February 10, 2017

Global warming will bring milder weather to the Pacific Northwest

A recent article in the journal Climate Change analyzed how the number of mild days will change as the Earth warms due to human-caused global warming.

There are winners and losers, with most the world's population being losers, but for us here in the Northwest the changes will be favorable, with substantially more mild days, particularly in the spring and fall.

Before giving you the results, a few details.   The definition of mild weather in this paper is:
  • Daily maximum air temperature between 18 and 30 °C (64 to 86F).
  • Daily total precipitation not exceeding 1 mm (.04 inches).  This is not much.
  • Daily mean dew point temperature not exceeding 20 °C (68F).  High dew point are associated with sticky, humid conditions.
(If I was going the study, I would have had mild temperature ranging from 60 to 80F, precipitation not exceeding 2 mm, and dew point not exceeding 15°C, reflecting my Northwest U.S. tastes.)

This research made use the NOAA Climate Model (NOAA/GFDL HiFLOR global coupled model.) to project the world's climate for the rest of the century.  Their simulations assumed only modest growth in greenhouse gases (RCP4.5, for those that know about such things).

The following plots show the changes in the probability of mild days from now to 2081-2100) for each month, with blue indicating more mild days, and orange denoting fewer mild days.   In places with a warm climate (e.g., Miami), the changes are not good.  There are no mild days during summer in Miami. Quite frankly, temperatures changes is the least of Miami's global warming problems--rising sea level will probably flood the place.

Los Angeles and Denver, with cooler climates than Miami, will see improvement during winter and the adjacent months, with serious degradations during the warm months. Same thing for Chicago and New York City.

But Seattle is different.  We are real winners.  There will be substantial increases in the number of mild days from June to October, while the loss of mild days in mid-summer are relatively small.  But it is really better than that.  None of our winter days will be in the mild category (64 to 86F), but they will be considerably more pleasant than today (46 feels a lot warmer than 39F) .

And did you note the percentage of mild summer days in Seattle has been and will be around 70%...higher than almost any place else in the country any time of the year?  Only LA in November and May are as good.  And who would want to live in LA, anyway?

The Climate Change paper also took a global view, as shown in the figure below. Folks living in locations that are relative warm in summer (tropics, subtropics, India, SE Asia, SE U.S., China) will be losers.  That includes most of the Earth's population.  In contrast, Canada, Russian, the NW U.S., southeast Australia, lower South America, and northern Europe will be winners--more mild days.  Canada does particularly well.  Africa will be hit hard as will Brazil.

Western Washington and Oregon will relatively favored (at least in temperature) by global warming because we start off on the cool side, with warm extremes reduced by the cool eastern Pacific.  The warmer the land gets in summer, the more onshore (cool) flow develops--our natural air conditioning. And offshore (downslope) flow over the Cascades is predicted to decrease with global warming.

But although our temperatures will get progressively more pleasant during this century, other changes will not be as favorable, such as more extreme rainfall in winter, reduced snowpack, and worsened flooding in the fall.   So lessening the increase in greenhouse gases would certainly be in our own best interests.  You can always put on a sweater.


  1. I understand the "milder" part. .. But "What's Global Warming.?" ... I had "Global Amnesia" once (I think.) .. Is it, anything like "that".? (?)

  2. Reminds me of the song "It's Not the Meat it's the Motion"

  3. Nice story Cliff. But to change the subject what is up with the UW Probability Forecast? It showing very low high temperatures. For example today the forecast high is shown as 39 deg. NOAA is forecasting 48 and the current temperature is 46.

  4. Good new for bike commuters! Thanks auto drivers!

  5. awesome. i can't wait for the more mild days to melt off our pesky glaciers. total winners! i think we'll get tired off winning........

  6. "So lessening the increase in greenhouse gases would certainly be in our own best interests."

    I sure hope this isn't our only motivation for controlling greenhouse gasses. What about the interests of Africa, Central and South America, etc.? Not to mention the rest of our own country?

    I generally appreciate your level-headed treatment of climate change Cliff, but frankly, articles like this come off a little callous. Hooray, more good weather for us. Bummer about the rest of the planet, especially those whose lives are already miserable, and about to get a lot worse. We can just build walls to keep them out and let them fend for themselves.

    1. In the long run it will be a huge bummer for everyone. And with all the tracking happening everywhere it is going to happen faster than previously thought because the methane has a quicker effect.

  7. A good site to go after this article is the UW climate impacts group https://cig.uw.edu.

    The social impacts of this climate forecast will be profound. China and India becoming uninhabitable means inevitable northward migration into Russia or Europe. Brazil and other parts of South America will want to go farther south or north (here).

    Internal migrations will be increasing. Miami and San Diego will both be moving to Oregon and Washington. The water resources only exist on the west side and along the Columbia and Snake Rivers.

    Take a look around and say to your self these are the good old days because pleasant weather will not be pleasant if the population goes through the roof.

  8. Careful Cliff.

    POTUS may shut you down!

  9. Major bummer for trees that rely on deep freezes to kill off emerald ash borers and other invasive pests. Hopefully we don't wind up looking like the Sierra Nevadas someday.

  10. I am confused about the label "mild" vis-a-vis "warmer" or "hot". If a region will have less mild days in the summer does that mean there will be more hot days or more days that are cooler than before?

  11. Sorry if this is a duplicate comment. My comment was I need a more specific definition of "mild". Too subjective a term. If a locale will have fewer "mild" days in the summer, does that mean that it will be overall cooler in a place with a usually hot summer like in Denver, or does it mean that it will overall be hotter?

  12. Believing climate change will be good for western Washington is delusional. Any climate change: warmer, colder, wetter, dryer forces ecological change. The two back to back hot, dry summers of 2014 and 2015 killed several hundred small to medium Doug Firs in the forest surrounding my home on Vashon. An occasional thinning from a hot summer might be good but climate change is not.

    So yeah, great, I have lots of dry firewood this year. There were fewer mosquitoes in 2014 and 15. Good for me not so good for the birds and bats that eat them.

    What happens to our forests when summers like 2014 and 15 become normal. What happens when on top of the warmer norm we have a hotter than average summer (there will days when hot, dry down-sloping winds will occur). What will the new hottest days be like. Will the new hottest summers kill more than the small to medium Doug firs.

    Our forests will change in response to climate change.

    Life in the city where Cliff resides maybe better. More tomatoes, more BBQ days, greener grass but our natural ecosystem will suffer and it will change.

    Rising ocean levels will affect more than Florida. There are many homes and roads in the Puget Sound that are only a few feet above sea-level. There are salt marshes that will be flooded. There are forest areas that will become salty. Beaches becomes breakwater.

    If the changes occurred slowly then life in the tidal pools could gradually migrate up shore but the change will be fast.

    Scientists observing changes in the Arctic have complained that the models do not reflect reality. Changes to the Arctic ice pack are occurring faster than predicted by the models. Some scientists are predicting the Arctic summer ice pack could be gone as early as 2020. The current rate of ice volume loss suggests a summer melt-out around 2031.

  13. I think Cliff is a breath of fresh air! NOAA can't even predict weather for the next season, how can they predict for 100 years from now. Do we think that CO2 is the only thing that can drives climate?? What about the Sun, the oceans, volcanoes, etc etc. CA was supposed to be dry this winter and "global warming would really be bad for CA forever." Now we are flooding, have the highest rain and snow totals that we have seen in years. The amount of "global Temperature changes" predicted don't even come close to what the planet has had in the past. Let's get a little humble. We are just stupid human beings and the planet, the universe and nature abides by laws that we barely understand.
    Why is everything on the earth measured by how it affects us humans? How about when the world was all ice, the Sahara was gardens or 90% of all life forms were destroyed some millions of cycles ago. Let's get out of the way with regards to how we see the earth going through her natural cycles. Humble ourselves to Life. We are not in charge.

  14. All this points to one thing: Any change stresses the system. A cooling climate would do so too, in different ways.

    But I agree with you all who say we should not gloat. It certainly is not the time for that. For example if we lose the Everglades, that will be a loss for all.

    And yes, people may flock here. We are already overpopulated. People like mild. One time I visited the Mojave in August. Even the visitor center was closed.

    One thing puzzles me though. Why LESS summer offshore flow for W. Washington? Sounds like another version of the increased "June gloom" prediction. That isn't what happened in 2015, and I really hope it is wrong. We don't need less sun. If any good comes of GW, I hope we get more sun. But not less rain.

  15. Hi Mark,

    I was rather curious about the loss of your Douglas Fir trees during the summer of 2014 + 2015. The reason for my curiosity is that I'm in the South Eastern corner of Australia in the Macedon Ranges and I grow Douglas Firs here. Mate, summers here are way hotter than up in your part of the world. Slightly higher up the mountain range, there is a huge stand of mature Douglas Fir trees which were planted as a plantation a long time ago. The highest temperature I have seen here this summer is 39'C (102.2'F), but this year has been relatively mild and damp (unlike north of here where there is a record breaking heatwave) and so it does get even hotter here, but just not this year. The Douglas Fir's here shook off the heat and they all seem to be growing pretty well.

    Just a couple of thoughts I wanted to share with you about the deaths of your Douglas Firs. I was wondering whether the Douglas Firs in your part of the world were planted (or have grown) too densely and so in years of stress, there is a die-off of the trees that are less able to compete with their better established peers?

    And also the mountain range here is a volcanic massif and so I enjoy deep loamy mineral rich volcanic soils (as do the Douglas Firs here) and I was also wondering about your soil fertility as in years of climate stress and poor soils, lack of access to water and soil fertility can lead to die-back of less well established trees. That happens to the eucalyptus trees down this way, despite their ferocious reputations.

    Dunno, just a couple of thoughts for you.


  16. JAPAN?! No real change? Wow! Given their very humid summers (with dewpoints regularly in the mid to upper 70s), one would've expected differently..

    I agree with the above comments that any change should not be welcomed for merely being more comfortable.. this area of the country has especially beautiful scenery and nature, and I would not want to trade that in for simple comfort or convenience

  17. JOEL SAID ...cInternal migrations will be increasing. Miami and San Diego will both be moving to Oregon and Washington. The water resources only exist on the west side and along the Columbia and Snake Rivers.

    Thanks Joel! My wife and I are some of those 'immigrants' to WA and OR. We are fleeing Los Angeles. Your info was very useful.

    The climate changes for people in China and Brazil are very bad news. Brazil gets by because it is highly productive and food prices are low. If that changes, the impact on both S. America and Europe (which imports a huge amount of Brazilian crops) will e very big.

  18. So with climate change, will it also make our arctic outbreaks more extreme? Since those giant ridges of high pressure over Alaska and Greenland that then shunt the polar air over the PNW will be more pronounced due to increased buckling of the jet stream?


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

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