crown capital management environmental monitoring on how climate change is worsening california

8/13/2019 Crown Capital Management Environmental Monitoring on How Climate Change is Worsening California

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Crown Capital management environmental monitoring onHow Climate Change Is Worsening California’s Epic Drought

Leading Scientists Explain:

Scientists have long predicted that climate change would bring on ever-worsening droughts,especially in semi-arid regions like the U.S. Southwest. As climatologist James Hansen, whoco-authored one of the earliest studies on this subject back in 1990, told me this week,“Increasingly intense droughts in California, all of the Southwest, and even into the Midwesthave everything to do with human- made climate change.” Why does it matter if climate change is playing a role in the Western drought? As one topresearcher on the climate- drought link reconfirmed with me this week, “The U.S. may never

again return to the relatively wet conditions experienced from 1977 to 1999.” If his and otherprojections are correct, then there may be no greater tasks facing humanity than

1) working to slash carbon pollution and avoid the worst climate impact scenarios and

2) figuring out how to feed nine billion people by mid-century in a Dust-Bowl-ifying world.

Remarkably, climate scientists specifically predicted a decade ago that Arctic ice loss wouldbring on worse droughts in the West, especially California. As it turns out, Arctic ice loss hasbeen much faster than the researchers — and indeed all climate modelers — expected.And, of course, California is now in the death-grip of a brutal, record-breaking drought,driven by the very change in the jet stream that scientists had anticipated. Is this just anamazing coincidence — or were the scientists right? And what would that mean for thefuture? Building on my post from last summer, I talked to the lead researcher and several

other of the world’s leading climatologists and drought experts.

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First, a little background. Climate change makes Western droughts longer and stronger andmore frequent in several ways, as I discussed in my 2011 literature review in the journalNature:

Precipitation patterns are expected to shift, expanding the dry subtropics. Whatprecipitation there is will probably come in extreme deluges, resulting in runoff rather thandrought alleviation. Warming causes greater evaporation and, once the ground is dry, theSun’s energy goes into baking the soil, leading to a further increase in air t emperature. Thatis why, for instance, so many temperature records were set for the United States in the1930s Dust Bowl; and why, in 2011, drought-stricken Texas saw the hottest summer everrecorded for a US state. Finally, many regions are expected to see earlier snowmelt, so lesswater will be stored on mountain tops for the summer dry season.I labeled this synergy Dust-Bowlification. The West has gotten hotter thanks to globalwarming, and that alone is problematic for California.

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“The extra heat from the increase in heat trapping gases in the atmosphere over six monthsis equivalent to running a small microwave oven at full power for about half an hour overevery square foot of the land under the drought,” climatologist Kevin Trenberth explainedto me via email, during a drought. “No wonder wild fires have increased! So climate change

undoubtedly affects the intensity and duration of drought, and it has consequences.California must be very vigilant with regard to wild fires as the spring arrives.”

And then we have the observed earlier snow melt, which matters in the West because itrobs the region of a reservoir needed for the summer dry season — see “US GeologicalSurvey (2011): Global Warming Drives Rockies Snowpack Loss Unrivaled in 800 Years,Threat ens Western Water Supply” and “USGS (2013): Warmer Springs Causing Loss Of SnowCover Throughout The Rocky Mountains.”

Climate change undoubtedly affects the intensity and duration of drought, and it hasconsequences.

As climatologist and water expert Peter Gleick noted to me, quite separate from the impactof climate change on precipitation, “look at the temperature patterns here, which areleading to a greater ratio of rain-to-snow, faster melting of snow, and greater evaporation.Those changes alone make any drought more intense.” But what of the possibility that climate change is actually contributing to the reduction in

rainfall? After all, as Daniel Swain has noted, “calendar year 2013 was the driest on record inCalifornia’s 119 year formal record, and likely the driest since at least the Gold Rush era.” Trenberth explained that, according to climate models, “some areas are more likely to getdrier including the SW: In part this relates a bit to the wet get wetter and dry get driersyndrome, so the subtropics are more apt to become drier. It also relates to the expansionand poleward shift of the tropics.” Back in 2005, I first heard climatologist Jonathan Overpeck discuss evidence thattemperature and annual precipitation had started to head in opposite directions in the U.S.

Southwest, which raises the question of whether we are at the “dawn of the super -interglacial drought.” Overpeck, a leading drought expert at the University of Arizona,warned “climate change seldom occurs gradually.”

What’s going on in the Southwest is what anthropogenic global warming looks like for theregion.

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In a major 2008 USGS report, Abrupt Climate Change, the Bush Administration (!) warned:“In the Southwest, for example, the models project a permanent drying by the mid -21stcentury that reaches the level of aridity seen in historical droughts, and a quarter of theprojections may reach this level of aridity much earlier.”

In 2011 US Senate testimony, Overpeck stated:There is broad agreement in the climate science research community that the Southwest,including New Mexico, will very likely continue to warm. There is also a strong consensusthat the same region will become drier and increasingly snow-free with time, particularly inthe winter and spring. Climate science also suggests that the warmer atmosphere will leadto more frequent and more severe (drier) droughts in the future. All of the above changeshave already started, in large part driven by human-caused climate change.Overpeck told me this week, “because I think the science only gets stronger with time, I’ll

stick to my statements that you quote.” He added, “what’s going on in the Southwest iswhat anthropogenic global warming looks like for the region.” Beyond the expansion and drying of the subtropics predicted by climate models, someclimatologists have found in their research evidence that the stunning decline in Arctic seaice would also drive western drought — by shifting storm tracks.“Given the very large reductions in Arctic sea ice, and the heat escapi ng from the Arcticocean into the overlying atmosphere, it would be surprising if the retreat in Arctic sea ice did*not* modify the large- scale circulation of the atmosphere in some way,” Michael Mann,director of the Earth System Science Center at Pennsylvania State University, told me this

week. “We now have a healthy body of research, ranging from Lisa Sloan’s and JacobSewall’s work a decade ago, to Francis’s more recent work, suggesting that we may indeedbe seeing already this now in the form of more persistent anomalies in temperature, rainfall,and drought in North America.”



Back in 2004, Lisa Sloan, professor of Earth sciences at UC Santa Cruz, and her graduatestudent Jacob Sewall published an article in Geophysical Research Letters, “Disappearing

Arctic sea ice reduces available water in the American west” (subs. req’d). As the news release at the time explained, they “used powerful computers running a globalclimate model developed by the National Center for Atmospheric Research (NCAR) tosimulate the effects of reduced Arctic sea ice.” And “their most striking finding was asignificant reduction in rain and snow fall in the American West.” “Where the sea ice is reduced, heat transfer from the ocean warms the atmosphere,resulting in a rising column of relatively warm air,” Sewall said. “The shift in storm tracksover North America was linked to the formation of these columns of warmer air over areasof reduced sea ice in the Greenland Sea and a few other locations.” Last year, I contacted Sloan to ask her if she thought there was a connection between thestaggering loss of Arctic sea ice and the brutal drought gripping the West, as her researchpredicted. She wrote, “Yes, sadly, I think we were correct in our findings, and it will only beworse with Arctic sea ice diminishing quickly.”



This week, Sewall wrote me that “both the pattern and even the magnitude of the a nomalylooks very similar to what the models predicted in the 2005 study (see Fig. 3a).” Here is whatSewall’s model predicted in his 2005 paper, “Precipitation Shifts over Western NorthAmerica as a Result of Declining Arctic Sea Ice Cover”:

Figure 3a: Differences in DJF [winter] averaged atmospheric quantities due to an imposed

reduction in Arctic sea ice cover. The 500-millibar geopotential height (meters) increases by upto 70 m off the west coast of North America. Increased geopotential height deflects stormsaway from the dry locus and north into the wet locus

“Geopotential height” is basically the height above mean sea level for a given pressure level.The “500 mb level is often referred to as the steering level as most weather systems an dprecipitation follow the winds at this level…. This level averages around 18,000 feet abovesea level and is roughly half-way up through the weather producing part of the atmospherecalled the troposphere.” Now here is what the 500 mb geopotential height anomaly looked like over the last year, viaNOAA:



Look familiar? That is either an accurate prediction or one heck of a coincidence. The SanJose Mercury News described what was happening in layman’s terms:

… meteorologists have fixed their attention on the scientific phenomenon they say is to blamefor the emerging drought: a vast zone of high pressure in the atmosphere off the West Coast,nearly four miles high and 2,000 miles long, so stubborn that one researcher [Swain] hasdubbed it the “Ridiculously Resilient Ridge.” Like a brick wall, the mass of high pressure air has been blocking Pacific winter storms fromcoming ashore in California, deflecting them up into Alaska and British Columbia, evendelivering rain and cold weather to the East Coast.

This high pressure ridge is forcing the jet stream along a much more northerly track. Sewalltold me that multiple factors are driving drought in California:

There are, of course, caveats. This is one year, the model studies were looking at averages ofmultiple decades (20 or 50 years). There are other factors besides the Arctic ice that influencestorm tracks; some preliminary work suggests that a strong El Nino overwhelms any influenceof the ice. In El Nino “neutral” times (such as recently), the ice impact can have more of aneffect.



And for this year, it looks like ice may well be having more of an effect. The geopotential heightanomaly looks very much like what the models predicted as sea ice declined. The storm trackresponse also looks very similar with correspondingly similar impacts on precipitation (reducedrainfall in CA, increased precipitation in SE Alaska). While other factors play an influence, the

similarity of these patterns certainly suggests that we shouldn’t discount warming climate anddeclining Arctic sea ice as culprits in the CA drought.

NOAA and Prof. Jennifer Francis of Rutgers have more recently shown that the loss of Arcticice is boosting the chances of extreme US weather.Francis told me this week that “the highly amplified pattern that the jet stream has been insince early December is certainly playing a role in the CA drought.”

…this extremely distorted and persistent jet stream pattern is an excellent example of whatwe expect to occur more frequently as Arctic ice continues to melt.

“The extremely strong ridge over Alaska has been very persistent and has caused recordwarmth and unprecedented winter rains in parts of AK while preventing Pacific storms fromdelivering rain to CA,” she explained. “But is this pattern a result of human -caused climate

change, or more specifically, to rapid Arctic warming and the dramatic losses of sea ice? It’svery difficult to pin any specific weather event on climate change, but this extremelydistorted and persistent jet stream pattern is an excellent example of what we expect tooccur more frequently as Arctic ice continues to melt.” While there is no doubt that climate change is making droughts more intense, the specificconnection the loss of Arctic ice is emerging science, and some, like Trenberth, are skepticalthat the case has been made.Whether or not there is a proven link to the loss of Arctic ice, Senior Weather Channel

meteorologist (and former skeptic) Stu Ostro has been documenting “large magnituderidges in the mid- upper level geopotential height field” lasting as long as many months that“have been conspicuous in the meteorology of extreme weather phenomena.” Ostro gave a talk last year (with Franics), and as Climate Desk summarized, “Ostro’sobservations suggest that global warming is increasing the atmosphere’s thickness, leadingto stronger and more persistent ridges of high pressure, which in turn are a key totemperature, rainfall, and snowfall extremes and topsy- turvy weather patterns like we’ve



think the U.S. will experience increased risk of drought in the coming decades. What hasbeen happening during recent years in the central and western U.S. is very consistent towhat I have been predicting: both the natural variability (IPO [Interdecadal PacificOscillation]) and human-induced climate change will increase the risk of drought over these

regions for the next 1-2 decades. After that, the IPO may switch to a positive phase thatnormally would bring more rain over the U.S. regions, but by that time the human-inducedwarming have over-dominate the natural variability, with the U.S. regions still in drierconditions (compared with the 1980s-1990s).Finally, a 2009 NOAA-led paper warned that, for the Southwest and many semi-arid regionsaround the world, “the climate change that is taking place because of increases in carbondioxide concentration is largely irreversible for 1,000 years after emissions stop.” Impactsthat should be expected if we don’t aggressively slash carbon pollution “are irreversible dry -

season rainfall reductions in several regions comparable to those of th e ‘dust bowl’ era.”

When the climate changes, it ain’t gonna change back.

crown capital management environmental monitoring on how climate change is worsening california

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