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U.S. National Climate Assessment, Volume 1

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.

Temperature record

Figure 1. Source: USGCRP, 2017.

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.)

Projected Temperature

Figure 2. Source: USGCRP, 2017.

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)

Sea Level Rise

Figure 3. Source: USGCRP, 2017.

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).




Minor Tidal Floods

Figure 4. Source: USGCRP, 2017.

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 Precip Graphic

Figure 5. Source: USGCRP, 2017.

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.

Krugman: “The Depravity of Climate-Change Denial”

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.

Global Warming of 1.5°C (2)

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.

CO2 Emission Price

Figure 1. Source: Intergovernmental Panel on Climate Change, 2018.

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.

Threats to systems

Figure 2. Source: Intergovernmental Panel on Climate Change, 2018.

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.

Global Warming of 1.5°C (1)

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.

GMST 1850-Present

Figure 5. Global Mean Surface Temperature 1850-Present. Source: IPCC 2018.

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.

Reduction Pathways

Figure 6. GHG Emission Reduction Pathways. Source: IPCC 2018.

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.

Second Lowest Arctic Sea Ice on Record

Figure 1. Source: National Snow & Ice Data Center.

Arctic sea ice apparently reached its annual maximum extent on March 17, 2018, and it was the second lowest in the record, according to a report from the National Snow and Ice Data Center.

Each summer the arctic warms, and as it does, the sea ice covering the Arctic Ocean melts, reaching an annual low-point in late summer. Then, each winter the arctic cools, the surface of the ocean freezes, and the area covered by sea ice expands. The sea ice reaches its maximum extent in late winter, this year on March 17.

The National Snow and Ice Data Center tracks the extent of the sea ice using satellite images, as shown in Figure 1. The map is a polar view, with the North Pole in the center, the sea ice in white, and the ocean in blue. The land forms are in gray, with North America at lower left, and Eurasia running from Spain at lower right to the Russian Far East at the top. The magenta line shows the 1981-2010 average extent of the ice for the month of March. It doesn’t look like much on the map, but the anomaly in 2018 amounts to 436,300 square miles less than average.

(Click on figure for larger view.)

Figure 2. Source: National Snow & Ice Data Center.

Figure 2 shows the trend in Arctic sea ice from 1979-2018. The declining trend is easy to see. (The y-axis does not extend to zero to better show the change.) The National Snow and Ice Data Center applied a linear regression trend line to the data (blue line), and the trend shows an average loss of 16,400 square miles per year.






What about the annual minimum? That has been shrinking, too. Figure 3 shows the Arctic sea ice minimum in 1980, and Figure 4 shows it in 2012. The prevailing winds tend to blow the ice up against Greenland and the far northern islands of Canada, but you can see that in 1980 most of the sea, from the Canadian islands, to Greenland, to the Svalbard Islands, to Severnaya Zemla (anybody remember the Bond movie “GoldenEye?”), to the north of Far Eastern Russia, was covered by ice. In 2012, however, more than half of the Arctic Sea was ice-free, from north of the Svalbard Islands right around to the Canadian Islands. Even the famed Northwest Passage, a channel through the Canadian Islands, was open.

Figure 3. Minimum Extent of Arctic Sea Ice, 1980. Source: NASA Scientific Visualization Studio.

Figure 4. Minimum Extent of Arctic Sea Ice, 2012. Source: NASA Scientific Visualization Studio.









Figure 5. Minimum Extent of Arctic Sea Ice, 1979-2017. Source: NASA Global Climate Change.

Figure 5 charts the trend in the annual minimum. At its low in 2012, it was less than half of what it was in 1980.

The volume of the polar ice cap also depends on how thick the ice is. Satellites can photograph the entire ice cap, but data on thickness come to us from on-site measurements at a limited number of points. I don’t have a chart to share with you, but the data seem to indicate that compared to the years 1958-1976, in 2003-2007 the thickness had declined about 50% to 64%, depending on where the measurement was taken. (This change is approximate, being read off of a graph by Kwok and Rothrock, 2009.)

Thus, the decline in the arctic ice cap is actually much larger than suggested by the change in its extent.

Why does arctic sea ice matter? First, Arctic sea ice does not form primarily from snowfall, as does the snowcap in the western United States. Arctic sea ice forms because the temperature is low enough to cause the surface of the water to freeze, just as the your local pond or lake freezes if it gets cold enough. Thus, declining Arctic sea ice is a sign that the Arctic is warming. The Arctic seems to be the part of the planet that is warming the most from climate change, and this is a clear and graphic sign of that change.

Oddly, the warming arctic is one reason for the bizarre weather we have had in Missouri this winter. As noted in a post on 1/22/2015, the warming arctic weakens the polar vortex, which allows arctic cold to escape and travel south, impacting us in Missouri. Figure 6 shows the anomaly in Arctic temperatures from December, 2017 through February, 2018, in C. While it was warm over the entire Arctic, as much as 7°C above average (12.6°F), it was 2-3°C cooler than average over North America (3.6-5.4°F).

Second, it matters because ice is white, but the ocean is blue. That means that sunlight hitting ice reflects back towards space, and is not absorbed. Being blue, however, the ocean absorbs the light, and converts the energy to heat. This reflective capacity is called “albedo,” and the albedo of ocean is less than that of ice. Thus, the ice is melting because of global warming, but then, the melting contributes to even more global warming through the change in albedo. People are fond of saying that the earth has buffering mechanisms that tend to inhibit large climate changes, and such mechanisms do exist, but not everywhere in all things. This is one example where the earth shows positive feedback that destabilizes the climate even further.

Melting Arctic ice is not a major factor in the rising sea level. The reason is that the ice is already in the water. When the ice in your glass of iced tea melts, it doesn’t make the glass overflow. In the same way, as this ice melts, it has only a small effect on sea level. On the other hand, the Greenland Ice Cap and the Antarctic Ice Cap are not already in the water, and as they melt, they do affect sea level.

One final word: the data above are not computer models of future events. They are the best data available of what has already been happening, and what is happening now. To deny the reality of climate change is like denying that a river will flood, even as its water already swirls around your knees.


Kwok, R., and D./A. Rothrock. 2009. “Decline in Arctic Sea Ice Thickness from Submarine and ICESat Records: 1958-2008. Beophysical Research Letters 36:L15501. Cited in National Snow & Ice Data Center. State of the Cryosphere. Viewed online 4/12/2018 at http://nsidc.org/cryosphere/sotc/sea_ice.html.

NASA Global Climate Change. Arctic Sea Ice Minimum. Downloaded 4/12/18 from https://climate.nasa.gov/vital-signs/arctic-sea-ice.

NASA Scientific Visualization Studio. Annual Arsctic Sea Ice Minimum 1979-2015 with Area Graph. Downloaded 4/12/18 from https://svs.gsfc.nasa.gov/4435.

NASA Scientific Visualization Studio. Annual Arsctic Sea Ice Minimum 1979-2015 with Area Graph. Downloaded 4/12/18 from https://svs.gsfc.nasa.gov/4435.

National Snow & Ice Data Center. “2018 Winter Arctic Sea Ice: Bering Down. Arctic Sea Ice News & Analysis. 4/4/2018. Downloaded 4/12/2018 from http://nsidc.org/arcticseaicenews.

California Drought Emergency Officially Over

Gov. Jerry Brown officially declared California’s drought emergency over on Friday, April 7. It was a fitting ending to one of the worst episodes in California’s drought-laden history.

Or was it? The next two posts update California’s water situation. This one focuses on the current short-term situation. The next one focuses on the future, with an eye toward the future impact of climate change. I have personal reasons for following California’s water situation – I have family living there. But in addition, California is the most populous state in the Union, it has the largest economy of any state, and the state grows a ridiculously large fraction of our food. What happens in California affects us here in Missouri.

Figure 1. California Snowpack, 3/31/2017. Source: California Department of Water Resources.

Is the short-term drought truly over? Yes, I think so. The vast majority of California’s precipitation falls during the winter, and the snowpack that builds up in the Sierra Nevada Mountains serves as California’s largest “reservoir.” As it melts, it not only releases water that represents about 30% of the state’s water supply, but it also feeds water into the underground aquifers that provide groundwater to much of the state. Thus, the size of the snowpack is the most important factor in determining California’s water status. California measures the water content of the snowpack electronically and manually. The measurements around April 1 are considered the most important, as that is when the snowpack is typically at its largest. Figure 1 shows the report for this year. Statewide, the water content of the snowpack was 164% of average for the date, almost 2/3 larger than average. The water content was significantly above average in all three regions of the snowpack, North, Central, and South.



I follow the snow report at Mammoth Mountain Ski Resort to provide a specific example of the snow conditions. Figure 2 shows that through March, Mammoth received over 500 inches of snow, one of the highest totals in the record going back to 1969-70. The column for 2016-17 has very large blue and orange sections, indicating that the majority of the snow fell in January and February. Figure 3 confirms the impression. It charts the amount of snowfall at Mammoth during each month of the 2016-17 snow season, and compares it to the average for that month across all years. You can see that both January and February were monster snow months, especially January. By March, snowfall had already fallen below average. I wouldn’t make too much of this fact, one month doesn’t make a trend.

Figure 2. Source: Mammoth Mountain Ski Resort.

Figure 3. Data source: Mammoth Mountain Ski Resort.











Figure 4. Source: California Data Exchange Center.

California also stores water in man-made reservoirs. Figure 4 show the condition of 12 especially important ones on March 31. Most were above their historical average for that date, and many were approaching their maximum capacity. Those who follow this blog know that the Oroville Reservoir actually received so much water that it damaged both the main and emergency spillways, threatening collapse of the dam and requiring evacuation of thousands of people down stream. (See here.)







Figure 5. Elevation of the Surface of Lake Mead. Source: water-data.com.

In addition, Southern California receives the lion’s share of water drawn from the Colorado River, thus the status of Lake Mead, the largest reservoir on the Colorado, is important to the state. A study in 2008 found that there was a 50% chance the reservoir would go dry by 2021. On March 31, Lake Mead was at 1088.26 feet above sea level. (This doesn’t mean there were that many feet of water in the reservoir, Hoover Dam isn’t that tall. Rather, it represents how many feet above sea level the surface of the water was. Lake Mead’s maximum depth is 532 feet.) The current level represents 41.38% of capacity. Figure 5 shows the level of the lake over time. You can see that the line tends to go up with the spring snowmelt, and down during the rest of the year. This year it is up very slightly year-over-year, but the trend has been relentlessly down since 2000.

The conclusion seems inescapable: for this year at least, California has plenty of water. The short-term drought is over. One year doesn’t make a climate trend, however. In the next post I will consider the implications of this wet winter for California’s water situation going into the future.


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.

CA.GOV. Governor Brown Lifts Drought Emergency, Retains Prohibition on Wasteful Practices. Viewed online 4/10/2017 at https://www.gov.ca.gov/home.php.

California Data Exchange Center. Conditions for Major Reservoirs: 31-Mar-2017. Viewed online at http://cdec.water.ca.gov/cdecapp/resapp/getResGraphsMain.action.

California Department of Water Resources. Snow Water Equivalents (inches) for 3/30/2017. Viewed online 3/31/2017 at http://cdec.water.ca.gov/cgi-progs/snowsurvey_sno/DLYSWEQ.

Mammoth Mountain Ski Resort. Snow Conditions and Weather, Extended Snow History. Data downloaded 4/2/2017 from http://www.mammothmountain.com/winter/mountain-information/mountain-information/snow-conditions-and-weather.

water-data.com. “Lake Mead Daily Lake Levels.” Downloaded 4/5/2017 from http://graphs.water-data.com/lakemead/.

In Missouri, Your Electric Car May Be a Turkey

Compared to gasoline powered cars, electric cars may be worse for the environment and for climate change, according to a new analysis published in the Proceedings of the National Academy of Sciences. It depends on where your electricity comes from.

The authors performed a lifetime analysis in which they estimated not only the pollution and emissions that come from the tailpipe of your car, but also the pollution and emissions resulting from manufacturing the fuel. So, for instance, oil has to be extracted from the ground, refined, and transported to your local gas station. All of that causes both pollution and GHG emissions. Similarly, an electric car requires a battery. The chemicals used in the battery have to be mined, and the battery has to be manufactured. Then the battery must be charged with electricity, which has to be generated. All of this mining, manufacturing, and generating causes both pollution and GHG emissions. The study estimates the total amount of pollution from all of these processes.

The authors studied gasoline and 10 alternative fuels that are commonly discussed as future gasoline alternatives:

  • Gasoline hybrid
  • Diesel
  • Concentrated natural gas
  • Corn grain ethanol
  • Corn stover ethanol
  • EV charged by grid average electricity (“EV” = electric vehicle)
  • EV charged by electricity from coal
  • EV charged by electricity from natural gas
  • EV charged by electricity from corn stover
  • EV charged by electricity from wind, water, or solar

The authors weren’t interested in comparing results across states, so they did not look at differences in electrical generation between states. They focused on differences between the fuel types.

They found that in the future all fuel types resulted in increased emissions and pollution. This is because the number of miles driven is expected to increase in the future. I want to emphasize this point, because otherwise some of the charts below may give the wrong impression. Environmental damage from automobiles is projected to increase because more miles are expected to be driven.

From Tessum, Hill, & Marshall, 2014.

From Tessum, Hill, & Marshall, 2014.

However, compared to gasoline, some alternative fuels are projected to produce less harm, and some more harm. The chart at right shows the damage from the 10 alternative fuels relative to gasoline. Bars on the negative side of the chart do not mean damage will be reduced, they only mean that damage will increase less than in the case of gasoline. The black portion of the bar represents damage from pollution, the white portion of the bar represents damage from climate change.

(Click on chart for larger view.)

Compared to a regular gasoline powered car, an electric vehicle charged with electricity from wind, water, or solar is the best, causing about $0.40 less in pollution damage per gallon of gasoline equivalent, and about $0.50 less in climate change damage. Corn stover ethanol is second best, though its advantage is almost entirely from reduced climate change damages. Third best is an electric vehicle charged with electricity generated by burning natural gas.

The worst scenario involved an electric vehicle charged with electricity from coal. It had almost $1.50 more pollution damage per gallon of gasoline equivalent than a standard car, plus another $0.10 or so from climate change damages. Second worst was an electric vehicle powered by grid average electricity. Third worst was a car powered by corn grain ethanol. Most of Missouri’s electricity is generated by burning coal, so that makes Missouri a state in which an electric vehicle would be particularly damaging.

From Tessu, Hill & Marshall, 2014.

From Tessu, Hill & Marshall, 2014.

The series of maps at right shows the projected concentrations for PM2.5, particulate matter smaller than 2.5 microns in diameter. I discuss it briefly in Update on Missouri Air Quality. Many experts feel it to be the form of air pollution that causes the most damage to human health.

In the series of maps, the blue and red map at upper left shows the baseline concentration of PM2.5; it should be read against the colored bar on the lower left. The remaining 12 maps show the changes in PM2.5 levels expected in the future, and should be read against the colored bar on the lower right.

Notice that every fuel causes an increase in the PM2.5 level. However, there are some stark differences. The increase from electric vehicles charged by electricity from coal really turns the map red, as if the country were bleeding. Electric vehicles charged by electricity from the grid average, and vehicles powered by corn grain ethanol are nearly as bad.

Notice that Missouri is in the region of maximum damage from EV Coal and from corn grain ethanol.

The fuel that causes the smallest increase in PM2.5 is an electric vehicle charged by electricity generated from wind, water, or solar. That map is almost white, only very slightly pink in some areas. The map for natural gas appears to be the next whitest, and the one for gasoline hybrid appears to be the third whitest. You can do a lot worse than simply driving your good old hybrid.


Tessum, Christopher W., Jason D. Hill, & Julian D. Marshall. 2014. “Life Cycle Air Quality Impacts of Conventional and Alternative Light-Duty Transportation in the United States.” Proceedings of the National Academy of Sciences, Vol 111 (32), 18490-18495. http://www.pnas.org/content/early/2014/12/10/1406853111.abstract?

Americans Believe the Environment Should Be Protected

A poll conducted by the New York Times and CBS News shows that most Americans (58%) believe that the environment should be protected, even at the risk of curbing economic growth. Only 37% believe that economic growth should be given priority if the environment suffers as a result.

For decades there has been a belief that good environmental stewardship must inevitably reduce economic growth. Many contemporary environmentalists challenge that belief, however. Environmental stewardship might reduce economic growth if it is poorly designed, they have said, but it doesn’t have to if it is well designed. In fact, they have argued, environmental degradation itself limits economic growth, and good environmental stewardship might enhance economic growth compared to that.

In either case, the poll suggests that the majority of Americans do not agree with the reckless pursuit of economic growth at the expense of the environment.

Serious ImpactThe poll had some other interesting findings. Global warming, which I tend to call climate change, has been a significant concern of this blog. As the first chart at right shows, the poll shows that 28% of Americans believe that it will have a serious impact in the future, and 46% believe that it is already having a serious impact. Combined, that’s about 3 out of every 4 people. One often hears that there is a scientific consensus about the seriousness of climate change, but that the average American is not so sure. This poll suggests that there may be more of a consensus among Americans than is often portrayed.

(Click on chart for larger view.)

This question has been asked in several polls going back to 2011. Because of the variability from poll to poll, and because polls always contain a confidence interval that is several percentage points wide, it is difficult to read many trends simply by looking at the chart. The one trend I can pick out for certain is that for several years there were some people who denied the existence of global warming entirely. That no longer appears to be a tenable opinion, and has vanished from the chart completely.

Causes chartThe poll also asked people whether they thought global warming was caused mostly by human activities or mostly by natural patterns in the earth’s atmosphere. The data only go back 3 years instead of 13, but the trend over time is clearer, as shown in the second chart at right. The percentage of people who believe it is caused by human activities has increased from 41% in 2011 to 54% in September of 2014.

Oddly, in these polls, 10% of those asked said global warming doesn’t exist, where just a moment ago, nobody was saying that. It just goes to show you how unreliable polls are, and how the way you ask the question seriously impacts the answers you get.


The poll data were published by the New York Times: Connelly, Marjorie. “Global Warming Concerns Grow.” New York Times. 9/22/14. http://www.nytimes.com/2014/09/23/science/global-warming-concerns-grow.html?module=Search&mabReward=relbias%3Ar%2C{%221%22%3A%22RI%3A11%22}&_r=0.

The poll results themselves were linked to from the article: “The New York Times/CBS News Poll, Sept. 10-14, 2014.” http://graphics8.nytimes.com/packages/pdf/science/NYTpoll-sept-14-globalwarming.pdf?action=click&contentCollection=Science&module=RelatedCoverage&region=Marginalia&pgtype=article