4F rise already endangers species, melts glaciers, and causes more extreme weather. An additional 2.2F will have many more effects.

The atmosphere now has about 388 ppm of CO2 (rising 1 ppm every 2-3 months), and many people believe it needs to go down to 350, not up to 450. It was 280 before industrialization. The alternate target of 350 would require far lower emissions, discussed below.

All these ppm numbers are based on how many molecules of carbon dioxide are in the atmosphere per million molecules of dry air. "Dry air" means water molecules are not counted. This is also called the "dry air mole fraction" or "parts per million by volume" or ppmv. CO2 molecules are heavier (44 grams per mole) than the atmospheric average (28.97 or 28.966, mostly from N2 and O2 molecules). The current 388 ppm by volume is about 589 ppm by mass (388*44/28.97=589).

The sustainable emissions per person will drop in the future, because (a) population will grow so the annual limit is divided among more people, and (b) we continue to release CO2 at high rates, using up the century's limit, and leaving less per year for the rest of the century. These calculations depend on how fast we cut:

If the world cuts CO2 rapidly for 25 years, and stabilizes at 2,800 pounds per person per year, we will achieve the needed 3,700-pound average for the whole century, with a 3.6F rise. 2,800 is near the current level of India.

CO2 per Year per Person, Pounds
]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]  44,000  USA
]]]]]]]]]]]  11,000  World
]]]]]]]  7,000  China
]]]  2,800 Target
]]  2,400  India

If we cut slowly over 50 years, we emit so much while we are cutting that we have to stabilize much lower at 1,800 pounds per person per year, to reach the 3,700 pound average. 1,800 is near the current level of El Salvador and Sri Lanka.

These are 94% and 96% cuts from the US level of 44,000 pounds per person per year. If the US does not cut to 2,800 pounds in 25 years, someone else has to cut deeper, or the US cooks the planet.

If we could hurry up and cut down our CO2 in 10 years, we would only have to cut to 3,300, near the level of Uruguay and Sudan. If we take 70 or more years to cut CO2, the whole world has to cut to zero, since emissions while we are cutting use up the entire century's CO2 budget.

Table of 50-, 25- and 10-year Scenarios to Cut CO2

A clear review of options to provide energy sustainably is MacKay's 2008 book, Sustainable Energy withouthotair.com/download.html It estimates that large fractions of each country will need to be covered by solar collectors, wind turbines and/or biomass crops to produce the energy we use. This expansion will change views and ecosystems, though not as badly as global warming. MacKay's book does not estimate the CO2 released to manufacture those collectors and turbines, or to clear the land for biomass crops.

YOUR OWN CLIMATE MODEL

In an interactive model at chooseclimate.org/ you can move a cross to set a target level for CO2 in the atmosphere. (In their various models, we recommend starting with the older, fully documented model.)  Setting it at 450 ppm (the UNDP recommendation) makes an estimate appear on another graph showing how many billion metric tonnes of Carbon could be emitted each year, consistent with this goal. Slide the cursor around on that graph, and you can read that the graph drops from 7 billion to 2 billion tonnes over the century. This is an average of 4.5 billion tonnes of Carbon per year, which is 16 billion tonnes of CO2 per year, virtually the same as the UNDP's estimate of 15 billion.

Changing the target for the atmosphere to 350 ppm yields an estimate that emissions would have to drop to zero for a while, before stabilizing at 600 million tonnes Carbon per year, which is 2 billion tonnes CO2 per year, or 700 pounds CO2 per person per year. One sees why 350 ppm is not a popular goal, though the model predicts temperature would only rise 1.9F, instead of 3.6F above pre-industrial levels. This would still be half a degree warmer than now. (In the chart of Temperature rises, you can set the baseline year to 1750 to reflect a "pre-industrial" baseline.)

SOLUTIONS are discussed on another page

REASONS FOR OPTIMISM are discussed on another page

BENEFITS

The fruits of success will include more food, coral and species saved; fewer floods, droughts and tropical diseases; and less extreme weather.

The International Union for Conservation of Nature, which for decades has monitored the risk of species becoming endangered (the "Red List") says climate change endangers 35% of the 10,000 bird species studied, 52% of the 6,000 amphibian species studied and 72% of the 800 coral species studied (Species Susceptibility to Climate Change Impacts IUCN 2008). These species are affected by:

* desynchronization of migrations; 
* uncoupling of parasite/host, predator/prey, & mutualisms (eg. pollinators);
* interaction with new pathogens and invasives; 
* loss of habitat; 
* increased stress; 
* changes in fecundity, sex ratios and competitive ability;
* inability to deposit calcium (e.g. shells and bones).

A CO2 offset usually means paying someone else to reduce greenhouse gases (beyond what they would have done anyway) and claiming it as your own reduction. The fallacy is that it usually involves double-counting, where both you and they (or their country) claim the same reduction.

For example you join with others (usually through a nonprofit) and:

• (A) you pay for a power company to reduce its emissions by 400,000 pounds of CO2 per year. This might be done by energy conservation, CO2 capture, building windmills, reducing transmission losses, etc., if feasible.
• or (B) you pay for a landfill to reduce its methane emissions by 400,000 pounds of CO2-equivalent gases per year. Typically this means capturing methane and burning it to CO2, which is much less harmful than methane.
• or (C) you pay a group of farmers to reduce Nitrogen fertilizer by 85,000 pounds of Nitrogen, reducing nitrous oxide emissions by 1,300 pounds, which is equivalent to 400,000 pounds of CO2.
• or (D) you find 200 people in a poor country emitting 3,700 pounds of CO2 per year each. You pay them to cut back by 2,000 pounds each to 1,700 pounds per person per year. Maybe you provide solar cookers, etc. Again you have a savings of 400,000 pounds per year.
• or (E) you pay to expand a tropical forest which absorbs 400,000 pounds more CO2 than the previous land use (e.g. fields and pasture, and you pay to reduce the demand for these).

In any of these examples, suppose you pay 10% of the cost, so you claim credit for reducing emissions by 40,000 pounds per year. You then continue to emit 44,000 pounds per year, but say your net emissions are only 4,000 pounds per year.

However the power, landfill, and farm customers also can look at the new lower emissions by their power, landfill and farm, and they too claim they are emitting 400,000 pounds per year less than before. The only way to avoid double-counting is to pretend they are still emitting the same old high levels. But all the CO2 reports and goals around the world look at actual emissions, not what the emissions would have been if you hadn't paid to reduce them.

Furthermore, your personal reduction only makes sense as part of a worldwide reduction to the sustainable level of 3,700 pounds CO2 equivalent per person per year. Most of those power, landfill and farm customers themselves emit far more than this goal, and have to reduce to that level for a sustainable earth, so you are claiming reductions which they needed to make anyway.

The farm example is a proposal by Michigan State University to reduce fertilizer slightly, from the upper to lower bounds of recommended ranges in the Midwest, expecting no decrease in yields. If there really is no decrease in yield the farmers would do it anyway to save fertilizer cost. If it decreases yields, other land has to be cleared or fertilized more to grow the missing food. The Midwestern farmers and their customers already emit far more CO2e than a sustainable level, so selling an offset means they pay themselves to continue emitting unsustainably. Furthermore the authors acknowledge (p.202) that it would take expensive accurate testing (emitting CO2) to measure nitrogen levels in soil or plants, to be sure the farmers did not add more fertilizer anyway, to increase yields.

The poor country example (D) is different. These savings really would help us get closer to a global goal. But you are unlikely to find people willing or able to reduce their emissions so low. Just making and maintaining the solar cookers uses up some of the CO2 savings. What can they buy with the money you pay them without using up even more of the CO2 savings? As they develop (you want them to develop, right?) it will be hard enough for them to keep emissions under 3,700 pounds per person per year, let alone 1,700. Then consider the ethics and instability of such drastic inequality in CO2 output. It involves 20 people living at a destitute level of CO2 for every one person staying at the current US level.

China is often able to sell offsets, since it has companies ready and willing to reduce emissions from old manufacturing methods. However China, like richer countries, already emits more than the sustainable level of CO2 per person, so it needs its own reductions, and counting them elsewhere is double-counting.

The tropical forest example (E) does capture CO2 in years when you expand the forest and reduce demand for land. There are several issues to remember.

1. First, it is nearly impossible to reduce the demand for fields and pasture (i.e. demand for food and biofuels). If you don't reduce the total demand, growers will expand into some other forest.
2. Second, you need to ensure that your forest does not contract in the future.
3. Third, if you want to call this your offset, you need to ensure that the tropical country does not double-count the forest expansion as part of its own net CO2 efforts.
4. Fourth, continuing the same size forest does not capture much CO2, because the constant cycle in a forest, of plants dying and decaying, releases nearly as much CO2 as the forest absorbs. Plants take in CO2, release O2 and put the C in their cells. Plants die and as they decay insects, fungi and bacteria take in the C, combine it with O2 and release CO2.

Example (E) above is limited to tropical forest, since expanding temperate forest reduces snow reflection and absorbs sun, so it warms the earth even though it absorbs CO2. Planting in temperate deserts would not have problems 2-4, but they don't have water.

All the discussion above about paying others to reduce CO2 emissions is a version of the "cap and trade" method of limiting emissions. That is a term used when governments cap CO2 emissions, and allow emitters who can go below their cap to sell the savings to emitters who can't cut so easily and stay above the cap. Overall the caps would be met. On a long term world scale, people would have a cap, such as 3,700 pounds CO2 emissions per year, and people above the cap would have to buy emission rights from people below the cap. Buying from people above the cap, who have no unused emission rights to sell, doesn't get you anywhere. In fact, as mentioned on the Goals page, the 3,700 pound limit per person will have to drop even lower in the future as world population rises, to keep world emissions at or below 32 trillion pounds CO2 per year, which in turn is necessary to hold the temperature down.

A landfill like example (B) above was the subject of a controversy between Business Week and Terrapass over CO2 offsets claimed by the 2007 Academy Awards ceremony. Supporting the landfill purportedly let the stars offset the CO2 emitted by their celebrity lifestyles. However that controversy only addressed whether current regulations would have forced the methane to be captured anyway. Regardless of old regulations, the earth does require both methane capture and CO2 cutbacks in our lifestyles. It is not a choice. It is both, and much more.

UK consumer group's overview of offsets with helpful ratings and links

Friends of the Earth statement against offsets

You can choose several models on the opening screens of the "Climate Model" link below. We recommend starting with the older, fully documented model.

You will see crosshairs which you can move on the screen. Moving them chooses a target level for average CO2 in the atmosphere. The 2009 level is 386. (This means 386 molecules of CO2 per million molecules in the atmosphere; "parts per million" or ppm.)

Setting the crosshairs at 450 (a common recommendation) makes a line move on another part of the same screen, showing how the world's Carbon emissions need to drop each year, to stabilize at your chosen level.

Another line on the same screen shows the resulting rise in temperature, relative to 1750 or any later year.

Then try other targets, like 350 or 550, and see how emissions and temperatures are affected.

The options are discussed more on our Goals page.

Go to the Climate Model.

CO2 Labels

Labels would help us choose products wisely, and would influence producers to reduce their CO2 emissions as much as they can. A British system encourages labels on products. A Swedish system encourages fact sheets on the web (these are extracts of their "Environmental Product Declarations").

Cooling the Earth

Capturing CO2 in the oceans, with plants, or with other offsets does not seem to be feasible, but reflective roofs and burying charcoal can help.

Money Incentives

We can be creative when the incentives are strong. The strongest incentive is a rising fee for CO2 emissions, with wide public support for the fee. Wide support for a large fee will come only if we distribute all the revenue in a public dividend. Alaskans support oil royalties, because they get a dividend. Workers support Social Security, because it comes back to us. People will support a growing CO2 fee if the money comes back to us. Start at a penny per pound of CO2, which will provide $440 to each American. Then watch while we creatively save CO2 and support fee increases which raise our dividends, until the dividends finally fall off when CO2 use drops

The UN Development Program estimates 3¢ to 5¢ will stabilize the climate. Start at a penny and phase it in, which accomplishes 8 goals:

• Strong political support, since people are receiving dividends.
• Gains for people who use below average CO2, including the poor and energy conservers
• Losses for people above average CO2, giving an incentive to reduce
• A fiscal stimulus since people know the price of all products will rise, so better to buy now than after the next fee increase
• Long term planning by businesses, households and investors, since people would know what prices to expect
• Big sudden shocks are avoided
• Steady reduction in CO2 use
• The chance to stop raising the dividends when CO2 responds enough

Administering a CO2 fee is simpler than most taxes, since there are relatively few refineries, etc, where the tax would need to be collected. Each person could choose, as with income tax refunds, to get credit toward the next income tax, or immediate payment, such as by topping up a debit card each month with an equal share of CO2 fees received.

Imports can be charged fees to reflect their CO2 content also. These charges on imports would extend the reach of one country's CO2 price to encourage reductions in suppliers abroad too. The World Trade Organization allows such charges (p.xix of Trade and Climate Change, 2009, WTO & UNEP, also cited by Krugman).

CO2 levels and climate stability are discussed in our Goals page. UNDP's estimate of 3¢ to 5¢ per pound (p.127, 2007-8 Human Development Report) is smaller than the International Energy Agency estimate of 9¢ (p.11, World Energy Outlook 2008). Neither estimate is large compared to US average spending, so we should start and see how fast CO2 use drops.

Caps, Fees, Taxes, Auctions

Some authors call this a tax, others a fee for a permit to release CO2. In either case politicians will decide what is a reasonable level and start there.

Instead of setting the fee, one can set a cap on the annual amount of CO2 and auction permits. Businesses then bid whatever price it takes to get the CO2 permits they need. Environmentalists like this way of capping CO2, but it has two defects

• An auction for CO2 permits discourages long term planning, since people and businesses cannot be sure what price they will have to pay.
• A cap on CO2 emissions is not absolute, since politicians fear an auction price going too high and hurting the economy. So politicians will decide what is a reasonable ceiling which the economy can handle. That is a ceiling for the auction, with unlimited permits available at the ceiling price. The auction price can be anything up to the ceiling.

On the other hand if there is NO cap, politicians decide what is a reasonable ceiling which the economy can handle, and set that price, which they may call a fee or a tax. An auction will never be higher than the ceiling, and has a good chance of being lower, so an auction gives a lower price than the price set by politicians, and thus an auction under a cap has less carbon reduction than a simple fee or tax.

Who would want an auction which sets the CO2 fee below the reasonable level? Low fees encourage CO2 use now, and we would need to compensate by reducing the final CO2 levels even more: The cumulative total controls global warming. In other words the faster we cut, the less far we will have to cut, because we won't have as much catch-up to do. The more slowly we cut CO2, the more we emit now, the farther down we will have to cut, in order to compensate. Deeper cuts are a heavy price to pay for delay.

Tobacco and liquor taxes are not set by auctions. The government chooses a tax to discourage use and raises it periodically.

Other sites discuss Dividends to citizens, Carbon taxes, reasons for optimism, and an extensive discussion of the economics of pricing CO2.

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People have proposed methods to cool the earth, because it does not seem feasible to reduce CO2 enough.

A study by Lenton and Vaughan compares cooling proposals. Most have huge side effects, but bio-char, reflective roofs, and reduced soot seem to have the least harmful side effects (data on roofs and 3-year results). Bio-char has the negative effect of making soil absorb more sunlight, but this can be minimized, and more reflective varieties of crops can also help.

Lenton and Vaughan make the following four points:

* "By 2050, only stratospheric aerosol injections or sunshades in space have the potential to cool the climate back toward its pre-industrial state...

* "[L]arge reductions in CO2 emissions, combined with global-scale air capture and storage, afforestation, and bio-char production, i.e. enhanced CO2 sinks, might be able to bring CO2 back to its pre-industrial level by 2100,

* "[S]tabilising CO2 at 500 ppm, combined with [more reflective]... clouds, grasslands, croplands and human settlements might achieve a patchy cancellation....

* "Ocean fertilisation options are only worthwhile if sustained on a millennial timescale... Enhancing ocean upwelling or downwelling have trivial effects on any meaningful timescale."

Go to the Study of cooling options