Global warming and food production

THE GREENHOUSE EFFECT

HAROLD BERNARD

HARPER COLOPON BOOKS            1980

PART I

Introduction

• Before the end of the next four decades, easily within the lifespans of many of us, the climate of the earth may be warmer than at any time in the past thousand years.
• By the middle of the next century, within the lifetimes of our children – or certainly of their children – it is possible that the earth will be warmer than at any time in the past 125,000 years.
• To say that human adjustment to these changes would be difficult is at best an understatement.
• We are part of the problem and can be part of the solution. We can have a voice in the decisions that must be made. The decisions will determine our energy future. There is no question that we must wean ourselves from fossil fuels.
• This book details the possible climatic consequences of the continued dominant position of fossil fuels in world energy production. It also discusses actions that we can take.
• If we understand the cost of losing the battle, the campaign may be carried forth more vigorously. That is the prime reason for this book. The outlook, particularly for the Midwest, is grim.

Chapter 1: The Greenhouse Threat

Increasing amounts

• The air now holds 15% more carbon dioxide than it did a hundred years ago.
• Because the world’s population is growing the demand for energy burgeons at an ever accelerating rate.
• Carbon dioxide is relatively transparent to solar radiation – sunshine – but relatively opaque to the earth’s heat radiation. This greenhouse effect warms the earth.
• Current estimates suggest that carbon dioxide-induced warming could be 11ºF within a hundred years, with temperature increases in polar regions as much as three times that.

A super-interglacial

• The earth could be plunged into a super-interglacial, with temperatures warmer than anything experienced in the last million years.
• Sea levels would rise and agricultural belts would be shifted by changing weather patterns. For some countries with marginal agriculture, the impact on food production could be severe.
• There would be winners and losers. A climate change could be the cause of a major redistribution of wealth.
• If the greenhouse effect were to last over a number of centuries, the Greenland and Antarctic ice caps would melt, and oceans would rise, flooding the world’s coastal cities.
• Global warming may amount to a climatic catastrophe in the 21^st century. Everybody agrees that the potential for a serious problem is there.

A cooling cycle

• Natural cycles of warming and cooling still dominate our weather and climate. Every 180 years a significant drop in atmospheric temperature takes place and persists for several decades.
• There are cycles superimposed upon cycles superimposed upon cycles, and the cooling is never uniform. The 180-year cycle seems to be the dominant one.
• The bottom of the last cycle was in the early 1800s, which suggests the 1980s will once again bring peak coldness. The rugged winters of 1976-77, 1977-78, and 1978-79, each of which was one of the coldest on record in some parts of the United States, were probably the advance guard of the types of winters we will experience more frequently in the 1980s.
• A natural cooling trend will likely mask the initial effects of any human-induced warming. The greenhouse effect is possibly preventing temperatures from dropping as low as they might.
• Before the end of the century, a natural warming trend is projected on the 180-year cycle curve, while at the same time the carbon dioxide effect really takes off.
• Shortly after the year 2000 we could be in for a very rude climatic shock, as hemispheric temperatures soar past anything we have experienced in the past several hundred years.

The impact on our lives

• By mid-century our climate may be warmer than at any point in the last 125,000 years. The change could come about in a very short period. Humankind would have an immense difficulty in adjusting to it.
• Following chapters examine in detail, mainly for the United States, the changes in weather patterns likely to result from a warming climate.
• Global wind circulation patterns change and weather regimes over particular regions are completely recast. Some spots turn cooler; others become drier; some wetter; and many warmer.
• Most of the chapters deal with specific climatic changes many of us may live to experience. Chapter 12 presents, in more general terms, a scenario of global climatic transitions that are possible over the next 100 years or so.
• Agriculture, especially, is highly sensitive to climatic change, and the greenhouse threat holds frightening possibilities for our Midwestern breadbasket.
• The final chapters suggest ways out of the dilemma, although it is now doubtful that we can completely escape the consequences of what we have started.
• The development of solar energy must receive the highest priority. Energy conservation must become a way of life.
• Muddling through is not an effective way to deal with cumulative environmental problems as policy making grows out of crisis management. The greenhouse threat must be met head-on. And it must be met now.

Chapter 2: We Can’t Put the Weather in a Test Tube

• Continuous measurements of airborne carbon dioxide were begun in the late 1950s at the observatory on the dormant Hawaiian volcano, Mauna Loa. We know for certain that atmospheric carbon dioxide concentrations have been steadily growing for the past twenty years.

Historical trends

• Carbon dioxide concentrations have been growing since 1860 when the industrial revolution began; the use of fossil fuels, coal in particular, started to accelerate.
• The pre-industrial concentration of carbon dioxide was somewhere between 285 and 305 parts per million (ppm). In 1958 concentrations were 311 or 312. Current estimates put the concentration close to 335 ppm and by the year 2000 the value will be in the range 380-400 ppm.
• The Mauna Loa record is essentially duplicated by other measurements taken at the South Pole, American Samoa, and Barrow, Alaska, and by readings gathered by Sweden and Australia.
• The first 10% increase in carbon dioxide took place over about 110 years, the next 10% will take 20 years and the next 10% beyond that only ten years.
• Superimposed on the steady upward trend of the carbon dioxide concentrations there is a seasonal oscillation each year of about 5 or 6 ppm because plants and trees use carbon dioxide in the photosynthesis process when vegetation is actively growing. In winter, when many plants are dormant, less carbon dioxide is used, and more of it remains in the atmosphere.
• The clearing of forests and the decay of humus may add as much carbon dioxide to the atmosphere annually as the burning of fossil fuels.

Future trends

• The net effect of increasing amounts of carbon dioxide is to warm the atmosphere near the earth’s surface. As the amount of carbon dioxide rises, so does the temperature of the earth’s lower atmosphere.
• In 1967 we were warned of a global temperature increase of 4ºF if atmospheric carbon dioxide were allowed to double. Estimates say this will happen between 2020 and 2050.

Nervous breakdowns and other problems

• Climate models are relatively primitive. Scientists cannot hope to represent all of the intricacies and nuances of real atmospheric processes. Today’s largest computer would have a nervous breakdown trying to deal with the complexity of such a model.
• Assumptions may or may not be right. The projected numbers that are plugged into the models may or may not be right.
• Even the most complex computer models have serious shortcomings. One of the greatest weaknesses is that types and amounts of clouds are not computed. A second major deficiency is that interactions between the atmosphere and oceans are not represented.
• Oceans store and transport large quantities of heat and thus exert significant long-term effects on weather and climate.
• The consensus is that a doubling of the atmospheric carbon dioxide content will lead to warming of 3.6ºF to 5.4ºF, with significantly larger warming – perhaps as much as 18ºF – in the world’s polar regions.
• In polar regions the air is cold and cannot hold much water vapor, allowing greater heat absorption and warming. Once ice and snow disappear, warming accelerates.
• The process becomes self-enhancing: more warming leads to more ice melting, which leads to more solar radiation being absorbed, which leads to more warming.

Feedback

• There is the problem of positive and negative feedback; the answers the models are giving might be wrong. If there is a significant error in the model forecasts, that error could be in the direction of under-predicting or over-predicting the amount of potential warming.
• The personal opinion of people working in the area is that refinement of the models and consideration of all possible feedbacks will probably force us to draw a bleaker picture.

How much proof?

• Since the consequences of a climate change at the higher end of the current warming estimate could be both enormous and irreversible, perhaps society would be best to err conservatively in planning future fossil fuel consumption patterns.
• Many of the following chapters in this book explore what the enormous and irreversible climatic effects might be, beginning with changes many of us may live to experience. We should know what we are facing.

Chapter 3: A Search for a Climatic Analog

Chapter 4: The Return of the Dust Bowl

Droughts and sunspots

• On a broad time scale the occurrence of major droughts in the United States west of the Mississippi River appear to follow a fairly regular cycle of twenty to twenty-two years, and to match up very closely with the double sunspot cycle, two eleven-year cycles.
• The next major drought in the West will occur around the year 2000. But it is not with that drought that this book is concerned. It is the one likely to strike around 2020, near the end of the first decade of significant carbon dioxide caused climatic warming.

Black blizzards

• The greatest disaster in American history attributable to metorological factors was the superdrought of the 1930s, which dried up 50 million acres of the Great Plains.
• Before the plains were settled in the late 1800s, natural, deeprooted grasses could survive even prolonged droughts. But after 1885 the grasses were either plowed under to raise wheat and corn, or were overgrazed by range cattle.
• The Midwestern topsoil was bared to the mercy of the elements, and the relentless winds that accompanied the 1930s drought removed 350 million tons of the richest soil in the world.
• The first of a series of awesome dust storms, or ‘black blizzards,’ struck in November 1933. Great dust storms continued to ravage the Midwest until 1939.
• In the heart of the dust bow, livestock died of suffocation and starvation; what crops survived were withered and stunted. Huge drifts of loose soil surrounded farms and blocked highways and railroads. The blowing dust sandblasted paint off houses and automobiles.
• Hundreds of people died of respiratory ailments, and thousands fled the area, simply abandoning their ranches to the wind and dust. The black blizzards left profound physiological and psychological impacts on a generation of Midwesterners.

Snapshots

• Figure 4.2 is a ‘snapshot’ of the 1930s drought at its peak in July 1934. The drought of the 1950s was shorter, more confined, and centered a bit further south than its 1930s predecessor.
• The 1970s drought spared much of the Midwest, but dried up reservoirs and snowpacks in the Far West and Rocky Mountain states, and hit hard at Minnesota and Wisconsin.
• Figure 4.4 is a snapshot of the drought in April 1977, as the western United States came out of a virtually snowless winter. Very intense drought also gripped northwest Wisconsin.
• Steinbeck’s vivid scenes may exist only in books both now and in the future, for modern soil conservation practices should preclude the return of the great, dark storms of the 1930s. But the specter of severe drought still hovers over the western United States, and the greenhouse threat may well be converted into dust bowl reality if the warmth and atmospheric circulation patterns of the 1930s return early next century. The implications for agriculture and water supply are serious.

Eight-five bushels per acre

• Corn accounts for almost 53% of the total U.S. grain production. It is a crop highly dependent upon July precipitation and temperature. Typically, the highest per acre yields come in cooler-than-normal summers.
• During the period 1930-1939, July temperatures in the corn belt states of Iowa, Missouri, Illinois, Indiana, and Ohio averaged from 2 to 4ºF or more above modern means. July precipitation averaged just 50% to 85% of current normals. The hottest and driest weather blistered Iowa and Missouri, and corn crops withered and died.
• Since the 1930s agricultural technology has made immense strides and crop yields have steadily increased. But even modern technology may not be able to overcome the deleterious effects of severe drought.
• Simulated corn yields using 1973 technology and harvested acreage show contemporary yields averaging around 105 bushels per acre while during the worst years of the 1930s dust bowl, yields would have dropped to around 85 bushels per acre, a reduction of about 20%.
• Despite modern fertilizers and pesticides, farm mechanization, and strains of grain that are relatively drought and pest resistant, an intense drought would still have a huge impact on Midwestern corn production.