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The last post reported on 33 climate trends discussed in “State of the Climate 2017,” a report published in the Bulletin of the American Meteorological Society. This post characterizes the 2017 climate in the United States. Be sure to catch that this is for 2017, not 2018, the year just ended. In what follows, “CONUS” means the continental United States. All anomalies compare to the 1981-2010 average.
The annual average temperature in 2017 for the contiguous United States (CONUS) was 12.5°C or 1.0°C above the 1981–2010 average—its third warmest year since records began in 1895, 0.2°C cooler than 2016 and 0.4°C cooler than 2012. Figure 1 shows a map of 2017 temperature anomaly across the United States. Every state was warmer than average except for Washington. Most of Missouri was 1.0-1.5°C warmer than average (1.8-2.7°F). A few areas were even warmer, but the map isn’t sufficiently detailed to determine for sure which areas they were.
Averaged nationally, precipitation was 104% of average, making 2017 the 20th wettest year in the record. The pattern was variable, however, as shown in Figure 2. In particular, winter precipitation was higher than average, with Nevada and Wyoming each having the wettest winters on record. The California mountains were wetter than average (I reported on the large snowpack in the winter of 2017 in previous posts). So was eastern Colorado-New Mexico. On the other hand, much of the Southwest and the northern Plain States were in drought. It was also dry along the Mississippi River from the Missouri Bootheel into central Iowa.
There were 16 weather-related events in 2017 which resulted in damage of more than $1 billion. That tied with 2011 for the highest number of billion-dollar disasters. The total damages they caused was $306 billion, a new record. Figure 3 shows a map of where they were roughly located. There were three major hurricanes across the southern United States, plus catastrophic fires in California and other western states. Missouri and Arkansas were affected by flooding in late April-early May 2017.
Missouri had 13 fatalities and 155 injuries from weather-related disasters in 2017, and a total of $156.20 million in damages. There have been many years when the Missouri’s weather-related damage has been below $100 million, but in 2011 it was over $3.4 billion.
Blunden, J., D. S. Arndt, and G. Hartfield , Eds., 2018: State of the Climate in 2017. Bull. Amer. Meteor. Soc., 99 (8), Si–S332, doi:10.1175/2018BAMSStateoftheClimate.1. Downloaded 12/15/18 from https://www.ametsoc.org/index.cfm/ams/publications/bulletin-of-the-american-meteorological-society-bams/state-of-the-climate.
Office of Climate, Water, and Weather Services, National Weather Service. 2016. Natural Hazard Statistics. Data downloaded 2/10/16 from http://www.nws.noaa.gov/om/hazstats.shtml#.
The IPCC report Global Warming of 1.5°C, and the Fourth National Climate Assessment were not the only climate related reports to be published in the second half of 2018. The American Meteorological Society also published its annual report on the climate, State of the Climate in 2017. Rather than a document assessing the effects of climate change, this documents presents a comprehensive picture of what the climate was like in 2017.
Figure 1 shows in a single graphic the major climate variables that are discussed in the report. I will discuss each very briefly in order, going down each column before moving to the next column. I’ve made the chart to open in a separate browser tab, and you should be able to refer back and forth between my comments and the charts. In the charts, some of the data is shown as anomalies rather than as raw values, and in those cases, the reference period is given in the chart.
Charts (a) and (b) show the level of polar ozone, the 1st in March, the 2nd in October. This ozone is high-altitude ozone, and it is essential for blocking ultraviolet rays, too much of which are harmful. These charts concern the famous ozone hole of the 1980s. In general, the level in March bottomed in the 1980s, partially rebounded, but has again been trending downward. In October, the level bottomed in the 1980s and has been largely moving sideways since then.
Chart (c) shows the average surface temperature in the arctic. It has obviously been warming, some 3°C since the 1950s.
Chart (d) shows the average surface temperature of the whole earth. It has been warming, but not as much as the arctic. The recent several years show a steep spike upward.
Chart (e) shows temperature in the lower troposphere. This is the lowest layer of the earth’s atmosphere, and it is where almost all life occurs, as well as almost all weather. It has been warming, and you can see the same spike in recent years.
Chart (f) shows the temperature in the lower stratosphere. This is the next higher layer of the atmosphere. Near the equator it begins some 66,000 feet up, while at the poles it is lower, some 23,000 feet up. The temperature here has been cooling. I have seen some arguments that the cooling in the stratosphere compensates for the heat in the troposphere. This is like saying that cool weather in San Francisco means people can’t be dying from a heat wave in Chicago. Sorry, but it doesn’t mean any such thing.
Chart (g) plots the number of warm days (solid line) and cool nights (dotted line). Warm days have been increasing, and cool nights have been decreasing.
Chart (h) shows the area covered by arctic sea ice. The maximum is the solid line, the minimum the dotted line. Both have been decreasing, the minimum more severely.
Chart (i) shows antarctic sea ice. The variability between years has grown significantly, and the general trend appears to be increasing.
Chart (j) shows a measure of the amount of water locked-up as ice in all of the world’s glaciers. It has been declining at a significant rate. It will have implications for anyone and anything dependent on glaciers and/or glacial melt for water.
Chart (l) shows the amount of water vapor in the lower stratosphere. It is quite variable, but the trend appears to be toward slightly higher amounts of water vapor.
Chart (m) shows the level of cloudiness across the planet. There are several data sets. The trend appears to be towards convergence, with a slightly downward slope for at least some of the data sets.
Chart (n) shows the amount of water vapor in the entire atmosphere, top to bottom, over land. It has been increasing.
Chart (o) shows the amount of water vapor in the entire atmosphere, top to bottom, over the ocean. It, too, has been increasing.
Chart (p) shows the specific humidity in the upper troposphere. It appears to be declining slightly.
Chart (q) shows the specific humidity over land. It has been increasing. Specific humidity is not the humidity statistic we are used to, that is relative humidity (see below). The specific humidity is a measure of the mass of water vapor in an air sample compared to the mass of the other air in the sample.
Chart (r) shows the specific humidity over the ocean. It, too has been increasing.
Chart (s) shows relative humidity over the land. It has been decreasing. Relative humidity is a measure of the amount of water a sample of air is holding, compared to the maximum it could hold. Air’s ability to hold water increases with temperature, so it is possible for relative humidity to decrease, even while specific humidity increases, if the temperature rises.
Chart (t) Shows relative humidity over the ocean. It has been mostly moving sideways, but perhaps decreasing slightly.
Chart (u) shows the amount of precipitation over land. It moved mostly sideways until the 1980s, at which point it appears to have increased. The recent years have seen a significant spike upward.
Chart (v) shows the Southern Oscillation Index. This is a measure comparing air pressure in the western and eastern South Pacific. It tracks the El Niño phenomenon, with negative values indicating an El Niño, and positive values indicating a La Niña. I see no obvious trend in the data.
Chart shows the amount of heat the ocean is holding. The amount of heat is not the same as the temperature: a 100° pot of water holds much more heat than a 100° pot of air, though both are the same size. The heat content of the oceans has bee increasing.
Chart (x) shows a measure of sea level. It has been rising. The scale is in millimeters, so the chart shows about a 6-inch rise.
Chart (y) shows the tropospheric ozone level in the tropics. It has been increasing. This is not the same as arctic ozone levels, which are measured in the stratosphere, where they help to block ultraviolet light from striking the earth. This is ground level ozone, a harmful pollutant. It is the ozone I track when I report on the Air Quality Index.
Chart (z) shows a measure of the speed of the wind in the troposphere. It has been increasing slightly.
Chart (aa) shows a measure of the speed of the wind over land. It has been decreasing.
Chart (ab) shows a measure of the speed of the wind over the ocean. It has been increasing.
Chart (ac) shows the amount of biomass being burned each year. It has been deecreasing.
Chart (ad) shows a measure of soil moisture across the earth. It has been moving sideways, a surprise to me, as I would have expected increased temperatures to dry the soil.
Chart (ae) shows terrestrial water storage. Though the data series is short, it appears to be declining. This variable concerns fresh water, and reflects ice sheets, glaciers, and lakes. Its decline is a matter of concern for all people, animals, and plants that depend on stored water.
Chart (af) shows global FAPAR. FAPAR is the amount of solar radiation available for absorption by plants during photosynthesis that actually gets absorbed. Though the data series is short, it was declining, but in recent years it has increased.
Chart (ag) shows the albedo of the land surface. Though the data series is short, it appears to be decreasing. Albedo is the reflectivity of the earth. High albedo means most of the light is reflected. Low albedo means most of the light is absorbed, causing the surface to warm. Black paint has a low albedo, white paint has a high albedo.
Blunden, J., D. S. Arndt, and G. Hartfield , Eds., 2018: State of the Climate in 2017. Bull. Amer. Meteor. Soc., 99 (8), Si–S332, doi:10.1175/2018BAMSStateoftheClimate.1.
In my previous post I reported on the 4th National Climate Assessment, Volume 1. That volume deals with the natural science findings. Volume 2 deals with how climate change is projected to impact the United States, and with mitigation and adaptation. Unlike reports by the IPCC, the National Climate Assessment focuses on the United States. As with all of the IPCC and NCA reports, the 4th National Climate Assessment is far too large and substantive to fully summarize in a brief blog post. What follows is a selection of a few of the findings.
Figure 1 projects U.S. economic damage from climate change in 2090 under the low emission scenario (RCP 4.5) and the high emission scenario (8.5). The intangibles that make life worth living, what we call quality of life, are not easy to put a dollar value on, and this chart does not address them.
In the chart, the columns represent various sectors of the economy. The blue portion represents the damages under RCP 4.5, while the whole column represents the damages under RCP 8.5 Thus, the orange portion represents the difference between the two. The largest economic damages come from 3 sectors: Labor, Extreme Temperature Mortality, and Coastal Property. In addition, in most of the sectors, the damages under RCP 8.5 are more than twice the damages under RCP 4.5.
(Click on chart for larger view.)
Figure 2 shows projected carbon emissions, temperature change, and U.S. economic damage from climate change under various emission scenarios. The left side of the chart shows that observed carbon emissions are following the high scenario, and there is no evidence that they are suddenly about to revert to the low emission scenario. The right side shows that the high emissions scenarios lead to larger increases in temperature and correspondingly larger damages to the U.S. economy.
The Overview of the report summarizes some of the specific risks the USA faces from climate change. It is quite a list, but it puts real form to projections that often are statistical or vague. To paraphrase:
- Rising sea levels, higher storm surges, and increased high tide flooding will impact coastal infrastructure, damaging electrical and natural gas supply lines, and causing problems with access to goods from overseas. About $1 trillion in coastal property will be impacted. Coastal cities will experience daily flooding.
- Wildfire in the West will increase, damaging ranches and rangelands; increasingly it will damage property in cities and take human lives. Energy transmission and production will be damaged.
- Thawing permafrost in Alaska will damage roads and buildings, including oil and gas operations. This will be partially offset by a longer ice-free season.
- Yields of major U.S. crops (corn, soybeans, wheat, rice, sorghum, and cotton) are expected to decline due to higher temperatures and changes in water availability, disease, and pests. These will percolate through the economy, resulting in less availability of agricultural products, and increased prices.
- Human productivity equal to almost 2 billion labor hours is expected to be lost annually due to extreme temperatures, resulting in an estimated $160 billion in lost wages. States in the Southeast and Southern Great Plains are expected to be impacted hardest.
- Fresh water quality and quantity are threatened by rising temperatures, reduced mountain snowpack, sea level rise, saltwater intrusion, drought, flooding, and algal blooms. In some places, the availability of safe and dependable water will be threatened.
- Hydropower supplies are expected to decrease as a result of changes in mountain snowpack.
- Drought will impact oil and gas drilling and refining, all of which use water intensely.
- Tourism will be impacted by changes in snowpack and wildfire. Communities dependent on tourism will be impacted.
- Air quality will be impacted by higher temperature, higher humidity, and increased smoke from wildfires. Reduced air quality is expected to adversely impact human health.
- Species already are, and will continue, to shift their growing ranges and growing seasons in response to climate change. Mismatches between species and the availability of the resources they need to survive are expected to occur. Extinctions and transformative impacts on some ecosystems are expected.
- Heavy-to-severe coral bleaching is expected to onset across most of the Hawaiian Islands, Guam, and American Samoa by the late 2030s. This will impact fisheries yields and tourism. (Paradise Lost – where’s John Milton when you need him?)
- Rising temperatures are expected to increase illness and death (especially among older adults, pregnant women, and children), partially (but only partially) offset by a reduction in cold-weather deaths.
- Rising temperatures are expected to reduce electricity generation capacity while simultaneously increasing demand for it and its costs. Power outages and blackouts are expected to increase, and household budgets will be strained. Marginal populations and the economically disadvantaged will be impacted even more severely.
- Rising temperatures are expected to threaten human health by promoting the growth of foodborne and waterborne pathogens. Diseases like Lyme disease, West Nile, chikungunya, dengue, and Zika are expected to spread and become more common.
- Every armed service (but especially the Navy, Marines, and Coast Guard), has many bases located in coastal regions. They are expected to be threatened by climate change, and in some cases made unusable. Many of the transportation routes between these bases are similarly located in coastal regions and may become unusable. Thus, climate change is expected to become a significant challenge to the national security apparatus of this country.
- All of the above expected effects of climate change are expected to cause increased stress, leading to increased rates of stress-related diseases, including mental illness.
In terms of mitigation and adaptation, the report states that power sector emissions were 25% below 2005 levels in 2016, the largest emissions reduction for a sector of the American economy over this time. This decline was in large part due to increases in natural gas and renewable energy generation, as well as enhanced energy efficiency standards and programs. Under continued business-as-usual projections, U.S. carbon dioxide and other greenhouse gas emissions show flat or declining trajectories over the next decade with a central estimate of about 15% to 20% reduction below 2005 levels by 2025. (While it is great that U.S. emission have declined, worldwide emissions continue to increase.)
The report notes that efforts to adapt to climate change and to mitigate its effects have increased across the country, but are not even close to adequate. Adaptation is an issue for local planning, as it must take into account both the specific damages anticipated in the locale and many local characteristics such as topography, local water supply, etc. Mitigation follows pathways that are more common across different locations. Figure 3 shows is a map showing the number of GHG mitigation policies in place in each state, by type of policy.
The fact that Missouri has mitigation policies in place does not necessarily mean that GHG emissions have substantially decreased. I last reported on state GHG emissions using data from 2013. At that time, Missouri’s GHG emissions from fossil fuel were still above their level in 2000. Figure 4 republishes a chart from that post showing GHG emissions over time from Missouri and some neighboring states.
The document contains a great deal more than I can report in this post. Those who are interested can follow the link in the Sources section below to the original document. The whole document is available as a single download, or you can download individual chapters.
USGCRP, 2018: Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, Volume II [Reidmiller, D.R., C.W. Avery, D.R. Easterling, K.E. Kunkel, K.L.M. Lewis, T.K. Maycock, and B.C. Stewart (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, 1515 pp. doi: 10.7930/NCA4.2018. Downloaded 12/5/2018 from https://nca2018.globalchange.gov.
The National Climate Assessment is the official United States Government report on climate change. The most recent assessment is the 4th one. It was issued in 2 volumes, the first of which was published in November, 2017. It focuses on the science of climate change and the changes that are likely to occur. The second volume was published in October, 2018. It focuses how the changes outlined in Volume 1 are projected to impact our country, and on some perspectives on adaptation.
In the remainder of this post, italics represent direct quotes from the Executive Summary of Volume 1. In parentheses, I give the page of the report where the quote can be found.
Global annually averaged surface air temperature has increased by about 1.8°F (1.0°C) over the last 115 years (1901–2016). This period is now the warmest in the history of modern civilization. (p.1) In Figure 1, the chart on the left presents a graph of the increase in temperature. The map on the right shows how the change in temperature is distributed across the world.
(Click on chart for larger view.)
The last three years have been the warmest years on record for the globe. These trends are expected to continue…(p.1) Figure 2 maps the projected increase in temperature across North America at mid- and late-century under a low emission scenario and a high emission scenario. I favor the high emission scenario, because I see no sign we are slowing GHG emissions. The high emission scenario shows the average yearly temperature rising by 4-6°F in Missouri by mid-century. By the end of the century, some regions of the country will experience temperature increases of 8-10°F.
Human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century. (p.1) There is no convincing alternative explanation. See the previous post for some comments on climate change denial.
Global average sea level has risen by about 7–8 inches since 1900, with almost half (about 3 inches) of that rise occurring since 1993. (p.1)
Global average sea levels are expected to continue to rise—by at least several inches in the next 15 years and by 1–4 feet by 2100. A rise of as much as 8 feet by 2100 cannot be ruled out. (p.2) Figure 3 shows historical and projected sea level rise across 2 time scales – the upper chart goes back to 500 BCE. The lower chart goes back to 1800. The upper one especially shows that the increase in sea level is unprecedented in human history. The different colored lines in the lower chart represent projections from different future emission scenarios – high (red) to low (blue).
The incidence of daily tidal flooding is accelerating in more than 25 Atlantic and Gulf Coast cities. (p.2) Figure 4 shows the historical and projected incidence of minor tidal flooding in Charleston SC, and San Francisco CA. Minor flooding is also called nuisance flooding. Basically, it is flooding that occurs only at high tide, and is limited to a couple of feet. But it is defined differently at different locations. For an article explaining it all, see here: https://www.climate.gov/news-features/understanding-climate/understanding-climate-billy-sweet-and-john-marra-explain. The charts show that flooding is on the increase, though in San Francisco, the increase is small (also typical of other West Coast locations). It is much larger in Charleston (also typical of other East Coast locations). In both locations, minor flooding is expected to increase, and under the high emission scenario, which is the one we seem to be following, it will nearly become a daily event.
Heavy rainfall is increasing in intensity and frequency across the United States and globally and is expected to continue to increase. The largest observed changes in the United States have occurred in the Northeast. (p.2) Figure 5 shows the historical change in heavy precipitation events across the United States. It shows the data in several forms. The map at upper left shows the percentage change in the largest 1-day rainfall event over rolling 5-year periods. The map at upper right shows the percentage change in the number of days that fall in the 99th percentile of 1-day precipitation over the historical record. The map at lower left shows the percentage change in the number of 2-day precipitation events that exceeded the largest 2-day amount that is expected to occur, on average, once every 5 years, from 1901-2016. The map at lower right shows the number of 2-day precipitation events that exceeded the largest 2-day amount that is expected to occur, on average, once every 5 years, from 1958-2016. Thus, the two lower maps show identical data, except the reference period in the left one stretches back to 1901, while the reference period in the right one stretches back to 1958. (This is all a bit complicated, but it is necessary because the amount of precipitation that constitutes a heavy event may be different in, say, Seattle vs. Las Vegas. You just have to unpack it slowly, and it all makes sense.)
The trend in Figure 4 is strongest in the eastern part of the country, where the increase is large, no matter how you count the data. In the Southwest, however, the data is equivocal. That region may be getting heavier 1-day storms, but heavy precipitation is not lasting over 2 days as frequently as it used to.
Heatwaves have become more frequent in the United States since the 1960s, while extreme cold temperatures and cold waves are less frequent. (p.2) I have written previous posts on how the increase in temperature could lead to deadly heat waves. One series of posts starts here. Another article is here.
The incidence of large forest fires in the western United States has increased…and is expected to further increase…with profound changes to regional ecosystems. (p.2) I’ve written quite a number of posts about how fire is increasing in the West, and how that may contrast with Missouri. See here and here.
Earlier spring melt and reduced snowpack are already affecting water resources in the western United States…Long-duration hydrological drought is increasingly possible before the end of this century. (p.2) I’ve covered this extensively in my posts on the water situation in California and made a number of updates. The original series of posts is here. The most recent update is here.
The magnitude of climate change…will depend primarily on the amount of greenhouse gases (especially carbon dioxide) emitted globally…With significant reductions…the increase in annual average global temperature could be limited to 3.6°F (2°C) or less. (p.2)
The global atmospheric carbon dioxide (CO2) concentration has now passed 400 parts per million (ppm), a level that last occurred about 3 million years ago, when both global average temperature and sea level were significantly higher than today. (p.2)
Continued CO2 emissions would lead to an atmospheric concentration not experienced in tens to hundreds of millions of years. (p.3)
In 2014 and 2015, emission growth rates slowed as economic growth became less carbon-intensive. A recent report, however, suggests that in 2018, the rate of emissions reversed, surging ahead at an accelerating rate. (Le Quéré et al, 2018)
The next post will focus on Volume 2 of the National Climate Report.
U.S. Global Change Research Program. 2017. Climate Science Special Report: Fourth National Climate Assessment, Volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart, and T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, 470 pp, doi: 10.7930/J0J964J6.
Le Quéré, Corinne, and 76 other authors. 2018. Global Carbon Budge, 2018. Earth System Science Data, 10, 2141-2194. Downloaded 12/8/2018 from https://doi.org/10.5194/essd-10-2141-2018.
I ended my last post by noting that if we are to avoid devastating the planet and ourselves through climate change, drastic action is needed immediately. If you ask me, that’s been clear for a long time, but the truth has been denied by climate change deniers. Climate change deniers dislike the word “denial” because it comes from the psychological mechanism of denial, like addicts who deny that they have an addiction.
Perhaps climate change deniers do have an illness like addiction, or perhaps it is something even worse.
In a recent OpEd, Paul Krugman compares the denial of climate change to the denial that cigarette smoking is harmful. According to him, tobacco companies knew for decades that smoking was harmful, but undertook a cynical campaign to try to discredit the science around smoking. Why? Money. They were willing to let hundreds of thousands die in order to preserve profits. The denial of climate change, he says, has been undertaken by fossil fuel companies for precisely the same reason, using precisely the same tactics (and, in fact, using some of the same organizations to conduct the campaign). He also gives a nod to mistrust of government regulation, which will be required to address climate change (while also poking fun at it, noting that their mistrust somehow manages to allow governments to force consumers to subsidize coal. Thus, the real motivation is reduced back to money.) Krugman concludes that this is not just misguided, it is depraved.
The amazing thing is that their nonsense has taken hold of an entire political party (the Republicans) and a great number of people in this state (Missouri). It reminds one of how Naziism took hold of a large number of people in Germany during the 1930s. We look back and ask how rational people could have believed such obvious nonsense, such vile evil? Could such things happen in the USA? Well, try reading The Paranoid Style in American Politics for a starter. Of course it could.
The climate change deniers I have known fall into two camps. Some are simple people who are just repeating what they have heard their neighbors say, or what they have seen in the conservative media they like to follow. Others are more informed. These deniers like to see themselves as skeptics, but to me they seem pervasively suspicious, oppositional, and perhaps even querulous. They are preoccupied with unjustifiable doubts, often seeing conspiracies where none exist. They focus on details or outright fabrications to prop up their denial, while ignoring vast amounts of fact, upon which they turn their back. Because not everything is known, they argue that nothing is known.
I received an email from one, a British lord no less, who comfortably turned his back on thousands of scientific references in an IPCC report, in favor of a column written by the host of an Australian children’s TV show. Well, he claimed, climate science is a vast conspiracy.
Is that paranoia? Has it gone so far as to be a psychotic delusion? Were the German people who supported Naziism deluded? Psychotic? At what point does fear of the future – I’m fearful, too, it would be silly not to be – turn into suspicion and paranoia?
Well, this IPCC report makes it clear that global warming, if left unchecked, is going to cost hundreds of billions of dollars yearly, and is going to ruin the lives of hundreds of millions. Clinging on to denial in the face of such facts, Krugman writes, is depraved. It is no longer a viable intellectual or political position, he argues, it is a sign of depravity.
Drastic change is required immediately if we are to avoid terrible damage to our planet. Even in only economic terms, the projected damage if we do nothing is absolutely staggering. But in addition to that, the lives of hundreds of millions will be ruined. Can humankind respond with the kind of immediate, large-scale planetary change that is required, or is it already too late? Will we act, or have we sold ourselves out to the forces of depravity?
Hofstadter, Richard. 1996. The Paranoid Style in American Politics, and Other Essays. Cambridge, MA: Harvard University Press. Originally published in 1952.
Intergovernmental Panel on Climate Change. 2018. Global Warming of 1.5°C (Draft). Downloaded 11/24/2018 from https://www.ipcc.ch/report/sr15.
Krugman, Paul. “The Depravity of Climate-Change Denial.” The New York Times, November 26, 2018. Viewed online 12/1/2018 at https://www.nytimes.com/2018/11/26/opinion/climate-change-denial-republican.html.
In the previous post, I reported that the recent IPCC report, Global Warming of 1.5°C, concludes that it is theoretically possible to limit global warming to 1.5°C, but it would require drastic change: a 50% reduction in GHG emissions by 2030, and zero net GHG emissions by 2050. In this post, I will discuss some of what the report says about making such a change.
The IPCC reviewed a number of computer models to explore scenarios that limited global warming to 1.5°C. Assumptions varied between the models, and they consequently yielded different results. They can be grouped into several categories: models that projected an increase in Global Mean Surface Temperature (GMST) that stayed below 1.5°C, models that projected a small overshoot of 1.5°C (eventually returning to 1.5°C), models that projected a large overshoot of 1.5°C (eventually returning to 1.5°C), models that projected a 2.0°C increase in GMST, and models that projected a large increase above 2.0°C.
According to the report, limiting the increase in GMST to 1.5°F would require putting a substantial price on carbon emissions. Estimates vary widely, thus, there is substantial uncertainty about just how large the price increase would need to be. It is clear, however, that the smaller the increase in GMST, the higher the price would have to be, and in all cases, the price would need to rise over time. Figure 1 shows the findings. The required price of carbon emissions is on the vertical axis, and the year is on the horizontal axis. The different colored columns represent the categories defined in the preceding paragraph.
The projected price for 2030 ranges from $135 to $5500 per metric ton of CO2e. The projected price in 2050 ranges from $245 to $13,000 per metric ton of CO2e. For comparison, at 11:22 a.m. CST on 12/4/18, Bloomberg reported the current price for emissions on the European Emissions Exchange was €20.72 ($23.48). Thus, the estimate for 2030 ranges from about 6 to 234 times the current price. I don’t know if fossil fuel prices would increase equally, but you can be sure they would increase a lot!
Carbon pricing, however, would not be sufficient in and of itself, and other policies would be required. The strategies mentioned in the report include using less energy, converting electricity generation to methods that don’t release carbon dioxide, converting all fuels to types that don’t release carbon dioxide, converting all energy end use to use decarbonized electricity (e.g. electric cars that run on renewable electricity), and some form of carbon sequestration. This is an intimidating list of changes. It would involve transforming basically all of our energy use infrastructure.
I couldn’t find an estimate of the cost of making the required transformation.
IPCC also doesn’t make specific predictions about the consequences of unchecked global warming, such as “Miami will flood,” or “400 million people will die of famine.” Rather, they speak of threats, how many people will be exposed to them, and which natural systems will be impacted. Figure 2 shows that for all of the systems considered, the threat increases the higher GMST goes. The increase in GMST is shown on the vertical axis. In the columns, white means the system will not impacted. Yellow means it will be impacted moderately. Red indicates that the impact will be severe and widespread. Purple indicates that the impacts will not only be severe, but perhaps irreversible, and also that the ability to cope with and adapt to the change will be limited. It is easy to see that for all systems, the risks increase as global warming increases. Some of the systems enter the red or purple color at or below 1.5C. But many of them only turn red or purple between 1.5 and 2.0°C.
The consequences are dramatic. The report discusses the specifics at great length, and they are far too numerous and complex to try to summarize here. However, I will say that the reports quotes estimates that, if no policy is instituted to limit global warming, GMST would rise 3.66°F by 2100, and it would reduce global Gross World Product (GWP) by 2.6%. According to the CIA World Factbook, GWP in 2017 was $127.8 trillion. Thus, even if GWP does not grow over time, a 2.6% reduction would equate to $3.3 trillion. In comparison, limiting global warming to 2°C would result in a decrease in GWP of 0.5% ($639 billion), and the 1.5°C scenario would result in a reduction of 0.3% ($383 billion).
Thus, the damage associated with global warming increases dramatically the more it warms. Limiting climate change to 1.5°C compared to 2.0°C would prevent $256 billion in economic loss every year. Thus, over a 10-year period, if you spent $2.5 trillion on climate change prevention, it would still be justifiable on the basis of avoided damage. A few trillion dollars here, hundreds of billions of dollars there – pretty soon, it will add up to real money!
The report includes population projections in its modeling of future climate change: increasing the population increases GHG emissions, and hence, it increases future climate change. The report does NOT address, however, limiting population as a strategy for limiting climate change, and least I could not find a section that did. Hmm! (If it’s there and I missed it, please let me know in a comment.)
The report is based on more than 6,000 scientific references. It contains a great deal of information, far too much to adequately summarize here. It should make clear, however, that the denial of climate change is no longer viable. If you ask me, it’s been clear for a long time, but this is pretty definitive.
Drastic change is required immediately if we are to avoid terrible damage to our planet. Even in only economic terms, the projected damage if we do nothing is absolutely staggering. Can humankind respond with the kind of immediate, large-scale planetary change that is required, or is it already too late?
Bloomberg.com. Markets: Energy. Viewed online 12/4/2018 at https://www.bloomberg.com/energ.
Central Intelligence Agency. 2018. The World Factbook 2016-17. Viewed online 11/30/2018 at https://www.cia.gov/library/publications/the-world-factbook/index.html.
Intergovernmental Panel on Climate Change. 2018. Global Warming of 1.5°C (Draft). Downloaded 11/24/2018 from https://www.ipcc.ch/report/sr15.
Can we limit global warming to 1.5°C? What would it require? Would there be real advantages compared to letting earth’s climate warm more than that? These are the questions that the Intergovernmental Panel on Climate Change (IPCC) Special Report 15, Global Warming of 1.5°C seeks to answer. IPCC is, of course, discussing human-induced global warming, not natural climate change. I will discuss their answer to the first question in this post, and the other two questions in the next post.
Let’s start by understanding what we can expect from this report.
Figure 1 shows an image of something. It appears to be something white. It is too far away and out of focus to see more. Figure 2 moves a little closer. Now it is possible to see that that it is a white rectangle with some gray smudges on it.
Figure 3 moves a little closer. You can’t see the whole of the white rectangle, but the gray smudges can now be seen to be a word: “Titanic.” But the writing is still out of focus. Figure 4 moves a little closer still, and the writing is now in clear focus.
Over the years, the IPCC has issued a series of reports on global warming/climate change. Over that time, the basic understanding of global warming has not changed. But as we have gotten closer, it has come more clearly into focus, and it has become possible to make out details that we couldn’t see before. We still don’t have global warming in full focus; we’re not to Figure 4 yet. But it has become possible to ask specific questions and give answers that, while not yet fully specific and detailed, are getting there. So, Global Warming of 1.5°C doesn’t contain radical new understandings. Rather, it is more detailed, and that is useful.
By the way, I chose the word “Titanic” on purpose. That ship was not built to survive a catastrophic iceberg strike, substandard steel may have been used to construct her, and she didn’t have enough lifeboats for all of the passengers. The captain denied the risk and sailed through the night into an iceberg field. By the time the iceberg was spotted dead ahead in the middle of the night, it was too late to turn and too late to stop. By that point, nothing they could do could change their fate: the Titanic was going to hit that berg and sink, and thousands were going to die.
Did I really write that? That’s really catastrophic, apocalyptic even! According to the IPCC report, we are very, very close to being like the Titanic. It may already be too late, but perhaps if we try really, really hard, it isn’t. Read on.
Human activity has already caused our planet’s global mean surface air temperature (GMST) to warm approximately 1°C (1.8°F) since pre-industrial times, according to the report. GMST is increasing by about 0.2°C (0.36°F) per decade. The rate of warming appears to be increasing. Figure 5 shows the temperature trend. The gray line shows the monthly temperatures in the datasets. The orange line shows the change forced by both humans and nature combined, while the yellow line shows the change forced by human activities alone (it is hard to see because it is embedded in the yellow band, look closely) .
GMST is an average across the globe. Some regions have warmed more than others. For instance, the temperature over land has increased more than the temperature over water; 40-60% of human population lives in regions that have already warmed 1.5°C (2.7°F) or more. Thus, a 1.5°C increase in GMST implies a larger than 1.5°C increase over land, with a smaller increase over the ocean.
Past emissions (through 2017) are probably not sufficient to cause GMST to increase more than 1.5°C. Therefore, warming limited to 1.5°C is theoretically possible if human emissions are immediately reduced. Two ways in which the 1.5°C limit could be achieved are discussed in the report. One reduces GHG emissions sufficiently quickly so that the 1.5°C limit is never exceeded. The other would allow a small overshoot of the limit, with temperature then being brought back within the limit by removing carbon dioxide from the atmosphere.
To limit the increase of GMST to 1.5°C with no overshoot would require GHG emissions of no more than 25-30 billion metric tons of CO2e per year in 2030 (compared to estimates that under business as usual they will be 50-58 billion metric tons per year). And GHG EMISSIONS WOULD NEED TO DECLINE TO NET ZERO BY 2050. That’s right – no net GHG emissions by 2050. Figure 6 shows the reductions over time in emissions of CO2, methane, black carbon (soot), and nitrous oxide consistent with a 1.5°C increase in GMST.
The no-net-emissions requirement could be met by two strategies: the first would involve reducing emissions themselves. Reducing emissions at this magnitude would require near-total transformations of our energy, transportation, and agricultural systems. The second would involve widely deploying carbon dioxide removal mechanisms. The only currently proven mechanism for removing carbon dioxide from the atmosphere is revegetation, especially reforestation. Attempts to add carbon capture and sequestration to power plants have not yet proven viable.
The limits agreed to in the Paris Climate Agreement are not sufficient to limit the increase in GMST to 1.5°C.
In the next post, I will look at what the report has to say about strategies to meet the limit, and what the costs and benefits might be.
Intergovernmental Panel on Climate Change. 2018. Global Warming of 1.5°C (Draft). Downloaded 11/24/2018 from https://www.ipcc.ch/report/sr15.
Recent weeks have been very active for tropical storms. At one time in the Atlantic, there were 3 hurricanes (Florence, Helene, and Isaac) and 2 tropical storms (Gordon and Joyce). In the Eastern Pacific, August saw 4 tropical cyclones active at the same time (Hector, Kristy, John, and Lleana). and in September, Hurricane Hector and a new storm, Hurricane Olivia, impacted Hawaii. In the Western Pacific there have been 28 named storms. One of them, Super-Typhoon Mangkhut, caused extensive damage in the Philippenes.
Is this normal, or are tropical storms getting worse?
Tropical cyclones are rotating, organized storm systems that originate over tropical or subtropical waters. They have a center of low pressure around which they rotate that can develop into an “eye” if the storm is sufficiently intense and well organized. The thunderstorms tend to get organized into bands of thunderstorms that spiral out from the center. Even outside the thunderstorms, however, they have high sustained winds. In the Northern Hemisphere, they rotate counter-clockwise. In the Southern Hemisphere, they rotate clockwise.
Tropical cyclones are classified by the speed of their winds:
- Tropical Depressions have maximum sustained winds of 38 mph or less.
- Tropical Storms have maximum sustained winds of 39 to 73 mph.
- Hurricanes have maximum sustained winds of 74 mph or higher. In the Western Pacific, hurricanes are called typhoons. In the Indian Ocean and Southern Pacific, they are called cyclones.
- Major Hurricane have maximum sustained winds of 111 mph or higher.
Hurricanes are further classified according to the Saffir-Simpson Hurricane Wind Scale:
- Category 1: winds 74-95 mph., capable of causing damage even to well-constructed wood frame homes.
- Category 2: winds 96-110 mph., capable of causing damage to roofs and siding, blowing shallowly rooted trees over, and causing power loss.
- Category 3 (major hurricane): winds 111-129 mph., capable of causing structural damage to even well-built homes, snapping or uprooting lots of trees, and causing power outages that last for days.
- Category 4 (major hurricane): winds 130-156 mph., capable of causing catastrophic damage, ripping whole roofs off houses or blowing down walls. Regions impacted may be uninhabitable for weeks or months.
- Category 5 (major hurricane): winds 157 mph. or higher, capable of destroying most houses, blowing down most trees, cutting off access to whole regions, and making whole regions uninhabitable for weeks or months.
Tropical cyclones generally originate near the equator. Figure 1 shows the major regions where tropical cyclones tend to form, and their typical paths. I’m not sure what sends so many of them up the U.S. coast, rather than coming ashore. Perhaps it is the jet stream, or the Gulf Current, or the Mid-Atlantic High.
Figure 2 divides the year into 10-day intervals, and counts the number of tropical storms, hurricanes, and major hurricanes that form in the Atlantic Basin per 100 years during each interval. August and September are “hurricane season,” and the 10 days from September 10-19 are the peak. This chart would seem to indicate that during that interval, between 90 and 100 tropical storms originate every 100 years in the Atlantic Basin. That averages out to about 0.9-1.0 per year. Thus, it would appear that the last several weeks have been unusually active.
Figure 3 shows the number of tropical storms, hurricanes, and major hurricanes that have formed in the Atlantic Basin annually since 1851. The blue area shows the number of tropical storms, the red area shows the number of hurricanes, and the green area shows the number of major hurricanes. To each series I have fitted a polynomial regression line.
First, the variation between years is large for all of the series. Second, there are more tropical storms than hurricanes, and more hurricanes than major hurricanes. Third, all three series show an increasing trend over time. There are more tropical storms than there used to be, more hurricanes, and more major hurricanes. HOWEVER, in viewing these trends, one must keep in mind that today we have weather satellites, air travel, and a good deal more shipping density across the Atlantic Ocean. It is quite possible that some storms went undetected or unmeasured in the past, but that is no longer the case. Thus, the observed change could easily be due to better observations, not a real increase in the number of storms. I don’t have the ability to make that correction, but The Fifth Assessment Report of the Intergovernmental Panel on Climate Change concluded that evidence for an increase in the number of tropical cyclones is not robust.
As noted above, tropical cyclones can form in 8 basins around the world. One might ask which produces the most severe storms? Figure 4 shows the data. All of the basins have produced storms with sustained winds above 150, but the highest ever recorded was 215 mph. in Hurricane Patricia in the Eastern Pacific in 2015. In terms of lowest central pressure, the lowest ever recorded was in Typhoon Tip in the Western Pacific in 1979.
One might also ask which basin produces the most severe storms. Record keeping began in a different year in each basin, however, there appears to be a clear answer: the Western Pacific. Counting only storms with a minimum central pressure below 970 kPa, this basin has produced more than twice as many as any other basin.
Large cyclonic storms most often form in the tropics during hurricane season, but they don’t have to. For instance, the so-called “Perfect Storm” (they made a movie about it starring George Clooney) was a 1991 storm that formed in the Atlantic off the coast of Canada on October 29. It developed into a Category 1 hurricane, with a well defined eye, not dissipating until after November 2. Similarly, the remnants of Tropical Storm Rina (2017) travelled north across the Atlantic, crossed the British Isles, and crossed Central Europe. Entering the Mediterranean Sea, it re-strengthened into a tropical storm, now called Numa, which developed an eye and other characteristics typical of a hurricane. It’s strength peaked on November 18, with maximum sustained winds of 63 mph., not quite hurricane strength, but close.
Hartmann, D.L., A.M.G. Klein Tank, M. Rusticucci, L.V. Alexander, S. Brönnimann, Y. Charabi, F.J. Dentener, E.J. Dlugokencky, D.R. Easterling, A. Kaplan, B.J. Soden, P.W. Thorne, M. Wild and P.M. Zhai, 2013: Observations: Atmosphere and Surface. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
NASA Space Place. 2018. How Do Hurricanes Form. Downloaded 9/18/2018 from https://spaceplace.nasa.gov/hurricanes/en.
National Oceanic and Atmospheric Administration. 2018. Tropical Cyclone Climatology. Viewed online 9/18/2018 at https://www.nhc.noaa.gov/climo.
Wikipedia contributors. (2018, July 21). Cyclone Numa. In Wikipedia, The Free Encyclopedia. Retrieved 19:26, September 18, 2018, from https://en.wikipedia.org/w/index.php?title=Cyclone_Numa&oldid=851259614
Wikipedia contributors. (2018, September 14). List of the most intense tropical cyclones. In Wikipedia, The Free Encyclopedia. Retrieved 22:23, September 18, 2018, from https://en.wikipedia.org/w/index.php?title=List_of_the_most_intense_tropical_cyclones&oldid=859553932.
I’ve reported on drought in the American West many times in this blog. What about the country as a whole?
One way of looking at this question is by asking each month how much of the country has been very dry, and how much as been very wet? By very dry, I mean that the amount of precipitation for that month falls in the lowest 10% for that month in the historical record. By very wet, I mean that the amount of precipitation for that month falls in the highest 10% for that month.
The National Oceanic and Atmospheric Administration keeps this data. They measure the precipitation in every county in the country, and calculate what percent of the country was very dry, and what percent was very wet. They have data for every month going back to January of 1895.
Figure 1 shows the monthly data for every month all the way back to January, 1895. Blue bars represent the percentage of the country that is very wet. Red bars represent the percentage that is very dry. (To keep the blue and red bars from obscuring each other, I multiplied the dry percentage by -1, thereby inverting it on the chart.) I dropped trend lines on both data series. As you can see, there is considerable variation from year-to-year. There is a slight trend – hardly noticeable – towards more very wet months and fewer very dry months. But it is small, and the yearly variation is much greater than the trend.
Figure 2 shows the same data, but it beings in January, 1994.. I constructed this chart to see whether the most recent 25 years look different than the record as a whole. Again, blue bars represent very wet months, and the red bars represent very dry ones. I dropped linear trend lines on both data series, as before. The yearly variation is again larger than the trends. There appears to be virtually no trend in the number of very dry months. There is a small trend towards increasing number of very wet months. It appears a bit larger than did the one for the whole time period, but even so, it is tiny compared to the yearly variation.
It’s a bit hard to read the two data series on opposite sides of the zero line, so I constructed Figure 3. For each month it shows the percentage of the country that was very dry minus the percentage that was very wet. By doing my subtraction that way, numbers above zero mean that more of the country was very dry than very wet, and numbers below zero mean that more of the country was very wet. I dropped a linear trend on the data (red), and I also dropped a 15-year moving average on it. The chart shows that, as we saw in Figure 1, there is a slight trend towards fewer very dry months and more very wet ones. The variation is much larger than the trend, whether one looks at the monthly data, or the yearly.
This data differs from other drought data I report. Those reports focus on the Palmer Drought Severity Index, an index intended to represent soil moisture. Soil can dry out because there is little overall precipitation, or because there are longer periods between precipitation events, or because the temperature is warmer. This data would tend to indicate that regions of the country with very little precipitation may be decreasing very slightly, very slowly. Regions with very much precipitation may be increasing. This trend would be consistent with consensus predictions regarding climate change, where overall precipitation is not expected to change, but the number of heavy precipitation events is expected to increase.
National Centers for Environmental Information, National Oceanographic and Atmospheric Administration. U.S. Percentage Areas (Very Warm/Cold, Very Wet/Dry). Downloaded 9/1/2018 from https://www.ncdc.noaa.gov/temp-and-precip/uspa.
Revision: This is a revision of the post that appeared yesterday, 8/2/18. The Drought Monitor map issued 7/31/18 shows drought intensifying in Missouri, and extending to include most of the state. In this revision, I’ve replaced the map with the newer one, and I’ve revised the text to include the new information.
Drought has one again gripped the American West and Southwest. Unfortunately, the wet winter of 2017 turned out to be a one-year reprieve. Perhaps the coming winter will be wet again, but for now, the regions are once again dry – in some cases, as dry as they have ever been since record-keeping began.
Figure 1 shows the U.S. Drought Monitor for July 17, 2018. This map shows the Palmer Drought Severity Index for the United States. White areas are not in drought, colored areas are, and the darker the color, the worse the drought. It is easy to see that an “exceptional drought” has gripped portions of the Southwest, centered on the Four Corners Area where Colorado, New Mexico, Arizona, and Utah meet. Though the drought is most severe there, it has gripped much of the entire western United States.
Drought is primarily about soil moisture. Without moisture in the soil, crops wither and drinking water sources dry up. It is not feasible, however, to directly measure soil moisture across the entire country. The Palmer Drought Severity Index computes an estimate of soil moisture using temperature and precipitation data, and is the primary measure of drought used by the National Oceanographic and Atmospheric Administration.
Figure 2 shows the PDSI in June for the Southwest Climate Region (Arizona, Colorado, New Mexico, and Utah) from 1895 to 2018. Green columns represent years when it was wetter than average in June, orange columns when it was dryer than average. It is easy to see that green columns cluster to the left of the chart, and orange ones cluster to the right. In fact, of the most recent 19 years, 16 have been drier than average. This year, June was the second driest in the record, virtually as dry as it has ever been since record keeping began. The blue line shows the trend: the PDSI has decreased -0.23 per decade on average.
Ever since I wrote an extended series of posts on drought in California in 2015, this blog has followed the drought situation there. Plentiful snow during the winter of 2017 brought welcome relief, but the winter of 2018 was a big disappointment. Precipitation was below average, and the snowpack peaked well below normal (see here).
As Figure 3 shows, California has not escaped the drought gripping most of the West. The most extreme drought is in the southeastern corner of the state. That is where the Imperial Valley is located, a region that supplies us with many of our fruits and vegetables. The farms there are mostly irrigated with water from the Colorado River, so local drought there is not a terrible worry for us here in Missouri. More on the Colorado River below, however.
Figure 4 shows that the PDSI for the state as a whole for June 2018, indicates a severe drought, but not an extreme one. The trend over time is clearly downward, however, and the continued dryness represents a long-term threat to the state’s water supply.
As Figure 5 shows, California’s reservoirs are moving into deficit. They have been fuller than average for most of the time since the winter of 2017, but now three of the biggest and most important, Trinity Lake, Lake Shasta, and Lake Oroville, are below average for this date. In the chart, the yellow bars represent the maximum capacity of each reservoir, the blue bars the current level, and the red line the average for this date. Lake Oroville has not yet fully recovered from the near disaster in 2017 that caused managers to lower the lake level to prevent a collapse of the dam(see here).
Readers who have been following this blog know that California, Arizona, Nevada, Utah, New Mexico, and even Mexico depend on water from the Colorado River, and that Lake Mead is the large reservoir that holds the water for all of those states. You also know that water withdrawals from Lake Mead have exceeded inputs for many years, and the level of water in the lake has been relentlessly dropping. One study went so far as to predict that Lake Mead had a 50% chance of going dry by 2021. (Barnett and Pierce, 2008. See here for a fuller discussion California’s water resources.) Figure 6 shows the level of the lake for the past 3 years. The green line shows 2016, the red line 2017, and the blue line the year-to-date in 2018. Notice that the chart begins October 1, which is the official start of the water year. The wet winter of 2017 replenished the lake a little bit, but you can see that the current drought is causing it to drop again. Lake Mead is only 38% full, and Lake Powell, the large reservoir upstream from Lake Mead, is only 51% full. These low levels do not represent an immediate existential threat, but if dry conditions persist, they will before too many years pass.
The most important source of Missouri’s water is the Missouri River (see here). As Figure 7 shows, precipitation in the Northern Rockies and Plains Climate Region was slightly above average for the first 6 months of 2018. Statistics for the reservoirs along the Missouri show that they are at or near maximum storage. In fact, since part of their mission is flood control, several of them are higher than desired for that purpose. (U.S. Army Corps of Engineers, 2018)
Going back to Figure 1, however, you can see that the drought over the West has expanded to include Missouri, and it is especially severe in the northwestern part of the state. In St. Joseph, for instance, July brought 1.10 inches of rain, compared to 5.19 inches in an average July. In addition, since January 1, St. Joseph experienced 326 more heating degree days than average, an increase of 43%. That translates, on average, to a daily increase 1.8°F. (I arrived at this number by dividing the excess in heating degree days by the number of days.) Drought is as much a result of increased temperature as it is of reduced precipitation. Even if precipitation remains constant, increased temperature causes the ground to dry out more quickly, intensifying drought.
Because the reservoirs along the Missouri are relatively full, this drought will impact agriculture more than it will impact drinking water, unless your drinking water comes from wells. Drought can impact the availability of ground water to seep into wells, especially if they are shallow.
Climate projections for Missouri do not project a large decrease in precipitation. They tend to project that precipitation will remain about the same, or possibly increase slightly. Temperature, however, will rise, leading to a potential increase in the frequency of damaging drought. The real concern, however, is that the drought in the American West might not be not a temporary weather phenomenon, but, instead, a permanent change in climate. Modelers predict that climate change will cause just such a change Could it be occurring already?
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.
Lake Mead Water Database. 2018. Lake Mead Daily Water Levels, Last 3 Water Years. Downloaded 7/19/2018 from http://graphs.water-data.com/lakemead.
National Oceanographic and Atmospheric Administration. 2018. Climate-at-a-Glance. Data downloaded 2018-07-19 from https://www.ncdc.noaa.gov/cag.
Riganti, Curtis. 2018. U.S. Drought Monitor, July 17, 2018. National Drought Mitigation Center. Downloaded 7/19/2018 from http://droughtmonitor.unl.edu.
U.S. Army Corps of Engineers, Missouri River Basin Water management. 2018. Mainstem and Tributary Reservoir Bulletin, 7/18/2018. Viewed online 7/19/2018 at http://www.nwd-mr.usace.army.mil/rcc/reports/pdfs/MRBWM_Reservoir.pdf.