Is Atmospheric Condition Whiplash Increasing Inwards California?
This calendar week a newspaper was released inwards Nature Climate Change past times Daniel Swain in addition to co-authors that made a bold claim: that California is experiencing in addition to volition increasingly sense "weather whiplash" because of anthropogenic global warming.
They define "weather whiplash" or "precipitation whiplash" every bit a transition from a much drier than normal twelvemonth to a much wetter than normal year, such every bit the alter that occurred betwixt the winters of 2015-2016 in addition to 2016-2017.
As 1 mightiness expect, alongside such an explosive claim in addition to graphic metaphor, the media would instruct wild over it. They did. Headlines describing the civilization-testing whiplash were establish inwards media outlets across the world, from the forepart page of the LA Times to CNN in addition to fifty-fifty made Dan Rather's blog. Environmental activists website covered this revelation inwards depth.
But I suspect most reporters did non read the paper, in addition to every bit I volition depict below, this move suffers from substantial problems in addition to claims that are at the best excessive, fifty-fifty using the model simulations they describe. And the results are exclusively based on model results that don't seem to gibe good alongside what has happened inwards the existent world.
The Claims
Swain et al.'s claims of a atmospheric precipitation whiplash is based only on climate model output in addition to then is only every bit proficient every bit the model. Specifically, they used a 40-member collection of forecasts (an ensemble) using the Community basis System Model (CESM). This is a global model developed at the National Center for Atmospheric Research. I am quite familiar alongside CESM in addition to guide hold used its output inwards some of my ain work. It is run at around 1° horizontal resolution (about 111 km) in addition to thus is unable to copy the details of western the United States of America atmospheric precipitation in addition to weather condition systems.
The Definition of whiplash used inwards this newspaper is a combat arcane in addition to one-sided.
Specifically, they only considered a whiplash from dry out to moisture conditions. For some argue they did non mean value a moisture to dry out whiplash was important.
Swain in addition to colleagues looked at the distribution of atmospheric precipitation inwards the model during a pre-industrial menstruation (before 1850) in addition to establish the top 20% in addition to bottom 20% atmospheric precipitation years. With those numbers they examined CESM climate simulations, encompassing most of the 20th in addition to 21st centuries, that was driven past times an aggressive (probably besides aggressive) increment of greenhouse gases (RCP 8.5 inwards climate modeler lingo), looking for the frequency of changes from dry out (the bottom 20% earlier 1850) to moisture (top 20% earlier 1850) years. And they did this for each ensemble fellow member in addition to thus were able to instruct the alter inwards frequencies of this one-sided whiplash every bit the model simulations forced past times increasing greenhouse gases.
Their results are establish inwards the figure below for some model grid boxes inwards southern in addition to northern CA (they don't actually specify inwards the newspaper just where), showing the alter inwards frequency of dry out to moisture atmospheric precipitation whiplash events. Influenza A virus subtype H5N1 stair out of the attain of climate model whiplashes are shown past times the majestic shading (67% of the simulations are inside the shaded areas in addition to majestic occupation shows the ensemble hateful (which has been smoothed or averaged over time)).
So, what does their analysis of the models show?
For northern California, not much. Influenza A virus subtype H5N1 refuse inwards whiplash inwards the 1970s, an increment from roughly 2015 to 2025, in addition to non much alter for the side past times side xxx years. According to their ain analysis, the changes inwards northern CA are NOT statistically significant. And maintain inwards withdraw heed that most of California's reservoir capacity is inwards the north.
For southern CA, at that spot is an sudden alter from reducing whiplash to a really irksome steady ascent starting around 1985, alongside the whiplash remaining quite little until mid-century. Considering that the envelope of dubiety encompasses zilch alter until around 2050, I am sure the alter would NOT endure statistically pregnant through that time. As shown later, this development inwards southern CA does NOT compare good alongside observations through 2018, where at that spot is no trend. And inwards whatever case, southern CA has few large reservoirs in addition to only a little total of California agriculture.
In general, at that spot newspaper shows non much alter inwards the number of dry out years but increasing moisture years for the northern 2 thirds of the dry soil every bit nosotros move along into the minute one-half of the century.
What has Actually Occurred alongside Precipitation Whiplashes
Here is the average wet-season (November-March) atmospheric precipitation for California from 1936-2018 from the NOAA/NWS Division information available from the wonderful NOAA ESRL website. This plot in addition to subsequent plots were made past times UW Atmospheric Sciences staff member, Neal Johnson. Why did nosotros outset inwards 1936? Because the ESRL website said at that spot were issues earlier 1935.
Not much tendency inwards CA precipitation, but enough of ups in addition to downs---now known every bit whiplash, I guess.
Anyway, since this is science, let's practice a WHIPLASH INDEX (WI) that is just divergence betwixt 1 year's atmospheric precipitation in addition to that of the twelvemonth earlier (shown below). (Note, the right pronunciation of WI is "why"). Now this is a combat different than Swain et al. whiplash plot (they showed the frequency of increases of atmospheric precipitation betwixt really dry out years (bottom 20%) in addition to moisture years (top 20%). But my index is much easier to sympathise in addition to is to a greater extent than informative. And my index is based on OBSERVATIONS inwards the REAL WORLD different the model-based whiplash guidance inwards the Swain et al. paper.
What is clearly apparent is that it is difficult to give away evidence of an increment inwards aAmplitude inwards the whiplash index based on observations. Now, if nosotros facial expression at the tendency of increases inwards atmospheric precipitation (above the dashed line)--which is really similar to Swain et al's approach-- there is no evidence of increasing dry out to moisture years. In fact, at that spot are LESS of them during the past times 2 decades...and to a greater extent than inwards the decades before.
Or facial expression at the moisture to dry out transitions---no evidence of whatever trend.
But let's accept this 1 footstep further, Swain et al. divided their whiplashes into southern in addition to northern California. Let's practice amend than that (a UW Husky volition ever travail to improve upon a UCLA Bruin)--- let's calculate the whiplash index for southern, central, in addition to northern California (below).
These results are really important--they demo at that spot is NO increment inwards atmospheric precipitation whiplash for whatever sub-region of California WHEN ONE LOOKS AT WHAT ACTUALLY HAPPENED.
In contrast, the model output applied inwards Swain et al shows that at that spot is an increment inwards whiplash events starting around 1985 inwards southern CA in addition to 2005 inwards northern CA. The clear decision is that something is amiss alongside the model inwards predicting California precipitation. And therefore, the predictions used inwards this newspaper are suspect.
The fact that the model is non getting the twelvemonth past times twelvemonth variability right for California atmospheric precipitation is hardly surprising. West Coast atmospheric precipitation is modulated past times El Nino/La Nina in addition to teleconnections (remote physical connections) forced past times convection inwards the tropics. And such low-resolution models practice a pitiable task on tropical convection in addition to thus volition mess upwards the teleconnections. I know a lot close this because I am actively working inwards this area. And at that spot is a agency to ready the problem...but it takes huge estimator resources.
But fifty-fifty if their model output was correct, I would debate that they in addition to sure enough the media are agency overhyping these results. In fact, at human face upwards value their predictions are good intelligence for California. According to their results, the increment of whiplash events inwards northern California is slight in addition to is non significantly pregnant at fifty-fifty the depression 90% pregnant marking (more studies role 95% significance). And most of the reservoir capacity inwards California is inwards the northern part of the state.
They also demo that at that spot volition endure an increment inwards wintertime atmospheric precipitation over fourth dimension across most of California. Now California (unlike Washington) has huge multi-year storage capacity, then fifty-fifty if their model is right in addition to at that spot was to a greater extent than twelvemonth to twelvemonth variability, California would endure fine....they just volition shop the H2O from the moisture years.
There are a lot of other technical issues alongside the newspaper I could convey up, but the bottom occupation is clear:
(1) observations over the past times lxxx years practice non demo an increment inwards atmospheric precipitation whiplash inwards California fifty-fifty though the effects of global warming guide hold begun.
(2) their model results are inconsistent alongside observed trends
(3) fifty-fifty if they are right, the implications are positive, non negative. California volition guide hold to a greater extent than H2O over time.
Now it is truthful that temperatures volition increment in addition to that volition drive to a greater extent than evaporation in addition to drying. Sierra snowpack volition refuse (but the H2O volition even then endure at that spot every bit rain). So California volition in all probability desire to add together to a greater extent than reservoir capacity in addition to waste matter less H2O (more drip irrigation, less crazy H2O loving crops). They could fifty-fifty force H2O cloak-and-dagger during moisture years. This is a solvable work in addition to non a existential threat. Weather whiplash volition in all probability endure the to the lowest degree of their problems.
This "whiplash" frenzy inwards the media shows a major failure fashion inwards our conversations close global warming. Some researchers analyze purely model results. They don't compare the model output alongside observations. They give away some pocket-size changes inwards the model projections in addition to somewhat inflate the importance inwards their paper. The media in addition to sure involvement groups hype upwards the results alongside large headlines.
As a result, the populace is exposed to essentially wrong information in addition to gets turned off past times some other apocalyptic prediction. And such pitiable communication gets inwards the agency of properly dealing alongside climate change, a serious issue, inwards a rational, fact-based way.
They define "weather whiplash" or "precipitation whiplash" every bit a transition from a much drier than normal twelvemonth to a much wetter than normal year, such every bit the alter that occurred betwixt the winters of 2015-2016 in addition to 2016-2017.
As 1 mightiness expect, alongside such an explosive claim in addition to graphic metaphor, the media would instruct wild over it. They did. Headlines describing the civilization-testing whiplash were establish inwards media outlets across the world, from the forepart page of the LA Times to CNN in addition to fifty-fifty made Dan Rather's blog. Environmental activists website covered this revelation inwards depth.
But I suspect most reporters did non read the paper, in addition to every bit I volition depict below, this move suffers from substantial problems in addition to claims that are at the best excessive, fifty-fifty using the model simulations they describe. And the results are exclusively based on model results that don't seem to gibe good alongside what has happened inwards the existent world.
The Claims
Swain et al.'s claims of a atmospheric precipitation whiplash is based only on climate model output in addition to then is only every bit proficient every bit the model. Specifically, they used a 40-member collection of forecasts (an ensemble) using the Community basis System Model (CESM). This is a global model developed at the National Center for Atmospheric Research. I am quite familiar alongside CESM in addition to guide hold used its output inwards some of my ain work. It is run at around 1° horizontal resolution (about 111 km) in addition to thus is unable to copy the details of western the United States of America atmospheric precipitation in addition to weather condition systems.
Specifically, they only considered a whiplash from dry out to moisture conditions. For some argue they did non mean value a moisture to dry out whiplash was important.
Swain in addition to colleagues looked at the distribution of atmospheric precipitation inwards the model during a pre-industrial menstruation (before 1850) in addition to establish the top 20% in addition to bottom 20% atmospheric precipitation years. With those numbers they examined CESM climate simulations, encompassing most of the 20th in addition to 21st centuries, that was driven past times an aggressive (probably besides aggressive) increment of greenhouse gases (RCP 8.5 inwards climate modeler lingo), looking for the frequency of changes from dry out (the bottom 20% earlier 1850) to moisture (top 20% earlier 1850) years. And they did this for each ensemble fellow member in addition to thus were able to instruct the alter inwards frequencies of this one-sided whiplash every bit the model simulations forced past times increasing greenhouse gases.
Their results are establish inwards the figure below for some model grid boxes inwards southern in addition to northern CA (they don't actually specify inwards the newspaper just where), showing the alter inwards frequency of dry out to moisture atmospheric precipitation whiplash events. Influenza A virus subtype H5N1 stair out of the attain of climate model whiplashes are shown past times the majestic shading (67% of the simulations are inside the shaded areas in addition to majestic occupation shows the ensemble hateful (which has been smoothed or averaged over time)).
So, what does their analysis of the models show?
For northern California, not much. Influenza A virus subtype H5N1 refuse inwards whiplash inwards the 1970s, an increment from roughly 2015 to 2025, in addition to non much alter for the side past times side xxx years. According to their ain analysis, the changes inwards northern CA are NOT statistically significant. And maintain inwards withdraw heed that most of California's reservoir capacity is inwards the north.
For southern CA, at that spot is an sudden alter from reducing whiplash to a really irksome steady ascent starting around 1985, alongside the whiplash remaining quite little until mid-century. Considering that the envelope of dubiety encompasses zilch alter until around 2050, I am sure the alter would NOT endure statistically pregnant through that time. As shown later, this development inwards southern CA does NOT compare good alongside observations through 2018, where at that spot is no trend. And inwards whatever case, southern CA has few large reservoirs in addition to only a little total of California agriculture.
In general, at that spot newspaper shows non much alter inwards the number of dry out years but increasing moisture years for the northern 2 thirds of the dry soil every bit nosotros move along into the minute one-half of the century.
What has Actually Occurred alongside Precipitation Whiplashes
Here is the average wet-season (November-March) atmospheric precipitation for California from 1936-2018 from the NOAA/NWS Division information available from the wonderful NOAA ESRL website. This plot in addition to subsequent plots were made past times UW Atmospheric Sciences staff member, Neal Johnson. Why did nosotros outset inwards 1936? Because the ESRL website said at that spot were issues earlier 1935.
Not much tendency inwards CA precipitation, but enough of ups in addition to downs---now known every bit whiplash, I guess.
Anyway, since this is science, let's practice a WHIPLASH INDEX (WI) that is just divergence betwixt 1 year's atmospheric precipitation in addition to that of the twelvemonth earlier (shown below). (Note, the right pronunciation of WI is "why"). Now this is a combat different than Swain et al. whiplash plot (they showed the frequency of increases of atmospheric precipitation betwixt really dry out years (bottom 20%) in addition to moisture years (top 20%). But my index is much easier to sympathise in addition to is to a greater extent than informative. And my index is based on OBSERVATIONS inwards the REAL WORLD different the model-based whiplash guidance inwards the Swain et al. paper.
What is clearly apparent is that it is difficult to give away evidence of an increment inwards aAmplitude inwards the whiplash index based on observations. Now, if nosotros facial expression at the tendency of increases inwards atmospheric precipitation (above the dashed line)--which is really similar to Swain et al's approach-- there is no evidence of increasing dry out to moisture years. In fact, at that spot are LESS of them during the past times 2 decades...and to a greater extent than inwards the decades before.
Or facial expression at the moisture to dry out transitions---no evidence of whatever trend.
But let's accept this 1 footstep further, Swain et al. divided their whiplashes into southern in addition to northern California. Let's practice amend than that (a UW Husky volition ever travail to improve upon a UCLA Bruin)--- let's calculate the whiplash index for southern, central, in addition to northern California (below).
Northern CA
Central CA
Southern CA
These results are really important--they demo at that spot is NO increment inwards atmospheric precipitation whiplash for whatever sub-region of California WHEN ONE LOOKS AT WHAT ACTUALLY HAPPENED.
In contrast, the model output applied inwards Swain et al shows that at that spot is an increment inwards whiplash events starting around 1985 inwards southern CA in addition to 2005 inwards northern CA. The clear decision is that something is amiss alongside the model inwards predicting California precipitation. And therefore, the predictions used inwards this newspaper are suspect.
The fact that the model is non getting the twelvemonth past times twelvemonth variability right for California atmospheric precipitation is hardly surprising. West Coast atmospheric precipitation is modulated past times El Nino/La Nina in addition to teleconnections (remote physical connections) forced past times convection inwards the tropics. And such low-resolution models practice a pitiable task on tropical convection in addition to thus volition mess upwards the teleconnections. I know a lot close this because I am actively working inwards this area. And at that spot is a agency to ready the problem...but it takes huge estimator resources.
But fifty-fifty if their model output was correct, I would debate that they in addition to sure enough the media are agency overhyping these results. In fact, at human face upwards value their predictions are good intelligence for California. According to their results, the increment of whiplash events inwards northern California is slight in addition to is non significantly pregnant at fifty-fifty the depression 90% pregnant marking (more studies role 95% significance). And most of the reservoir capacity inwards California is inwards the northern part of the state.
They also demo that at that spot volition endure an increment inwards wintertime atmospheric precipitation over fourth dimension across most of California. Now California (unlike Washington) has huge multi-year storage capacity, then fifty-fifty if their model is right in addition to at that spot was to a greater extent than twelvemonth to twelvemonth variability, California would endure fine....they just volition shop the H2O from the moisture years.
There are a lot of other technical issues alongside the newspaper I could convey up, but the bottom occupation is clear:
(1) observations over the past times lxxx years practice non demo an increment inwards atmospheric precipitation whiplash inwards California fifty-fifty though the effects of global warming guide hold begun.
(2) their model results are inconsistent alongside observed trends
(3) fifty-fifty if they are right, the implications are positive, non negative. California volition guide hold to a greater extent than H2O over time.
Now it is truthful that temperatures volition increment in addition to that volition drive to a greater extent than evaporation in addition to drying. Sierra snowpack volition refuse (but the H2O volition even then endure at that spot every bit rain). So California volition in all probability desire to add together to a greater extent than reservoir capacity in addition to waste matter less H2O (more drip irrigation, less crazy H2O loving crops). They could fifty-fifty force H2O cloak-and-dagger during moisture years. This is a solvable work in addition to non a existential threat. Weather whiplash volition in all probability endure the to the lowest degree of their problems.
As a result, the populace is exposed to essentially wrong information in addition to gets turned off past times some other apocalyptic prediction. And such pitiable communication gets inwards the agency of properly dealing alongside climate change, a serious issue, inwards a rational, fact-based way.
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