December 30, 2018

Year in Review I: The Big Picture

With new year's coming up tomorrow night, it is appropriate to look back on the weather of the past year.

The essential take away:  2018, and particularly the late spring and summer, were much warmer than normal.
We can illustrate this with a nice graph (see below) produced by the National Weather Service for Seattle-Tacoma Airport, showing the observed temperatures (blue line), the normal range (green shading) and the records for each date (high records-red color, low records, blue color).

One is struck immediate by the many dates that were above normal, particularly from May 1 to Sept. 1).    A number of these days hit highs 10-15F above normal.    On the other hand, the annual extremes were not impressive...on day got to 94F and the lowest temperature all year was 24F, with only one cold spell in late February.

Precipitation was a very different story--the annual precipitation will end up slightly below normal (see middle graph, top of light green shows accumulated precipitation), resulting from a wetter than normal first half of the year, a dry summer, and moist late fall.

Snow in Seattle was almost absent:  about 1 inches compared to a normal total of around 6 inches.

A regional view of the differences from normal of temperature and precipitation for 2018 is shown below.   For temperature, the entire region west of the Rocky Mountains has been warmer than normal, particularly the U.S. Southwest.   Here in WA state, roughly 1-2F above normal.   But note the cooler than normal weather over the northern Plains.  That will be important.

Precipitation is more complex.  Most of the west was near normal in 2018, except from southwest WA to northern CA, where is has been quite dry.  The contrast across western WA is really substantial.

So what it the cause of the warm anomaly in the West?

Anthropogenic global warming might be making some contribution, but there is much more going on.    A hint at this comes from taking a broader perspective, looking at all of North America (see below).   This figure shows the temperature anomaly (difference from normal) for 2019.  Blue indicates colder than normal and  red/orange above normal.   The western U.S. is warm, but the middle of the country is cold, while the East Coast is warm.

This pattern was associated with an amplified upper-level wave pattern, with ridging (high pressure) over the West Coast, with troughing (lower pressure) over the central U.S..   This pattern was evident for much of the year, including our warm/dry period in November and during the late spring.

To illustrate, here is a map produced by the National Weather Service showing the average upper level (500 hpa) height anomaly in November (sorry it is blurry, the government shut-down makes it impossible for me to get better graphics).  Red indicates higher than normal heights (ridging), blue indicates troughing).  Ridging produces localized warm surface temperatures, the opposite for troughing.  Ridging also suppresses precipitation, explaining our drier than normal conditions.

There is no reason to expect that this pattern has anything to do with global warming (note:  the "lazy jet stream" hypothesis has been firmly disproved in the peer review literature). 

How much of our warm year might be due to anthropogenic global warming?   We can get some insights into this by using the wonderful Washington State Climatologist climate plotting site (with kudos to Karen Bumbaco and Nick Bond).    The annual temperature in Seattle is shown below.  A small upward trend of perhaps .5F, with human caused global warming undoubtedly contributing during the past 30 years.  Other local stations are similar.

The take away is that most of the warming this year (1-2F)  is due to the anomalous upper level pattern, which is probably the result of natural variability.  Why am I stressing this point?  Because too many people, and unfortunately some in the media, make the assumption that every warm anomaly is mainly the result of increasing CO2 in the atmosphere.   This is simply not true.


  1. " the "lazy jet stream" hypothesis has been firmly disproved in the peer review literature). "

    Awesome! We eagerly look forward to a guest appearance here from Jenifer Francis buying you a well deserved pint

  2. When was the last cooler than normal summer? It feels like it's been multiple summers of hotter and drier conditions, with the last 2 being brutal with the addition of smoke.

  3. Most memorable weather event of 2018? The God-awful smoke storms in August. Those were enough to make one consider packing up and moving elsewhere.

  4. Volume 1 of the 4th National Climate Assessment estimates that for the Northwest as a whole average temperature (overall, maximum, and minimum) have all increased by approximately 1.5F in the present day period (1986 to 2016) compared to the first half of the 20th century. In addition, the coldest day of the year for the Northwest has increased by nearly 5F in the same period, the largest for any US contiguous region. And, of course, projected increases through the end of this century are very substantial, depending on which model is used.

    The Pacific Ocean off the Northwest coast is warming substantially as well.

    So, I was having a bit of difficulty interpreting your comment that in Seattle there has been "[a] small upward trend of perhaps .5F, with human caused global warming undoubtedly contributing during the past 30 years." I would be surprised if Seattle and the Puget Sound are not warming as much as the Northwest as a whole, but perhaps this is the case:


    My understanding is that attribution of human causation to warming of specific regions is less certain compared to the very high level of confidence that overall global warming is due to human activity. Nevertheless, there is already strong support for warming in the Northwest as being part of a human caused global warming effect:

  5. MAC, there is no mystery here. Cliff is showing data for Seattle. It's a single station. It is useful to bear in mind that there is considerable uncertainty in temperature measurements and even more in regional or global temperature anomalies calculated from the data.

    On a global temperature level, UAH TLT shows the lowest warming rate of about 0.14 per decade. Hadcrut4 shows about 0.17, GISS shows about 0.19, and the RSS satellite (recently updated) shows 0.22.
    That's a large spread.

    Another thing to bear in mind is that over the 40 years of satellite data, RSS TLT shows less warming globally than the CMIP5 climate models. RSS TLT in the tropics shows perhaps half the warming as the CMIP5 model mean.

    Bottom line, There is huge uncertainty as to exactly how much it has warmed over the historical record. There is much larger uncertainty in how much it will warm in the future with global climate models having well known deficiencies making them not skillful in this regard.

  6. I went to the OWSC website. I echo the kudos from Dr. Mass. Here is the link for anyone who wants to play around with trends in Washington climate:

    But I wanted to make two comments on the trend graph that Dr. Mass chose to print for Seattle:

    1. It looks to me that Seattle and a few other cities, mostly in southern Puget Sound, are pretty much outliers among all of the reporting sites in the states of Washington, Oregon, and Idaho. My city of Bellingham shows ~1.8F increase over this period. So, while people in Seattle might be led to think average temperature increases in Seattle are relatively small, it does not appear to be the case for the rest of the Northwest. When I eyeball the map, it looks like at least 75% of the reporting sites show substantially larger increases.

    2. If you look at average minimum temperature for Seattle during this period, the increase is almost three times as large (~1.5F). With that measure, Seattle looks much more like the rest of the Northwest. If you do the trend line for average maximum temperature in Seattle, it is decreasing (not increasing) by about .5F. So, it does appear to me that Seattle's temperature is showing a significant increase at the lower end of the temperature spectrum, which is not apparent from the overall average. I think it is an interesting question why Seattle should have lower average maximum temperatures. On the map, there is a band of reporting sites all in approximately the same latitude that show the same effect (Seattle, Wenatchee, Spokane, Kellogg). I would be interested in any hypothesis that Dr. Mass might advance to explain that observation.

  7. SeaTac's failing sensor didn't help.

  8. Ruth - That woke us up here in Mukilteo! Heavy rain and hail. I think I heard thunder distantly once, but it was the noise of rain and hail hitting the roof that woke me up. I think it was a tenacious convergence zone, but not sure of that.

  9. Can you please expand on how the lazy jet stream has been debunked? In the last couple of years you haven't discussed past more than a couple of sentences. Im honestly just curious. Is a bit tricky navigating google as a layman sometimes.

  10. "Last week, in the journal Nature Communications, Francis and two of her colleagues published a paper offering further observational evidence for the hypothesis. Led by Judah Cohen, a visiting scientist at M.I.T. and the director of seasonal forecasting for the climate-risk company Atmospheric and Environmental Research, they looked back at meteorological records from twelve American cities, spanning from 1950 to 2016, and found that, when temperatures were anomalously high in the Arctic, extreme winter weather on the East Coast was between two and four times likelier to occur. The paper, Cohen said, does not attempt to explain why this might be. ... Her hypothesis [Francis] has more to do with how long a cold spell ultimately lasts than whether it breaks any temperature records. 'Persistence is the whole key,'...”

    Doesn't seem like the lazy jet stream hypothesis has been firmly disproved. From this March 2018 New Yorker article it seems there is some evidence that it may still be true.

  11. Another comment by same unknown. Perhaps you could delve into how climate change will affect the jet stream based on current models, peer literature, etc.

    I think it would be fun to read/learn about.

  12. Yes - cannot say the link between polar vortex/jet stream blocking patterns and global warming has been disproved - emerging evidence there may be a link e.g. due to warming Arctic:

    'New theory finds 'traffic jams' in jet stream cause abnormal weather patterns'

    'Polar Vortex: How the Jet Stream and Climate Change Bring on Cold Snaps'

  13. The 2018 NOAA Arctic Report Card, which was released this month, does not dismiss the lazy jet stream hypothesis at all:

    See generally, pp. 74-80, Clarity and Clouds: Progress in Understanding Arctic Influences on Mid-latitude Weather

    My interpretation of the discussion is there are potentially multiple mechanisms at play that may accompany arctic warming and loss of sea ice, which are not yet fully understood (see pp. 75-76):

    "In addition to [amplified warming of the Arctic region], we know that many changes in the climate system are happening simultaneously and are also affecting mid-latitude weather regimes. For example, most climate model simulations for the future indicate that another area of amplified warming will occur in the upper atmosphere over the tropics (though there's no sign of it yet in observations). This amplification will increase the north-south temperature difference between the tropics and mid-latitudes and oppose the influence of AAW. * * * [M]any details of linkage mechanisms remain elusive."

    See also the discussion on pp. 76-77 under "Cold Eurasian winters linked to sea-ice loss in the Barents and Kara seas."

  14. Cliff- While I appreciate the many posts you make reiterating that weather != climate, I think it would be useful for you to post more often about why global warming is a concern we should be doing something about and maybe how. It is important to be scientifically accurate in your posts, but what you choose to post about reflects your priorities for what the public should know about.

    The main republican message is that climate change activists are self interested alarmists who conflate weather with climate and look to raise revenue for pet projects through a carbon tax. We shouldn't trust them or government, and therefor we should do nothing about climate change.

    I wonder if in environmental movements to restrict smoking or remove lead from consumer products or abolish DTD you would have preoccupied yourself with pointing out the many scientific inaccuracies in those movements. Would you have been preaching "we don't know why that particular celebrity got lung cancer" or "we don't know that mental retardation in that group of children was caused by lead" or "cigarette taxes aren't revenue neutral so we should vote no".

    I say all this as someone who largely agrees with your point of view in substance. The last carbon tax was far worse than a revenue neutral model, but the alternative was doing nothing, and doing nothing was the worst solution of all. Similarly, I agree that global warming activists conflate weather with warming, but the fact is that weather generates news, and of course people concerned about global warming want to use the news event as a catalyst for action on global warming.

    With climate change, are you really intent on having your roll to be a climate activist fact checker who tilts the climate change argument towards "do nothing"? Why not focus on what effects we do see from global warming, and on what actions we should be taking to help address the problem and prepare for its impacts?

  15. Some research on changes in jet stream and implications, likely causes (sumaries with links to origial papers). Don't know whether this relates to the the cutesy 'lazy' jet stream Mass refers to, but certainly provides new insight into what influences jet stream behavior - and, of course, weather

  16. If I recall you cited a paper from CO State rebutting the original Francis paper. Since then there have been multiple papers supporting the Francis hypothesis but I haven't seen any peer reviewed rebuttals. Do you have more rebuttals to list?

  17. M P said

    “SeaTac's failing sensor didn't help.”

    It would be nice if there was a convenient way to explain what looks like anomalous data, but I would surprised if this was the explanation. I took another look at the OWSC website and made sure that I was selecting the same years (1929-2017) that Dr. Mass had on his post. I continue to believe that his statement of “[a] small upward trend of perhaps .5F” greatly understates the extent of warming in this time period in Seattle and certainly the rest of the Northwest. Based on this statement, it would be easy for a reader to conclude that the Northwest is not experienced very much warming. While the statement may be literally correct for Seattle if you use only average temperature, it leaves out a lot important context.

    First, here is a link to the Seattle average temperature screen used by Dr. Mass, which was the basis of his statement:

    Second, here is a link for average minimum temperatures:

    Third, here is a link for average maximum temperatures:

    Finally, for general reference, this is a link to the Northwest average temperature, with no particular site selected. It has the same Northwest map as the first link, but the colors are easier to discern. The large red circles indicate sites with significant warming. Small circles mean the change is not significant. But as you can see, a very high percentage of Northwest and Washington sites show significant average temperature warming (like my home city of Bellingham with +1.91F). No site shows cooling.

    As stated before, it appears clear that the reported .4F decrease in average maximum temperature for Seattle is what has made the difference. It brought the overall average down as the average minimum temperature for Seattle actually increased by 1.58F.

    As stated before, there is a band near I-90 of reporting sites at Seattle’s latitude that all appear to report smaller average and average minimum increases and, like Seattle, some show actual decreases in average maximum temperature. So, while there may be selected locales within the Northwest that are not warming as much due to local or other microclimate effects, the overall message is one of much more warming than .5F.

  18.  the fact is that weather generates news, and of course people concerned about global warming want to use the news event as a catalyst for action on global warming.
    That's fine if the news event is covering a phenomenon that is clearly caused by global warming such as rising sea level or melting polar ice caps. However if the news event is a hurricane or a major windstorm or a wildfire (which are totally normal, naturally occuring weather events that have been happening on this planet since the beginning of weather as we know it and will continue to occur long after humans are gone)than that's just a plain lie. The media reports that seem to claim that just about every flood, fire, hurricane, tornado and major weather event is caused or made worse by climate change is absurd. It's disinformation to follow a narrative (like we dont see enough of that in the media these days) to try and change how people think. People show a lack of trust in the media these days because it's clear rather than just "reporting the news" many media outlets and journalists have now become activists and clearly have a narrative to follow.

  19. The one-half degree increase from 1930 to present could easily be attributed to the urban heat island effect.

  20. @Eric Fisk, with respect to your carbon taxes, the dogs don't like the dog food. Being a Seattle "progressive," you will do your damndest to force the dogs to eat it, but as long as the dogs get to vote they are going to reject your dog food.

  21. Eric Fisk, Smoking and DDT are not good analogies. Fossil fuels have a huge economic benefit not to mention improving individuals quality of life. That's why mitigation has largely been a failure. I personally believe that the dangers of warming are already trumpeted almost daily by a compliant press repeating exaggerated messages from activists. These messages are creating cynicism amoung a public that has been bombarded for over 50 years with advice that is "backed by science" such as that dietary fat was very harmful. The problem here is much more about crisis fatigue caused by dramatic falsehoods and exaggerations. Cliff's desire to counter these lies may actually lead to a truer message that might be better accepted by the public.

  22. Like so much in climate science, the lazy jet stream theory looks like its a subject of controversy. Why would anyone be surprised. Everything in climate science is based on uncertain data, even more uncertain climate models, and often poor statistical analysis. For example, the pause. There are perhaps 200 climate science papers admitting the pause and trying to explain it. Now there is a new paper by Mann, Oreskes, Lewindowski, and Ramsdorff saying it didn't exist and all those previous papers were caused by confirmation bias. Of course, this group of authors has a less than stellar scientific track record. Anyone who says the science of climate is settled is sadly misinformed or worse an activist with a bias.

  23. the rebuttal on the Francis hypothesis has focused on the measurement of waviness of the Rossby waves. At the time it made valid arguments on the methodology. Since then there have been several studies employing more mathematical rigor. One of the best (I have done a lot of engineering signal analysis) shows a definite increase in waviness:
    Changes in meandering of the Northern Hemisphere circulation

    Giorgia Di Capua1,2 and Dim Coumou 1
    1 Potsdam Institute for Climate Impact Research, Earth System Analysis, D-14473 Potsdam, Germany

    2 University of Potsdam, D-14469 Potsdam, Germany

  24. In regard to the regular commentor "Placeholder":

    It should be obvious to all by now that "Placeholder" holds and expresses freely an animosity and general contempt for anyone who he perceives as a typical denizen of Seattle. In fact, this sentiment is often the entirety or no less than half of his prodigious communications, as is evident in his response to the above Eric Fisk.

    Speaking for myself, I don't particularly mind this, as any libertarian minded person surely wouldn't, considering our inalienable right to free speech.

    The one thing I do take offence at is that "Placeholder" is a name that somehow I doubt is written onto any birth certificate, Kenyan or otherwise, and as one can see written directly below in the rules and regulations and I quote:

    "This blog does not allow anonymous comments."

    It seems to me only courteous (and apparently required) that if "Placeholder" is inclined to respond as he does to a person who not only shows respect to our intelligence through a well reasoned and respectful articulation of his thoughts but then signs with his name and an identifiable photo that "Placeholder" should at the very least sign his name with something a little bolder than a rather strange pseudonym.

    And if really honourable, an indication of which town he lives in...... and presumes to represent, it would seem.

    Signed: Bruce Kay of Powell River, BC

  25. Don Healy said...

    "The one-half degree increase from 1930 to present could easily be attributed to the urban heat island effect."

    The problem with the "heat island" hypothesis is it would not explain why the average temperature for all of Washington increased by +1.6F in this period (OR is +1.9F, ID is +1.8F, and MT is +2.0F). Increases for Washington average minimum temperature appear to be the largest in the Winter (+2.9F) and Summer (+1.9F), with Spring (+.8F) and Fall (+.9) showing less. If Seattle was a heat island, you would expect Seattle's increases to be more, not less, than the rest of the state and region.

  26. In my last comment, I should have said "Increases for Washington average temperature * * *," not "Increases for Washington average minimum temperature". Sorry for any confusion.

  27. @Bruce, do you have any spare sanctimony, or do you really need all of that for yourself?

  28. The Seattle Urban USHCN temperature record shown in the plot comes from the University of Washington from 1909 - 1971, then they use the Portage Bay (Montlake) record from 1972 - 1998. After the Portage Bay site closed in 1998 the data is fake data, or not actually observed data.

    1) 1909 - 1971 Univ of Washington
    2) 1972 - 1998 Portage Bay
    3) 1999 - 2018 Fake data - not observed

    1. Mark

      How did the fake data compare to the observed from stations around Seattle?

  29. I ended up with 43 inches of rain on the Bothell- Mill creek line. But almost no rain in May, July, or Smogust ;-)

  30. 'the "lazy jet stream" hypothesis has been firmly disproved in the peer review literature'

    The fairest statement on this topic is that it is still an area of active research.

    There are recent peer reviewed papers supporting the idea that Arctic Amplification of global warming is causing increased persistence of weather pattern at mid-latitudes and there are also peer reviewed papers that suggest there is no such effect.

    Personally I'll await more evidence before accepting or rejecting this particular (hypothesized) aspect of global warming.

  31. "Placeholder" .....

    or whatever your name is

    Has it ever occurred to you that what you characterize as "sanctimony" is nothing more than a perfectly reasonable criticism of your highly suspect standard of ethics?

    Look at it this way:

    Can you think of any single common criticism of Donald Trump that could actually substantively be characterized as "sanctimony" other than obliquely as a offence on the sanctity of the office he holds?

    No of course not. Even then and by a large margin it is Trump himself who "defiles" that particular sanctity, not anyone else. In this case there are clear norms of reasonable behaviour which you consistently transgress and that is even without the obvious dishonourable conduct of doing so anonymously.

    Which as I point out occurs in complete disrespect for the posted guidelines.

    To tell you the truth, when it comes to basic semantics, I think you really just need to go back and redo grade 10 English

  32. As far as I can determine, Placeholder has never made a meaningful substantive comment on weather or climate change. It is clear that he is not interested in doing that. Instead, his mission is to get people who may have differing political views angry with each other using various types of rhetorical manipulation. He has a standard set of talking points sprinkled with various types of disinformation and name-calling. The best thing is not to respond to him directly as you will only receive a vicious counterattack. Perhaps when it is apparent to him and everyone else (including whoever might be sponsoring his activity), he will leave.

  33. I would point out to Mr. Young that the"new" paper he cites (and hyped by Brietbart) is a couple of years old, only states that warming slowed down not paused, and has been superceded by two recent papers by most of the same authors stating that with more sophisticated statistical analysis and the addition of arctic temps. just becoming available the pause indeed did not happen:

    A fluctuation in surface temperature in historical context: reassessment and retrospective on the evidence
    James S Risbey1, Stephan Lewandowsky1,2, Kevin Cowtan3, Naomi Oreskes4, Stefan Rahmstorf5,6, Ari Jokimäki7 and Grant Foster8

    The 'pause' in global warming in historical context: (II). Comparing models to observations
    Stephan Lewandowsky1,2,3, Kevin Cowtan4, James S Risbey3, Michael E Mann5, Byron A Steinman6, Naomi Oreskes7 and Stefan Rahmstorf8,9

    Environmental Research Letters V. 13 #12

  34. Like others I am wanting to find out how the lower latitude effects of a disrupted polar vortex - due to Arctic warming - has been "firmly disproved".

    Those who forecast weather for the East Coast and Europe clearly think the vortex needs to be considered when developing their predictions - and is currently of concern.


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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