March 30, 2021
Jim Steele examines natural climate change, species extinctions, species range changes, environmental stewardship.
March 30, 2021
The earth’s energy equilibrium is determined by the balance between incoming solar radiation versus radiative cooling that emits infrared radiation back to space. Water vapor primarily and CO2 can slow radiative cooling via the greenhouse effect. I am most grateful for the greenhouse effect. Without it the earth’s average temperature would hover near 0°F instead of our currently more livable 59°F. But in addition to any radiative effects, the earth’s global average temperature is determined by a variety of climate dynamics, such as the balance between ocean heat storage and heat ventilation. This is well established as climate scientists attributed the slowdown in 21st century global warming was due to increased ocean heat storage associated with a period of more La Ninas. Warming in the northeast Pacific Ocean, famously known as the blob, was not caused by added heat, but by reduced winds that ventilated less heat than normal. Cloud dynamics are also important. Clouds can warm the nights and cool the days. Although increased cloud cover can slow the loss of outward-bound infrared radiation, clouds also block sunlight to cause more cooling. Modeling studies have shown cloud cover trends are more closely related to decadal variability, and dynamics such as the Pacific Decadal Oscillation, than to any greenhouse gas induced warming.
Changes in land surface conditions are another critical dynamic. For example, given the exact same amount of incoming heat, dry soils will increase surface temperatures twice as fast as moist soils. As expanding human populations drained wetlands, and increasingly shunted rainwater into storm sewers, drier soils have caused abnormally higher temperatures during normally occurring droughts and heat waves. Unfortunately a myopic focus on CO2 has led to downplaying the vital importance of how climate dynamics affect the global average temperature. But climate dynamics not only offer the best explanation for regional weather extremes, climate dynamics alone can account for 150 years of the earth’s average warming.
Consider that the polar regions are much warmer today than what the physics of radiative heating and cooling would predict. Polar regions should be much, much colder than they are today because they radiate more heat back to space than is absorbed by the sun and the greenhouse effect combined. The dynamic transport of heat from the tropics via ocean and air currents provides the added Arctic “warmth” that’s observed today. While winter temperatures (January) at north pole vary from -45°F to -15°F, the south pole winter temperatures vary between -80°F and -67°F. The south pole is so much colder because it is relatively shielded from the warming dynamics of ocean heat transport as well as its higher elevation.
Scientists have noted the warming effects of warm ocean currents travelling poleward to the Arctic for over 100 years. Winds extract heat from the warm poleward bound Gulf Stream and North Atlantic Current and carry that heat across the Atlantic to increase northwest Europe’s temperatures by 9-18°F. Thus it is the strength of those winds which is moderated by the North Atlantic Oscillation, and the volume of heat carried by the ocean currents that are the dynamics determining changes in the average European temperature.
With comprehensive modern measurements, researchers now estimate that inflows of warm Atlantic water “carry enough heat, if released, to melt the Arctic sea ice many times over”. However, when that warm Atlantic water reaches the Arctic Ocean, most sinks below 300-foot depths due to its greater density caused by its higher saltiness. The dynamics of an overlying layer of fresh water and the thickness of insulating sea ice determine how much of that intruding Atlantic heat radiates back to space. Between 1950 and 1990, air temperatures exhibited a cooling trend over the western Arctic Ocean where insulating sea ice remained intact and inhibited the ventilation of stored heat. The lack of warming suggested no greenhouse effect.
Recent wind-driven increases in the volume of intruding Atlantic water (as well as intruding Pacific water) have melted more Arctic sea ice. Without ice, more heat ventilates and raises Arctic air temperatures. Increased heat ventilation due to reduced sea ice can also be driven solely by changes in the prevailing wind direction that pushes more ice cover out of the Arctic to melt in the warmer Atlantic. The good news is less ice benefits the Arctic food chains. The loss of sea ice has increased photosynthesis and boosted the productivity of the Arctic Ocean food web 3-fold.
Such complex interplays of climate dynamics can result in abnormally high Arctic temperatures without a contribution from the greenhouse effect. Yet that “Arctic amplification” biases the global average temperature upwards and then incorrectly gets attributed to rising CO2. Unfortunately as Mark Twain warned long ago, “All colleges have two great functions: to confer, and to conceal, valuable knowledge”. Accordingly despite copious published science by “climate dynamicists”, many scientists protect their pet theories and promote a manufactured CO2-driven “climate crisis” while downplaying the competing importance of natural climate dynamics. I have university colleagues who teach “global warming policy” without having examined the underlying science. They just blindly trust the crisis narrative. Likewise most journalists and politicians lack the needed scientific background and simply perpetuate the narrative because both profit from promoting crises. As a result, climate science is suffering, and the dynamic control knob of climate change gets veiled from the public.
The 2021 cold snaps that caused so much misery in the central USA and Europe exemplify the power of climate dynamics. Although Dallas, Texas normally experiences 60°F in mid-February, temperatures fell by over 50°F to a low of 4°F with the day’s highest temperature only reaching 14°F. This obliterated the 1909 record low of 15°F and day’s record-low maximum temperature of 31°F. But such cold was not unprecedented. In three of the last 40 years Texas witnessed temperatures drop 50°F below normal. It should be noted, there was no compensating 50°F warming in the Arctic. Coincidentally the United Kingdom recorded -9°F, its coldest February night since 1955, while much of Germany saw temperatures fall below -4°F. The greenhouse effect can neither cause nor prevent such widespread devastating cold.
Record-breaking cold snaps contradict CO2 warming theory. As one climate scientist published, “The recent perceived prevalence of cold waves, exacerbated by heightened media attention to each event, is at odds with a rather obvious first-order hypothesis: a warming climate should lead to warm extremes getting warmer, and cold extremes getting less cold”. Accordingly in the 1990s, climate scientists who promoted global warming argued rapidly warming temperatures during the winter were evidence of a stronger greenhouse effect. But their theories failed to explain the colder weather episodes.
A different hypothesis is proving to be more robust. Instead of arguing a warming climate causes fewer cold snaps, climate dynamics flips cause and effect; fewer cold snaps will increase averaged regional temperatures. Climate scientists published, “Like many places, Canada is not warming, it is just getting less cold.” Indeed, while many maximum temperatures have decreased since the 1930s, the increase in average land temperatures has been due solely to higher minimum temperatures. Appropriately, regions with rising average temperatures have experienced fewer cold snaps. In contrast, due to the dynamics of quasi-stationary planetary waves, cold snaps remain common over other regions. In much of the southeastern USA, temperatures have failed to exhibit any warming trend in the past 70+ years, despite urban warming effects. Such regions are classified as warming holes because they fail to exhibit the warming trend predicted by rising CO2.
Heat waves and cold snaps, floods and droughts, are often a function of planetary “waveguides” that shepherd the movements of cold and warm and moist and dry air masses. If there were no continents the “ideal flow” of the polar jet would be in a relatively straight line from west to east. The polar jet stream’s strong westerly winds would more readily restrict cold air masses to the polar regions. But due to the high- and low-pressure systems generated by the contrasting temperatures between land and sea, as well as flow altering mountain barriers, the “ideal zonal flow” is disrupted. In combination with the earth’s rotation (Coriolis effect), those disruptions impart a waviness to surface winds and the jet stream. The screenshot below (from https://earth.nullschool.net/) shows the waviness of the jet stream (at 500 mb) on March 25, 2021. The sharp color change reveals the boundary of the cold air which can be thought of as the equatorward limit of the polar vortex.
Cold Arctic air moves towards the equator via the wave troughs while the wave ridges allow warm air to intrude poleward. Due to an extreme trough in February, cold Arctic air reached down through the Great Plains into southern Texas. Due to a somewhat stationary planetary “waveguide”, such a wave trough is most often located between the Rocky Mountains and the Appalachians. That pattern also enables descending cold Arctic air to collide with warm air from the Gulf of Mexico to create Tornado Alley. The same trough dynamics that brought the Texas/Oklahoma cold snaps, brings the world’s highest frequency of tornados to the same region. The focus of that trough will shift with the seasons and over decades. As a result tornado activity is decreasing throughout the southern and northwestern portions of the Great Plains and the northern Midwest but increasing throughout the Southeast and southern portion of the Midwest. Decreasing tornado activity contradicts greenhouse warming predictions but is best explained by the dynamics of natural planetary wave motion.
In contrast, when a less wavy jet stream confines the cold air to the polar region, warmer southern air moves further poleward. Due to such a dynamic, Siberia endured a heat wave from January through May of 2020. At Verkhoyansk, Russia the typical maximum January temperature reaches -44°F, rapidly rising 90°F to an average high of 50°F in May as summer sunshine increases. The heat wave caused monthly temperatures to exceed normal temperatures by 10.8°F . Nonetheless, a Siberian heatwave which raises May maximums to just 61°F shouldn’t be hyped as the “earth on fire”, and I suspect any warming in January would be greatly appreciated. Yet, with the science of climate dynamics obscured, any extreme weather event gets deflected as CO2-driven “weather weirding”, even though natural climate dynamics provide robust scientific explanations.
Both the Texas cold snap and the Siberian heatwave are the result of changes in the strength of the polar vortex. The vortex and waviness of the jet stream are largely moderated by oscillations in the quasi-permanent Aleutian Low pressure system, which also regulates changes in the western Arctic sea ice. The Aleutian Low strengthens in the winter and weakens in the summer and its winter-time strength is further moderated by El Nino/La Nina dynamics and the closely related Pacific Decadal Oscillation. Media journalists prefer to avoid explaining the complexity of those basic climate dynamics, because simplistic explanations that are dumbed down are an easier sell. Thus natural climate change remains ambiguous to most people and that’s a problem.
In the 1990s, scientists and environmental groups pushing a CO2-driven “crisis” hyped decades of the rapidly warming temperatures in Alaska as the fastest warming region on earth. Unexpectedly, Alaska suddenly flipped to become the fastest cooling region. Climate scientists observed, “During the first decade of the 21st century most of Alaska experienced a cooling shift.” Such a shift was inconsistent with the rising CO2 theory, but again easily attributed to the dynamics associated with “a change in the sign of the Pacific Decadal Oscillation (PDO, see graph below).
When the PDO is positive, the Aleutian Low strengthens, and its counter-clockwise circulation drives more warm air into Alaska and drives more warm water through the Bering Strait increasing sea ice melt. When the PDO turns negative, it weakens the Aleutian Low, reducing the warm air flow into Alaska, so Alaska cools. A weaker Aleutian Low also reduces its disruption of the jet stream which allows the vortex to strengthen. The power of the ~30-year cycles of the PDO was first recognized in 1997 as scientists noticed it coincided with changing ocean currents and changing productivity of salmon between the Gulf of Alaska and Oregon. The increasing understanding of natural PDO fluctuations has led climate scientists to argue that the “natural internally-generated changes in atmospheric circulation were the primary cause of coastal Northeast Pacific warming from 1900 to 2012”.
Pacific Decadal Oscillation index (PDO) 1900-2020 data: http://www.atmos.washington.edu/
When summer arrives in the northern hemisphere, the contrast between colder land and warmer oceans is reduced causing the Aleutian Low to weaken. The growing summer heat causes warmer lands to now contrast with cooler oceans which causes the high?pressure systems in the northern hemisphere to strengthen in the subtropical Pacific and Atlantic (Pacific or Hawaiian High and the Bermuda or Azore High). These high?pressure systems block moist ocean winds from bringing summer rains to the west coast of California and the Mediterranean regions. This dynamic causes several months of summer drought each year, making California one of the most fire prone regions globally. La Nina years extend summer droughts into the winter. Simultaneously, due to the clock?wise circulation of the Pacific high, moisture carrying winds are pushed northward causing wet summers from Oregon to Alaska.
In combination with summer high pressure systems and low-pressure regions formed by rising convection in the tropics, the “ideal zonal flow” of westerly winds is disrupted, causing various jet stream wave patterns across the mid-latitudes. When a pattern of 5 or 7 waves encircles the globe, the waves resonate in such a way they cause storms to be somewhat blocked and move slower than normal. It is slower-moving storms that generate the longer-lasting extreme weather events such floods, droughts and heat waves. As seen in the illustration above (from Kornhuber 2020) when a pattern of 5 waves forms, heat waves are 20 times more likely in specific regions (in red) of North America, eastern Europe and eastern Asia. Because a pattern of 5 circum-global waves tend to precede heat waves by 15–20 days, meteorologists have greatly increased their ability to forecast heat waves by including the state of planetary waves in their analyses. A similar resonance increases extreme weather events when patterns of 7 waves form. Fortunately, there is no evidence to suggest the earth is experiencing an increasing trend in blocking and resulting weather extremes. However, unaware that circum-global wave guides can cause similar extreme weather around the globe, some climate scientists were misled to think that such extremes (i e. widespread heatwaves) could only be caused by a global blanket of CO2-driven warming.
Still some events remain unpredictable. When the trough of a jet wave reaches its lowest point, it pinches off to form a “cut-off low” which makes the ensuing extreme weather highly unpredictable. Meteorologists nicknamed the cut-off low, the “weatherman’s woe” because cut-off lows can become stationary or flow against the general direction of the prevailing wind. Such a cut-off low formed over the Sahara Desert in the summer of 2019. The naturally heated desert air then moved northwestward, first bringing a heat wave to western Europe and then to Greenland where it caused extreme melting by raising temperatures 18°F above normal for 3 consecutive days. But yet again that Greenland melting was falsely attributed to amplification by CO2-driven global warming while the natural climate dynamics were obscured.
El Nino Cycles Drive Global Warming and Modulate Planetary Wave formation
The ocean’s heat content naturally oscillates, discharging enough heat during an El Nino to create a net loss of ocean heat, then recharging and gaining enough heat during a La Nina for a net gain of ocean heat.
However, the heat gained during a La Nina is not completely balanced by the heat discharged during an El Nino. La Nina events usually last twice as long as El Nino events. Some El Ninos don’t fully discharge the ocean’s stored heat. Heat that is not released to the atmosphere remains sequestered below the surface for years and decades, contributing to the long-term cycles of the Pacific Decadal Oscillation. According to Harvard and MIT oceanographers parts of the deep ocean is still cooling, releasing heat acquired centuries ago. Thus unbalanced El Nino/La Nina cycles will affect the long?term heating or cooling of the oceans.
First consider the impacts during a La Nina. Climate scientists all agree that “under normal conditions, and even more so with La Nina,” east to west trade winds pile up warm waters in the western tropical Pacific. By removing warm solar?heated water from the eastern Pacific, trade winds also cause cooler subsurface waters to upwell and replace the surface waters transported to the west. So during a La Nina a large temperature difference is created that further amplifies the trade winds (the Walker Circulation). Counter-intuitively the widespread upwelling of cooler water causes the average global temperature to decline while the ocean is gaining heat at greater depths.
During a La Nina the pile-up of warm waters in the western Pacific increases the largest body of warm water on earth, aka the Indo-Pacific Warm Pool. Convection increases over the warm pool and strengthens the Asian and Australian summer monsoons. Regions of rising convection also move across the Indian and Pacific Ocean alternating warmer and cooler patches of the oceans every 30 to 60 days (Madden-Julian Oscillation). Pressure from the growing Pacific warm pool pushes heated water through channels between the Indonesian Islands and increases temperatures in the Indian Ocean. Warmed Indian Ocean water can leak around the southern tip of Africa and adds heat to the Atlantic. Simultaneously, the northward flow of warm water increases along the eastern Asian coast via the Kuroshio current, as well as pushing warm water southward along the Australian west coast via the Leeuwin Current. An especially strong La Nina amplified the warm Leeuwin Current causing a marine heatwave along the western Australian coast in 2011, with severe coral bleaching and devastation to marine fisheries.
Madden Julian Oscillation
After that La Nina ended, the southward flow of warm Pacific water subsided allowing cooler southern waters to then flow equatorward. As a result the region began experiencing cold waves and a strong rebound in marine life from coral to fish. Such oscillating ocean temperatures and marine life productivity exemplifies how naturally dynamic climate change can affect biology. It also contradicts CO2 driven predictions of steadily increasing warmth and increasing extinctions.
During an El Nino, all the phenomenon associated with a La Nina weaken or reverse. The trade winds weaken and warm waters surge eastward along the equator, causing sea level to fall in the west and rise in the east by as much as 25 cm. Discharging heat warms the ocean surface causing global temperatures to spike upwards. Warm water sloshing eastward reduces the west-east temperature difference, reducing the trade winds which reduces upwelling. During an El Nino the centers of rising warm air shifts eastward. Sometimes the warm El Nino waters only reach the center of the Pacific. At other times the warm waters reach the coast of the Americas and then move poleward up their coasts. In 1998 this caused heavy rains and floods in California. In the 1800s, warm water reaching the coast brought flooding to Ecuador and washed river crocodiles down to Peru, while heavy rains turned Peruvian deserts into grasslands. These constantly changing regions of convection naturally alter atmospheric waves that encircle the earth. Extreme weather events will depend on wave interactions.
During the Little Ice Age, according to Michael Mann and others, the temperature difference between the western and eastern Pacific Ocean was in an El Nino-like condition. That does not mean the Pacific was constantly discharging heat. It means the La Nina-like or the negative Pacific Decadal Oscillation-like conditions that are associated with recharging ocean heat were largely absent. This is consistent with observations of low sunspot minimums during the Little Ice Age and solar effects on the trade winds. Although some correctly argue observed changes in energy output during sunspot cycles is too low to directly explain the earth’s warming and cooling, small solar changes are amplified by ocean dynamics. Any decrease in solar irradiance cools the equator far more than higher latitudes. This decreases the north?south temperature difference that drives the trade winds. Reduced trade winds cannot transport as much warm surface water westward into the warm pool reducing the monsoons and causing mega-droughts in southeast Asia. Slower trade winds reduced upwelling in the eastern tropical Pacific. As evidenced in sediments along the Peruvian coast, reduced upwelling clearly reduced marine productivity during the Little Ice Age. As solar irradiance increased during the 20th century, so did the El Nino/La Nina cycles. Upwelling and marine productivity increased as the earth gradually warmed, and the earth exited the climate-driven catastrophes of the Little Ice Age.
Tree ring studies similarly show PDO variability was also weak during the Little Ice Age, but strong during the Medieval Warm Period from 993 and 1300 AD. During the Medieval Warm Period, solar irradiance was higher and strong La Nina?like conditions existed. With a larger Pacific warm pool, southeast Asian mega-droughts were absent but megadroughts devastated the western United States and Canada. As sunspot activity now wanes from it peaks in the 1950s and 1990s, we are provided with a natural experiment to evaluate how the Pacific Ocean will respond to lower sunspot activity. Will the monsoons and the Pacific Decadal Oscillation weaken as they did during the Little Ice Age?
Unfortunately for now, definitively distinguishing the causes of 20th century warming between greenhouse warming versus warming from climate dynamics is currently impossible. A simple experiment done at home using just an infrared thermometer gun can demonstrate why. Heat up a large pot of water, say to 150°F. Then turn off the heat. Measure the temperature of the pot’s surface water and randomly measure 9 spots on the kitchen floor. The average temperature would compute to about 78°F. That determines the “energy state of the kitchen”. Then scoop out half the water from the pot and throw it across the floor. Then repeat the measurements. The average temperature will be significantly higher, even though there was no added heat to the state of the kitchen. The warmer average was simply due to re-distribution of heat and the way the average surface temperature was calculated. Also notice the temperature of the pot will not have changed. One might argue that the water on the kitchen floor will quickly cool and the average temperature will revert back to the original state. But in real life, solar heated ocean water becomes saltier and denser due to evaporation. The warm water then sinks below the surface where it is insulated for years.
Because we performed the experiment, we know that spreading the heat from the pot across the floor caused the average temperature to increase. However in nature we would need to precisely know the volume and degree of heat that has been redistributed across 3 dimensions. Our current technology and methods cannot precisely measure that. Scientists recently attempting to measure the discharge of ocean heat during an El Nino and reported quantities but with 25% uncertainty.
Scientists who assume recent global warming is due to rising CO2 concentrations have simply argued “there is no viable alternative explanation”. So they assume every change, warming or cooling, drought or flood, is made worse by rising CO2 concentrations. But atmospheric physicists have shown that the forcings from CO2 concentrations in the lower atmosphere are now saturated, and the increased “competition” between greenhouse molecules greatly attenuates any additional greenhouse effect imparted by rising CO2 concentrations. At higher altitudes CO2 is not saturated, but because the stratosphere warms with increasing altitude, any increasing stratospheric CO2 will enhance the export of infrared to outer space and cool the earth. To attribute any global warming to rising CO2, the warming effect of the redistribution of heat around the world must be precisely measured and factored out. How the calculation of the global average is affected by heat redistribution must be accurately ascertained. Until then, climate dynamics appear to be the better climate control knob and offer the best explanation for both a warming climate and episodes of extreme weather. And natural oscillations suggest a human caused climate crisis is highly unlikely!
Jim Steele is Director emeritus of San Francisco State University’s Sierra Nevada Field Campus, authored Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism, and a member of the CO2 Coalition
Last week the Guardian proclaimed Butterfly Numbers Plummeting in US West as Climate Crisis Takes Toll. Numerous media outlets flooded the internet with similar versions in response to the research article Fewer Butterflies Seen by Community Scientists Across the Warming and Drying Landscapes of The American West by lead author Dr. Matt Forister. Researchers found warmer summer temperatures had a positive effect statistically, while warmer autumn temperatures had a negative association. Sadly, in an age where chicken little catastrophes sell, only the negative fall temperature statistic got hyped.
Worse, the public was misled to assume “all” western butterflies were declining. For example, a University of Arizona press release (home of Forister’s co-author) stated, “Western butterfly populations are declining at an estimated rate of 1.6% per year,….The report looks at more than 450 butterfly species.” Although their database “encompassed more than 450 species”, their analyses addressed just 289 species. Only 182 exhibited declining populations. Another 107 species were stable or increasing, and 161 lacked sufficient data for analysis.
Forister et al. examined 3 independent datasets to determine the regional extent of butterfly declines. The North American Butterfly Association (NABA) supplied their once-a-year butterfly counts, typically held around July 4th, from 72 different sites. ( I’ve participated in Sierra Nevada counts) Dr. Art Shapiro’s northern California bi-weekly surveys provided a second dataset but covered only 10 sites from the San Francisco Bay area to the Sierra Nevada crest. The iNaturalist’s citizen-science dataset covers the entire west but fails to provide trustworthy trend data.
Comparing trends in the NABA & Shapiro datasets, only 104 species exhibited declines in both. In other words, only 23% of the ballyhooed 450 species showed a possible widespread decline. Despite that reality, National Geographic still trumpeted 450 Butterfly Species Rapidly Declining Due to Warmer Autumns in The Western U.S. Forister had encouraged a climate change caused decline hypothesizing, “fall warming likely induces physiological stress on active and diapausing stages, reduces host plant vigor, or extends activity periods for natural enemies.” But most species are no longer flying or laying eggs or feeding during the autumn. Most feed on springtime and early summer vegetation which is already dead or dormant by autumn. By autumn, most have sought relative safety from approaching winter to await the next flush of vegetation.
Forister et al. disturbingly downplayed known benefits of summer warming, suggesting it only increased butterfly visibility stating, “warming in the summer influences adult activity times directly and hence increases the probability of detection”. But to power their flight, butterflies sunbathe to raise their body temperature above ambient summer air temperatures. Warmth-powered flight is needed for mating and finding host plants. Summer warmth enables faster larval growth, which may enable an additional generation (i.e. Monarchs). In other species, like Edith’s checkerspot, the caterpillars seek hotter surfaces to speed growth and reach the required size to successfully overwinter. Warmer summers benefit many species in many ways.
Furthermore Forister did not remove well-known declining trends caused by insecticides and land use change. In a 2010 paper he found, “most severe reductions at the lowest elevations, where habitat destruction is greatest.” In a 2014 paper Forister concluded, “Patterns of land use contributed to declines in species richness, but the net effect of a changing climate on butterfly richness was more difficult to discern.” In his 2016 paper he modelled negative effects of neonicotinoid insecticides.
The media typically implied a climate connection to the 99% decline of Monarch butterflies, listed as Forister’s 37th most declining species. Yet the Monarch’s big killers are also land use change and herbicides, not climate change. In the 1970s, scientists discovered virtually all monarchs breeding east of the Rocky Mountains migrate to overwinter in extremely small patches of high mountain forests in central Mexico. However logging was opening the forest canopy and removing its insulating effects. In January 2002, a storm brought cold rains followed by clear skies. Without an insulating forest canopy, temperatures plummeted to 23°F (- 4°C). Millions of damp butterflies froze in place. Many millions more fell creating an eerie carpet of dead and dying butterflies several inches deep. 500 million butterflies died that winter, wiping out 80% of the entire eastern population. Similar cold events happened in 2004, 2010 and 2016. Population declines for monarchs wintering in California have paralleled the Mexican declines.
Additionally increased herbicide use severely reduced the monarch’s food plants, milkweeds. Because milkweed competed with crops, reducing harvests of wheat and sorghum by 20%, most states had declared milkweed a noxious weed. Due to the 1970s discovery of the herbicide glyphosate (i.e. Roundup) and the 1990s development of genetically modified herbicide-resistant soybean and corn crops, milkweeds dramatically declined, hindering monarch summertime recovery. To truly benefit butterflies, farmers and the public are planting butterfly friendly gardens, while climate warming provides great benefits.
Jim Steele is Director emeritus of San Francisco State University’s Sierra Nevada Field Campus, authored Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism, and a member of the CO2 Coalition