There is a lot of incorrect information and false claims regarding the recent heavy rain and flooding in the Pacific Northwest.
Claims that the recent heavy rain events were unprecedented or that global warming (climate change from human emissions of greenhouse gases) was a major contributor.
The truth is that there is a long history of similar and larger events.
The truth, supported by extensive evidence, is that global warming played a very minor role, if any.
False
False
Major Flooding Events Often Occur in the Northwest
Heavy rain and massive flooding are frequent visitors to our region, and THERE IS NO EVIDENCE THAT MAJOR EVENTS ARE INCREASING in intensity or frequency.
For example, in February 1996, major flooding in Oregon and Washington resulted in over a billion dollars of loss.
The Willamette Valley flooded in 1996
The 2006 flood event destroyed many roads and bridges in Mount Rainier Park, with massive damage along the Skagit and Cowletz rivers.
Mt. Rainier Park, 2006
If global warming were a significant contributor to Northwest flooding, then flooding events would become more frequent or intense.
This is not happening.
Precipitation is not increasing
Most of the arguments for a global warming origin of heavy rain depend on arguments about the atmosphere "holding" more water as temperatures increase.
The problem with this claim is that many other factors modulate the location, intensity, and longevity of atmospheric rivers and their ability to produce heavy precipitation.
Let's evaluate these claims by looking at the ACTUAL changes in precipitation over our region.
Below is the wet season (November through February) annual precipitation over Washington State for 1895-2024 (below).
There is NO UPWARD trend, even as the planet warms.
Is the number of days with heavy rain increasing in our region?
The data says no.
To illustrate, this figure shows the number of days with heavy (2 inches or more) precipitation at Stampede Pass in the central WA Cascades. NO UPWARD trend in apparent. If anything, it is going down.
I have looked at many other stations...same story...no increase.
Not convinced yet?
Let me show you something only my research group has at this time: high-resolution regional climate simulations in which greenhouse gases are increasing substantially (the RCP4.5 scenario).
This figure shows the change in the annual highest 5 days of precipitation between 2070-2100 and 1970-2000.
Very little change over WA State, but drier in CA.
Finally, there is ANOTHER major error regarding global warming and flooding in the claims noted above....in this case, dealing with snow.
Their argument is that warming causes less snow, and snow "soaks up" the precipitation, thus lessening flooding.
Wrong. As noted by distinguished regional hydrometeorological expert Professor Dennis Lettenmaier, less snow meant LESS SNOWMELT, which REDUCES the amount of water for flooding.
In short, there are a lot of false claims about the relationship between global warming and local flooding.
The truth:
Northwest flooding is not increasing in frequency.
Northwest flooding is not getting worse.
There is little change in precipitation amounts or intensity during the past decades over the region as the Earth has slowly warmed.
Truth does matter.
Do forecast models consider tropical atmospheric effects, or are the models more local to the PNW?
ReplyDeleteJapan Meteorological Agency officials, as reported by NHK, linked intense Southeast Asian rainfall to Cyclone Senyar forming in the Strait of Malacca, driven by high sea-surface temperatures near Indonesia and cooler waters on the western side of the region. This temperature contrast across the strait prompted warm, moist air to flow eastward, fueling heavy precipitation exceeding 900 mm in parts of Indonesia.
Recent floods in late November 2025 struck Indonesia, the Philippines, Vietnam, Thailand, Malaysia, and Sri Lanka, killing over 1,600 people and causing $20 billion in damage from cyclones like Senyar, Ditwah, and Koto. Senyar was unusual as it intensified near the equator in the Malacca Strait between Sumatra and Malaysia, where weak winds normally prevent cyclone formation.
I so appreciate your perspective professor Mass. Please comment on the melting of glaciers and how that impacts overall climate, etc.
ReplyDelete"Behind Everything We Publish, The Inescapable Specter of Our Addiction To Yellow Journalism"
ReplyDeleteThank you for setting the record straight. Anyone who has lived in the Northwest long enough and is old enough to remember some of the big rainfall and flood events of the 1980s and 1990s knew full well that these "atmospheric rivers" weren't anything new or unprecedented. It's often the media that overuses these new (to them) jargon for weather events. Bomb cyclone and heat dome are two more that are often overused by the happy-to-clickbait media.
ReplyDeleteYes I agree: There is too much hype. I never heard of a "bomb cyclone" or a "heat dome" until a few years ago.
DeleteI’d also never experienced 122+ degrees in Canada pre-heat dome. It was an exceptional event.
DeleteOnce again, the use of science based evidence refutes the Climste Lab claims. The art of selling newspapers often stretches or ignores the truth. And MSM wonders why their influence is waning?
ReplyDeleteCheck table 12.12 chapter 12 AR6, and you will find that you are right: no statistically significant correlation to AGW
ReplyDeleterains too much = climate change. rains too little = climate change.
ReplyDeleteIn theory, changing climate can result in excessive precipitation and droughts in different parts of the world or during different seasons. Of course, rain existed before, and not every weather event is directly attributable to climate change. Weather is local and short-term, climate is regional and long-term. It is complicated. But our world's temperatures continue to rise, so we need to cut GHG emissions.
DeleteThanks for continuing to speak clearly with data supported information and points of view. Keep it up. The Seattle Times is clearly not interested in that approach, which you have stated often and loudly.
ReplyDeleteReguardless of the idealogy with all this, we need find the poltical will to build means of controlling these floods a bit better. Better levees and flood control gates. Flood tunnels. More reserviors in the foot hills and mountains.Telling develpers "No" when proposals to build in flood plains come up for review. It doesn't matter if its climate change or not. The end result is a cycle of destruction, insurance paying for it to be rebuilt (wrong) exactly the same, it floods again...and cycle repeats.
ReplyDeleteI don't see anything changing, though. The tribes will complain about fish and developers always seem to win. Money, money, money!
I work in Ferndale and we keep an close eye on the Nooksack as, when the stage climbs up toward major flood (23' on the USGS gauge), things can get pretty ugly. The major flood during mid-November 2021 reached the highest stage at the Ferndale gauge since 11/27/1963 and was a real shock/wakeup call for those living in and near the floodplain of the lower mainstem of the river.
ReplyDeleteHistorically, major flood stage at Ferndale has been rather rare with only 17 instances of such an occurrence during the >century of records at that location. However, flooding of this magnitude was actually much more common from the early to mid-20th century with major flood stage being reached about every 3 years on average. Interestingly, since the early early 1960s, major flood stage at the Ferndale gauge has decreased in frequency by a factor of 9. Between 1917 and 1963, major flood stage was reached a total of 15 times, becoming especially common during the 1950s and early 1960s. In fact, major flood stage was reached on 4/30/1959 and then *again* on 11/23/1959! Since 1963, though, major flood stage has occurred just twice: the first time was 11/10/1990 and the second, and most recent, was 11/16/2021.
While November is the most common month among the 17 major floods with 7 having occurred during that month, the very worst floods, which occurred during 1951, 1917, 1932, 1935, 1945, 1921, 1955, 1961, 1959, and 1949 often took place during December, January, and February. An examination of weather records antecedent to these floods suggests that they were precipitated by major rain-on-snow events where snowpack often extended down nearly to sea level and deepened rapidly even at lower and moderate elevations in the mountain valleys. The modern major floods, on the other hand, have been driven almost entirely by excessive precipitation in the form of damaging atmospheric rivers with little runoff contribution from melting snowpack.
So, it appears thanks to global warming, that major flooding on the lower mainstem of the Nooksack has actually been attenuated, both in frequency as well as magnitude, due to the decrease in cold temperatures and snowfall, say, from around sea level up to 1000-2000' elevation.
We do, of course, still occasionally get significant snow in the band between sea level and 1000-2000' and we obviously are subject to extreme and damaging atmospheric rivers, but the risk of a catastrophic rain-on-snow event is a shadow of what it once was because the likelihood of significant low-mid elevation snowpack has become so low that the probability of an extreme and damaging atmospheric river occurring while significant low-mid elevation snowpack exists has become vanishingly small.
We should count our blessings for this small mercy as, based on the historical data, the flooding that the Ferndale area once experienced on relatively regular basis truly puts to shame anything that has occurred in living memory. As an example, the catastrophic flood of February 1951, resulting from an extreme rain-on-snow event, reached a stage more than *7-feet* above the disastrous November 2021 flood!
How about the conflicting wind models for Christmas Eve
ReplyDeleteMy question too.
DeleteMost of those who call themselves journalists are in competition not with the truth but with each other. And when your livelihood depends on being published, you don't make yourself a target by parting from the heard. I'd likely do the same. Be skeptical.
DeleteYes, multiple sources say winds up to 70 mph *possible on Christmas Eve. In Seattle? Might you be reporting on this Cliff? We much appreciate and rely upon your accurate weather forecasts!
ReplyDeleteYou address the precipitation and how it has changed (or not) over time which I appreciate. I do have two questions:
ReplyDelete1) For the flooding events in 1996 and 2006, how does the amount and type of precipitation (for those areas at the time) compare to this recent event, in terms of actual inches hitting the ground where the flooding occurred over the same time period? I realize with the 2006 flooding this is complicated by the rain on snow situation given this happened on the mountain.
2) More significant, in my mind, and others I’ve talked to during and since this recent event is the fact that all of this precipitation fell as rain instead of snow. What do your climate models show regarding temperature (instead of precip) changes for the month of December? It seems like it is much warmer than the past (such that the precip fell mostly as rain instead of snow… especially if you look at Snoqualmie Pass for example); if it had fallen as snow it would also have been epic but likely not resulted in such short term flooding.
Thank you.
More silly global warming probes. It's just bull shit to me. There's always flooding to some degree around Thanksgiving. Just shut the hell up and go away already with your manipulative Darwinism.
DeleteWell, parts of the US-2 highway (east-west crossing over Cascades) have been washed out and collapsed in some places, so US.2 remains closed at Skykomish, no access to Stevens Pass from the west.
DeleteThey have just reopened one lane to get to the ski resort from the East side, only if guided by a pilot car. Still no roadway between Skykomish and Leavenworth on the other side of the Cascades, and the mayors said it will take several months to rebuild. Global heating or not, I remember those flash floods in Texas, Spain and in Germany a few years ago. It can be pretty serious for the folks who live in the affected area. Weather forecasts save lives.