Does Global Warming Really Increase Snowfall???

So why did more snow accumulate and glaciers advance during the cold of the Lttle Ice Age??

Trenberth’s 1999 paper framing the effects of global warming on extreme precipitation declared, “With higher average temperatures in winter expected, more precipitation is likely to fall in the form of rain rather than snow, which will increase both soil moisture and run off, as noted by the IPCC (1996) and found in many models.” The  2001 IPCC 3^rd Assessment repeated those expectations stating, “Northern Hemisphere snow cover, permafrost, and sea-ice extent are projected to decrease further.” Soon climate scientists like Dr. Viner proffered alarming scenarios that ‘children would no longer know what snow was’. Similarly in 2008 politicians like RFK Jr. warned DC children would be deprived of the fun of sledding due to global warming. But our climate naturally oscillates and by early February of 2010 Snowmageddon was blanketing the USA’s eastern seaboard with record snows, making global warming predictions the butt of many jokes. The heavy snows didn’t disprove CO2 had caused any warming, but it definitely highlighted failed predictions.

In 2011 Chris Mooney writing for the DeSmog blog noted heavy snowfall had become a “communications nightmare” for global warming theory and urged, “We need to move the public to a place where drawing a warming-snowstorm connection isn’t so challenging”. Kevin Trenberth was already on point. Just two weeks after the 2010 Snowmageddon, Trenberth appeared in a NPR interview flip-flopping to a new climate change framework in which a “Warming Planet Can Mean More Snow”. Now he argued, "The fact that the oceans are warmer now than they were, say, 30 years ago means there's about on average 4 percent more water vapor lurking around over the oceans than there was, say, in the 1970s”. Thus “you can get dumped on with more snow partly as a consequence of global warming," A year later the Union of Concerned Scientists held a press conference asserting global warming was no longer causing less snow, but causing heavier snow. And now, every year as heavy snowstorms approach, Trenberth and his well-groomed media outlets bombard the public, urging them not to be misled by their senses, but trust that cold and snowy days have worsened due to global warming.

Trenberth bases his warmer-earth-more-cold-and-snow alchemy on the Clausius–Clapeyron relation stating, “the water holding capacity of the atmosphere goes up exponentially at a rate of 7% per degree Celsius.” Indeed the Clausius–Clapeyron relation is undeniable physics. The problem is Trenberth misapplies it. First as seen in the graph below from the peer-reviewed paper Weather And Climate Analyses Using Improved Global Water Vapor Observations, there is little evidence of a steady increase in total precipitable water vapor (TPW) ever paralleling rising CO2. The important question Trenberth never asked was, “if TPW has declined since 1998, has there been no warming since 1998?” Indeed in accord with less water vapor, several top climate scientists have reported a global warming hiatus over the same period and the Climate Reference Network reports no warming trend over the USA for the past decade. Furthermore, ocean temperatures were in agreement. Based on Argo data a consensus of scientists reported heat content in the upper 300 meters of the ocean had “increased from 1984 to 1992 followed by a short cooling episode in 1992/93, and then increased from 1994 to 2003/2004, followed by flattening or a decrease.” Note the decline in water vapor from 1992 to 1994 and the decline since 1998 coincides with those ocean temperatures. All things considered, the uptick in heavier snow since 2009 cannot be explained by Trenberth’s new normal “warmer and wetter” assumption.

“Old school” scientists seek to understand causes of extreme events by examining changes in atmospheric circulation and other contributing weather dynamics. In contrast Trenberth does not want scientists to use the standard null hypothesis to test if CO2 warming was a contributing factor. He simply assumes CO2 must be and accuses other researchers of erroneously accepting the standard null hypothesis indicating no effect from rising CO2 (type 2 errors). Based on pure assumptions, he wants to allot some portion of every extreme event to rising CO2, even when an no anthropogenic signal emerges from standard scientific analyses and modeling experiments, as discussed in part 1.  According to Trenberth, due to the dominating effects of natural variability, CO2-driven climate models do a very poor job of simulating large changes in atmospheric circulation. While one model run will force large changes, the next model run will not. To side step that problem, instead of asking if there have been trends in atmospheric and oceanic circulation changes that produced snowfall extremes, Trenberth wants researchers to simply ask, “Was it [snowfall] related to higher than normal SSTs off the coast or farther afield” and then assume those higher temperatures were partly due to rising CO2. But that’s bad science. Higher than normal sea surface temperatures often have no connection to any theoretical CO2 heating. Warmer sea surface temperatures associated with a storm can be solely caused by a redistribution of warm water during an El Nino event. A shift in the North Atlantic Oscillation, or a shift in the jet stream can reduce wind fields and warm sea surfaces because weaker winds ventilate less heat and reduce evaporative cooling. Elsewhere shifts in atmospheric circulation can reduce cloudiness and increase solar heating.

  

Global Water Vapor trend from Vonder Haar 2012 

Trenberth has reported that 70% of the moisture involved in a storm is typically in place at the beginning of the storm, suggesting global warming has increased the available moisture. But again observations do not support Trenberth’s simplistic “warmer and wetter” attributions. For example in the 2011 Groundhog Day Blizzard the amount of available water vapor was far below normal as seen in the diagram posted by meteorologist Joseph D’Aleo at WUWT. So another question Trenberth’s attribution studies must ask, “where does the moisture come from for an extreme snow event when a region is not “warmer and wetter?”

Average Water Vapor During Winter Blizzards of 2011

Still there are many useful questions that can be asked to determine if the affects of climate change have exceeded the boundaries of natural variability. For example, do similar extreme snowfalls happen independently of sea surface temperatures that are warmer or cooler than normal? That question is easily answered from a historical perspective that encompasses just 100 to 150 years.  Historical extremes like the Great Blizzard of 1888 dropped very similar amounts of snow on America’s northeast, despite a very different climate background with colder ocean temperatures from the Little Ice Age and extensive Arctic sea ice. Comparing the Great Blizzard of 1888 with Snowmaggedon, higher than normal SST temperatures do not appear to be a critical factor.

To separate natural weather dynamics from climate change scientists must also establish why snowfall varies greatly over small timeframes; timeframes that are too short for CO2 to hypothetically alter ocean temperatures. As anyone having lived in New England knows, during any given winter the depth of snowfall is totally dependent on 2 crucial factors: 1) how fast the storm moves along the coast and 2) how far from the coast the storm travels. Unquestionably slow moving storms cause the most extreme precipitation events, rain or snow. For the American east coast, colder than normal temperatures south of Greenland encourage more frequent blocking ridges of high pressure, and those blocks cause storms to slow down and even stall. These “Greenland blocks” were also responsible for Superstorm Sandy’s sudden shift back towards the coast.

Greenland blocks are more common during negative phases of the North Atlantic Oscillation (NAO), a phase that has coincided with the recent rise in heavy snowstorms. So we must also ask if global warming has affected a shift to the negative phase of the North Atlantic Oscillation (NAO)? But previous research had suggested increased CO2 promoted a more positive NAO during the latter decades of the 20^th century. Within a framework of a single year or a few decades, shifts in the NAO are often associated changes in snowfall. But if we ask if climate change altered trends in a given NAO phase, researchers report in the paper Need for Caution in Interpreting Extreme Weather Statistics, “no significant changes either in the mean or in the entire PDFs [Probability Density Functions]” of the NAO index over the last 140 years.

As illustrated in the diagram below, the positions of cold air masses on land and warm air masses over the ocean determine where precipitation falls as snow or rain. For example during the Blizzard of 2013, despite being surrounded by warm ocean waters Nantucket Island received the least amount of snowfall (6.3 inches) while further west Providence Rhode Island (18 inches) and Hartford, Connecticut (22.8 inches) surrounded by a colder air mass received record snow. For snow to form, moist warm air must be raised to an altitude where temperatures are below freezing, with an optimal snow forming temperature hovering around -12 degrees C  (10F). Typically a cold air mass (or mountains) forces the rise in altitude. According to the Clausius-Clapeyron relation, air at 31 degree F can only hold a given amount of moisture, no matter how greatly the global average temperature varies. The critical factor that determines how much snow will accumulate is the temperature of the air nearer the ground. If lower air layers are warmer than 0°C (32F), the snow will melt as it falls forming rain, freezing rain or sleet. Only where the entire air column is below freezing do we get snow. If the storm track moves too far out to sea, or if the cold air mass is to far inland, the warm air mass gets less lift, and much less snow forms. Thus to attribute the cause of extreme snowfall a scientist must also ask, “what was the position of the storm track?” And how much cold air was in place?

Trenberth cavalierly suggests that it’s always cold enough to snow in winter, but that that is misleading. For blizzards to occur sufficient cold air must already be in place and that is not a given. Dips in the jet stream and storm tracks across North America pull cold Arctic air southward along the storms trailing edge. To produce Snowmageddon blizzards along the east coast, enough cold air had to reach the southeast and overflow the Appalachian barrier where it is dammed up along the coast (Rauber 2005). The snows that reached Jacksonville Florida in 2015 were the result of a stronger than normal flow of cold air over the Appalachians. Similar to “lake effect snow”, after flowing over the ocean, the cold dry air picked up enough moisture to dust Jacksonville with light snows.

Accordingly the National Snow and Ice Data Center experts tell us, “While it can be too warm to snow, it cannot be too cold to snow. Snow can occur even at incredibly low temperatures as long as there is some source of moisture and some way to lift or cool the air”.  In contrast, Mooney relays Trenberth’s message contradicting those experts stating, “Heavy snows mean the temperature is just below freezing, any cooler and the amount would be a lot less.”… “Warmer waters off the coast help elevate winter temperatures and contribute to the greater snow amounts. This is how global warming plays a role.”   Why would Trenberth make that up?

Dips in the jet stream and stronger storms capable of pulling an abundance of cold Arctic air equatorward are often associated with the negative phase of the North Atlantic/Arctic Oscillation (AO). Although December 2015 had been mild, when weather forecasters recognized a shift to the AO’s negative phase in early January 2016, they correctly predicted conditions would be just right for the Blizzard of 2016 that buried the mid-Atlantic States in 2 feet of snow 2 weeks later. So to explain contributions of extreme snowfall, scientists must ask how do natural cycles of the North Atlantic/Arctic Oscillation contribute to extremes.

How Air Temperature Determines Snowfall or Winter Rain

As would be predicted by a shift to more frequent negative phases of the NAO/AO, the USA was experiencing greater incursions of cold Arctic air that promoted both more record low temperatures and greater snowfall, as was the case in the 1960s and 70s. Despite projections by CO2 driven models that the ratio of record high temperatures would exceed record low temperatures by 20 to 1 in 2050, in 2013 and 2014 record low temperatures exceeded record highs. However to counter such contradictory observations, Trenberth pushes another unscientific and non-falsifiable explanation. Suggesting risingCO2 was preventing extreme cold that he claims reduce snowfall, Trenberth submitted,

“below normal temperatures can be fully consistent with climate change but are likely warmer than they otherwise would have been.”

Winter storms are low-pressure systems, or cyclones, that spin in a counter-clockwise direction as they travel across North America. Most winter cyclones in North America are initiated by the curvature of the jet stream as it passes around the Rocky Mountains, or curve northward along the eastern seaboard. The North American topography favors two major storm centers in western North America. One lies just east of the Canadian Rockies where “Alberta Clippers” form. Clippers are fasting moving storms. Typically they will not produce record heavy snowfall because the moisture supply flowing into northern North America is relatively low and the Clippers’ swift passage does not allow for sustained snow accumulation. However Clippers can evolve into major storms over the Great Lakes or eastern seaboard where moisture is available or when they align with storms initiated by the subtropical jet stream. The other storm center lies just east of Colorado. These storms often gather more moisture from the Gulf of Mexico and are slower moving. Typically these storms deliver heavier snowfall.  Of importance to east coast snowfall, either storm type will pull cold Arctic air southward and eastward toward the coast, setting the stage for greater snowfall totals from the next storm. In fact it was an Alberta Clipper that set the stage for the east coast Blizzard of 2015.

In general as illustrated below, there are 3 air masses that interact with a winter storm. 1) The cooler air that was left in place from a previous storm. This cooler air mass forces the approaching warm air to rise to altitudes where water vapor can turn to snow. 2) Warm moist air from the Gulf of Mexico or tropical Atlantic that is pulled northward by the storm’s leading edge. 3) The cold dry Arctic air pulled southward along the storms trailing edge. Mild warm conditions generated from the warm air mass typically precede a blizzard, and often catch people ill prepared for the bitter cold that follows. The most famous incident was the January 1888 School Children’s Blizzard that swept through the Great Plains. It was so named because of the 235 people who were killed, many were children who headed to school “lightly dressed because temperatures had been gradually rising to just above freezing as warm moist air was pulled up from the Gulf of Mexico. However within a few hours temperatures dropped to -29 degrees C, as the cold Arctic air advanced. Due to this counter-clockwise circulation pattern, strong storms can reverse a region’s normal latitudinal temperature gradient, temporarily making it warmer in the north and colder in the south.

How Air Masses Interact in Winter Storms

When storms track along the east coast, they intensify due to the sharp contrast between warm Atlantic temperatures and cold land temperatures. The sharp contrast favors “explosive cyclogenesis”, a phenomenon that is most common along the Gulf Stream and along the Kuroshio Current and promotes extreme snowfalls in New England and Japan respectively. In addition to the land-sea contrast, there is also a steep temperature gradient over the Atlantic due to the warm Gulf Stream. Along the coast of North Carolina in February, coastal waters are typically 10 degrees C (50 F), while just 130 kilometers to the east, Gulf Stream waters register 22 degrees C (72 F) Reddy 1994. In addition to the heat and moisture evaporating from warm Gulf Stream waters, winter storms travelling up the coast will pull warm moist tropical air northward in what is called the “warm conveyor” as illustrated below in the Washington Post illustration of the 2015 blizzard. Notice the head of the storm’s “comma” shape is an area of extreme snowfall, where the storm had pulled warm and moist air northward and westward which then rose over the colder air already in place from previous storms.

How WInter Storms Convey Warm Air and Moisture Northward

Nevertheless ignoring all the potent weather dynamics that naturally drive anomalously warmer sea surface temperatures ahead of a storm, Trenberth emailed his favorite media outlets Joe Romm, Chris Mooney and others to assert, “At present sea surface temperatures are more the 2 degrees F above normal over huge expanses (1000 miles) off the east coast and water vapor in the atmosphere is about 10% higher as a result. About half of this can be attributed to climate change.”

Was this 50% contribution ever scientifically tested and peer reviewed? Did Trenberth determine “how much warmth was transported northward on the warm conveyor side of the storm?” Did Trenberth ask how much warmth was picked up from the Gulf Stream and carried westward to cooler coastal waters? Did the storm temporarily reverse the latitudinal temperature gradient? Trenberth’s untested opinion of a 50% contribution attributed to rising CO2 was simply an opinion. It was an opinion pushed to satisfy the “need to move the public to a place where drawing a warming-snowstorm connection isn’t so challenging” and thus protect the global warming theory.

More yellow journalism followed a few weeks later in Mooney’s “What the massive snowfall in Boston tells us about global warming”. Keeping the focus on global warming Mooney reported, “sea surface temperatures off the coast of New England are flashing red”. Michael Mann added to the global warming meme reporting, “Sea surface temperatures off the coast of New England right now are at record levels, 11.5C (21F) warmer than normal in some locations.” But Mooney, Mann and Trenberth were not interested in discussing the details of those fleeting warm anomalies. They never considered the warm conveyor delivered above normal warmth northwards and then dragged that warmth and Gulf Stream warmth westward. They never tell us how fleeting those warm anomalies were. Yet for the month of February 2015 temperatures on land and sea were all several degrees colder than normal as seen in the illustration by CBSBoston’s chief meteorologist. It was extreme cold that intensified the storm. And despite below normal sea surface temperatures and thus below normal water vapor, the storm gathered enough moisture and Boston experienced record-breaking snows.

Temperaturs Were Far Below Normal During Blizzards of 2015

Trenberth has now revised his 1999 framework. Despite the record cold that reduces water vapor, he still argues global warming causes more snow in winter. He maintains warming will still cause more rain and reduced snow in the fall and spring. But again the evidence contradicts his claims. Although Trenberth focuses public attention on a decreasing trend in spring snow extent, like the winter, there has also been an increasing trend in autumn snow extent as seen in the graph below from Rutgers Global Snow Lab.

Trend in Autmn Snow Extent for Northern Hemisp
here from Rutgers Global Snowlab

So why does Trenberth persist in claiming extreme snowfalls are due to a warmer and wetter world. Trenberth betrays his intentions when he writes,  “The main way climate change is perceived is through changes in extremes because those are outside the bounds of previous weather. Climate change from human influences is difficult to perceive and detect because natural weather-related variability is large. Even with a significant climate change, most of the time, the weather is within previous bounds.” So Trenberth has organized a media campaign to not only overturn the null hypothesis, but to reverse our understanding of the difference between climate and weather. He wants you believe every extreme weather event is worsened by CO2, whether or not there is any evidence.

The Kevin Trenberth Effect: Pulling Science Back to the Dark Ages - Part 1 Droughts and Heat waves

In my essay on the natural causes of Pacifica’s Coastal Erosion, I reported on how California’s coast has still not reached an equilibrium with sea levels that rose at the end of the last ice age. I also suggested the media and a few scientists give the public a false impression that all natural weather phenomenon and coastal erosion have been worsened by CO2-driven climate change. Pointing to a few leading perpetrators I wrote, “After centuries of scientific progress, Trenberth and his ilk have devolved climate science to the pre-Copernican days so that humans are once again at the center of the universe, and our carbon sins are responsible for every problem caused by an ever-changing natural world.” Such a strong statement deserves further elaboration. Although a highly intelligent scientist, to support his obsessive claims that CO2-caused climate change has worsened every extreme event, Trenberth has been tragically undermining the very foundations of scientific inquiry by 1) reversing the proper null hypothesis, 2) promoting methods that can not be falsified, 3) promoting fallacious arguments only by authority, and 4) stifling any debate that promotes alternative explanations.

Dr. Trenberth, via his well-groomed media conduits, preaches to the public that every extreme event - flood or drought, heat wave or snowstorm - is worsened by rising CO2. To fully appreciate the pitfalls of his “warmer and wetter” meme, you need to look no further than Trenberth’s pronouncements regards the devastating Moore, Oklahoma tornado. Although Trenberth admits, “climate change from human influences is difficult to perceive and detect because natural weather-related variability is large”, in a Scientific American interview, arguing only from authority he cavalierly attributed CO2 climate change to a “5 to 10 percent effect in terms of the instability and subsequent rainfall, but it translates into up to a 33 percent effect in terms of damage.” But in contrast to Trenberth’s “warmer and wetter world” assertions, there was no warming contribution. Maximum temperatures in Oklahoma had been cooler since the 1940s.

Clearly Trenberth’s simplistic “warmer and wetter” world assertion cannot be applied willy-nilly to every region. Climate change is not globally homogenous. It is regionally variable and the global average temperature is a chimera of that regional variability. Furthermore his claim of a “wetter world” is a hypothetical argument not supported by evidence. As seen in the graph below from the peer-reviewed paper Weather And Climate Analyses Using Improved Global Water Vapor Observations, there is little evidence of a steady increase in water vapor paralleling rising CO2. Even Trenberth’s own studies have concluded, “Total Precipitable Water vapor [TPW] variability for 1988–2001 was dominated by the evolution of ENSO [El Ninos].” The El Nino effect is evidenced by peak water vapor coinciding with the 1998 El Nino. Since 1998, the atmosphere has been arguably drier, contradicting his CO2 driven wetter world hypothesis. Despite a multitude of contradictions, to garner support for his theories Trenberth insists on reframing the scientific method by reversing the null hypothesis. Instead of determining if CO2 had an effect on extreme weather beyond what natural variability predicts, Trenberth wants scientists and the public to blindly assume, “All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be.”

Trend in Total Precipitable Water (TPW) Contradicts Trenbert's Assertions

In contrast to simply making the “Trenberth assumptions”, climate scientists use two main strategies to extract any possible CO2 effect. First based on physics, the consensus believes early changes in CO2 concentration exerted no significant climate impact, and extreme events happening before 1950 were due to natural variability. Thus historical analyses compare extreme events before and after 1950 to determine how they differ. But Trenberth has been maneuvering to make such CO2 attribution studies non-falsifiable by stripping recent extreme weather events from that historical framework. In the Washington Post, Chris Mooney pushes Trenberth’s “new normal” quoting,

“All storms, without exception, are different. Even if most of them look just like the ones we used to have, they are not the same.”

Trenberth’s “new normal” side steps historical scientific analyses. One would think a good investigative reporter would question Trenberth’s undermining of that scientific methodology, but Mooney is not a scientist. Ironically Mooney’s claim to fame was a book “The Republican War On Science”, about which Washington Post’s Keay Davidson wrote, "Mooney is like a judge who interprets a law one way to convict his enemies and another way to acquit his friends.” Evidently that is just the kind of journalist Trenberth and the Washington Post wanted. Mooney left Mother Jones and was hired by Washington Post to write columns on climate change and serves as one of Trenberth’s media conduits. (Btw: the Real Science website is a great place to view headlines from the past illustrating great similarities between past and present extreme weather events.)

The second strategy relies on models that compare “the probability of an observed weather event in the real world with that of the ‘same’ event in a hypothetical world without global warming.”  But this approach incorrectly assumes the natural variability is well modeled. Often the model’s “world without global warming” is assumed to be stationary but with a lot of “noise”. But that tactic generates false probabilities because our natural climate is not stationary but oscillating. In 2012 climate experts met at Oxford University to discuss such attribution studies and the highlights were reported in Nature. Many experts suggested that due to “the current state of modeling any attribution would be unreliable, and perhaps impossible…One critic argued that, given the insufficient observational data and the coarse and mathematically far-from-perfect climate models used to generate attribution claims, they [attribution claims] are unjustifiably speculative, basically unverifiable and better not made at all. And even if event attribution were reliable, another speaker added, the notion that it is useful for any section of society is unproven.”

(Such concerns raise another question: if attributing a CO2 effect on any event like a heat wave or drought is nearly impossible, how reliable is any attribution of a global average temperature if those same extreme heat waves and droughts skew the global average?)

Color me an old-fashioned scientist, but our best practices demand we correctly establish the boundaries of natural climate change before we can ever assume rising CO2 has worsened weather events. But Trenberth and his ilk insist on reversing the null hypothesis. Instead of asking if a weather event exceeded natural variability, Trenberth insists we rashly assume CO2 has already worsened the weather. However most scientists share my concern about his maneuverings. As Professor Myles Allen from Oxford University said,  “I doubt Trenberth’s suggestion [reversing the null hypothesis] will find much support in the scientific community.”  Trenberth’s attempt to reverse the null hypothesis has been discussed previously by Dr. Judith Curry and by top rated skeptic blogs, and in a published paper by Dr. Allen “In Defense of the Traditional Null Hypothesis.

Nonetheless many papers are now being published that simply make Trenberth’s assumptions and there is a growing rift between researchers who adopt Trenberth’s “new normal” tactics versus “old school” scientists. The different resulting scientific interpretations are well illustrated in peer-reviewed publications on droughts and heat waves.

A bank account serves as a good analogy to illustrate drought stress.  Financial (hydrologic) stress results from changes in income (rain and snow) versus withdrawals (evaporation and runoff) and the buffering capacity of your reserves (lakes, wetlands and subsurface water). Old school science would demand researchers eliminate all confounding factors affecting hydrological stress before claiming any effect by a single variable like CO2. Here are a few confounding factors that are seldom addressed in papers that blame a greenhouse effect for higher temperatures and stronger heat waves and droughts.

i.)             Clear dry skies increase shortwave (solar) insolation, while simultaneously decreasing downward long wave radiation (i.e. decreasing the greenhouse effect). Reasons for this were discussed in an essay Natural Heat Waves and have been verified by satellite data (Yin 2014). Higher temperatures happen despite a reduced greenhouse effect.

ii.)             In arid and semi-arid regions like the American Southwest, precipitation shortfalls not only decrease the hydrologic “income” but also decrease evaporation. If there is no rain, there is nothing to evaporate. The decrease in evaporative cooling raises temperatures (Roderick 2009, Yin 2014) . Drier surfaces have a lower heat capacity so that incoming energy that was once converted to latent heat of evaporation is now felt as sensible heat that rapidly raises temperatures. Trenberth’s global warming claims often have the tail wagging the dog by assuming higher temperatures cause drier soils. Drier soils cause higher temperatures.

iii.)           Natural cycles cause decadal oscillations between dry and wet years. Recent research (Johnstone 2014) report the past 110 years of climate change in northwestern North America can be fully accounted for by the multi-decadal Pacific Decadal Oscillation (PDO).  The PDO alters the pattern of sea surface temperatures, which alters atmospheric circulation affecting transportation of warmth from the south, and moisture from the ocean. The PDO produces dry cycles that not only reduce rainfall but can increase temperatures via mechanisms i and ii. The negative PDO experienced over the last 15 years promoted more La Ninas that make California drier.

iv.)            The buffering effect of hydrologic reserves has increasingly dwindled. Wetlands have been drained and degraded watersheds have drained subsurface waters resulting in reduced evapotranspiration. The loss of California wetlands since 1820 has been dramatic (Figure 9) generating a decreasing trend in evaporative cooling. Furthermore spreading urbanization has relegated natural streams to underground pipelines. Urbanization has increased runoff (hydrologic withdrawals) as rainfall is increasingly shunted into sewer systems and no longer recharges whatever remaining landscapes are not paved over with heat retaining materials. This increasing reduction in our moisture “reserves” increases regional dryness and has not been balanced by irrigation.

California's Lost Wetlands Has Reduced Evaporative Cooling

The difference between “old school” science and Trenberth’s “new normal” is illustrated in contrasting interpretations of recent extreme droughts and heat waves. For example NOAA’s Randall Dole attributed the 2010 Russian heat wave to a lack of precipitation and a high-pressure blocking pattern that enhanced surface feedbacks. Dole had been studying the effects of blocking patterns for over 30 years since his research days at Harvard. Blocking high-pressure systems pump warm air northward on the systems western flank and trap that heat while clear skies increase insolation. In 1982 Dole had mapped out 3 regions most prone to blocking highs due to undulations of the jet stream.  Those same blocking highs are also implicated in our more recent heat waves that “Trenberth’s school of climate change” trumpet as worsened by CO2. The 3 regions are 1.) Northeast Pacific where the “Ridiculous Resilient Ridge” typically produces California’s drought, 2) North Atlantic that affects Western Europe’s droughts and 3) over northern Russia generating heat waves every 20 years such as the 2010 heat wave. 

Dole concluded in 2011 “the intense 2010 Russian heat wave was mainly due to natural internal atmospheric variability.” Dole’s historical analysis noted, “The July surface temperatures for the region impacted by the 2010 Russian heat wave show no significant warming trend over the prior 130-year period from 1880 to 2009” and he noted similar but slightly less extreme heat waves had occurred periodically over the past 130-year period. The more extreme temperatures could be attributed to “surface feedbacks” from the early season drought and landscape changes. Based on a proper null hypothesis Dole concluded, “For this region an anthropogenic climate change signal has yet to emerge above the natural background variability.”  

Whether or not Dole is correct, Dole is a climate scientist we can trust. A trustworthy scientist, who cannot detect a difference between a recent extreme event and natural extreme events from the past, will simply report that they cannot detect an anthropogenic signal. Whether or not there was a CO2 global warming effect remains to be tested. In contrast less trustworthy scientists will push a non-falsifiable CO2 effect and argue natural variability “masked CO2 warming,” a warming Trenberth insists we must assumes to be present.

Trenberth also appears to hate any scientific claim that weather was just weather. Accordingly he attacked Dole’s “heresy” via his internet attack dogs. Joe Romm blogged, “Monster Crop-Destroying Russian Heat Wave To Be Once-In-A-Decade Event By 2060s (Or Sooner)”, which provided Trenberth an opportunity to denigrate Dole’s analysis in a way not allowed in more staid scientific journals. Trenberth maligned Dole’s analysis as “superficial and does not come close to answering the question in an appropriate manner. Many statements are not justified and are actually irresponsible. The question itself is ill posed because we never expect to predict such a specific event under any circumstances, but with climate change, the odds of certain kinds of events do change.”  

Seriously? Dole’s research was irresponsible because it found no CO2 effect?!? The great value of science to society is that it provides us with some measure of predictability that guides how we best adapt to future events. Dole simply asked, “Was There a Basis for Anticipating the 2010 Russian Heat Wave?” and concluded neither past weather patterns, current temperatures trends, historical precipitation trends or increasing CO2 could have prepared Russia for that event. The only predictability was that similar events had happened every 2 or 3 decades. Trenberth has persistently argued the only “right question” to ask is “how much has CO2 worsened an extreme event, but Dole asked a more useful question. What triggers extreme Russian droughts and heat waves every 20 to 30 years?

Dole’s models, forced with sea ice or ocean temperatures, did not simulate the observed blocking patterns over Russia. Based on several modeling experiments Dole concluded results were “consistent with the interpretation that the Russian heat wave was primarily caused by internal atmospheric dynamical processes rather than observed ocean or sea ice states or greenhouse gas concentrations.” Yet despite Dole’s examination of a great breadth of contributing factors, Trenberth attacked Dole for being “too narrowly focused” because, of all things, Dole did not include July flooding in China and India, or record breaking floods in Pakistan in August. Trenberth was suggesting that that those floods were due to warmer oceans and thus global warming should have been blamed for worsening the Russian heat wave even though Dole’s modeling studies found no such connection.

But Trenberth had the tail wagging the dog - again! Due to the clockwise motion of a blocking High, warm air was pulled poleward and accumulated on the western side of the system driving the heat wave. In contrast the same system pushed colder air equatorward along the system’s leading eastern edge. As discussed in Hong 2011, when that cold air was pumped southward, it collided with warm moist air of the monsoons, and it was that cold air that increased the condensation that promoted extreme precipitation in some locales. Nonetheless, determined to connect CO2 warming to the Russian heat wave, it was Trenberth who was not asking the right questions. He should have been asking how much did a naturally occurring blocking pattern contribute to the southern Asian floods.

As was the case for the Russian heat wave, analyses of the historic heat wave for Texas and the Great Plains revealed no warming trend over the latter 20^th and the 21^st century. In Hoerling 2013, a team comprised of ten climate experts, mostly from NOAA, examined the Texas drought and heat wave. They reported “no systematic changes in the annual and warm season mean daily temperature have been detected over the Great Plains and Texas over the 62-yr period from 1948 to 2009 consistent with the notion of a regional ‘‘warming hole’’. Indeed, May–October maximum temperatures over the region have decreased by 0.9°C.” Thus those experts concluded the absence of observed warming since 1948 cautioned against attributing the heat wave and drought to any warming, natural or CO2 related (However CMIP5 modeled results suggested a 0.6°C warming effect since 1900). Likewise satellite data revealed a radiative signature of a reduced greenhouse effect and increased solar heating (Yin 2014).  

In contrast Trenberth claimed on Romm’s blog, “Human climate change adds about a 1 percent to 2 percent effect every day in terms of more energy. So after a month or two this mounts up and helps dry things out. At that point all the heat goes into raising temperatures. So it mounts up to a point that once again records get broken. The extent of the extremes would not have occurred without human climate change.” But Trenberth’s 1% per day CO2 attribution seems absurd in a regions where maximum temperatures had decreased. His warmer and wetter world meme only obfuscated the issues and Trenberth was again asking the wrong question. The correct question was how much had the drought lowered surface moisture and reduced evaporative cooling that caused higher temperatures? In a region where there had been no increase in maximum temperatures, the amplified temperatures for this extreme weather event were likely the result of natural surface feedbacks caused by a lack of rain.

NOAA’s drought task force also reported on the following Great Plains drought and heat waves. They concluded this drought was likewise due to natural variability stating, “Climate simulations and empirical analysis suggest that neither the effects of ocean surface temperatures nor changes in greenhouse gas concentrations produced a substantial summertime dry signal.” But no matter the level of expertise, Trenberth via his internet attack dog Joe Romm and his blog assailed the Drought Task Force with a less than an honest account. Trenberth assaulted their conclusions, “It fails completely to say anything about the observed soil moisture conditions, snow cover, and snow pack during the winter prior to the event in spite of the fact that snow pack was at record low levels in the winter and spring.”  (But Trenberth’s denigration contrasted with a document-search for the term “soil moisture”, which found it was mentioned about 15 times including the sub-section title in big bold letters “Simulations of Precipitation and Soil Moisture”.) Trenberth’s mugging continued, “There is no discussion of evaporation, or potential evapotranspiration, which is greatly enhanced by increased heat-trapping greenhouse gases. In fact, given prevailing anticyclonic conditions, the expectation is for drought that is exacerbated by global warming, greatly increasing the heat waves and wild fire risk. The omission of any such considerations is a MAJOR failure of this publication.”

But that was a very odd comment for a top climate scientist! Anticyclonic conditions predict droughts will be exacerbated by natural feedbacks, not by global warming.

And again Trenberth failed to ask the right questions. If he believed a greenhouse effect exacerbated the drought by increasing evaporation, then he needed to ask why satellite data has been showing reduced downward long wave radiation and increased solar insolation that typically occur in dry clear skies? In contrast to Trenberth’s obfuscations, the Task Force had extensively discussed the meteorological conditions that inhibited the transport of moisture from the Gulf of Mexico, resulting in reduced soil moisture. Despite low snowpack, soil moisture had not been deficient in the spring. It was the lack of moisture transported from the Gulf that reduced summer soil moisture that raised temperatures and exacerbated the drought. Furthermore modeling experiments performed by the Task Force found precipitation was not affected by changes in sea surface temperatures or greenhouses gases. And historical analyses (as seen in Figure 7) revealed that despite global warming Central USA temperatures were lower than expected given the extreme dryness and expected surface feedbacks. So again Trenberth failed to ask the right questions. Why were temperatures higher during the droughts of the 30s when there was no increased greenhouse effect?

The 2011-2015 drought in California is the most flagrant example of the Trenberth Effect. California’s droughts are most often associated with natural La Nina conditions and a blocking ridge of high pressure that inhibits the flow of moisture from the Pacific to California. Another thorough analysis by NOAA’s Drought Task force again concluded, “the recent drought was dominated by natural variability.” In an interview with the NY Times co-author Dr. Hoerling stated, “It is quite clear that the scientific evidence does not support an argument that this current California drought is appreciably, if at all, linked to human-induced climate change.”

In support of the Drought Task Force’s conclusions, every study of the California drought has reported the major factor driving recent drought has been episodic rainfall deficits. Nonetheless despite the extreme rainfall shortfall there was no evidence of any trend in precipitation amounts or variability that could explain the recent lack of precipitation. Ridging patterns have always reduced rainfall, and the lack of a trend in precipitation contradicts recent claims that greenhouse gases are increasing the likelihood of a ridging pattern that was blocking precipitation (Swain 2014). Nonetheless media conduits for alarmism like Slandering Sou promoted Swain’s arguments. But Slandering Sou is not a scientist nor has she ever published any meaningful science. In contrast climate scientists like Dr. Cliff Mass readily pointed out Swain’s faulty analyses.

Furthermore there is no long-term precipitation trend as seen in the 700-year California Blue Oak study by Griffin 2015. The dashed blue line represents the extreme precipitation anomaly of 2014. For the past 700 years similar extreme precipitation shortfalls have equaled or exceeded 2014 several times every century. From a historical perspective, we can infer there is no evidence that rising CO2 has increased that ridging pattern that reduces rainfall and causes drought. More severe and enduring droughts happened during the Little Ice Age when temperatures were cooler. Clearly land managers and government agencies should prepare for severe periodic droughts whether or not CO2 has any effect or not, testifying to why the Oxford attendees saw little usefulness in CO2 attribution studies.

No Trend in California Precipitation

As expected Trenberth’s attack dogs assailed NOAA’s California report because it attributed drought to natural variability. Romm blogged that the drought would Soon Be More Dire. Over at the Washington Post, Mooney’s fellow yellow journalist Darryl Fears wrote “California’s terrifying climate forecast: It could face droughts nearly every year.” But Fears’ projection has already failed. Despite no precipitation trends, several authors blamed the California drought on extremely high temperatures. Michael Mann argued “Don’t Blame It on the Rain”. Blame it on global warming. To support warming assertions Trenberth blogged a fanciful analogy, “The extra heat from the increase in heat trapping gases in the atmosphere over six months is equivalent to running a small microwave oven at full power for about half an hour over every square foot of the land under the drought.” If that wasn’t fearful enough Trenberth added, “No wonder wild fires have increased!”

But historical analyses suggest the universe had unplugged Trenberth’s “microwaves” over most of California since 1940s, and wildfires were much worse during the Little Ice Age. As shown in the illustration below from Rapacciuolo 2014, observations show most of California, like Texas, had experienced a decline in the maximum temperatures since 1940. If maximum temperatures have not risen there has been no accumulation of heat and California appears to be insensitive to rising CO2. The question that Trenberth failed to ask is why did maximum temperatures decline in his “warmer and wetter” world?

70-year Cooling Trend for Maximum Temperatures in Half of California 

Mao 2012 analyzed the drought in California’s Sierra Nevada and likewise found no trend in maximum temperatures. However assuming the minimum temperature trend was an expression of anthropogenic warming, he used the minimum trend to model CO2-warming effects on drought. But minimum temperatures have little effect on drought. Relative humidity is highest and approaches the dew point during the minimum. Due to daytime surface-heating, turbulent convection peaks around the maximum temperatures and increases evaporation and dries the soil dramatically. But turbulent convection is virtually non-existent when minimum temperatures are measured. Accordingly based on the minimum temperature trend, Mao 2012 found “warming may have slightly exacerbated some extreme events (including the 2013–2014 drought and the 1976–1977 drought of record), but the effect is modest; instead, these drought events are mainly the result of variability in precipitation.”

That brings us to the most recent example of how Trenberth’s “new normal” has undermined science. Williams 2015 claimed CO2 warming had worsened the California drought by 8 to 27%, a claim that was trumpeted by press releases and blogs. To his credit Williams did use a much better version of the Palmer Drought Severity Index (PDSI) that takes into account the physical processes causing a drought. He also pointed out that simpler versions of the PDSI, used by Diffenbaugh 2015, Griffin 2014 and others, had artificially amplified and overestimated the contribution of temperatures to drought (Sheffield 2012, Roderick 2009).

However Williams claimed to have separated anthropogenic warming from natural warming, and used the reversed null hypothesis to do so. Williams warned that he had assumed any warming trend was all anthropogenic. To determine natural temperature variability he simply subtracted his hypothetical anthropogenic-warming trend from California’s observed temperatures. Whatever remained was deemed natural variability. By assuming CO2 is responsible for any warming trend, alleviates climate scientists from the more arduous task of determining natural temperature variability. Furthermore instead of separating out the confounding factors that are known to contribute to higher temperatures, such as the PDO (Johnstone 2014) or landscape feedbacks (as discussed above), Williams simply acknowledged he did not account for those factors as a caveat, then went on to promote his human influence estimated in press releases suggesting he had scientifically linked CO2 warming to drought severity. Without accounting for all factors, Williams’s study was not a scientific evaluation, but simply an opinion piece. Still, as might be expected, Trenberth weighed in calling Williams analyses reasonable but conservative, and recommended that he drop the lower end (8%) of estimated human contribution.

But Williams and Trenberth never asked the right questions. How can scientists assume an anthropogenic warming trend if it hijacks the earlier warming trend before 1950, a trend that the consensus believes was all natural? How can scientists assume an anthropogenic warming trend when there no warming trend for maximum temperatures since 1950? How can scientists blame global warming for worsening droughts when other factors like the PDO, the drying of the California landscape and surface feed backs were never accounted for? 

And more importantly, why should people ever trust Trenberth’s “new normal” science that undermines the very foundation of scientific inquiry. It is more than irksome that my taxes help pay Trenberth’s high salary and allow him to undermine the foundations of scientific inquiry.

In part two: Trenberth’s snowjob, I examine Trenberth’s fallacious argument that global warming causes more snow.