Wednesday, May 29, 2019

Cycles of Rapid Climate Warming

Published in the Pacifca Tribune May 28, 2019

What’s Natural

Cycles of Rapid Climate Warming

The globally averaged temperature rose 1.5°F from 1880 to today. Various narratives suggest the rise since 1950 was driven by increasing concentrations of CO2. The rising temperature before 1950 was considered natural. Since 1990, Arctic temperatures rose 2 to 3 times faster than the global average. So, are rapidly rising Arctic temperatures evidence of an impending climate crisis? 

Astute students of climate history recall rapid Arctic warming has happened often and naturally. During the last Ice Age when COconcentrations were just half of today’s, 25 abrupt warming eventshappened. Arctic temperatures rose 9°F, and sometimes as much as 14°F in just 40 years. These rapid warming episodes are now called Dansgaard–Oeschgerevents (D-O events) in honor of the researchers who first detected them in Greenland’s ice cores. These D-O episodes affected global climate, changed ocean currents along California’s coast and altered the range of European forests.

What caused such abrupt warming? Basic physics dismisses changes in greenhouse gases or solar insolation because neither radiative effect induces such rapid warming. The most reasonable explanation suggests episodes of ventilating heat, that had accumulated in the Arctic Ocean, rapidly warmed the air. 

The notion of stored heat in a freezing Arctic Ocean seems unfathomable to many laypeople. But it is scientifically well documented.Tropical Atlantic waters experience intense heating and evaporation. This results in warm salty water that is relatively dense. The Gulf Stream and its branching currents then transport that warm water northward. Because the water is salty and dense it sinks below colder and fresher surface waters as it approaches the Arctic Ocean. As a result, there is a layer of warm Atlantic water stored at depths between 300 and 2,700 feet below the Arctic Ocean’s surface.Arctic researchers report, “the total quantity of heat is substantial, enough to melt the Arctic sea ice cover several times over.”

Warm Atlantic Water in the Arctic Ocean

Sea ice and a layer of cold fresh water normally inhibit subsurface heat from ventilating to the atmosphere. But as the incoming heat increases and accumulates, the warm Atlantic Waters can eventually melt the overlying ice cover. Other times, changes in the direction of Arctic winds will blow sea ice out into the Atlantic, as it did in the late 1990s. Either way, without insulating ice, a burst of heat ventilates from the ocean and warms the atmosphere. 

Recently, anthropologists studying past Arctic cultures found the pre-Dorsett culture periodically abandoned then recolonized the Arctic coast as changes in sea ice affected temperatures. When sea ice covered coastal waters for 2 months longer than today, temperatures became 3-7°F cooler. Arctic people then abandoned the coast and moved south. A few hundred years later they re-colonized the coast when periods of open water, lasting 4 months longer than today, allowed heat to ventilate and raise temperatures 10°F warmer than today.  Such changes alternated over several hundred years. And that raises the question, is the Arctic still experiencing similar cyclical warming?

Over the past several hundred years, melting Arctic sea ice corresponds with observed periods of increased intrusions of warm Atlantic waters. The dramatic Arctic warming during the 1920s and 1930s corresponded with increased intrusions of warm water accompanied by Atlantic fish species normally found further south. As the 1922 newspaper clipping reveals (see above), the warming of the Arctic was so dramatic it raised concerns the frigid Arctic would soon be converted to a warmer “temperate zone”. 

Arctic 1922

When warm water inflows began retreating around 1950 so did the Atlantic fish. Sea ice then increased.  Such cycles have been recorded infishery data for hundreds of years. The most recent cycle of melting Arctic sea ice likewise coincided with intruding warm Atlantic waters with patterns of invading fish very similar to the 1920s-1930s warming episode.

So, we are now in the midst of an instructive natural experiment. If the loss of Arctic sea ice and warmer temperatures are due to rising CO2concentrations, we should soon see a total loss of Arctic sea ice as predicted by some climate scientists. In contrast, if natural oscillations are controlling intrusions of warm Atlantic waters, Arctic sea ice will soon rebound. Indeed, a recent shift in ocean oscillations is now decreasing warm water intrusions. Temperatures should fall as less heat ventilates into the atmosphere. Based on earlier 20thcentury patterns when lost sea ice rebounded in the 1960s and 70s, Arctic sea ice should begin rebounding by the year 2030. But then again, warmer temperatures did last for 300 years during cycles a few thousand years ago. Either way, natural climate cycles predict Arctic temperatures will not experience further accelerated warming. We will soon see which theory is most accurate within the coming decade.

Jim Steele is retired director of the Sierra Nevada Field Campus, SFSU

Saturday, May 25, 2019

The $1000 Student Climate Challenge Award

Is there a climate crisis??  

 Currently children are being asked to lead a political charge for “climate change action”. Climate is very complex, and most adults have a very poor understanding of all the factors affecting climate change.  Thus, many people believe our children must have a far inferior understanding of climate change and are just being used as pawns in the politics of climate change. Many adults see student strikes as silly political theater, not validation of any climate theory or proof of an impending climate crisis.

But perhaps I underestimate the knowledge and intelligence of our student “climate strikers”. So, I am offering a $1000 award to the student who unequivocally outlines why 1) rising concentrations of CO2 are the cause of recent climate change, and 2) why that change is catastrophic. 

I warn participants, I devoted my whole professional career towards scientific research and education that promotes wise environmental stewardship. Nonetheless I became a climate skeptic. I observed too many people eager to blame climate change for environmental problems that were caused by other factors and had real remedies. So, I suspect no adult, never mind a child, can meaningfully determine that recent weather or recent changes in a species abundance have been driven by rising greenhouse gases. 

But you may prove me wrong. 

Furthermore, to encourage good scientific thinking, if there is no winner in this climate challenge, I will still guarantee a $500 “runner-up” prize to the student who demonstrates the best scientific thinking, even if their conclusions are wrong.

Here are the requirements:

1.    The student must be 21 years or younger. Nonetheless I encourage each student to discuss climate change with your parents, teachers and friends as well as contacting scientists.

2.    The student must email their arguments in a document that is no larger than 5000 words. They must state their name and age and type “The $1000 Student Climate Challenge Award” in the subject line. Email the document by December 1, 2019 to

3.    The student must use the foundation of scientific inquiry, the “null hypothesis.   In other words, the student must show that current weather/climate reflects a change that exceeds natural climate change. That requires choosing the appropriate time frames for discussion.

4.    Students must go beyond simple correlations. Correlation is notcausation. Although CO2 concentrations are higher today than they were 200 years ago, higher concentrations are not evidence of causation. 

5.     Students must address relevant alternative hypothesesFor example, why is Arctic warming the result of CO2 warming and not the result of natural oscillations that drive warmer waters into the Arctic?

6.    Students must address why warming is catastrophic. If warming is caused by rising CO2, why would a longer growing season be catastrophic? Or if there is less sea ice why would the resulting increase in photosynthesis be catastrophic? Or what is the evidence of a trend in larger or more tornados?

7.    Consensus is not evidence.  Consensus is merely political theater. Arguments must be based on evidence. Politically motivated scientists tried to refute Albert Einstein’s theory of relativity using a “consensus” argument and writing “100 Authors Against Einstein”. The consensus was still wrong.

8.    Avoid arguments from authority. As Carl Sagan wisely advised “arguments from authority carry little weight  - authorities have made mistakes in the past.” For example, John Muir’s ideas were published in popular papers and magazines regards the formation of Yosemite Valley by glaciers. The geological authority from Harvard, Josiah Whitney, suggested otherwise and tried to smear Muir as just an “ignorant shepherd”. But Muir was mostly correct! Likewise, I warn that using the word “denier” will not make your arguments more correct.

9.    Students can enter as many times as they want. You may want to change your arguments when new information comes to light. Simply note that your new entry replaces your last.

As student essays roll in, I will periodically report in my What’s Naturalnewspaper column, and on my blog, regards failed common arguments and why it will disqualify your essay from the award.  That will allow every student to improve their argument and re-submit.

I wish every student the best and hope their sincere essays will promote better scientific discourse and understanding.

Sincerely Jim Steele

Director emeritus, Sierra Nevada Field Campus, San Francisco State University

Wednesday, May 15, 2019

Our Urban “Climate Crisis”

Published in Pacifica Tribune  May 14, 2019

What’s Natural 
Our Urban “Climate Crisis”

Based on a globally averaged statistic, some scientists and several politicians claim we are facing a climate crisis. Although it’s wise to think globally, organisms are never affected by global averages. Never! Organisms only respond to local conditions. Always! Given that weather stations around the globe only record local conditions, it is important to understand over one third of the USA weather stations report a cooling trend.  Cooling trends have various local and regional causes, but clearly, areas with cooling trends are not facing a “warming climate crisis”. Unfortunately, by averaging cooling and warming trends, the local factors affecting varied trends have been obscured. 
It is well known as human populations grow, landscapes lose increasing amounts of natural vegetation, experience a loss of soil moisture and are increasingly covered by heat absorbing pavement and structures. All those factors raise temperatures so that a city’s downtown area can be 10°F higher than nearby rural areas. Despite urban areas representing less than 3% of the USA’s land surface, 82% of our weather stations are located in urbanized areas. This prompts critical thinkers to ask, “have warmer urbanized landscapes biased the globally averaged temperature?”  (Arctic warming also biases the global average, but that dynamic must await a future article.)
from Wickham 2013
Satellite data reveal that in forested areas the maximum surface temperatures are 36°F cooler than in grassy areas, and grassy areas’ maximum surface temperatures can be 36°F cooler than the unvegetated surfaces of deserts and cities. To appreciate the warming effects of altered landscapes, walk barefoot across a cool grassy lawn on a warm sunny day and then step onto a burning asphalt roadway.
In natural areas like Yosemite National Park, maximum air temperatures are cooler now than during the 1930s. In less densely populated and more heavily forested California, maximum air temperatures across the northern two thirds of the state have not exceeded temperatures of the 1930s. In contrast, recently urbanized communities in China report rapid warming of 3°F to 9°F in just 10 years, associated with the loss of vegetation.

Although altered urban landscapes undeniably raise local temperatures, some climate researchers suggest warmer urban temperatures do not bias the globally averaged warming trend. They argue warming trends in rural areas are similar to urbanized areas. So, they theorize a warmer global temperature is simply the result of a stronger greenhouse effect. However, such studies failed to analyze how changes in vegetation and wetness can similarly raise temperatures in both rural and urban areas. For example, researchers reported overgrazing had raised grassland temperatures 7°F higher compared to grassland that had not been grazed. Heat from asphalt will increase temperatures at rural weather stations just as readily as urban stations.
To truly determine the effects of climate change on natural habitats requires observing trends from tree ring data obtained from mostly pristine landscapes.  Instrumental data are overwhelmingly measured in disturbed urbanized areas. Thus, the difference between instrumental and tree ring temperature trends can illustrate to what degree landscapes changes have biased natural temperature trends.  And those trends are strikingly different!
The latest reconstructions of summer temperature trends from the best tree ring data suggest the warmest 30-year period happened between 1927 and 1956. After 1956, tree rings recorded a period of cooling that lowered global temperatures by over 1°F. In contrast, although tree rings and instrumental temperatures agreed up to 1950, the instrumental temperature trend, as presented in NASA graphs, suggests a temperature plateau from 1950 to 1970 and little or no cooling. So, are these contrasting trends the result of an increased urban warming effect offsetting natural cooling?

from Schneider 2015

After decades of cooling, tree ring data recorded a global warming trend but with temperatures just now reaching a warmth that approaches the 1930s and 40s. In contrast, instrumental data suggests global temperatures have risen by more than 1°F above the 1940s. Some suggest tree rings have suddenly become insensitive to recent warmth? But the different warming trends are again better explained by a growing loss of vegetation and increasing areas covered by asphalt affecting temperatures measured by thermometers compared with temperatures determined from tree ring data in natural habitats.
Humans are increasingly inhabiting urban environments with 66% of humans   projected to inhabit urban areas by 2030. High population densities typically reduce cooling vegetation, reduce wetlands and soil moisture, and increase landscape areas covered by heat retaining pavements. Thus, we should expect trends biased from urbanized landscapes to continue to rise. But there is a real solution to this “urban climate crisis.” It requires increasing vegetation, creating more parks and greenbelts, restoring wetlands and streams, and reducing heat absorbing pavements and roofs. Reducing CO2concentrations will not reduce stifling urban temperatures. 

Jim Steele is the retired director of San Francisco State University’s Sierra Nevada Field Campus and authored Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism

Wednesday, May 1, 2019

Polar Bear Narratives

Published May 1, 2019 Pacifica Tribune

What's Natural 

Polar Bears: Which Narrative to Believe?

When polar bear expert Mitch Taylor modeled populations in the Baffin Bay region (west of Greenland) in the 1980s, he estimated between 300 and 600 bears. Inuit hunters protested his estimates were far too low, and Baffin Bay’s hunting quotas far too small. So, Taylor and Inuit hunters sat together in “kappiananngittuq” to discuss their disagreements. The Inuit pointed out he surveyed during a time and in a place that overlooked a large portion of the population. Naturally, models driven by poor data always fail to model reality.

To Taylor’s credit, he redesigned his surveys based on hunters’ recommendations. The new survey tripled population estimates to over 2000 bears. Although a trend in the bear population could not be determined, it has been universally agreed that since the 1974 International Agreement for the Conservation of Polar Bears, polar bear populations were increasing due to better hunting regulations.

Of the 5 polar bear populations deemed to be declining by Canadian researchers, three declines were due to over hunting. Only two declines, such as western Hudson Bay, were possibly driven by global warming. Models suggested bears of western Hudson Bay were declining because warming was reducing sea ice. In 2013, extremist researchers like Andrew Derocher proclaimed, "All indications are that this population could collapse in the space of a year or two if conditions got bad enough," and the media echoed ‘bears were on the verge of collapse’. Instead, that bear population has now increased.  It is interesting to note the Hudson Bay is totally ice free every summer. So, does less summer sea ice truly hurt polar bears?

The claim that less sea ice will cause polar bears to go extinct is just one narrative, not tested science. From a historical perspective, Derocher’s claim that two-thirds of all polar bears could go extinct by 2030 is laughable. Numerous researchers have reported Arctic temperatures averaged about 3 degrees higherthan today between 10,000 and 6,000 years ago and sea ice extentwas far less for thousands of years. Clearly, polar bears did not go extinct, and history does not support Derocher’s narrative.

Most importantly, Arctic studies show less sea ice promotes more photosynthesis. After sea ice had recently decreased by 9%, Stanford scientists determined productivity increased by 30%. More photosynthesis provides more food for fish. More fish feed more seals and fatter seals feed more polar bears. 

Conversely, there is solid evidence that thick ice is detrimental to seals and bears. Despite plenty of sea ice to hunt from, each winter all polar bears lose weight. Polar bears’ main prey is ringed seals, but bears have a very low success rate when hunting seals at their breathing holes. Polar bears feed most successfully from March to May when ringed seals birth their pups on the ice. Feasting on seal pups, bears can quickly quadruple their weight. After giving birth and molting, ringed seals leave the ice and migrate to the open ocean to feed and become quite inaccessible to bears for the summer. Recent reductions in sea ice from July to September are irrelevant for bears’ summer hunting success. But open waters do benefit seals and fish.

To remain in the Arctic all winter ringed seals must create several breathing holes. When new thin ice first forms, they bust out several breathing holes using their heads. As winter proceeds they gnaw and claw to keep their holes open. Wherever sea ice survives for several years it becomes too thick to create breathing holes. So, across the Arctic, regions of thick ice contain the fewest seals and fewest bears. In contrast, in the Hudson Bay where new ice must form each year seals and bears are abundant!

Researchers report cycles of thick spring-time ice stress ringed seals. Natural cycles change wind directions, trapping ice against various coasts. As layers of ice raft over each other, the new ice thickens. Thicker ice delays seals from reaching open water for summer feeding, resulting in weight loss. Low weights cause seals to forego breeding the next year thus reducing the bears’ food supply.

Because local ice conditions frequently change, polar bears do not defend territories. Instead bears are flexible and move great distances seeking out regions with more seals. One radio-collared bear was tracked moving from Alaska to Greenland during a summer.

When winds shift, thick sea ice can be blown out into the relatively warm Atlantic. This allows new ice to form which then can support more seals and more bears. Based on this basic biology, the Inuits’ narrative, “It is the time of the most polar bears” is best supported by scientific evidence.

Jim Steele is the retired director of San Francisco State University’s Sierra Nevada Field Campus and authored Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism

Thursday, April 18, 2019

Native American Wisdom: Polar Bears and Bowhead whales

published Pacifica Tribune April 17, 2019
 What's Natural column

Inuit Superior Calculations of Wildlife 

Native American Wisdom and Kappiananngittuq: Part 1
In 2010 Nunavut’s Minister of Environment Daniel Shewchuk wrote, “Inuit hunters have a close relationship with the land and wildlife. They have observed that the overall population of polar bears in Nunavut is not declining as some suggest, but rather is thriving. No known environmental or other factors are currently posing a significant or immediate threat to polar bears overall. Furthermore, Inuit knowledge and science corroborate that the species can and will adapt to changing and severe climatic conditions, as it has done for centuries.”

The Inuit truly practice the concept of “it takes a village”. Hunters sit down in kappiananngittuq and respectfully share their observations of wildlife and their movements. Kappiananngittuq is the Inuit word for a “safe place to discuss”. Based on community discussions, Inuit have steadfastly claimed it is “The Time of the Most Polar Bears”. Overhunting has been one of the world’s greatest threats to wildlife. And the growing number of polar bears is testimony to wise hunting regulations now honored by the Inuit.

In contrast, based on questionable computer models, some western scientists have argued two-thirds of all polar bears will be extinct by the year 2030. Climate scientists like Gavin Schmidt sitting in his New York office, suggested the Inuit are in total denial. Sadly, in climate politics there is no kappiananngittuq where people safely discuss divergent knowledge. If you dare disagree with models of gloom and doom, you are attacked as an ignorant denier.

Fat Polar Bear

In part 2, I will present abundant scientific evidence supporting Inuit claims that it is the “time of the most polar bears”. But first I present an example of the Inuit’s amazing ability to correctly diagnose changes in Arctic wildlife populations. Kappiananngittuq discussions consistently resulted in accurate conclusions, far superior to western science.

Due to overharvesting during the early 20th century, Bowhead whales were undeniably on the brink of extinction. In response, commercial hunting of Bowheads along the Canadian Arctic was wisely banned in 1951. Inuit subsistence hunting continued until 1979 but was later prohibited. After extensive debate, a limited licensed subsistence hunt was eventually renewed in Nunavut in 1996.
When the Inuit first petitioned to hunt the Bowhead in the 1980s, scientists argued the Bowhead population had not yet recovered to the sustainable numbers needed to safely permit subsistence hunting. The Inuit insisted scientists grossly underrepresented the whale’s abundance due to faulty surveys. It is not exactly clear how the Inuit counted, but by compiling their community’s observations, they concluded there were three times more Bowhead than scientific models suggested.

Many non-Inuit were suspicious, insinuating Inuit estimates were a self-serving calculation driven by their desire to hunt more whales. Off-hand comments portrayed Inuit estimates as mere hunches lacking written documentation and verifiable observations. Inuit science was not considered on par with hi-tech calculations.

But scientific surveys frequently suffer from a wide range of biases and inaccuracies. Models are often just the best guesses of a small group of scientists that get translated into numbers and equations. The data that feed their models are often limited by scant observations.

In the 1970s, during the Bowhead’s spring migration, scientists perched on hilltops, or pressure ridges in the ice. They counted whales as they migrated north through the open-water “leads” along the north coast of Alaska. They erroneously assumed that when the winds changed and ice temporarily closed those leads, whales stopped migrating. Only after the winds again shifted and the leads reopened, did scientists continue their count. Based on such survey assumptions, scientists modeled that only 2000-3000 Bowhead whales existed. And such small numbers meant the whales were still endangered.

In contrast Inuit hunters had always ventured much further out on the ice. Based on experience, they argued that when open-water leads closed, the whale migration still continued. The swirling pack ice always generated chaotic but sufficient springtime cracks and leads, providing whales enough opportunities to breathe. Bowheads also break relatively thin ice to make their own breathing holes. Whales were never restricted to large open-water leads along the coast. Thus, Inuit hunters argued the scientists had been blind to the majority of migrating whales. To their credit, western scientists re-designed their surveys to address the Inuit’s criticisms. The Inuit were proven correct, and amazingly had correctly calculated that Bowhead populations were 3 times higher than scientists had estimated. I suggest we all could benefit by debating kappiananngittuq style.

Bowhead Whale creating breathing hole

Tuesday, April 16, 2019

Victory for Intellectual Freedom

A Victory for Intellectual Freedom!

Dr. Peter Ridd who studies the effects of sediments in the Great Barrier Reef was fired for challenging University reports asserting the Great Barrier Reef was dying. To silence his skepticism the university fired him claiming he violated the code of collegiality. Alarmists around the internet supported the university's attempt to silence a skeptic. 

However the judge ruled the University had acted unlawfully stating, "Incredibly, the University has not understood the whole concept of intellectual freedom. In the search for truth, it is an unfortunate consequence that some people may feel denigrated, offended, hurt or upset. It may not always be possible to act collegiately when diametrically opposed views clash in the search for truth." (p. 71)

The entire ruling can be read here:

The list of rulings start on  p. 74

Tuesday, April 2, 2019

The Little Ice Age - Back to the Future

published in the Pacifica Tribune's biweekly column What’s Natural?

April 3, 2019

Little Ice Age glaciers threaten villages and farms

The Little Ice Age - Back to the Future 

Extreme scientists and politicians warn we will suffer catastrophic climate change if the earth’s average temperature rises 2.7°F above the Little Ice Age average. They claim we are in a climate crisis because average temperature has already warmed by 1.5°F since 1850 AD. Guided by climate fear, politicians fund whacky engineering schemes to shade the earth with mirrors or aerosols to lower temperatures. But the cooler Little Ice Age endured a much more disastrous climate.

The Little Ice Age coincides with the pre-industrial period. The Little Ice Age spanned a period from 1300 AD to 1850 AD, but the exact timing varies. It was a time of great droughts, retreating tree lines, and agricultural failures leading to massive global famines and rampant epidemics. Meanwhile advancing glaciers demolished European villages and farms and extensive sea ice blocked harbors and prevented trade. 

Dr. Michael Mann who preaches dire predictions wrought by global warming described the Little Ice Age as a period of widespread “famine, disease, and increased child mortality in Europe during the 17th–19th century, probably related, at least in part, to colder temperatures and altered weather conditions.” In contrast to current models suggesting global warming will cause wild weather swings,Mann concluded “the Little Ice Age may have been more significant in terms of increased variability of the climate”.  Indeed, historical documents from the Little Ice Age describe wild climate swings with extremely cold winters followed by very warm summers, and cold wet years followed by cold dry years.

A series of Little Ice Age droughts lasting several decades devastated Asia between the mid 1300s and 1400s. Resulting famines caused significant societal upheaval within India, China, Sri Lanka, and Cambodia. Bad weather resulted in the Great Famine of 1315-1317 which decimated Europe causing extreme levels of crime, disease, mass death, cannibalism and infanticide.The North American tree-ring data reveal megadroughts lasting several decades during the cool 1500s. The Victorian Great Drought from 1876 to 1878 brought great suffering across much of the tropics with India devastated the most. More than 30 million people are thought to have died at this time from famine worldwide. 

The Little Ice Age droughts and famines forced great societal upheaval, and the resulting climate change refugees were forced to seek better lands. But those movements also spread horrendous epidemics. Wild climate swings brought cold and dry weather to central Asia.  That forced the Mongols to search for better grazing. As they invaded new territories they spread the Bubonic plague which had devastated parts of Asia earlier. In the 1300s the Mongols passed the plague to Italian merchant ships who then brought it to Europe where it quickly killed one third of Europe’s population. European explorers looking for new trade routes brought smallpox to the Americas, causing small native tribes to go extinct and decimating 25% to 50% of larger tribes. Introduced diseases rapidly reduced Mexico’s population from 30 million to 3 million.

By the 1700s a new killer began to dominate – accidental hypothermia. When indoor temperatures fall below 48°F for prolonged periods, the human body struggles to keep warm, setting off a series of reactions that causes stress and can result in heart attacks. As recently as the 1960s in Great Britain, 20,000 elderly and malnourished people who lacked central heating died from accidental hypothermia. As people with poor heating faced bouts of extreme cold in the 1700s, accidental hypothermia was rampant. 

What caused the tragic climate changes of the Little Ice Age? Some scientists suggest lower solar output associated with periods of fewer sunspots. Increasing solar output then reversed the cooling and warmed the 20thcentury world.  As solar output is now falling to the lows of the Little Ice Age, a natural experiment is now in progress testing that solar theory. However other scientists suggest it was rising COthat delivered the world from the Little Ice Age. 

Increasing COalso has a beneficial fertilization effect that is greening the earth. The 20th century warming, whether natural or driven by rising COconcentrations, has lengthened the growing season. Famines are being eliminated. Tree-lines stopped retreating and trees are now reclaiming territory lost over the past 500 years. So why is it that now we face a climate crisis?

At the end of the 1300’s Great Famine and the Bubonic Plague epidemic, the earth sustained 350 million people. With today’s advances in technology and milder growing conditions, record high crop yields are now feeding a human population that has ballooned to over 7.6 billion.

So, the notion that cooler times represent the “good old days” and we are now in a warmer climate crisis seems truly absurd. 

Jim Steele is retired director of the Sierra Nevada Field Campus, SFSU