Home » Climate Change » Greenhouse Gas Emissions (Page 3)

Category Archives: Greenhouse Gas Emissions

Drought in California Part 15: Summary and Discussion

This is the last post in my series on Drought in California. I’ve been writing the series for just over 3 months – I can’t believe it has been that long! I’ve looked at California’s climate, projections for how California’s climate might change through mid-century, California’s water infrastructure, California’s water supply, and patterns of water consumption in California. I’ve calculated the size of the water deficit that California might experience by mid-century, and I’ve looked at various ways California might attempt to cover the deficit: enacting policies to stop population growth, stealing water from the environment, diverting additional water from rivers, desalinating water, reducing agricultural water consumption, and reducing urban water consumption.

I’m not aware of anything like my analysis. If you are, I would love to read it, and I think other readers of this blog might like to, also. Please comment and let us know where to find it.

It looks to me like California faces some really difficult challenges. By mid-century, they are going to face a decline in water supply due to climate change. Put the decline in supply together with the fact that the population is predicted to grow, and the fact that they already overdraft their water, and they face a very large future water deficit. California has built an amazing water infrastructure, but there are problems associated with every possible alternative for covering the water deficit. Only a few seemed realistically possible to me: desalination, urban conservation, and agricultural conservation.

I constructed three scenarios for policies California might follow, but again, only one of them seemed realistic to me: conserving water in both the urban and agricultural sectors, desalinating enough water to cover the resulting urban demand, and diverting the remaining water resources to agriculture. This scenario would provide sufficient water to urban areas, but California would lose slightly more than half of its agricultural sector. I calculated the impacts such a scenario might have on California’s economy, and found that it would probably cause the economy to start shrinking. The result would be a recession, and eventually a depression. The impact would be worst in the agricultural sector, but it would be felt statewide.

The bulk of the projected water deficit comes from a decline in the snowpack that is projected to occur due to climate change. Obviously, if that projection turns out to be wrong, the entire analysis would have to change. Even if it holds true, it is likely to be a slow-motion train wreck. As I have been writing this series, an El Niño has formed, and El Niños are typically associated with lots of rain in California. It hasn’t happened yet, but many are hoping for a wet winter.

For my analysis, it doesn’t matter a bit. The projected 40% decline in the snowpack is a 30-year average. There will be wetter years, not every year will be as bad as this year. Thus, the problems I foresee are likely have a slow onset, except for economic effects. The economy depends on psychology, and asset prices do so especially. Psychology can (and usually does) change very quickly – ask anybody who invests in the stock market! At some point, I expect people to lose confidence in California. When? Before mid-century, but precisely when I don’t know. Until then, the economy will be okay. After that, it won’t. Everybody thinks they will be able to get out in time, but they never do. It is like being caught in an avalanche: there is no avalanche until the rocks are already sliding down the mountain. But then it is too late, and the avalanche slides down the mountain very fast!

As I said, I don’t know of any other analysis like mine, thus it has been a really worthwhile exercise. But it has been a lot of territory for one person to cover, especially someone who is neither an engineer, a water expert, nor a climate expert. Along the way I have had to rely on publicly available data sources. Some of them have been of the highest quality available, but others have been less reliable. There have been instances when data was not available, and I have had to make assumptions or “guesstimates.” Further, the analysis has sometimes had to predict how people will respond to the problems they will face. Predicting human behavior is notoriously hard to do. Yet if people respond differently than anticipated, the whole analysis will have to be redone.

All of these issues affect the quality of my analysis, and the reliability of my conclusions. The two areas most seriously affected are the calculation of the future water deficit and the calculation of economic effects. Take what I have written as an interesting exercise, but only the future will reveal what will actually happen.

Thanks for reading this long excursion away from what this blog usually focuses on. I’m going on vacation now for a couple of weeks. When I return in late October, I plan to get back to reporting on large-scale studies about Missouri’s environment.

Drought in California Part 7: Conserving Water – Agricultural Water Efficiency

This is the seventh post in my series Drought in California. In Part 1: California Climate and Drought, I found that drought is projected to be the “new normal” climate in California. In Part 2: The Status of California’s Current Water Resources, I found that California is already depleting both it’s groundwater and surface water resources. In Part 3: California’s Total Water Deficit, I constructed an overall estimate of California’s future water deficit, concluding that it will be about 25.1 million acre-feet per year, about 39% of California’s current dedicated water supply. In Part 4: The Potential to Procure Additional Ground and Surface Water, I found that a variety of obstacles and problems made it unlikely that California could cover the predicted future water deficit by tapping additional groundwater or surface water resources. In Part 5: The Potential of Desalination, I found that using desalination to cover the projected water deficit was within the realm of conceptual possibility, but it would be costly and would involve a massive infrastructure program. In Post 6: Conserving Water – Population and Environment, I discussed water consumption terminology and also concluded that conserving water by voluntarily limiting population growth or by stealing it from the environment would be objectionable due to severe negative effects.

In this post I will discuss the possibility for increasing agricultural water efficiency. At the beginning of each part of this series, I have noted that there are problems with the type of exercise I’m attempting, and with the data and analyses I’m having to use. If you want to read more about it, see the introduction to the series.

The Potential for Increased Agricultural Water Efficiency

Figure 26: Agriculture is an important industry in California. Photo by Wonderlane [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons.

Figure 26: Agriculture is an important industry in California. Photo by Wonderlane [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)%5D, via Wikimedia Commons.

Irrigation consumes 76% of California’s water, some 28.3 million acre-feet per year. Most of the irrigation is agricultural. (USGS, 2005) Because it is the largest consumer of water, agriculture is a prime target for water conservation. If the projected water deficit of 25.1 million acre-feet were prorated according to consumption, then 76% of the deficit would belong to agriculture, or about 19.0 million acre-feet per year. That represents about 69% of current agricultural consumption.

(Click on graphics for larger view.)

Some 77,900 California farms and ranches received $46.3 billion for their output in 2013, accounting for 12% of the national farm income total. California farms produced about 69% of the fruits and nuts produced in the USA, and 36% of the vegetables and melons. The top 10 agricultural commodities in California were (in order): milk, almonds, grapes, cattle, strawberries, walnuts, lettuce, hay, tomatoes, and nursery plants. (California Department of Agriculture, USDA) California is the sole U.S. producer (99% or more) of artichokes, dates, figs, raisin grapes, kiwifruit, olives, Clingstone Peaches, pistachios, dried plums, pomegranates, sweet rice, Ladino Clover seed, and walnuts. Thus, not only is California agriculture an essential industry within the state, but it is an essential contributor to the entire nation’s food supply. (USDA Pacific Regional Field Office, 2015)

In 2013, the average value of California farm real estate was $6,900 per acre, but irrigated land was valued at $11,800 per acre, an increase of 2.9% from 2012 (the drought is causing non-irrigated land to decline in value, but irrigated land to increase in value). The amount of land devoted to farming in California was 25.5 million acres. The total value of the farm land is about $176 billion. (USDA Pacific Regional Field Office, 2015). Direct farm employment in California in 2014 was 417,200, with an unknown number of other workers indirectly dependent on farming (anybody who sells equipment or services to farms or farmers). (Employment Development Department, 2015)

Figure 27: California's 10 most important agricultural counties.

Figure 27: California’s 10 most important agricultural counties.

In 2012, California’s top 10 counties by production were Fresno, Kern, Tulare, Monterey, Merced, Stanislaus, San Joaquin, Kings, Ventura, and Imperial. Seven of them are in the Central Valley. Monterey County is in the Central Coast Region (John Steinbeck’s The Grapes of Wrath was set in Monterey County). Ventura County is in the South Coast Region, just north of Los Angeles. Imperial County is in the Mojave Desert, along the border with Mexico. All of these counties are dry counties – the crops depend on irrigation for survival.

The potential for increased water efficiency in California agriculture is controversial, with estimates varying widely. Theoretical calculations of potential water conservation appear to be large, but the real-world potential appears to be much smaller. For instance, focusing on the San Francisco Bay Delta, a group at the Pacific Institute wrote that up to 3.4 million acre-feet could be conserved via 4 modest strategies: crop shifting, smart irrigation scheduling, advanced irrigation management, and efficient irrigation technology. A group at the Irrigation Training & Research Center attacked the Pacific Institute paper, however. In their opinion, smart irrigation scheduling, advanced irrigation management, and efficient irrigation technology were already widely adopted on California farms. As for crop shifting, they felt that it could not be accomplished because the land was not suitable for the proposed shift, and because it would create increased supply in certain crops without creating increased demand to receive it. In addition, they felt that the Pacific Institute group had completely ignored the economic implications of their recommendations, and had fundamentally misunderstood the way in which practices on individual farms translate into basin-wide water dynamics. (Cooley, Christian-Smith, and Gleik, 2008; Burt et al, 2008.)

Almond trees begin to flower in early spring. Source: USDA Agricultural Research Service.

Almond trees begin to flower in early spring. Source: USDA Agricultural Research Service.

An instructive example of economic implications might involve nuts. Acreage devoted to the production of nuts has exploded in California: pecan acreage increased by 52% in 2013, and almond acreage increased by 33%. They are very profitable: almonds were the second leading commodity in California, and walnuts were sixth. They are a long-term crop, however: nuts grow on trees, and it takes several years before a nut tree begins producing. Thus, farmers have a significant investment of capital and time in their nut groves.

The water needs of nuts are interesting, however. They require almost 1,200 gallons of water per pound to grow (almost 9 times as much as milk, almost 3 times as much as eggs). (Mekonnen and Hoekstra, 2012) They would appear to be a good candidate for the crop shifting strategy recommended by the Pacific Institute group. Shifting, however, would require farmers to abandon their significant capital investment, as well as one of the most profitable crops in all of California.

Complicating this scenario is the arcane system of water rights that exists in most western states, including California. Water rights were established in the 1800s and early 1900s. The basis was first come, first served. The first person on the scene made a claim to withdraw a certain quantity of water from a water source. The second person did likewise, and so on. Over time, the claims accumulated. In wet years, the water resource can supply all of the claims, but not in dry years, there just isn’t enough to go around. In those years, water is not prorated. Rather, the senior claim gets the full allotment. Then the second most senior claim, then the third, and so on until there is no more to distribute. It is a controversial system, but it has existed for a very long time, and it is well established in law. (Wikipedia, Water Right)

The effect of this system is that senior water rights holders get all the water they need during dry years, while junior holders go completely without. In those years, junior holders typically allow some of their fields to lie fallow. But you can’t do that with nut trees; they need water every year, or the trees will die. Thus, junior holders may choose to plant something other than nut trees. But if you are a senior water holder, why would you shift out of nuts? You are likely to get all the water you need, it is very profitable, and if you shift, you’re going to take an economic hit. The only problem for the senior rights holder is if water distributions are cut off entirely.

Easy, inexpensive solutions like those proposed by the Pacific Institute paper are often called “low hanging fruit.” I can’t evaluate whether low hanging fruit is a real opportunity in California, or whether it is largely illusory. I do feel constrained to observe, however, that agriculture has existed in California for many decades, water scarcity has been a problem for equally as long, and California has developed the most extensive water collection and diversion system in the country. The system has been very expensive and very controversial. Given these facts, it seems that claims for easy, inexpensive solutions should be evaluated with caution. Even where water conservation is possible, it seems likely to result in increased operating costs to the farmer, and shifting to less profitable crops. Thus, farm income will be reduced.

Those who advocate increased agricultural water efficiency sometimes point to the example of Israel, a model of desert farming efficiency. Israel’s agricultural accomplishment is, indeed, admirable. However, there are important differences that may make Israel a poor model for California. For one, in Israel they don’t farm all of the various crops that they do in California. For another, it is a very small country: more than 20 Israels could fit in California, almost 3 in the Central Valley alone. Further, it is more densely populated: 4.3 times as densely populated as all of California, and 3.6 times as densely populated as the Central Valley. These differences matter, for instance, because Israel strictly limits the amount of fresh water to farms, making up for it with reclaimed water from urban areas and brackish water. The larger size of California means that infrastructure to supply reclaimed water would have to be much more extensive in California than in Israel. In addition, Israel’s higher population density means that per acre of farmland, there is more urban water available for reclamation. (Israel Export & International Cooperation Institute, 2012)

The California Legislative Analyst’s Office concluded that agricultural water efficiency could conserve about 0.5 million acre-feet of water per year, at a cost of just under $6,000 per acre-foot. (Legislative Analyst’s Office, 2008) That is a tiny fraction of the projected water deficit.

Water deliveries out of the California State Water System were cut off to many farmers in 2014, and the State Water Resources Control Board just announced further cutbacks. Water rights dating as far back as 1903 will be restricted, and restrictions will grow as the summer goes on. (Medina, 2015) The result has been the drilling frenzy discussed in Part 2 of this series, as farmers seek to maintain production by substituting groundwater. How long they can continue to do so is unknown. In Post 2 I discussed the limits of that strategy: it threatens not only to drain the aquifer, but also to harm its ability to hold water when a wetter cycle returns. In addition, a group of farmers has threatened to challenge in court the state’s ability to make such cutbacks. It is hard to believe that California would ask so many of its citizens to endure great hardship so that senior water holders could continue to grow nuts. However, the existing system of water rights is deeply and firmly entrenched in law. Taking water away from senior holders would involve taking away a very important property right. It would be highly contentious, and it is not inconceivable that the Supreme Court would rule in favor of the water holders.

Certainly, California’s agricultural sector can reduce its consumption of water. All that is required is to abandon their fields and stop farming. If this were to be the direction California follows, then the economic consequences would be hard to predict. However, if one simply assumed that, since water consumption would have to be reduced by 67%, then 67% of California’s agricultural production would be lost, and 67% of the farmland would be lost, and it would amount to a loss of $31 billion in annual farm receipts, and $118 billion in farmland, not to mention all the equipment on those farms. About 280 thousand people would be thrown out of work. I don’t know how many of those whose lives are indirectly dependent on farming would become unemployed, but if one assumes that it would be 1/3 as many, then some 372 thousand people would be unemployed in total. That represents about 2% of California’s civilian employment, though the unemployment would be concentrated in the agricultural counties, not spread throughout the state. And finally, farmers usually operate on bank credit. The failure of 67% of the farms in California would create significant strains on the banking system, and the recent Great Recession has shown us how much havoc stress on the banking system can create.

The above paragraph makes it sound like the effects would all occur at once, in one year. If the drought and lack of snowpack continue as they have the last two years, the effects may, indeed, be concentrated into a single year, or two, or three. But if a wetter cycle returns, with the decline in the snowpack occurring gradually through mid-century, then the effects would be more gradual, spread over many years.

In summary, agriculture is the largest consumer of water in California. The sector’s prorated share of the water deficit would amount to slightly more than 2/3 of its current water consumption. While nobody is claiming that the sector can make that big a reduction in water consumption, there are a variety of sources claiming that large improvements in California’s agricultural water efficiency are easily and affordably achievable. However, there is reason for skepticism, and the conclusion of the Legislative Analyst’s Office is that only a very small improvement is achievable.

The alternative would be for a large portion of California’s agriculture to be lost, resulting in loss of income, loss of assets, stress on the banking system, and possibly a 2% increase in unemployment statewide. In addition, the entire United States would feel the effects, as more than 5% of our food supply would be lost, including 22% of our supply of vegetables and melons, and about 46% of our fruits and nuts.

My best guess, and it is mostly a guess, is that if cooperation occurs, then some water conservation will be achievable, more than the amount estimated by the Legislative Analysts Office. However, it will be nowhere the amount needed to cover the projected deficit. I have no idea how the issue of water rights will be resolved, but I expect that it will be highly contentious. I expect that a significant amount of California’s agricultural output will be lost, and a significant portion of its farms will fail and be abandoned. I expect that the effects will ripple through the communities which depend on and support California’s agriculture, causing significant hardship and economic dislocation. Over what period of time all this will occur depends on how the drought continues to unfold, as well as many human factors.


Burt, Charles, Peter Canessa, Larry Schwankl, and David Zoldoske. 2008. Agricultural Water Conservation and Efficiency in California – A Commentary. Unpublished paper. Retrieved online 6/12/15 at http://www.itrc.org/papers/commentary.htm.

California Department of Food and Agriculture. California Agricultural Production Statistics. Web page accessed 6/12/15 at http://www.cdfa.ca.gov/statistics.

Cooley, Heather, Juliet Christian-Smith, and Peter Gleick. 2008. More With Less: Agricultural Water Conservation and Efficiency in California. Oakland, CA: Pacific Institute. Retrieved online 6/12/15 at http://www.pacinst.org/wp-content/uploads/sites/21/2013/02/more_with_less3.pdf.

Employment Development Department. 2015. Industry Employment & Labor Force – by Annual Average. An Excel spreadsheet created 5/22/15 by the Labor Market Information Division of the California Employment Development Department, and downloaded 6/14/15 at http://www.labormarketinfo.edd.ca.gov/LMID/Employment_by_Industry_Data.html.

Israel Export & International Cooperation Institute. 2012. Israel’s Agriculture. Retrieved online at http://www.moag.gov.il/agri/files/Israel%27s_Agriculture_Booklet.pdf.

Legislative Analyst’s Office. 2008. California’s Water: An LAO Primer. Retrieved online at http://www.lao.ca.gov.

Medina, Jennifer. 6/12/15. “California Cuts Farmers’ Share of Scant Water.” New York Times. Retrieved online 6/14/15 at http://www.nytimes.com/2015/06/13/us/california-announces-restrictions-on-water-use-by-farmers.html?ref=earth&_r=0.

Mekonnen and Hoekstra. 2012. “A Global Assessment of the Water Footprint of Farm Animal Products. Ecosystems. 15: 401-415. Downloaded from http://waterfootprint.org/media/downloads/Mekonnen-Hoekstra-2012-WaterFootprintFarmAnimalProducts.pdf.

USDA. “Cash Receipts by Commodity, 2010-2014F.” U.S. and State-Level Farm Income and Wealth Statistics. Economic Research Service. Web data portal accessed 6/12/15 at http://www.ers.usda.gov/data-products/farm-income-and-wealth-statistics/annual-cash-receipts-by-commodity.aspx.

USDA Agricultural Research Service. “Blue Orchard Bee.” http://www.ars.usda.gov/Research/docs.htm?docid=18333.

USDA Pacific Regional Field Office, California. 2015. California Agricultural Statistics 2013 Annual Bulletin. Sacramento, CA: Pacific Regional Field Office, National Agricultural Statistics Service. Available online at http://www.nass.usda.gov/Statistics_by_State/California/Publications/California_Ag_Statistics/2013cas-all.pdf.

USGS. Estimated Use of Water in the United States. County Level Data for 2005. http://water.usgs.gov/watuse/data/2005.

Wikipedia. Water right. Viewed online 6/12/2015 at https://en.wikipedia.org/wiki/Water_right.

Drought in California Part 6: Conserving Water – Population and Environment

This is the sixth post in my series Drought in California. In Part 1: California Climate and Drought, I found that drought is projected to be the “new normal” climate in California. In Part 2: The Status of California’s Current Water Resources, I found that California is already depleting both it’s groundwater and surface water resources. In Part 3: California’s Total Water Deficit, I constructed an overall estimate of California’s future water deficit, concluding that it will be about 25.1 million acre-feet per year, about 39% of California’s current dedicated water supply. In Part 4: The Potential to Procure Additional Ground and Surface Water, I found that a variety of obstacles and problems made it unlikely that California could cover the predicted future water deficit by tapping additional groundwater or surface water resources. In Part 5: The Potential of Desalination, I found that using desalination to cover the projected water deficit was within the realm of conceptual possibility. However, it would involve a massive infrastructure construction program. Whether such a program could be completed within the needed time frame was unknown. Further, desalinating such a large volume of water would have an annual cost roughly equal to 1% of California’s total GDP.

This post will examine the potential for water conservation by limiting population growth and by limiting environmental uses of water. At the beginning of each part, I have noted that there are problems with the type of exercise I’m attempting, and problems with the data and analyses I’m having to use. If you want to read more about them, see the introduction to the series.

The Basics of Water Consumption

Figure 5b: Distribution of the Dedicated Water Supply. Data source: California Department of Water Resources (b).

Figure 5b: Distribution of the Dedicated Water Supply. Data source: California Department of Water Resources (b).

Water consumption gets a bit complex, and one needs a little foundation to understand it. The water literature uses several terms to discuss water use. Total supply is all of the water that comes into the state, by whatever route Dedicated supply is that portion of total supply that is available for human use. Withdrawals refer to water taken from the dedicated supply and used for human purposes. Consumptive withdrawals are used in a way that makes the water unavailable for use in the same water basin. Such a use might involve evaporation, conversion to steam that is lost to the atmosphere, or contamination. Non-consumptive withdrawals return the water to the basin in a way that it can be used again. An example might be irrigation water that either sinks into the ground and then into an aquifer that is tapped by wells, or that flows into a collection pond from which it is used again.

In Part 2 of this series I reported that the California Department of Water Resources estimated dedicated supply to be 65.1 million acre-feet in 2001, a dry year. Figure 5b, repeated from that post, shows the uses to which that water was distributed.

(Click on graphics for larger view.)

Figure 22a. California Water WIthdrawals in 2005, Including Withdrawals for Thermoelectric Generation. Data source: USGS, 2005.

Figure 22a. California Water WIthdrawals in 2005, Including Withdrawals for Thermoelectric Generation. Data source: USGS, 2005.

Total water withdrawals in California during 2005 were about 51.2 million acre-feet per year. About 28% of California water was withdrawn for thermoelectric generation, which parallels findings in other states. Figure 22a shows the amounts by sector, with withdrawals for thermoelectric generation included. Figure 22b shows the same data with withdrawals for thermoelectric generation excluded. With thermoelectric generation excluded, irrigation accounted for about 76% of all water withdrawals in California. Industrial use (including mines) consumed a mere 1%. Domestic withdrawal is water used in homes. The bulk of it is supplied by public water supply companies, but a small amount is self-supplied, as in a home well. Public supply is water delivered by a state certified public water utility. Most of the water delivered for urban use comes from public supply. In 2005 about 57% of publicly supplied water was delivered to homes, with about 43% going to commercial and other uses. (USGS, 2005)

Figure 22b. California Water WIthdrawals in 2005, Excluding Withdrawals for Thermoelectric Generation. Data source: USGS, 2005.

Figure 22b. California Water WIthdrawals in 2005, Excluding Withdrawals for Thermoelectric Generation. Data source: USGS, 2005.

Why have I netted out water withdrawn for thermoelectric generation? Because it is one of those non-consumptive withdrawals discussed above. Nuclear and coal power plants use huge volumes of cooling water. The cooling water is typically returned to the environment. It may cause local problems because it is hot, but it is not usually otherwise polluted. In this sense, it is used, but not consumed.

Could California reduce water consumption by limiting population growth or by limiting the amount of water returned to the environment?

Population Growth

When I constructed an estimate of California’s future water deficit in Part 3, about 3.1 million acre-feet of it was based on population growth. Should the population stop growing, it would reduce the projected deficit by that much. Figure 23 shows California’s decadal population growth rate in blue, and the USA’s in red. California’s rate of growth has declined over time, and between 2000 and 2010, California’s population grew 10%, the same as the USA as a whole. (U.S. Census Bureau (a), U.S. Census Bureau (b))

Figure 23. Decadal Population Growth Rate of California and the United States. Data source: U.S. Census Bureau a and b.

Figure 23. Decadal Population Growth Rate of California and the United States. Data source: U.S. Census Bureau a and b.

To conserve water, California could enact policies to reduce, halt, or reverse population growth. The idea would likely encounter significant resistance, however. Businesses and governments generally assume population decline to be socially and economically destructive, and over the last several decades several countries around the world have taken steps to reverse slowing rates of population growth because of these concerns. (Coleman and Rowthorn, 2011) In addition, policies to limit population growth fairly and equitably would be complex to devise. Some policies, such as the one child policies in China and India, have been oppressive, if not brutal.

It seems unlikely that California will voluntarily enact policies to intentionally limit population growth; it would be extraordinarily controversial. Besides, only 12% of the projected water deficit was based on population growth, and limiting population would do nothing to address the remaining 88%.

I personally believe, however, that the projected water deficit facing California will cause an involuntary reduction in California’s population. I believe that California will become a much less desirable place to live or to locate a business. There will be a net outmigration, just as there was a migration out of the Midwest during the Dust Bowl. This possible scenario will be discussed in more detail in a coming post.

Returning Water to the Environment

The estimate of dedicated supply (65.1 million acre-feet, see Part 2 of this series) is larger than the estimate of net withdrawals by 28 million acre-feet. That’s a lot of water! There are several reasons for the difference. First, supply is different from consumption; the estimates are constructed using entirely different data sets. You wouldn’t expect them to agree perfectly. Second, dedicated supply was estimated for 2001, while withdrawals were estimated for 2005. While both were dry years, it is likely that the total supply was different, and that affected both dedicated supply and withdrawals. Most important, however, is that 35% of the dedicated supply was returned to the environment for environmental remediation purposes. The supply data from the California Department of Water Resources included this water, but the USGS data on withdrawals did not.

From time-to-time I read a proposal that to solve the water deficit, California should simply stop using water for environmental purposes. Of California’s 65.1 million acre-feet of dedicated supply in 2001, some 22.4 million acre-feet of it were used for environmental purposes. That is close to being enough to cover the future deficit I projected.

Figure 24: Sacramento River Delta. The water flows northeast into the delta from the San Joaquin River, and southeast into the delta from the Sacramento River. It flows west to San Francisco Bay, and south across the delta, where it is pumped from the Clifton Court Forebay into the California and Delta-Mendota Aqueducts. Photo by NASA, 2005.

Figure 24: Sacramento River Delta. The water flows northeast into the delta from the San Joaquin River, and southeast into the delta from the Sacramento River. It flows west to San Francisco Bay, and south across the delta, where it is pumped from the Clifton Court Forebay into the California and Delta-Mendota Aqueducts. Photo by NASA, 2005.

There would be problems with this proposed solution, however. For instance, the largest single environmental return is water diverted into the San Francisco Bay Delta. In their natural states, the Sacramento and San Joaquin Rivers provide sufficient flow of fresh water through the delta into San Francisco Bay to prevent ocean water from the bay from intruding into the delta. However, so much water has been diverted from these streams that ocean water threatens to intrude. The water in the California State Water Project that is destined for Southern California is discharged into the delta by the Sacramento River, flows across the delta, and is sucked up by huge pumps on the other side, lifting it into the California Aqueduct, and sending it south. If water were not returned to the delta, salt water would contaminate the water destined for Southern California. Even with water returns, the drought has reduced water flow through the delta to the point that the California State Water System is having to construct an emergency barrier in the delta to prevent salt intrusion. (California Department of Water Resources, 5/29/15)

Figure 25: Satellite imagery shows the shrinking Aral Sea. Source: USGA/NASA; visualization by UNEP/GRID-Sioux Falls.

Figure 25: Satellite imagery shows the shrinking Aral Sea. Source: USGA/NASA; visualization by UNEP/GRID-Sioux Falls.

The situation with the delta is an example of a general principal: water returned to the environment is not wasted, it is used to prevent serious environmental damage. Now, there are places around the world where people have chosen to proceed with unwise water diversions, and they have devastated the environment as a result. Perhaps the Aral Sea is the most dramatic example. Once the world’s fourth largest lake, it has been reduced by water diversion to a small fraction of its former extent. The entire region’s climate has been adversely effected, thousands of square miles of barren salt flats have been created, the regions economy has been devastated, and Kazakhstan has begun an expensive emergency program to try to restore the sea. It has been called one of the world’s worst environmental disasters. (Wikipedia, Aral Sea)

California already over-withdraws water from its rivers, causing environmental damage. Would the state choose to turn itself into another Aral Sea? Would it be allowed to do so? I doubt it. I do not believe that significant additional water can be obtained by taking it from the environment.


Thus, it seems unlikely that California will pursue a policy to voluntarily and intentionally limit population. And it seems clear that California cannot pursue a policy of withdrawing additional water from the environment without serious environmental harm. “Environmental harm,” of course, is a euphemism for some really unpleasant stuff, as they found out around the Aral Sea.

This post was corrected on 8/8/15 to correct an error in Figure 22b.


California Department of Water Resources (b). California State Water Project Water Supply. Webpage accessed 5/21/2015 at http://www.water.ca.gov/swp/watersupply.cfm.

California Department of Water Resources. 5/29/15. Emergency Drought Barrier Nears Completion. News release viewed online 6/12/15 at http://www.water.ca.gov/news/newsreleases/2015/052915.pdf.

Coleman, David, and Robert Rowthorn. 2011. “Who’s Afraid of Population Decline? A Critical Examination of Its Consequences.” Population and Development Review. (37), Issue Supplement s1, 217-248. Retrieved online 6/6/15 at http://www.oisp.ox.ac.uk/fileadmin/documents/PDF/WP57_Who_s_afraid_of_population_Decline__by_David_Coleman_and_Robert_Rowthorn.pdf.

NASA. 2005. Sacramento River Delta. Earth Observatory, 12/2/2005. http://earthobservatory.nasa.gov/IOTD/view.php?id=6070.

U.S. Census Bureau (a). Part II. Population of the United States and Each State: 1790-1990. http://www.census.gov/population/www/censusdata/Population_PartII.xls.

U.S. Census Bureau (b). Table 1. Intercensal Estimates of the Resident Population for the United States, Regions, States, and Puerto Rico: April 1, 2000 to July 1 , 1010. http://www.census.gov/popest/data/intercensal/national/nat2010.html.

USGS. Estimated Use of Water in the United States. County Level Data for 2005. http://water.usgs.gov/watuse/data/2005.

USGS/NASA. Satellite imagery of the Aral Sea. Visualization by UNEP/GRID-Sioux Falls. Downloaded 6/16/15 from http://na.unep.net/geas/getUNEPPageWithArticleIDScript.php?article_id=108.

Wikipedia. Aral Sea. Viewed online 6/15/15 at https://en.wikipedia.org/wiki/Aral_Sea.

Drought in California Part 3: California’s Total Water Deficit

This post is Part 3 of my series on Drought in California. In Drought and the California Climate, published 2 weeks ago, I reviewed the drought California is experiencing, the state’s historical climate, and projections for the state’s future climate. I discovered that drought is expected to become the “new normal” for the state. In The Status of California’s Current Water Resources, published last week, I surveyed California’s current water resources, discovering that California is already experiencing deficits in both groundwater and surface water. Both groundwater and surface water supplies are being depleted. Unless changes are made, the depletion is projected to continue.

This post attempts to construct a summary total of California’s overall water deficit. The estimate is going to be a very rough, “back-of-the-envelope” exercise, that relies on a number of assumptions that may, or may not, be correct. Nevertheless, such an estimate is needed in order to evaluate potential measures to procure additional water supplies and to conserve existing ones. There are surprisingly few published estimates out there. They are uneven in what they include and omit. Indeed, much of the data and the analysis used for this series have problems and limitations. You can read about them in the introduction to the series.

California’s Total Water Deficit

As noted in the previous post, the total water supply for California has been estimated for wet, average, and dry years. Because climate change is expected to cause drought to be the “new normal” in California, the supply during dry years is the one that should be of most interest to us.

In addition, either the total supply or the dedicated supply can be estimated. The total supply is an estimate of every drop of water that falls on the state as precipitation, every drop that is imported in aqueducts from other states, every drop that is desalinated, and every drop that is pumped out of the ground. The dedicated supply is the portion available for human consumption. The not-dedicated water is not surplus; it recharges aquifers, and supports the plants, animals, and fish that live in California. Thus, it is not an untapped water supply available for humans to grab. The dedicated supply is the estimate that is relevant to these calculations. As noted in the previous post, the dedicated supply of water during a dry year is 65.1 million acre-feet. (California Department of Water Resources (b)).

Table 3: California Dedicated Water Supply. Source: California Department of Water Resources (b).

Table 3: California Dedicated Water Supply. Source: California Department of Water Resources (b).

Table 3 at right shows how the dedicated water supply is used in wet, average, and dry years. The table shows that in dry years, the amount of water distributed by the California State Water Project to agriculture and to urban uses actually increases. But the amount distributed to environmental uses decreases by almost 1/3. This is not difficult to understand: they close the sluice gates. More water is held in the reservoirs and diverted into the aqueducts, less flows into the rivers.

(Click on graphics for larger view.)

California currently derives its water from two primary sources: groundwater and surface water. Groundwater comes from aquifers. The largest and most important fresh water aquifer in California is the Central Valley Aquifer. Its status was reviewed in the previous post. As it is the most important aquifer, I will let its deficit stand in for the total groundwater deficit, though it is surely an underestimate. Water storage in the Central Valley Aquifer declined by at least 114 million acre-feet between 1962 and 2014. That is about 2.2 million acre-feet per year. Withdrawals would have to be curtailed by that much to stabilize the aquifer. (May, 2015)

An analysis by the Pacific Institute and the National Resources Defense Council estimates that California diverts 5 million more acre-feet from the Sacramento-San Juan watershed than can be sustained, and depletes up to 2 million acre-feet from that watershed’s groundwater supplies. It is not clear how this study’s estimated groundwater deficit overlaps with the Central Valley Aquifer decline estimated above, but I will assume that half of it does, and the Pacific Institute estimate should be adjusted by that amount. Thus, the overall estimated deficit is 6 million acre-feet. (Pacific Institute and the NRDC, 2014)

The EPA estimates that California’s groundwater deficit in 2010 was 2 million acre-feet per year. Given current trends, population growth in California will result in an additional 6.2 million acre-feet deficit in a drought year. The current deficit of 2 million acre-feet appears to overlap with the estimate by the Pacific Institute, and will not be included further in this calculation. The future estimate appears to be an estimate of increased demand caused by the anticipated increase in population. For many years, California’s booming economy has depended on a growing population, and it seems unlikely that economic interests will want to freeze or reduce it. It seems equally unlikely, however, that the trend can continue unchanged. Thus, because population growth may slow, it may be reasonable to reduce the EPA’s estimated deficit. By how much is not clear, but by 50% may be reasonable. That would be 3.1 million acre-feet. (EPA, 2010)

Neither the Pacific Institute estimate nor the EPA estimate attempts to assess the effects of reservoirs going dry, or of a significant decline in the snowpack. Were Lake Mead to go dry, it would interrupt water deliveries from the Colorado River System. Although the intakes for the aqueducts that deliver the water are in Lake Havasu, if Lake Mead were to go dry, it would disrupt managers’ ability to manage the water level in Lake Havasu, uncovering the intakes. The system provides about 4.4 million acre-feet per year to the state, and this would represent an immediate loss of that supply. For Southern California’s metro areas, it would represent a loss of about 23% of their water supply. The loss of one or more of California’s instate reservoirs would be only slightly less catastrophic. I don’t have an estimate of when that might occur, however, so it will not be included in this calculation. Recall from the previous post that even a 25% reduction in water withdrawals still left a 50% chance that Lake Mead would go dry by 2060. Thus, the draw from the Colorado River would need to be reduced by more than that. How much more is unclear, but again, a 50% reduction seems not unreasonable. That would be 2.2 million acre-feet. (Barnett and Pierce, 2008)

In 2015 the California snowpack was only 5% of its historical average. If this were to become the normal occurrence, it would represent an immediate and existential threat to the state. Not only would runoff into the streams that charge California’s man-made reservoirs be reduced, but water seeping into the ground to recharge the aquifers would, also. However, the 2015 snowpack may be a temporary extreme, and it may be better to accept the National Climate Assessment’s projection of an average 40% decline in the water content of the snowpack (discussed in Part 1). That would amount to 11.6 million acre-feet.

It is difficult to know how to combine this information into an overall estimate of California’s looming water shortage. It seems that only the National Climate Assessment anticipates a decline in water supply based on the decline in the snowpack, and none of the estimates discuss the need to reverse the already-occurring depletion of essential reservoirs.

The estimated deficit in the Central Valley Aquifer is 2.2 million acre-feet per year. The Pacific Institute’s estimate for this same region overlaps with this estimate by about 1 million acre-feet per year, but adds surface water deficits. Adjusting the Pacific Institute estimate to reflect the overlap, the deficit is estimated at 6 million acre-feet per year. These two estimates pertain to only part of the state, the Central Valley. However, that watershed is by far the state’s largest and most important. The aquifer and the two rivers there are the largest within the state. A large part of the excluded area is very dry, and water from the two Central Valley rivers is delivered far and wide across the state. Therefore, these two estimates appears to be a minimum, but reasonable starting point. The EPA’s estimate (adjusted to remove overlap with the Pacific Institute and to anticipate a reduced rate of population growth) represents the increase in demand that would come from an increase in population. It would be 3.1 million acre-feet per year. To prevent Lake Mead from going dry would require a 2.2 million acre-feet reduction. Finally, by far the largest of these potential water deficits would be the decline in the snowpack, which would be 11.6 million acre-feet. (U.S. Global Change Research Program, 2014)

Combined, they sum to a total water deficit of 25.1 million acre-feet, about 39% of California’s dedicated water supply in dry years. Thus, I estimate that to remove its future water deficit, California will need to increase supply and/or reduce demand by more than 1/3.

This estimate is much larger than currently published estimates. The primary reason is that I have included both population growth and the projected effects of climate change. If population growth and climate change trends were to change, it would impact the estimate. In addition, though I remarked on the limitations of this analysis at the beginning, I feel I should restate that the analysis relies on a number of assumptions that may or may not be correct, and on data that is far from perfect.

California can contribute to minimizing the impacts of climate change, but no single state is in control of climate change. California will have to adjust. The estimate constructed above provides one perspective on just how much adjusting they will have to do. In coming posts, I will explore potential strategies for increasing water supply and/or reducing demand.


Barnett, Tim, and David Pierce. 2008. “When Will Lake Mead Go Dry?” Water Resources Research, 44, W03201. Retrieved online at http://www.image.ucar.edu/idag/Papers/PapersIDAGsubtask2.4/Barnett1.pdf.

California Department of Water Resources (b). California State Water Project Water Supply. Web page accessed 5/21/2015 at http://www.water.ca.gov/swp/watersupply.cfm.

EPA. 2010. “California Water Fact Sheet.” EPA WaterSense. EPA832-F-10-016. http://www.epa.gov/watersense/docs/california_state_fact_sheet.pdf.

May, John. 2015. “The Status of California’s Current Water Resources.” Blog post in the blog MoGreenStats. http://www.mogreenstats.com.

Pacific Institute and the National Resources Defense Council (NRDC). 2014. The Untapped Potential of California’s Water Supply: Efficiency, Reuse, and Stormwater. http://pacinst.org/publication/ca-water-supply-solutions/#issuebriefs.

U.S. Global Change Research Program. 2014. Climate Change Impacts in the United States: The Third U.S. National Climate Assessment. http://www.nca2014.globalchange.gov.

Record High Concentrations of Greenhouse Gas

GHG Levels Over TimeIn 2013, the absolute atmospheric concentration of greenhouse gases were 396 parts per million (ppm) for carbon dioxide (CO2), 1,824 parts per billion (ppb) for methane (CH4), and 325.9 ppb for nitrous oxide (N2O). This information comes from the Greenhouse Gas Bulletin issued by the World Meteorological Organization. As shown in the first chart at right, the concentration of each has grown significantly since 1750. The concentrations in 2013 were record highs for all 3. (Some of the charts do not start at zero, to better show the changes that have occurred.)

(Click on chart for larger view.)

Notice how the carbon dioxide and methane lines zigzag up and down each year. This pattern comes from the seasonal change between summer and winter in the northern hemisphere. Plants absorb or emit carbon dioxide and methane differently during summer and winter, and it affects the amounts of these gases in the atmosphere. So much of the earth’s land surface is in the northern hemisphere that the seasonal pattern there outweighs the one in the southern hemisphere. If you want to see a NASA animated simulation of these effects for carbon dioxide, follow this link to:

Radiative Forcinghttps://www.youtube.com/watch?v=x1SgmFa0r04.

The second chart at right shows the radiative forcing from the most important greenhouse gases from 1750 to 2013. (The chart does not start at zero, to better show the change that has occurred). Light blue is carbon dioxide, light green is methane, purple is nitrous oxide, yellow is CFC-12 (also known as Freon), the dark blue band is CFC-11, and the red band is for 15 other GHGs combined. It is easy to see that carbon dioxide produces by far the most forcing, followed by methane.


GHG Abuncance ChartI have provided a third chart at right that shows what percentage of the atmospheric concentration of carbon dioxide, methane, and nitrous oxide have been added to the atmosphere since 1750: about 30% of the carbon dioxide, 60% of the methane, and 17% of the nitrous oxide. In looking at the chart, don’t overlook the fact that the concentration of carbon dioxide is in parts per million, whereas the concentrations of methane and nitrous oxide are in parts per billion.

Methane and Nitrous Oxide have an atmospheric concentrations so much lower than does CO2 – how can they have radiative forcings that can even show up on the same graph as CO2? The answer is that, gram-for-gram, they have much stronger radiative forcing effects.

Carbon dioxide occurs naturally in large amounts. Even so, human activity emits so much that it is overwhelming the preindustrial balance. Methane and nitrous oxide are not uncommon, but in nature they occur in much smaller amounts than does carbon dioxide, and we emit less, also.


World Meteorological Organization Global Atmosphere Watch. 2014. WMO Greenhouse Gas Bulletin. http://www.wmo.int/pages/prog/arep/gaw/ghg/GHGbulletin.html.

1.16 Million Nuclear Generating Plants

Radiative ForcingWorldwide atmospheric greenhouse gas concentrations reached record highs in 2013, according to a report from the World Meteorological Organization. The resulting radiative forcing averaged 2.9 watts per square meter (see chart at right).

(Click on chart for larger view.)

Let me explain. The earth constantly receives energy from the sun, and radiates it back into space. Greenhouse gases trap some of the radiation, holding it in the earth’s atmosphere rather than letting it escape into space. If energy is being absorbed at the same rate, but the rate at which it is radiated back into space is reduced, then the earth will warm. This is the basic theory behind global warming and the concern with greenhouse gases.

The difference between the rate at which the earth radiates energy into space today vs. the rate during pre-industrial times (the year 1750) is called radiative forcing. It represents how much excess energy the earth is holding compared to 1750.

So how much energy is that? Well, the earth is a big place. It’s surface area is 510.2 trillion square meters. At 2.9 watts per square meter, the Earth is holding an excess of 1.48 quadrillion watts of heat (1,480,000,000,000,000).

That’s a big number, it boggles the mind. But what does it mean – how much energy is 1.48 quadrillion watts? We could compare it to train locomotives. The largest locomotives in the world have a power output of about 5,400 kilowatts. Global radiative forcing would be roughly equal to the output of 274 million of them. Even that is such a large number it is hard to imagine, however.

Let’s compare it to the output of nuclear generating stations. We only have one in Missouri, the Callaway Nuclear Generating Station, so let’s use it for our comparison. The output of the Callaway Plant is 1,279 megawatts, so the solar forcing affecting the earth would be roughly equal to 1.16 million Callaway Plants. Imagine covering the earth with 1.16 million nuclear generating stations. (As of May, 2014, there were only 435 nuclear reactors operating around the world.)

Now, let’s break it down a bit. How much of that excess heat should be attributed to the United States? How much to Missouri? The surface area of the USA is 9,857,306 square kilometers. At 2.9 watts per square meter, that yields a total solar forcing of 28.59 trillion watts, the equivalent of 5.9 million locomotives, or 22,353 Callaway Nuclear Generating Stations.

The surface area of Missouri is 180,533 square kilometers. At 2.9 watts per square meter, that represents 523.5 billion watts of solar forcing, the equivalent of 96,944 locomotives, or 409 Callaway Nuclear Generating Stations. The campus of the Callaway Nuclear Generating Station is irregular, but it is roughly 1 mile across north-to-south, half-a-mile across east-to-west. If you kept with those dimensions, and said that each generating station had to have its own campus that size, then they would require a rectangular footprint that stretched from the Missouri-Iowa border on the north to Little Rock on the south, and from Independence on the west to St. Charles on the east.

Some may argue that the radiative forcing is small compared to the total energy budget of the earth, and therefore trivial. I disagree. The fact that it is small compared to the earth’s total energy budget does not make it trivial. If you had a fever of 104°, it would be small compared to your overall energy budget – an increase in temperature of less than 1%. But that would not make it trivial. In fact, it would be life-threatening.

The amount of excess energy represented by radiative forcing is significant, and on a human scale, it is large.

In an upcoming post, I will go into the gases contributing to radiative forcing.


World Meteorological Organization Global Atmosphere Watch. 2014. WMO Greenhouse Gas Bulletin. Accessed 11/21/14 at http://www.wmo.int/pages/prog/arep/gaw/ghg/GHGbulletin.html.

“List of Largest Locomotives.” Wikipedia. Accessed 11/21/14 at http://en.wikipedia.org/wiki/List_of_largest_locomotives.

Nuclear Energy Institute. World Statistics. http://www.nei.org/Knowledge-Center/Nuclear-Statistics/World-Statistics.

“Earth.” Wikipedia. Accessed on 11/11/14 at http://en.wikipedia.org/wiki/Earth.

“United States.” Wikipedia. Accessed 11/12/14 at http://en.wikipedia.org/wiki/United_States.

“Missouri.” Wikipedia. Accessed 11/12/14 at http://en.wikipedia.org/wiki/Missouri.

Unit Juggler. Accessed 11/11/14 at http://www.unitjuggler.com.

Ameren Accounts for 1/3 of Missouri Large Source GHG Emissions

Missouri is finally developing an energy plan. Woohoo! The state was basically forced into it by the new EPA regulations on carbon dioxide emissions from large stationary sources. The largest stationary emitters of greenhouse gas are coal burning power plants, and to comply with the new regulations the state has to develop an energy plan.

There is a certain calculus at work here. The fundamental cause of excessive GHG emissions is us – humans. We like to use energy, and most of the energy we consume is created by burning fossil fuel. We use natural gas to heat our homes and do our cooking. That consumption, however, is widely distributed. The vast majority of buildings have their own furnaces, their own kitchens. We like to drive our cars. That consumption is also widely distributed. US Summ. ChartElectricity, on the other hand, is generated at very large power stations, and it creates lots of GHG emissions. While they are only part of total GHG emissions, it might be possible to achieve reductions by focusing on large power stations and other large industrial facilities.

Nationally, the total amount of GHG emitted from large stationary sources is 3.09 billion metric tons CO2e. Almost 70% of it comes from power plants. All the other sources combined account for less than half as much. (See the first chart at right.)

(Click on chart for larger view.)


MO Summ ChartIn Missouri, large stationary sources emit 89.8 million metric tons CO2e. In this state, fully 82% of it comes from power plants. (See second chart at right.) All other sources combined account for less than 1/4 as much. The second leading sector is minerals, the large mining industry we have in Missouri. It accounts for 12% of large source GHG emissions.

Between 2012 and 2013, emissions from large sources increased in Missouri by 1.4%. The IPCC has estimated that to prevent the worst ravages of climate change, GHG emissions must decrease greatly. We‘re still increasing.

There could be several reasons for Missouri’s extreme concentration of GHG from power plants. It might be a sign that we rely on coal to generate our electricity, and have stubbornly refused to change. It could be a sign that our energy infrastructure is inefficient. Or it might be a sign of how much other industry has fled Missouri. Or it could be a combination.

Table 1 shows the 10 largest single source GHG emitters in Missouri. Nine of them are power plants, 1 is a cement plant.

Table 1: The 10 Largest Single Source GHG Emitters in Missouri (2013).

Facility Parent Company GHG Emissions (MTCO2e) Type
Labadie Ameren Inc. 15,330,245 Power plant
Iatan KCP&L 9,874,198 Power plant
Thomas Hill Associated Electric Coop. 8,084,188 Power plant
New Madrid Associated Electric Coop. 7,390,398 Power plant
Rush Island Ameren Inc. 7,129,195 Power plant
Sioux Ameren Inc. 4,730,255 Power plant
Hawthorn Great Plains Energy 3,682,564 Power plant
Montrose Great Plains Energy 2,958,481 Power plant
Holcim St. Genevieve Plant Holcim Inc. 2,776,115 Cement plant
Meramec Ameren Inc. 2,675,991 Power plant

In terms of corporate responsibility, Ameren Inc. accounts for 1/3 of all large stationary source emissions in Missouri. KCP&L is part of Great Plains Energy. Including KCP&L, Great Plains Energy is second, with 22%, and Associated Electric Cooperative is third, with 18%. Together, these 3 companies by themselves account for 73% of all Missouri large source GHG emissions.


EPA. Facility Level Information on Greenhouse Gases Tool. http://ghgdata.epa.gov/ghgp/main.do. Data downloaded 10/30/2014.

Summary of 14 Missouri GHG Inventories

It has been more than a year since I summarized GHG emissions by Missouri communities, and since then I have reported on 2 additional communities that have completed GHG inventories, University City and Brentwood. In addition, Columbia has updated its inventory. That bring the total to 14, including the State of Missouri itself.

GHG Summary by Sector, Update 2014The chart at right shows per capita emissions. Each column stands for a different community. Within each column, the colors stand for sectors of the community. In all jurisdictions, buildings account for the largest portion of emissions. The built environment is best represented by combining the residential (blue) and commercial (red) sectors. Across the 14 communities, it accounted for between 43% and 87% of per capita emissions.

Several communities have inventoried emissions for more than one year: Missouri, Kansas City, and the City of St Louis all have inventoried emissions in two years, and Columbia has inventoried emissions in three. In my first summary analysis I used the first inventory completed by a community. In this analysis, I have used the most recent one.

The most important factor determining the total amount of GHG emitted is the population of the community. Large communities with lots of people emit more GHG than do small communities with fewer people. I used per capita emissions to adjust for population differences, but I still found significant differences between communities. What accounts for the difference?

The primary answer is change in daytime population. Some communities are primarily residential. They lose population during the day as their residents go off to work and shop in other communities. Other communities have significant commercial sectors. They gain population during the day, as people from other communities come to work and shop. One can compare the daytime population gain (loss) to the residential population to give an indication of the extent to which a community serves as a bedroom community or a commercial center.

Day Pop vs per capita, Update 2014The second chart at right shows per capita GHG emissions plotted against daytime population change. In this graph, if a community has a daytime population gain of, say, 187, that means that its population increases by 187% during the day. If its daytime population loss is -35.3, that means its population decreases by 35.3% during the day. The correlation between per capita emissions and daytime population change is 0.83. Correlation is a statistic used to measure the relationship between two variables. It runs from 1.0, which indicates a perfect relationship, through 0.0, which indicates no relationship, to -1.0, which indicates a perfect inverse relationship. A correlation of 0.83 indicates a strong positive relationship. One caution here: the data for GHG emissions derive from various years between 1990 and 2010, while the percentage change in daytime population is for 2005. (Missouri has been omitted from the chart because it is an entire state. We don’t ordinarily think of large midwestern states serving as bedroom communities for other states.)

Multiple regression is a statistical technique that provides an estimate of the degree to which a set of variables “account” for the variation in a target variable. Using the StatPlus Mac computer program, I constructed a multiple regression of total community GHG emissions on residential population and percent change in daytime population. It showed that residential population and percent change in daytime population accounted for almost all of the variation between these 13 communities in total GHG emissions (r-squared > .99, irrespective of whether I used the data from my original analysis or this one).

Thus, the difference in per capita emissions between communities is mostly a function of their size and the degree to which they serve as a commercial center vs. a bedroom community. With that said, there are clearly some communities in which the opportunity to reduce per capita emissions are greater, simply because there are more per capita emissions.


I have individually reported on each greenhouse gas inventory summarized in this post. See each individual post to find links to the respective GHG inventories. You can find the individual posts by clicking on the “Climate Change” category at the top of the home page.

County populations are from Table 1. Annual Estimates of the Resident Population for Counties of Missouri: April 1, 2000 to July 1, 2009, http://www.census.gov/popest/data/counties/totals/2009/tables/CO-EST2009-01-01.xls.

Municipal populations through 2009 are from Table 4. Annual Estimates of the Resident Population for Incorporated Places in Missouri: April 1, 2000 to July 1, 2009, https://www.census.gov/popest/data/cities/totals/2009/SUB-EST2009-4.html.

Municipal populations in 2010 are from: U.S. Census Bureau. 2012. Missouri: 2020. Population and Housing Unit Counts (CPH 2-27). http://www.census.gov/prod/cen2010/cph-2-27.pdf.

Daytime population changes are from Daytime Population Changes in Missouri Counties and Selected Cities, Missouri Economic Research & Information Center, December, 2005, http://www.missourieconomy.org/pdfs/daytime_population.pdf.

Columbia Emissions Down More Than 14%

Columbia has been one of the most progressive cities in Missouri when it comes to climate change. They were among the first to study their greenhouse gas emissions, and were an early adopter of the U.S. Mayors Climate Protection Agreement. The Columbia City Council passed an ordinance in 2006 committing the city to reducing GHG emissions 7% from 2000 levels by 2012. Columbia became the first municipality in Missouri that I know of to complete an inventory of GHG emissions in three separate years, each 5 years apart: 2000, 2005, and 2010. The most recent update was issued in 2012, though I just became aware of it.

Columbia 2010 Update By Sector Comm. ChartAccording to the update, Columbia’s total emissions grew by 8.61% between 2000 and 2010. However, the city’s population grew by 26.85% during the same period of time. On a per capita basis, Columbia’s emissions declined by 14.39% from 25.39 MTCO2e per capita to 21.74 MTCO2e.

The first chart at right shows community emissions by sector for 2000, 2005, and 2010. The second chart at right shows per capita emissions. In the charts, the “Other” category includes emissions from wastewater and solid waste.

(Click on charts for larger view)

Columbia 2010 Update Per Capita ChartThe data for 2000 and 2005 differ slightly from the data I originally published when I first reported on the Columbia GHG inventory (original post here). The reason is that the new update used improved methods to calculate some of the data, and it standardized the older inventories to the new one. One of the changes involves the use of metric tons of CO2e, where previous inventories used short tons.

In all three years the commercial sector emitted the largest fraction of Columbia’s emissions, followed by the residential and transportation sectors. Across the 10-year period, only emissions from the industrial sector declined, by 15.21%. Transportation emissions increased by 20.90%, residential by 13.10%, and commercial by 10.34%.

If a municipality’s population grows because people moved to the municipality from elsewhere, it may not represent an overall increase in GHG emissions, but rather a relocation of them. However, one cannot be sure without much more analysis, and it brings up a problem that is often omitted in discussing GHG emissions. The amount of GHG emitted per person declined in Columbia, but the effect was overcome by the increase in population. Overall GHG emissions still went up. We (the United States, the World) may make progress in reducing the amount of GHG emitted by each person, but if population continues to grow unchecked, emissions may continue to increase despite our efforts.


Mitchell, James. City of Columbia, Missouri Greenhouse Gas Inventory 2010 Update and Emission Reduction Recommendations. http://www.gocolumbiamo.com/Sustainability/documents/MicrosoftWord-ColumbiaGHG2012FINALREPORT.pdf.

For Columbia’s 2000 & 2005 population: Table 4. Annual Estimates of the Resident Population for Incorporated Places in Missouri: April 1, 2000 to July 1, 2009 (SUB-EST2009-04-29). U. S. Census Bureau. https://www.census.gov/popest/data/cities/totals/2009/SUB-EST2009-4.html.

For Columbia’s 2010 population: State & County QuickFacts, U.S. Census Bureau, http://quickfacts.census.gov/qfd/states/29/2915670.html.

Brentwood Reports GHG Emissions

Brentwood, a suburb of St. Louis, has completed and published a municipal greenhouse gas inventory. The inventory studied community emissions and emissions from government operations for the baseline year of 2010. The latter are a subset of the former, but municipalities break them out separately because they have direct control over their own emissions, while they can only influence community emissions indirectly. Many municipalities also want to demonstrate leadership on the issue.

Brentwood Comm GHG Chart 2010Total Brentwood community emissions were 224,878 metric tons of carbon dioxide equivalent (MTCO2e). According to the report, Brentwood had a residential population of 8,025 in 2010, yielding per capita emissions of 28.02 MTCO2e/person.

The first chart at right shows community emissions by sector. The commercial sector was largest, accounting for over 40% of total emissions. The residential sector and transportation sectors were second and third largest. The streetlight sector represents a few privately lighted streets. The second chart at right shows community emissions by source. Almost 3/4 of Brentwood’s emissions derived from the consumption of electricity. Transportation fuels, gasoline and diesel, together accounted for 16.65% of emissions. Natural gas consumption accounted for only 10.4% of emissions.

(For larger view, click on chart.)

Brentwood Govt GHG Chart 2010Total government GHG emissions were 3,291 MTCO2e, about 2% of community emissions. The second chart at right shows government emissions by sector. The largest portion of emissions was accounted for by energy consumption in the city’s buildings and facilities (65%), which were nearly twice as much as all other sources combined. The vehicle fleet accounted for 13% of emissions, while employee commute accounted for 12%.

Brentwood operates a recreation center with an ice rink. This facility alone consumed 2.2 million kWh of electricity, more than 2/3 of the electricity consumed by all Brentwood government buildings.


Morlen, Ron. City of Brentwood, Missouri, Community and Local Government Operations Greenhouse Gas Emissions Inventory, 2010. As of this writing, this document is not published on the web. Contact the City of Brentwood for a copy.

%d bloggers like this: